Agulhas Plateau Cretaceous Climate: drilling the Agulhas Plateau and Transkei Basin to reconstruct the Cretaceous–Paleogene tectonic and climatic evolution of the Southern Ocean basin

Citation for published version: Uenzelmann-Neben, G, Bohaty, SM, Childress, LB & the Expedition 392 Scientists 2022, 'Agulhas Plateau Cretaceous Climate: drilling the Agulhas Plateau and Transkei Basin to reconstruct the Cretaceous–Paleogene tectonic and climatic evolution of the Southern Ocean basin', International Ocean Discovery Program: Preliminary Reports, vol. 392. https://doi.org/10.14379/iodp.pr.392.2022


Introduction
The warmest sustained greenhouse episode of the past ~150 My occurred during the mid-Cretaceous between ~95 and 80 Ma (e.g., Clarke and Jenkyns, 1999;Friedrich et al., 2012;Huber et al., 2018Huber et al., , 2002. Proxy data and climate models suggest CO 2 levels during this supergreenhouse interval may have been as high as 3500 parts per million by volume (ppmv) before declining to less than 560 ppmv following the Eocene-Oligocene transition (EOT) at ~34 Ma (Berner et al., 1983;Bice et al., 2006;DeConto and Pollard, 2003;Royer et al., 2004). High-latitude temperatures were exceptionally warm during the prolonged period of elevated CO 2 levels in the mid-Cretaceous, resulting in low meridional temperature gradients (Bice et al., 2006(Bice et al., , 2003Forster et al., 2007;Huber et al., 1995). However, Cretaceous warmth was also interrupted by periods of rapid global climate change during oceanic anoxic events (OAEs), which were associated with widespread reduction in basin ventilation and major changes in ocean temperature and circulation (Arthur et al., 1985(Arthur et al., , 1987Jenkyns, 2003Jenkyns, , 2010Schlanger and Jenkyns, 1976;Sinninghe Damsté et al., 2010). The timing, magnitude, and oceanographic and ecological consequences of the Cretaceous greenhouse warming are poorly documented in the southern high latitudes. Furthermore, greenhouse climate conditions with CO 2 levels approaching those of the Cretaceous-Paleogene interval are envisioned for the near future (e.g., Hay, 2011), highlighting the value of using Cretaceous-Paleogene records to better understand the operation of the Earth system in greenhouse periods.
Expedition 392 drill sites on the Agulhas Plateau and Transkei Basin were located at high latitudes during the Late Cretaceous (65°-58°S) (Hay et al., 1999;Sewall et al., 2007;Tetley et al., 2019) and positioned in the gateway between the newly opening South Atlantic, Southern Ocean, and southern Indian Ocean basins. Climate models indicate significant Cenozoic cooling arising from the opening of Southern Ocean gateways, pointing toward a progressive strengthening of the Antarctic Circumpolar Current (ACC) as the major cause for cooler deep ocean temperatures (Sijp et al., 2014;Toggweiler and Russell, 2008). Analogous arguments point to a critical role for deep circulation in controlling Late Cretaceous climate evolution (e.g., MacLeod and Huber, 1996;Robinson and Vance, 2012;Voigt et al., 2013). Therefore, because of its position at the narrow junction between the Indian and Atlantic oceans and expanding Southern Ocean, basement and sedimentary records recovered during Expedition 392 from the Agulhas Plateau will allow direct testing of these models through precise determination of the timing of large igneous province (LIP) volcanism and emplacement of the plateau and its subsequent paleoceanographic history, including documentation of ocean temperature, circulation, and sedimentation patterns during the Cretaceous and Paleogene.

African-Southern Ocean gateway circulation
In the Cretaceous greenhouse world, the role of oceanic poleward heat transport as a main driver of long-term climate change is uncertain. Low latitudinal thermal gradients and different patterns of runoff and evaporation could have shifted areas of deepwater formation, and constricted connections between basins could have led to largely internal circulation of deepwater masses in relatively small Cretaceous oceanic basins (120-80 Ma) (Friedrich et al., 2008;MacLeod et al., 2011MacLeod et al., , 2008. Numerical simulations of Cretaceous (Albian and Cenomanian/Turonian boundary) circulation do not predict overturning circulation in the African-Southern Ocean gateway, although weak circulation connecting the Pacific, Atlantic, and Indian Ocean basins is indicated (Uenzelmann-Neben et al., 2017). Cooling due to atmospheric CO 2 reduction through the Late Cretaceous, perhaps due to enhanced carbon burial (Robinson et al., 2010;Robinson and Vance, 2012) and/or evolving tectonic barriers via the formation of oceanic plateaus (Frank and Arthur, 1999), could have resulted in circulation patterns similar to modern ones, with consequent feedbacks through changing ocean heat transport. Better depth-resolved, empirical constraints on circulation coupled with modeling experiments from critical regions like the southwest Indian Ocean are needed to test and refine these hypotheses.
In the Agulhas Plateau region today, surface and deep currents transport warm and salty waters through the African-Southern Ocean gateway from the Indian Ocean into the southern Atlantic Ocean via the Agulhas Current and Agulhas rings, whereas cold water flows eastward into the Indian Ocean ( Figure F2) (de Ruijter et al., 1999(de Ruijter et al., , 2006Lutjeharms, 1996Lutjeharms, , 2006Lutjeharms and   Ansorge, 2001; Mantyla and Reid, 1995;Read and Pollard, 1999;Tomczak and Godfrey, 1994;Toole and Warren, 1993;van Aken et al., 2004;You et al., 2003). Water mass exchange in this region is controlled by seafloor topography, requiring a deep and wide gateway. Lutjeharms (1996Lutjeharms ( , 2006 observed that the Agulhas Current hugs the shelf break of the Agulhas Passage and the path of Agulhas rings is influenced by the Agulhas Ridge topography. Both the Agulhas Current and Agulhas rings maintain the energy transfer between the Indian and Atlantic Oceans (Biastoch et al., 2008(Biastoch et al., , 2009. Seafloor features such as the Mozambique Ridge and Agulhas Plateau constitute barriers for the flow of these oceanic currents and lead to modifications in flow paths. During the Cretaceous, the presence of large magmatic obstructions is hypothesized to have caused constriction of the African-Southern Ocean gateway and hence hindered water mass exchange between the Atlantic and Indian basins. There are two possible ways that LIP formation complicated the opening of the African-Southern Ocean gateway: (1) a southeast African super-LIP (140-95 Ma) (Gohl et al., 2011) or (2) the formation of two LIPs between 140 and 120 Ma (Mozambique Ridge and Astrid Ridge) (König and Jokat, 2010) and 105 and 95 Ma (Northeast Georgia Rise, Agulhas Plateau, and Maud Rise) (Parsiegla et al., 2008;Uenzelmann-Neben et al., 1999). The second hypothesis allows deepwater circulation between the Tethys/Indian Ocean and Southern Ocean/South Atlantic from ~120 Ma onward. Convergence of Falkland and Kerguelen intermediate water masses may have then initiated following tectonic subsidence of the intervening barriers in the Southern Ocean basin. Therefore, instead of the gateway slowly opening and allowing increasingly deeper water mass exchange, geophysical studies (Fischer et al., 2016;Gohl et al., 2011;König and Jokat, 2010;Schlüter and Uenzelmann-Neben, 2008a) indicate prolonged restricted circulation in the opening gateway (e.g., Transkei Basin). In this model, only surface current flow occurred between the Tethys/Indian Ocean and the evolving Southern Ocean/South Atlantic, whereas deep and intermediate water masses were blocked by this barrier. With the full clearance of the South American plate and the separation of the Agulhas Plateau-Northeast Georgia Rise-Maud Rise LIP into three parts ( Figure F1), changes in the seafloor topography may have allowed open-ocean circulation across the African-Southern Ocean gateway by ~94 Ma. To test this proposed history, drilling of Cretaceous basement and sediments from the Agulhas Plateau during Expedition 392 was intended to provide constraints on the timing and nature of African-Southern Ocean gateway evolution from the onset of Agulhas Plateau-Northeast Georgia Rise-Maud Rise LIP formation (younger than 105 Ma) to a fully open gateway (~94 Ma) (König and Jokat, 2010;Parsiegla et al., 2008). Recovery of sediments on the Agulhas Plateau and in the Transkei Basin were further intended to provide long records of changing paleodepth, paleoceanography, and paleoclimate spanning the mid-Cretaceous through the Paleogene, documenting the formation of the plateau in presumed subaerial or shallow-water environments and its subsidence to bathyal depths.

Seismostratigraphic model
Prior to drilling, the seismostratigraphic model developed for the proposed Expedition 392 drill sites ( Figure F3) was tentative because only the uppermost part of the sedimentary sequence of the Agulhas Plateau had previously been sampled by scientific drilling at only one location (International Ocean Discovery Program [IODP] Expedition 361 Site U1475 on the southwest Agulhas Plateau) (Hall et al., 2017), and therefore the interpretations for ages of reflectors should be applied with caution. The seismostratigraphic models for the Agulhas Plateau and Transkei Basin sequences were based on analysis of reflection characteristics (e.g., amplitude, frequency content of units, and continuity of reflections) and were tied to the ages of conventional gravity/piston cores (Tucholke and Carpenter, 1977) where possible and to Site U1475 for the post-Miocene sequences (Gruetzner et al., 2019).
For the Agulhas Plateau, Tucholke and Carpenter (1977) and Tucholke et al. (1984) identified four distinct seismic horizons above acoustic basement and constructed a first seismostratigraphic model (see Table T2 in Uenzelmann-Neben et al. [2020]). An unconformity above acoustic basement was cored where it crops out high on the western flank of the plateau and was found to be minimally Maastrichtian in age (~72-66 Ma). The underlying reflections terminate against the Upper Cretaceous reflector, thus documenting erosion (Uenzelmann-Neben, 1998 A 9 My hiatus across the Paleocene/Eocene boundary in the Agulhas Plateau sedimentary sequence (Tucholke et al., 1984) is interpreted as Reflector LE, which shows strong amplitudes and is mostly conformable to bounding beds ( Figure F4). Intensified bottom currents (e.g., due to the formation and strengthening of the ACC [Tucholke et al., 1984]) led to the formation of a second regional hiatus between ~33 and 29 Ma (Reflector LO) ( Figure F4) that is of medium to strong amplitude and represents an unconformity observed on the Agulhas Plateau (Uenzelmann-Neben, 2002). Reflector MM (Middle Miocene) is also likely a result of deepwater erosion and redeposi- Figure F3. Agulhas Plateau and Transkei Basin bathymetry (Sandwell and Smith, 1997). Expedition 392 sites (red stars) on seismic lines (black lines) (Uenzelmann-Neben, 1998, 2005, 2014. Yellow diamond = Expedition 361 Site U1475 (Gruetzner et al., 2019;Hall et al., 2017).  (Allen and Tucholke, 1981;Tucholke and Carpenter, 1977;Uenzelmann-Neben, 2001. tion (Tucholke et al., 1984). This reflection shows weaker amplitudes and frequent wedge-outs at the seafloor ( Figure F4). A regional hiatus of Late Miocene-Early Pliocene age (~10-6 Ma) is attributed to erosion and redeposition of sediments by Circumpolar Deep Water in the ACC (Tucholke et al., 1984) and represented by a strong reflection (Reflector LP), which is often found very close to and thus indistinguishable from the seafloor. Reflector LP is dated to 5.7 Ma (Gruetzner et al., 2019) and interpreted to represent the onset of a period of increased Atlantic Meridional Overturning Circulation. A relatively thin veneer of Pliocene-Pleistocene sediments (~0-50 m) rests on top of the Lower Pliocene reflection across most areas of the Agulhas Plateau, forming thicker drift packages only in localized areas. Several reflections in the Pliocene-Pleistocene sequence have been associated with climate-induced changes in circulation (Gruetzner et al., 2019).
In the Transkei Basin, the top of the oceanic crust is imaged as a high-amplitude, partly rugged reflection ). An undisturbed sedimentary sequence overlying basement identified as Subunit 1A is separated from the overlying heavily faulted Subunit 1B by Horizon K-T (Cretaceous/Paleogene boundary) of medium reflection amplitude (see Table T3 in Uenzelmann-Neben et al. [2020]) ( Figure F5). Sedimentary Unit 1 is topped by Horizon E (late Eocene). In Subunit 1A, a reflection band with higher amplitudes was interpreted to represent black shales (Schlüter and Uenzelmann-Neben, 2008a). The overlying Unit 2 marks a short transition zone and appears as a small but very high-amplitude reflection band with a thickness of ~25 m. The interface between Units 2 and 3 is characterized by Reflector O and represents the Eocene/Oligocene boundary ( Figure F5). Unit 3 indicates an increasing energy level and also thickens up to 70 m. The Unit 3/4 boundary is represented by Reflector M, which was hypothesized to be Middle Miocene in age. In contrast to Unit 3, overlying Unit 4 thickens up to 130 m, whereas the amplitudes weaken. Units 4 and 5 are separated by the Lower Pliocene Reflector P ( Figure F5). The youngest Unit 5 shows high-amplitude reflections .

Scientific objectives
Expedition 392 drilling was aimed at addressing the following scientific questions and objectives ( Figure F3).  It is hypothesized that the Agulhas Plateau, Northeast Georgia Rise, and Maud Rise initially formed a superplateau similar to the combined Ontong Java-Manihiki-Hikurangi Plateau (Davy et al., 2008;Hoernle et al., 2010;Timm et al., 2011) before being broken up by seafloor spreading in the mid-Cretaceous. Basement rocks recovered on the Agulhas Plateau will test whether the Agulhas Plateau-Northeast Georgia Rise-Maud Rise super-LIP formed at the Bouvet triple junction (Gohl et al., 2007;Parsiegla et al., 2008) (much like the Shatsky Rise in the northwestern Pacific [Sager et al., 1999]) or through interactions between the Bouvet and Marion hotspots with the Southwest Indian Ridge (Georgen et al., 2001). Continuous, 15-20 km long reflections observed in Agulhas Plateau basement structures are similar to lava flow sequences drilled at Shatsky Rise (Tamu Massif ) that rapidly accumulated at inferred melt production rates of 0.63-0.84 km 3 /y over a time interval of 3-4 My Gohl and Uenzelmann-Neben, 2001;Expedition 324 Scientists, 2010;Sager et al., 2013;Uenzelmann-Neben et al., 1999). These rates imply the involvement of a mantle plume.
A fundamental question concerning Cretaceous LIPs is whether they tapped a common reservoir in the lower mantle, and if so, what is the composition of this reservoir and its homogeneity/heterogeneity (e.g., Jackson and Carlson, 2011;Jackson et al., 2010 (Hanan et al., 2004;Stracke et al., 2005;Zindler and Hart, 1986). However, the stratigraphically youngest plateau lavas in some areas display a compositionally distinct (Enriched Mantle 1 [EM1]) type; e.g., (Zindler and Hart, 1986) Singgalo composition. On the other hand, recent studies of lavas from the Manihiki Plateau (Timm et al., 2011), Shatsky Rise , and Mozambique Ridge (Jacques et al., 2019) show considerably more compositional variation, suggesting that even single LIP events tap heterogeneous sources similar to ocean island basalts.
Another important question about LIPs concerns their longevity: do they represent single shortterm events occurring over a few million years, or are these volcanic provinces active over longer time periods (e.g., Bryan and Ernst, 2008)? Although the main Tamu Massif of Shatsky Rise formed between ~144 and 143 Ma, magnetic data suggest the three massifs formed over a longer time interval from M20 to M4 (146-127 Ma). The uppermost lava group at the Tamu Massif (Shatsky Rise) yielded an age (133 Ma) ~10 My younger than the main sequence of lavas (144-143 Ma) , providing evidence for volcanic rejuvenation. These lavas are geochemically identical to the main plateau stage lavas and therefore appear to have tapped the same source. At Ontong Java Plateau, the stratigraphically youngest Singgalo lavas have a distinct trace element and isotopic composition from the main Kwaimbaita/Kroenke lavas (Tejada et al., 2004(Tejada et al., , 1996(Tejada et al., , 2002. The uppermost lavas at Manihiki Plateau drilled at Deep Sea Drilling Project (DSDP) Site 317 have a distinct Singgalo-type chemical composition compared to the main low-Ti plateau lavas with Kwaimbaita/Kroenke-type compositions (Hoernle et al., 2010;Timm et al., 2011). Alkalic rejuvenated lavas with distinct (high μ [HIMU]-type) incompatible element and isotopic compositions occur on Ontong Java, Hikurangi, and Manihiki Plateaus (e.g., Hoernle et al., 2010;Timm et al., 2011). Seismic data from the Manihiki Plateau revealed several formation stages: the initial phase forming the nucleus (older than 125 Ma), the extension (125-116 Ma), and the secondary phase (100-65 Ma) (Pietsch and Uenzelmann-Neben, 2015). Seismic and geochemical data from Mozambique Ridge indicate a rapid, partly contemporaneous formation of the four segments and later postsedimentary magmatism (Fischer, 2017;Jacques et al., 2019). These observations pose the question of whether rejuvenated volcanism is a common feature on oceanic plateaus, and if so, what is its origin?
• What are the age, origin, and temporal and geochemical evolution of the uppermost Agulhas Plateau volcanic sequences? • Do the uppermost Agulhas Plateau lavas show evidence for subaerial volcanism?
• Does the Agulhas Plateau show geochemical affinities and melt production rates similar to other LIPs (e.g., Shatsky, Ontong Java, Manihiki, Hikurangi, and Kerguelen Plateaus), requiring elevated mantle temperatures and/or lower mantle source (high 3 He/ 4 He and solar Ne isotope ratios) and thus the presence of a mantle plume from the lower mantle? • Is there evidence for late-stage volcanism on the Agulhas Plateau as has been observed at Shatsky Rise and the Ontong Java, Manihiki, and Hikurangi Plateaus? How much younger is it compared to the main plateau stage, and does it show compositional differences in major (alkalic versus tholeiitic) and trace element and isotopic (e.g., more enriched) composition? • How does Agulhas volcanism correlate with the separation of Africa and Antarctica and the formation of other plateaus in the African-Southern Ocean gateway (e.g., Mozambique Ridge)?
3.2. Objective 2: did sedimentation on the Agulhas Plateau start immediately after crustal emplacement at ~100 Ma under subaerial conditions?
Following the separation of the Falkland Plateau from southern Africa during the breakup of Africa, South America, and Antarctica ( Figure F1), the onset of free water mass exchange between the Tethys/Indian Ocean and evolving South Atlantic/Southern Ocean emerged. However, the emplacement of LIPs appears to have obstructed the opening of this gateway. König and Jokat (2010) suggested that the Mozambique Ridge formed between 140 and 122 Ma and parts of the Astrid Ridge (Antarctica) were possibly still attached to the Mozambique Ridge (Fischer, 2017;Gohl et al., 2011). It is unclear whether this LIP was submarine or emplaced subaerially, but it likely formed an obstacle for the flow of intermediate and deepwater masses (Fischer and Uenzelmann-Neben, 2018). Another barrier for oceanic circulation was created with the formation of the Agulhas Plateau-Northeast Georgia Rise-Maud Rise LIP between 105 and 95 Ma, after which the Northeast Georgia Rise and Maud Rise detached from the Agulhas Plateau by seafloor spreading (Figure F1) (Gohl and Uenzelmann-Neben, 2001;Gohl et al., 2011;Parsiegla et al., 2008), leading to a widening and deepening of the gateway. Based on crustal thickness and estimated subsidence, Parsiegla et al. (2008) speculated that the central part of the Agulhas Plateau (present water depths are <3000 m) formed subaerially. The Transkei Basin formed between the Mozambique Ridge and Agulhas Plateau-Northeast Georgia Rise-Maud Rise LIPs and the African continent. Plate tectonic reconstructions (König and Jokat, 2010;Parsiegla et al., 2008) suggest that this basin may have been a restricted subbasin until ~80 Ma (Schlüter and Uenzelmann-Neben, 2008a;Uenzelmann-Neben, 2010).
Key questions regarding initial sedimentation on the Agulhas Plateau include the following: • Under what environmental conditions were sediments deposited shortly after formation of the Agulhas Plateau-subaerial, shallow or deep water, or warm or cool conditions? • How did emplacement of the plateau influence the climate, oceanic environments, and Earth's biota? • What can we deduce about water mass changes during early stages of the plateau's evolution?
Did emplacement of the Agulhas Plateau LIP interrupt an already incipient circulation?
3.3. Objective 3: did bottom currents associated with deep-and intermediate water masses as well as climatic events leave an imprint in the sedimentary record in the form of seismic reflections and unconformities? Tucholke and Carpenter (1977) and Tucholke et al. (1984) identified five distinct horizons in their interpretation of Agulhas Plateau seismic reflection data sets, of which they dated the oldest horizon from piston cores and dredge samples as Maastrichtian (see Table T2 in Uenzelmann-Neben et al. [2020]). These horizons were subsequently related to regional hiatuses resulting from local sea level highstands, initiation and spreading of the ACC, and activity of Antarctic Bottom Water (Uenzelmann-Neben, 2001. For the Transkei Basin, Schlüter and Uenzelmann-Neben (2007) presented a seismostratigraphic model tied to the model of Niemi et al. (2000) (see Table T3 in Uenzelmann-Neben et al. [2020]) that showed the importance of dating the horizons with respect to possible erosion and the evolution of ocean circulation, which may represent significant climatic episodes (e.g., OAE 3). The Cretaceous sedimentary record of the Transkei Basin represents an archive of the circulation initially restricted by the emplacement and elevation of both the Mozambique Ridge and Agulhas Plateau. Dating of these sedimentary units and unconformities in the Transkei Basin and mapping their regional extent will help us to identify traces of deepand intermediate water masses, their onset, the intensification and/or weakening of the circulation, and changes to the circulation pathways. This information will provide insight into both long-term and short-lived changes in bottom water circulation through the Late Cretaceousearly Paleogene interval in relation to the tectonic isolation and opening of this gateway.

3.4.
Objective 4: what was the paleotemperature history at southern high latitudes across the rise and decline of the Cretaceous supergreenhouse and through the early Paleogene?
Planktonic foraminifer oxygen isotope records from Falkland Plateau DSDP Site 511 indicate Cretaceous sea-surface temperatures that at times exceeded 30°C (Huber et al., 2002), yet climate simulations require unrealistically high atmospheric pCO 2 levels of 6500-7500 ppm to match these extremely warm subantarctic temperatures (Bice et al., 2003). Although it is unlikely that the mid-Cretaceous experienced such high pCO 2 levels, paleoceanographic and preservational explanations for the low δ 18 O values (e.g., diagenesis and low salinity) have been ruled out. In addition, the timing and tempo of cooling from peak Turonian temperatures is debated (e.g., Andò et al., 2013;Friedrich et al., 2012), and this uncertainty compromises parallel efforts to relate changes in the tectonic configuration of gateways and geochemically inferred patterns of circulation to climate evolution. Cretaceous foraminifers and inoceramid bivalves from the sequences recovered at Expedition 392 sites should allow construction of oxygen isotope, Mg/Ca, and, depending on organic biomarker preservation, TEX 86 paleotemperature estimates spanning the mid-Cretaceous supergreenhouse through the early Paleogene, providing a robust temperature history and reducing uncertainties about the climate history at high southern latitudes.
Recent advances in paleoclimate modeling offer potential avenues for reconciling model-data disparities for Cretaceous temperature and CO 2 estimates through consideration of cloud and biological feedbacks (Kump and Pollard, 2008;Poulsen and Zhou, 2013), emission of non-CO 2 greenhouse gases (Beerling and Royer, 2011), and regional increases in ocean heat transport (Poulsen and Zhou, 2013). Moreover, water isotope-enabled Earth system models are increasingly common, making direct comparisons between proxy data and simulations feasible (e.g., Zhou et al., 2008). Determining whether extreme warm conditions were localized or widespread through the Southern Ocean will provide an important test of possible warming mechanisms.
Specific questions to address include the following: • What was the thermal history of the Cretaceous, and was this linked to changes in atmospheric CO 2 , tectonic evolution, or some other forcing? • Were surface water temperatures over the Agulhas Plateau cool enough at any time during the Cretaceous and early Paleogene to allow for growth of Antarctic ice sheets? • Can Earth system models simulate the conditions recorded at Agulhas Plateau during the Cretaceous? What assumptions about CO 2 levels are required to reproduce these conditions? 3.5. Objective 5: how did the progressive opening of the African-Southern Ocean gateway influence Cretaceous to Paleogene circulation?
Significant changes in ocean and atmospheric circulation related to evolving bathymetry in oceanic gateways are one possible driver of global-scale climate change through the Cretaceous and Cenozoic. Many studies have proposed enhanced formation and export of Southern Component Waters starting in the Campanian (e.g., Jung et al., 2013;Murphy and Thomas, 2012;Robinson et al., 2010;Robinson and Vance, 2012;Voigt et al., 2013), promoted by the opening of the South Atlantic and establishment of connections to all major oceanic basins. However, incomplete records that lack robust age control from southern high-latitude areas currently hinder deepwater circulation reconstructions for the Cretaceous and early Paleogene. The source regions for different deepwater masses in evolving southern gateways are also controversial (see African-Southern Ocean gateway circulation), and resolving fundamental questions on circulation history requires analyses of samples from various depths in or near gateways across which circulation may have reversed.
Specific questions to address include the following: • Despite the nearly four decades since OAEs were discovered, no study has satisfactorily established the primary forcing factors that caused their formation. If increased organic productivity was the dominant cause for OAEs, why are biotic and geochemical indicators of nutrient upwelling generally not found in sediments deposited across those time intervals (Jenkyns, 2010)? On the other hand, if OAEs were caused by sluggish overturning circulation during times of high atmospheric CO 2 (Poulsen and Zhou, 2013) and oxygen-poor water masses in isolated basins (Poulsen et al., 2003), then why is there an offset in the timing of carbon isotope excursions that accompany each of the OAEs relative to peak phases of LIP eruptions and other major volcanic episodes (Jenkyns, 2010), and why are some peak carbon isotope excursions diachronous (Tsikos et al., 2004)? Recovery of complete OAE intervals with well-preserved organic matter and microfossils at the Expedition 392 drill sites will help resolve these controversies. Importantly, new OAE records from the Agulhas Plateau and Transkei Basin will shed light on relative variations in surface productivity and indicate whether there were cooling feedbacks associated with increased organic carbon burial during the OAEs and also whether there were significant changes in bottom circulation prior to, during, and after the OAE intervals. The presence of organic-rich shale with up to ~6% total organic carbon (TOC) from upper Cenomanian-lower Turonian sequences at multiple sites in the Bight Basin (Totterdell et al., 2008) and Mentelle Basin (Chen et al., 2022;Huber et al., 2019;Petrizzo et al., 2021) on the southern/southwestern Australian margin provides evidence that euxinic waters may have been present elsewhere in the southern high latitudes during OAE 2. As noted above, interpretation of the seismic profiles indicates that sediments as old as late Albian may be accessible at relatively shallow burial depths on the Agulhas Plateau, which should allow for preservation of primary geochemical signals across the OAE 1d, OAE 2, and OAE 3 intervals, and a sedimentary section extending down through OAE 3 may be recovered at the Transkei Basin site.
Key questions to address include the following: • Was there an increase in C org burial during the δ 13 C excursion intervals that define Cretaceous OAEs? If so, was the interval of increased C org burial pulsed or continuous?
• How did surface productivity, paleotemperatures, the vertical thermal and δ 13 C gradients, and bottom circulation change in the eastern South Atlantic across the OAE intervals? • Did changes in Agulhas Plateau microfossil assemblages correspond to observed OAE geochemical and sedimentological shifts, and if so, can the cause for those changes be determined?

Background and objectives
Site U1579 (proposed Site AP-10A) is located on the shallowest part of the central Agulhas Plateau (39°57.0725′S/26°14.1793′E) at 2492 m water depth. The Agulhas Plateau rises up to 2200 m above the surrounding seafloor, with the shallowest central area rising to ~1800 m on average. The central and southern parts of the plateau have a smoother topography, whereas the northern plateau is characterized by a rough topography. The sedimentary column is thicker on the central and southern Agulhas Plateau, whereas the northern plateau shows a very thin or no sedimentary cover. Basement highs characterize the plateau and have been interpreted to represent magmatic edifices. The plateau has been subject to erosion resulting in wedge-out of sequences and the formation of unconformities, which are interpreted to have resulted from oceanic currents flowing across and past the plateau since the Paleogene. The seismic data show that Site U1579 is positioned between two basement highs in a small sediment-filled depression. The seismostratigraphic model developed prior to drilling (see Background) provides a framework for interpreting the drill core results. The deepest horizon interpreted is characterized by a rugged topography and has been interpreted as top of basement ( Figure F6). Below this horizon, reflections have been observed dipping away from the basement highs. The sedimentary column shows a chaotic layer (ZS) with a strong top reflection immediately above basement. Two further strong seismic horizons can be observed separating layers of potentially Campanian, Maastrichtian, and Paleocene age, which will be confirmed in postcruise analysis. These reflections and the Campan-   ian and Maastrichtian sequences follow the basement topography. The younger sequences show continuous reflections of weaker amplitude. The youngest part of the sedimentary column is affected by strong erosion at the seafloor ( Figure F6).
Site U1579 was chosen to recover both Cretaceous and Paleogene sedimentary records and basement. Integration of seismic profiles with the drilling results allows for direct dating of the observed seismic unconformities M, LE, and LO (purple, blue, and green in Figure F6) and interpretation of their causes. Recovery of the sediment/basement interface will provide information on the age of the oldest sediments above the basement, as well as the water depth and environment at the time of deposition. At this site, records spanning the transition from the Cretaceous supergreenhouse and through the Paleogene were drilled. Based on precruise seismostratigraphic interpretations, critical interval of ocean/climate transitions such as Oi1, PETM, Cretaceous/Paleogene boundary, OAE 2 and OAE 3 were expected to be documented in the sedimentary record. The nature and age of the basement would also be unraveled by drilling at this site.

Operations
Expedition 392 started on 5 February 2022, and following quarantine, the science party boarded on 7 February under the COVID Mitigation Protocols Established for Safe JR Operations (COPE). The majority of incoming freight was loaded by the previous crew, and on 8 February the offgoing core and surface freight was loaded into two reefers. Fuel bunkering was completed via barge, and a load of fresh and frozen produce was brought aboard. The final installation, testing, and commissioning of the new 50 kVA uninterruptable power supply (UPS) for the JOIDES Resolution Science Operator (JRSO) network was done on 8 and 9 February, requiring temporary blackouts of shipboard IT services. COVID-19 rapid antigen testing was conducted for all shipboard personnel on 8 February, and PCR testing was conducted on 9 February. Site U1579 hole locations, water depths, and the number of cores recovered are listed in Table T1.
The first core of Expedition 392 was taken in Hole U1579A at 0500 h on 13 February in 2498.32 m of water. We used the advanced piston corer (APC) system to take Cores 1H-8H, and the last Calcareous nannofossil zones Figure F7. Stratigraphic summary, Site U1579. Calcareous nannofossil zones: NP following Martini (1971), CC following Sissingh (1977), and CN following Agnini et al.(2014). Black NGR data = 15-point moving average, cps = counts per second, black MS data = 25-point moving average Alkalinity measurements are from pore waters; carbonate content is from bulk sediments. Yellow shading = stratigraphic intervals for which a splice is constructed. 634.72-697.00 m CSF-A) consists of ~60 m of greenish gray well-lithified zeolitic siliciclastic sediments (sandstones, siltstones, and claystones) with glauconite. Most individual clasts are likely of volcaniclastic origin and have undergone significant alteration to clay minerals and zeolites with carbonate cementation. Rare carbonate bioclasts and foraminifers suggest marine deposition. The variety of processes influencing the composition of Unit III (volcanism, siliciclastic sedimentation, and alteration) suggests a complex history of sedimentation and postdepositional diagenesis.
Lithostratigraphic Unit V (Hole U1579D = 720.90-725.47 m CSF-A) consists of a ~5 m interval of greenish gray sediments that were recovered between basalt Units IV and VI (see below). Unit V is of a similar lithologic character to Unit III but is physically separated from Unit III by basalt Unit IV. Like Unit III, Unit V consists of well-lithified greenish gray zeolitic siltstone and sandstone sediments with glauconite. The lower contact of the sediments of Unit V with the underlying basalt of Unit VI at ~725 m CSF-A provides important clues to the emplacement of the basalt. Across the ~50 cm immediately above the contact, sediment color gradually lightens downcore from greenish gray to light greenish gray, and individual grains and sedimentary structures become less distinct. This change in sedimentary character is interpreted as evidence for contact metamorphism in the sediment due to heating following intrusion of Unit VI.

Igneous petrology
Igneous rocks were encountered at 697.0 m CSF-A in Hole U1579D below sedimentary Lithostratigraphic Unit III ( Figure F7). A 23.8 m massive interval (Unit IV) was cored between 697.0 and 720.8 m CSF-A, below which a 4.57 m sedimentary sequence (Unit V) was encountered (720.8-725.3 m CSF-A). This sequence is underlain by another massive igneous unit (Unit VI; 725.3-727.2 m CSF-A), of which 1.8 m was cored before drilling in Hole U1579D was terminated at a final depth of 727.2 m CSF-A. Lithostratigraphic Unit IV (Igneous Unit 1; 697.00-720.77 m CSF-A) is composed of plagioclase-clinopyroxene phyric basalt. The unit grades downsection toward less vesicular and more coarse-grained textures, and the central portion of the unit is well crystallized and medium grained. From the central part of the unit downsection, the groundmass grain size decreases to fine grained and eventually aphanitic at its lower contact. No abrupt or significant lithologic changes (e.g., different mineralogy or multiple cooling units) could be recognized in the 23.8 m igneous succession of Lithostratigraphic Unit IV (Igneous Unit 1). Lithostratigraphic Unit VI (Igneous Unit 2; 725.47-727.285 m CSF-A) is composed of nearly aphyric basalt, is moderately vesicular (all vesicles are filled with alteration minerals), and shows a fine-grained groundmass.
Basalt Lithostratigraphic Units IV and VI in Hole U1579D are interpreted to be sills based on systematic lithologic variations toward their upper and lower margins and the characteristics of the sediments at the contact zones. Both units show relatively wide (>20 cm) chilled (and altered) zones without significant brecciation. Unit IV, which was completely cored, also shows a spatial increase in groundmass grain size toward its center. Accordingly, both units show more characteristics of sills than lava flows. More importantly, the sediments at the contact zones above both the upper and lower igneous bodies show alteration reactions such as brick red colored streaks characteristic of thermal "baking" as well as bleaching and recrystallization.

Micropaleontology
The sedimentary succession recovered at Site U1579 contains calcareous nannofossils, foraminifers, siliceous microfossils, and palynomorphs in varying abundance and preservation. Calcareous nannofossils are generally abundant and moderately to well preserved above 635 m CSF-A (Lithostratigraphic Units I and II) and provide the primary means of biostratigraphic age control for the calcareous sediments recovered at Site U1579. Planktonic foraminifers are also generally abundant and moderately to well preserved above 635 m CSF-A and also provide supporting age control for the calcareous sediments. Benthic foraminifers, however, are present in significantly fewer numbers. Radiolarians, together with sparse silicoflagellates and diatoms, are present only across the EOT interval. Palynomorphs, including dinoflagellate cysts (dinocysts), pollen, and spores, are found in discrete organic-rich layers below 635 m CSF-A and provide important age control in the lower part of the sedimentary succession (Unit III), which is nearly devoid of carbonate and siliceous microfossils.

Paleomagnetism
Paleomagnetic measurements were performed on all archive section halves from Site U1579, in addition to 131 discrete samples. The primary purpose of these measurements was to determine magnetic polarity stratigraphy. However, additional rock magnetic experiments (anisotropy of magnetic susceptibility [AMS] and isothermal remanent magnetization [IRM] acquisition) were performed to further inform the reliability of magnetic signals, magnetic fabric, and environmental/postdepositional processes.
In Lithostratigraphic Unit I and Subunit IIa (foraminiferal and nannofossil oozes; 0 to ~145 m CSF-A), a reliable magnetostratigraphy was not determined because of the low magnetization intensities of the samples. In Subunits IIb and IIc (nannofossil and calcareous chalks; ~145-635 m CSF-A) and Unit III (zeolitic siltstones and sandstones; ~635-697 m CSF-A), the determination of a complete magnetostratigraphy is also not possible, again because of the low magnetization of the samples. Using biostratigraphic constraints, however, in some regions of Subunit IIb and Unit III it is possible to determine distinct polarities and correlate these to chrons within the geomagnetic polarity timescale (GPTS) from the Geologic Time Scale 2020 (GTS2020) (Gradstein et al., 2020;Ogg, 2020). These include chrons C24n.3n, C27n, C27r, C28n, C28r, C29n, C29r, C33r, and C34n. All of the zeolitic siltstone to sandstone with glauconite and the basalt units have normal polarity that are assigned to Chron C34n.

Stratigraphic correlation
The physical property records of Holes U1579A-U1579D were compared and correlated, where possible, to establish a common depth scale. Tie points were identified using natural gamma radiation (NGR), magnetic susceptibility (MS) from Whole-Round Multisensor Logger (WRMSL), color reflectance data, high-resolution digital core images, and red-green-blue (RGB) color space data extracted from the digital core images. A composite record was spliced for the upper 147 m core composite depth below seafloor (CCSF) of the recovered stratigraphic succession. Recognition of matching patterns in NGR records from cores and natural gamma ray from wireline logging in Hole U1579D permitted translation of core depth scales from the CSF-A scale to the WMSF scale. The correlation between NGR signals in the retrieved sediment core and natural gamma ray in the downhole logging data sets is excellent, allowing the segments of recovered core intervals to be tightly correlated to the continuous borehole logging data.

Chronostratigraphy
Calcareous nannofossils, planktonic and benthic foraminifers, dinocysts, and magnetostratigraphy provide age control for the Santonian-Lower Miocene sediments recovered at Site U1579. Very few age constraints were identified in shipboard work for the lowermost part of the sedimentary sequence recovered at Site U1579 (below ~600 m CSF-A). However, an early Santonian age (86.8-85.2 Ma) is indicated based on the dinocyst assemblage, which is consistent with the interpretation of the persistent normal polarity in this interval to represent Magnetochron C34n (the Cretaceous Normal Superchron). Calcareous nannofossil, planktonic foraminiferal, and benthic foraminiferal biostratigraphy and magnetostratigraphy further constrain the age of the sedimentary sequence between ~608 and 505 m CSF-A to the Late Cretaceous Campanian and Maastrichtian stages (83.7-66.0 Ma). The Cretaceous/Paleogene boundary was recovered in Core 392-U1579D-33R, with the base of the Paleocene identified at a thin greenish gray clay. This placement was confirmed by benthic foraminiferal biostratigraphy, in addition to the top of Cretaceous calcareous nannoflora, which demarcates the end of the Cretaceous. The identification of the top of Magnetochron C30n at ~438 m CSF-A supports this interpretation.
Calcareous nannofossil biostratigraphy provides the primary means of age control for Paleocene-Lower Miocene sediments recovered in the upper part of Site U1579, with support from planktonic foraminiferal biostratigraphy and magnetostratigraphy. The basal Eocene (~56.0 Ma) was identified in Core 392-U1579D-16R. Between the Cretaceous/Paleogene boundary and basal Eocene, 14 nannofossil biohorizons and six paleomagnetic reversals provide good age control for the Paleocene sediments. The Eocene/Oligocene boundary (33.9 Ma) is identified between ~175 and ~168 m CSF-A. Between the basal Eocene and Eocene/Oligocene boundary, 18 nannofossil biohorizons and 2 paleomagnetic reversals provide good age control for the Eocene section of Site U1579.
Near the top of the recovered sedimentary section at Site U1579, a disconformity separates a thin veneer (~1-6 m thick) of Pleistocene sediments from the underlying sediments, which are dated to approximately the Oligocene/Miocene boundary (23.04 Ma) based on calcareous nannofossil biostratigraphy. Thirteen calcareous nannofossil and three foraminifer datums provide good age control for the Oligocene sediments recovered at Site U1579 (~168 to 1-6 m CSF-A).

Geochemistry
The geochemistry program at Site U1579 was designed to characterize the composition of bulk sediment and interstitial water (IW) and report on the presence and abundance of volatile hydrocarbons for routine safety monitoring. In total, 73 headspace samples were analyzed for routine safety monitoring.

Physical properties
Physical properties of sediments and igneous rocks recovered at Site U1579 were measured on whole-round core sections, split half core sections, and discrete samples from each hole at the site to a total depth of 727.3 m CSF-A. In the upper 182 m of the site, the holes overlap stratigraphically, and physical property data were used to construct a near-complete composite splice (see Stratigraphic correlation).
NGR and MS vary between the lithostratigraphic units ( Figure F7) Moisture and density (MAD) analyses were performed on 139 discrete samples. Bulk density increases downhole following a general trend of porosity reduction. Density values are higher in Lithostratigraphic Subunit IIc but low in Unit III. Contact P-wave velocities were measured with the P-wave caliper (PWC) system from working-half sections (1-2 per core; total = 163) and from three discrete cubic samples (nine measurements). In Lithostratigraphic Unit I and Subunit IIa (0-147.10 m CSF-A), P-wave velocities vary in a narrow range of 1560-1600 m/s. Higher P-wave velocities of ~2000-2150 m/s characterize the nannofossil chalk of Subunit IIb to ~500 m CSF-A.
In the chert-rich nannofossil chalk of Subunit IIc, velocity significantly increases to 2500-3500 m/s between 556 and 635 m CSF-A. Average P-wave velocities in the underlying altered zeolitic siltstones and sandstones (Units III and V) and basalts (Units IV and VI) are 2500-3000 m/s and 4500-5600 m/s, respectively.
Thermal conductivity measured on soft-sediment whole-round sections show a general increase downhole. Values are higher in the basalts of Lithostratigraphic Unit IV (~700-720 m CSF-A), and lower values in this range reflect more vesicular textures and interbedded sediments.

Downhole measurements
Hole U1579D was logged using the quad combo tool string, which consisted of the MSS, HNGS, HRLA, DSI, and HLDS. A high-resolution run between 450 and 250 m WMSF covering the condensed Eocene-Oligocene interval was followed by a normal resolution pass over the full depth of Hole U1579D. Natural gamma ray values show variation with lithology, and the highest values are in the zeolitic silicified silt-and sandstones. Lithostratigraphic Unit IV basalts (below 697 m WMSF) show the lowest values. Increased resistivity corresponds to zones of chalk beds with claystone and chert in Subunit IIc (see Lithostratigraphy). The highest resistivity values (100-300 Ωm) were recorded in Unit IV basalts. The downhole wireline density generally follows the Pwave velocity trend. There is a distinct offset between the P-wave velocities measured on the cores and downhole. In Subunit IIb (200-556 m WMSF) the P-wave velocity is 2000-2500 m/s, which is about 300 m/s higher than measured in the laboratory.

Background and objectives
Site U1580 (proposed Site AP-09B) is located on the southern central Agulhas Plateau (40°47.1535′S/26°36.4137′E) at 2560 m water depth. The site lies about 100 km southeast of Site U1579. Bathymetric data show Site U1580 to be located on the flank of a bathymetric high that is underlain by a number of basement highs, as revealed by seismic data. A rugged topography characterizes the top of the interpreted basement. Below this horizon, reflections have been observed dipping away from the basement highs in all directions. The basement highs have thus been interpreted as extrusion centers ( Figure F8). The seismic data show a chaotic layer topped by Reflector M with a strong reflection amplitude. Another strong seismic horizon, Reflector LE, can be observed. Both Reflectors M and LE follow the basement topography. The sequence above Reflector LE shows parallel to subparallel continuous reflections of middle to strong amplitude. The youngest part of this sequence is affected by erosion at the seafloor ( Figure F8).
Site U1580 was chosen to recover both Cretaceous and Paleogene sedimentary records and basement samples. This site was especially dedicated to recover an extended record of basement material to unravel the nature of the basement and provide information on its formation age. Potential late-stage magmatism and its effect on sedimentary sequences and the environment are additional objectives. Integration of seismic profiles with the drilling results will allow direct dating of the observed seismic unconformities M and LE and interpreting their causes, and recovery of the sediment/basement interface will provide information on the age of the oldest sediments above the basement as well as the water depth and environment at the time of deposition. At this site, a sediment sequence from the mid-Cretaceous to mid-Paleogene was expected to be drilled, spanning the long-term climate transition from the Cretaceous greenhouse to the mid-Paleogene icehouse. Critical intervals of ocean/climate transitions such as Oi1 glaciation, the Paleocene/Eocene Thermal Maximum (PETM), the Cretaceous/Paleogene boundary, and OAE 2 and OAE 3 were expected to be documented in the sedimentary record. The nature and age of the basement would also be unraveled by drilling at this site.  Table T1.
At ~1700 h on 1 March, the ROP on Core 392-U1580A-43R slowed to almost zero and no noticeable progress was being made. Following an additional short advance with no recovery in Core 44R, the bit deplugger (a core barrel with a pointed, metal tip) was dropped twice in an attempt to clear any material blocking the bit. Core 45R then advanced 3.2 m and recovered 3.25 m. It was determined from recovered pieces that a chert layer of loosened rock was slowing the ROP and preventing recovery.
The sediment/basalt contact was difficult to determine based on coring parameters, likely due to multiple chert/silicified horizons in the sediments immediately overlying the basalts that resulted in very low overall ROP. Although core recovery was low, pieces of basalt were recovered in Cores  assembled and deployed at 0900 h. The FMS-sonic tool consists of the FMS, DSI, and HNGS. Two passes were conducted, with both reaching the bottom of the hole at ~521.5 m WMSF. The tools were back at the surface at 1535 h. For the final downhole logging run, the Ultrasonic Borehole Imager (UBI) tool string consisted of the UBI, General Purpose Inclinometry Tool (GPIT), and HNGS.
The UBI tool string was run in the hole at 1610 h. One pass was completed to 504.5 m WMSF. The second pass was aborted after difficulties, and it was later determined that the transducer subassembly motor was sticking. The UBI logging run was completed with the tools at the surface at 0020 h on 7 March. The drill pipe cleared the rig floor at 0705 h, ending Hole U1580A. A total of 68 cores were taken in Hole U1580A over a 533.9 m interval (recovery = 65.7%). Total time on Hole U1580A was 232.8 h (9.73 days).
A new C-4 RCB bit was prepared, and after lowering the drill pipe to near the seafloor, the vessel was offset 20 m east. An RCB core barrel with center bit was installed, and Hole U1580B was spudded at 1710 h from a seafloor depth of 2571.5 m drilling depth below rig floor (DRF  (Figure F9). Coring of the igneous intervals in this sequence yielded excellent recovery (average = ~84%). All igneous rocks recovered at Site U1580 are classified as aphyric or slightly plagioclase and/or olivine phyric basalts, with 10 igneous units defined on the basis of differences in macro-and microscopic texture and identifiable contacts. Throughout the recovered basalts, olivine crystals, as phenocrysts or in the groundmass, are completely replaced by alteration phases (predominantly clay minerals), contributing to the overall moderate-to-high degree of alteration of these units. In addition to near-continuous recovery of igneous successions, isolated basalt fragments were also recovered in primarily sedimentary intervals. For instance, Unit XIII (478.53-490.54 m CSF-A; 478.53-490.54 m CCSF), which mainly comprises calcareous chalk, claystone, and siltstone, also contains three unoriented pieces of basalt; these basalt cobbles are distinct from the igneous units above and below Unit XIII and likely represent a thin interval of basalt not coherently recovered at ~488 m CSF-A.
The intercalation of igneous bodies and sediment packages in Hole U1580A implies that these igneous units represent either lateral intrusions (sills) or that they were emplaced as lava flows on which sediments were deposited after each eruption. Based on several lines of evidence, we interpret this igneous succession as sills. Sharp igneous contacts and broad chilled margins (without volcanic glass), slow gradational changes in crystallinity (grain size) toward coarsely crystalline interiors, and certain mineralogic textures (subophitic and doleritic) of the recovered units resemble sills rather than lava flows. Additional compelling evidence for sill intrusions into sedimentary deposits is the thermal overprint or "baking" (contact metamorphism) of the adjacent sedimentary lithology, which is repeatedly observed in Hole U1580A. Similar reactions may also appear beneath thick lava flows but would not be expected above a flow because any sediments deposited on an existing lava body should be younger in age.
The recovery of such an extensive (>120 m) sill complex near the center of the Agulhas Plateau and at such high stratigraphic position (with respect to the bulk of the seismically defined plateau "basement") was not expected. According to biostratigraphically constrained ages, the sills in Hole U1580A were intruded into sediments of late Cenomanian to Turonian or possibly Coniacian age, implying the sills to be younger. Such late-stage or "rejuvenated magmatism" of oceanic plateaus is often characterized by alkaline composition. However, preliminary geochemical data of the recovered basalts (Sites U1579 and U1580) indicate that the sills have a tholeiitic composition, which is characteristic of the main plateau building phase of oceanic LIPs. Postcruise research on the sills cored at Site U1580 will investigate links to the two sills that were also cored 98 km away at the base of Hole U1579D.

Micropaleontology
The

Paleomagnetism
Paleomagnetic measurements were undertaken on all archive section halves from Holes U1580A and U1580B and on 68 discrete samples from Hole U1580A. Demagnetization experiments and rock magnetic analyses were also performed to constrain magnetic polarity and the magnetic mineralogy of the sedimentary and igneous units defined at Site U1580 ( Figure F9). Paleomagnetic results indicate that the units sampled at Site U1580 are reliable recorders of magnetic field direction. Magnetic polarity was determined for 61 of the 68 cores measured from Hole U1580A and all four cores measured from Hole U1580B. Fifteen magnetic reversals were identified, and normal and reversed polarity intervals were correlated to chrons within the GPTS from the GTS2020 (Gradstein et al., 2020;Ogg, 2020 53.6-56 Ma. Because of low magnetization intensity, no magnetic reversals were identified in the lower Eocene section of Site U1580. The uppermost sediments recovered at Site U1580 (Unit I; 0-3.42 m CSF-A), which rest on a hiatal surface above the Eocene sediments below, are dated to the Pleistocene based on foraminiferal and nannofossil biostratigraphy.

Geochemistry
The geochemistry program at Site U1580 was designed to characterize the composition of bulk sediment and IW and diagnose the abundance of volatile hydrocarbons for routine safety monitoring. Methane above the detection limit was not found in any samples. Traces of propene (17.35 ppmv), iso-pentane (5.75 ppmv), iso-hexane (3.87 ppmv), and h-hexane (2.12 ppmv) were detected at ~87 m CSF-A. In total, 83 sediment samples from Site U1580 were analyzed for bulk carbon and nitrogen content to 485.99 m CSF-A. Total carbon (TC) and CaCO 3 range 0-14.5 wt% and 0-97 wt%, respectively, which is consistent with the observed pelagic nannofossil oozes and chalks, zeolitic sand/siltstones, limestone, and claystone lithologies. Average TOC is 0.64% ± 0.27% with minimum and maximum concentrations of 0% and 9.34%, respectively. Five samples with TOC content exceeding 1% are from below ~315 m CFS-A, and two samples composed of calcareous siltstone and black claystone exceed 5% and are from the lowest part of the hole deeper than 410 m CSF-A.
Samples from nine representative sills drilled at Site U1580 were selected for inductively coupled plasma-atomic emission spectrometry (ICP-AES) analyses. Based on classic discrimination diagrams for igneous rocks, all three samples classify as tholeiitic basalts, plotting together with tholeiitic lavas from the neighboring Mozambique Ridge and the only hitherto available basement (dredge) samples from the Agulhas Plateau.

Physical properties
Physical properties of sediments and igneous rocks recovered at Site U1580 were measured on whole-round core sections, split half core sections, and discrete samples to a total depth of 528.58 m CSF-A in Hole U1580A. Complementary downhole logging data sets were also collected from Hole U1580A. Between ~40 and 74 m CSF-A, cores from Hole U1580A and Hole U1580B overlap stratigraphically. Measured variations in physical properties arise from lithification with increasing burial depth and from variations in lithologic composition. The upper part of this interval shows small variations in MS, NGR, P-wave velocity, and density (Lithostratigraphic Unit I and Subunits IIa and IIb; 0 to ~208 m CSF-A). The overall higher P-wave velocities and densities and color change toward darker and more reddish layers in the lower part of Subunit IIb are attributed to diagenetic changes and an increase in clay content. Anomalous physical properties downhole were recorded in the zeolitic sandstone, siltstones, and claystones of Subunit IIIa (293.51-349.98 m CSF-A), characterized by a decrease in bulk density, increase in porosity, low P-wave velocities (as low as ~2000 m/s), and a sharp drop in thermal conductivity compared to the strata above and below. Increased MS and NGR values also correlate with the zeolitic sediments of Unit III (~293.51-407.46 m CSF-A) ( Figure F9). Deconvolved Natural Gamma Radiation Logger (NGRL) spectral data indicate that potassium is enriched to ~0.5-2.0 wt% in the zeolitic sandstones to claystones of Unit III, likely reflecting an increase in authigenic minerals rich in potassium such as glauconite and celadonite. Exceptional peaks in NGR (related to high uranium content) were also observed in a few dark layers in Cenomanian-Turonian deposits (Unit XII; ~471.6-478.53 m CSF-A; 471.60-478.53 m CCSF) sandwiched between basalt layers (Units XI and XIII).

Downhole measurements
Downhole measurements at Site U1580 consisted of wireline logging in Hole U1580A on 5 and 6 March 2022. No downhole temperature data were measured at this site. In addition to standard sonic and MS data, high-resolution density, natural gamma ray, neutron porosity, electrical resistivity, and FMS and UBI imagery provide a continuous borehole record, documenting lithologies of unrecovered stratigraphic intervals where coring gaps occurred in Hole U1580A. Downhole gamma ray spectroscopy data indicate that sediments of Lithostratigraphic Units II and III occupy two distinct compositional domains of potassium/thorium ratios. Potassium-rich Unit III is characterized by anomalously high porosity (>60%), which is confirmed by MAD analysis. The integrated interpretation of downhole data is instrumental to identify the true thickness of sediments and nature of their contacts with basalts below 407 m WMSF. The UBI and FMS images display various degrees of alteration/fracturing in basalts and sharp transitions to the interbedded sediments. The sedimentary rocks sandwiched in basalt units are characterized by elevated uranium content with peaks at about 2 ppm. The cross-dipole setup of acoustic logging enables a detailed core-to-seismic integration that includes analysis of elastic anisotropy.

Background and objectives
Site U1581 (Figure F10). This sequence shows a number of high-amplitude internal reflections. Below the base Reflector P (pink line, Figure F10) of the Agulhas Drift, the reflection characteristics change to lower reflectivity. The Agulhas Drift is underlain by the M Drift, a sediment drift formed during the Oligocene and Miocene (Schlüter and Uenzelmann-Neben, 2008b). The M Drift shows a strike almost perpendicular to the Agulhas Drift, which is indicative of a strong change in the direction of the prevalent bottom current. Reflector M dominates the seismic image of the Oribi drift in the middle of the sequence. Reflector E forms the base of Seismic Unit 2, which is only up to 30 m thick. Reflectors K-T and B characterize the deepest seismic unit above rugged oceanic basement ( Figure F10).
Site U1581 was chosen to recover an Upper Cretaceous and Paleogene sedimentary record, as well as a partial Neogene sequence. This site was especially dedicated to target Reflector B in the Cretaceous sequence. This reflector was interpreted to represent black shales, and recovery of material from the reflector and above/below was intended to provide information on the formation of black shales in connection with ocean anoxia. Integration of seismic profiles with the drilling results will allow direct dating of the observed seismic unconformities K-T, E, O, M, and P and interpreting their causes. Further objectives concern paleoenvironment and paleodepth of the Transkei Basin. At this site, critical intervals of ocean/climate transitions such as Mi1 and Oi1 glaciations, the PETM, the Cretaceous Paleogene boundary, and OAE 2 and OAE 3 were expected to be documented in the sedimentary record.

Operations
After completing the 338 nmi voyage to Site U1581 (proposed Site TB-01A), the vessel arrived on site at 2345 h on 9 March 2022. The thrusters were lowered, and the ship was switched to full DP mode at 2357 h. The APC/XCB bottom-hole assembly (BHA) was assembled, and we began tripping pipe to the seafloor. We attempted to shoot the first APC core from 4573.8 meters below sea level (mbsl); however, this resulted in no recovery (water core ing continued to 207.2 m CSF-A (Core 24H). The APCT-3 tool was run on Cores 4H, 7H, 10H, and 13H, with good data collected for all four. Pressure in the pipe increased while drilling the rathole of Core 24H. A mud sweep was pumped, and the core barrel was pulled back to the surface while the crew continued to circulate and condition the hole with an additional two mud sweeps. Site U1581 hole locations, water depths, and the number of cores recovered are listed in Table T1.
The core barrel recovered 8.11 m (Core 392-U1581A-25G; the designation for a core with an uncertain depth). A fray in the core line was discovered and repaired. Cores 26H-29H advanced to 233.8 m CSF-A. We then switched to the HLAPC system. Cores 30F-38F advanced to 276.1 m CSF-A. We then switched to the XCB system, and Cores 39X-41X advanced to 300.5 m CSF-A; however, strong swells and resultant low recovery and poor core quality led to the termination of coring in Hole U1581A at 1800 h on 13 March. A total of 41 cores were taken in Hole U1581A over a 300.5 m interval (recovery = 90.9%). Total time on Hole U1581A was 104.4 h (4.35 days).
The drill string was pulled out of the hole, and pipe was tripped back to the vessel. The bit cleared the rig floor at 0825 h on 14 March. It was determined that a compassionate evacuation was needed for a crew member. An attempt was made to recover the acoustic positioning beacon; however, it was ultimately deemed lost.
The vessel was switched from DP to cruise mode at 0945 h, and the thrusters were up and secured at 1014 h, beginning the sea passage to Gqeberha (formerly known as Port Elizabeth   In preparation for downhole logging, the hole was swept with sepiolite mud to flush cuttings and the bit released at 1835 h on 24 March. The hole was further displaced with mud, and the bottom of the drill string was placed at 77.8 m CSF-A for downhole logging. The first downhole logging run was with the Versatile Seismic Imager (VSI). The tool began its descent but encountered a solid ledge at 222.4 m CSF-A. The tool was worked up and down for almost an hour, but was unsuccessful at passing the ledge. The decision was made to bring the tool back to surface and lower the drill pipe to cover the ledge. The VSI cleared the rig floor, and the drill pipe was run in to 408.5 m CSF-A. Because of the lack of daylight for another VSI run, a modified triple combo tool string was made up with the DSI in place of the HRLA unit. The tool string consisted of the HNGS, HLDS, DSI, and MSS.
Upon make-up, a problem was found with power to the lower portion of the tool string. This was replaced, and the tool string was deployed. At 2606.8 m DRF (still within the water column), there was growing evidence of an electrical fault with the tool. The tool was brought back to the surface, where it was repaired and redeployed. The triple combo tool reached 1300.0 m DRF but was again showing an electrical fault, and the decision was made to terminate logging. The tool string was pulled out of the hole, and the cause of the electrical fault was much later determined to be the conductors in the collector and pinched conductors in the logging head. The triple combo tools were disassembled, and the drill string was tripped back to the vessel, clearing the seafloor at 0555 h and the rig floor at 1510 h on 26 March, ending Hole U1581B. A total of 73 cores were taken in Hole U1581B over a 708.1 m interval (recovery = 76%). Total time on Hole U1581B was 243.12 h (10.13 days).

Lithostratigraphy
A ~994 m thick Pleistocene-Campanian sedimentary succession composed of calcareous and siliciclastic sediments was recovered at Site U1581 ( Figure F11). The upper part of the succession is relatively carbonate rich, whereas the lower part is dominantly siliciclastic in composition. The sedimentary sequence is divided into Lithostratigraphic Units I and II, both of which are further divided into two subunits (Ia, Ib, IIa, and IIb) ( Figure F11).
Unit I (0.0-390.05 m CSF-A) is a 390 m sequence of Pleistocene-upper Paleocene biogenic ooze with variable amounts of sand, silt, and clay. The unit is divided in two subunits (Ia and Ib) on the basis of a higher concentration of siliciclastic material in Subunit Ib. Subunit Ia (Hole U1581A = 0-198.24 m CSF-A) consists principally of greenish gray, light yellowish brown, and light brown clayey nannofossil ooze with biosilica, nannofossil ooze, and grayish green foraminifer ooze with sand, silt, and clay intervals. The basal contacts of thin sand intervals that overlie nannofossil oozes are typically sharp or erosive when recovered. Carbonate content in Subunit Ia is highly variable, ranging between ~20 and 80 wt% in biogenic intervals and <1 wt% in siliciclastic intervals ( Figure F11). Subunit Ib (Hole U1581A = 198.24-262.11 m CSF-A; Hole U1581B = 289.00-390.05 m CSF-A) consists predominantly of siliciclastic sand, silt, and clay with occasional biogenic sediments (e.g., silty nannofossil ooze). Biogenic sediments are less common in Subunit Ib and occur as irregular, thin layers within thick packages of sand and silt. Siliciclastic sediments consist of medium-to fine-grained sand and silt layers that are massive or laminated and are occasionally normally graded. Carbonate content is generally low (<2 wt%) in Subunit Ib, except for in discrete decimeter-scale nannofossil-rich intervals, where it can be as high as ~40 wt%. The contact between Units I and II at 390.05 m CSF-A is marked by a change in lithology from intercalated siliciclastic and calcareous sediments to dominantly siliciclastic sediments, as well as a decrease in average carbonate content ( Figure F11).
Unit II (395.70-993.97 m CSF-A) is a 582 m thick middle Paleocene to Campanian sequence of siliciclastic sediments consisting of sand, silt, and clay and sandstone, siltstone, and claystone. This unit is divided into two subunits (IIa and IIb) based on the degree of lithification (clay versus claystone). Subunit IIa is ~90 m thick and consists of dark to very dark greenish gray fine-grained sand and silt, clayey silt, and very dark greenish gray or black clay, clay with silt, and minor greenish gray to black silicified siltstone with glauconite. Bedding ranges from massive to laminated, with normal grading in some intervals. Well-preserved inoceramids (bivalves) and other shell fragments are observed macroscopically throughout the subunit. The contact between Subunits IIa and IIb is sharp, with Subunit IIb marked by a sharp decline in MS, an increase in dry density, and a decrease in porosity. Subunit IIb is ~507 m thick and consists of dark to very dark greenish gray siltstone, fine-to medium-grained sandstone, and very dark greenish gray or black claystone (Figure F11). The sandy layers become less frequent downhole and are not present below ~791 m CSF-A. Mass movement is reflected by repeated fining upward sequences of sand to silt or silt with soft-sediment deformation features such as convolute lamination or load casts. However, finer grain sizes in Unit II (clays and fine silts) suggest a more distal location with respect to the sediment source in comparison to Unit l.

Micropaleontology
The 994.02 m sedimentary succession recovered at Site U1581 consists of varying proportions of siliciclastic sediment and biogenic ooze that contains calcareous nannofossils, foraminifers, dinocysts, radiolarians, and diatoms in varying abundance and preservation state. In Lithostratigraphic Figure F11. Stratigraphic summary, Site U1581. Calcareous nannofossil zones: NP following Martini [1971]; CC following Sissingh [1977]   Subunit Ia (0-198.24 m CSF-A; Pleistocene to Late Miocene), calcareous nannofossils and foraminifers are generally abundant and moderately to well preserved. Reworking of nannofossils is particularly prevalent in more siliciclastic rich sediments. Diatoms and other siliceous microfossils (including radiolarians and silicoflagellates) are common to abundant and well preserved in the uppermost ~7 m of the sequence. Below this, moderately preserved diatoms are present in few to rare numbers to ~110 m CSF-A, whereas radiolarians are common to ~93 m CSF-A and present in few numbers to ~175 m CSF-A. Dinocysts are well preserved when present, but their abundance varies throughout Subunit Ia from present in the Pleistocene and Pliocene to sparse in the Miocene.
In Subunit .05 m CSF-A; Late Miocene-middle Paleocene), calcareous nannofossils are common to abundant and moderately preserved in many samples; however, they are occasionally rare or absent entirely in some intervals, particularly in coarser grained lithologies. In Unit II (395.70-994.02 m CSF-A; Paleocene-Campanian), calcareous nannofossil abundance and preservation varies significantly. Nannofossils are present in few to common numbers in only some Paleocene samples, and many samples are completely barren. Nannofossils are generally present only in few numbers in the Cretaceous, but they are surprisingly well preserved, particularly between ~470 and 770 m CSF-A. Below this depth, abundance decreases and preservation deteriorates, with the lowermost sediments devoid of nannofossils. Foraminifers are almost entirely absent in the >63 μm size fraction in Unit II; however, small foraminifers <20 μm are observed in smear slides throughout the unit. Pyritized diatom fragments are common throughout much of this unit. Although they are often fragmented, some samples contain nearly complete pyritized diatom valves. Preservation of dinocysts and miospores is moderate to good in Unit II. Both are common to abundant throughout all samples investigated and contain rich and diverse assemblages, which will provide ample opportunity for postcruise study of the terrestrial and marine paleoenvironmental evolution of the region.
The siliciclastic component of Site U1581 sediments includes coarse-grained units with sharp bases and normal grading that are interpreted as turbidites. As a result, an uncertain proportion of the microfossils found in the sediments of Site U1581 were likely transported from nearby shallower settings. Consequently, there is a significant component of reworked microfossils throughout the sedimentary succession at Site U1581, which complicates identification of the biohorizon tops of species. However, the biohorizons identified demonstrate a clear age progression, suggesting that transported sediments were deposited quasi-contemporaneously.

Paleomagnetism
Paleomagnetic measurements were undertaken on archive section halves from Holes U1581A and U1581B and on 110 discrete samples from both holes. Paleomagnetic experiments included alternating field demagnetization, AMS, and IRM acquisition. These experiments were performed to constrain magnetic polarity and the magnetic mineralogy of sedimentary units from Site U1581. Paleomagnetic results are of variable quality, and magnetic polarity could only be determined from ~50% of the cores recovered from Hole U1581A and ~65% from Hole U1581B. From cores with clear magnetic polarity, nineteen reversals were identified and correlated to chrons within the GPTS from the GTS2020 (Gradstein et al., 2020;Ogg, 2020

Chronostratigraphy
Calcareous nannofossils, planktonic foraminifers, diatoms, dinocysts, and magnetostratigraphy provide age control for the Campanian to Pleistocene sediment sequence recovered at Site U1581 ( Figure F11)

Geochemistry
The geochemistry program at Site U1581 was designed to characterize the composition of bulk sediment and IW and report on the presence and abundance of volatile hydrocarbons for routine safety monitoring. Methane values range 0.7-1458 ppmv. Hydrocarbons with longer chain lengths up to n-hexane (C 6 ) were detected from 490.52 to 990.12 m CSF-A (bottom of Hole U1581B). The consistent presence of higher hydrocarbons up to hexane in the lower part of Hole U1581B is con-sistent with a thermogenic origin of the hydrocarbons. Notably, ethane/methane (C 2 /C 1 ) ratios are markedly elevated between 490.52 and 655.22 m CSF-A, with a maximum at 610 m CSF-A. In total, 204 sediment samples were analyzed for bulk carbon and nitrogen analyses at Site U1581. TC and carbonate weight percentages range 0-10.01 and 0-83.36 wt%, respectively, which is consistent with the deposition of pelagic biogenic oozes and lithologic observations. Greater variability and overall the highest carbonate content is observed in biogenic oozes between the seafloor and 198 m CSF-A. Below 200 m CSF-A, inorganic carbon and carbonate content typically decrease to below 10 wt% and average 0.97 and 8.11 wt%, respectively. The main carbonate mineral phase is likely calcite in the biogenic ooze above 200 m CSF-A; however, in the more siliciclastic sediments below 200 m CSF-A, the carbonate content may include other carbonate minerals, including siderite and dolomite. Despite uncertainty in the carbonate mineral phases present, carbonate carbon persists in selected samples to the bottom of the analyzed sedimentary section (~993 m CSF-A). The average TOC content is 0.46 ± 0.31 wt% with minimum and maximum concentrations of 0 and 1.69 wt%, respectively. Average TOC is slightly elevated to 0.52 wt% from 200 m CSF-A to the base of the recovered section at Site U1581.

Physical properties
Standard measurements of physical properties were made on cores from Holes U1581A and U1581B using the WRMSL, Section Half Multisensor Logger (SHMSL), and NGRL track instruments. Discrete measurements were also made for MAD analysis, thermal conductivity, and P-wave velocities on the PWC system.
Core disturbance was common in Hole U1581A cores collected with the APC, HLAPC, and XCB systems, affecting the continuous track measurements of physical properties for cores. Discrete sampling for thermal conductivity and MAD analyses avoided core disturbance wherever readily identifiable. Many of the clay-rich lithologies at Site U1581 expanded in volume upon recovery, likely altering some physical properties. In Hole U1581B, the trends in physical properties show a continuation of observations recorded in Hole U1581A. Average NGR levels and deconvolved uranium, thorium, and potassium concentrations are higher at Site U1581 compared to the two previous sites on the Agulhas Plateau, reflecting lower carbonate content and higher clay content in the Transkei Basin. P-wave velocity, thermal conductivity, and bulk density values all increase downhole through the biogenic oozes of Lithostratigraphic Subunit Ia in the upper 198.24 m. At the Subunit Ia/Ib boundary (~198.24 m CSF-A), a sharp ~0.2-0.3 g/cm 3 increase in bulk density occurs where a hiatus is indicated by biostratigraphic analysis. Finer scale changes in physical properties at Site U1581, such as in NGR and MS, are associated with decimeter-scale nannofossil ooze/chalk beds, which are likely turbiditic in origin. A major increase in MS to ~400 instrument units (IU) occurs in the clayey silts and silty clays of Subunit IIa (395.70-486.07 m CSF-A) and corresponds with the Cretaceous/Paleogene boundary interval. The grain density of claystones in Subunit IIb (486.07-994.02 m CSF-A) is high (~2.75-2.85 g/cm 3 ) and likely relates to the presence of authigenic minerals such as pyrite and siderite. P-wave velocity at Site U1581 increases downhole relatively linearly from ~1650 m/s at the seafloor to ~2200 m/s at the base of Unit II (994.02 m CSF-A).

Downhole measurements
Downhole logging measurements at Site U1581 included formation temperature measurements in Hole U1581A. Because of electrical connection problems during wireline logging in Hole U1581B, only natural gamma ray wireline logging data were collected between ~80 and 220 m WMSF using the Enhanced Digital Telemetry Cartridge device run at the top of the triple combo tool string (see Operations).
The logging data provide downhole natural gamma ray data across the poorly recovered interval at the base of Pliocene-Pleistocene drift deposits. These data allow for detailed correlation between Cores 392-U1581A-10H through 26H and downhole logging data. A cyclic pattern in the downhole natural gamma ray profile is characteristic for alternating sand and clay-rich turbiditic deposits.
Borehole formation temperatures were measured using the APCT-3 tool during recovery of

Background and objectives
The northern Agulhas Plateau is characterized by a rough topography and a number of basement highs separated by depressions with only a thin sedimentary cover. In between the interpreted basement highs, thicker sediment packages filling depressions or sediment drifts are observed. This distribution of sedimentary sequences attests to the strong erosional/nondepositional influence of the Agulhas Retroflection, as well as Circumpolar Deepwater flowing over the northern Agulhas Plateau. Furthermore, the northern slope of the Agulhas Plateau lies under the influence of North Atlantic Deepwater and Antarctic Bottom Water, both of which shape sediment drifts. Site U1582 (proposed Site AP-07A) is located on the flank of one of those basement highs (37°1.5002′S/24°59.7168′E) at 3441 m water depth, where a small ledge is formed (Figure F12). The seismic data show basement below an ~100 m thick sedimentary sequence, which is characterized by Reflectors M and LE (see Background). The uppermost part of basement further shows only few internal reflections (Figure F12), which differs from the seismic character of the basement at Sites U1579 and U1580. This has been interpreted to represent more homogeneous basalt at Site U1582.
Site U1582 was selected to recover both the thin Paleogene-Cretaceous sedimentary cover and basement samples. This site was especially dedicated to recover an extended record of basement material to unravel the nature of the basement and provide information on its age and geochemistry. Additional objectives include identifying potential late-stage magmatism and its effect on sedimentary sequences. Integration of seismic profiles with the drilling results will allow direct dating of the observed seismic unconformities M and LE and interpreting their causes, and recovery of the sediment/basement interface will provide information on the age of the oldest sediments above the basement as well as the water depth and environment at the time of deposition. At this site, a thin sediment sequence from the mid-Cretaceous to mid-Paleogene was expected to be drilled, spanning the long-term climate transition from the Cretaceous greenhouse to potentially the early Paleogene. The recovery of basement rocks at this site on the northern Agulhas Plateau was expected to help address fundamental questions about the formation of this LIP.

Operations
The vessel arrived at Site U1582 at 1420 h on 27 March 2022. The thrusters were lowered starting at 1424 h, the vessel was switched from cruise to DP mode at 1440 h, and the rig floor given the all clear. A new C-7 bit with a mechanical bit release was made up, and a four-stand RCB BHA was run into the hole starting at 1645 h. The drill pipe was lowered to 3378.3 m DRF, the sinker bars were installed, and the RCB core barrel was deployed. Site U1582 hole locations, water depths, and the number of cores recovered are listed in Table T1.
The first attempt for core at 2340 h was a water core. Starting on 28 March, four more attempts were made to get the first core. On the sixth attempt, Hole U1582A was spudded at 0405 h, with Core 1R recovering 1.9 m. The seafloor was established at 3429.4 mbsl. Coring continued, and basement was reached at 42.7 m CSF-A. Half cores were taken on Cores 6R and 7R. Core 7R was cored to 48.0 m CSF-A, but more than 100% was recovered (48.68 m CSF-A). Coring was terminated at 1915 h to trip out of the hole because severe weather was expected over the site within 24 h.
The pipe was tripped out of the hole, clearing the seafloor at 1945 h. On 29 March at 0215 h, the pipe trip was completed with the BHA at the rig floor. The bit cleared the rig floor at 0455 h, ending Hole U1582A. The rig floor was secured at 0600 h, and the vessel was switched to cruise mode at 0604 h. The thrusters were raised and secured by 0618 h, and the sea passage for waiting on weather began with the vessel transiting north at 10.6 kt. The vessel turned and took a westerly heading at 1818 h. Beginning on 31 March, the vessel turned south and then east to return to Site U1582. A total of seven cores were taken in Hole U1582A over a 48 m interval (recovery = 38.5%). Total time on Hole U1582A was 38.16 h (1.59 days).  On 1 April, the vessel arrived back at Site U1582. The thrusters were lowered starting at 1228 h, and the ship was switched to DP mode at 1245 h, ending the waiting on weather window. The vessel was positioned 10 m west of Hole U1582A. A new C-7 RCB bit was made up, and the BHA and pipe were tripped to the seafloor. A core barrel with a center bit was dropped, and Hole U1582B was spudded at 2315 h on 1 April. Seafloor was set at 3440.7 m DRF (by offset). Hole U1582B was drilled down to a hard contact at 36.3 m CSF-A. The center bit was retrieved, and coring began at approximately 0530 h on 2 April. Core 2R was on deck at 1100 h. The ROP was very slow, averaging just over 1 m/h because the hard basalt formation and shallow depth of the hole limited how much weight could be put on the bit. Coring continued to 3 April, and Core 5R was recovered at a final depth of 55.6 m CSF-A (recovery to 53.73 m CSF-A).
The weather over the site was expected to deteriorate over the next 2 days, thus forcing us off site and into an early transit to Cape Town, South Africa. Coring was terminated at 0230 h on 3 April, and the pipe was tripped back to the vessel. The bit cleared the rig floor at 1250 h, ending Hole U1582B and Site U1582. The vessel was switched to cruise mode at 1236 h, the thrusters were raised and secured by 1249 h, and we began our sea passage to Cape Town, South Africa, at 1250 h with the vessel making a wide turn to the northwest. A total of four cores were taken in Hole U1582B over a 19.3 m interval (recovery = 52.2%). Total time on Hole U1582B was 48 h (2.0 days). Expedition 392 officially ended with the first line ashore at 1154 h on 7 April.

Lithostratigraphy
Site U1582 consists of a 40.92 m sequence of sediments overlying a 16.9 m interval of basalt with intercalated thin layers of sediment. The sequence recovered at Site U1582 is divided into lithostratigraphic Units I and II ( Figure F13). Unit I is entirely comprised of sediments and further divided into Subunits Ia and Ib, and Unit II consists of pillow basalts with interspersed sediments.
Unit I (Hole U1582A = 0-40.42 m CFS-A; Hole U1582B = 36.30-36.83 m CSF-A) is a ~40 m sequence of nannofossil ooze, clayey silt, and clayey nannofossil ooze with sand in the upper sections and limestone at the base ( Figure F13). The unit is divided into Subunits Ia and Ib based on a downhole increase in lithification. Both subunits contain variable amounts of sand, silt, clay, and manganese nodules. Subunit Ia consists of light brown clayey silt, nannofossil ooze, clayey nannofossil ooze with sand, and manganese nodules. At 2.0-2.11 m CSF-A, there is a dark brown, ~11 cm manganese nodule, and there are additional small nodules of manganese throughout the entire subunit. From 7.32 m CSF-A to the base of the subunit, medium to coarse sand-sized and occasionally pebble-sized manganese nodules are present. The contact between Subunits Ia and Ib was not recovered and occurs in an interval of poor recovery between Cores 392-U1582A-4R and 5R (~21.71-31.07 m CSF-A).
Subunit Ib consists of limestone, with one cobble-sized manganese nodule at 45.5 m CSF-A.  Figure F13). In Hole U1582A, Unit II is comprised of a 7.76 m sequence of pillow lava basalts with thin, intercalated limestone pockets. Thirteen igneous units were identified and defined as individual inflationary pillow lava lobes in Hole U1582A. The sedimentary material in Lithostratigraphic Unit II consists of thin (<10 cm) limestones and is considered to be pockets of carbonate sediment that occupy interstices between individual pillow lobes.
The upper part of Lithostratigraphic Unit II in Hole U1582A (Igneous Units 1-3) is composed of predominantly plagioclase phyric pillow basalts, which all show a yellowish brown alteration pattern. There is abundant fresh glass along the chilled contact of the pillows, as well as an outer layer of palagonized (weathered) glass and possibly some sedimentary material. The basalt in the interior of the lobes is fine-grained, moderately to highly altered, and sparsely plagioclase phyric. Many intervals are also moderately vesicular with typical, radially arranged vesicle trains inward of the chilled margin, with all of the vesicles filled with calcite. The common yellowish brown color of the basalts in the upper part of Lithostratigraphic Unit II indicates considerable weathering and oxidation. The lower part of Lithostratigraphic Unit II in Hole U1582A (Igneous Units 4-13) is also composed of predominantly plagioclase phyric pillow basalts. However, most of these basalt units possess a natural gray color and show no signs of oxyhydroxide staining, indicating a lesser degree of oxidative weathering than the uppermost basalts of the unit.
Hole U1582B was spudded about 20 m away from Hole U1582A and delivered the same principle lithologies, although igneous rocks were first encountered ~4 m shallower ( trated before drilling ceased at 53.69 m CSF-A in Hole U1582B. The ~4 m shallower occurrence of the igneous basement in comparison to Hole U1582A may attest to the considerable lateral variability of pillow lava flow fields, which likely created an irregular sediment/basalt contact at this site. In total, 27 igneous units were identified in Hole U1582B, including 26 pillow lava units and one sequence of a hyaloclastite breccia. As in Hole U1582A, the pillow lava units were defined and interpreted as individual inflationary lava lobes. The entire igneous succession cored in Holes U1582A and U1582B is interpreted as a stack of pillow lava lobes based on observed structures such as curved chilled margins, the presence of thick (fresh and altered) glass rinds along these margins, radially arranged vesicle trains, and concentric vesicle bands parallel to the curved margins. The basalts recovered in both holes are characterized by the presence of pockets or intervals of interpillow carbonate sediment often recovered in direct contact with the pillow rims. The presence of calcareous nannofossils in at least some of these carbonate pockets rules out a purely diagenetic origin of the carbonate. Instead, the evidence of mingling of plastic lava with unconsolidated sediments is tentatively interpreted as peperite, implying an interaction of lava and coexisting sediment during eruption.

Micropaleontology
The 53

Paleomagnetism
Paleomagnetic measurements were undertaken on all archive section halves from Holes U1582A and U1582B and on four discrete samples from Hole U1582A. Demagnetization experiments were performed on both sedimentary and igneous units recovered from Site U1582. Results indicate that the sampled units at Site U1582 are reliable recorders of magnetic field directions. Magnetic polarity was constrained from all measured cores. Intervals of both positive and negative inclination were identified in Hole U1582A, indicative of reversed and normal geomagnetic polarity, respectively. All measured cores from Hole U1582B had negative inclination (normal polarity). Because of the condensed sediment interval collected in each hole, correlation to the GPTS (Gradstein et al., 2020;Ogg, 2020) was difficult; however, we suggest a correlation with Chron C34n of the predominantly normal polarity zone observed from ~21 m CSF-A downhole (see Chronostratigraphy).

Chronostratigraphy
Calcareous nannofossils, foraminifers, and magnetostratigraphy provide age control for the Campanian(?) to Upper Miocene sediments recovered at Site U1582 in Lithostratigraphic Unit I. The sedimentary cover is very thin (~40 m) at Site U1582 yet represents a long period of time (as much as 70 My), indicating very low sedimentation rates and/or significant erosion. The presence of abundant manganese nodules is consistent with this observation. The low sedimentation rates and other processes such as reworking of older sediment and burrowing, together with coring disturbance, make this a particularly challenging site for chronostratigraphy. Because of significant mixing, the youngest age diagnostic taxa within a given sample or set of samples was used for biostratigraphic age assessment, with outlier bioevents excluded that appear to result from drilling disturbance or contamination.
The nannofossil ooze, clayey silt, sand, and manganese nodules of Subunit Ia (Hole U1581A = 0-21.76 m CSF-A) show predominantly reversed magnetic polarity with some intervals of normal polarity usually associated with manganese nodules. Nannofossil assemblages in this subunit often include a significant component of reworking and presence of multiple biostratigraphic marker taxa indicating broad age ranges. Foraminifers in the mudline sample (0 m CSF-A) indicate a very young (Pleistocene-recent) age for the seafloor, and nannofossils indicate a Late Miocene age between ~10.9 and 5.5 Ma for the 0.43-1.35 m CSF-A interval. The 1.85-1.98 m CSF-A interval is assigned an Eocene to mid-Oligocene age (~35-27 Ma), and the 4.71-6.76 m CSF-A interval is assigned an early to early middle Eocene age (~54-47 Ma) based on nannofossil biostratigraphy. Samples between 7.63 and 11.90 m CSF-A contain assemblages of mixed ages with a significant component of older material reworked into younger sediment, together with likely contamination from younger material due to fall-in. However, although the nannofossil assemblage contains Cretaceous taxa similar to those in the deeper samples, the presence of Paleogene nannofossils indicate an early Eocene or younger age for this interval.
The 11.90-21.71 m CSF-A interval of Subunit 1a contains a solely Cretaceous nannofossil assemblage with background taxa similar to those in the sediment intercalated with the basalt of Unit II, indicating a Campanian to earliest Maastrichtian age despite the dominance of older (Coniacian) species. The dominantly reversed polarity of this interval also precludes a Coniacian age. However, the possibility that the nannofossil assemblage is entirely reworked through this interval cannot be discounted. The lowermost sediments recovered above basalt at Site U1582 are limestones in Subunit Ib (Hole U1582A = 40.92-31.00 m CSF-A; Hole U1582B = 36.83-36.30 m CSF-A), which contain only very rare and poorly preserved Cretaceous nannofossils that provide no additional age control. The limestone shows normal magnetic polarity with no reversals between it and the basalt below. This may suggest that the limestone was deposited during the long Cretaceous Normal Superchron (C34n), indicating an age of Santonian or older; however, this age assessment is very tentative.
Nannofossils and magnetostratigraphy provide age constraints for the basalt and sediments of Unit II (Hole U1582A = 48.68-40.92 m CSF-A; Hole U1582B = 53.73-36.83 m CSF-A). The limestones intercalated with basalt contain a sparse, moderately preserved Late Cretaceous nannofossil assemblage. Nannofossil marker taxa suggest an early Turonian to Santonian age (~93.7-84 Ma). The broad age interpretation of Turonian-Santonian is consistent with the persistent normal magnetic polarity of the basalt, which can therefore be assigned to Superchron C34n. Given the sparse nature of the assemblages, postcruise research may provide additional nannofossil age constraints for the sediments recovered within the basalts.

Geochemistry
The geochemistry program at Site U1582 was designed to characterize the composition of bulk sediment and IW and report on the presence and abundance of volatile hydrocarbons for routine safety monitoring.
A total of six headspace samples were taken and analyzed for routine safety monitoring. Hydrocarbons in headspace samples were detected in Hole U1582A. Methane was above the detection limit in three samples, with concentrations of 0.68 and 0.51 ppmv in samples from Cores 2R and 3R, respectively. Hydrocarbons with longer chain lengths up to n-hexane (C 6 ) were not detected in any of the headspace samples.  (Figure F13). In Subunit Ib, inorganic carbon averages 0.62 wt%. TOC is zero for all samples except Sample 1R-1, 82-83 cm, which has a concentration of 0.05 wt%. Total nitrogen was measured but remained below 0.05 wt% (average = 0.04 wt%), which is at or close to the detection limit, for the samples analyzed from Hole U1582A.
Total sulfur concentrations range from below detection limit to 0.41 wt%.

Physical properties
Standard measurements of physical properties were made on cores from Holes U1582A and U1582B using the WRMSL, SHMSL, and NGRL. Discrete measurements were also made for MAD analysis, thermal conductivity, and P-wave velocities on the PWC system. Physical property data from Site U1582 show a progression with depth that delineates the poorly consolidated clayey nannofossil ooze of Lithostratigraphic Subunit Ia (0-31.00 m CSF-A) from the underlying lithified limestone of Subunit Ib (Hole U1582A = 31.00-40.92 m CSF-A) and from the deeper pillow basalts with interspersed pockets of limestone in Unit II (Hole U1582B = 36.83-53.73 m CSF-A) ( Figure F13). Subunit Ia contains unlithified sediment with high porosity (65-82 vol%), low MAD bulk density (1.40-1.62 g/cm 3 ), low PWC P-wave velocities (~1600 m/s), and low thermal conductivity (0.9-1.2 W/[m·K]). In comparison, the underlying more lithified limestones of Subunit Ib have much lower porosity (~25%), higher average PWC P-wave velocity (~3000 m/s), and higher bulk density (~2.33 g/cm 3 ). The dark colored pillow basalts (L* = ~20-40) of Unit II have higher NGR values (~20 counts/s) and higher MS (~500-1000 IU) than the light-colored basalt ( Figure  F13).

Preliminary scientific assessment
Expedition 392 recovered sedimentary sequences and igneous rocks at three sites on the Agulhas Plateau (Sites U1579, U1580, and U1582) and a sedimentary sequence from one site in the Transkei Basin (Site U1581) (Figures F3, F14, F15). The main sedimentary sections recovered at the Agulhas Plateau sites span the lowermost Miocene through uppermost Cenomanian and comprise a wide range of lithologies from nannofossil oozes/chalks to zeolitic sandstones ( Figure F16).
Several key stratigraphic intervals that were well recovered at the Agulhas Plateau sites include the Oligocene-Miocene transition and a nearly complete spliced Oligocene sequence at Site U1579, the EOT at Site U1579, the Paleocene/Eocene boundary at Site U1580 (double cored), the Cretaceous/Paleogene boundary at Sites U1579 and U1580, and the upper Campanian at Sites U1579 and U1580. The thick sedimentary sequence cored in the Transkei Basin at Site U1581 also contains several important stratigraphic intervals, including an expanded Campanian claystone sequence and, potentially, the Cretaceous/Paleogene boundary (requiring further stratigraphic analysis postcruise) (Figures F14, F15).
Igneous rocks cored at Sites U1579 and U1580 are classified as plagioclase-clinopyroxene phyric basalts, aphyric or slightly plagioclase basalts, and olivine phyric basalts. At both sites, the basalt units are interbedded with sedimentary units. The intercalation of igneous bodies and sediment packages implies that these units represent either lateral intrusions (sills) or that they were emplaced as lava flows on which sediments were deposited after each eruption. Based on several lines of evidence, igneous successions at these sites are interpreted as sills. Preliminary geochemical analysis of the recovered basalts from both sites indicates that the sills have a tholeiitic composition, which is characteristic of the main plateau building phase of oceanic LIPs.
A sequence of plagioclase phyric pillow basalts was recovered at Site U1582, providing information on the eruptive nature of the Agulhas Plateau magmatism. The broadly constrained early Turonian-Santonian biostratigraphic age (~84-94 Ma) of the interpillow carbonate sediments may place these lavas several million years younger than the postulated formation age of the Agulhas Plateau based on seismic studies and plate tectonic reconstructions (95-105 Ma) (e.g., Gohl and Uenzelmann-Neben, 2001;Gohl et al., 2011). Direct radiometric dating of plagioclase phenocrysts of the Site U1582 basalts should be possible and will determine whether the reconstructions need to be revised or, alternatively, whether this pillow lava field belongs to a late "rejuvenated" or "posterosional stage" of volcanism. However, preliminary shipboard portable Xray fluorescence spectrometry (pXRF) analyses indicate a tholeiitic composition for the Site U1582 pillow lavas, which may indicate that these basalts represent the main phase of Agulhas Plateau volcanism.
Unfavorable weather conditions during the last week of the expedition prevented the recovery of deep basement samples at Site U1582; instead of the intended 300 m CSF-A, we could only drill to ~50 m CSF-A. However, as has been outlined above, the recovered basement cores will allow dating pillow lava flows and thus bear huge potential to add to the reconstruction of the emplacement of the Agulhas Plateau. Geochemical and age comparison with material retrieved at Maud Rise during Ocean Drilling Program (ODP) Leg 113 and the Northeast Georgia Rise during ODP Leg 114 will further contribute to a better understanding of the development of this LIP obstructing the African-Southern Ocean gateway during the Late Cretaceous. Camp. Tur.
Cenom. Drilling at Site U1581 revealed that an interpreted black shale reflector deep in the sedimentary sequence did not form the top of an organic-rich layer. However, the combination of recovered thin layers of siltstones, anisotropy observed for MS in the deepest cores recovered at Site U1581, peaks in P-wave velocity and density, and the computation of synthetic seismograms and thus core-log-seismic integration with dates from the sills recovered at Sites U1579 and U1580 will allow a study of the farfield effect that the emplacement of the Agulhas Plateau sills may have created.

Coniacian
In addition to these highlighted examples, the cores, downhole logging data, and IW samples collected at Expedition 392 sites will allow most of the main expedition objectives to be addressed. These objectives broadly fall into three areas: (1) age and origin of the Agulhas Plateau, (2) paleoceanographic and climate history, and (3)   Plio.

Age and origin of the Agulhas Plateau
• The successful recovery of igneous rocks at Sites U1579, U1580, and U1582 containing fresh plagioclase and other minerals typical of main-stage lavas suitable for 40 Ar/ 39 Ar dating studies should yield reliable ages for the igneous rocks recovered on Expedition 392, thereby answering fundamental questions regarding the emplacement age of the Agulhas Plateau. • The timing of sill intrusions at Site U1580 will be particularly informative, both for understanding the temporal window in which magmatism occurred on the Agulhas Plateau and, potentially, also for identifying regional, or even global, impacts of LIP volcanism on circulation and climate in the Late Cretaceous. • Radiogenic (e.g., Sr, Nd, Hf, Pb, and Os) and stable (e.g., O on fresh glass and mineral phases) isotope ratios from igneous rocks recovered at Sites U1579, U1580, and U1582 will allow characterization of the magma source composition and comparison with other regional or global LIPs. • Abundant occurrence of fresh clinopyroxene and some chromium-rich spinel in the igneous material from Sites U1579, U1580, and U1582 will allow for the reconstruction of the primitive Figure F16. Age-depth plots, Expedition 392. The four sedimentary sequences recovered at the Agulhas Plateau and Transkei Basin are shown. Ages according to the GTS2020 (Gradstein et al., 2020). Insert map modified from Figure F3. Upward triangle = nannofossil base, downward triangle = nannofossil top, diamond = foraminiferal datum, circle = dinocyst datum, plus sign = magnetic polarity reversal, vertical line = datum depth uncertainty, horizontal line = age uncertainty, horizontal arrow = sediment could be younger (left arrow) or older (right arrow) than the position of the datum, wavy line = unconformity, pale red box = assemblage based age ranges for Site U1582, question mark = uncertainty.  melt (including volatile) compositions from melt inclusions (e.g., in olivine, spinel, or pyroxene) to evaluate melting processes and extents, temperatures and depths. These planned investigations will enable evaluation of whether a mantle plume drove Agulhas Plateau magmatism. • At Site U1582, combined petrological and trace element data on whole rocks and in particular on fresh glass (representing the melt composition) can be used to constrain the magma source temperature and degrees and depths of melting (e.g., Fitton et al., 2004;Herzberg et al., 2007;Husen et al., 2013;Putirka, 2008), crucial for distinguishing LIP formation models. Additionally, the analysis of CO 2 and other volatile gases in fresh glass from the basalt recovered at Site U1582 will provide information on the paleoenvironment during emplacement of the magmatic material. • Benthic foraminiferal assemblages and organic-walled microfossils at Sites U1579 and U1580 will provide insight into the paleobathymetric evolution of the Agulhas Plateau and, importantly, allow testing of whether areas of the central and southern Agulhas Plateau was subaerially exposed during its early stages of formation. • The recovery for the first time of Upper Cretaceous igneous and sedimentary sequences from the Agulhas Plateau provides an opportunity to revise and complement existing plate kinematic reconstructions of the early Southern Ocean and the relative motion of Africa. Paleolatitudinal constraints derived from paleomagnetic and geochronologic analyses will improve our understanding of the formation of evolving gateways and the role of the Agulhas Plateau as a volcanotectonic barrier in the context of Gondwana breakup. Although the Agulhas Plateau is thought to have formed at 65°-58°S during the mid-Cretaceous (100-95 Ma), there is significant uncertainty in the timing and position (latitude) of emplacement because of the current lack of data.

Paleoceanographic and climate history
• The recovery at Site U1579 of rhythmically bedded limestone and claystones with striking white and red alternations, coupled with a good magnetostratigraphic record and nannofossil biostratigraphy, will reveal the pacing of Campanian climate by orbital forcing and also contribute to timescale development for this understudied interval of the Cretaceous. • An expanded Campanian mudstone succession recovered at Site U1581 will permit reconstruction of ocean and climate conditions adjacent to the Agulhas Plateau during the Late Cretaceous using organic-walled microfossils and organic biomarkers, providing information on ocean connectivity between the Atlantic and Indian through the Southern Ocean, as well as terrestrial climate history. • The excellent preservation of nannofossils in the Campanian section at Site U1581 will provide an unprecedented opportunity to examine coccolithophore evolution over this time interval. Initial shipboard investigation revealed an intriguing combination of southern high-latitude and mid-latitude assemblages present at the site. • The good recovery of the Cretaceous/Paleogene boundary interval at Sites U1579 and U1580 (and possibly U1581) will provide new materials for high-resolution investigations of the boundary event. Because the Agulhas Plateau was located in relative proximity to the Deccan Traps (western India) at the end of the Cretaceous, detailed study of the new sequences recovered during Expedition 392 should allow for examination of the timing and effects of Deccan volcanism in the context of the boundary impact event. • The expanded Late Cretaceous and early Paleogene sedimentary sequences recovered at Sites U1579-U1581 contain abundant calcareous microfossils, which will provide a good basis for calcareous nannofossil and foraminiferal paleoecological studies and improvement of biostratigraphic frameworks for the southern high latitudes. • The abundant occurrence and good preservation state of foraminifers in the Miocene-Maastrichtian sequences and inoceramid (bivalves) in the Campanian sequences will additionally provide potential for conventional oxygen and carbon isotope analysis, as well as clumped isotope analysis, for reconstruction of paleotemperature over both long and short timescales through the Cretaceous and Paleogene. • Two nearly complete Paleocene records were recovered at Sites U1579 and U1580 and will provide an excellent opportunity to study that time interval in the Southern Hemisphere where many records have unconformities or low carbonate content. These new materials recovered during Expedition 392 will be particularly ideal for examining plankton evolution following the Cretaceous/Paleogene mass extinction. • A Paleocene/Eocene boundary section was recovered at Site U1580 at relatively shallow subseafloor depths (~60 m) in two parallel holes. In contrast to most deep-sea records, Site U1580 sediments remain carbonate rich across the boundary, without a clay layer that typically results from carbonate dissolution during the PETM. The minimal carbonate dissolution at Site U1580 places a new constraint on the degree of carbonate compensation depth (CCD) shoaling during the PETM, and also presents a unique opportunity to study the morphology, ecology, and geochemistry of planktonic and benthic foraminifers during the event.
Foraminifer-based stable isotope investigations at Site U1580 may reveal an exceptionally complete record, particularly of the earliest phases of the event's onset, which is typically truncated by carbonate dissolution at other well-studied sites. • Results from preliminary rock magnetic experiments performed on discrete sediment samples collected from Expedition 392 highlight distinct variations in magnetic mineralogy at Sites U1579 and U1580, with some variations correlating with observed changes in IW geochemistry, and others with major environmental crises (e.g., Cretaceous/Paleogene and Eocene hyperthermal events). These results suggest that magnetic mineralogy can be used as an environmental proxy to highlight changes in diagenesis, redox conditions, and paleoclimate throughout the sampled sedimentary packages. • Paleogene sediments from Sites U1579 and U1580 are suitable for neodymium isotope analyses of fish teeth and debris, which will allow fingerprinting of deepwater masses and tracing their pathways as oceanic gateways opened in the Cretaceous and Paleogene. • A nearly complete Oligocene record extending through the Oligocene-Miocene transition was recovered at Site U1579. The location of Site U1579 is well situated to examine circulation changes that occurred in conjunction with establishment of large ice sheets on Antarctica at the EOT and also the gradual initiation of the ACC through the Oligocene and Miocene. Calcareous microfossil paleoecological analysis and geochemical proxy analysis, and potentially organic biomarker analysis, will enable examination of temperature and upper water column hydrographic changes through this time interval, both from the perspective of long-term trends and orbitally paced variability. These new records from the Agulhas Plateau are also particularly well situated to shed light on the timing and regional impact of the pre-Neogene development of the Agulhas Current. • Excellent physical properties data (natural gamma ray, density, seismic velocity, resistivity, porosity, MS, FMS, and UBI) collected both from the cores and downhole at Sites U1579 and U1580 will allow for successful core-log-seismic integration. In the absence of downhole logging data at Sites U1581 and U1582 (because of technical problems and bad weather), the physical properties data collected from the cores will be used for this purpose. Synthetic seismograms will allow the transfer of geological information to seismic data and thus the spatial extrapolation of this information. Ages and origins will be assigned to prominent reflections. Hiatuses and condensed sections can be characterized in three dimensions, and the seismostratigraphic models for the Agulhas Plateau and Transkei Basin will be revised. Pathways of paleocurrents will be reconstructed with the potential to form the starting point for numerical simulation of sediment transport (e.g., in combination with grain size information). • Core-log integration of exceptional natural gamma records obtained from the Paleocene and Eocene sections drilled at Sites U1579 and U1580 will also facilitate correlation to highresolution stratigraphic records from Shatsky Rise (North Pacific, ODP Leg 198) and Walvis Ridge (South Atlantic, ODP Leg 208). Detailed intra-and interbasin correlation will improve the stratigraphic framework for Expedition 392 cores and allow placement of the regional Agulhas Plateau paleoceanographic records into a global context.

Rock-water interactions and chemical evolution
• In addition to radiometric dating of igneous sill intrusions at Sites U1579 and U1580, postcruise investigations will focus on how volcanic intrusions have altered the organic-rich sediments these sills have penetrated through and the consequences of the magma-sediment interactions.
• The sediments and IW from the Agulhas Plateau Sites U1579 and U1580 provide an excellent opportunity to investigate submarine (reverse) weathering of LIP basalts and authigenic mineral formation in sediments in contact with igneous sills to assess impacts on seawater chemistry and long-term carbon cycling.

Additional research directions
• At Site U1581 in the Transkei Basin, Pliocene-Pleistocene sediments of the Agulhas Drift were well recovered and characterized by interbedded pelagic oozes and distal turbidites. This sequence will allow for correlation to detailed seismic stratigraphy, as well as investigation of sediment provenance via comparison with onshore deposits and interpretation of sedimentary processes. • The Pliocene-Pleistocene sequence recovered at Site U1581 also contains a good record of siliceous microfossils. Postcruise analysis of diatom accumulation and assemblage composition will allow assessment of the strength and extent of Antarctic Bottom Water flow through the Agulhas Passage during the mid-Pleistocene transition.

Outreach
Expedition 392 had one Education and Outreach Officer, Maryalice Yakutchik, a multimedia journalist/science writer from the United States. The Outreach Officer collaborated closely with scientists, technicians, drillers and ship's crew to engage and interact with a wide range of audiences around the world about science and day-to-day goings-on during the expedition. The aim was to be creative and jargon-free in video broadcasts, social media posts, and blogs on the JOIDES Resolution website, as well as in pitches and articles for external sites.

Live ship-to-shore broadcasts
During the expedition, the Education and Outreach Officer scheduled 40 ship-to-shore live Zoom broadcasts and completed 37 (3 were canceled by organizers). All tours were conducted by the Outreach Officer along with at least one scientist participating as tour co-leader; 15 different scientists took part in co-leading this educational effort during the expedition. Each tour was tailored individually for students ranging from second grade to postgraduate university level, including one special education class.
A typical session began with an introduction to our location on the Agulhas Plateau or Transkei Basin and an explanation of expedition goals. Tours of the ship followed the core path as it comes on board. Scientists working in various laboratories spoke about their research methods, showed images and instruments, and answered questions. A dedicated question and answer session concluded each tour/event.
In addition to classroom events, the Expedition 392 Outreach Officer (with scientists) broadcast live during the following: • A science and technology festival in the UK (panel discussion at Festival of Tomorrow), • A master's level science-writing symposium at Johns Hopkins University, • IODP-related events at universities in Australia and the US, • An AstroGeo workshop in France with Jacques Laskar, and • A national conference for educators in Houston, Texas (US) (National Science Teaching Association).
These broadcasts, arranged across seven countries and in five languages, reached thousands of viewers across a wide range of demographics. Numerous broadcasts were recorded for future listening/viewing. Some audiences were small to medium (classrooms with 12-80 students), and others numbered in the hundreds, some with media present. The Outreach Officer sent organizers educational material and links related to https://joidesresolution.org prior to the broadcasts and a follow-up and survey link after the broadcast.

Storytelling
The Education and Outreach Officer published 21 stories/blogs on the JOIDES Resolution ship's log page. Eleven nonfiction narrative stories written by the Outreach Officer covered science, operations on the drill floor, and activities in various laboratories and shipboard life and profiled scientists on Expedition 392. These stories, which included photos and videos, were interspersed with weekly updates about the progress of the expedition as reported by Gabriele Uenzelmann-Neben, Co-Chief Scientist for Expedition 392.
The Outreach Officer encouraged and worked with scientists to write blogs about their science/experiences on JOIDES Resolution; two pieces by early career scientists were published on the JOIDES Resolution website. The Outreach Officer also assisted members of the science party (notably six early-career scientists) in pitching, crafting, and editing stories for their home institutions' publications, magazines, and/or websites (i.e., Smithsonian Institution, Australian National University, UK Research and Innovation (UKRI)-IODP Newsletter, and Kent State University). For example, the outreach officer wrote the following for Rice University: https://news.rice.edu/news/2022/voyage-reveals-wonder-and-beauty-long-dead-ocean-dwellers.

Social media
In addition to blogs for the JOIDES Resolution Expedition 392 web page, the Outreach Officer created and published daily posts, including photos and videos, on a range of social media. The aim-to maintain a fresh presence with new content every single day throughout the expeditionwas met: Facebook: >70 posts. Twitter: >70 posts. Instagram: 27 photo stories.
The latest Facebook analytics (as of 2 April 2022) indicate that 37,781 people were reached between 6 March and 2 April, indicating a 51% increase. Actions on page were up 400%, Page Views were up 52%, Page Likes were up 180%, Post Reach was up 193%, and Post Engagement was up 53%.
The following were the top posts: • Facebook post on 29 March links to What's in a Name blog: 15,113 people reached, including 347 engagements, which represents a 3.1× higher than usual distribution score. • Facebook post on 19 March of photo and haiku: 8,512 people reached, including 443 engagements, which represents a 4× higher than usual distribution score. • Facebook post on 1 March of a photo and story about the Cretaceous/Paleogene boundary: 7,100 people reached, including 643 engagements. • Facebook post on 20 February of a photo and story called Cretaceous mania: 12,600 people reached, including 1,559 engagements.

Special project: 3.9.2.haiku
A haiku is an ancient poetic form, a compact bit of language that describes and reveals, with discipline and economy, timeless truths about natural phenomena. Starting with the outreach presentation shared during hotel quarantine, "3.9.2.haiku" was introduced as a collective project. The Outreach Officer first suggested that the science team think of haiku as the verbal equivalent of a core and then assigned word prompts to individual scientists based on their areas of expertise, requesting they write and share an initial haiku following the presentation.
During Weeks 3 and 4 of Expedition 392, the Outreach Officer organized two haiku writing workshops for the science team and technicians to further explore this poetic form. All were invited to join in creating a centerpiece haiku project: a series of connected/related haiku that describes each of the 68 cores from Hole U1580A, in its entirety, from top to bottom. Each scientist was asked to commit to describing two cores of their choosing. With nearly 100% participation from the science party, as well as some technicians, the project (as of 3 April) represents more than 30 distinct voices as well as a wide range of nationalities and scientific expertise.