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doi:10.2204/iodp.proc.313.103.2010

Paleontology

Biostratigraphic age assignments in Hole M0027A were determined from integrated calcareous nannofossil, planktonic foraminifer, and dinocyst zonations (Fig. F33). Paleobathymetry and paleoenvironments were determined from benthic foraminifers, dinocysts, and terrigenous palynomorphs. Palynomorph studies allowed for interpretation of both marine and terrestrial paleoenvironments. Calcareous microfossil occurrences ranged from absent to abundant, and preservation ranged from poor to excellent, with the best preserved, most abundant specimens and most diverse assemblages often occurring in the finer grained sediments. In general, organic microfossils were abundant and well preserved in fine-grained sediments. Reworking of all microfossil groups was found in some samples and was distinguished from in situ assemblages.

Pleistocene, Miocene, Oligocene, and possible uppermost Eocene sections were identified and integrated with Sr isotope stratigraphy to establish a chronostratigraphic framework for Hole M0027A (Fig. F34). The use of multiple planktonic microfossil zonations allowed ages to be refined, as the boundaries between nannofossil, planktonic foraminifer, and dinocyst zones tend to be offset. For example, planktonic foraminifer Zone M1/N4 overlaps with calcareous nannofossil Zone NN1 and dinocyst Zone DN1 only between 23.2 and 23.8 Ma, confirming that lowermost Aquitanian sediments were recovered in Hole M0027A. Similarly, the boundary between the early and middle Miocene, which falls within calcareous nannofossil Zone NN4 and dinocyst Zone DN4, was identified using the boundary between planktonic foraminifer Zones N7 and N8 (or M4 and M5).

Paleodepths varied throughout Hole M0027A, ranging from inner neritic (0–50 m) to outer neritic (100–200 m). In several sequences, paleobathymetric fluctuations indicated shallowing-upward successions that occurred within a sequence stratigraphic framework. In general, good correlation was found between sedimentary facies and benthic foraminifer biofacies. Similarly, benthic foraminifer water depth estimates and palynological estimates of proximity to shoreline were consistent. Palynological data support previous reconstructions of a warm, humid early Neogene climate.

Biostratigraphy

Calcareous nannofossils

A total of 86 samples from Hole M0027A were examined for calcareous nannofossil biostratigraphy. Sample spacing was generally one sample every three cores (approximately every 10 m), although fewer samples were taken within sandy units. Additional samples were also examined near sequence boundaries and when initial analysis indicated an unconformity. The total abundance of calcareous nannofossils within samples ranged from barren to very abundant. Preservation also varied significantly throughout the hole, ranging from poor to good, with the best preservation in the uppermost part of the hole. Members of the Noelaerhabdaceae family dominate assemblages throughout the hole. Reworked Paleogene material is also prevalent throughout.

Horizons recovered in Hole M0027A contain Pleistocene, Miocene, and Oligocene assemblages (Table T4; Fig. F35). Sediments from Cores 313-M0027A-1H through 13H (0–23.79 mbsf) are assigned to Martini's (1971) Zone NN21 based on the presence of Emiliania huxleyi, which first occurred at 0.25 Ma. This section can be further divided based on the zonation of Hine and Weaver (1998). Sediments from the top of the hole through Sample 313-M0027A-5H-CC (0–11.14 mbsf) contain common E. huxleyi and are tentatively assigned to the Emiliania huxleyi Acme Zone (<90 ka). Samples 313-M0027A-8H-1, 79 cm, to 13H-1, 111 cm (16.05–23.79 mbsf), contain assemblages with fewer E. huxleyi but common small Gephyrocapsa spp. and are therefore assigned to either the Transitional Zone or the Gephyrocapsa aperta Acme Zone, which together span 90–250 ka. A single sample from Core 313-M0027A-15H (27.42 mbsf) is tentatively assigned to Zone NN19 (0.41–1.97 Ma) based on the presence of a single Pseudoemiliania ovata. Samples from Cores 313-M0027A-17H through 51H (28.21–110.66 mbsf) are barren of nannofossils and are unzoned. Below the barren interval, samples from Cores 313-M0027A-59H through 69X (176.81–207.44 mbsf) contain poorly preserved calcareous nannofossils with no definitive age-diagnostic taxa, so that interval is also unzoned.

Two samples from Cores 313-M0027A-72H and 73X (210.67–212.13 mbsf) are assigned to undifferentiated Zone NN6/NN7 based on the last occurrence (LO) of Coccolithus miopelagicus (11.0 Ma). No other biostratigraphic events are found in the cores above the LO of Sphenolithus heteromorphus, making it impossible to further refine the zonal assignment at this time. This interval is characterized by the occurrence of a Catinaster-like species (possibly a broken Discoaster) that makes zoning difficult without the presence of other index taxa.

The LO of S. heteromorphus is found in Sample 313-M0027A-75X-1, 100 cm (217.21 mbsf), although this may not be the actual extinction (13.6 Ma) of this species. The interval from this sample to Sample 313-M0027A-83R-3, 12 cm (236.52 mbsf), is assigned to Zone NN5 (13.6–15.6 Ma) based on the presence of S. heteromorphus and the absence of Helicosphaera ampliaperta. The LO of the latter species occurs in Sample 313-M0027A-86R-2, 130 cm (246.46 mbsf). There is no evidence of a hiatus above this sample, so this likely represents the extinction of H. ampliaperta, which occurred at 15.6 Ma. The section from Core 313-M0027A-86R to Sample 313-M0027A-116R-1, 40 cm (335.56 mbsf), is assigned to Zone NN4 (15.6–18.3 Ma) based on the co-occurrence of H. ampliaperta and S. heteromorphus and the absence of Sphenolithus belemnos. The next core (313-M0027A-117R; 339.21 mbsf) contains a sparse assemblage of nannofossils that are not age diagnostic. The interval including Cores 313-M0027A-122R through 127R (347.46–360.94 mbsf) is barren of nannofossils. Cores 313-M0027A-139R and 142R (393.90–402.41 mbsf) also contain a sparse nannofossil assemblage that is not age diagnostic; therefore, the interval including Cores 313-M0027A-117R through 142R (339.21–402.41 mbsf) is unzoned.

A diverse nannofossil assemblage is present again beginning in Sample 313-M0027A-144R-1, 120 cm (409.56 mbsf). Characteristic lower Miocene marker taxa are rare or absent in sediments from Hole M0027A; therefore, the age assignment of this interval is based primarily on the absence of species, as well as the general assemblage. The assemblage in this sample is older than the first occurrences (FOs) of S. heteromorphus (18.2 Ma) and H. ampliaperta (~21.0 Ma), although the age of the latter datum is not well constrained. Triquetrorhabdulus carinatus, the LO of which marks the base of Zone NN3 (19.6 Ma), is sporadically present below this horizon, indicating Zone NN2 or older. Furthermore, the interval from Sample 313-M0027A-144R-1, 120 cm, to 174R-1, 123 cm (409.56–494.99 mbsf), is above two secondary events: the last common occurrence of T. carinatus (22.9 Ma), which is near the base of Zone NN2, and the crossover in abundance of Helicosphaera euphratis with Helicosphaera carteri, which is tentatively dated to 21.5 Ma. This interval also contains consistently present Cyclicargolithus floridanus, as well as more frequent occurrences of Discoaster deflandrei. Thus, samples from Cores 313-M0027A-144R through 174R (409.56–494.99 mbsf) are assigned to Zone NN2 and most likely the middle part of the zone, ~21–21.5 Ma. A single sample from Core 313-M0027A-177R (504.78 mbsf) contains few calcareous nannofossils that are not age diagnostic.

A significant change in assemblage occurs in Sample 313-M0027A-179R-2, 10 cm (508.24 mbsf). This sample contains common C. floridanus, as well as frequent H. euphratis and T. carinatus. This sample also contains Helicosphaera recta, which was once used as a marker for the boundary between Zones NP25 and NN1, which approximates the Oligocene/Miocene boundary. This species is now known to occur within the lower Miocene (Perch-Nielsen, 1985), but the combination of assemblage change and occurrence of H. recta suggests that samples from Cores 313-M0027A-179R through 183R (508.24–515.14 mbsf) can be assigned to the lowermost portion of Zone NN1, very near the Oligocene/Miocene boundary. The LO of Sphenolithus ciperoensis (24.75 Ma), which marks the top of Zone NP25 and approximates the top of the Oligocene, occurs in Sample 313-M0027A-186R-1, 34 cm (521.55 mbsf). There is no evidence of a hiatus between the samples assigned to lowermost Zone NN1 and Zone NP25.

The LO of Sphenolithus distentus (27.5 Ma), which marks the base of Zone NP25, is somewhat problematic in this hole. Sphenoliths are not very abundant in these sediments, and moderate preservation makes it difficult to distinguish between S. distentus and S. ciperoensis. A questionable specimen of S. distentus occurs in Sample 313-M0027A-192R-1, 37 cm (539.88 mbsf), whereas S. distentus is definitely present in Sample 313-M0027A-199R-1, 18 cm (554.94 mbsf). Thus, the interval including Cores 313-M0027A-192R through 196R (539.88–549.03 mbsf) is assigned to undifferentiated Zone NP24/NP25. Sediments from Samples 313-M0027A-199R-1, 18 cm, through 218R-2, 103–106 cm (554.94–615.24 mbsf), are assigned to Zone NP24 based on the sporadic co-occurrence of S. distentus and S. ciperoensis. The FO of the latter species marks the base of Zone NP24 at 29.9 Ma.

Below Core 313-M0027A-218R (615.24 mbsf), there appear to be several hiatuses separated by sediments of different ages. These sediments could represent stacked condensed sections formed during periods of low sedimentation rate. Samples from Cores 313-M0027A-220R and 221R (620.80–624.77 mbsf) contain a lower Zone NP23 assemblage based on the absences of S. distentus (FO 30.4 Ma) and Reticulofenestra umbilicus (LO 32.3 Ma). The LO of the latter occurs in Sample 313-M0027A-222R-CC (624.97 mbsf). The presence of a few specimens of R. umbilicus, together with frequent Isthmolithus recurvus (LO 32.46 Ma), suggests that the upper portion of Zone NP22 is missing in this hole. Thus, sediments from Samples 313-M0027A-222R-CC to 223R-1, 26 cm (624.97–625.17 mbsf), are assigned to lower Zone NP22.

The LO of Ericsonia formosa (32.8 Ma), which marks the base of Zone NP22, is found in Sample 313-M0027A-223R-1, 146 cm (626.37 mbsf). Because this species is found in frequent numbers in this sample, the upper portion of Zone NP21 is likely missing in Hole M0027A. A sample from the base of the hole, within Core 313-M0027A-224R (631.09 mbsf), contains a very abundant assemblage characteristic of the Eocene–Oligocene transition (EOT). E. formosa, R. umbilicus, and I. recurvus are much more abundant in this assemblage. The base of Zone NP21 is marked by the LO of Discoaster saipanensis, the last of the rosette Paleogene discoasters. This species does not occur in the sediments of Hole M0027A, although the LO of D. saipanensis (34.2 Ma) occurs a few hundred thousand years prior to the Eocene/Oligocene boundary (33.7 Ma) (Coccioni et al., 2008). Thus, the oldest sediments from this hole are assigned to lower Zone NP21, which spans the Eocene/Oligocene boundary. These sediments could be uppermost Eocene or lowermost Oligocene; further biostratigraphic analyses of calcareous nannofossils and planktonic foraminifers are necessary to further refine this age estimate.

Planktonic foraminifers

A total of 79 samples from Cores 313-M0027A-6H through 224R (13.75–631.15 mbsf) were examined in this study; only samples containing planktonic foraminifers are shown in Figure F36 and Table T5. Primarily core catcher samples obtained during drilling and processed prior to the Onshore Sampling Party (OSP) were picked for planktonic foraminifers, although some additional samples from split cores were washed and picked during the OSP. Planktonic foraminifers indicate that the Miocene section in Hole M0027A extends from at least 213.14 to ~509.19 mbsf between Samples 313-M0027A-73X-CC, 0–3 cm, and 179R-CC, 2–4 cm. The Oligocene occurs between Samples 313-M0027A-179R-CC, 13–15 cm, and 214R-CC, 12–14 cm (509.30–602.01 mbsf). Eocene sediments may occur in the deepest Sample 313-M0027A-224R-CC (631.15 mbsf). Key marker species for identifying the Oligocene/Eocene boundary (e.g., Hantkenina and the Turborotalia cerroazulensis lineage) are absent, so further work is needed to confirm the presence of uppermost Eocene strata.

Planktonic foraminifers are present in low abundances but are well preserved in Hole M0027A. Typical middle Miocene assemblages are present between Samples 313-M0027A-80R-CC and 98R-1, 141–145 cm. The LO of Paragloborotalia mayeri occurs in Sample 313-M0027A-80R-CC, 0–15 cm (227.65 mbsf). This event marks the base of Zone M12/N15 at 11.4 Ma, indicating this sample is at least that old. Sample 313-M0027A-89R-CC, 0–2 cm (255.90 mbsf), contains well-preserved species of Praeorbulina sicana. The LO of this species is at 14.8 Ma and approximates the base of Zone M7/N10. This species continues downcore through Sample 313-M0027A-98R-1, 141–145 cm (281.67 mbsf). The FO of P. sicana marks the base of Zone M5/N8 (16.4 Ma). Another key species is Praeorbulina curva, which is present in Sample 313-M0027A- 89R-CC, 0–2 cm (255.90 mbsf).

The lower Miocene extends from Sample 313-M0027A-101R-3, 34–38 cm (292.76 mbsf), through 179R-CC, 2–4 cm (509.19 mbsf). This interval is characterized by Catapsydrax dissimilis, Fohsella peripheroronda, Globoquadrina baroemoenensis, Catapsydrax unicavus, Globorotalia praescitula, Globigerina angulisuturalis, and Globigerinoides primordius. The LO of C. dissimilis (17.3 Ma) marks the base of Zone M4a/N7 and occurs in Sample 313-M0027A-101R-3, 34–38 cm (292.76 mbsf). A single G. praescitula is found in Sample 313-M0027A-151R-1, 155–160 cm (431.26 mbsf). The FO of this species falls within Zone M3/N6 at 18.5 Ma. G. angulisuturalis is found within Sample 313-M0027A-154R-2, 72–77 cm (441.08 mbsf). The LO of this species occurs at 21.6 Ma, within Zone M1/N4. Paragloborotalia kugleri, a species confined to Zone M1/N4, occurs in Sample 313-M0027A-179R-CC, 2–4 cm (509.19 mbsf). The FO of this species is at 23.8 Ma, indicating that the interval from 441.08 to 509.19 mbsf is dated to 21.6–23.8 Ma.

The FO of G. primordius (26.7 Ma) is found in Sample 313-M0027A-179R-CC, 13–15 cm (509.30 mbsf). This event falls within Zone O6/P22. This sample is also characterized by Paragloborotalia opima nana, a species with a range that extends into the basal Miocene; thus, these sediments are tentatively assigned to the uppermost Oligocene but could range into the lowermost Miocene. Definite Oligocene sediments are found below this sample based on the absence of G. primordius. Paragloborotalia cf. opima opima occurs in Sample 313-M0027A-195R-2, 9–11 cm (549.60 mbsf). No definite specimens of Paragloborotalia opima opima, the LO of which marks the base of Zone O6/P22 at 27.1 Ma, were observed at Site M0027; however, the presence of similar forms suggests this sample may be older than 27.1 Ma. The next biostratigraphically useful taxon found is Globigerina ampliapertura (LO 30.3 Ma), which marks the base of Zone O3/P20. The LO of this species occurs in Sample 313-M0027A-209R-3, 33–36 cm (588.51 mbsf), indicating Zone O2/P19. The interval between Samples 313-M0027A-217R-3, 10–12 cm, and 223R-CC, 18–20 cm (612.76–627.56 mbsf), is barren of planktonic foraminifers.

The LO of Pseudohastigerina spp. (32.0 Ma) marks the base of Zone O2/P19. The last sample examined (Sample 313-M0027A-224R-CC; 631.15 mbsf) contains Pseudohastigerina micra, indicating that the base of the hole is at least lowermost Oligocene Zone O1/P18. The Eocene/Oligocene boundary is correlated using the LO of the genus Hantkenina (33.8 Ma). A secondary marker for this event is the FO of Cassigerinella chipolensis. These species were not observed in Hole M0027A, suggesting that the oldest sediment recovered is lowermost Oligocene. The presence of large, flattened Eocene subbotinids (Subbotina eocaena and Subbotina cryptomphala) could suggest the section is Eocene, although these species could range into the Oligocene. A single Sr isotope age of ~34 Ma suggests an Eocene correlation (see "Chronology"). Analysis of additional samples from the base of the hole is necessary to determine if the section is uppermost Eocene or lowermost Oligocene.

Dinocysts

A total of 47 samples between Samples 313-M0027A-9H-CC and 223R-CC (19.59–627.58 mbsf) were examined for dinocysts (Fig. F37; Table T6). Sample 313-M0027A-9H-CC (19.59 mbsf) is assigned to the Pleistocene on the basis of sparse dinocyst assemblages dominated by Bitectatodinium tepikiense together with Brigantedinium spp., Tectatodinium pellitum, and Selenopemphix nephroides. Sample 313-M0027A-50H-CC (96.12 mbsf) was barren of palynomorphs. The presence of Habibacysta tectata, Labyrinthodinium truncatum modicum, Labyrinthodinium truncatum truncatum, Paleocystodinium golzowense, Trinovantedinium papulum, and Hystrichosphaeropsis obscura constrains the age of Samples 313-M0027A-65X-CC through 67X-CC (195.53–201.22 mbsf) to dinocyst Zones DN5–DN8. Sample 313-M0027A-69X-CC (207.44 mbsf) is assigned an age of late Serravalian to early Tortonian (Zones DN7–DN8; 12.8–8.6 Ma) based on the occurrence of Erymnodinium delectabile together with T. papulum, as well as common Batiacasphaera sphaerica. The occurrence of Apteodinium tectatum, Unipontedinium aquaeductum, Systematophora placacantha, L. truncatum truncatum, and L. truncatum modicum constrains the age of Sample 313-M0027A-91R-CC (262.05 mbsf) to the lower part of Zone DN5 (~15.2–14.2 Ma), around the Langhian/Serravalian boundary.

Sample 313-M0027A-101R-CC (292.91 mbsf) is assigned to Zone DN3 (late Burdigalian; ~18.6–16.8 Ma) based on the occurrence of Lingulodinium multivirgatum, Distatodinium paradoxum, Cousteaudinium aubryae, and Cerebrocysta poulsenii. A sparse assemblage in a terrigenous-dominated slide allows a minimum age of 15.2 Ma (top of Zone DN4) for Samples 313-M0027A-105R-CC and 146R-CC (304.95 and 417.57 mbsf) based on the presence of A. tectatum, C. aubryae, and Pentadinium laticinctum. These samples are thus tentatively assigned to Zone DN3, given the well-constrained age of overlying Sample 313-M0027A-101R-CC (292.91 mbsf). Samples 313-M0027A-149R-CC through 177R-CC (426.71–505.33 mbsf) are assigned to Zone DN2, which spans 22.2–19.1 Ma (late Aquitanian–early Burdigalian) based on the common presence of dinocysts typical of the lower Miocene (e.g., L. multivirgatum, Tityrosphaeridium cantharellum, Cribroperidinium tenuitabulatum, and Cerebrocysta satchelliae). Following de Verteuil and Norris (1996), the presence of Exochosphaeridium insigne suggests an early Burdigalian rather than late Aquitanian age over most of this interval (Samples 313-M0027A-155R-CC through 167R-CC; 445.17–481.60 mbsf), although others have found E. insigne lower in the Burdigalian.

Samples 313-M0027A-185R-CC through 191R-CC (520.96–539.19 mbsf) are assigned to Zone DN1 (latest Chattian–Aquitanian; ~22.2–25.2 Ma), the lower boundary age of SNSM1 from Munsterman and Brinkhuis (2004). Common dinocysts in sediments assigned to Zone DN1 in Hole M0027A are Chiropteridium galea, Deflandrea phosphoritica, Dinopterygium cladoides, Homotryblium floripes, Homotryblium vallum, Glaphrocysta spp., and C. satchelliae. Samples 313-M0027A-192R-CC through 193R-CC (542.48–545.61 mbsf) are assigned to the uppermost Oligocene (Chattian) based on the presence of C. galea and Glaphrocysta spp. together with Distatodinium biffii, as well as Apteodinium australiense, Polysphaeridium zoharyi, and S. placacantha. The presence of genera that do not extend into the Chattian (e.g., Phthanoperidinium, Areosphaeridium, Diphyes, Charlesdowniea, and Rhombodinium) allows Samples 313-M0027A-204R-CC through 220R-CC (573.01–620.83 mbsf) to be assigned to the Rupelian. Based on the absence of Oligocene markers and the presence of Svalbardella cooksonia, Sample 313-M0027A-223R-CC (627.58 mbsf) is tentatively assigned a middle–late Eocene age.

Paleoenvironment

Benthic foraminifers

Benthic foraminifers were examined from 77 (primarily core catcher) samples from Hole M0027A: Samples 313-M0027A-6H-1, 145–150 cm (12.99 mbsf), through 223R-CC (627.96 mbsf). Benthic foraminifer abundances ranged from absent to abundant, and preservation ranged from poor to excellent. Poorly preserved specimens are likely to have been reworked and were not used in paleodepth estimates. The long-term change in paleodepth from the Eocene(?)–Oligocene to the modern seafloor is reflected in the overall shallowing from the outer neritic zone (100–200 m) to the inner neritic zone (0–50 m), with the present water depth at 33.5 m (Fig. F38; Table T7). Benthic foraminifer biofacies changes within this section indicate additional, higher resolution paleodepth variations superimposed on the long-term trend. Barren intervals occur throughout the section and may indicate nearshore/nonmarine environments, substantial downslope transport, or dissolution. It should be noted that the low-resolution shipboard sampling interval did not bracket all lithologic changes and that the sampling interval varied throughout the hole.

Stratigraphic biofacies distributions may be related to substrate (finer grained versus sandier sediments), changes in sediment input, and/or organics/dysoxia, which often correspond to bathymetry. Comparisons in Hole M0027A show good correspondence between sedimentary facies and biofacies, with shallower water biofacies (<50 m) occurring in the sandier intervals of the shoreface–offshore transition (between storm wave base and fair-weather wave base) and deeper water biofacies (50–80 m) occurring in the siltier intervals of the offshore sedimentary facies (deeper than storm wave base). In addition, preliminary results presented here suggest that benthic foraminifer biofacies changes in Hole M0027A indicate that paleobathymetric fluctuations occur within a sequence stratigraphic framework, with several sequences showing a shallowing-upward succession. Detailed higher resolution postcruise studies will elaborate on this.

Samples above Sample 313-M0027A-70X-CC (208.92 mbsf) were barren or contained only one or two specimens of foraminifers; no paleodepth could be determined for these samples (Fig. F38). In and below this (Miocene Samples 313-M0027A-70X-CC, 0–2 cm, to 98R-1, 144–145 cm; 208.92–281.70 mbsf), paleowater depths varied within the inner neritic zone from ~15 to 50 m. These samples are dominated by Nonionella pizarrensis/Nonionella miocenica stella, Hanzawaia concentrica/Hanzawaia hughesi, and Lenticulina spp. (including Lenticulina americana). Samples characterized by abundant H. concentrica/H. hughesi (in the absence of Nonionella) indicate depths of ~10–25 m, whereas samples dominated by N. pizarrensis/N. miocenica stella indicate somewhat greater depths of ~25–50 m. Occasional specimens (typically rare to few) of Bolivina spp., Bulimina mexicana, Buliminella gracilis, Cancris sagra, Cibicides lobatulus, Cibicidoides spp., Fissurina spp., Lagena spp., Pararotalia bassleri, Plectofrondicularia morneyae, Rectuvigerina lamelata, Uvigerina juncea, polymorphinids, and agglutinated benthic foraminifers are found in these samples.

Benthic foraminifer faunas indicate that paleowater depths varied from ~25–50 to ~75–100 m in Miocene Samples 313-M0027A-101R-3, 34–38 cm (292.76 mbsf), through 165R-CC, 5–7 cm (475.81 mbsf) (Fig. F38). Key depth-indicator taxa (Hanzawaia and Nonionella) for the inner neritic zone are discussed above. For the middle neritic zone (50–100 m), B. gracilis and U. juncea are excellent depth indicators and are found throughout this section (Table T7). Samples containing more abundant B. gracilis indicate slightly shallower paleodepths (50–80 m) than samples containing more abundant U. juncea (75–100 m), based on faunal studies from New Jersey coastal plain boreholes (Miller et al., 1997). Other rare to common species found in these Buliminella/Uvigerina–dominated faunas typically include Bolivina spp., Cibicidoides spp., H. concentrica/H. hughesi, Lenticulina spp., Plectofrondicularia spp., Stilostomella spp., and miliolids.

The deepest water benthic foraminifer associations (outer neritic; 100–200 m) were identified below reflector m6 in the Eocene(?)–Oligocene section (Samples 313-M0027A-179R-CC, 13–15 cm, through 223R-CC; 509.30–627.58 mbsf); however, there was significant within-sequence shallowing indicated by faunal changes (Fig. F38). In general, deeper water assemblages are more diverse with more abundant specimens and include taxa such as Anomalinoides spp., Cassidulina spp., Cibicidoides pachyderma, Cibicidoides primulus, Coryphostoma georgiana, Globobulimina auriculata, Gyroidinoides spp., Hanzawaia mantaensis, Melonis barleeanum, Melonis pompilioides, Oridorsalis sp., Plectofrondicularia spp., Pullenia salisburyi, R. lamelata, Siphonina danvellensis, Sphaeroidina bulloides, Trifarina wilcoxensis, polymorphinids, and agglutinated benthic foraminifers. Outer neritic faunas typically include shallower water benthic foraminifer taxa that either range to greater depths or were transported.

Terrestrial palynomorphs and palynofacies

Thirty-one samples from Hole M0027A were analyzed for palynomorphs. Sample spacing was fairly consistent for the lower Miocene and Oligocene sections (approximately one sample every three cores beginning at Core 313-M0027A-146R; 417.57 mbsf). Sample spacing was somewhat greater for the middle Miocene section, with seven samples examined between Samples 313-M0027A-65X-CC and 105R-CC (195.53–304.95 mbsf). Only one sample was examined for Pleistocene sediments. All samples contain numerous pollen grains and other palynomorphs with generally good preservation, with the exception of one sandy sample. In some samples, pollen grains are filled with pyrite, hampering identification and assignment to herbal or arboreal taxa.

Results are discussed according to the age of the sediments: Pleistocene, middle Miocene, early Miocene, Oligocene, and the EOT. Age estimations are based on the Sr-based age model and biostratigraphic results. Percentages of palynomorphs are given with respect to the number of nonsaccate pollen (combined nonsaccate pollen is always 100%).

Pleistocene

One sample (313-M0027A-9H-CC; ~19.59 mbsf) from the Pleistocene was palynologically analyzed. The palynomorph assemblage is characterized by high bisaccate pollen content compared to nonsaccate pollen (Figs. F39, F40). Among the nonsaccate pollen, pollen of deciduous trees is most abundant. Grass, sedge, and herb pollen are also abundant (>15% grass and sedge pollen and >20% herb pollen) (Fig. F40). The sample is also characterized by high percentages of trilete spores, probably of the genus Sphagnum.

Dinocysts are rare in relation to nonsaccate pollen (~17%). Furthermore, the assemblages are dominated by only one cyst type (probably B. tepikiense, generally described as a freshwater and/or meltwater indicator. The amount of foraminifer test linings is very low (<2%). These findings imply that Hole M0027A was probably proximate to the coast during this interval, as higher abundances of foraminifer test linings would be expected in a more distal setting. This is in accordance with the benthic foraminifer–based water-depth reconstruction.

Pollen data imply that deciduous trees (probably deciduous oaks and birches) dominated the New Jersey hinterland during the interval represented by Sample 313-M0027A-9H-CC; however, conifers were widespread and probably also settled in the lowlands and on exposed shelf regions (Fig. F39). These findings indicate that the sample represents an interval of drier and/or cooler conditions compared to samples from the Miocene (see below). This is suggested by the comparatively high percentages of grass, sedge, and herb pollen, indicating vegetation similar to the modern onshore New Jersey coastal plain, which is dominated by mixed pine-oak forests and open vegetation sphagnum bogs/swamps. One sample between 19.59 and 195.53 mbsf was examined and found to be barren of pollen.

Middle Miocene (Serravallian and Langhian)

Four core catcher samples (313-M0027A-65X-CC, 67X-CC, 69X-CC, and 91R-CC; 195.53–262.05 mbsf) were analyzed for palynology and interpreted as middle Miocene (Serravallian and Langhian) based on pollen and dinocysts (Fig. F39). The lowermost sample is placed just below the lower/middle Miocene boundary based on the age-depth plot (see "Chronology"). Bisaccate pollen percentages are very low (~3% for the Serravallian and ~4%–13% for the Langhian) (Fig. F40). Nonsaccate pollen of arboreal taxa—mainly oak pollen—is most frequent and may indicate more extensive oak forests in the New Jersey hinterland. Hickory was probably also very frequent. Grass and herb pollen are rare in middle Miocene sediments, indicating a predominance of forests in the source region. Low percentages of the generally overrepresented bisaccate pollen may indicate that conifers (mainly pines) were only present in areas distant from the sea, probably in mountainous areas (Fig. F39). Climate conditions during the middle Miocene were probably warm and humid. Very low percentages of dinocysts (3%–8%) (Fig. F40) and foraminifer test linings suggest a shorter distance between Hole M0027A and the coastline.

Early Miocene (Burdigalian–Aquitanian)

Eighteen core catcher samples analyzed for palynology (Samples 313-M0027A-101R-CC through 191R-CC; 292.91–539.19 mbsf) (Table T8; Fig. F39) are interpreted as early Miocene (Burdigalian–Aquitanian) based on pollen and dinocysts (Fig. F39). This differs from the placement of the Oligocene/Miocene boundary at ~500 mbsf based on the age-depth plot (Fig. F34) but reflects the fact that the o.5 sequence from 494.87 to 539.5 mbsf straddles the Oligocene–Miocene transition. The uppermost samples from the upper Burdigalian (Fig. F39) are similar to the samples from the Langhian in terms of palynomorph assemblages; however, they show slightly higher percentages of dinocysts and bisaccate pollen, which points to a greater distance between Hole M0027A and the coastline at this time (Fig. F39). Furthermore, conifers were probably still constrained to mountainous areas because, despite the general overrepresentation of bisaccate pollen in the marine record, percentages do not exceed 50% (Fig. F40). The lowlands were probably dominated by hickory-oak forests, as indicated by comparatively high amounts of oak and hickory pollen.

The interval from the lower upper Burdigalian to the lower Aquitanian (~420 to ~540 mbsf) shows strong variations in organic-walled dinocysts and bisaccate pollen, but both palynomorph types increase from younger to older sediments. In light of this, the Aquitanian was probably an interval of greater distance between Hole M0027A and the coastline compared to the Burdigalian and especially the Langhian. The late Aquitanian was further characterized by the presence of different hemlock species, probably indicating moister conditions during this interval. During the lowermost Aquitanian, linden pollen shows high percentages. The vegetation reconstructions described above imply that the climate during the early Miocene was probably warm and humid.

Oligocene

Six samples (313-M0027A-193R-CC through 220R-CC; 545.61–620.83 mbsf) analyzed for pollen were assigned to Oligocene sediments based on pollen and dinocysts, with the lowermost sample close to the EOT (Sample 313-M0027A-220R-CC). Oligocene sediments show an increasing number of hickory and linden-like plant pollen. Bisaccate pollen grains exhibit high percentages (>100%), especially during the Chattian. This could be caused by an increasing distance between Hole M0027A and the shoreline because bisaccate pollen has a very high aeolian transport potential and thus tends to be more overrepresented under more distal conditions. However, it is equally probable that during the middle Oligocene, decreasing temperatures and/or humidity led to a spread of pines and other conifers (Figs. F39, F40). High percentages of herbal taxa (mainly members of Brassicaceae; 5%–22%) suggest decreasing humidity.

Most samples from the Oligocene show relatively low contents of foraminifer test linings compared to the lower Miocene and the ?Eocene (see below). The lowermost two samples show high abundances of dinocysts; however, during the upper Rupelian and the lower Chattian, dinocyst percentages decreased. These findings may point to relatively shallow water depths and a shorter distance between Hole M0027A and the coastline during the middle Oligocene and slightly greater depths and increased distance at the onset of the Oligocene.

?Eocene

The ?Eocene is reflected by only one sample (313-M0027A-223R-CC; 627.58 mbsf) in Hole M0027A. This sample is close to the EOT based on other fossil groups and Sr isotopes, although it could be uppermost Eocene or lowermost Oligocene (see "Chronology" and "Planktonic foraminifers"). The sample is characterized by very high percentages of dinocysts and foraminifer test linings, indicating relatively deep water.

Although percentages of bisaccate pollen are almost equal with percentages of nonsaccate pollen (Figs. F39, F40), considering the overrepresentation of bisaccate pollen in marine pollen records, conifers with bisaccate pollen were probably either rare or grew in distant, mountainous areas (Fig. F39). They were still more abundant than during the Miocene. The New Jersey hinterland was probably dominated by deciduous trees and shrubs. Furthermore, the presence of herb taxa indicates the presence of small open areas or, alternatively, the presence of herb populations (mainly members of Brassicaceae) close to the shoreline. Oaks were probably the most frequent trees/shrubs; however, compared to the Miocene, the percentages of oak pollen are lower. Hickory pollen—although very frequent in samples from the Oligocene—was not found in the ?Eocene sample. Cypress-like taxa, on the other hand, seem to have been more frequent than during the following intervals. Pollen assemblages point to a generally warm and humid climate at that time.

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