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doi:10.2204/iodp.proc.339.105.2013

Biostratigraphy

The microfossil content of sediment recovered at Site U1387 was usually high, with the exception of a dolomite layer in Section 339-U1387C-19R-4 and a few lithified sandstone units (see “Lithostratigraphy”) that could not be disaggregated. The Pleistocene, upper Pliocene, and uppermost Miocene samples (Fig. F25; Table T5) are very rich in planktonic and benthic foraminifers as well as nannofossils. In the Pleistocene sediments, nannofossils, foraminifers, and ostracods are, in general, moderately to well preserved (Tables T6, T7). In the lower Pliocene, however, most of the calcareous microfossils and nannofossils are corroded and fragmented. Furthermore, a mixture of shallow- and deepwater forms characterizes the benthic foraminifer and ostracod assemblages during this period, supporting deposition characteristic of bathyal settings dominated by gravitational, mainly turbiditic episodes (see “Lithostratigraphy”).

Pollen and spores are abundant in the 13 samples analyzed in Holes U1387A and U1387C, ranging from ~4,500 to 32,500 grains/cm³. These values are similar to those found at Site U1386. The preservation of the grains is good to moderate in Hole U1387A (upper 350 mbsf) and very poor in Hole U1387C (350–860 mbsf). In the upper part of Hole U1387C, pollen assemblages are dominated by herbs, mainly Taraxacum-type pollen (Asteraceae and Liguliflorae), whereas corroded conifer pollen dominates the sample at the bottom of the section (Fig. F26).

Common to rare abundances of pteropods were observed in Samples 339-U1387A-1H-CC through 3H-CC (Table T7). All other samples were barren of pteropods. Siliceous microfossils, diatoms, and radiolarians are also present at some levels, such as Samples 339-U1387A-24X-CC, 339-U1387B-24X-CC, and 339-U1387C-29R-CC and 30R-1, 59–60 cm (Tables T7, T8), although diatoms are mainly dissolved and only internal, pyritized molds are preserved.

The sedimentary record recovered at this site was continuous during most of the Pleistocene, but a large hiatus was observed in Core 339-U1387C-19R (Fig. F25; Table T5). Based on the presence of Sphaeroidinellopsis seminulina in Sample 339-U1387C-19R-CC, the hiatus may span from 1.8 to at least 3.19 Ma.

Below the hiatus, early Pliocene and latest Miocene sediments were recovered with ages younger than 6.35 Ma for the bottom of Hole U1387C.

Sedimentation rates are 25 cm/k.y. in the recovered Pleistocene section and 15 cm/k.y. in the Pliocene to latest Miocene sequence.

Calcareous nannofossils

All core catcher samples from Holes U1387A–U1387C were analyzed for calcareous nannofossil biostratigraphy. Additionally, selected samples from Holes U1387A and U1387C were analyzed to constrain biohorizons, paying attention only to marker species. Calcareous nannofossil assemblages are abundant and diverse, and the preservation is good to moderate, with weak dissolution and overgrowth in some samples. Small placolith species (<3 µm) dominate most of the assemblages. Inorganic input and reworking of lower Neogene and Paleogene species vary from few to common throughout all sections (Table T6).

In total, 17 Quaternary and Neogene nannofossil datums defined and/or calibrated by Raffi et al. (2006 and references therein) and Flores et al. (2010) were identified in all holes (Table T5).

The change in abundance of the large Emiliania huxleyi (>4 µm) that characterizes Termination 1 in mid- to low-latitude water masses in the Atlantic Ocean has been proven as a useful event by Flores et al. (2010). This change in abundance was recorded between Samples 339-U1387A-1H-2, 105 cm, and 1H-3, 75 cm (2.55–3.75 mbsf), making it possible to distinguish the onset of the Holocene.

The first occurrence (FO) of E. huxleyi (0.26 Ma), which marks the base of Zone NN21, was placed between Samples 339-U1387A-9X-3, 75 cm, and 9X-4, 75 cm (68.85–70.35 mbsf), and between 339-U1387B-6H-CC and 7X-CC (56.10–64.18 mbsf). However, this event should be taken with caution because of dissolution effects and the low proportion of this species. The last occurrence (LO) of Pseudoemiliania lacunosa (0.46 Ma), considered to be a globally synchronous event that defines the top of Zone NN19, occurred between Samples 339-U1387A-13X-6, 75 cm, and 13X-7, 33 cm (111.75–112.44 mbsf), and between 339-U1387B-11X-CC and 12X-CC (104.11–113.54 mbsf).

A biohorizon considered useful in dating Pleistocene sediments is the LO of Reticulofenestra asanoi (0.90 Ma), which was placed between Samples 339-U1387A-22X-7, 64 cm, and 22X-CC (198.15–199.20 mbsf) and between 339-U1387B-22X-CC and 23X-CC (204.40–214.09 mbsf). The FO of R. asanoi (1.07 Ma), another significant event for the Pleistocene, was recorded between Samples 339-U1387A-29X-2, 65 cm, and 29X-3, 65 cm (257.9–259.4 mbsf), and between 339-U1387B-26X-CC and 27X-CC (242.74–243.54 mbsf). To define these biohorizons, we considered specimens of R. asanoi ≥6 µm in size.

The LO of large Gephyrocapsa spp. (>5.5 µm) (1.24 Ma) was recorded between Samples 339-U1387A-31X-CC and 32X-1, 75 cm (284.81–286.34 mbsf), and between 339-U1387B-30X-CC and 31X-CC (281.30–290.87 mbsf).

The LO of Helicosphaera sellii (1.25 Ma) was identified between Samples 339-U1387A-32X-1, 75 cm, and 32X-1, 75 cm (286.34–287.82 mbsf), and between 339-U1387B-31X-CC and 32X-CC (290.87–300.76 mbsf). This event is considered diachronous (Raffi et al., 1993; Wei, 1993); however, its occurrence at this site is consistent with the ages provided by Raffi et al. (2006) for the Mediterranean Sea when compared with other calibrated events.

The FO of large Gephyrocapsa spp. (>5.5 µm) (1.61 Ma) was identified between Samples 339-U1387C-7R-CC and 8R-CC (346.05–357.52 mbsf). The LO of Calcidiscus macintyrei (1.66 Ma) is defined in the same interval.

Between Samples 339-U1387C-18R-CC and 61R-CC, the succession of events is complex to establish because of potential reworking linked to the presence of several turbidites and slump deposits within all of Hole U1387C.

Between Cores 339-U1387C-18R and 19R, a variation in the composition of calcareous nannofossil assemblages was recorded, characterized by the presence of Discoaster brouweri, Discoaster pentaradiatus, Discoaster surculus, and Discoaster tamalis. The LOs of these species and/or morphotypes occur between 1.90 and 2.8 Ma, allowing us to infer a possible hiatus within Zones NN19 and NN17. However, based on planktonic foraminifer data, the hiatus could be extended at least until 3.19 Ma because of the presence of S. seminulina (Table T5). Core 339-U1387C-19R is characterized by the presence of a dolomite-rich layer and, for most of its length, by the absence of calcareous nannofossil assemblages.

The lower portion of Hole U1387C was analyzed by selecting intervals with predominantly fine-grained sediment and trying to avoid possible turbidites and slumps (see “Lithostratigraphy”). The LO of Sphenolithus spp. (3.7 Ma) and Reticulofenestra pseudoumbilicus >7 µm (3.83 ma), marker species of Zone NN14–NN15, was recorded between Samples 339-U1387C-31R-CC and 33R-CC (573.59–597.01 mbsf). The LO of Amaurolithus primus (4.5 Ma) was recorded between Samples 339-U1387C-39R-CC and 40R-5, 91 cm (650.36–661.21 mbsf). This last event should, however, be taken with caution because of the low proportion of this species.

The deepest portion of Hole U1387C is characterized mainly by undisturbed hemipelagic deposits (nannofossil mud to nannofossil ooze; see “Lithostratigraphy”) allowing the approximation of the LO of Discoaster quinqueramus (Zone NN11–NN12; 5.54 Ma) between Samples 339-U1387C-55R-CC and 56R-7 (805.68–817.18). This bioevent is placed in the uppermost Miocene, close to the Miocene/Pliocene boundary. Below this interval, the presence of assemblages composed mainly of Discoaster berggrenii, D. quinqueramus, and Discoaster variabilis was recorded. For the deepest portion of the hole, the sparse presence of both Amaurolithus primus and Amaurolithus delicatus, as well as common specimens of Reticulofenestra rotaria and dominance of small placoliths of Reticulofenestra minuta against Reticulofenestra haqii/minutula morphotypes (Young, 1998; Flores and Sierro, 1987), suggest a Messinian age.

Planktonic foraminifers

Planktonic foraminifers are dominant in the Pleistocene samples from all three holes (Tables T7, T8), with the exception of Sample 339-U1387B-34X-CC. In the Pliocene to latest Miocene samples, abundance varies between rare and dominant. Preservation is generally moderate to very good, but in several samples, especially in the Pliocene, poor preservation was observed.

The Pleistocene assemblages are typical of temperate waters from the North Atlantic with a mixture of surface- and deep-dwelling foraminifers. Globigerina bulloides, Neogloboquadrina pachyderma (dextral), and Globorotalia inflata are the dominant species, with Globorotalia truncatulinoides, Globorotalia scitula, Globorotalia crassaformis, and occasionally Globorotalia hirsuta also contributing to the deep-dwelling fauna.

In the Pliocene to late Miocene samples, subtropical to tropical species such as Globigerinoides trilobus, Globigerina apertura, Globigerina decoraperta, and Globigerinoides extremus are common. In addition, Sphaeroidinellopsis subdehiscens and S. seminulina were observed in several samples from Hole U1387C (Table T8). Specimens of Sphaeroidinellopsis kochi were detected in Samples 339-U1387C-59R-CC and 60R-CC. Globorotalia menardii seldom occurs. Rare specimens of Globorotalia conomiozea and Globorotalia miotumida were observed between Samples 339-U1387C-57R-CC and 61R-1, 0–3 cm. A reworked specimen of Globorotalia plesiotumida was found in Sample 49R-CC.

N. pachyderma (sinistral) was regularly observed but in low numbers during the middle to late Pliocene. Neogloboquadrina atlantica (dextral) was found in samples from the mid-Pleistocene (see below for details) and Neogloboquadrina atlantica (sinistral) in samples from Cores 339-U1387C-57R through 59R (Table T8). Neogloboquadrina humerosa specimens, on the other hand, were observed between Samples 339-U1387C-58R-CC and 61R-CC.

The planktonic foraminifer biostratigraphy at Site U1387 is based on nine events (Table T5). The top of the paracme of N. pachyderma (sinistral), (1.21 Ma; Lourens et al., 2004), was placed between Samples 339-U1387A-31X-CC and 32X-CC (284.81–295.29 mbsf) and between 339-U1387B-30X-CC and 31X-CC (281.35–290.87 mbsf). The bottom of the paracme of N. pachyderma (sinistral) (1.37 Ma; Lourens et al., 2004) was observed between Samples 339-U1387B-34X-CC and 36X-CC (319.42–337.99 mbsf) and probably also reached with the lowermost sample in Hole U1387A (i.e., Sample 339-U1387A-38X-CC).

As at the previous sites, N. atlantica (dextral) was observed in samples from the mid-Pleistocene in all three holes: Samples 339-U1387A-33X-CC through 38X-CC (305.05–352.75 mbsf), 339-U1387B-33X-CC through 36X-CC (310.17–337.99 mbsf), continuously between 339-U1387C-2R-CC and 19R-2, 46–48 cm (299.59–454.98 mbsf), and with a single specimen in 339-U1387C-19R-3, 99 cm, and 19R-CC (458.54–458.59 mbsf).

The FO of Globorotalia inflata (2.09 Ma; Lourens et al., 2004) was placed between Samples 339-U1387C-19R-3, 20–22 cm, and 19R-CC (456.22–458.59 mbsf), coinciding with a dolomite-rich layer and the above-mentioned hiatus. At the same level, the LO of Globorotalia puncticulata (2.41 Ma; Hilgen, 1991; Lourens et al., 2004) was identified.

Observation of Pliocene events is restricted to Hole U1387C, where discrete samples within specific cores were studied in addition to core catcher samples (Table T8). The LO of S. seminulina (3.19 Ma) was also observed between Samples 339-U1387C-19R-3, 20–22 cm, and 19R-CC (456.22–458.59 mbsf), coinciding with the FO of G. inflata and the LO of G. puncticulata. The co-occurrence of the three aforementioned events with ages from 2.09 to 3.19 Ma together with the recognized nannofossil bioevents indicates a range of 1.9 Ma to at least 3.19 Ma for the hiatus recognized in Core 339-U1387C-19R.

The temporal disappearance of G. puncticulata (3.57 Ma; Lourens et al., 2004) was identified between Samples 339-U1387C-26R-1, 57–59 cm, and 25R-CC (520.24–520.49 mbsf). The reappearance of this species (3.31 Ma) was placed between Samples 22R-CC and 23R-1, 59–61 cm (489.75–492.01 mbsf).

The LO of Globorotalia margaritae (3.8 Ma; Lourens et al. 2004), was recorded between Samples 339-U1387C-30R-3, 58–59 cm, and 30R-1, 59–60 cm (558.90–561.89 mbsf). Because the last abundant occurrence of G. margaritae (3.98 Ma) coincides with slumped sediments in Core 339-U1387C-34R (see “Lithostratigraphy”), we did not define this event at this site.

The FO of G. puncticulata (4.52 Ma; Lourens et al., 2004), was observed between Samples 339-U1387C-37R-3, 60–62 cm, and 37R-5, 100–102 cm (629.12–632.52 mbsf).

The absence of G. miotumida and the presence of G. margaritae at the bottom of this site indicate an age younger than 6.35 Ma for the base of Hole U1387C.

Benthic foraminifers

In Hole U1387A, every second sample between Samples 339-U1387A-1H-CC and 36X-CC was studied for the abundance of benthic foraminifers (Table T9). The assemblages were expected to resemble those of Site U1386. For Hole U1387C, every second core catcher sample was analyzed between Samples 339-U1387C-2R-CC and 28R-CC. Beginning with Sample 29R-CC, all available core catcher samples were included in the analysis. Additionally, selected core catcher samples from Hole U1386B were examined for the “Stilostomella extinction” event. The combined information from all studied samples documents the entire succession recovered at Site U1387.

Abundance and preservation of benthic foraminifers are related to grain size and depositional environment. In the contouritic portions of Hole U1387A (Samples 1H-CC through 36X-CC) and Hole U1387C (Samples 2R-CC through 13R-CC), benthic foraminifers are abundant and preservation is generally good. Within the dolomite horizon and with the occurrence of turbidite deposition in Core 339-U1387C-19R (see “Lithostratigraphy”), the abundant benthic foraminiferal tests are moderately to poorly preserved. Between Samples 339-U1387C-55R-CC and 61R-CC, preservation improves and well-preserved assemblages are found.

Similar to preservation, the composition of the benthic foraminiferal assemblages shows a relation to lithofacies (see “Lithostratigraphy”). Most of the assemblages in the nannofossil ooze and silty mud (Samples 339-U1387A-1H-CC through 36X-CC and 339-U1387C-2R-CC through 18R-CC) consist of species of Brizalina, Bulimina, Cassidulina, Globobulimina, Melonis, Sphaeroidina, and Uvigerina in varying proportions. These taxa characterize upper bathyal environments with increased organic matter flux and reduced ventilation (van Morkhoven et al., 1986; Leckie and Olson, 2003; Murray, 2006). Peak abundances of Brizalina spp. indicate peaks in oxygen depletion of bottom water related to enhanced input of organic matter and/or a well-stratified water column. Transport from the shelf was low, as related taxa occur rarely in the assemblages.

In contrast, Samples 339-U1387A-13X-CC through 19X-CC reveal assemblages primarily composed of Cibicidoides pachyderma and Uvigerina spp., whereas low-oxygen indicators like Brizalina spp. occur sporadically. These assemblages indicate an episode of increased ventilation, which is potentially related to an increase in the intensity of the upper core of MOW. The “epibenthos group,” suggested as an indicator for MOW intensity in the area (Schönfeld, 1997, 2002; Schönfeld and Zahn, 2000), shows abundances of >5% in this interval, whereas it is less common in the rest of Hole U1387A.

Hyalinea balthica, an indicator for cold-water masses (Bayliss, 1969; van Morkhoven et al., 1986), is only abundant in Samples 339-U1387A-3H-CC and 24X-CC and 339-U1387C-3R-CC. As observed at Site U1386, this taxon occurs only sporadically below the MPR marker horizon in the seismic profiles (Llave et al., 2001, 2011; Roque et al., 2012) and disappears below Sample 339-U1387C-7R-CC.

Similar to Site U1386, Cassidulina laevigata/teretis, commonly occurring in boreal waters of the North Atlantic during the middle–late Pliocene and the Pleistocene, virtually disappears below Sample 339-U1387C-19R-CC.

The cored portion from Sample 339-U1387C-19R-CC to 43R-CC shows a pattern of alternating assemblages primarily consisting of (1) upper bathyal assemblages characterized by varying amounts of Brizalina, Bulimina, Melonis, Siphonodosaria, and Uvigerina similar to the nannofossil ooze and (2) shelf species of Ammonia, Asterigerinata, and Elphidium. The often abraded and broken foraminiferal shells of the later assemblages indicate downslope transport, which is consistent with the sedimentological observations (see “Lithostratigraphy”). Within the assemblages dominated by shelf taxa, a further distinction can be drawn that corresponds well to lithofacies and potentially indicates different sources for the transported sediments. Whereas the core catcher samples from the turbiditic sediment (Samples 339-U1387C-19R-CC through 33R-CC) reveal middle–outer shelf species of Elphidium and Asterigerinata as main components, the inner shelf taxon Ammonia occurs frequently only in the interval of convolute bedding (Samples 38R-CC through 43R-CC).

Benthic foraminiferal assemblages between Samples 339-U1387C-44R-CC and 52R-CC are mainly composed of the shelf taxa Ammonia, Elphidium, and Asterigerinata, as well as cibicids. In particular, Samples 47R-CC through 51R-CC reveal the highest abundances of Cibicides lobatulus in the succession. Together with scarce deepwater taxa, the assemblages imply downslope transport as well as increased ventilation and/or current strength (Schönfeld, 1997).

A shallowing trend and/or a first phase of tectonically driven sediment transport are implied for the lowest part of Hole U1387C. Beginning with Samples 339-U1387C-60R-CC and 61R-CC, the occurrences of Cibicidoides wuellerstorfi and Laticarinina pauperata indicate middle bathyal to abyssal environments (van Morkhoven et al., 1986). These associations are followed by upper bathyal assemblages consisting of Brizalina, Uvigerina, and stilostomellids that finally pass into assemblages increasingly affected by downslope transport with Uvigerina, Cibicidoides, Elphidium, and Ammonia (Samples 339-U1387C-54R-CC through 52R-CC).

The Stilostomella extinction (0.58–0.7 Ma) (Hayward, 2002; Kawagata et al., 2005) was recognized between Samples 339-U1387A-14X-CC and 15X-CC (122.99–132.43 mbsf) as well as in Samples 339-U1387B-13X-CC and 14X-CC (122.45–132.51 mbsf). The datum agrees well with the age estimates from nannoplankton assemblages (Fig. F25). Similar to Site U1386, nodosariids, pleurostomellids, and stilostomellids are rare at this depth interval, and only a few tests have been identified. Frequent occurrences of these foraminiferal groups are recorded from below Sample 339-U1387A-33X-CC.

Ostracods

Ostracods were examined in most core catcher samples from Hole U1387A and selected core catcher samples from Hole U1387C to provide a low-resolution record of the entire stratigraphic section recovered at Site U1387 (0–865 mbsf), which extends from the Holocene to the latest Miocene (Fig. F25). In general, ostracod abundance decreases with increasing depth, but it varies significantly throughout the record, with lowest abundances recorded from ~865 to 350 mbsf. Highest concentrations are observed in the upper 350 mbsf, a section that is distinguished by contourite deposition and good preservation of both benthic foraminifers and ostracods. A marked abundance peak is observed at ~170 mbsf, which corresponds to ~0.72 Ma according to calcareous nannofossils and planktonic foraminifer biostratigraphy.

The ostracod assemblage found at Site U1387 is similar to that observed at Site U1386 and includes >70 species typical of the inner shelf to upper slope facies (Table T10). Species diversity, however, is underestimated because species of selected genera (i.e., Krithe, Cytheropteron, etc.) were grouped to facilitate the shipboard preliminary study. The most common genera are Krithe, Henryhowella, Cytheropteron, Argilloecia, and Cytherella, with lesser contributions by Buntonia, Parakrithe, Aurila, and Urocythereis.

Four main ostracod assemblages were distinguished based on the stratigraphic distribution of the different taxa. Assemblage A is characterized by Krithe spp., Argilloecia acuminata, Cytheropteron spp., Paracytherois productum, Paramacrocypris arcuata, and Pseudocythere caudata. This assemblage is present during three intervals in the record: in the upper 220 mbsf, between 315 and 420 mbsf, and between 820 and 850 mbsf. These taxa characterize upper bathyal environments with increased organic matter flux and reduced ventilation (Cronin, 1983; Ruiz et al., 2008; Alvarez Zarikian et al., 2009).

Assemblage B, characterized by ostracods typical of bathyal environments and enhanced ventilation (Didié and Bauch, 2000; Ruiz et al., 2008; Alvarez Zarikian et al., 2009), dominates at the base of Hole U1387C (~840–865 mbsf), from ~670 to 480 mbsf (except a short interval between ~570 and 600 mbsf, see below), and from 345 to 215 mbsf. This assemblage includes Henryhowella sarsii, Cytherella spp., Monoceratina mediterranea, Neonesidea mediterranea, Paijenborchella malajensis cymbula, Parakrithe dimorpha, and Bradleya dictyon.

Assemblage C is present in the upper 350 mbsf at Site U1387, and its proportion increases to >50% in Samples 339-U1387B-1H-CC and 2H-CC (8–15 mbsf). Assemblage C includes Buntonia dertonensis, Buntonia sublatissima, Rectobuntonia inflata, Buntonia textilis, Loxoconcha multifora, and Pterigocythereis jonesii. Today, the majority of these species lives between 75 and 250 mbsl in the Mediterranean Sea (Bonaduce et al., 1975; Yassini, 1979; Ruiz and Gonzalez-Regalado, 1996) and may indicate a change in bottom water environmental conditions possibly related to bathymetric reduction in the Gulf of Cádiz at this time.

Assemblage D consists of typical shallow-water, inner-shelf taxa Aurila spp., Callistocythere spp., Loxoconcha rhomboidea, Urocythereis spp., and Ruggieria longecarenata (Ruiz et al., 2008). This assemblage was observed only in Samples 339-U1387C-31R-CC through 33R-CC and from 41R-CC to 54R-CC, but their preservation is poor and most specimens are fragmented. These samples correspond to debrite and turbidite layers (see “Lithostratigraphy”) of early Pliocene age, and the presence of shallow-water ostracods in these sediments imply reworking by gravity and/or lateral flow. The paleonvironmental interpretation derived from the ostracod fauna is in agreement with that derived from benthic foraminifers at this site.

Palynology

Five samples from Hole U1387A (1H-CC, 10X-CC, 20X-CC, 29X-CC, and 37X-CC) and eight samples from Hole U1387C (7R-CC, 10R-CC, 19R-CC, 21R-CC, 24R-CC, 35R-CC, 48R-CC, and 61R-CC) were analyzed. The lithology of the four uppermost samples in Hole U1387A is dominated by mud (silty mud and nannofossil mud). In contrast, the sample at the base of Hole U1387A is different, formed by silty sand (see “Lithostratigraphy”). Pinus is well represented in the upper 350 m of the sequence, with the maximum abundance at the top (Fig. F26; Table T11). It is almost absent in all the samples from Hole U1387C, although some of the corroded pollen of conifers likely belong to the Pinus genus.

In Hole U1387A, the pollen assemblages in Samples 339-U1387A-1H-CC, 10X-CC, 20X-CC, and 29X-CC, covering the last 1 m.y., are characterized by assemblages from the Mediterranean forest, mainly deciduous and evergreen Quercus and Olea, semidesert environments (Artemisia, Ephedra, and Chenopodiaceae/Amaranthaceae), and grasslands, mainly Taraxacum-type and Poaceae, similar to the composition found in the contemporaneous levels of the previous sites (see “Biostratigraphy” in the “Site U1385” chapter [Expedition 339 Scientists, 2013c] and “Biostratigraphy” in the “Site U1386” chapter [Expedition 339 Scientists, 2013d]). In contrast, the silty sand sample at the bottom of Hole U1387A-37X-CC, dated close to 1.6 Ma, contains two distinct assemblages, one composed of well-preserved tree pollen grains (deciduous and evergreen Quercus, Olea, Carpinus orientalis/Ostrya, Ulmus/Zelkova, and Taxodiaceae/Cupressaceae) and the other characterized by corroded pollen grains, mainly Taraxacum-type and conifers, suggesting two different sources of pollen grains. Well-preserved tree pollen might be transported by a river plume from the adjacent landmass of southern Iberia, whereas the corroded pollen and the associated coarse–grain size sediments might be the result of reworked material caused by downslope or alongslope flow (see “Lithostratigraphy”).

In Hole U1387C, all analyzed samples are composed of light (greenish gray nannofossil mud) and dark (very dark greenish gray mud with biogenic carbonates) mud (see “Lithostratigraphy”) dated older than 1.61 Ma (Table T5). Pollen grains are poorly preserved, and the unidentifiable/total pollen and spores ratios are the highest of the sequence. Samples 339-U1387C-7R-CC, 10R-CC, 19R-CC, 21R-CC, 24R-CC, and 35R-CC are dominated by Taraxacum-type, a pollen that is very resistant to corrosion and, additionally, easily to identify when damaged. This pollen morphotype is commonly overrepresented in poorly preserved pollen assemblages (e.g., Sánchez Goñi, 1994). In contrast, Samples 339-U1387C-48R-CC and 61R-CC are dominated by corroded pollen grains of conifers. High proportions of unidentifiable conifer pollen are a common feature in Pliocene and Miocene sequences of southern Iberia (Jiménez-Moreno et al., 2010). The fact that no well-preserved pollen assemblages are recorded in sediments older than 1.6 Ma could indicate a different regional geomorphological configuration at that time that precluded any direct arrival of pollen from the local vegetation of the close continent.

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