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doi:10.2204/iodp.proc.324.107.2010

Paleontology

Sediments recovered from Site U1350 include several pieces of red and black chert (Cores 324-U1350A-1W to 9R; Unit I and Subunit IIa; see "Sedimentology"). Discrete chert pieces found in the Subunit IIa basalts are most likely displaced from the upper levels by rotary core barrel (RCB) drilling. Shipboard calcareous microfossil studies were performed on limestones that encrusted cherts. In addition, numerous intercalated pelagic limestones between pillow lavas in Unit IV (Cores 25R and 26R) were also investigated.

Calcareous nannofossils from Unit I and Subunit IIa are frequent to high in abundance and moderately to poorly preserved. As a whole, the assemblage is indicative of Early Cretaceous age (Hauterivian–Albian). Planktonic and benthic foraminifers are almost barren in these two units, with only a few silica-replaced specimens. Interpillow pelagic limestones of Unit IV are severely recrystallized and do not yield any calcareous microfossils. A low-diversity, poorly preserved radiolarian assemblage is present in the foraminiferal samples of Site U1350.

Calcareous nannofossils

The calcareous nannofossils in the chert-encrusting limestones from Site U1350 (Unit I and Subunit IIa) are frequent to abundant and moderately to poorly preserved. The sediments recovered below this interval are barren of calcareous nannofossils.

Sample 324-U1350A-1W-1, 5–6 cm, contains Eprolithus floralis, Staurolithites siesseri, and Zeugrhabdotus diplogramus (Table T2), which allows assignment to Zone NC8 (Albian). The occurrence of Cretarhabdus striatus and Cruciellipsis cuvillieri together with Haqius curcumradiatus and S. sisseri in Sample 324-U1350A-1W-1, 9–10 cm, immediately below, implies a mixture of calcareous nannofossil taxa of the Lower to mid-Cretaceous (Hauterivian–Albian) (Table T2). An almost identical nannofossil assemblage is recorded from Sample 324-U1350A-3R-1, 5–6 cm. Beneath, Sample 324-U1350A-4R-1, 18–19 cm, contains C. cuvillieri, Rotelapillius crenulatus, and Speetonia sp., which point to Zone NC4 (Hauterivian).

The calcareous nannofossils from Samples 324-U1350A-6R-1, 10–11 cm, and 8R-1 (Piece 1, 2–4 cm), both derived from discrete chert pieces that are most likely displaced from upper sediments, indicate the Berriasian to Albian by the presence of Rhagodiscus asper and Staurolithites crux. Sample 324-U1350A-9R-1 (Piece 2, 10–11 cm) illustrates a mixed assemblage of the Lower to mid-Cretaceous by the presence of Axopodorhabdus albianus, C. cuvillieri, Rhagodiscus angustus, and Zeugrhabdotus erectus.

In summary, the age of studied Unit I and Subunit IIa is most likely the Berriasian to Albian

Foraminifers

Both planktonic and benthic foraminifers are nearly barren in the chert-encrusting limestones in Unit I and Subunit IIa. Individuals encountered are one hedbergellid specimen (planktonic foraminifer; Sample 324-U1350A-1W-1, 9–10 cm) and one Dorothia specimen (benthic foraminifer; Sample 324-U1350A-5R-1, 4–5 cm), both of which are replaced by silica and give no information on age or paleowater depth. Likewise, no foraminifer specimen was retrieved from intercalated pelagic limestones between pillow lavas in Unit IV (Cores 324-U1350A-25R through 26R).

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