Beschreibung: The dataset compiles reconstructed changes in bottom water temperature and global ice volume from 0 to 17 Ma using δ18O in conjunction with Mg/Ca records of the infaunal benthic foraminifer, O. umbonatus from Ocean Drilling Program (ODP) Site 130-806 (equatorial Pacific; ~2500 m). This dataset covers the middle Miocene to present (17-0 Ma) and has an average temporal resolution of ~0.2 Ma. Application of the new equations to the Site 130-806 record leads to the suggestion that global ice volume was greater than today after the Middle Miocene Climate Transition (~14 Ma). ODP Site 130-806 bottom waters cooled and freshened as the Pacific zonal sea surface temperature gradient increased, and climate cooled through the Pliocene, prior to the Plio‐Pleistocene glaciation of the Northern Hemisphere.

Beschreibung: The Middle Eocene Climatic Optimum (MECO) at ca. 40 Ma is one of the largest of the transient Eocene global warming events. However, it is relatively poorly known from tropical settings since few sites span the entirety of the MECO event and/or host calcareous microfossils, which are the dominant proxy carrier for palaeoceanographic reconstructions. Ocean Drilling Program (ODP) Pacific Ocean Site 143-865 in the low-latitude North Pacific (Allison Guyot) has the potential to provide a useful tropical MECO reference but detailed stratigraphic and chronological constraints needed to evaluate its completeness were previously lacking. We have addressed this deficit by generating new high-resolution biostratigraphic, stable isotope and X-ray fluorescence (XRF) records spanning the MECO interval (~38.0-43.0 Ma) in two holes drilled at Site 143-865. XRF-derived strontium/calcium (Sr/Ca) and barium/strontium (Ba/Sr) ratio and Fe count records allow correlation between holes and reveal pronounced rhythmicity, enabling us to develop the first composite section for Holes 143-865B and 143-865C and a preliminary cyclostratigraphy for the MECO. Using this new framework, the sedimentary record is interpreted to be continuous across the event, as identified by a pronounced transient benthic foraminiferal δ¹⁸O shift of ~0.8‰. Calcareous microfossil biostratigraphic events from widely used zonation schemes are recognized, with generally good agreement between the two holes, highlighting the robustness of the new composite section and allowing us to identify planktic foraminiferal Zones E10-E15 and calcareous nannofossil Zones NP15-18. However, discrepancies in the relative position and ordering of several primary and secondary bioevents with respect to published schemes are noted. Specifically, the stratigraphic highest occurrences of planktic foraminifera Acarinina bullbrooki, Guembelitrioides nuttalli, and Morozovella aragonensis, and calcareous nannofossils Chiasmolithus solitus and Sphenolithus furcatolithoides and the lowest occurrence of Reticulofenestra reticulata, all appear higher in the section than would be predicted relative to other bioevents. We also note conspicuous reworking of older microfossils (from planktic foraminiferal Zones E5-E9 and E13) into younger sediments (planktic foraminiferal Zones E14-15) within our study interval consistent with reworking above the MECO interval. Regardless of reworking, the high-quality XRF records enable decimeter scale correlation between holes and highlight the potential of Site 143-865 for constraining tropical environmental and biotic changes, not just across the MECO but also throughout the Paleocene and early-to-middle Eocene interval.

Beschreibung: The oxygen isotopic composition of benthic foraminifera (d18Ob) is widely used to date and correlate marine sediment sequences. However, d18Ob has found comparatively little use in the Arctic Ocean due both to uncertainty in Arctic marine sediment chronology and the lack of resemblance between Arctic and open ocean d18Ob records. We address this issue by combining Arctic d18Ob records (Cronin et al., 2019) with benthic ostracode Mg/Ca-BWT reconstructions (Cronin et al., 2017) to create a composite record of the history of seawater d18O in the intermediate-to-deep Arctic Ocean over the last 600 kyr. Seawater d18O and its uncertainty was calculated using PSU Solver (Thirumalai et al., 2016).

Beschreibung: A representative split of 356 washed samples (〉38µm) was analysed for foraminifera size. Size parameters of randomly oriented foraminifers were measured using a Malvern Mastersizer laser granulameter. The maximum diameter of the object was chosen as the most suitable size estimator because it is least affected by random orientation. The 90th percentile of the maximum diameter (or D90) was used to describe these strongly skewed distributions.

Beschreibung: Core samples were washed over a 38µm sieve and dried in an oven at 40°C. Planktic foraminifera species and genera abundance counts were made on 49 samples.

Beschreibung: The Eocene-Oligocene transition (EOT, ~34 Ma) is marked by changes in calcareous nannofossil assemblages and coincides with variations in sea-surface temperature and nutrient availability. During the EOT, calcareous nannofossil assemblages underwent an abrupt turnover with a permanent decline of warm-oligotrophic taxa, a decrease in species diversity and a remarkable increase in eutrophic taxa. Here, we combined calcareous nannofossil and planktonic foraminifera biostratigraphy from ODP Hole 756C (Ninetyeast Ridge, Indian Ocean), as well as new benthic foraminifera and bulk sediment stable isotope (C, O) records, which documents ocean-climate changes and provides independent chemostratigraphy. Our results provide further support to previous records documenting an invigorated Southern Ocean circulation associated with the transport of cooler and nutrient-enriched waters toward low-middle latitudes.