English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

. The Middle Eocene Climatic Optimum (MECO) at ca. 40 Ma is one of the largest ofthe transient Eocene global warming events. However, it is relatively poorlyknown from tropical settings since few sites span the entirety of the MECOevent and/or host calcareous microfossils, which are the dominant proxycarrier for palaeoceanographic reconstructions. Ocean Drilling Program (ODP)Pacific Ocean Site 865 in the low-latitude North Pacific (Allison Guyot) hasthe potential to provide a useful tropical MECO reference, but detailedstratigraphic and chronological constraints needed to evaluate itscompleteness were previously lacking. We have addressed this deficit bygenerating new high-resolution biostratigraphic, stable isotope, and X-rayfluorescence (XRF) records spanning the MECO interval (∼38.0–43.0 Ma) in two holes drilled at Site 865. XRF-derivedstrontium ∕ calcium (Sr∕Ca) and barium ∕ strontium (Ba∕Sr) ratios and Fe countrecords allow correlation between holes and reveal pronounced rhythmicity,enabling us to develop the first composite section for Holes 865B and 865Cand a preliminary cyclostratigraphy for the MECO. Using this new framework,the sedimentary record is interpreted to be continuous across the event, asidentified by a pronounced transient benthic foraminiferal δ18Oshift of ∼0.8 ‰. Calcareous microfossilbiostratigraphic events from widely used zonation schemes are recognized,with generally good agreement between the two holes, highlighting therobustness of the new composite section and allowing us to identify plankticforaminiferal Zones E10–E15 and calcareous nannofossil Zones NP15–18.However, discrepancies in the relative position and ordering of severalprimary 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 ofReticulofenestra reticulata all appear higher in the section than would be predicted relative to otherbioevents. We also note conspicuous reworking of older microfossils (fromplanktic foraminiferal Zones E5–E9 and E13) into younger sediments(planktic foraminiferal Zones E14–15) within our study interval consistentwith reworking above the MECO interval. Regardless of reworking, thehigh-quality XRF records enable decimetre-scale correlation between holesand highlight the potential of Site 865 for constraining tropicalenvironmental and biotic changes, not just across the MECO but alsothroughout the Palaeocene and early-to-middle Eocene interval.

New composite bio- and isotope stratigraphies spanning the Middle Eocene Climatic Optimum at tropical ODP Site 865 in the Pacific Ocean