T212 Cushman Foundation Symposium: Hothouse to Coldhouse Transitions at Southern High Paleolatitudes during the Cretaceous and Cenozoic

Tuesday, 6 November 2018
1:30 PM - 5:30 PM
Room 140

HIGH SOUTHERN LATITUDE RECORD OF CRETACEOUS OCEAN ANOXIC EVENT (OAE) IN THE HIKURANGI PLATEAU (SOUTHWEST PACIFIC)

Paper number: T212-9
Program: Technical Sessions
Time: 3:30 PM – 3:45 PM

Authors

Abstract

Deep-sea records of Ocean Anoxic Events (OAEs) are relatively rare, especially within the high southern latitudes. Consequently, their occurrence is valuable to our interpretation of the paleoceanographic evolution of our planet during global climatic shifts due to their heightened sensitivity to seawater chemical and temperature perturbations.

During International Ocean Discovery Program (IODP) Expedition 375, Site U1520 penetrated the sedimentary cover of the incoming Pacific Plate on the Hikurangi Subduction Margin (HSM) to 1045.75 mbsf. Included in this record are ~30 m (15.45 m recovered) of dark grey clayey siltstones and organic-rich mudstones interbedded with volcanoclastic conglomerates of late Cenomanian-early Turonian age.

Shipboard investigation of these lithologies revealed heightened Total Organic Carbon (TOC) values varying from ~4-14%. Our evidence infers that the section preserved at this site records the first occurrence of OAE2 within the HSM, illustrating the environmental perturbations through an OAE from a high southern paleolatitude (~70-80° S) site proximal to the Cretaceous Antarctic mainland.

We investigated the foraminiferal, calcareous nannofossil, radiolarian and geochemical record preserved within the HSM to document the environmental stresses and paleoceanographic mechanisms driving the observed shifts of the microfossil communities within this high-southern latitude marine setting. Foraminifer assemblage analyses reveal variably preserved populations of rare foraminifers, suggesting fluctuating environmental conditions recorded throughout the section. Planktonic foraminiferal diversity and abundance remains relatively low, composed primarily of muricohedbergellids. As well as TOC and faunal analysis, this investigation details high resolution benthic foraminiferal, and bulk isotopic analysis (δ18O and δ13C) through the OAE, detailing the localised environmental perturbations and their relationship with similar high latitude sites.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-320606

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