T169 Oceans and Climates through Earth History: From Proxy Reconstructions to Model Assessments (Posters)

Tuesday, 11 October 2022
9:00 AM - 1:00 PM
Exhibit Hall F

INVESTIGATING THE SEDIMENTOLOGICAL CHANGES DURING THE EARLY PLEISTOCENE ON THE CHILEAN CONTINENTAL SHELF SOUTH OF THE FALKLAND ISLANDS

Paper number: T169-24
Program: Technical Sessions
Time: 9:00 AM – 1:00 PM

Authors

Abstract

The International Ocean Discovery Program (IODP) Site U1534 is located south of the Falkland Islands in the thickest part of a contourite drift off the Chilean shelf. Due to its strategic location, the site has a high sedimentation accumulation rate that can be used to reconstruct past climates. One of the most recent and important gradual changes in Earth’s recent climate record was the Pliocene-Pleistocene Transition (LP/EP). Between 3 and 0.77 million years ago (MYA), the Earth's global climate cooled by approximately 2-3°C, marking the beginning of our current glacial period. Paleoclimate experts theorize that this global cooling was caused by Earth’s three orbital Milankovitch cycles: eccentricity, obliquity, and precession. Although climate models indicate a strong correlation between eccentricity and obliquity with climate, past studies of the δ18O record collected from deep-sea sediment cores show conflicting results on the link between precession and Plio-Pleistocene cooling.

Our research will continue to investigate this question by using a combination of shipboard data and weight percentages of ice rafted detritus (IRD) to identify paleoclimate indicators of the early Pleistocene from IODP Site U1534. Our interval is located approximately 89 (~2.3 my) to 120 mbsf (~2.6 my) with an average sedimentation rate of 1 cm per 1,000 years. The time frame is poorly dated due to a lack of paleomagnetic reversals. As a result, dating was primarily done through diatom biostratigraphy. The samples are located within Lithostratigraphic Unit II, which is dominated by biosilica-bearing to biosilica-rich dark greenish gray and very dark greenish gray silty clays, with quartz taking up more than 50% of the terrigenous fraction. Feldspars, micas, and glauconite minerals are also highly present at the interval. After analyzing the b*, natural gamma radiation (NGR), and gamma ray attenuation (GRA) within our samples, the data suggests a higher sedimentation rate below 106 mbsf with an inflection point once it reaches around 111 mbsf. Understanding the subtle effect of Earth’s orbit on climate and glacial cycles is crucial to understanding not only the past but the future of both the Greenland and Antarctic ice sheets.

Geological Society of America Abstracts with Programs. Vol. 54, No. 6

doi: 10.1130/abs/2022AM-380669

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