Paper No. 4
Presentation Time: 1:30 PM-5:30 PM
THE PLIO-PLEISTOCENE SECTION OF ODP SITE 188-1165, PRYDZ BAY, ANTARCTIC CONTINENTAL MARGIN: A HIGH-RESOLUTION INTEGRATED-STRATIGRAPHY COMMITTE (HIRISC) REPORT
During ODP Leg 188 to Prydz Bay, East Antarctica, several of the shipboard scientists formed the High-Resolution Integrated Stratigraphy Committee (HiRISC). The committee was established in order to furnish an integrated data set from the Pliocene portion of Site 188-1165 as a contribution to the ongoing debate about Pliocene climate and climate evolution in Antarctica. The proxies that were determined in our various laboratories were the following: magnetostratigraphy and magnetic properties, grain-size distributions (granulometry), near-ultraviolet/visible/near-infrared (NUV/VIS/NIR) spectrophotometry, calcium carbonate content, characteristics of foraminifer, diatom, and radiolarian content, clay mineral composition, and stable isotopes. In addition to the HiRISC samples, other data sets contained in this report are subsets of much larger data sets.
Our data sets demonstrate a very dynamic East-Antarctic continental margin, with rapid depositional episodes alternating with erosional episodes and the formation of hiatuses. We see a pronounced change in most parameters at 34 mbsf, at about 3.4 to 3.5 Ma. For instance, brightness, ARM, IRM and ARM/IRM all change. Smectite decreases upcore whereas kaolinite increases. Maghemite decreases upcore, indicating either a change in source area/depositional mechanism, or a climatic deterioration. In any event, the dynamic behavior of the Antarctic margin, juxtaposed to the 'paralyzed landscapes' of the high-elevation interior, poses a challenge to paleoclimatologists and modelers.