2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
Paper No. 314-5
Presentation Time: 2:30 PM-2:45 PM

Coarse Fraction Abundances and the Plio-Pleistocene Record of Iceberg-Rafting at IODP Sites 1305 and 1308, North Atlantic Ocean

KRISSEK, Lawrence1, MCKEE, Margaret Haack2, LEITNER, P.3, STOLL, A.3, KRISSEK, P.3, CALHOUN, J.P.1, BAUMGARTNER, L.1, BLAKE, Daniel4, and GULEFF, E.1, (1) School of Earth Sciences, The Ohio State Univ, 125 S. Oval, Columbus, OH 43210, krissek.1@osu.edu, (2) Department of Geology and Environmental Sciences, Northern Illinois University, DeKalb, IL 60115, (3) The Ohio State University, Columbus, OH 43210, (4) Earth & Environmental Sciences, Wright State University, Dayton, OH 45435

Plio-Pleistocene orbital- and suborbital-scale climatic variability in the North Atlantic was investigated during IODP Expedition 303, which cored Sites 1305 (southwestern Eirik Drift, 3459 mbsl) and 1308 (reoccupation of DSDP Site 609, central North Atlantic, 3871 mbsl).

Sediments from Sites 1305 and 1308 were sampled with an average time spacing of ~3 ky, and analyzed for coarse fraction abundance (CFA; weight % of the 150 m 2 mm fraction) by sieving. Present data is the total CFA, including both biogenic particles (predominantly foraminifers) and terrigenous grains (interpreted as iceberg-rafted debris, or IRD). IRD grains have a significantly higher weight per grain, however, so IRD variations are interpreted to drive major variations in total CFA.

The Site 1305 record extends to ~1 Ma, and contains six to seven major CFA peaks in the interval 0 700 ka. CFAs do not appear to correlate directly with marine isotope stages (MIS); e.g., both MIS 6 and MIS 11 have relatively low CFAs. However, larger CFA peaks tend to occur near transitions from an interglacial to a glacial. In the interval 700 ka 1.0 Ma, CFAs vary more frequently, recording local response to the mid-Pleistocene transition.

The Site 1308 record extends to ~1.8 Ma. CFAs vary quasi-cyclically at a period of ~100-150 k.y. to ~950 ka, and CFA maxima tend to occur during MIS-defined glacials; however, not every glacial is marked by a CFA maximum, and a few maxima occur within interglacials or near stage transitions. CFA variations are more rapid before ~950 ka.

Future work will define more clearly the roles of global vs. local controls on iceberg-rafting by: extracting the IRD signal from the CFAs; defining iceberg sources from IRD composition; and evaluating the IRD signals within the oxygen isotope stratigraphy developed for each site.

2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
General Information for this Meeting
Session No. 314
Paleoclimatology/Paleoceanography
George R. Brown Convention Center: 310BE
1:30 PM-5:30 PM, Wednesday, 8 October 2008

Geological Society of America Abstracts with Programs, Vol. 40, No. 6, p. 499

© Copyright 2008 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.