1 A Changing Cryosphere: The Past and Present

Tuesday, 23 May 2023
8:00 AM - 12:00 PM
Room 304-306

1ST CONTINENTAL SIZE GLACIATION REACHING MISSISSIPPI DRAINAGE AREA

Paper number: 1-13
Program: Theme Sessions
Time: 11:40 AM – 12:00 PM

Authors

Abstract

Interpretation of ODP 100 core 625B — drilled in eastern Gulf of Mexico (GoM) — generally presumes existence of multiple melt-water events during Early Matuyama Chron. Reports of Joyce et al. (1990, 1993) and of Roof et al. (1991) document many aspects related to this pilot ODP mission, but original conclusions were based on planktonic species alone. Based on benthic data now available for parts of this core a new globally related time-scale is presented. Using the terrigenous proxy — quartz, dolomite, and dilution (of carbonates) provided in Roof et al. — it is shown that 1st glaciation to reach Mississippi River (MR) basin should be during MIS 50 (~1.5 Ma), a 2nd group of glacial advances is projected during MIS 32/30 (~1.085-1.035 Ma). This revision is supported by diverse proxy from the Great Plains, Baffin Bay, and Greenland. Furthermore, the often quoted ‘melt-water spikes’ during Early Matuyama period are related to collapse of thermohaline circulation in northern North Atlantic during de-glaciation when ice is not present in MR drainage area. Negative δ18O excursions for true melt-water discharges — from MR — never reach the magnitude or duration of Early Matuyama anomalies. It is shown that these (apparent) ‘melt-water spikes’ (of Joyce et al.) lack a coincident terrigenous signature and are not a signal from MR — and therefore are an invalid indicator for glaciations. Other evidence reveals that meltwater from MR occurs during late glacial stages — the negative planktonic δ18O anomalies occurring near interglacial peaks, are not melt-water, and are attributed to an alternative mechanism. An Early Matuyama warm Period (EMwP) from 2.4-1.77 Ma (MIS 95/94 to MIS 65) is proposed.

Geological Society of America Abstracts with Programs. Vol. 55, No. 5

doi: 10.1130/abs/2023RM-387850

© Copyright 2023 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.