2002-2003 Science Planning Summary

Geology & Geophysics

Dr. Scott Borg
Program Manager

GO-054-A

NSF/OPP 98-11877
Station: McMurdo Station
RPSC POC: Karla College
Research Site(s): Dry Valleys

Response of the East Antarctic Ice Sheet to middle miocene global change
Dr. David R. Marchant
Boston University
Department of Earth Sciences
marchant@bu.edu
Dr. Huiming Bao
Louisiana State University, Baton Rouge

Deploying Team Members: Huiming Bao . Sarah E Burns . James W Head . Emily L Klingler . Adam R Lewis . David R Marchant . Helen Margerison . Greg Michalski . Stephanie G Thomas
Research Objectives: Marine oxygen-isotope records, which register changes in ocean-water temperatures and global ice budget, show a major and permanent shift about 14 million years ago. Previously, this shift was thought to be linked to three geologic events, (1) the build-up of glacier ice in East Antarctica, (2) the development of a polar-style ice sheet in Antarctica, or (3) the initiation of the modern mode of ocean circulation off Antarctica (dominated by high-latitude deep water sources and strong meridian thermal gradients).

This project is designed to determine Antarctica 's role in this fundamental global climate shift. The group addresses the question of climate change and ice-sheet dynamics by examining Miocene-aged till sheets, lacustrine deposits, and moraines in the Dry Valleys region of southern Victoria Land. The mapped distribution of these deposits provides information on the areal extent of east antarctic ice. The textural characteristics of these deposits sheds light on climate conditions that prevailed during and after sediment deposition. Argon 40/39 analyses of ashfall deposits interbedded with these sediments, along with cosmogenic He-3, Be-10, and Al-26 analyses of surface boulders on moraines, will provide chronologic control.


Field Season Overview:
Nine team members will participate in two collaborative projects with combined logistical support:

- Dr. David Marchant (GO-054-A)

- Dr. Huiming Bao (GO-051-O)

Project team members will erect camps in the Olympus and Asgard Ranges. With helicopter support, researchers will map moraines and collect soil samples. Soil excavations will be filled in and the desert pavement replaced, a technique that allows for rapid surface recovery. Researchers will also collect volcanic ash in the McKelvey Valley region and measure ancient sub-glacial meltwater channels at the head of Wright Valley.

Supported by the University NAVSTAR Consortium (UNAVCO) and support contractor personnel, two team members will acquire high-precision elevation data for up to 50 sites within the western Dry Valleys region. The data will be used to produce high-resolution, one-meter contour maps of selected study areas and to provide control for analyses of cosmogenic data. Rock and soil samples will be returned to the investigators’ home institutions for analyses.