THE MCMURDO DRY VALLEYS: A UNIQUE WINDOW INTO CENOZOIC ANTARCTIC ICE SHEET AND CLIMATE HISTORY

A rich and well-preserved set of glacial deposits and erosional features in the McMurdo Dry Valleys provide tremendous insights into the Cenozoic history of the East and West Antarctic Ice Sheets and regional climate via alpine glaciers and mountain ice-caps. The three primary valleys are anything but similar. The decreasing scale of glaciation over the Cenozoic and the wide range in valley threshold heights have combined to restrict areally the deposition of Quaternary sediment such that wide expanses of Tertiary glacial sediment remain exposed.

The valleys feature a variety of primarily glacial bedrock morphologies across their 100 km length and 3 km of relief. We present a landsystems classification of the large-scale bedrock morphology and also contrasting stratigraphies for landscape evolution.

We re-mapped much of the surficial geology in the valleys onto a consistently geolocated set of nested satellite images and aerial photographs. We compiled data on the surface and near-surface sediment and attached these to the pertinent sampling locations using Geographic Information Systems techniques. The sediments date to at least the mid-Miocene and their spatial patterns provide significant constraints on paleo-glacier dynamics.

From this base, we developed a landsystem classification of the surficial glacial deposits. Additionally, we generated a composite lithostratigraphy, climate-stratigraphy, and chronostratigraphy for these sediments. We present these using both maps and sections which are available in GIS format. With the recent production of high-resolution DEMs of the valleys, significant advances in surficial sediment stratigraphy are expected.

Subsurface stratigraphy in the Dry Valleys is the new frontier in glacial history. The near-heroic effort of the Dry Valleys Drilling Project showed the tremendous thicknesses of unconsolidated sediment in the valleys and their antiquity. Development of a stratigraphy for subsurface terrestrial glacial sediments has been expectedly difficult. However, ground-penetrating radar shows significant promise as a technique that couples the subsurface down to 50 m to surface geomorphology and adds spatial analysis to aid core interpretation.