Lindley Hanson's List: New England Geology - Glaciation

Surficial Geologic History of Maine

Approximately 120 million years passed between the formation of the youngest bedrock in Maine and the Pleistocene Epoch, popularly known as the "Ice Age." There is little evidence of the weathering and erosion of the land that occurred during this long interval, though remnants of deeply weathered and disintegrated bedrock that escaped later erosion by glacial ice can be seen in places.

Continental glaciers similar to today's Antarctic Ice Sheet probably extended across Maine several times during the Pleistocene Epoch, which lasted from about 2.5 million to 10,000 years ago. The slow-moving glacial ice changed the landscape as it scraped across mountains and valleys (Figure 1), eroding rock debris and carrying it for miles (Figure 2). The sand, gravel, and other unconsolidated sediments that cover much of Maine are largely the products of glaciation. Some of these materials were deposited directly from glacial ice as an uneven blanket of stony till; others washed into the sea or accumulated in meltwater streams and glacial lakes as the ice receded. Glaciation also disrupted earlier drainage patterns and helped create the hundreds of modern ponds and lakes scattered across the state.

Introduction

The most recent continental ice sheet to cover New England was the Laurentide, which formed during the late Wisconsinan glacial stage. The Laurentide ice sheet formed in Canada approximately 75,000 years ago. During the early and middle Wisconsinan stages the ice sheet advanced, then retreated from northern New England. Late Wisconsinan cooling 25,000 years ago initiated another advance of the ice sheet. This time it reached southern New England, stopping just south of the Cape Cod peninsula in the the vicinity of Martha's Vineyard and Nantucket Islands about 21,000 years ago. As the global climate warmed 18,000 years ago, the ice sheet began its retreat from southern New England. The portion of the ice front that covered eastern Massachusetts had a lobate form.

U.S. Geological Survey Open-File Report 2006-1008
High-Resolution Geologic Mapping of the Inner Continental Shelf: Boston Harbor and Approaches, Massachusetts

by Seth D. Ackerman, Bradford Butman, Walter A. Barnhardt, William W. Danforth and James M. Crocker

Published 2006
This report presents the surficial geologic framework data and information for the sea floor of Boston Harbor and Approaches, Massachusetts (fig. 1.1). This mapping was conducted as part of a cooperative program between the U.S. Geological Survey (USGS), the Massachusetts Office of Coastal Zone Management (CZM), and the National Oceanic and Atmospheric Administration (NOAA). The primary objective of this project was to provide sea floor geologic information and maps of Boston Harbor to aid resource management, scientific research, industry and the public.

he Stellwagen Bank region off eastern Massachusetts: a Wisconsin glaciated Cenozoic sand banks/delta?
Purchase the full-text article



References and further reading may be available for this article. To view references and further reading you must purchase this article.

Elazar Uchupi Corresponding Author Contact Information, E-mail The Corresponding Author

Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA

Received 22 July 2003;
Revised 5 January 2004;
accepted 5 January 2004.
Available online 10 March 2004.

Abstract

Stellwagen and Tillies banks, Jeffreys Ledge, the erosional remnants shoreward of the banks in Massachusetts Bay, Cape Cod Bay and beneath Cape Cod may define an Eocene sand banks/delta. The present configuration of the region is due to a combination of pre-Wisconsin fluvial erosion, Wisconsin proglacial, subglacial and marine processes and Holocene marine processes. Wisconsin sediments south of Jeffreys Ledge experienced deformation and the formation of sag basins by the sinking of the overlying sediments into the underlying fine grained mass with the sediments between the basins being squeezed up to producing diapirs. The western part of Jeffreys Ledge rising tens of meters above its surroundings is a moraine created during a local re-advance when the overall Laurentide ice was retreating prior to 14 000 years ago. This re-advance resulted in the deformation of Coastal Plain and Wisconsin strata.

Author Keywords: Author Keywords: Eocene sand banks/delta; Coastal Plain erosional remnants; Wisconsin subglacial tectonism; subglacial tunnel valleys

Principal Investigators: Terence Hughes, James Fastook

This is a proposal to model the late glacial Laurentide Ice Sheet from its closest approach to steady-state equilibrium at ~25,000 BP (years before present), through reversible stadial-interstadial transitions associated with Laurentide iceberg outbursts (Heinrich events 2 and 11), and across the threshold of irreversible Laurentide collapse after the last iceberg outburst at ~11,000 BP (Heinrich event 0). The goals are to determine if these ice-sheet changes could have triggered climate changes on the timescale of abrupt ice sheet change, and to investigate the structure of any changes. The plan is to isolate mechanisms of abrupt change on the order of hundreds of years in the ice sheet that are large enough to trigger climate changes captured as time “snapshots” by our coupled global and regional atmospheric climate models. Specific modeling tasks are: