Simplified Surficial Geologic Recent stream alluvium, including flood What will you find if you dig a hole? plain, stream terrace, and alluvial fan deposits. This cross section shows common relationships of glacial and postglacial surficial sediments Map of Maine Fort Kent in valleys above (left) and below (right) the marine limit. Recent swamp, marsh, and bog deposits DEPARTMENT OF CONSERVATION Former glacial Upper limit of late-glacial lake level Maine Geological Survey 9 marine submergence Glacial lake-bottom deposits 10 Modified from Thompson, W. B., 2 8 3 8 and Borns, H. W., Jr. 1 6 10 Glacial stream deposits and glacial-lake deltas. 2 4 Surficial Geologic Map of Maine, 2 2 2 1985, Maine Geological Survey 1 7 5 3 1 Presque Glacial-marine deposits (silt and clay) Digital cartography by Isle Marc Loiselle 1- Bedrock 6- Marine sand plain 2- Till 7- Fine-grained glacial lake-bottom sediments Glacial-marine deposits (sand and gravel) Robert G. Marvinney 3- Esker 8- Glacial-lake delta State Geologist 4- Glacial-marine delta 9- Postglacial stream-terrace Eskers 5- Glacial-marine clay (Presumpscot Formation) 10- Modern flood-plain 2003 Houlton Mt. Katahdin Till Glacial Recession in Southern Maine
Bedrock and thin glacial sediment cover Ice Marine limit T Millinocket New Ice Brunswick DS 16,000 years ago a continental glacier D T Greenville MAINE covered most of Maine, but was receding from the Nova coastal lowland. The sea was EM S in contact with the ice margin. M Calais Vermont Scotia EM
New Ice Rangeley Eastport New York Hampshire DR Maximum extent of glacial ice T Bangor Ice E Mass. (about 28,000 to 24,000 years ago) IB Machias D Conn. R.I. DS T 15,000 years ago, ML the glacier was receding N.J. rapidly and southern Maine S EM was ice-free. The land was still M exposed continental shelf depressed from the weight of BEM Augusta Mount Desert the ice, resulting in extensive Island submergence of lowland areas. Atlantic Ocean DR E T OP Penobscot Bay The color map (at left) shows the principal types of sedimentary materials that K K cover the bedrock in Maine. Most of these materials were left by glacial ice during OP BR the Pleistocene "ice age". One of Maine's distinctive glacial legacies is the blanket 13,000 years ago, the D of marine sediments across southern portions of the state. The last continental ice glacier had disappeared T Portland sheet was so thick and heavy that it depressed the Earth's bedrock crust several from central and southern hundred feet. Even though global sea level was lower in glacial times, this Maine. Uplift of the land had M Casco Bay EM depression enabled the sea to flood low areas of southern Maine as the glacier caused the sea to retreat. M receded. The dark-blue line on the map shows the inland limit of marine BEM submergence. Numerous islands existed in the flooded area but are not shown here. The recession of the ice sheet caused the land to rise above the ocean, and a BEM - buried end moraine E - esker ML - marine limit wide variety of sedimentary deposits were released from the melting glacier. These BR - bedrock ridge EM - end moraine OP - outwash plain include long esker ridges of sand and gravel formed in tunnels under the ice, shown D - delta IB - ice block S - seawater by the red lines on the map. Maine's eskers and emerged marine features are world- DR - drumlins K - kettle T - till Kittery class examples of glacial deposits. DS - distributary stream M - marine sediments