11
11
888833
2222 22
22
7711
22
33
44
55
Recent stream alluvium, including floodplain, stream terrace, and alluvial fan deposits.
Recent swamp, marsh, and bog deposits
Glacial lake-bottom deposits
Glacial-marine deposits (silt and clay)
Glacial-marine deposits (sand and gravel)
Eskers
Till
Bedrock and thin glacial sediment cover
Marine limit
Simplified Surficial GeologicMap of Maine
DEPARTMENT OF CONSERVATIONMaine Geological Survey
Modified from Thompson, W. B.,and Borns, H. W., Jr.
Surficial Geologic Map of Maine,1985, Maine Geological Survey
Digital cartography byMarc Loiselle
Robert G. MarvinneyState Geologist
2003
The color map (at left) shows the principal types of sedimentary materials that cover the bedrock in Maine. Most of these materials were left by glacial ice during the Pleistocene "ice age". One of Maine's distinctive glacial legacies is the blanket of marine sediments across southern portions of the state. The last continental ice sheet was so thick and heavy that it depressed the Earth's bedrock crust several hundred feet. Even though global sea level was lower in glacial times, this depression enabled the sea to flood low areas of southern Maine as the glacier receded. The dark-blue line on the map shows the inland limit of marine 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 wide variety of sedimentary deposits were released from the melting glacier. These include long esker ridges of sand and gravel formed in tunnels under the ice, shown by the red lines on the map. Maine's eskers and emerged marine features are world-class examples of glacial deposits.
What will you find if you dig a hole?This cross section shows common relationships of glacial and postglacial surficial sediments
in valleys above (left) and below (right) the marine limit.
Upper limit of late-glacial marine submergence
Former glaciallake level
1- Bedrock2- Till3- Esker4- Glacial-marine delta5- Glacial-marine clay (Presumpscot Formation)
6- Marine sand plain 7- Fine-grained glacial lake-bottom sediments 8- Glacial-lake delta 9- Postglacial stream-terrace10- Modern flood-plain
1
1
883
22 2
2
71
2
3
4
5
6
10
9
10
13,000 years ago, the glacier had disappeared from central and southern Maine. Uplift of the land had caused the sea to retreat.
15,000 years ago,the glacier was receding rapidly and southern Maine was ice-free. The land was still depressed from the weight of the ice, resulting in extensive submergence of lowland areas.
16,000 years ago a continental glacier covered most of Maine,but was receding from the coastal lowland. The sea was in contact with the ice margin.
BEM - buried end moraine E - esker ML - marine limitBR - bedrock ridge EM - end moraine OP - outwash plainD - delta IB - ice block S - seawaterDR - drumlins K - kettle T - tillDS - distributary stream M - marine sediments
Glacial Recession in Southern Maine
Glacial stream deposits and glacial-lake deltas.
exposed continental shelf
Atlantic Ocean
MAINE
NewBrunswick
NovaScotia
NewHampshire
Vermont
New York
Mass.
R.I.Conn.
N.J.
Maximum extent of glacial ice(about 28,000 to 24,000 years ago)
Ice
Ice
T
DS
D T
S
MEM
EM
T
ML
Ice
Ice
DR
IB
E
DS
D
T
S
M
BEM
DR
EM
E
TOP
K K
OP
D
M
BR
T
MBEM
EM
Fort Kent
PresqueIsle
Mt. Katahdin
Augusta
Portland
Kittery
Casco Bay
Penobscot Bay
Mount DesertIsland
Bangor
Machias
Calais
Eastport
Houlton
Millinocket
Greenville
Rangeley