GLACIAL AND POST GLACIAL HISTORY ICE LAKES ISOSTATIC REBOUND TYPICAL STRATIGRAPHY POLLEN AND CLIMATE.

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Presentation transcript:

GLACIAL AND POST GLACIAL HISTORY ICE LAKES ISOSTATIC REBOUND TYPICAL STRATIGRAPHY POLLEN AND CLIMATE

WORLD ICE COVER

WATCH ICE RETREAT as well as SEA and LAND LEVEL RISE

GLOBAL SEA LEVEL HISTORY

Ridge et al., 1999 Dyke & Prest, 1987 Radiocarbon Ages Ice Extent +Thickness = Ice Volume =  Sea Level

History Geology of Vermont, Edward Hitchcock, 1861 Mt. Mansfield Erratic Ludlow, VT Striae

Unweathered erratics and weak soils suggest overrunning by LGM ice. Mt. Washington Erratics Mt. Katahdin Soil

“Common COSMOGENIC Nuclides”......

Target Atoms 10 Be: O, Mg, Si, Fe 26 Al: Si, Al, Fe n 3n3n 4p Spallation How are csi’s made? Muons? < 3% t 1/2 = 700 ky t 1/2 = 1500 ky 5 to 40 at g -1 yr -1

For long-lived or stable nuclides N = P*t + Inheritance

Goofer Point (block, bedrock, boulder) Summit (block) Tuckerman (block) Mt. Washington Long-standing Dogma All of New England overrun and rock surfaces eroded by continental ice

Basin Ponds Moraine (6 boulders) North Basin (3 boulders) Knife Edge and South Peak (2 bedrock) Baxter Peak (bedrock & block) Cathedral Ridge Mt. Katahdin

Summit Block, Baxter Peak 25.6±0.5 ky 1 st indication something is not as expected

Polished Bedrock, Knife Edge 11.2 ± 0.4 ky

North Basin Boulders (n=3),  = 12.3 ± 0.9 ky 10.9 ± 0.4 ky 11.6 ± 0.4 ky 13.9 ± 0.4 ky On lip

Pineo Ridge Calibrated 14 C Age 13.2 to 14.0 ky Average 10 Be: 26 Al Age 13.5 ± 0.6 ky

21.6, 13.4, 13.6 ky 120±3 ky 9.8±0.3 ky Mt. Washington 2 nd indication something is not as expected

Mt. Washington and Mt. Katahdin, nunataks during late Wisconsinan? Not likely! 1. fresh erratics 2. weak soils Recession.. younging

Was continental ice so thin/cold that it eroded little, leaving nuclides from prior exposure on the summits? cone Sub-summit erosion

>500 ky total history BEDROCK 9.3±0.5 ky ERRATIC BAFFIN ISLAND UPLAND

Late Glacial Limit Waterloo Cactus Rock Bush, Baraboo, Observatory

Cold non-erosive upland ice, warm erosive valley ice Pangnirtung Fjord, Baffin Island New England is not unique; there is an Arctic analog.

PREDICTABLE SEQUENCE MEAN WHILE, BACK IN VERMONT

EARLYLATER = STOWE GULLY

OBSERVATION: LAKE SHORE FEATURES ARE TILTED NORTHSOUTH Rising to the north

LAKE SHORELINES CAN BE FOUND AT PREDICTABLE ELEVATIONS

WHAT IS IT? ALNUS or ALDER

WATCH PINE MOVE NORTH

VIEW TOGETHER

Delcourt and Delcourt, 1984 Jackson and Whitehead, 1991 Spear et al., 1994 COOL, WET? meridional flow WARM AND DRY strong westerlies COLD WARMING, MOIST meridional flow Adirondack Mtns. Eastern N. America Pollen, Macrofossils Pollen, Foraminifera COOL, WET? spruce increase COOLING? WARM AND STORMY pine and birch expand WARM AND DRY WARMING White Mtns. Pollen, Macrofossils WARM, DRY? pine and birch expand WARMING COOLING? COOL, WET? spruce increase COLD Max. Seasonality Spruce Minimum C year BP