chapter_9_part_1

chapter_9_part_1 - Glacial facies Glacial environments...

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Glacial facies • Glacial environments encompass broad areas… – Deposits on land = Continental Facies • Grounded ice facies, – Unstratified – Stratified • Proglacial/periglacial facies – glaciofluvial – glaciolacustrine – Deposits at sea = Glacial-marine Facies • Proximal facies – Near ice-terminous in water • Distal facies – Beyond ice terminious on open shelf
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Continental Ice Facies: Grounded ice facies • Unstratified diamicts – Till deposited directly from ice on land • Found in various types of moraines – unstratified and unsorted • pebbles, cobbles and boulders • matrix of sand, silt, and clay – Sands and silts commonly angular – silt/clay produced by glacial abrasion Quaternary unstratified diamicton, Alaska
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Continental Ice Facies: Grounded ice facies • Stratified diamicts – deposited from meltwaters • upon, within, beneath or marginal to the glacier • known as ice-contact sediments • transported and reworked by meltwater – Consists of gravels, sands and silts – Better sorting – Accumulates in channels or mounds • Kames = small mound-shaped accumulations of sand or gravel formed in meltwater ponds or crevasses in stagnant ice • Kame terraces = similar accumulations deposited along valley glacier • Eskers = narrow sinuous ridges of stratified sediment – meltwater tunnels at the base or through the glacier
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Stratified diamict in an esker system
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Continental Ice Facies : Proglacial -environment Facies • Glacial meltwater transports large quantities of glacial debris basinward of ice-contact zone – glaciofluvial sediment (e.g., braid streams) – or glaciolacustrine sediment • Has characteristics of the depositional setting with some evidence of glacial derivation – Presence of varves from seasonal variation in meltwater
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Continental Ice Facies : Periglacial - environment Facies • Wind-deflation of outwash plain sediment provides silt-size sediment • Eolian transport of fine silts/clays downstream – Dominantly angular grains of quartz – Coarser particles construct dunes in periglacial areas • lacks well-defined stratification because of uniform grain size
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Marine Glacial Facies : Proximal Facies • Setting = marine terminous of glacier/ice sheet • Sediment constructs subaqueous sediment fans – meltwater conduits – fluidized till – melt out from floating ice – E.g., till deltas • Sands and gravels accumulate within channels from sediment gravity underflows • Mud and sand rain out of sediment plumes
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This note was uploaded on 02/20/2010 for the course GEOL 3032 taught by Professor Bouma,a during the Fall '08 term at LSU.

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chapter_9_part_1 - Glacial facies Glacial environments...

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