GEOL 4010 QUATERNARY GEOLOGY Instructor: Dr' Hester Jiskoot

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GEOL 4010QUATERNARY GEOLOGYInstructor Dr.
Hester Jiskoot
LECTURE 14
Erosional and periglacial Quaternary records
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TRIMLINES
Frost shattering
Ice scouring
Three weathering zones ? Zone above upper
trimline blockfields, tors, Tertiary
weathering ? Outer zone periglacial
weathering during deglaciation some glacial
erosion joint widening ? Zone below trimline
(subglacial zone) only Holocene
weathering glacial features well preserved
Glacial, climatic or thermal trimlines???
Example Glen Nevis, LOCH LOMOND (FIG 12.71)
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SUBGLACIAL EROSION low mountain environment
Bulk sediment input? Pattern of erosion analogue
to continental ice sheets? Ice dynamics, geology,
landscape?
Glacial Erosion F (pre-existing landscape,
geology, Tice,
Dynamicsice, Extentice)
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EROSIONAL PROCESSES
Erosion F(Tice, Fluxice)
Bedrock highs subject to gtgt stress soft rock
rock drumlins hard rock roche moutonnées and
cragtail steps Orientation bedrock relative to
ice flow (joints/weaknesses)
1) removal pre-existing regolith 2) abrasion 3)
quarrying (fracture plucking)
?Velo - quarrying dominant ?Velo - abrasion
dominant
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LANDSCAPES OF SUBGLACIAL EROSION (Sugden John,
1976 Benn Evans, 1998)

• Areal scouring
• Selective linear erosion
• Little/no erosion
• Alpine erosion
• Cirque erosion

FIG 9.62 BE, 1998
RELECTION AVERAGE GLACIAL CONSITIONS DURING
QUATERNARY
LINK GLACIAL PROCESSES AND LANDSCAPE EVOLUTION
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LANDSCAPES OF SUBGLACIAL EROSION Greenland (Sug
den John, 1976)
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SUBGLACIAL PRESERVATION OF LANDFORMS
Ice divide position? Cold ice? Nunataks?
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POSSIBLE THERMAL DEVELOPMENT OF AN ICE SHEET
Cold
ADVANCE
Warm
GLACIAL MAX.
Cold
Warm
ELA
RETREAT
Cold
Warm
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PERIGLACIAL LANDFORMS

• Environmental implications
• climate
• glaciation
• permafrost conditions
• wind conditions
• Table 14.1. Ballantyne Harris (1994)

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INDIRECT EVIDENCE FOR GLACIATION PLEISTOCENE
RIVERS
(PL GIBBARD)
BLOCKING BASELINE VARIATIONS WATERSHED
VARIATIONS SOURCE MATERIAL TECTONICS CLIMATE
RELATED SOURCE MATERIAL AGGRADATION-EROSION
Elbe, Weser, Rhine, Meuse, Scheldt, Thames,
Somme, Seine Baltic, Channel