lecture 05: pleistocene epoch of quaternary period Flashcards
pleistocene epoch time period
2.58 Ma to 11.7 Ka
milankovitch cycles
‘canon of the earth’s insolation’: characterizes the climates of all the plants
explanation of earth’s long-term climate changes caused by changes in the position of the earth in comparison to the sun
what are the 3 milankovitch orbital cycles
eccentricity, obliquity, precession
beringia
areas free of ice, much of asia, siberia to yukon (some areas up to 1 Ma)
last glacial maximum
ice sheet and glacial coverage peaked
the 2 ice sheets
cordilleran and larentide (divided into keewatin and labrador)
driftless area
glaciers missed one region of the midwest USA leaving an unglacieted region surrounded by glaciated landscapes.
great lakes likely deflected or redirected the glaciers since it’s more sloped and hilly
remaining continental glaciers as of today
antarctic and greenland ice sheets
post-glacial isostatic adjustment
uplift of the land surface following ice melt
north american ice-free corridor
~13.8ka
coast + yukon –> alberta
proglacial lakes
would form at the margins of large glacial lakes created by receding glaciers
misfit streams
forms in the hollow valley of divides or ice dams
glacial lake agassiz
largest proglacial lake in Manitoba and parts of saskatchewan, ontario, n. dakota and minnesota
alberta’s connection to lake aggasiz mega-flood
clearwater to athabasca to arctic ocean
cut the clearwater gorge
sent massive deposits of delta sand down river
potholes
formed from extreme vortexes in the water
catastrophism vs uniformitarianism
competing geological theories
younger dryas
12.9 Ka - 11.7 Ka
considered end of ice age
named after arctic plant (dryas octopetala)
showing up in europe’s paleo-vegetation at this time
microspherules
form at >2200C
inconsistent with anthropogenic and volcanic materials, perhaps molten iron droplets
carolina bays
inferred to be ‘ejecta’ craters (secondary impacts by ice)
ice-margin
interface between ice and the glacier foreland or pro-glacial zone
subglacial
situated or occurring underneath a glacier or ice sheet
moraines
push moraines, dump moraines, ablation moraines
drumlins
low oval mound or small hill, typically one of a group, consisting of compacted boulder clay molded by past glacial action
outwash fans/plains
fan-shaped body of sediments deposited by braised streams from a melting glacier
kames
glacial landform, irregularly shaped made of sand or gravel. can be deposited at or near the terminus of a glacier
kame-kettle topography
locataed on end moraines where sediment accumulates at the end of the glacier. kettles are depressions formed by ice being trapped under
glacial erratic
large rocks from elsewhere
glaciolacustrine
glacial lake deposits
glaciofluvial
glacial river deposits
surficial geology
refers to the unconsolidated geologic materials lying on top of the bedrock. subsequent soil development is highly dependent on these original source materials
eolian deposits
sand
stagnant ice moraine
collapsed and slumping of debris near ice margin
what is a feature of stagnant ice
doughnuts
ice-thrust moraine
formed by displacement of blocks or ‘rafts’ that are left more or less intact
major meltwater channel
massive river drainage during melting of glacier and possible major break in glacial lake
