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| Geology 370: Glacial Geology
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| Lecture Notes | Grades
| MIS: even numbers generally glacials & odd numbers generally interglacials
Ice age started in late Pliocene ~2.5-1.8 MYBP
Continued on into Pleistocene 1.8 MYBP - 10,000 YBP
Early Pleistocene 1.8 MYBP - 750,000 YBP (MIS 20-36)
Matuyama-Brunhes polarity reversal 750,000 BP marks Early/Middle boundary
Middle Pleistocene 750,000-130,000 YBP (MIS 6-19)
includes Illinoian Glacial (MIS 6 & 8)
possibly more severe than Wisconsin glaciation
~150 m drop in sea level - major land bridges exposed
interglacial (MIS 7)
warm climates & dense vegetation in North America & Europe - little continental erosion & little marine sedimentation
formation of paleosols
sea level higher than today
Late Pleistocene 130,000-10,000 BP
Sangamon Interglacial MIS 5e or all of MIS 5
MIS 5 (130,000-75,000 YBP) or just substage 5e (130,000-115,000 YBP)
midlatitudes slightly warmer than today
sea level slightly higher than today
widespread paleosols
Wisconsin Glacial MIS 2, 3 & 4 (and 5 a, b, c, d)
Dates
starts ~115,000 BP with isotope substages 5a, b, c, d
or, starts ~75,000 BP with isotope stage 4
includes MIS 4, 3 and 2 (and parts of 5)
Early Wisconsin or "Eowisconsin" 115-75 ka YBP; isotope substages 5 a, b, c, d
MIS 5d (115,000-105,000): stadial
MIS 5c (105,000-93,000): interstadial
MIS 5b (93,000-85,000): stadial
MIS 5a (85,00075,000): interstadial
Middle Wisconsin 75-25 ka YBP
MIS 4 (75,000-60,000): stadial
MIS 3 (60,000-25,000): interstadial
Late Wisconsin 25-10 ka YBP; MIS 2
Woodfordian Substage
~ 22,000-12,5000 YBP
Last glacial maximum (LGM) ~21,000-17,000 YBP
Numerous lakes in western mountains
Lake Bonneville, Idaho (wetter conditions than now)
Lake Missoula: western Montanna (ice-dammed lake)
Glacial Lake Agassiz (pro-glacial lake)
formed about 11,700 YBP; drained southwards to Gulf of Mexico
11,000-10,100 YBP drained eastwards to North Atlantic
10,100-9,400 YBP drained northwest
9,400-8,200 YBP drained eastwards to North Atlantic
numerous catastrophic outburst
Evolution of the Great Lakes
Twocreekan Substage (Allerod)
interstadial: 12,500-11,8000 YBP
retreat of ice; most of Great Lakes region deglaciated
followed by eventual establishment of spruce forest at Two Creeks
corridor opened between Laurentide & Cordilleran Ice Sheets
Greatlakean Substage (Younger Dryas)
stadial ~11,800-10,000 YBP
glacial readvance; Two Creeks forest killed ~11,850 YBP
possible catastrophic outflow of ice-dammed lakes to North Atlantic
Short term fluctuations in proxy records
Heinrich events
massive iceberg flotillas deposited ice rafted debris (IRD) across Atlantic
events associated with very cold temperatures & drops in ocean salinity
evidence for 6 sudden changes in ocean cores
H1 ~14,000 YBP
H2 ~21,000 YBP
H3 ~28,000
H4 ~40,000
H5 ~51,000 YBP
H6 ~63,000 YBP
possibly related to ice sheet instabilities
Dansgaard-Oeschger (D-O) events
rapid temperature rise of 8-16C (interstadial)
slow temperature drop back to stadial conditions
Heinrich events occur after a series of declining D-O events
Bond cycles
methane cycles
contain several D-O events
slow cooling leads to more cold-based ice
sudden warming causes bed to thaw & ice sheet surges producing Heinrich events
Image credit: NOAA Paleoclimatology Slide Set. Heinrich Events: Marine Record of Abrupt Climate Changes in the Late Pleistocene. http://www.ncdc.noaa.gov/paleo/slides/slideset/19/index.html
Image credit: NOAA Paleoclimatology Slide Set. Heinrich Events: Marine Record of Abrupt Climate Changes in the Late Pleistocene. http://www.ncdc.noaa.gov/paleo/slides/slideset/19/index.html
MIS 1
Hypsithermal (Altithermal) about 9,000-6,000 YBP; climatic optimum
Little Ice Age: ~1500s to 1800
