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Quaternary Environments Non-Marine Geological Evidence

Quaternary Environments Non-Marine Geological Evidence. Geological Studies. Virtually all continental sedimentary deposits convey a paleoclimatic signal Aeolian Glacial Lacustrine Fluvial Deposits. Loess. Wind blown silt Quartz, Feldspars, and Mica

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Quaternary Environments Non-Marine Geological Evidence

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  1. Quaternary EnvironmentsNon-Marine Geological Evidence

  2. Geological Studies • Virtually all continental sedimentary deposits convey a paleoclimatic signal • Aeolian • Glacial • Lacustrine • Fluvial Deposits

  3. Loess • Wind blown silt • Quartz, Feldspars, and Mica • Material originates from glacial outwash, braided stream deposits, or desert conditions

  4. Loess Deposits Around the World Christopherson. 2004. Elemental Geosystems 4th Edition. Prentice Hall Publisher.

  5. Christopherson. 2004. Elemental Geosystems 4th Edition. Prentice Hall Publisher.

  6. Chinese Loess Chronology • North Central China (southeast of the Gobi Desert) • 300m thick • Alternating sequences of loess and intervening paleosols • Baoji Type section • 37 soils and loess deposits

  7. Luochuan Loess Sequence

  8. Dating of Loess • Relative Dating of the Loess-Paleosol Sections • Aminostratigraphy on snails in the deposit • Thermoluminescence over the last glacial cycle • Paleomagnetism for the Quaterary (dated with K/Ar)

  9. Magnetic stratigraphy of the loess-paleosol section at baoji, loess plateau, north central China

  10. Composite marine oxygen record with the proposed correlation to the loess-paleosol sequence

  11. Grain size variations from the Baoji type section compared to Milankovich cycles (obliquity and eccentricity)

  12. Periglacial Features • Disturbed ground due to extremely low temperature conditions • Provide information on periods of low temperature • Provide information on areas close to the ice sheet margins for which there are few other sources of proxy paleoclimate data

  13. Problems with Periglacial Features • Direct dating of the features is difficult. Usually only get bounding dates. • Indicate a maximum temperature limit only • Discontinuous record

  14. Periglacial Features • Continuous permafrost • Fossil ice wedges – Winter temperatures of -12 to -20°C • Discontinuous permafrost • Pingos – Max annual temperature of -2°C • Intense seasonally frozen ground • Sorted polygons • Stone stripes • Periglacial involutions

  15. Ice Wedge http://www.radio.cbc.ca/programs/quirks/archives/02-03/beringia/beringia.html

  16. Pingo

  17. Patterned Ground

  18. Patterned Ground; Sorted Nets

  19. Patterned Ground; Polygons

  20. Stone Stripes

  21. Stone Stripes

  22. Periglacial Involutions

  23. Snowlines and Glaciation Thresholds • Snowline • Limit between season snow accumulation and permanent snow • Assumed to be at the 0°C isotherm • Equilibrium Line Altitude (ELA) • Limit between accumulation and ablation zones • 70% of total area of glacier • Glaciation level • Lowest limit at which permanent ice field can develop

  24. Problems of Snowline Estimates • Present day analogs have not been well studied • Atmospheric lapse rates in mountainous regions are not well documented • Paleosnowline reconstructions are often based on features of varying age

  25. Glacial Evidence • Destruction of previous evidence • Down-wasting as opposed to shortening • Lag in timing at glacial front • Glacier length • Basal slope • Ice thickness • Temperature • Overall geometry • Dating problems • 14C • Lichenometry • Cosmogenic Isotopes

  26. Glacial Erosion

  27. Glacial Erosion

  28. Glacial History • Holocene Glacier Fluctuations • Most detailed record • Reduction of glacial extent in the mid-Holocene (termed the Altithermal by Antevs) • Little Ice Age • Best recorded in western Europe • Historical records, Paintings, and Sketches • Dendrochronological evidence

  29. Principle Episodes of Glaciation US Mountain Glaciers US Laurentide Canadian Laurentide Poland and Western Former Soviet Union European Alps Southern Alps Antarctica

  30. Glacial Expansion Phases During the Holocene

  31. Lake-Level Fluctuation • Record changes in temperature and precipitation through time • Evidence • Abandoned wave-cut shorelines and beach deposits • Percehed deltas • Exposed lucustrine sediments • Paleosols in a lake core record • Lake Cores • Stratigraphy • Geochemistry • Macrofossil evidence • Microfossil evidence • Sedimentary facies

  32. Lake Basins • Endoreic regions • Land-locked basins with loss through evaporation • Areic regions • Lack of surface drainage • Arid environments • Pluvials • Periods of high lake levels

  33. Areas of Endoreic and Areic Drainage

  34. Pluvial Lakes, 14,500 yr. BP

  35. Lake Lahontan Paleo Lake Level Indicator

  36. Lake Level Reconstructions

  37. Proglacial Lakes, 13,000 Yr. BP

  38. Hoover Dam and Lake Mead

  39. Lake Level ca. 18,000 yr BP

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