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R E L I C D U N E F I E L D S I N N O R T H A M E R I C A
Photograph: kcspor!our
Sand and loess deposits in the United States Sun and Muhs 2007
Global distribution of aeolian sand Sun and Muhs 2007
Lt. G.K. Warren’s sketch of the Nebraska Sand Hills, 1855
Source: Stephen Wolfe
“...the men and horses were in great want of water, and the heat was very great while travelling through miles of burning sand.”
Captain John Palliser, 1863
Source: Hughenholtz et al., Aeolian Research (2010)
Were these dune fields more active prior to the 20th century?
Photograph: Stephen Wolfe
Impurities or defects in this structure can act as “traps” for free electrons.
free electron
The rate at which free electrons are produced, and traps are filled, is proportional to:
• the amount of radioactive elements in the minerals being dated
• the amount of radioactive elements in their surroundings.
Source: Wolfe et al., Geographie physique et Quaternaire, 2002
Photograph: Stephen Wolfe
Stephen Wolfe Geological Survey of Canada
Source: Stephen Wolfe
Source: Wolfe et al., Geographie physique et Quaternaire, 2002
Source: Wolfe and Hughenholtz, Geology, 2010
Source: Stephen Wolfe
Light Detection and Ranging (LiDAR)
Source: Wolfe and Hughenholtz, Geology, 2010
barchan dune
parabolic dune
back ridgeresidual
dune ridges
Parabolic dunesPhotograph: Shooting Chris
Barchan dunesPhotograph: Ron Scho!
S TA B L E I S O T O P E S I N P A L E O C L I M AT O L O G Y
less O18“depleted”
more O18“enriched”
more O18
“enriched”
less O18“depleted”
Source: Jouzel et al., Journal of Geophysical Research, 1994
Source: Jouzel et al., Journal of Geophysical Research, 1994
“light”
“heavy”
“more positive” δO18 = “heavy” = “enriched”for example, ocean water
“more negative” δO18 = “light” = “depleted”for example, glacial ice
Source: Bowen and Wilkinson, Geology, 2002
δO18 in precipitation
