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USGS Navajo Land Use Planning Project (NLUPP)

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History of eolian deposits: Paleoclimate


Climate-related events can be determined, in part, through understanding the relationships between and ages of alluvial fans, debris flows, soils, and dunes. Resolving climate history of the region is important to understanding the effect of climate change in the future. The history preserved in, and deciphered from, eolian and alluvial fan deposit may provide valuable insights into the impact of climate change on ancestral peoples that lived in the region, the history of regional volcanism, and the evolution of ecosystems in the region.


  Alluvial channel fill
Right: Example of stream floodplain stratigraphy exposed by arroyo incision into a older, stream valley-fill deposits.

The landscape in the Navajo Nation preserves a record of climate history. Sand dunes are sensitive indicators of climate change; they are dynamic and respond to:
  • Overall Moisture Balance
  • Degree of vegetation cover
  • Wind circulation patterns
Areas that are now dune fields exist in areas that were lake beds during wetter glacial periods during the Pleistocene Epoch. Cycles in climate change during the Holocene Epoch are recorded in the stratigraphy of alluvial fans and dune ramps deposits. Ancestral peoples living in the region left behind evidence, such as charcoal in fire pits, that can be used to radiocarbon dated. Paleontological evidence (pollen and microfossils such as ostracodes) can be derived from spring deposits and ponded sediments.

  Dune ramp

Example of a dune ramp located on an alluvial fan. Studies of interbedded dune sand and stream deposits may help reveal information about history of regional climate change.

(images source: Margaret Hiza-Redsteer, USGS Flagstaff, AZ)
 

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