Denver Dust Bowl

Denver Dust Bowl

A lot of sand gets blown around in Colorado.

Great Sand Dunes National Park and Preserve is a United States National Park located in the San Luis Valley, in the easternmost parts of Alamosa County and Saguache County, Colorado, United States.

Great Sand Dunes National Park

The dunes were formed from sand and soil deposits of the Rio Grande and its tributaries, flowing through the San Luis Valley.

Westerly winds picked up sand particles from the lake and river flood plain.

As the wind lost power before crossing the Sangre de Cristo Range, the sand was deposited on the east edge of the valley.

This process continues, and the dunes are slowly growing.

https://en.wikipedia.org/wiki/Great_Sand_Dunes_National_Park_and_Preserve

Some of this sand gets deposited in the Denver Basin.

This map is a product of a study of the geomorphology and stratigraphy of sand sheets and dune fields in eastern Colorado.

Eolian sediment blankets about 60 percent of Colorado east of the Rocky Mountains (Madole, 1995a).

Of this eolian cover, about 30 percent is sand and 70 percent is loess.

Colorado Basin Contours

Contours (in meters) drawn on the top of Precambrian rock define the extent and depth of the Denver Basin (after Hansen and Crosby, 1982, U.S. Geological Survey Professional Paper 1230). Shaded areas are Precambrian rock-cored mountains that bound the west edge of the basin. Mountains in western Colorado are not shown.

Distribution of Late Quaternary Wind-Deposited Sand in Eastern Colorado
R.F Madole, D.P. VanSistine and J.A. Michael – 2005
U.S. Geological Survey Scientific Investigations Map 2875
http://pubs.usgs.gov/sim/2005/2875/pdf/2875pam.pdf

Aeolian processes, also spelled eolian or æolian, pertain to wind activity in the study of geology and weather and specifically to the wind’s ability to shape the surface of the Earth (or other planets).

https://en.wikipedia.org/wiki/Aeolian_processes

Loess is an aeolian sediment formed by the accumulation of wind-blown silt, typically in the 20–50 micrometer size range, twenty percent or less clay and the balance equal parts sand and silt that are loosely cemented by calcium carbonate.

https://en.wikipedia.org/wiki/Loess

Digging into the Denver Basin sand reveals there are 1st and 2nd Millennium layers of soil embedded in the sand.

Holocene eolian sand stratigraphy near Hillrose

Numerical age control for eolian sand units in eastern Colorado

Distribution of Late Quaternary Wind-Deposited Sand in Eastern Colorado
R.F Madole, D.P. VanSistine and J.A. Michael – 2005
U.S. Geological Survey Scientific Investigations Map 2875
http://pubs.usgs.gov/sim/2005/2875/pdf/2875pam.pdf

The upper layer of soil is estimated to have formed between 1020 and 1250 AD.

Upper Buried Soil

The upper buried soil is estimated to have formed primarily between about 930 and 700 years ago (A.D. 1020 and 1250).

The interval is approximately coincident with the peak of the European Medieval Warm Period.

Lamb (1985) notes that the climax of this warm interval “was not quite contemporaneous everywhere,” but “in the heartland of North America, as in European Russia and Greenland, the warmest times may be placed between about A.D. 950 and 1200.

Distribution of Late Quaternary Wind-Deposited Sand in Eastern Colorado
R.F Madole, D.P. VanSistine and J.A. Michael – 2005
U.S. Geological Survey Scientific Investigations Map 2875
http://pubs.usgs.gov/sim/2005/2875/pdf/2875pam.pdf

The lower layer of soil “ceased to develop” around 675 AD.

Lower Buried Soil

The lower soil ceased to develop when it was buried, which, on the basis of two calibrated 14C ages of the upper 10 centimeters of the buried soil and two IRSL ages of sand in the middle unit (unit 3b, fig. 11), is estimated to have occurred about 1,275 yr B.P. (A.D. 675).

The duration of landscape stability that allowed this soil to develop is unknown.

Distribution of Late Quaternary Wind-Deposited Sand in Eastern Colorado
R.F Madole, D.P. VanSistine and J.A. Michael – 2005
U.S. Geological Survey Scientific Investigations Map 2875
http://pubs.usgs.gov/sim/2005/2875/pdf/2875pam.pdf

The chronology graphic provided with these date determinations is difficult to digest.

However, using a revised layout [that includes two excluded outlier data points in red] the dating context for these buried soil layers becomes more accessible.

Ages of late Holocene eolian sand units in the South Platte River area

Denver Dust Bowl Layers

See: https://malagabay.wordpress.com/2016/04/08/digitised-japanese-isotopic-tree-thermometer/

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Gallery | This entry was posted in Atmospheric Science, Catastrophism, Heinsohn Horizon, History, Radiocarbon Dating. Bookmark the permalink.

2 Responses to Denver Dust Bowl

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