Iowan erosion surface

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The Iowan Erosion Surface (IES) is a geographic region located mostly in northeastern Iowa and extends into southeastern Minnesota. [1]

Iowa State of the United States of America

Iowa is a state in the Midwestern United States, bordered by the Mississippi River to the east and the Missouri River and Big Sioux River to the west. It is bordered by six states; Wisconsin to the northeast, Illinois to the east, Missouri to the south, Nebraska to the west, South Dakota to the northwest and Minnesota to the north.

Minnesota State of the United States of America

Minnesota is a state in the Upper Midwest, Great Lakes, and northern regions of the United States. Minnesota was admitted as the 32nd U.S. state on May 11, 1858, created from the eastern half of the Minnesota Territory. The state has a large number of lakes, and is known by the slogan the "Land of 10,000 Lakes". Its official motto is L'Étoile du Nord.

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History of IES analysis

The IES has been a center of controversy for Quaternary workers due to its topographic relief and other elements. [2] ).

Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene. The informal term "Late Quaternary" refers to the past 0.5–1.0 million years.

Early workers proposed the notion that the surface was a glacial deposit between the early Wisconsinan and Illinoian stages. [3] [4] In 1968, Ruhe proposed that this area underwent a dramatic erosive event during the Late Wisconsinan. [2]

Geological history

Most of the region is underlain by pre-Illinoian till, with an age of greater than 0.5 Ma. A thin blanket of Late Wisconsinan aged loess covers the in some places. The relief of the IES itself is generally flat with broad, peculiar interfluves sitting atop of it. The broad elliptical interfluves are commonly referred to as paha and are oriented in a NW-SE (northwest to southeast) direction while each paha is generally isolated or at a distance from one another on the IES. [5] The NW-SE orientation is attributed to Pleistocene-era oriented snowdunes that melted over the permafrost table, which then eroded and formed oriented depressions in the terrain. This was followed by episodic blankets of paleo-snow and its snowmelt to wear back the rim or scarp of the depressions which resulted in the broad, leveled, erosional plain called the Iowan Erosion Surface. [6]

The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma.

Till Unsorted glacial sediment

Till or glacial till is unsorted glacial sediment.

Loess A predominantly silt-sized clastic sediment of accumulated wind-blown dust

Loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of the Earth's land area is covered by loess or similar deposits.

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Driftless Area

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Paha (landform)

Paha are landforms composed of prominent hills that are oriented from northwest to southeast and typically have large loess deposits. They developed during the period of mass erosion that developed the Iowan surface, and are considered erosional remnants and are often at interstream divides. Paha generally rise above the surrounding landscape more than 20 feet (6.1 m). The word paha means hill in Dakota Sioux. A well known Paha is the hill on which the town of Mount Vernon, Iowa developed.

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Periglaciation

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Climatic geomorphology

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References

Inline citations

  1. Prior, 1991
  2. 1 2 Ruhe et al., 1968
  3. Kay, G (1929). "The relative ages of the Iowan and Illinoian drift sheets". American Journal of Science . 16: 497–518.
  4. Calvin, Sam (1899). "Iowan Drift". Geological Society of America Bulletin. 10: 107–120. doi:10.1130/gsab-10-107.
  5. Iannicelli, M. (2010). "Evolution of the Driftless Area and contiguous regions of midwestern USA through Pleistocene periglacial processes." The Open Geology Journal, vol. 4, pp. 35 – 54.
  6. Iannicelli, M. (2010). "Evolution of the Driftless Area and contiguous regions of midwestern USA through Pleistocene periglacial processes." The Open Geology Journal, vol. 4, pp. 35 – 54.

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