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The Pleistocene is the geological epoch that lasted from c. 2.58 million to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek πλεῖστος (pleîstos) 'most' and καινός 'new'.
A loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loesses or similar deposits.
The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated in the northern North American Cordillera; the Innuitian ice sheet, which extended across the Canadian Arctic Archipelago; the Greenland ice sheet; and the massive Laurentide Ice Sheet, which covered the high latitudes of central and eastern North America. This advance was synchronous with global glaciation during the last glacial period, including the North American alpine glacier advance, known as the Pinedale glaciation. The Wisconsin glaciation extended from about 75,000 to 11,000 years ago, between the Sangamonian Stage and the current interglacial, the Holocene. The maximum ice extent occurred about 25,000–21,000 years ago during the last glacial maximum, also known as the Late Wisconsin in North America.
The Teays River (pronounced taze) was a major preglacial river that drained much of the present Ohio River watershed, but took a more northerly downstream course. Traces of the Teays across northern Ohio and Indiana are represented by a network of river valleys. The largest still existing contributor to the former Teays River is the Kanawha River in West Virginia, which is itself an extension of the New River. The name "Teays," from the much smaller Teays Valley still extant above the surface, has been associated with the river and the remainder of its related buried valley since 1910. The more appropriate name would be the Ancestral Kanawha Valley. The term Teays is used when discussing the buried portion of the Ancestral Kanawha River. The Teays was comparable in size to the Ohio River. The River's headwaters were near Blowing Rock, North Carolina; it then flowed through Virginia, West Virginia, Ohio, Indiana, and Illinois.. The largest tributary to the Teays River was the Old Kentucky River, which extended from southern Kentucky through Frankfort and subsequently flowed northeast, meeting other tributaries and eventually joining the Teays.
The Last Glacial Period (LGP), also known as the Last glacial cycle, occurred from the end of the Last Interglacial to the beginning of the Holocene, c. 115,000 – c. 11,700 years ago, and thus corresponds to most of the timespan of the Late Pleistocene.
The Glaciated Allegheny Plateau is that portion of the Allegheny Plateau that lies within the area covered by the last glaciation. As a result, this area of the Allegheny Plateau has lower relief and gentler slopes than the relatively rugged Unglaciated Allegheny Plateau. In general, the glaciated lies to the north and west of the unglaciated, and forms an arc in northeastern to southeastern Ohio lying between the glacial till plains and the Unglaciated Allegheny Plateau. The Glaciated Allegheny Plateau extends into a belt of southern New York State and the central Susquehanna River basin.
There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.
The Anglian Stage is the name used in the British Isles for a middle Pleistocene glaciation. It precedes the Hoxnian Stage and follows the Cromerian Stage in the British Isles. It correlates to Marine Isotope Stage 12, which started about 478,000 years ago and ended about 424,000 years ago.
The Cromerian Stage or Cromerian Complex, also called the Cromerian, is a stage in the Pleistocene glacial history of north-western Europe, mostly occurring more than half a million years ago. It is named after the East Anglian town of Cromer in Great Britain where interglacial deposits that accumulated during part of this stage were first discovered. The stratotype for this interglacial is the Cromer Forest Bed situated at the bottom of the coastal cliff near West Runton. The Cromerian stage preceded the Anglian and Elsterian glacials and show an absence of glacial deposits in western Europe, which led to the historical terms Cromerian interglacial and the Cromerian warm period. It is now known that the Cromerian consisted of multiple glacial and interglacial periods.
The Hoxnian Stage was a middle Pleistocene stage of the geological history of the British Isles. It was an interglacial which preceded the Wolstonian Stage and followed the Anglian Stage. It is equivalent to Marine Isotope Stage 11. Marine Isotope Stage 11 started 424,000 years ago and ended 374,000 years ago. The Hoxnian is divided into sub-stages Ho I to Ho IV. It is likely equivalent to the Holstein Interglacial in Central Europe.
The Wolstonian Stage is a middle Pleistocene stage of the geological history of Earth from approximately 374,000 until 130,000 years ago. It precedes the Last Interglacial and follows the Hoxnian Stage in the British Isles.
The Illinoian Stage is the name used by Quaternary geologists in North America to designate the Penultimate Glacial Period c.191,000 to c.130,000 years ago, during the late Middle Pleistocene (Chibanian), when sediments comprising the Illinoian Glacial Lobe were deposited. It precedes the Sangamonian Stage and follows the Pre-Illinoian Stage in North America. The Illinoian Stage is defined as the period of geologic time during which the glacial tills and outwash, which comprise the bulk of the Glasford Formation, accumulated to create the Illinoian Glacial Lobe.
The Yarmouthian stage and the Yarmouth Interglacial were part of a now-obsolete geologic timescale of the early Quaternary of North America.
The Beestonian Stage is an early Pleistocene stage in the geological history of the British Isles. It is named after Beeston Cliffs near West Runton in Norfolk where deposits from this stage are preserved.
The Pastonian interglacial, now called the Pastonian Stage, is the name for an early or middle Pleistocene stage of geological history in the British Isles. It precedes the Beestonian Stage and follows the Pre-Pastonian Stage. Unfortunately the precise age of this stage cannot yet be defined in terms of absolute dating or MIS stages. The Pre-Pastonian Stage is equivalent to the Tiglian C5-6 Stage of Europe and the Pre-Illinoian I glaciation of the early Pre-Illinoian Stage of North America.
The Pre-Pastonian Stage or Baventian Stage, is the name for an early Pleistocene stage of geological history in the British Isles. It precedes the Pastonian Stage and follows the Bramertonian Stage. This stage ended 1.806 Ma at the end of Marine Isotope Stage 65. It is not currently known when this stage started. The Pre-Pastonian Stage is equivalent to the Tiglian C4c Stage of Europe and the Pre-Illinoian J glaciation of the early Pre-Illinoian Stage of North America.
The Bull Lake glaciation is the name of a glacial period in North America that is part of the Quaternary Ice Age. The Bull Lake glaciation began about 200,000 years ago and ended about 130,000 years ago, and was concurrent with the Illinoian Stage of the Quaternary Ice Age. There is disagreement over these time frames, however, and further research is necessary.
Marine isotope stages (MIS), marine oxygen-isotope stages, or oxygen isotope stages (OIS), are alternating warm and cool periods in the Earth's paleoclimate, deduced from oxygen isotope data derived from deep sea core samples. Working backwards from the present, which is MIS 1 in the scale, stages with even numbers have high levels of oxygen-18 and represent cold glacial periods, while the odd-numbered stages are lows in the oxygen-18 figures, representing warm interglacial intervals. The data are derived from pollen and foraminifera (plankton) remains in drilled marine sediment cores, sapropels, and other data that reflect historic climate; these are called proxies.
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.
The Sangamonian Stage is the term used in North America to designate the Last Interglacial and depending on definition, part of the early Last Glacial Period, corresponding to Marine Isotope Stage 5. While often historically considered equivalent in scope to MIS 5, it is now often used in a more narrow sense to refer to the Last Interglacial only. It preceded the Wisconsinan (Wisconsin) Stage and followed the Illinoian Stage in North America.
References
- ↑ Flint, R.F., 1957, Glacial Geology and the Pleistocene Epoch. John Wiley & Sons, New York. 553 p. New York
- 1 2 Aber, J.S., 1991, Glaciations of Kansas. Boreas. vol. 20, no. 4,pp. 297–314
- 1 2 3 Roy, M., P.U. Clark, R.W. Barendregt, J.R., Glasmann, and R.J. Enkin, 2004, Glacial stratigraphy and paleomagnetism of late Cenozoic deposits of the north-central United States Archived 2018-09-28 at the Wayback Machine , PDF version, 1.2 MB. Geological Society of America Bulletin, vol. 116, no. 1–2; pp. 30–41; doi : 10.1130/B25325.1
- 1 2 3 Hallberg, G.R., 1986, Pre-Wisconsin glacial stratigraphy of the Central Plains region in Iowa, Nebraska, Kansas, and Missouri, Quaternary Science Reviews. vol. 5, pp. 11–15.
- ↑ Boellstorff, J., 1978a, Chronology of some Late Cenozoic deposits from the central United States and the Ice Ages.Transactions of the Nebraska Academy of Science. vol 6, pp. 35–49
- ↑ Boellstorff, J., 1978b, North American Pleistocene stages reconsidered in the light of probable Pliocene-Pleistocene continental glaciation. Science. vol. 202, pp. 305–307.
- ↑ Easterbrook, D.J., and J. Boellstorff, 1984, Paleomagnetism and Chronology of Early Pleistocene Tills in the Central United States. in W.C. Mahaney, ed., pp. 73–90. Correlation of Quaternary Chronologies. Norwich, United Kingdom, Geo Books.
- 1 2 Richmond, G.M. and D.S. Fullerton, 1986, Summation of Quaternary glaciations in the United States of America. Quaternary Science Reviews. vol. 5, pp. 183–196.
