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This digital document is a journal article from Palaeogeography, Palaeoclimatology, Palaeoecology, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

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We performed sensitivity experiments with the global climate model GENESIS on two stages of the Upper Ordovician (Caradocian, ~454 Ma; Ashgillian, ~446 Ma) under a range of atmospheric pCO"2 values (8-18x PAL; Pre-industrial Atmospheric Level), high and low sea level, and two values of poleward ocean heat transport in order to determine the importance of these variables on global cooling. We then coupled a three-dimensional ice sheet model to the global climate model in order to investigate the necessary boundary conditions for ice sheet formation. All simulations with a high sea level and normal heat transport remain free of ice sheets, even with pCO"2 levels as low as 8x PAL. In the Caradocian simulations, ice sheets form in three scenarios: (1) with pCO"2 of 8x PAL and a low sea level and normal poleward ocean heat transport, (2) with pCO"2 of 8x PAL and a high sea level and reduced (50% of normal) poleward ocean heat transport, and (3) with pCO"2 of 15x PAL and a low sea level and reduced poleward ocean heat transport. In the Ashgillian simulations, ice sheets form in only two scenarios: (1) with pCO"2 of 8x PAL and a low sea level and normal poleward ocean heat transport, or (2) with pCO"2 of 8x PAL and a high sea level and reduced poleward ocean heat transport. The ice sheets in the Ashgillian experiments are larger and thicker than the ice sheets in the Caradocian simulations because the southward movement of Gondwana increased land area in the higher southern latitudes where ice sheets could grow. The threshold for glaciation under Ashgillian paleogeography is 8x PAL and either a low sea level (exposed shelves) or a reduced poleward ocean heat transport. While the paleogeographic evolution and a drop in pCO"2 during the Late Ordovician cooled the global climate, changes in additional factors were required to initiate ice sheet formation, such as a drop in sea level, a reduction in poleward ocean heat transport, or a combination of both. ... Read more

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Chapters: Messinian Salinity Crisis. Source: Wikipedia. Pages: 91. Not illustrated. Free updates online. Purchase includes a free trial membership in the publisher's book club where you can select from more than a million books without charge. Excerpt: The Messinian Salinity Crisis, also referred to as the Messinian Event, and in its latest stage as the Lago Mare event, was a geological event during which the Mediterranean Sea went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene epoch, from 5.96 to 5.33 Ma (million years ago). Charles Mayer-Eymar (1826-1907) of Zurich studied fossils between gypsum-bearing, brackish and freshwater sediment layers and identified them as having been deposited just before the end of the Miocene Epoch. In 1867 he named the period the Messinian, for the region of Messina, Sicily. Since then salt-bearing and gypsum-bearing evaporite layers in many Mediterranean countries have been dated to that period. The Messinian salt deposits that have been pushed up onto land by tectonic activity in places like Messina (Sicily), northeast Libya, Italy, and southern Spain have been described since the 19th century and it is then that the salinity crisis theory started to be developed. In 1961, seismic surveying of the Mediterranean basin revealed a geological feature some 100-200 metres below the seafloor. This feature, dubbed the M reflector, closely followed the contours of the present seafloor, suggesting that it was laid down evenly and consistently at some point in the past. The origin of this layer was largely interpreted as related to salt deposition. However, different interpretations were proposed for the age of salt deposition and its disposition. Using new and high quality seismic data acquired in the Mediterranean Basin in 1970, Auzende et al. (1971) proposed that the salt was late Miocene in age, following earlier suggestions fr...More: http://booksllc.net/?id=1870896 ... Read more

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This digital document is an article from Geoscience Canada, published by Geological Association of Canada on March 1, 2008. The length of the article is 1655 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available immediately after purchase. You can view it with any web browser.

Citation Details
Title: Paleogeography of the North American Cordillera: Evidence For and Against Large-Scale Displacements.(Book review)
Author: JoAnne Nelson
Publication: Geoscience Canada (Magazine/Journal)
Date: March 1, 2008
Publisher: Geological Association of Canada
Volume: 35Issue: 1Page: 43(2)

Article Type: Book review

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Webster's bibliographic and event-based timelines are comprehensive in scope, covering virtually all topics, geographic locations and people. They do so from a linguistic point of view, and in the case of this book, the focus is on "Paleogeography," including when used in literature (e.g. all authors that might have Paleogeography in their name). As such, this book represents the largest compilation of timeline events associated with Paleogeography when it is used in proper noun form. Webster's timelines cover bibliographic citations, patented inventions, as well as non-conventional and alternative meanings which capture ambiguities in usage. These furthermore cover all parts of speech (possessive, institutional usage, geographic usage) and contexts, including pop culture, the arts, social sciences (linguistics, history, geography, economics, sociology, political science), business, computer science, literature, law, medicine, psychology, mathematics, chemistry, physics, biology and other physical sciences. This "data dump" results in a comprehensive set of entries for a bibliographic and/or event-based timeline on the proper name Paleogeography, since editorial decisions to include or exclude events is purely a linguistic process. The resulting entries are used under license or with permission, used under "fair use" conditions, used in agreement with the original authors, or are in the public domain. ... Read more