Paleozoic climate

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The Early Cambrian climate was probably moderate at first, becoming warmer over the course of the Cambrian, as the second-greatest sustained sea level rise in the Phanerozoic got under way.  However, as if to offset this trend, Gondwana moved south with considerable speed, so that, in Ordovician time, Most of West Gondwana (Africa and South America) lay directly over the South Pole.  The Early Paleozoic climate was also strongly zonal, with the result that the "climate", in an abstract sense became warmer, but the living space of most organisms of the time -- the continental shelf marine environment -- became steadily colder.  However, Baltica (Northern Europe and Russia) and Laurentia (eastern North America and Greenland) remained in the tropical zone, while China and Australia lay in waters which were at least temperate.  The Early Paleozoic ended, rather abruptly, with the short, but apparently severe, Late Ordovician Ice Age.  This cold spell caused the second-greatest mass extinction of Phanerozoic time.   
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The Early Cambrian climate was probably moderate at first, becoming warmer over the course of the Cambrian, as the second-greatest sustained sea level rise in the Phanerozoic got under way.  However, as if to offset this trend, Gondwana moved south with considerable speed, so that by the [[Ordovician]] west Gondwana (Africa and South America) was centered near  the South Pole.  The Early Paleozoic climate was also strongly zonal, with the result that the "climate", in an abstract sense became warmer, but the living space of most organisms of the time -- the continental shelf marine environment -- became steadily colder.  However, Baltica (Northern Europe and Russia) and Laurentia (eastern North America and Greenland) remained in the tropical zone, while China and Australia lay in waters which were at least temperate.  The Early Paleozoic ended, rather abruptly, with the short, but apparently severe, Late Ordovician Ice Age.  This cold spell caused the second-greatest mass extinction of Phanerozoic time.   
The Middle Paleozoic was a time of considerable stability.  Sea levels had dropped coincident with the Ice Age, but slowly recovered over the course of the Silurian and Devonian.  The slow merger of Baltica and Laurentia, and the northward movement of bits and pieces of Gondwana created numerous new regions of relatively warm, shallow sea floor.  As plants took hold on the continental margins, oxygen levels increased and carbon dioxide dropped, although much less dramatically.  The north-south temperature gradient also seems to have moderated, or metazoan life simply became hardier, or both.  At any event, the far southern continental margins of Antarctica and West Gondwana became increasingly less barren.  The Devonian ended with a series of turnover pulses which killed off much of Middle Paleozoic vertebrate life, without noticeably reducing species diversity overall.
The Middle Paleozoic was a time of considerable stability.  Sea levels had dropped coincident with the Ice Age, but slowly recovered over the course of the Silurian and Devonian.  The slow merger of Baltica and Laurentia, and the northward movement of bits and pieces of Gondwana created numerous new regions of relatively warm, shallow sea floor.  As plants took hold on the continental margins, oxygen levels increased and carbon dioxide dropped, although much less dramatically.  The north-south temperature gradient also seems to have moderated, or metazoan life simply became hardier, or both.  At any event, the far southern continental margins of Antarctica and West Gondwana became increasingly less barren.  The Devonian ended with a series of turnover pulses which killed off much of Middle Paleozoic vertebrate life, without noticeably reducing species diversity overall.

Revision as of 18:29, 3 October 2006

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