Toward identifying potential causes for stratigraphic change in subtropical to tropical Laurentia during the Mohawkian (early Late Ordovician)

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Numerical models of the ocean-climate system indicate that during the early Late Ordovician, water from the higher southern latitudes flowed north toward the equator. The cold-water masses welled up into and penetrated the epicontinental sea of Laurentia. The "cold-water conditions" existed despite high levels of pCO 2 (∼15× preindustrial atmospheric levels) and did not necessarily indicate the onset of glaciation during the early Late Ordovician; rather the cold-water conditions may indicate the onset of a cooling event that plunged the Ordovician Earth system toward icehouse conditions that would lead later to the end-Ordovician (Hirnantian) glaciation. Furthermore, the observed distribution of cold-water masses across the southeastern margin of Laurentia is consistent with the interpretation that a cold-water event caused a regional extinction in the Mohawkian of eastern Laurentia. © 2010 The Geological Society of America. All rights reserved.

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Special Paper of the Geological Society of America

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