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The breakup of Pangea and its impact on climate: Consequences of Variscan-Alleghanide orogenic collapse

By
Warren Manspeizer
Warren Manspeizer
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Published:
January 01, 1994

The breakup of Pangea in the central Atlantic occurred at a time of worldwide plate reorganization, embracing both the terminal phases of Pangean consolidation and the early phases of Pangean extension. The breakup developed along the thickened and highly elevated Variscan-Alieghanian orogen that was the site of Late Paleozoic polyphase deformation, which ultimately led to the formation of Late Paleozoic, late orogenic, wrench-formed basins. These late orogenic basins of the northern Appalachians and Morocco may have formed by tectonic escape as the collision of Gondwana and Laurasia forced the Hercynian-European plate northeast along major dextral shears.

Fission-track and isotopic data indicate that the subsequent breakup of Pangea during the Triassic was accompanied by continued northwest plate convergence in the lower crust and by large-scale vertical uplift and southeast extension in the upper crust. It is postulated that as the crust thickened beneath the leading edge of the Alleghanian orogen, topographic elevations increased so as to provide increased vertical stress needed to drive the extension. As these events were concurrent with subduction of the paleotethys plate, through the suturing of Cimmeria to Laurasia, I propose that orogenic collapse leading to the breakup may have been aided or induced by subduction rollback, initiating tectonic extrusion of a microplate bounded by the N40°-Kelvin and South Atlas fracture zone, which acted as a ridge-to-arc transform. The Late Triassic rift basins, in this view, formed along the western border of this easterwardly extruded microplate, whose detachment surface may have been composed of Carboniferous evaporites.

Breakup of the supercontinent during the Late Triassic–Early Jurassic also had major consequences on Pangean climates, as Early Mesozoic climates were substantially modified by changes in continentality, oceanography, orography, and igneous activity. In contrast to Pangean climates marked by glaciation and aridity, Late Triassic climates were markedly more equitable and characterized by more humid conditions over much of the world. The changing conditions also profoundly affected the biota, as Late Triassic strata record one of the five greatest episodes of mass extinctions in the history of the earth.

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GSA Special Papers

Pangea: Paleoclimate, Tectonics, and Sedimentation During Accretion, Zenith, and Breakup of a Supercontinent

George O. Klein
George O. Klein
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Geological Society of America
Volume
288
ISBN print:
9780813722887
Publication date:
January 01, 1994

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