Abstract: Timing, Effects, and Causes of Reorganizations of the Plate Tectonic System
Jeffrey U. Kraus, David
B. Walsh, Christopher R. Scotese
We have analyzed the PALEOMAP plate tectonic model and determined the rate and direction of motion for the seven major plates (North America, South America, Europe, Africa, Asia, Australia, and Antarctica) over the last 180 m.y. Cretaceous and younger plate motions were compared to the Atlantic Ocean-Indian Ocean hot-spot reference frame. When plotting changes in rate and direction relative to the hot-spot reference frame, times of global plate reorganizations became apparent. Geologic evidence of global plate reorganizations include the emplacement of blueschist and ophiolite belts, as well as sequence stratigraphic boundaries that reflect tectonically driven changes in sea level. Plate reorganizations often coincide with major collisional and rifting events, such as the collision of the Cimmerian terranes in central Asia and the breakup of Gondwana.
The occurrence of numerous, non-periodic plate reorganizations has several implications. First, the cause of these reorganizations seems to be lithospheric, rather than mantle driven. That is to say, changes in plate geometry due to ridge subduction, rifting, continental collision, trench initiation, and breakup of supercontinents is the major forcing factor in the plate tectonic system. Because slab pull is responsible for these events, it follows that slab pull must be the dominant mechanism driving the system. Another implication is that changes in sea level over spans of a few million years may be primarily tectonically driven. Therefore, sea level may be responding on a long term to changes in sea-floor spreading rates and on a short term to changes at subduction zones.
AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994