Print this pageAbstract: Causality and Timing in North American Transgression-Regression Cycle from Cambrian to Present
Epicontinental marine transgressions and regressions involve either eustatic changes in sea level, with vertical ranges of a few hundred meters at most, or epeirogenic processes with crustal uplifts and depressions relative to sea level reaching several kilometers in many cases. Changes in the figure of the earth due to the secular decrease in the rate of rotation of the earth are considered to be the major cause of epeirogeny during the Paleozoic. Effects due to mantle convection and plate tectonics became dominant during the Mesozoic. Calculations show that the equatorial bulge decreased from 51.6 km at the beginning of the Cambrian to 23.0 km at the end of the Permian and to 21.3 km at present. In North America the adjustments took place in nine orogenic episodes or te tophases. These tectophases separate the 10 depophases each of which is represented by a depositional sequence consisting of equatorial and polar units separated by hinge lines located 35° from the equator. During most of the Paleozoic, North America was located south of the equator and the southern hinge line became the Transcontinental arch. The location of the hinge line permits precise location of the rotational pole independent of all paleomagnetic data.
AAPG Search and Discovery Article #90972©1976 AAPG-SEPM Annual Convention and Exhibition, New Orleans, LA