The Paleogeographic Atlas Mission (PGAP has existed as analysis enterprise at The University of Chicago since 1975 when Shell Oil provided preliminary funding to Alfred (Fred) M. Ziegler. Though detrital mica in these sandstones suggests distal orogenic detritus (Poulton et al., this volume, Chapter 18), these sands had been in all probability, for essentially the most half, derived from optimistic areas in the United States and the craton to the east.
The abundance of incised valley deposits suggests that the Moosebar/Clearwater transgression was extremely episodic and interrupted by periods of sea-degree lowstand and valley incisement (Putnam, 1982; James, 1985; Rosenthal, 1988; Wood and Hopkins, 1989).
Scholars in this area provide a paleogeographic reconstruction of volcanic regions, where the traditional course of sediment accumulation has been periodically interrupted by lava flows and deposits of large quantities of volcanic ash and different volcanic merchandise.
Strata of this interval consist primarily of thin, coarsening-upward successions of shales, siltstones and lenticular sandstones with regionally occurring thin limestones representing deposition in a low-energy, brackish, subaqueous surroundings (Finger, 1983; James, 1985).
The primary clear evidence of orogenic exercise is found in decrease Upper Jurassic strata, marked by the westerly derived sediments of the Passage Beds in …