Great Basin Algorefrauds

Abstract

Great Basin algorefrauds reveal the effect of celestial cycles on global climate changes on Paleozoic rocks and more recently on Quaternary deposits associated with the beginning of the recent algorefraud. An algorefraud is a global warming cycle that is reflected in the rock record as transgressive sequence that overlies the top of a shallowing-upward sequence. Just as melting of the giant ice sheets that started at the end of Pleistocene glacial period have caused sea level to raise during the recent algorefraud so Devonian algorefrauds were likewise caused by global climate changes. Devonian algorefrauds are well exposed in the Upper Devonian Guilmette Formation carbonates of the Timpahute Range about 100 miles north of Las Vegas. Surface gamma ray logs, a field technique pioneered by the author to create gamma ray logs of outcrops that can easily be correlated with subsurface gamma ray logs, and detailed descriptions of the stratigraphic sequences were used to define and correlate 21 Devonian algorefrauds throughout much of the eastern Great Basin. An isopach map of all 21 algorefrauds reveals a Great Basin Devonian basin, larger than the Williston Basin, which had been modified by thrusting within the western Cordillera thrust belt. The correlation of the algorefrauds between thrust sheets provides a structural tool to help create restorable, balanced structural cross sections in the thrust belt. Algorefrauds in the Late Devonian of the Timpahute Range were interrupted by the Alamo impact event and resumed after the event.

AAPG Datapages/Search and Discovery Article #90266 © 2016 AAPG Pacific Section and Rocky Mountain Section Joint Meeting, Las Vegas, Nevada, October 2-5, 2016