CARBON ISOTOPIC CHEMOSTRATIGRAPHIC RECORD OF THE UPPER FAMENNIAN, SOUTHWEST U.S. AND WEST-CENTRAL GERMANY

Carbon isotopic chemostratigraphic curves were constructed for three sections in west-central Germany, and in several sections in the western U.S. The strata in each case span equivalent conodont zones of the Late Famennian, ranging from the Latest marginifera Zone, through the trachytera, postera, and Middle expansa Zones.  The data indicate that Layte Devonian regional and global events that are well recorded in Germany are also present in western U.S. deposits. Two regionally extensive black shale layers in Germany are associated with carbon isotopic anomalies. A negative excursion associated with the Annulata Shale at the base of the Lower postera Zone also exists in Glenwood Canyon, CO. A positive excursion associated with the Dasberg Shale in Germany at the Lower expansa Zone – Middle expansa Zone boundary is detected in sections in Colorado and at Pinyon Peak, UT. In Utah, this change occurs at a formation boundary, and is associated with microkarst and a quartz sandstone bed that interrupts a nearly continuous section of dolostone. The sandstone bed rests on an unconformity and indicates that a relative sea level change was associated with this event of faunal turnover in this part of Laurentia. Finally, one of the most prominent events of the Late Famennian (Middle to Upper praesulcata Zone), the Hangenberg Event, is associated with sea level change, black shale deposition and a large positive carbon iosotopic excursion. Although this event is absent in most sections in North America, it appears to be present in strata in Colorado. The recognition of the chemostratigraphic signals of Late Devonian events in both Germany and southwest U.S. improves correlation of strata, helps in the recognition of unconformities, and allows for reconstruction of global oceanographic events.