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Paper No. 46-3
Presentation Time: 9:00 AM-5:30 PM
TRANS-ATLANTIC KATIAN (UPPER ORDOVICIAN) δ13C CHEMOSTRATIGRAPHY AND ITS RELATIONS TO GRAPTOLITE AND CONODONT ZONES
In the global Katian Stage, which by definition extends from the base of the D. caudatus Graptolite Zone to the base of the N. extraordinarius Graptolite Zone, six chemostratigraphic excursions are currently recognized in North America, namely in ascending order the Guttenberg (GICE), Kope, Fairview, Waynesville, Whitewater, and Elkhorn excursions. In Baltoscandia the last three of these excursions are known as the Saunja, Moe, and Paroveja excursions. The North American Fairview excursion is still poorly documented in Baltoscandia, but the other excursions have proven to be quite useful for solving long-standing problems in trans-Atlantic correlations. For instance, the previously virtually unknown trans-Atlantic correlation of parts of the Katian is now established with a precision of a few meters. Recent work has shown that the GICE occurs in the D. caudatus and C. ruedemanni Graptolite Zones and the A. tvaerensis Conodont Zone; the Kope/Nabala is in the C. spiniferus and G. pygmaeus Graptolite Zones and the A. superbus Conodont Zone; the. Waynesville/Saunja excursion is in the A. manitoulinensis Graptolite Zone and the A. grandis Conodont Zone; the Whitewater/Moe excursion is in the D. complanatus Graptolite Zone and the A. ordovicicus Conodont Zone; and the Elkhorn/Paroveja excursion occurs in the P. pacificus Graptolite Zone and the uppermost A. ordovicicus Conodont Zone. All the chemostratigraphic excursions are now known from the Cincinnatiian Series in its reference area in Ohio and adjacent states. The usefulness of the Katian chemostratigraphy for solving long-standing statigraphic age problems is also illustrated by the occurrence of the Whitewater/Moe excursion in the lower part of the Great Basin Katian carbonate succession, which indicates an age no older than Richmondian. This is in agreement with the age of the early Richmondian transgression in Texas-New Mexico, Arizona, Oklahoma, and adjacent states.