1 Paleontology

Thursday, 10 April 2008
10:00 AM - 12:20 PM

NEW UPPER CAMBRIAN (APHELASPIS ZONE) TRILOBITE SITES IN THE CENTRAL CONASAUGA RIVER VALLEY, NORTH GEORGIA

Paper number: 1-2
Program: Technical Sessions
Time: 10:20 AM – 10:40 AM

Authors

Abstract

Middle and Upper Cambrian strata in the southeastern Appalachians (Tennessee to Alabama) comprise the Conasauga Formation (or Group). Heretofore, the youngest reported Conasauga beds in the Valley and Ridge Province of Georgia were of late-Middle Cambrian age (Bolaspidella Zone), located on the western state boundary in the valley of the Coosa River. Recent collecting in two sites in the Conasauga River Valley, significantly farther east in Gordon and Murray counties, reveals a diagnostic suite of trilobites from the Late Cambrian Aphelaspis Zone. This discovery is significant because the closest contemporaneous Late Cambrian beds are in eastern and central Alabama, suggesting that the Conasauga River Valley lies in a thrust sheet separate from the intervening Coosa River Valley. Additionally, these new sites represent the easternmost Late Cambrian strata in the southern Appalachians.

The trilobite assemblage includes the distinctive and globally-correlative agnostoid Glyptagnostus reticulatus angelini. Other trilobites firmly identified are Agnostus inexpectans and Aspidagnostus laevis. Collectively this assemblage is age-diagnostic for the Aphelaspis polymeroid trilobite zone. Ironically, the abundant polymeroid trilobites in the same collections are less confidently identified, but here tentatively placed in two species of Aphelaspis, including A. walcotti and one that appears to be new.