118 Paleontology 1: Diversity, Extinction, and Origination

Monday, 26 September 2016
1:30 PM - 5:30 PM
Mile High Ballroom 4C

WALCOTT’S SOUTHERN APPALACHIAN TRILOBITE LOCALITIES REDISCOVERED – LOWER CAMBRIAN, UPPER CHILHOWEE GROUP, “NEVADELLA” ZONE

Paper number: 118-3
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

After reconnaissance field work for USGS mapping in the 1890s, C.D. Walcott, and later, A. Keith commented on, but did not illustrate, describe, or collect (reposit) trilobite fragments from the Murray Formation of Chilhowee Mountain in eastern Tennessee (Walcott, 1890; Keith 1895). Walcott later commented on but did not illustrate or describe, moldic specimens of a trilobite from the upper Antietam Formation, Chilhowee Group, near Natural Bridge in central Virginia, which he compared to Olenellus thompsoni (Walcott 1892). Resser (1938) illustrated but did not describe one of Walcott’s four poorly preserved Virginia specimens as Olenellus sp. The totality of this record has long and repeatedly been cited as evidence for correlation of the upper Chilhowee Group in the southern Appalachians as early Cambrian, ‘Bonnia-Olenellus’ Zone.

Since at least the 1940’s, workers have attempted to relocate Walcott and Keith’s Chilhowee Mountain trilobite localities. Efforts have been confounded by poor initial documentation, historical changes to geographic landmarks, and poor exposure due to heavy vegetation. In addition, as a result of a fault (apparently unrecognized by Walcott and Keith) there has long been debate whether the TN locality was or was not the stratigraphic equivalent of the VA locality within the upper Chilhowee Gp. The moldic fossil fragments from upper Antietam of VA have been recognized by many field geologists; however, they have not been formally described.

A multi-year effort to relocate and collect from Walcott’s southern Appalachian trilobite localities has yielded new, well-preserved nevadiid trilobite specimens from the Murray Shale (mid-upper Chilhowee Gp.) in the region of Walcott’s original locality. The site yields abundant well preserved hyolithids and other arthropod? specimens (Murray fauna). In addition, although poorly preserved, the stratigraphically younger, moldic fauna present at the top of the Chilhowee Group (Helenmode fauna) can be found across southern Virginia and into northeastern Tennessee. Efforts to collect, describe and integrate results with other early Cambrian sites are ongoing.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-280562

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