Gsa 2014 - Trilobite Abstracts

[piranha]

Two abstracts on the trilobites Ampyxina and Australosutura, from the upcoming GSA Southeastern Section annual meeting in Blacksburg, Virginia.

Southeastern Section - 63rd Annual Meeting (10–11 April 2014)

 

Paper No. 42-9 - Presentation Time: 1:00 PM-5:00 PM

 

NEW FINDINGS ON AN ORDOVICIAN TRILOBITE ASSEMBLAGE FROM SOUTHWEST ROANOKE COUNTY, VA: A GEOMETRIC MORPHOMETRIC STUDY OF AMPYXINA POWELLI

MEYER, Michael and HOWARD, Aaron Stuart, Geosciences and Natural Resources, Western Carolina University, Stillwell Hall, Cullowhee, NC 28723

 

Ampyxina powelli is a small (~1 cm long) and rare species of trilobite whose evolutionary connections and developmental stages to other ‘related’ trilobites are relatively unknown. This species has a rather limited range, and as a result, has been the subject to very few studies in the last forty years. Recently, one of the few localities where A. powelli has been found, the Tucker Farmhouse locality in southwest Roanoke County, VA, is again being sampled and analyzed. To better understand A. powelli’s evolutionary placement within Trilobita, and its developmental history, specimens have been analyzed using advanced morphometric and statistical techniques. Additionally, newly found taxa (including graptolites, gastropods, and Tentaculites) at the Tucker Farmhouse locality will be combined with the morphologic trilobite findings, contributing to our understanding of this region’s local Ordovician paleoecology.

Paper No. 42-10 - Presentation Time: 1:00 PM-5:00 PM

 

FAUNA FROM A WAULSORTIAN-LIKE MOUND IN THE FORT PAYNE FORMATION (LOWER MISSISSIPPIAN) OF TENNESSEE

BLACKBURN, Bryan D. and ROBERSON, Randal Philip, Cookeville, TN 38501

 

A new road cut along TN-52 has exposed a Waulsortian-like mound just east of Celina, TN at the base of the Fort Payne Formation. The exposed part of the mound is approximately 19m in height and 50m in width. At the west end of the outcrop the mound overlies some 15cm of non-fossiliferous, gray-green shale with phosphate nodules interpreted to represent the Maury Shale of Kinderhookian age. The Maury is in sharp contact with the underlying Chattanooga Shale. The mound is composed of three distinct geometric bodies. The lowest body is a geometrically complex shale unit with three distinct crests and flanks that apparently pinch out laterally into shale of the Maury. The middle body is a complex of several carbonate beds that pinch and swell over the lower clastic body, and thin laterally to the west into two thin (7cm and 23 cm) off mound carbonate beds. The upper mound body is fine-grained, greenish-gray shale that comprises about 50 percent of the total mound thickness. It is thickest over the middle of the mound and thins away from the mound crest to the east and west where the outcrop ends. The lower and upper clastic bodies have yielded a diverse fauna that includes articulate brachiopods, cryptostome bryozoans, fenestrate bryozoans, crinoids, bivalves, possible sponge spicules, trilobites, ostracodes, and solitary rugose corals, approximately in decreasing order of abundance. Cephalons and pygidia from the trilobites so far recovered belong to a single species of the genus Australosutura. The presence of Australosutura is important because it is a cosmopolitan genus that has been reported from Australia, Argentina, Belgium and both western and central United States. Previous authors have interpreted Australosutura to represent off-shelf, deep water marine environments. Cryptostome bryozoans have also been strongly associated with the deeper end of European Waulsortian phases by Lees. These both support an interpretation of relatively deep water environments for the Tennessee mound.