Southeastern Section - 50th Annual Meeting (April 5-6, 2001)

Paper No. 0
Presentation Time: 1:00 PM-4:00 PM

PALEOECOLOGY AND TAPHONOMY OF TENTACULITIDS FROM THE BIRDSONG SHALE MEMBER OF THE ROSS FORMATION (DEVONIAN), WESTERN TENNESSEE


GIBSON, Michael A. and DAHNKE, William F., Univ Tennessee–Martin, 215 Joseph E. Johnson EPS Bldg, Martin, TN 38238-5039, wilfdahn@mars.utm.edu

The Birdsong Shale Member (Lower Devonian, Lochkov) is the shale-dominated portion (~20m thick) of a mixed carbonate-siliciclastic sequence exposed in a north-south trending outcrop belt in western Tennessee. Previous studies have determined that the mixed nature of the sequence results from a combination of storm winnowing and obrution on a level bottom seafloor. While most of the fauna is dominated by epibiont-rich brachiopods, bryozoans, echinoderms, and trilobites, a 1.2 meter section of interbedded thin packstone/wackestone and shale preserved an unusually rich accumulation (over 1000 per 10 m2) of the tentaculid Tentaculites aculus at a single locality. At least 15 different packstone/shale interbeds occur suggesting alternating conditions at this locality; however, the tentaculid bed is not traceable to other areas. Two scenarios to explain the accumulation are examined. Either the tentaculid accumulation is a series of mass kills that occurred in the same general region repeatedly (due to some form of endemism?) over a protracted interval of time or the entire 1.2 meter accumulation is one mass kill event, which suggests that much of the Birdsong itself may be a short-term sediment accumulation.