1 Exceptional Biotas and Fossil Preservation in the Southeast

Thursday, 17 March 2005
8:00 AM - 12:40 PM

TERRESTRIAL FAUNA AND FLORA OF THE INGERSOLL SHALE: AN UPPER CRETACEOUS KONSERVAT-LAGERSTÄTTE, EUTAW FORMATION, EASTERN ALABAMA

Paper number: 1-4
Program: SYMPOSIA SESSIONS
Time: 8:50 AM – 9:10 AM

Authors

Abstract

The recently discovered Ingersoll shale lens in Russell County, Alabama, is the only terrestrial Upper Cretaceous Lagerstätte known in the southeastern Coastal Plain. This ~80-cm-thick, carbonaceous clay-shale lens contains a terrestrial fauna and flora of Santonian age, including fossils of plants, probable fungi, insects, chelicerates, theropod feathers and anomalous structures which resemble fish scales, branchiopod carapaces and/or ammonite aptychi. The dominant mode of fossil preservation is carbonization with compression. Preliminary investigation of the microstratigraphy within the shale reveals tidal laminations, and all of the evidence thus far suggests this konservat-Lagerstätte was deposited in a restricted tidal creek of an estuary.

Three theropod feathers have been discovered in the deposit, with the size of the feathers suggesting an avian theropod or a small maniraptoran such as a dromaeosaur. Possible theropod eggshell fragments have also been discovered in association with the feathers. The most common fossils within this Lagerstätte are angiosperm leaves such as Manihotites georgiana, preserved as carbonized compressions. Most gymnosperm seeds and cones are found partially pyritized and preserved in three dimensions. Amber has been found with inclusions tentatively identified as fungal hyphae. Terrestrial arthropod fossils in the Ingersoll shale include insect wings, possibly neuropteran or ephemeropteran, and chelicerate and blattodean fragments. The spectacular preservation of fossils in this Lagerstätte may have been caused by rapid burial and salinity changes, via tidal pumping, within an estuarine environment.