PALEOECOLOGY AND TAPHONOMY OF AN OSTRACODE FAUNA FROM THE LANEY MEMBER, GREEN RIVER FORMATION, WYOMING

The Eocene Green River Formation contains one of the most famous Konservat Lagerstätten in the world. While it has been extensively studied with respect to its petrology, sedimentology, tectonic features and fossil fish, few studies have examined the invertebrates, particularly the ostracodes of this well preserved fauna. Detailed stratigraphic sections were measured and described from Gosiute basin and were sampled for ostracodes at the centimeter scale. Ostracodes were recovered from 15 out of 34 samples within a 28 meter section of the Laney Member of the Green River Formation. The ostracodes include members of the species: Hemicyprinotus watsonensis, Potamocypris williamsi, Candona pagei, Cypridea bisulcata, Metacypris paracordata, and Procyprois ravenridgensis. Of these six species, three are plant dwellers, two are mud dwellers and one is nektonic. These different ecologies are reflected in the facies in which the ostracodes are preserved, representing changing physical and chemical conditions through time in this balanced filled lake. In addition to documenting the diversity of the ostracodes throughout the Laney Member, we examined the preservational history of the various ostracode communities. Most ostracodes were found within the organic and carbonate rich layers, with the exception of two ostracode coquinas that occur within the section. In most shale layers, the ostracodes appear to have sheared along bedding planes, indicating post burial deformation. In addition, these unaltered shells appear flattened and compressed. In the coquinas, the valves are separated and there is no apparent orientation within the beds, possibly representing deflation surfaces along the lake margin. Thus, ostracodes recovered from the Laney Member of the Green River Formation may track environmental changes due to lake level fluctuations. Their preservational pathways may lead to further information regarding lake stability and changes in lake chemistry through time.