A HIGH RESOLUTION ARCHIVE OF LAKE DYNAMICS PRESERVED IN THE STROMATOLITES OF THE LANEY MEMBER OF THE GREEN RIVER FORMATION (EOCENE)

Stromatolites provide a unique situation for the preservation of a high resolution sedimentary record in the near-shore lacustrine environment. Stromatolites are the only laminated phenomenon preserved in the near-shore environment of Lake Gosiute. Potentially, they are highly sensitive to slight changes in lake dynamics and could provide a high-resolution sedimentary record that may not be recorded in the less sensitive, lake-center sediments. The stromatolites of the Laney Member of the Green River Formation (Eocene) are in laterally continuous units that can be correlated over distances exceeding 20 km. They can be traced from environments that formed in very shallow water to areas that formed in deeper water. Unlike many lacustrine stromatolites that form in relatively narrow, sublittoral zones, these stromatolites apparently grew contemporaneously across the very low gradient of the lake margin. Changes in stromatolite laminae, microstructure, and macrostructure are observed that correspond to changing environmental conditions. Subsets of laminae within the stromatolites can be traced across large distances. This allows for the comparison of the vertical patterns within the stromatolites as well as the lateral changes. Sampling individual sets of laminae across stromatolites provides a controlled situation with which to study lateral changes in isotopic and minerologic composition of the unit. Vertical changes in the minerologic and isotopic signal in the stromatolites can be compared to provide a high resolution record of lake dynamics during the time the stromatolites grew. The sedimentary record provided by the stromatolites contributes to a more complete and detailed understanding of the conditions under which stromatolites form, as well as the paleoenvironmental and paleoclimatic conditions which contributed to the lake’s history.