Abstract by Jason Klimek
Organic carbon analysis of the Long Ridge bar set, Delta UT.
The Pleistocene Lake Bonneville shoreline of central and eastern Utah is marked by prominent sand and gravel benches that were stranded during lake recession. The Long Ridge beach bar set is an echelon series of Pleistocene gravel bars that form a large cuspate foreland. The bars consist of highly sorted, well-rounded cobbles and are separated by deposits of very light gray silty muds. Bucket auger boreholes reveal that the depth of fine-grained inter-bar sediments shallows from north to south. RockEval whole-rock pyrolysis analysis of sediment samples obtained from the boreholes reveals a series of oscillations in organic carbon content. Correlation of organic carbon content in borehole samples from the bar set and the nearby lake bed reveals that there was continued deposition of fine-grained sediment on the lake bed after the abandonment of the lowest gravel bar. These factors, along with the relative height of the gravel bars, provide additional insight into the recession of Lake Bonneville and the paleoclimatic conditions at the time.