CORRELATION OF THE LATE PLEISTOCENE “INTERMEADIATE” SHORELINES OF LAKE BONNEVILLE, U.S.A

Multiple transgressive shorelines of the late Pleistocene Lake Bonneville in northwestern Utah, USA have been identified between the altitudinal limits of the Bonneville and Provo levels and were named by the G.K. Gilbert as the “Intermediate” shorelines (1890). The chronologic record of these Intermediate shorelines is relatively unknown because they have not been correlated in the basin due to their individual altitudinal variations. The complexity of the altitudinal variations associated with the Intermediate shorelines has been attributed to differential hydro isostatic rebound patterns, differential wave energy patterns, and autogenic sedimentological processes related to an oscillating lake. In order to correlate the features locally and basin wide, modern GIS technologies are coupled with field investigations of the sedimentological and geomorphic patterns of the features. High resolution digital elevation models were utilized in a hydrostatic rebound model and then a potential wave energy model was developed by incorporating fetch and slope as proxies for wave energy. Both of these models, coupled with field investigations, are used to quantify factors that influence the development of shorelines in a complex lacustrine system. Six significant and multiple small Intermediate shorelines are correlated in the northwestern portion of the Bonneville basin (Hogup Mountains and Matlin Mountain) and within a southern arm of the basin (Wah Wah valley). Correlation of these shorelines allows a more accurate history of the shorelines and the basins climatic history to be determined. Correlating these Intermediate shorelines also has the potential to further aid in the understanding of how the lake may have responded to regional and/or global submillennial climatic shifts and how the basin may respond to these same type of climatic shifts in the future.