SUBSURFACE IMAGING OF THE SNOWPLOW, LAKE BONNEVILLE, UTAH

Lake Bonneville was the largest of the late Pleistocene lakes in the Great Basin of western North America. The lake was hydrographically closed during its transgressive and regressive phases and therefore has well-preserved shorelines and deposits throughout the lake basin. A prominent geomorphic feature called "the Snowplow" by G.K. Gilbert displays characteristics that are typical of many of the shorezone landforms of Lake Bonneville. The Snowplow is located in the central part of the Bonneville basin. Gilbert noted the resemblance of the landform's shape to that of a snowplow, and thus gave it that name. In understanding the origin of the Snowplow it is important to remember that Lake Bonneville was hydrographically closed during its transgressive phase. The Snowplow consists of a stack of V-shaped gravel barriers with the lower-altitude V-shaped barriers being older than the higher ones. The exact mechanisms involved in the formation of the V shapes are not fully understood, although it is clear that longshore transport of gravel was involved.

To better understand the subsurface stratigraphy of the Snowplow, a ground penetrating radar (GPR) survey was undertaken. A Sensors and Software pulseEKKO 100 GPR system with 50, 100 and 200 MHz antennae was used to collect transects on several levels of the Snowplow. The processed and interpreted stratigraphy show progradation and aggradation of the coastal sedimentary deposits. The research continues on Derald G. Smith’s earlier GPR work along the Bonneville shorelines, and also provides analogues for modern lacustrine and marine coasts.