Tertiary lakebeds of the east-central Conger Range
Benjamin Bradley
The data for my senior research was gathered in west central Utah during the summer of 1998. I spent six weeks in the Conger Range, a western spur of the Confusion Range, researching the deformation of the Tertiary Lakebeds. The purpose of my research is to determine if small scale deformation in the Tertiary Lakebeds mimics the large scale geologic processes that have affected the Confusion Range.
The structures of the east-central Conger Range are deformed by two periods of extension. The first being classified as low angle, and occurring during the late Mesozoic to early Cenozoic, and the second being classified as high angle, and occurring during the middle Miocene. Low angle faults were responsible for most of the lateral displacement of the province, while the high angle normal faulting was responsible for the present Basin and Range structures. The Tertiary lakebeds where I did my research are deformed directly and indirectly by both modes of faulting. Therefore, the lakebeds display small scale deformation that mimics the large scale processes which have deformed the entire region. A listric fault bounding the west side of the Tertiary lakebeds joins the Snake Range detachment at depth, and therefore successive movement on the detachment affects the listric fault stemming from the main fault. It is this detachment which has caused the Tertiary unit to be folded along the fault in my research area. The Basin and Range high angle faulting affected the Tertiary lakebeds in a different manner. As the horst and graben topography was forming, it allowed for lacustrine sediments to be preserved in the basins, and debris flows coming from newly uplifted regions drained into the lake-bottom leaving conglomerates which were deposited directly onto carbonate lakebed deposits. All of the Tertiary units in the Conger Range are located in grabens and, therefore, have been effected by both low angle and high angle faulting.
Research projects on similar Tertiary units throughout the Basin and Range are few and far between; therefore it is difficult to correlate my findings with those of others. There are discussions about the formation of these sediments, but interpretations of the small scale deformation within them are virtually nonexistent. However, it is clear that more work needs to be done on these units, as they hold much more information than first meets the eye.