Paper No. 66-18
Presentation Time: 2:00 PM-6:00 PM
AN INVESTIGATION OF PATTERNED GROUND IN THE BIG SMOKEY VALLEY, SOUTH-CENTRAL NEVADA
Patterned ground fundamentally arises as a mechanical response to a pattern in local and/or thermal regimes. While well documented in periglacial locations (e.g., the Arctic), patterned ground can develop in arid regions where it can also develop a variety of forms (e.g., polygons, stripes). In general, it will develop as a result of multigelation (cycles of freezing and thawing events) and associated frost heave. Such formation is not random and is distinct from mud crack formation or subaqueous sedimentation. As such, patterned ground has the potential to provide insight into the local and regional environmental processes which influence the evolution of desert landscapes. In this study, patterned ground was observed in a level area proximal to Oligocene-Miocene basalt flows in Big Smoky Valley, Nevada, at an elevation of ~1,950 m above sea level. Here, the region was characterized by polygons defined at their edges by clast-rich ridges. Physical samples were also collected to assist in the characterization of materials that define this area. Scanning electron microscopy (SEM) analysis was further utilized to determine the mineral composition, texture, etc. The observed polygons range from having 3 to 7 sides with a predominance of 5. Polygons varied from 5.1 cm to 20.3 cm in maximum width, with an average of 12.4 cm. Clasts were dominantly angular and composed of black basaltic rock and chert. 308 clasts from polygon ridges range in size from 5.3 mm to 47.4 mm in maximum length, with an average of 14.0 mm. Additionally, the minimum length varied from 2 mm to 29 mm, averaging 7.1 mm. Clast mass varied from 1.0 g to 50.61 g, averaging 1.68 g. Clast size measurements and mass data sets were unimodal and right-skewed toward smaller lengths and mass. Additional research into other occurrences and potential variances of patterned ground may provide insight into regional environmental conditions and contribute to our understanding of the processes associated with desert landscape evolution.