Cap carbonate and diamictite facies relationships in the Neoproterozoic Kingston Peak Formation, Death Valley, California, USA
|Category||Paleontology and Stratigraphy|
|Location||International Geological Congress,oslo 2008|
|Author||Partin, Camille; Kennedy, Martin|
|Holding Date||10 September 2008|
The Neoproterozoic Kingston Peak Formation includes two laterally persistent diamictite bearing intervals each sharply overlain by a carbonate unit. The older diamictite (Surprise) is overlain by a limestone unit, whereas the younger diamictite (Wildrose) is overlain by a dolomite unit, similar to Neoproterozoic glacial successions in many basins on other continents. Continuous exposure on steep canyon walls in the southern Panamint Range, California, shows strong stratigraphic contrast between the lower diamictite-carbonate couplet (Surprise Member and Sourdough Limestone) and the upper couplet (Wildrose diamictite and Noonday Dolomite) with the upper couplet showing a continuous lateral thickness. The Surprise diamictite, by contrast, shows rapid thickness changes in response to localized topography related to faulting. The Surprise is thickest basinward and thins onto Proterozoic crystalline basement horst-blocks, and overlaps older basin fill to rest directly on basement. The stratigraphic thickness changes of the Surprise indicate deposition during local syn-sedimentary faulting. The lateral persistence of the Surprise may point to a regional glacial influence, also supported by rare striated clasts in other canyons. The younger, Wildrose, diamictite overlaps farther southeastward to rest on basement blocks that lack all the older Kingston Peak members. Detailed mapping in the Panamint region reveals a complex relationship between the Surprise diamictite, the succeeding sandy-mass flows and the Sourdough limestone. Contrary to other cap carbonate examples, the Sourdough limestone does not simply cap the Surprise diamictite; it can be found as clasts in the uppermost Surprise diamictite; and it also occurs up-section in the sandy Middle Park Member. Interbedding of cap carbonate facies through a succession of diamictite and sandy facies contrasts with the typical abrupt deposition of carbonate on diamictite facies representative of most Neoproterozoic deglacial successions globally, including the Wildrose-Noonday transition. These relationships suggest that carbonate deposition is not limited to the immediate post-diamictite interval; neither can they be explained by rapid globally synchronous climate change. Local tectonic controls open the possibility that cap carbonates can be diachronous and still show abrupt relations with diamictite facies in other regions.