Sedimentary Evolution of the Miocene-Pliocene Camp Davis Basin, Northwestern Wyoming

The late Miocene to early Pliocene Camp Davis Formation of northwestern Wyoming consists of conglomeratic lower and upper members separated by lacustrine limestone, siltstone, and tuff of the middle member.Detailed lithofacies analyses show the lower member (75 to 100 meters) to consist primarily of massive to horizontally stratified pebble to cobble gravel (Gm) and trough cross-stratified granule to pebble gravel (Gt).Deposition occurred in a Scott-type braided stream system characterized by development and aggradation of diffuse gravel sheets and longitudinal bars (Gm) and filling of shallow channel scours (Gt).Paleocurrent data and presence of reworked Precambrian quartzite clasts and distinctive, yet previously unrecognized, Tertiary intrusive clasts suggest deposition by a south to southeastward flowing axial-parallel fluvial system (ancestral Snake River).The upper member (1500 meters) is dominated by muddy, clast-supported, massive to horizontally stratified pebble to boulder conglomerates (Gm/Dcm and Gm/Dcm-Dmm) deposited by streamflow, sheetflood, hyperconcentrated flood flows and high-strength plastic debris flows.Matrix-supported conglomerate (Gms/Dmm) is typically massive, may be inversely graded, and represents deposition by high-strength plastic debris flows.Low-angle trough crossbedded gravel (Gt) accumulated during shallow scour infilling within shallow bed-load streams and during periods of unconfined sheet-flood.Collectively, these lithofacies suggest deposition on the proximal portion of a hyperconcentrated flood flow-dominated alluvial fan.Clast imbrication measurements indicate a southwestward paleoflow direction.Clasts include Paleozoic and Mesozoic sedimentary and Precambrian crystalline rocks M cur) patience throughout the completion of this thesis project.