|Lone Mountain, a thick stack of Lower Paleozoic sediments deposited on the continental shelf of Laurentia. North of US Hwy 50, c. 15 mi west of Eureka.|
|Domains, terranes, and assemblages of Nevada (Crafford 2010). Added dashed line is a rough approximation of the late Proterozoic rift.|
Reassembly didn't start right away. For several hundred million years, the Laurentian coast was a passive margin—the continent and seafloor on the same plate, with no tectonic activity. Thick layers of sediments accumulated offshore. Three zones of deposition are recognized, now represented by early Paleozoic rocks: continental shelf in eastern and central Nevada (e.g., Lone Mountain in photo above); continental slope in central Nevada; and, to the west, deep basin sediments underlain by seafloor.
|Simple schematic of the early Paleozoic margin of Laurentia (trilobites not to scale ;)|
|Mesozoic terranes and assemblages of Nevada (Crafford 2010).|
|Two puzzling mementos. Metavolvanic? From whence? Deformed before or during collision?|
|North of US Hwy 50 just west of Sand Springs Pass; rhyolite intruded into slate and phyllite.|
|My field assistant is not a fan of roadside outcrops (she has to stay in the van).|