FOURTH ORDER PARASEQUENCES OF THE MOLEEN FORMATION, ELY LIMESTONE, ELKO, NEVADA
The base cycle at Grindstone Mountain, GM1, is a transgressive cycle comprised of basal sandy micrites that grade to sandy grainstones. The central 8 m is a covered section assumed to be eroded basinal micrites and interpreted to represent a period of aggradation. The MG1/GM2 boundary is covered and interpreted to be abrupt deep water sediments such as micrites - the same applies to the MG3/MG2 boundary. The upper part of the second cycle (GM2) is a transgressive parasequence from sandy micrite to silty grainstones. MG3, has been interpreted to be a transgressive sequence dominated by carbonaceous arenites with a small period of carbonate dominated deposition marking the top of the cycle. The upper boundary has been delineated as the center of a 1 m thick bed of sandy packstone and is arbitrary. Samples from the base and top of the Grindstone Mountain section contain Millerella and Pseudostaffella ex gr. needhami, (among others) which indicate a lower Atokan age. Based on this fauna an estimated maximum time span for the studied section is 3 million years. Thus, assuming a linear deposition rate, the maximum duration of cycle one is approximately 1.3 m.y., the second cycle is 625,000 yrs., while the third is approximately 800,000 yrs.