Paleoenvironmental interpretation of the Guilmette Formation near Ely, Nevada
Two sections of the Upper Devonian Guilmette Formation in White Pine County, Nevada, were measured and sampled to determine its paleoenvironmental and depositional history. The Guilmette was deposited predominately during a transgressive phase that was interrupted by minor regressions. The formation was divided into five informal members on the basis of lithologic and paleontological occurrences. Each member was broken down into separate microfacies representing a variety of environments. The depositional environment for each member is: 1) Alternating dolomite-limestone member--deposited in an intertidal-shallow lagoon with minor fluctuations of transgression and regression. 2) Lower mound member--deposited in a slightly restricted deep lagoon with an abundance of stromatoporoids. Small biohermal mounds are associated with this member. 3) Fore-mound member--initially deposited in a restricted lagoon environment that prograded into an open marine shallow shelf. 4) Upper mound member--deposited during fluctuating sealevel that caused alternations between lagoon and open marine conditions. The upper most part represents a trend toward shallow open shelf contitions. 5) Inter-mound member--represents a regressive phase noted in the Pancake Range that is not present in the Cherry Creek Range. The absence of this member in the Cherry Creek section may be a result of tectonic uplift initiated by onset of the Antler Orogeny. Transgression occurred during the Upper Givetian and Frasnian in an easterly direction across Nevada and Utah.
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