Petroleum Source Rock Evaluation of the Cretaceous Newark Canyon Formation in North-Central Nevada

MULLARKEY, J. C., Colorado School of Mines, Golden, CO, J. L. CLAYTON, U.S. Geological Survey, Denver, CO, R. F. WENDLANDT, Colorado School of Mines, Golden, CO, and T. A. DAWS, U.S. Geological Survey, Denver, CO

The petroleum source rock potential of the Cretaceous Newark Canyon Formation, Eureka and Elko counties, Nevada, has been determined by integrated field and subsurface sampling and mapping and by geochemical analyses. Geologic mapping was supplemented by measurement of a reference stratigraphic section and four hand-held gamma-ray traverses. Cores and cuttings from three wells provide subsurface control. Sixty-six outcrop and ten subsurface Newark Canyon samples were collected and pyrolyzed (Rock-Eval II) to determine hydrocarbon yield, total organic carbon content (TOC), and thermal maturity. Two samples were solvent extracted for gas chromatography and mass spectrometry analyses to evaluate the environment of deposition.

The Newark Canyon Formation is 2055 ft thick in the Cortez Range and contains 115 ft of limestone and calcareous shale with an average TOC of 2.5 weight % of type II/III kerogen (hydrogen indices 7-424 mg hydrocarbon/g TOC). The correlative section in the Pinon Range contains 200 ft of calcareous shale averaging 8% TOC (ranging up to 23.5%) of type I/II kerogen (hydrogen indices 457-912 mg hydrocarbon/g TOC). Subsurface samples are similar to the Cortez Range samples in organic content and kerogen type. The Newark Canyon Formation is marginally mature to mature with respect to petroleum generation (average T values = 440 degrees C). This data indicates the Newark Canyon Formation is an excellent potential source rock. Saturated hydrocarbon distributions confirm field observations that indicate deposition of the Newark Canyon's organic-rich facies in a low-energy lacustrine environment.

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)