Rock-eval pyrolysis, vitrinite reflectance, and kerogen microscopy results from Miocene carbonaceous mudstones and coals in outcrop, McGrath Quadrangle, southwestern Alaska

Description

The Cenozoic Holitna basin is a gravity-defined feature that sits astride the Denali-Farewell fault zone in southwestern Alaska. The basin corresponds to a gravity low in excess of -40 milligals (mGals). No outcrops exist within the footprint of the gravity low and no subsurface data are available; consequently, the stratigraphy and age of its fill are unknown. The Alaska Division of Geological & Geophysical Surveys (DGGS) investigated the shallow gas potential of the basin during the summers of 2000 and 2002 by studying Tertiary coal-bearing rocks exposed along the Denali-Farewell fault zone to the northeast of the basin in the southern McGrath Quadrangle as an outcrop analog to the subsurface stratigraphy of the basin. We visited exposures along Windy Fork Middle Fork River to collect samples for source-rock characterization, including Rock-Eval pyrolysis, vitrinite reflectance measurements, and visual kerogen analysis. Rock-Eval pyrolysis results from carbonaceous mudstone and coal samples along Windy Fork indicate the presence of Type II and Type III kerogen, which are expected to be excellent sources of oil and gas under favorable subsurface conditions. Available thermal maturity data for the samples indicate they are immature for oil and gas, but are in the late pre-oil phase of maturity. If a coal- and carbonaceous-mudstone-bearing succession similar to the rocks discussed in this report from the McGrath Quadrangle are present in the subsurface of the gravity-defined Holitna basin at favorable depths, they can be expected to have significant thermogenic oil and gas generative potential.

Resources

Name Format Description Link
0 http://dx.doi.org/10.14509/1853
0 http://dx.doi.org/10.14509/2589
0 http://dx.doi.org/10.14509/2725
0 http://dx.doi.org/10.14509/2665
0 http://dx.doi.org/10.14509/2870
0 http://dx.doi.org/10.14509/1854
0 http://dx.doi.org/10.14509/2736
0 http://dx.doi.org/10.14509/2733
0 CSDGM IMPORT ERROR: No digtinfo/formcont http://dx.doi.org/10.14509/29406
0 http://dx.doi.org/10.14509/29406
0 http://dx.doi.org/10.14509/16681

Tags

  • carboniferous
  • vitrinite
  • mcgrath quadrangle
  • resources
  • rock-eval pyrolysis
  • pyrolysis
  • coal
  • miocene
  • energy

Topics

  • Local Government

Categories