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Reconnaissance studies of potential petroleum source rocks in the Middle Jurassic Tuxedni Group near Red Glacier, eastern slope of Iliamna Volcano

Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-1B

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Abstract

Previous geological and organic geochemical studies have concluded that organic-rich marine shale in the Middle Jurassic Tuxedni Group is the principal source rock of oil and associated gas in Cook Inlet (Magoon and Anders, 1992; Magoon, 1994; Lillis and Stanley, 2011; LePain and others, 2012; LePain and others, submitted). During May 2009 helicopter-assisted field studies, 19 samples of dark-colored, fine-grained rocks were collected from exposures of the Red Glacier Formation of the Tuxedni Group near Red Glacier, about 70 km west of Ninilchik on the eastern flank of Iliamna Volcano (figs. 1 and 3). The rock samples were submitted to a commercial laboratory for analysis by Rock-Eval pyrolysis and to the U.S. Geological Survey organic geochemical laboratory in Denver, Colorado, for analysis of vitrinite reflectance. The results show that values of vitrinite reflectance (percent Ro) in our samples average about 2 percent, much higher than the oil window range of 0.6–1.3 percent (Johnsson and others, 1993). The high vitrinite reflectance values indicate that the rock samples experienced significant heating and furthermore suggest that these rocks may have generated oil and gas in the past but no longer have any hydrocarbon source potential. The high thermal maturity of the rock samples may have resulted from (1) the thermaleffects of igneous activity (including intrusion by igneous rocks), (2) deep burial beneath Jurassic, Cretaceous, and Tertiary strata that were subsequently removed by uplift and erosion, or (3) the combined effects of igneous activity and burial.

Additional Publication Details

Publication type:
Report
Publication Subtype:
Other Government Series
Title:
Reconnaissance studies of potential petroleum source rocks in the Middle Jurassic Tuxedni Group near Red Glacier, eastern slope of Iliamna Volcano
Series title:
Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report
Series number:
2013-1B
Year Published:
2013
Language:
English
Publisher:
Alaska Division of Geological and Geophysical Surveys
Contributing office(s):
Geology, Minerals, Energy and Geophysics Science Center
Description:
5 p.
Larger Work Type:
Report
Larger Work Subtype:
Other Government Series
Larger Work Title:
Overview of 2012 field studies: Upper Alaska Peninsula and west side of lower Cook Inlet, Alaska (Alaska Division of Geological & Geophysical Surveys Preliminary Interpretive Report 2013-1)
First page:
5
Last page:
9
Country:
United States
State:
Alaska
Other Geospatial:
Iliamna Volcano;Red Glacier