Geology topics

C. Shaun Peterson

Publications and source records attributed to C. Shaun Peterson.

3 recordsLinked to original sources

USGS2013

Status of a reconnaissance field study of the Susitna basin, 2011

The Alaska Division of Geological & Geophysical Surveys (DGGS) and Alaska Division of Oil and Gas (DOG), in collaboration with the U.S. Geological Survey (USGS) performed reconnaissance field studies for ten days in late June 2011, in the Susitna basin, directly north of Cook Inlet, south-central Alaska (fig. 1). The purpose of our investigation was to reconnoiter outcrops in the basin and along its periphery to gather new information towards understanding the basin formation history and stratigraphy. This reconnaissance data represents the first step toward better understanding the basin’s hydrocarbon potential, a key component of DGGS’s multi-year In- State Gas Program. This program is focused on collecting baseline geologic information from potential frontier gas basins to encourage new exploration to help, in part, reduce the high cost of energy in rural Alaska. Our work represents the first season of this three-year project. Preliminary results from year two, a companion project within the Nenana and Tanana basins in interior Alaska, are described by Wartes and others (2013). DGGS plans to return to the Susitna basin for follow-up fieldwork during the third and final year of the program. The motivation for developing a better understanding of the Susitna basin stems from the recognition that the Susitna basin shares similar age coal-bearing strata with the adjacent, petroliferous Cook Inlet forearc basin (Barnes, 1966; Reed and Nelson, 1980) and with exhumed strata in the Matanuska Valley forearc basin (Trop and others, 2003) (figs. 1 and 2). Cook Inlet basin has eight producing oil fields, more than 25 producing gas fields, and likely contains many additional undiscovered oil and gas accumulations (LePain and others, in press). Most of the Cook Inlet gas is of microbial origin and apparently was sourced from abundant coalbeds of primarily Miocene age in the Tyonek, Beluga, and Sterling Formations (Claypool and others, 1980; Magoon, 1994). If the biogenic gas model for Cook Inlet is applicable to the Susitna basin, then the latter may be a viable source for Alaska Railbelt and rural energy needs. This brief overview report summarizes the reconnaissance field data collected in the Susitna basin during the first summer of the program. As the data are developed, this report will be followed by interpretive technical reports addressing the stratigraphy, reservoir quality, coal quality and gas potential, hydrocarbon seal integrity, subsurface structure, and uplift history of the basin and sub-basin margins.

Alaska↗

USGS2013

Summary of 2012 reconnaissance field studies related to the petroleum geology of the Nenana Basin, interior Alaska

The Alaska Division of Geological & Geophysical Surveys (DGGS) recently initiated a multi-year review of the hydrocarbon potential of frontier sedimentary basins in Alaska (Swenson and others, 2012). In collaboration with the Alaska Division of Oil & Gas and the U.S. Geological Survey we conducted reconnaissance field studies in two basins with recognized natural gas potential—the Susitna basin and the Nenana basin (LePain and others, 2012). This paper summarizes our initial work on the Nenana basin; a brief summary of our work in the Susitna basin can be found in Gillis and others (in press). During early May 2012, we conducted ten days of helicopter-supported fieldwork and reconnaissance sampling along the northern Alaska Range foothills and Yukon–Tanana upland near Fairbanks (fig. 1). The goal of this work was to improve our understanding of the geologic development of the Nenana basin and to collect a suite of samples to better evaluate hydrocarbon potential. Most laboratory analyses have not yet been completed, so this preliminary report serves as a summary of field data and sets the framework for future, more comprehensive analysis to be presented in later publications.

Alaska↗

USGS2013

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

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 R o ) 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.

Alaska↗