8. Subsidence and Accommodation History of Arctic Alaska

The Arctic Alaska microplate, which during the Jurassic – Early Cretaceous simultaneously rifted away from Canada via counterclockwise opening of the Canada basin on one side and collided with oceanic terranes on the opposite side, contains the sedimentary record of a unique and complex geologic history. The sedimentary succession includes deposits of a Late Paleozoic–Early Jurassic passive margin, a Jurassic–Early Cretaceous asymmetrical rift shoulder, a Late Jurassic–Tertiary syn-to-post-rift foreland basin, a Cretaceous–Tertiary post-rift passive margin, and a Tertiary–Holocene system of tectonic-wedgetop basins. Arctic Alaska strata not only include one of the world’s most prolific petroleum systems but also a record of some of the globe’s most unusual climate signatures - including warm and anoxic events at high latitudes. The development of a quantitative approach for understanding the history of subsidence and sediment accommodation across this region will provide a framework for interpreting the influence of tectonics on prolific petroleum systems and their relations to high-latitude climate signatures across more than 200 million years of earth history.

That part of Arctic Alaska north of the Brooks Range extends ~1,500 km in length from the Russia-U.S. maritime boundary in the Chukchi Sea eastward to the Mackenzie River delta in Canada. The south-north width of the province, from the Herald arch – Brooks Range thrust belt to the northern margin of the Beaufort rift shoulder, ranges from ~500 km in the west to ~50 km in the east. Although the stratigraphic and structural framework of this region is fairly well known, significant questions remain regarding the influence of tectonics on subsidence history and the contributions of eustasy and sediment compaction on accommodation. Considering the relatively narrow dimensions of the Arctic Alaska microplate and the overlap in time and space of diverse tectonic events, it is unknown how regional subsidence patterns were influenced by the relative contributions of events such as the thermal uplift and subsequent cooling-contraction of the Beaufort rift shoulder, obduction and related tectonic loading along the ancestral Brooks Range orogenic belt, wrench-faulting in the Chukchi Sea, and northward translation of the Brooks Range tectonic front to a position beneath the modern Beaufort Sea shelf in the east. Although general interpretations of rift-shoulder uplift, flexural subsidence induced by obduction, and peripheral bulging induced by thrust loading have been proposed by various authors, no integrated and comprehensive analysis of subsidence history has been attempted across the entire region.

Regional datasets essential to the analysis of subsidence and accommodation history across the entire Arctic Alaska region have been assembled, and the basic geologic framework of the region has been established. Within this framework, the opportunity exists for a postdoctoral researcher to develop and apply innovative approaches to establish quantitative relationships linking tectonic events and processes to crustal responses and sedimentary signatures across an unusually large region.  The research conducted by the Mendenhall Fellow will provide a fundamental geological framework that will be of significant value both to petroleum and climate-change geoscientists working in the Arctic. The research will establish links between regional tectonic processes and the stratigraphic record, which includes petroleum source rocks ranging in age from Carboniferous to Paleogene, and also the succession deposited during the Paleocene-Eocene Thermal Maxima and the Azolla event.

Proposed Duty Station: Reston, VA

Areas of Ph.D.: Geology, geophysics

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)

Research Advisor(s): David Houseknecht, (703) 648-6466, dhouse@usgs.gov; Richard Saltus, (303) 236-1375, saltus@usgs.gov; Christopher Connors (Washington and Lee University) (540) 458-8170, ConnorsC@wlu.edu; Bernard Coakley (University of Alaska ? Fairbanks), (907) 474-5385, bernard.coakley@gi.alaska.edu; Kenneth Bird, (650) 329-4907, kbird@usgs.gov

Human Resources Office contact: Brian Arnold-Renicker, (703) 648-7468, brenicke@usgs.gov

Summary of Opportunities