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

Basement Structure and Styles of Active Tectonic Deformation in Central Interior Alaska

Geosciences ◽

10.3390/geosciences11030127 ◽

2021 ◽

Vol 11 (3) ◽

pp. 127

Author(s):

Nilesh C. Dixit ◽

Catherine Hanks

Keyword(s):

Crustal Structure ◽

Foreland Basin ◽

Active Regions ◽

Structural Features ◽

Tectonic Deformation ◽

Block Rotation ◽

High Concentration ◽

Intraplate Earthquakes ◽

Interior Alaska ◽

Nenana Basin

Central Interior Alaska is one of the most seismically active regions in North America, exhibiting a high concentration of intraplate earthquakes approximately 700 km away from the southern Alaska subduction zone. Seismological evidence suggests that intraplate seismicity in the region is not uniformly distributed, but concentrated in several discrete seismic zones, including the Nenana basin and the adjacent Tanana basin. Although the location and magnitude of the seismic activity in both basins are well defined by a network of seismic stations in the region, the tectonic controls on these intraplate earthquakes and the heterogeneous nature of Alaska’s continental interior remain poorly understood. We investigated the crustal structure of the Nenana and Tanana basins using available seismic reflection, aeromagnetic and gravity anomaly data, supplemented by geophysical well logs and outcrop data. We developed nine new two-dimensional forward models to delineate internal geometries and the crustal structure of Alaska’s interior. The results of our study demonstrates a strong crustal heterogeneity beneath both basins. The Tanana basin is a relatively shallow (up to 2 km) asymmetrical foreland basin with its southern, deeper side controlled by the northern foothills of the Central Alaska Range. Northeast-trending left lateral strike-slip faults within the Tanana basin are interpreted as a zone of clockwise crustal block rotation. The Nenana basin has a fundamentally different geometry. It is a deep (up to 8 km), narrow transtensional pull-apart basin that is deforming along the left-lateral Minto Fault. This study identifies two distinct modes of current tectonic deformation in Central Interior Alaska and provides a basis for modeling the interplay between intraplate stress fields and major structural features that potentially influence the generation of intraplate earthquakes in the region.

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Cenozoic tectonic and thermal history of the Nenana basin, central interior Alaska: new constraints from seismic reflection data, fracture history, and apatite fission-track analyses

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2016-0197 ◽

2017 ◽

Vol 54 (7) ◽

pp. 766-784 ◽

Cited By ~ 2

Author(s):

Nilesh Dixit ◽

Catherine Hanks ◽

Alec Rizzo ◽

Paul McCarthy ◽

Bernard Coakley

Keyword(s):

Seismic Reflection ◽

Fission Track ◽

Strike Slip ◽

Apatite Fission Track ◽

Plate Convergence ◽

South Central ◽

Interior Alaska ◽

Late Paleocene ◽

Half Graben ◽

Nenana Basin

The Nenana basin of interior Alaska forms a segment of the diffuse plate boundary between the Bering and North American plates and is located within a complex zone of crustal-scale strike-slip deformation that accommodates compressional stresses in response to oblique plate convergence to the south. The basin is currently the focus of new oil and gas exploration. Integration of seismic reflection and well data, fracture data, and apatite fission-track analyses with regional data improves our understanding of the tectonic development of this continental strike-slip basin. The Nenana basin formed during the Late Paleocene as a 13 km wide half-graben, affected by regional intraplate magmatism and localized crustal thinning across the Minto Fault in south-central Alaska. The basin was uplifted and exhumed along this faulted margin in the Early Eocene through to Late Oligocene in response to oblique subduction along the southern Alaska margin. This event resulted in the removal of up to 1.5 km of Late Paleocene strata from the basin. Renewed rifting and subsidence during the Early Miocene widened the basin to the west resulting in deposition of Miocene non-marine clastic rocks in reactivated and newly formed extensional half-grabens. In the Middle to Late Miocene, left lateral strike-slip faulting was superimposed on this half-graben system, with rapid subsidence beginning in the Pliocene and continuing to the present day. At present, the Nenana basin is in a zone of transtensional deformation that accommodates compressional stresses in response to oblique plate convergence and allows tectonic subsidence by oblique extension along major basin-bounding strike-slip faults.

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Radiocarbon dating of samples collected during the 1984 expedition to North Greenland

Rapport Grønlands Geologiske Undersøgelse ◽

10.34194/rapggu.v125.7880 ◽

1985 ◽

Vol 125 ◽

pp. 5-8

Author(s):

M Ghisler

Keyword(s):

Radiocarbon Dating ◽

East Coast ◽

Mineral Exploration ◽

Field Work ◽

Field Studies ◽

Petroleum Geology ◽

Laboratory Studies ◽

Main Field ◽

The West ◽

North Greenland

The Geological Survey of Greenland (GGU) continued the investigation of the geology of Greenland during the year with both field studies in Greenland and laboratory studies in Copenhagen. Field work was carried out between June and September by two main field groups in the northern and southernmost parts of Greenland separated by more than 2000 km. Smaller groups worked in several areas along the west coast and a short reconnaissance was accomplished along the south-east coast. GGU's work encompassed geochemical and geophysical studies, mineral exploration, petroleum geology, environmental investigations, and glaciology. Seventy-nine scientists and technicians participated in the summer's field work. In addition to the GGU parties several groups from other institutions worked in dose collaboration with GGU. The areas of activity in 1984 are indicated on fig. 1.

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