Skip to Main Content
Book Chapter

Distal Facies Variability Within the Upper Triassic Part of the Otuk Formation in Northern Alaska

By
K. J. Whidden
K. J. Whidden
US Geological Survey, Central Energy Resources Science Center, Denver Federal Center MS 939, Denver, Colorado 80225 USA
Search for other works by this author on:
J. A. Dumoulin
J. A. Dumoulin
US Geological Survey, Alaska Science Center, 4210 University Drive, MS 259, Anchorage, Alaska 99508 USA
Search for other works by this author on:
M. T. Whalen
M. T. Whalen
University of Alaska, Department of Geology and Geophysics, Reichardt Building, 900 Yukon Drive, Fairbanks,Alaska 99775 USA
Search for other works by this author on:
E. Hutton
E. Hutton
US Geological Survey, Geology, Minerals, Energy and Geophysics Science Center, 345 Middlefield Road, MS 901, Menlo Park, California 94025 USA
Search for other works by this author on:
T. E. Moore
T. E. Moore
US Geological Survey, Central Energy Resources Science Center, Denver Federal Center MS 939, Denver, Colorado 80225 USA
Search for other works by this author on:
S. B. Gaswirth
S. B. Gaswirth
US Geological Survey, Central Energy Resources Science Center, Denver Federal Center MS 939, Denver, Colorado 80225 USA
Search for other works by this author on:
Published:
January 01, 2014

Abstract

The Triassic-Jurassic Otuk Formation is a potentially important source rock in allochthonous structural positions in the northern foothills of the Brooks Range in the North Slope of Alaska. This study focuses on three localities of the Upper Triassic (Norian) limestone member, which form a present-day, 110-km-long, east-west transect in the central Brooks Range. All three sections are within the structurally lowest Endicott Mountain allochthon and are interpreted to have been deposited along a marine outer shelf with a ramp geometry.

The uppermost limestone member of the Otuk was chosen for this study in order to better understand lateral and vertical variability within carbonate source rocks, to aid prediction of organic richness, and ultimately, to evaluate the potential for these units to act as continuous (or unconventional) reservoirs. At each locality, 1 to 4 m sections of the limestone member were measured and sampled in detail to capture fine-scale features. Hand sample and thin section descriptions reveal four major microfacies in the study area, and one diagenetically recrystallized microfacies. Microfacies 1 and 2 are interpreted to represent redeposition of material by downslope transport, whereas microfacies 3 and 4 have high total organic carbon (TOC) values and are classified as primary depositional organofacies. Microfacies 3 is interpreted to have been deposited under primarily high productivity conditions, with high concentrations of radiolarian tests. Microfacies 4 was deposited under the lowest relative-oxygen conditions, but abundant thin bivalve shells indicate that the sediment-water interface was probably not anoxic.

The Otuk Formation is interpreted to have been deposited outboard of a southwest-facing ramp margin, with the location of the three limestone outcrops likely in relatively close proximity during deposition. All three sections have evidence of transported material, implying that the Triassic Alaskan Basin was not a low-energy, deep-water setting, but rather a dynamic system with intermittent, yet significant, downslope flow. Upwelling played an important role in the small-scale vertical variability in microfacies. The zone of upwelling and resultant oxygen-minimum zone may have migrated across the ramp during fourth- or fifth-order sea-level changes.

You do not currently have access to this article.
Don't already have an account? Register

Figures & Tables

Contents

SEPM Special Publication

Deposits, Architecture, and Controls of Carbonate Margin, Slope and Basinal Settings

Klaas Verwer
Klaas Verwer
Statoil ASA, Sandsliveien 90 5124, Bergen, Norway
Search for other works by this author on:
Ted E. Playton
Ted E. Playton
Chevron Energy Technology Company, 1500 Louisiana St, Houston, Texas 77002, USA
Search for other works by this author on:
Paul M. (Mitch) Harris
Paul M. (Mitch) Harris
Chevron Energy Technology Company, 1500 Louisiana St, Houston, Texas 77002, USA
Search for other works by this author on:
SEPM Society for Sedimentary Geology
Volume
105
ISBN electronic:
9781565763241
Publication date:
January 01, 2014

References

Related

A comprehensive resource of eBooks for researchers in the Earth Sciences

Related Articles
This Feature Is Available To Subscribers Only

Sign In or Create an Account

This PDF is available to Subscribers Only

View Article Abstract & Purchase Options

For full access to this pdf, sign in to an existing account, or purchase an annual subscription.

Subscribe Now