Report of Investigations 2014-4 GEOLOGIC MAP OF THE south-central sagavanirktok Quadrangle, north slope, alaska by R.J. Gillis, P.L. Decker, M.A. Wartes, A.M. Loveland, and T.D. Hubbard Sagwon Member of the Sagavanirktok Formation forms the east bank of the Sagavanirktok River; the formation is tilted gently toward the northwest. Trans-Alaska Pipeline System Pump Station #2 in background. Published by STATE OF ALASKA DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGICAL & GEOPHYSICAL SURVEYS 2014 Report of Investigations 2014-4 GEOLOGIC MAP OF THE south-central sagavanirktok Quadrangle, north slope, alaska by R.J. Gillis, P.L. Decker, M.A. Wartes, A.M. Loveland, and T.D. Hubbard 2014 This DGGS Report of Investigations is a final report of scientific research. It has received technical review and may be cited as an agency publication. STATE OF ALASKA Sean Parnell, Governor DEPARTMENT OF NATURAL RESOURCES Joe Balash, Commissioner DIVISION OF GEOLOGICAL & GEOPHYSICAL SURVEYS Steven Masterman, State Geologist and Director Publications produced by the Division of Geological & Geophysical Surveys (DGGS) are available for free download from the DGGS website (www.dggs.alaska.gov ). Publications on hard-copy or digital media can be examined or purchased in the Fairbanks office: Alaska Division of Geological & Geophysical Surveys 3354 College Rd., Fairbanks, Alaska 99709-3707 Phone: (907) 451-5020 Fax (907) 451-5050 [email protected] www.dggs.alaska.gov Alaska State Library Alaska Resource Library & Information State Office Building, 8th Floor Services (ARLIS) 333 Willoughby Avenue 3150 C Street, Suite 100 Juneau, Alaska 99811-0571 Anchorage, Alaska 99503-3982 Elmer E. Rasmuson Library University of Alaska Anchorage Library University of Alaska Fairbanks 3211 Providence Drive Fairbanks, Alaska 99775-1005 Anchorage, Alaska 99508-4614 This publication released by the Division of Geological & Geophysical Surveys was produced and printed in Fairbanks, Alaska, at a cost of $28.00 per copy. Publication is authorized by Alaska Statute 41, which charges the division “to determine the potential of Alaskan land for production of metals, minerals, fuels, and geothermal resources; the location and supplies of groundwater and construction materials; the potential geologic hazards to buildings, roads, bridges, and other installations and structures; and shall conduct such other surveys and investigations as will advance knowledge of the geology of Alaska.” contents Introduction ............................................................................................................................................................................1 Overview of mapping methods and constraints .....................................................................................................................1 Overview of stratigraphy .......................................................................................................................................................4 Structural style .......................................................................................................................................................................8 Timing of hydrocarbon maturation and migration .................................................................................................................9 Discussion of the timing of deformation and exhumation, and their implications ................................................................9 Conclusions ..........................................................................................................................................................................13 Description of map units ......................................................................................................................................................13 Surficial deposits ............................................................................................................................................................13 Bedrock deposits ............................................................................................................................................................14 Acknowledgments ................................................................................................................................................................20 References ............................................................................................................................................................................21 FIGURES Figure 1. Station location map showing the distribution of ~800 bedrock stations visited during the 2008 field season ...................................................................................................................................................................2 2. Shaded-relief map of the study area and locations of wells and major physiographic features ..........................3 3. Stratigraphic cross section constrained by four wells in or near the map area ....................................................5 4. Chronostratigraphic column for the Colville basin, Alaska .................................................................................7 5. View to the north along the Sagavanirktok River at Sagwon Bluffs ...................................................................8 6. Tight, small-scale folding of Canning Formation strata exposed in the core of the Kuparuk anticline on the east bank of the Sagavanirktok River ..........................................................................................................10 7. Age vs. measured-depth plots of previously published apatite fission-track data for the Susie Unit 1, Aufeis Unit 1, and Lupine Unit 1 wells .............................................................................................................11 SHEETS Sheet 1. 1:63,360-scale geologic map of the south-central Sagavanirktok Quadrangle, North Slope, Alaska 2. Diagrammatic cross section oriented approximately perpendicular to the main structural trend through the Lupine Unit 1 and Susie Unit 1 wells. GEOLOGIC MAP OF THE south-central sagavanirktok Quadrangle, north slope, alaska by R.J. Gillis1, P.L. Decker2, M.A. Wartes1, A.M. Loveland1 , and T.D. Hubbard1 introduction overview oF Mapping Methods and constraints Despite proximity to the Dalton Highway and the Trans- Alaska Pipeline corridor, the east-central foothills of the North Rock unit identification, bedding attitudes, structural Slope remain only lightly explored by drilling, and have not observations, hydrocarbon indications, and analytical data been mapped in detail. Previous bedrock investigations in the from samples collected at field stations (fig. 1) were used Sagavanirktok River area are limited to reconnaissance-level to ground-truth and refine preliminary geologic interpreta- 1:1,000,000-scale maps by Lathram (1965) and Grybeck and tions based in part on subsurface data. Approximately 420 others (1977), road log figures by Mull and Harris (1989), line km (260 line mi) of proprietary two-dimensional (2-D) and unpublished inch-to-mile mapping by Gil Mull. This seismic reflection data through the map area (seven dip new geologic mapping of the southwest and south-central lines and three strike lines) were interpreted by P.L. Decker Sagavanirktok Quadrangle at 1:63,360 scale was completed prior to 2008 field activities, integrating available surface through the combination of field mapping and stratigraphic information and subsurface correlations in the Lupine Unit studies by the Alaska Division of Geological & Geophysical 1, Aufeis Unit 1, Ivishak Unit 1, and Echooka Unit 1 wells Surveys (DGGS) and the Alaska Division of Oil and Gas in the map area and the Susie Unit 1, Nora Federal 1, and (DOG) in the summers of 2007 and 2008. The map area is Bush Federal 1 wells nearby to the north (figs. 2 and 3). The bisected by the Dalton Highway, the Sagavanirktok River, seismic data were useful in constraining the continuity and and the Trans-Alaska Pipeline System Pump Station 2 (near plunge of major structures and in projecting lithologic and the north edge of the map), and encompasses approximately structural contacts into areas of significant Quaternary cover 3,100 km2 (1,200 mi2) of the Sagavanirktok A-3, A-4, B-3, where surface constraints were limited or lacking. Map unit B-4, and parts of A-2, A-5, B-2, and B-5 1:63,360-scale and fault contacts and fold axial traces are shown as black quadrangles. The mapping builds on existing published and lines where field evidence constrains their position. Red lines unpublished mapping by DGGS and others (Mull and Har- represent contacts and axial traces that are constrained en- ris, 1989). Stratigraphic units identified on the map are based tirely by subsurface information. Rubble traces and traceable on the revised nomenclature of Mull and others (2003) with beds evident from aerial photography and topography helped further refinement from recent and concurrent stratigraphic define folds and other structures, contributing to the map studies (Decker, 2007; Decker and others, 2008; LePain and interpretation in areas of little or no intact bedrock outcrop. others, 2008; Wartes and Decker, 2008). In most cases, rubble traces were visited to confirm forma- This mapping effort differed from previous DGGS tion assignments and all interpretations were reconciled with foothills projects by substantially incorporating subsurface available subsurface information.