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Geologic Report for the Shumagin Planning Area

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Geologic Report for the Shumagin Planning Area OCS Report Geologic Report for the MMS 89-0097 Shumagin Planning Area, Western Gulf of Alaska by Warren L. ~orowik David A. Steffy Peter J. Hoose t edited by Ronald F. Turner U. S. Department of the Interior Anchorage, Alaska Minerals Management Service 1989 Alaska OCS Region t Valued friend, colleague, and researcher, deceased December 1989. Library of Congress Cataloging-in-Publication Data Horowitz, Warren L., 1953- Geologic report for the Shurnagin planning area, western Gulf of Alaska / by Warren L. Horowitz, David A. Steffy, Peter J. Hoose ; edited by Ronald F. Turner. p. cm. - (OCS report) "MMS-89-0097." Includes bibliographical references. 1. Geology-Alaska-Alaska, Gulf of, Region. 2. Petrdeum-Geology- Alaska- Alaska, Gulf of, Region. I. Steffy, David A. II. Hoose, Peter J. Ill. Turner, Ronald F. IV. Tile. V. Series. QE84.A33H67 1989 551.46'634 - dC20 89600377 CIP Available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161, Order Number PB 90-146317 Any use of trade nanzes is for descriptivepuposes only and does not constitute endorsement of these products by the Mitterals Management Service. Table of Contents * Abstract .............................................................................. 1 Introduction ............................................................................... 3 PART 1: REGIONAL GEOLOGY 1. Geologic Framework ..................................................................... 9 2. Geology of Deep-Water Areas ............................................................ 15 Aleutian Abyssal Plain Geology .......................................................... IS Aleutian Trench Geology ............................................................ 15 Slope Geology ......................................................................... 18 3. Onshore Geology ........................ .. ........................................ 29 Alaska Peninsula Stratigraphy ........................................................... 29 Kodiak Islands ......................................................................... 30 Border Ranges Fault .................................................................. 32 Chugach and Prince William Terranes .................................................... 32 Early Cretaceous Accretion ........................................................ 32 Summary ............................................................................. 34 4 . Continental Shelf Geology ................................................................ 37 KodiakDST Wells ..................................................................... 37 Miocene Unwnformity ............................................................ 39 Shurnagin Shelf Geology ............................................................... 39 Seismic Stratigraphy .............................................................. 40 Sequence A (Cretaceous and Paleocene) ........................................ 40 Sequence B (Eocene) ......................................................... 42 Sequence C (Oligocene to Pleistocene) ......................................... 43 Summary .................................................................. 46 Structural Geology ................................................................ 46 Basin Boundary Features ...................................................... 46 Border Ranges Fault ..................................................... 46 Shumagin Ridge ......................................................... 47 Sanak Island Wrench Zone ............................................... 47 Central Sanak High ...................................................... 47 Eage Sanak Island Transverse High ............................................. 47 Boundary Fault ........................................................ 48 Unimak Ridge .......................................................... 48 EastSanakSlopeRidge .................................................. 48 Basinstructure ............................................................. 49 Tugirlak Basin ........................................................... 49 Shumagin Basin ......................................................... 49 EastSanakBasin ........................................................ 51 East Sanak Slope Basin ................................................... 51 West Sanak Basin ........................................................ 51 Unimak Basin ........................................................... 55 Summary and Discussion ..................................................... 55 5 . Time-Depth Curves ...................................................................... 59 6. Fault Mechanisms. Seismicity. and Transverse Tectonic Features .............................. 65 7 . Geologic History ......................................................................... 71 PART 2: PETROLEUM GEOLOGY 8. Exploration History ...................................................................... 81 9 . Geothermal Gradient ..................................................................... 83 10.SourccRock ........................................................................... 87 Kodiak Stratigraphic Test Wells and Onshore Geology ...................................... 87 ShumaginPlanningArca ................................................................ 88 Shumagin Continental Slope ........................................................ 88 Shuma@nShelfBsim ............................................................. 89 Summary ............................................................................. !XI 11.ReservoirRocks ........................................................................ 91 Seismic Sequence C .................................................................... 92 Shunagin Plimning Arw ........................................................... 92 Alaska Peninsula (Oligocene and Miocene) ........................................... 92 Onshore Kodiak .................................................................. 92 Kodiak Shelf StratigraphicTest Wells ................................................ 94 Seismic Sequence B .................................................................... 94 Seismic Sequence A .................................................................... 94 Summary ............................................................................. 95 ms 12. Play Concepts ........................................................................... 97 Source Rocks .......................................................................... 97 Reservoir Rocks ....................................................................... 97 Migration ............................................................................. 97 Seals ................................................................................. 97 Shurnagin Shelf Plays and Trap Configurations ............................................. 97 Simple. Faulted Fold Traps in the Shumagin Basin ..................................... 97 Fold Traps in the West Sanak and Unimak Basins ..................................... 97 Extensional Fault Traps in the East Sanak. West Sanak, and Unirnak Basins ............... 98 Stacked and Imbricate Thrust Traps in the West Sanak and Unimak Basins ................ 101 Stratigraphic-Onlapand Facies Traps ................................................ 101 Sanak Island Transverse High Play ....................................................... 101 Deep-Water Plays ...................................................................... 101 Summary ............................................................................. 104 PART 3: SHALLOW GEOLQCY. GEOUXIC HAZARDS. and ENVIRONMENTAL CONDITIONS 13 .Shallow Geology ........................................................................ 107 Physiography and Bathymetry ............................................................ 107 Surficial Sediment and Bedrock Outcrops ................................................. 110 14. Potential Geologic Hazards .............................................................. 117 Seismicity ............................................................................. 117 Ground Shaking .................................................................. 117 Fault Displacement ................................................................ 117 Tectonic Uplift or Subsidence ....................................................... 118 Ground Failure ................................................................... 118 Tsunamis ........................................................................ 118 Earthquake Potential .............................................................. 118 Shallow Gas ............................................................................121 Volcanic Activity ....................................................................... 121 Sediment Erosion and Deposition ........................................................ 123 Summary ............................................................................. 123 15. Climate and Meteorology ................................................................ 125 Summary .................................................................................. 129 References ............................................................................... 131 FIGURES 1 .Location of the Shumagin Planning Area ........................................................
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