'.ithosphere Investigation roaram r ros~e~tus anks I ot ~eologiculand Geophysical Sun OLOG Y CIRCULAR 984 Pre~wred in cr >operatiocr with the University of Alaska, Fairbanks, the Alaska Di vision of (~eologicol and Geol ahysical Surveys, and re-I rvarronarL I .. I acrenceC-.- - - r. rounaar I. ion Department of the Interior DONALD PAUL HODEL, Secretary U.S. Geological Survey Dallas L. Peck, Director Library of Congress Cataloging-in-Publication Data Trans-Alaska Lithosphere Jnvestigation-Prog~am Prospectus. U.S. Geological Survey Circular 984 "Prepared in cooperation with the University of Alaska, Fairbanks, the Alaska Division of Geological and Geophysical Surveys, and the National Science Foundation." Supt. of Docs. No.: I 19.4/2:984 1. Trans-Alaska Lithosphere Investigation. I. Stone, David B. 11. Page, Robert A. 111. Davies, John N. IV. University of Alaska, Fairbanks. V. Alaska. Division of Geological and Geophysical Surveys. VT. National Science Foundation (U.S.). V11. Series. QE47.A4T73 1986 651.1'3'097YX XM00201 Free on application to the Books and Open-File Reports Section, U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 COVER Deep seismic reflection profiling along the Trans-Alaska Lithosphere Investigation transect near Donnelly Dome, with the Alaska Range in the background. The five trucks in the foreground vibrate the ground in unison, sending out compressional seismic waves which reflect off velocity discontinuities within the upper lithosphere and return to the surface where they are recorded by an array of seismographs. In this survey, contracted by the U.S. Geological Survey in 1986, the signals were recorded by a 30-km linear array of 1,024 groups of seismographs deployed symmetrically about the vibrator trucks. Figure 7 (p. 14) shows an example of the data obtained. Page Page Sumary--------------------------------- 1 Research techniques (continued) Introduction----------------------------- 2 Geophysical (nonseismic)-------------- 16 Importance of studying Alaska------------ 2 Potential-field geophysics--------- 16 Transect route and geologic problems----- 5 Gravity analysis----------------- 16 Research problems------------------------ 7 Magnetic analysis---------------- 17 Tectonostratigraphic terranes--------- 7 Deep geoelectrical studies--------- 17 "Basement" of accreted terranes------- 8 Paleomagnetic studies-------------- 17 Depth to Moho------------------------- 8 Borehole geophysical studies------- 17 Orogeny and deformation of the Satellite-based studies------------ 17 lithosphere------------------------- Remote sensing------------------ 17 Subduction and magmagenesis----------- Geodesy-----------------*------- 18 Major fault systems------------------- Rock properties-------------------- 18 Neotectonics-------------------------- Geological---------------------------- 18 Oraclinal bending--------------------- Geologic mapping------------------- 18 Earthquake hazards-------------------- Stratigraphic, basin analysis, Volcano hazards----------------------- and paleontological studies------ 18 Metallogenesis------------------------ Petrologic, geochemical and Basin analysis------------------------ isotopic tracer studies---------- 18 Geothermal resources------------------ Petrologic studies of meta- Research techniques---------------------- morphic rocks-------------------- 19 Seismological------------------------- Structural and fabric studies------ 19 Artificial sources----------------- Age studies------------------------ 19 Refraction and wide-angle Metallogenesis studies------------- 19 reflection profiling--------- Neotectonic studies---------------- 19 Vertical reflection Deep drilling------------------------- 20 profiling--------------------- Investigations in progress--------------- 2 2 Marine profiling---------------- U.S. Geological Survey---------------- 22 Earthquake sources----------------- Rice University--University of Seismic imaging----------------- Alaska cooperative studies--------- 23 Seismicity studies-------------- University of Alaska------------------ 23 Focal mechanism studies--------- Alaska ~ivisionof Geological and Surface wave analysis----------- Geophysical Surveys---------------- 2 3 Appendix--------------------------------- 24 ILLUSTRATIONS Page Figure 1. Global view of Alaska and pacific and Arctic Ocean basins showing TALI route-----*-------------------------------------------*d------------d--- 2. Organizational ,-hart of TALI---------------------------------------------- 3. Map showing TALI route and te~tonostrati~raphicterranes of Alaska and Siberia----------------------------------------------------------------- 4. Map showing TALI route, tectonostratigraphic terranes, major faults, and active volcanoes---------------------------------------------------- 5. seismic record section and P-wave velocity model for the northern Chugach Mountains and southern Copper River Basin----------------------- 6. Map showing earthquake epicenters in the vicinity of the TALI transect---- 7. Vertical seismic-reflection section from the northern Chugach Mountains------------------------------------------------------- 8. Map showing seismograph stations in the vicinity of the TALI transect----- 9. Geologic map and cross section showing location of candidate site for deep scientific hole at Middleton Island, Gulf of Alaska---------------- Trans-Alaska Lithosphere Investigation-Program Prospectus David B. Stone, Robert A. Page and John N. Davies, Editors SUMMARY New insights into geologic processes will help to This prospectus presents the rationale and o Resolve fundamental questions relating to the framework for a major cooperative investigation of evolution of continents and to the movements the Alaskan lithosphere--the Trans-Alaska Litho- and collisions of the diverse microplates and sphere Investigation, or TALI. TALI focuses on a terranes that constitute the Alaskan crust, north+outh transect, extending from the active convergent Pacific margin to the passive rifted o Elucidate the origin of Alaska's oil and mineral Arctic margin, following the trans-Alaska oil pipe- resources and the causes of the State's earth- line corridor (fig. 1). The route samples an quakes and volcanoes, and exceptionally brot*d variety of geologic structures o Decipher the geologic development of western and problems along its 1,400-km length. North America and the Pacific rim. -Goals.--The goals of the Trans-Alaska Lithosphere Organization.-TALI is a cooperative effort among Investigation are to Federal and State agencies, universities, and the o Determine the structure, composition and petroleum and mineral industries, evolution of the Alaskan lithosphere, TALI is promoted and coordinated by a three- person committee with representatives from the o Examine the role of accretion tectonics in the U.S. Geological Survey (USGS), the Alaska Division growth of Alaska, and of Geological and Geophysical Surveys (ADGGS), o Investigate the post-amalgamation behavior of and the University of Alaska, Fairbanks (UAF). This Alaska and the origin of major geologic committee disseminates information on the features-mountain chains, sedimentary basins, objectives, plans, and progress of TALI and seeks to regional fault zones, seismic belts, and stimulate collaboration among potential volcanoes. investigators. The primary objective of TALI is to obtain a An advisory committee, consisting of scientists continuous geologic and geophysical profile acrcas from industry, government, and academia, is being Alaska by the end of this decade. Particular established to review periodically the aims and emphasis is placed on seismic-reflection and accomplishments of TALI, to recommend topics for refraction profiling and other geophysical methods and priorities of future work, and to foster to resolve the structure of the crust and underlying participation and cooperation, mantle and to relate surface geology to structures The TALI organization, consisting of the at depth inferred from geophysics. coordinating and advisory committees, provides Benefits.-TALI will substantially improve knowl- information and recommendations to participants edge of the State's geologic framework, especially and funding sources but does not engage in funding in the subsurface, and will yield new insights into activities. the geologic processes that have shaped the crust. Studies directly focused on TALI have been Improved knowledge of the geologic framework initiated by the USGS, in its Trans-Alaska Crustal will Transect (TACT) project, and by Rice University o Facilitate evaluation of the State's oil and and the UAF with support from the Department of mineral potential, and Energy, the National Science Foundation, and the petroleum industry. The ADGGS and individual o Provide a regional context in which to interpret scientists from several universities and companies detailed subsurface studies completed by are collaborating in many of these studies. The industry and others along the transect corridor. total support for these studies in 1985 was about $2 million. Many other geologic and geophysical investigators who wish to pursue a particular study investigations that contribute to the goals of TALI and to agencies and companies that are asked to are also being conducted by industry, universities, support a particular effort. The ultimate scope and and government along or near the transect corridor. accomplishments of TALI will depend on the interests of those who choose to participate in the program and their success in obtaining