Surficial Geology And Quaternary History Of The Healy Lake Area, Alaska Item Type Thesis Authors Ager, Thomas Alan Download date 02/10/2021 19:32:01 Link to Item http://hdl.handle.net/11122/8326 INFORMATION TO USERS This dissertation was produced from a microfilm copy of the original document. While the most advanced technological means to photograph and reproduce this document have been used, the quality is heavily dependent upon the quality of the original submitted. The following explanation of techniques is provided to help you understand markings or patterns which may appear on this reproduction. 1. The sign or "target" for pages apparently lacking from the document photographed is "Missing Page(s)". If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. This may have necessitated cutting thru an image and duplicating adjacent pages to insure you complete continuity. 2. 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Silver prints of "photographs" may be ordered at additional charge by writing the Order Department, giving the catalog number, title, author and specific pages you wish reproduced. University Microfilms 300 North Zeeb Road Ann Arbor, Michigan 48106 A Xerox Education Company Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. MASTERS THESIS M-3895 AGER, Thomas Alan SURFICIAL GEOLOGY AND QUATERNARY HISTORY OF THE HEALY LAKE AREA, ALASKA. University of Alaska, M.S., 1972 Geology University Microfilms, A XEROX Com pany, Ann Arbor, Michigan 0 1972 THOMAS ALAN AGER ALL RIGHTS RESERVED Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SURFICIAL G EO LO G Y AN D QUATERNARY HISTORY OF THE HEALY LAKE AREA, ALASKA A THESIS Presented to the Faculty of the University of Alaska in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE By Thomas Alan Ager, B.S. College, Alaska M ay, 1972 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. SURFICIAL GEOLOGY AND QUATERNARY HISTORY OF THE HEALY LAKE AREA, ALASKA Chairman Department Head APPROVED: C d J Date / ? / C^ean o f the College o f Earth Sciences and Mineral Industry Vice President for Research and Advanced Study Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. PLEASE NOTE: Some pages may have indistinct print. Filmed as received. University Microfilms, A Xerox Education Company Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract Surficial geology of the Healy Lake area in the Tanana Valley, interior Alaska, records the effects of major regional climatic events of the late Pleistocene and Holocene. During the Delta Glaciation the area was subjected to severe periglacial conditions associated with ice wedge formation, solifluction, and intense eolian activity which ventifacted resistant bedrock fragments and deposited fin e sand and loess over much of the area. The Donnelly Glaciation was also characterized by periglacial conditions. Aggradation of the Tanana River floodplain by glacial outwash dammed the Healy River, impounding a large lake in the lower Healy Valley. Wave activity caused by strong southerly winds produced beaches along the north shore of the lake. The beach sediments served as a source for sand and silt which were deposited by wind on adjacent slopes, producing widespread sand sheets, dunes, and loess deposits. During the Holocene the environment of the area changed from grassland- tundra to boreal forest. The Donnelly-age lake was drained and its lacustrine deposits incised by the Healy River. Although loess deposition continued during the Holocene, the rate of accumulation and the mean grain size decreased. Bogs formed in the lower Healy Valley in the area previously covered by lake water. Permafrost development in the bogs was associated with thermokarst phenomena. Late in Holocene time, renewed aggradation of the Tanana River floodplain again dammed the Healy River, resulting in the formation of present-day Healy Lake. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CONTENTS Page INTRODUCTION 1 Previous Investigations 4 Present Investigation 5 Acknowledgements 6 REGIONAL SETTING 7 Climate 7 Vegetation 7 Permafrost 11 Soils 11 PHYSIOGRAPHIC PROVINCES 15 Alaska Range 15 Tanana Lowland 17 Yukon-Tanana Upland 19 REGIONAL HISTORY 23 Late Quaternary Events 24 Paleoecology 30 Holocene Environment 32 HEALY LAKE AREA 35 Local Setting 35 Vegetation and Permafrost 37 Bedrock Geology 40 Sediment Analysis 43 Test Pit Profiles 48 Surficial Geology 65 Eolian Deposits 65 Fluvial Deposits 70 Lacustrine and Related Deposits 77 II Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Page Holocene Lake Formation 83 Tectonic Considerations 89 Quaternary History of the Healy Lake Area: Summary 91 APPENDIX I: Test Pit Profiles 98 APPENDIX II: Factor Analysis Printouts 114 APPENDIX III: Sediment Interpretations 118 REFERENCES CITED 121 HI Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ILLUSTRATIONS (Plates 1 to 4 are in pocket) Plate I . Vegetation map of the Healy Lake area 3. Index map of test pit localities 4. Longitudinal profiles of the Tanana and Healy Rivers Page Figure 1. Index map of Alaska 2 2. Physiographic provinces of the Healy Lake region 3 3. Clim atic data for the Big Delta area 8 4. Vegetation and permafrost distribution diagram 10 5. Soils distribution diagram 13 6 . Extent of glaciations map of Healy Lake region 26 7. Aerial view of Healy Lake region from the north 36 8 . Map of lake channels and bedrock outcrops 42 9. Test Pit 13 profile 49 10. Test Pit 32 profile 53 11. Test Pit 43 profile 55 12. Test Pit 70 profile 57 13. Test Pit 75 profile 59 14. V illage Site Test Pit profile 62 15. V illage Site Test Pit sediment grain size diagram 63 16. Radiocarbon dates from the V illage Site 63 17. Bog processes diagram 74 IV Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Page Figure 18. Lower Healy River bog flats from the south 7 5 19. Lower Healy River bog flats during high water stage 76 20. North end of Healy Lake 84 21. Thaw lakes and lacustrine terrace 85 22. Goss section of thawing islands 8 6 23. Delta age moraines, upper Healy River 92 24. Donnelly age moraines, upper Healy River 93 25. Village Site hillside profile 112 Table 1. Glacial Chronology for the, Alaska Range and Yukon-Tanana Upland \ 25 2 . Vegetation units for Healy Lake area 39 3. Factor interpretations 44 4. Volcanic Ash analysis 51 5. Air photo identification criteria for surficial units 6 6 6 . Pebble lithologies from Ashes Point coring 78 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INTRODUCTION Healy Lake is located in the central Tanana Valley of interior Alaska about 108 miles southeast of Fairbanks (Fig. 1). The Tanana Lowlands here are bordered to the south by rugged glaciated mountains of the Alaska Range, and to the north by the lower hills and ridges of the Yukon-Tanana Upland (Fig. 2). The region is sparsely inhabited. Although the Alaska Highway follows the Tanana Lowlands just north of the Alaska Range, only a few unimproved roads extend short distances from the highway to cabin sites and sawm ills. Beyond the lim it o f roads, access to remote parts of the region is primarily by boat, float plane, all-terrain vehicles, or snow machines in w inter. Archeological evidence and radiocarbon dates from sites around the lake suggest that man occupied the area at least intermittently since about 1 1 , 0 0 0 years ago. Significant climatic fluctuations and resulting environmental changes have taken place during that period. Knowledge of these changes is vital to the interpretation of the culture and ecology of the early inhabitants. Healy Lake also displays unique characteristics which in themselves merit study. Aggradation o f the Tanana floodplain has dammed a number o f tributaries which drain from the Yukon-Tanana Uplands, resulting in the formation of Healy, Harding, Birch, George, and other lakes. Among the lakes formed in this manner, Healy Lake alone had glaciated headwaters during the late Pleistocene. The lake also displays an unusual characteristic of periodic flooding via its outlet channel by the silt-laden waters of the Tanana River. Geologic studies at Healy Lake were initiated in 1969. The primary objective was to reconstruct the history of environmental changes in the region during late Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Figure Is Index map of Alaska with location of the Healy Lake Region, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 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