Geology and Tectonic History of the Lower Cape Fear River Valley, Southeastern North Carolina U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1466 - A Geology and Tectonic History of the Lower Cape Fear River Valley, Southeastern North Carolina By DAVID R. SOLLER SURFACE AND SHALLOW SUBSURFACE GEOLOGIC STUDIES OF THE CAROLINA COASTAL PLAINS U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1466-A A study of a major river valley on the outer Atlantic Coastal Plain including mineralogic analysis of the deposits and geomorphic evidence for tectonic uplift UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1988 DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Any use of trade names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Geological Survey Library of Congress Cataloging in Publication Data Seller, D.R. (David R.) Geology and tectonic history of the lower Cape Fear River valley, southeastern North Carolina. (U.S. Geological Survey professional paper ; 1466A) Bibliography: p. 1. Geology North Carolina Cape Fear River valley. 2. Cape Fear River valley (N.C.) I. Title. II. Series. QE148.C35S65 1988 557.3 s [557.56'2] 86-600245 For sale by the Books and Open-File Reports Section, U.S. Geological Survey Federal Center, Box 25425, Denver, CO 80225 CONTENTS Page Page Abstract........................................................................................................ Al Mineralogy of the fluvial and upland deposits Continued Introduction.................................................................................................... 1 Clay-sized fraction............................................................................A25 Acknowledgments........................................................................................ 2 Weathering processes and patterns ...................................................... 33 Geographic setting........................................................................................ 2 Weathering of the upland deposits................................................ 39 Geologic setting ............................................................................................ 3 Weathering of the fluvial deposits ................................................ 39 Previous investigations................................................................................ 6 Weathering of the dune deposits.................................................... 40 General stratigraphy .................................................................................. 8 An estimate of the ages of dunes and Carolina bays ........................ 41 Study approach.............................................................................................. 9 Geomorphic evidence for uplift of the Cape Fear River valley...... 42 Sample localities .......................................................................................... 9 Longitudinal profiling...................................................................... 43 Methods of analysis...................................................................................... 9 Local uplift of the Cape Fear River valley.................................. 46 Radiocarbon data........................................................................................ 11 Cause of the elevated shorelines...................................................... 50 Pollen data.................................................................................................... 11 Comparison of the Cape Fear and Pee Dee River valleys .............. 52 Identification and correlation of terraces............................................ 12 Upland drainage patterns and regional tectonics .................... 53 Gross lithology and thickness of the fluvial deposits........................ 15 Summary...................................................................................................... 54 Mineralogy of the fluvial and upland deposits .................................. 18 References .................................................................................................... 56 "Heavy" sand-sized fraction ............................................................ 18 Appendix: Drill-site locations.................................................................. 59 "Light" sand-sized fraction.............................................................. 19 ILLUSTRATIONS Page PLATE 1. Geologic map of the Cape Fear River valley and surrounding upland areas.................................................. In pocket Page FIGURE 1. Map showing location of the study area .............................................................................................. ........ A2 2. Landsat image of the study area........................................................................................................................... ..3 3. Aerial photograph of the lower Cape Fear River valley showing Carolina bays and sand dunes..................................4 4. Maps presenting geologic evidence for the Cape Fear arch................................................................. ............. .5 5. Map showing location of drill sites within the study area ................................................................................ .. 10 6. Cross sections of the Cape Fear River valley along four auger hole transects......................... 13 7. Aerial photograph of the Cape Fear River valley and uplands near Garland, N.C. .................................................. 14 8. Aerial photograph of the Cape Fear River valley showing diversion of Colly Creek by migrating dunes .................. 16 9. Aerial photograph of the lower reaches of the Cape Fear River valley showing the Socastee and Wando terraces. .. .. ..............................................................................................._^ 10,11. Diagrams comparing lithology and sand mineralogy of auger hole samples of: 10. Upland deposits.......................................................................................................................................... 20 11. Valley deposits ...................................................................................................................... ..... 22 12-17. Maps of the Cape Fear River valley showing variations in: 12. Hornblende abundance in the fluvial sediments............................................................... ... ..... 29 13. Epidote abundance in the fluvial sediments......................................................................... ...... .... 29 14. Hornblende abundance in the dune sands ......................................................................... .. .. .. 30 15. Epidote abundance in the dune sands..................... ...................... ... ... 30 16. Feldspar abundance in the fluvial sediments .............................................. 31 17. Feldspar abundance in the dune sands................................................................. 31 18,19. X-ray diffraction traces of the untreated clay-sized fraction in samples of: 18. Upland deposits................................................................................................................................... 32 19. Valley deposits ............................................................................................................................... 34 20. Graph showing the rate at which the Cape Fear River has migrated to the southwest............... 43 in IV CONTENTS Page FIGURE 21-26. Diagrams showing: 21. Longitudinal profiles of fluvial terrace upper surfaces in the Cape Fear River valley................................ A44 22. Hypothetical profiles of a graded river along a stable continental margin .................................................. 45 23. Hypothetical profiles along a tectonically active continental margin............................................................ 45 24. Uplift of the Cape Fear River valley as measured by a best fit procedure on longitudinal profiles................ 46 25. Profile reconstruction used to assess the accuracy of the best fit procedure for profiling.............................. 47 26. Reconstructed profiles for all intervals of deposition since Waccamaw time (early Pleistocene).................... 48 27. Diagram comparing southeastern Atlantic Coastal Plain deposits with major interglacial oxygen isotope stages .............................................................................................................................................................. 51 28. Generalized location map showing major drainage and cities between the Pee Dee and Cape Fear Rivers, South Carolina and North Carolina ........................................................................................ ............. .... 52 TABLES Page TABLE Generalized late Cenozoic stratigraphy for the outer Coastal Plain of parts of North Carolina and South Carolina ................................................................................................................................................................................................. A9 Radiocarbon data for peat and macerated wood samples ........................................................................-..........-...--.--.....-.~~ 11 Pollen data...................................................................................................................................................................................................