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E-146,701 C St. Maps For maps, address mail orders to U.S. Geological Survey, Map Distribution Maps Federal Center, Box 25286 Maps may ^ purchased over ^ counter at the U.S. Geologi- Uenver, CO 80225 caj Sm^gy offices where books are sold (all addresses in above list) and at the following Geological Survey offices: Residents of Alaska may order maps from ROLLA, Missouri-1400 Independence Rd. Alaska Distribution Section, U.S. Geological Survey, . DENVER, Colorado-Map Distribution, Bldg. 810, Federal New Federal Building-Box 12 Center 101 Twelfth Ave., Fairbanks, AK 99701 . FAIRBANKS, Alaska-New Federal Bldg., 101 Twelfth Ave. Geologic Evolution of Trail Ridge Eolian Heavy-Mineral Sand and Underlying Peat, Northern Florida By ERIC R. FORCE and FREDRICK J. RICH U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1499 The peat underlying ilmenite ore sand is a synchronous fades and records the approach of the eolian dune UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1989 DEPARTMENT OF THE INTERIOR MANUEL LUJAN, JR., Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. Government Library of Congress Cataloging in Publication Data Force, Eric R. Geologic evolution of Trail Ridge eolian heavy-mineral sand and underlying peat, northern Florida. (U.S. Geological Survey professional paper ; 1499) Bibliography: p. Supt. of Docs, no.: I 19.16: 1499 1. Heavy minerals Florida Trail Ridge. 2. Sand Florida Trail Ridge. 3. Peat Florida Trail Ridge. 4. Eolian pro­ cesses Florida Trail Ridge. 5. Geology Florida Trail Ridge. I. Rich, Fredrick J. II. Title. III. Series. QE364.2.H4F67 1989 553.4'6 88-607931 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............................................................................ 1 Nature of Trail Ridge Lignitic Peat....................................... 7 Introduction....................................................................... 1 General description....................................................... 7 Previous work.................................................................... 2 Petrography ................................................................ 8 Nature of the Trail Ridge ilmenite ore sand ............................ 3 Palynology................................................................... 9 Areal distribution and geologic relations........................... 3 Age........................................................................... 10 Sequence and structure ................................................. 4 The sand component of Trail Ridge peat.......................... 10 Sand morphology and grain size ...................................... 5 Depositional relation of Trail Ridge peat and sands ................. 14 Heavy minerals............................................................ 6 Paleogeographic reconstruction............................................ 15 Heavy-mineral variation with sedimentary structure .......... 6 Acknowledgments.............................................................. 15 Origin......................................................................... 7 References 15 ILLUSTRATIONS Page FIGURE 1. Location of Trail Ridge shown on a satellite thermal image............................................................................................. 2 2. Cross-sectional profile of Trail Ridge........................................................................................................................... 2 3. Diagrams showing lithologic features, percent leucoxenized ilmenite, and percent Ti02 in altered ilmenite, Trail Ridge ore body................................................................................................................................................................ 3 4. Photograph showing humate pseudobedding in Trail Ridge sand...................................................................................... 4 5. Photograph showing Trail Ridge ilmenite ore sand........................................................................................................ 5 6. Circular diagram of azimuths and magnitude of crossbed dip in Trail Ridge ilmenite ore sand .............................................. 5 7. Topographic map showing Trail Ridge localities discussed in the text............................................................................... 6 8. Scanning electron microscope photographs of grains from the Trail Ridge ore sand............................................................. 7 9. Photomicrograph of thin section of Trail Ridge ilmenite ore sand..................................................................................... 8 10. Photograph of laminae alternately rich and poor in heavy minerals .................................................................................. 8 11. Graphs comparing adjacent laminae rich and poor in heavy minerals ................................................................................ 9 12. Graphs showing palynological and maceral constituents of peat in core RTR2 .................................................................... 11 13. Photomicrograph of thin section of sandy lignitic peat from core RTR2............................................................................. 12 14. Scanning electron microscope photograph of sand-bearing lignitic peat sample from core RTR2............................................ 12 15. Graphs showing grain-size distributions of inorganic fraction of sandy Trail Ridge peat from core RTR2................................ 13 16. Scanning electron microscope photographs of sand grains in Trail Ridge peat from core RTR2............................................. 13 17. Photograph showing Holocene coastal transgressive longwall dune near Newcastle, New South Wales, Australia.................... 14 18. Schematic paleogeography of Trail Ridge at the time of dune formation............................................................................ 15 TABLE Page TABLE 1. Organic and sand constituents of core samples from Trail Ridge peat. ..10 ill GEOLOGIC EVOLUTION OF TRAIL RIDGE EOLIAN HEAVY-MINERAL SAND AND UNDERLYING PEAT, NORTHERN FLORIDA By Eric R. FORCE and Fredrick J. RICH ABSTRACT overlying sand are essentially the same age. Fine sand found in peat represents the sand fraction remaining suspended in flow separation at The