Hydrogeology of Jurassic and Triassic Wetlands in the Colorado Plateau and the Origin of Tabular Sandstone Uranium Deposits U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1548 AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications re­ leased prior to the current year are listed in the most recent annual "Price and Availability List." Publications that may be listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" may no longer be available. 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Quesenberry Photocomposition by Carol A. Quesenberry For Sale by U.S. Geological Survey, Map Distribution Box 25286, MS 306, Federal Center Denver, CO 80225 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 Sanford, Richard F. Hydrogeology of Jurassic and Triassic wetlands in the Colorado Plateau and the origin of tabular sandstone uranium deposits / by Richard F. Sanford. p. cm.—(U.S. Geological Survey professional paper ; 1548) Includes bibliographical references. Supt.ofDocs.no. : I 19.16: 1548 1. Paleohydrology—Colorado Plateau. 2. Geology, Stratigraphic—Jurassic. 3. Geology, Stratigraphic—Triassic. 4. Geology—Colorado Plateau. I. Title. II. Series QE39.5.P27S26 1995 553.4'932'097913—dc20 94-15974 CIP CONTENTS Abstract................................................................................................................................. 1 Introduction.......................................................................................................................... 1 Description of Tabular Sandstone Uranium Deposits.................................................. 1 Hydrogeological Principles Used in Reconstruction............................................................ 2 Controls on Ground-Water Flow.................................................................................. 2 Topography........................................................................................................... 2 Geology................................................................................................................ 2 Aquifers and Confining Units............................................................................... 3 Composition......................................................................................................... 3 Features of Ground-Water Flow................................................................................... 4 Scale of Ground-Water-Flow Systems................................................................. 4 Compositional Variations..................................................................................... 4 Recharge and Discharge in Fluvial-Lacustrine Environments............................. 4 Transient Effects and Water-Table Variations..................................................... 4 Paleohydrogeology in the Colorado Plateau ........................................................................ 5 Major Controls on Late Jurassic Ground Water........................................................... 5 Topography........................................................................................................... 5 Geology................................................................................................................ 5 Composition......................................................................................................... 7 Salt Wash Sandstone Member of the Morrison Formation.......................................... 7 Recapture Member of the Morrison Formation............................................................ 11 Westwater Canyon Member of the Morrison Formation............................................. 13 Brushy Basin Member of the Morrison Formation...................................................... 15 Jackpile Sandstone Member of the Morrison Formation............................................. 17 Lower Part of the Chinle Formation............................................................................. 19 Topographic Controls on Ground-Water Flow .................................................... 23 Geologic Controls on Ground-Water Flow.......................................................... 23 Diagenesis and Uranium Deposition.................................................................... 25 Origin of Tabular Sandstone Uranium Deposits.................................................................. 26 Role of Humate............................................................................................................. 26 One or Two Solutions?................................................................................................. 27 Seepage, Compaction, and Density.............................................................................. 27 Transient, Depression-Focused Ground-Water Recharge............................................ 29 Summary and Conclusions................................................................................................... 31 References Cited................................................................................................................... 34 FIGURES 1. Diagram showing classification of topographic, geologic, and compositional controls on ground water showing conditions favorable for discharge................................................................................................................ 3 2. Map showing major geologic features that influenced ground-water flow in the Late Jurassic in the Colorado Plateau region.............................................................................................................................................. 6 3. Simplified map and cross section of the Colorado Plateau for Late Jurassic time at end of deposition of the Salt Wash Sandstone Member of the Morrison Formation............................................................................... 8 4. Generalized map showing source rocks for solutes in ground water in the Colorado Plateau region........................ 9 5. Schematic cross section showing influences on ground-water flow in the Colorado Plateau region during the Late Jurassic at the end of deposition of the Salt Wash Sandstone Member of the Morrison Formation..................