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Stratigraphy and Depositional Environments of Lower and Middle Cambrian Strata in the Lake Mead Region, Southern Nevada and Northwestern Arizona

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Stratigraphy and Depositional Environments of Lower and Middle Cambrian Strata in the Lake Mead Region, Southern Nevada and Northwestern Arizona UNLV Retrospective Theses & Dissertations 1-1-1997 Stratigraphy And Depositional Environments Of Lower And Middle Cambrian Strata In The Lake Mead Region, Southern Nevada And Northwestern Arizona Joseph Kirk Hardy University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Hardy, Joseph Kirk, "Stratigraphy And Depositional Environments Of Lower And Middle Cambrian Strata In The Lake Mead Region, Southern Nevada And Northwestern Arizona" (1997). UNLV Retrospective Theses & Dissertations. 6. http://dx.doi.org/10.25669/v7dt-e0l5 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. INFORMATION TO USERS This reproduction was made from a copy of a document sent to us for microfilming. While the most advanced technology has been used to photograph and reproduce this document, the quality of the reproduction is heavily dependent upon the quality of the material submitted. 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When a map, drawing or chart, etc., is part of the material being photographed, a definite method of “sectioning” the material has been followed. It is customary to begin filming at the upper left hand corner of a large sheet and to continue from left to right in equal sections with small overlaps. If necessary, sectioning is continued again—beginning below the first row and continuing on until complete. 4. For illustrations that cannot be satisfactorily reproduced by xerographic means, photographic prints can be purchased at additional cost and inserted into your xerographic copy. These prints are available upon request from the Dissertations Customer Services Department. 5. Some pages in any document may have indistinct print. In all cases the best available copy has been filmed. University Micrdfilms International 300 N. Z eeb Road Ann Arbor, Ml 48106 Order Number 1331529 Stratigraphy and depositional environments of Lower and Middle Cambrian strata in the Lake Mead region, southern Nevada and northwestern Arizona Hardy, Joseph Kirk, M.S. University of Nevada, Las Vegas, 1986 Copyright ©1988 by Hardy, Joseph Kirk. All rights reserved. U MI 300 N. Zeeb Rd. Ann Arbor, MI 48106 PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V . 1. Glossy photographs or pages_____ 2. Colored illustrations, paper or print______ 3. Photographs with dark background 4. Illustrations are poor copy______ 5. Pages with black marks, not original copy______ 6. Print shows through as there is text on both sides of p_______ a g e 7. Indistinct, broken or small print on several pages ^ 8. Print exceeds margin requirements______ 9. Tightly bound copy with print lost in spine_______ 10. Computer printout pages with indistinct ______print 11. Page(s)___________ lacking when material received, and not available from school or author. 12. Page(s) seem to be missing in numbering only as text follows. 13. Two pages numbered . Text follows. 14. Curling and wrinkled pages 15. Dissertation contains pages with print at a slant, filmed as received 16. Other University Microfilms International STRATIGRAPHY AND DEPOSITIONAL ENVIRONMENTS OF LOWER AND MIDDLE CAMBRIAN STRATA IN THE LAKE MEAD REGION, SOUTHERN NEVADA AND NORTHWESTERN ARIZONA by Joseph Kirk Hardy A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geology Department of Geoscience University of Nevada, Las Vegas December, 1986 The thesis of Joseph Kirk Hardy for the degree of Master of Science is approved. h . Chairperson, Stephen M. Rowland A jlJL Examinjing Conunittee Member, Margaret N. Rees Examining Committee Member, Frederick W. Bachhuber Graduate Faculty Representative, Evangelos A. Yfantis Graduate Dean, Ronald W. Smith University of Nevada Las Vegas, Nevada December, 1986 ©1988 JOSEPH KIRK HARDY All Rights Reserved ABSTRACT Lower and Middle Cambrian strata in the Lake Mead region of southern Nevada and northwestern Arizona are divisible into four lithologically heterogeneous formations. The oldest of these, the Lower Cambrian Tapeats Sandstone, rests nonconformably upon Proterozoic crystalline basement rocks, is characteristically cross­ stratified, and consists primarily of medium- to thick- bedded, medium to coarse sand-sized, well-sorted, subrounded, texturally supermature, silica-cemented quartzarenite. The recessive Lower and Middle Cambrian Pioche Shale gradationally overlies the Tapeats Sandstone and consists of greenish or reddish mudrock interbedded with thin lenses or beds of cross-stratified, glauconitic sandstone. A reddish, ledge-forming, flaggy sandstone unit— herein informally named the Diamond Bar Sandstone Member— occurs in the upper half of the Pioche Shale in all but northernmost parts of the study area. The cliff- forming, Middle Cambrian Lyndon Limestone gradationally overlies the Pioche Shale and typically consists of a light gray or light brown weathering, medium- to thick- bedded, very well indurated, partially recrystallized and dolomitized limestone. The youngest formation studied, the Middle Cambrian Chisholm Shale, sharply overlies the Lyndon Limestone and typically consists of greenish or iii. reddish mudrock intercalated with thin grainstone beds. The Lyndon and Chisholm formations show an antithetic thickness relationship that suggests the existence of a generally east-west oriented, early Middle Cambrian carbonate bank near the center of the study area. Nine intergradational lithofacies are recognized within Lower and Middle Cambrian strata in the Lake Mead region. Each of these facies is inferred to represent a shallow-subtidal, intertidal, or supratidal paleoenvironment. The depositional model proposed for these lithofacies, based solely on vertical facies relationships with limited biostratigraphic control, involves seaward progradation of terrigenous siliciclastic sediments and the expansion of carbonate-accumulation areas in response to variation in the rates of relative sea-level rise and sedimentation. During times of slow relative sea-level rise, terrigenous siliciclastics were deposited throughout that portion of the Cambrian shelf that now lies within the study area. When the rate of relative sea-level rise was rapid, however, siliciclastic sedimentation was confined to coastal areas, allowing carbonates to accumulate. TABLE OF CONTENTS Introduction......................................................1 Purpose....................................................... 1 Regional Setting............................................ 2 Methods of study............................................ 5 Previous study: Stratigraphy............................ 14 Lake Mead region...................................... 14 Grand Canyon region...................................17 Pioche region..........................................19 Spring Mountains--Death Valley region.............21 Previous study: Depositional environments.............. 24 Lake Mead region...................................... 24 Grand Canyon region...................................24 Pioche region..........................................27 Spring Mountains— Death Valley region.............28 Stratigraphy.....................................................35 Spring Mountains— Death Valley region...................35 Pioche region...............................................36 Grand Canyon region....................................... 38 Lake Mead region........................................... 42 Tapeats Sandstone..................................... 48 Pioche Shale........................................... 59 Lyndon Limestone...................................... 70 Chisholm Shale.........................................77 Summary...................................................... 81 Paleoenvironmental Analysis...................................85 Facies description.........................................85 Facies A: Thinly bedded, friable sandstone..........................................85
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