A STUDY OF THE CHINLE-SHINARUMP BEDS IN THE LEUPP-HOLBROOK AREA, ARIZONA Item Type text; Dissertation-Reproduction (electronic) Authors Smith, Riley Seymour, 1908- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 03/10/2021 20:12:05 Link to Item http://hdl.handle.net/10150/298688 A STUDY OF THE CHINLE-SHINARUMP BEDS IN THE LEUPP-HOLBROOK AREA, ARIZONA by Riley S*-1 Smith, Jr. A Thesis Submitted to the Faculty of the DEPARTMENT OF GEOLOGY In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College UNIVERSITY OF ARIZONA 195 7 STATEMENT BY AUTHOR This thesis has been submitted in partial fulfill­ ment of requirements for an advanced degree at the University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library. Brief quotations from this thesis are allowable without special permission, provided that accurate aclaiowl- edgement of source is made. Requests for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in their Judgment the proposed use of the material Is in the inter­ ests of scholarship. In all other instances, however, per­ mission must be obtained from the author. SIGNED APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below: JOHN F. LANCE Professor of Geology CONTENTS Page LIST OF PLATES ill LIST OF TABLES V LIST OF FIGURES vi ABSTRACT vil. INTRODUCTION 1 Purpose and Scope 2 Location and Description of Area 2 Methods Used in the Investigation 3 Field work 4 Acknowledgements 4 TOPOGRAPHY 7 Rock Exposures 8 STRATIGRAPHY", PETROGRAPHY, AND SEDIMENTATION 9 Historical Sketch of the Shlnarump and Chinle Formations in the Plateau Region 9 General Stratigraphic Relations 11 Shinarurap Conglomerate 14 Areal Extent and Thickness 14 Topographic Expression 16 Relationship to Overlying and Underlying ,r Formations 17 Moenkopi-Shinarump Contact 17 Shinarurap-Chinle Contact 18 Lithologic Aspects of the Shinarump Conglomerate 19 The Shlnarump in the Leupp-Holbrook Area.. 21 Heavy Mineral Studies 27 Primary Structures 29 Secondary Structures 29 Age of the Shinarump Conglomerate 29 Chinle Formation 30 Extent and Thickness 30 i Page Topographic Expression 31 Relationship to Underlying and Overlying Rooks 31 Subdivisions of the Chinle Formation 32 Nomenclature Used in This Paper ., 34 The Chinle in the Leupp-Holbrook Area 34 Lower Member 38 Bentonite In the Leupp-Holbrook Area 39 Petrified Forest I-Iember 43 Owl Rock Member 45 Limestones 48 Marlstones 50 Porcellanites 51 Genesis of the Limestones and Porcellanites 54 Facies Changes in the Leupp-Holbrook Area. 57 Age Determinations 60 PALEOGEOGHAPHY AND SOURCES OF SEDIMENT 61 SUMMARY AND CONCLUSIONS 65 APPENDIX NO. 1 68 Shinarump Field and Laboratory Studies 68 APPENDIX NO. 2 89 Chinle Field and Laboratory Studies 89 PLATES... 125 BIBLIOGRAPHY. 165 11 PLATES Plates Pag© X. Map showing Areal Geology of the Leupp- Holbrook Area, Arizona in pocket II. Chinle Cross-section and Correlations... in pocket III-1. Lower member, near section 1 126 III-2. Lower member at section C 126 IV-1. Lava capped mesa southeast of Smith Butte 128 IV-2. Basalt dike at foot of Smith Butte 128 . V-1. Shinarump outlier resting on Koenkopi... 130 V-2. Unconformity "between Shinarump and Hoenkopi 130 VI-1. South side of Smith Butte 132 VI-2. Closer view of VI-1 132 VII-1. Shinarump outlier capped by lowermost Chinle shales and silt,stones 134 VII-2. Closer view of VII-1 134 VIII-1. Low Shinarumn outcrop near Leupp 136 VIII-2. Closer view of VIII-1 136 IX-1. Shinarump outlier on eroded Koenkopi.... 138 IX-2. Sandstone lens in Shinaruiap at Holbrook. 138 X-1. Silicified log in Shinarump sands, be­ tween Joseph City and Holbrook 140 X-2. Cross-lamination in the Shinarump at location 2, north of "Winslow 140 XI-1. South side of Smith Butte, showing con­ tact of Owl Rock and '/Ungate sandstone.. 142 XI-2. Smith Butte; contact between Owl Rock and overlying Wingate 142 XII-1. Newberry Ilesa, £ mi. northeast of Leupp. 144 XII-2. Closer view of 23-D, showing poorly de­ fined cross-stratification 144 iii Plates Page XIII-1. Agatized tree trunk from Lower member of the Chinle formation 146 XIII-2. Unit 16 at section C, northeast of Joseph City 146 XIV-1. Porcellanite in the Owl Rock member at Location I, 18 ml. northeast of Winslow.. 148 XIV-2. Thick porcellanite, capping mesa at Loca­ tion Or, east of Leupp 148 XV-1. Unit 23-D at section E 150 XV-2. Unit 23-D at section E, showing "root-like" features 150 XVI-1. Unit 21-D at section E 152 XVI-2. Unit 23-D at Smith Butte 152 • ' XVII-1. Badlands in Lower member of Chinle, 10 miles west of Joseph Cit2r 154 XVII-2. Bentonite weathering on slope in the Lovrer member at section C, 5 ml. northeast of Joseph City . 154 XVIII-1. Cross-stratification in mudstone, 10 ml. west of Joseph City 156 XVIII-2. Cross-stratification in bentonitic clays in Pet. Forest member, HE of Winslow 156 XIX-1 . Portion of section G-, unit 23-D 158 XIX-2. Section K, showing unit 23-D capping the mesa unit 21 ~D 158 XX-1. Cross-bedding in siltstone layers in the Lower member, section D, ITW of Leupp 160 XX-2. Small unconformity between two units of Lower member, HE of Joseph Citysection C 160 XJCI-1. Cliff-forming layer of the Owl Rock member, 18 mi. IIE of Winslow, section I.. 162 XXI-2. Slump structure in Owl Rock, section I... 162 XXII-1. Unit 23-D capping marlstones of Petrified Forest member, 7 ml. IT of Winslow, sec. E 164 XXII-2. Unit 23-D at section I, 18 ml. NE of Win. 164 lv TABLES Page Table 1. Statistical Data on Gravel-size Samples of Shlnarump conglomerate 28 Table 2. Comparisons of the Various Rock Types.... 37 Table 3. Distribution of Bentonite 41 Table 4. Llthologic Types Found in the Chinle Formation.. 59 Table 5. Gravel Analysis at Location No. 1 69 Table 6. Size Analysis of the Matrix at Location No. 1 70 Table J. Gravel Analysis at Location No, 2 74 Table 8. Size Analysis of the TThole Rock at Location No. 3 77 Table 9. Description of Gravel-sized. Constituents at Location Uo. 3 78 Table 10. Gravel Analysis at Location No. 4 82 Table 11. Size Analysis of the Matrix at Location No. 4 83 Table 12. Gravel Analysis at Location No. 5 86 Table 13. Gravel Analysis at Location No. 6 88 v FIGURES Pas© Fig. 1. Index Map of Thesis Area 5 Fig. 2. Planar Cross-stratification and Trough Cross-stratification 24 Fig. 3. Map Showing Shinarump Cross-stratification Trends 25 Fig. 4. Histogram showing grain size of the matrix at Location Ho. 1 70 Fig. 5. Histogram showing grain sise of the Shinarump at Location No. 3 77 Fig. 6. Histogram showing grain sise of the matrix at Location Ho. 4 83 Ti ABSTRACT The Shinarump and Chinle beds were investigated in the Leupp-Holbrook area of northeastern Arizona. Cross- stratification trends and cobble studies suggest a south­ eastern source for the material. A southwestern source direction is also postulated by the presence of Kaibab fossils, gray quartzite, and granite cobbles. The possibil­ ity exists that the granite and quartzite are from the Brad- shaw Mountains near Prescott. Coarse clastic facies in the Lower member of the Chinle show a decrease in quantity and grain size toward the northwest, correlating with the Shinarump findings. Another notable change is the thinning out and disappearance of some of the cliff-forming Upper Chinle units as they are traced southeastward from Leupp to Smith Butte. The most useful feature for stratigraphic control in the area is a resistant, cliff-forming, porcellanlte bed, found at the base of the Owl Rock, the uppermost member of the Chinle.formation. Some of the "limestones" of the Chinle formation in the area were found to be true limestones, but others are marlstones and porcellanites. The lime is believed to have vii been precipitated by evaporation from shallow, flood plain, lake waters. The soluble salts may have been flushed out by vraters from associated streams during flood stage. The silica responsible for the highly siliceous nature of cer­ tain Owl Rock units is believed to have been released by the decomposition of reworked volcanic ash and its conversion into montmorillonite. Silica carried by groundwater possib­ ly enriched the already siliceous rocks. The chert is secondary. Some substantiating evidence is offered for the concept of the Shinarump as a regressive, blanket deposit, and the Chinle as transgresslve, upward building deposit. vlli INTRODUCTION The Colorado Plateau, which includes the Leupp- Holbrook area, was first explored in 1540 "by Coronado and in 1776 by Escalante and other padres. The first geologist to visit the area described in this paper was Marcou (1856) who accompanied Lt. Whipple 011 his 1853 expedition to locate a transcontinental railroad route. Their party skirted the south edge of the region, following approximately the route used today by the Sante Pe railroad. The first geologist to actually traverse the Painted Desert was Newberry (1861) who was geologist of the expedition led by Lt.