Pennsylvanian and Associated Rocks in Wyomin
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Pennsylvanian and Associated Rocks in Wyomin By WILLIAM W. MALLORY SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY GEOLOGICAL SURVEY PROFESSIONAL PAPER 5S4-G A regional study of the extent, thickness, lit ho logy, and stratigraphic relations of the Tensleep, Ams- den, Casper, and Fountain Formations, with em phasis on origin,paleogeography, and paleotectonic implications UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967 UNITED STATES DEPARTMENT OF THE INTERIOR STEWART L. UDALL, Secretary GEOLOGICAL SURVEY William T. Pecora, Director For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract. _________________________________________ Gl Casper Formation._________________________________ G17 Introduction. ______________________________________ 1 Fountain Formation._______________________________ 18 Location and extent of the area. _ _________________ 1 Minnelusa and Hartville Formations __________________ 18 Scope and objectives. ___________________________ 1 Morgan Formation and Weber Sandstone-_____________ 20 Previous work and acknowledgments. ____________ 2 Rocks of Morrow age in the Minnelusa, Hartville, Casper, Methods of study. _____________________________ 2 and Morgan Formations..___________-_-_--______-_ 20 Tectonic setting of the Middle Rocky Mountain region in Tensleep Sandstone._____-____________------------__ 21 Pennsylvanian time.. _ ____________________________ 3 Lithology and thickness.___-_-____-------_______ 21 Definition of the Pennsylvanian System in Wyoming. ___ 4 Extent and thickness of the Pennsylvanian System. _____ 5 Age.__---__________------------------------_-_ 21 Lower boundary of the Pennsylvanian System. _________ Quadrant Quartzite.______________-_----_---_-______ 22 Character of the disconformity- __________________ Lithology and thickness-________________________ 22 Time span of the hiatus in Wyoming. _____________ Age____._____________-_________------_-------- 22 Paleogeomorphology of the disconformity in north Rocks of Des Moines, Missouri, and Virgil age_________ 23 western Wyoming. ___________________________ Des Moines rocks__________________.-__--_______ 23 Interregional significance of the disconformity on Missouri rocks__________-_--____-_---__--------_ 23 the craton. __________________________________ Virgil rocks.________-____________----_--------- 24 Amsden Formation. _ _______________________________ Upper Boundary of the Pennsylvanian System.________ 25 Lithologic units. _______________________________ 8 Source of sand_-__-_________--__-___-_-_--_--------- 25 10 Nomenclature and the Amsden problem. 10 Tabulation of control data-_-______-___--_----------- 27 Darwin Sandstone Member. ___ ________ 11 Surface-______________-___-______---_---------- 27 Horseshoe Shale Member. ____________ 12 Subsurface..-_____-_-----------------------_--- 28 Ranchester Limestone Memb er _ _____ 14 References cited.___________________________________ 30 ILLUSTRATIONS [Plates are in pocJietJ PLATE 1. Correlation diagrams (stratigraphic sections) of Pennsylvanian and Mississippian rocks in the Middle Rocky Mountain region, Wyoming, showing relation of lithologic units and approximate time boundaries. 2. Maps showing extent, thickness, and lithology of members of the Amsden Formation of Mississippian and Pennsyl vanian age, and correlative formations in the Middle Rocky Mountain region. 3. Maps showing extent, thickness, and lithology of Tensleep Sandstone (except that part of Permian age) and total thickness of the Amsden, Tensleep, and correlative formations in the Middle Rocky Mountain region. Page FIGURE 1. Index map showing location of report area._______________________-__------_--------------------------- G2 2. Index map showing position of Ancestral Rocky Mountains relative to existing ranges and basins in Wyoming-_ 3. Correlation chart of Pennsylvanian and closely related strata in Wyoming.____________-_------------------ 4. Index map of Wyoming showing areal extent of Pennsylvanian formations and exposed Precambrian basement rock in existing mountain ranges__________________________-_--__---------------------------------- 5. Photograph showing erosional disconformity between Amsden Formation and Madison Limestone in Wind River Canyon, south of Thermopolis, Wyo.______________-_____--_--------------------------------- 6. Type and reference sections of Amsden Formation.______________________--_---------------------------- 9 7. Photographs showing crossbedding in Darwin Sandstone Member, Tensleep Canyon.__________-_------------ 12 8. View of north wall of Tensleep Canyon near trout-rearing station showing the top of the Madison Limestone, the three members of the Amsden Formation, and the lower part of the Tensleep Sandstone.___________ 9. Paleogeologic map showing areal geology of Pathfinder uplift at end of Atoka time and thickness and lithology of Ranchester Limestone Member of Amsden Formation in area surrounding the uplift____-------------- 10. Photograph of the red marker on east fork of Wagonhound Creek, west of Arlington, Carbon County, Wyo____ 11. Geologic section showing generalized correlation of Pennsylvanian and Permian rocks across southern part of Laramie basin and Laramie Mountains, Wyo. and Colo.________--_-----_--- -__-_-------------_-- in IV CONTENTS Page FIGUBE 12. Photograph of Tensleep Sandstone in Sinks Canyon of Middle Popo Agie River__._________________________ G21 13. Photograph showing giant crossbedding in the Tensleep Sandstone, Bull Lake Canyon, Wind River Range.___ 22 14. Map showing western limits of Missouri and Virgil rocks in central Wyoming._____________________________ 24 15. Formations which overlie Pennsylvanian strata in Wyoming.____________________________________________ 25 16. Map showing restored regional drainage patterns for Carboniferous time in northern United States and southern Canada.___-_-___________________________--______-__-__--___----_-_---_----------------------_- 26 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY PENNSYLVANIAN AND ASSOCIATED ROCKS IN WYOMING By WILLIAM W. MALLORY ABSTRACT southern part of the Pathfinder uplift were deposited in the Laramie basin area as the Fountain Formation. The Pennsylvania!! System in the Middle Rocky Mountains of In Des Moines time the Tensleep Sandstone was deposited on a Wyoming is represented principally by the Amsden and Ten- broad marine shelf over most of the area, while limestone, sand sleep Formations. These grade eastward into the Minnelusa, stone, and shale of the Hartville and Minnelusa Formations were Hartville, Casper, and Fountain Formations, and southward in deposited in eastern Wyoming. Arkose was deposited in dimin to the Weber and Morgan Formations. The Amsden Formation ishing quantities in the Laramie basin area during Atoka, Des has three members: the Darwin Sandstone at the base, the Horse Moines, Missouri, and Virgil times. In Missouri and Virgil time, shoe Shale (new name) in the middle, and the Ranchester Lime western Wyoming was emergent, and some sand derived from stone (new name) at the top. The Darwin is of Chester (Mis the Des Moines Tensleep there was removed and redeposited in sissippian) age; the Horseshoe is of Chester and Morrow ages; central Wyoming. and the Ranchester is of Morrow age at the base but is mostly The Pathfinder uplift had its greatest extent and elevation in of Atoka age. Atoka time and was progressively submerged later in the The Tensleep Sandstone (and its equivalent, the Quadrant Pennsylvanian. It ceased to exist in late Virgil or Early Permian Quartzite, in the Yellowstone Park area) is entirely of Des Moiues age in the Bighorn and Wind River Basins. In central time. Wyoming, however, the Tensleep contains beds of Missouri, Vir INTRODUCTION gil, and Early Permian ages. The Minnelusa and Hartville For mations in the eastern part of the State contain interbedded LOCATION AND EXTENT OF THE AREA sandstone, shale, and carbonate rock ranging in age from Morrow to Early Permian. The Casper is composed of sandstone and car The report area is the State of Wyoming except six bonate rock and grades southward into red arkosic conglomerate counties on the east side of the State (Campbell, Crook, of the Fountain Formation in the Laramie basin and adjacent Weston, Niobrara, Goshen, and most of Laramie areas. The Casper and Fountain Formations also range in age County) and the thrust belt along the west side (much from Morrow to Early Permian, but the older strata are missing in a wide area in central Wyoming where the Pathfinder uplift, of Lincoln County and parts of adjacent counties) (fig. the northernmost element of the Ancestral Rocky Mountains, 1). The area spans 4° of latitude (41°-4r5° N.) and dominated the paleogeographic scene. 6° of longitude (105°-111° W.) and encompasses about In Late Mississippian time the Mississippian Madison Lime 70,000 square miles. Physiographically it is dominated stone was exposed throughout the area except in the Laramie by the Middle Eocky Mountains. basin and adjacent mountains, where the Precambrian basement rocks were exposed. A karst surface formed in many areas on SCOPE AND OBJECTIVES the Madison in Late Mississippian time. In late Chester and per haps early Morrow time, marine waters spread eastward across The stratigraphy of the Pennsylvanian System in the Wyoming from the geosyncline in southern Idaho and invaded Middle Eocky Mountain region is generally simple, but the major valleys first and later covered nearly all the Madison understanding