The Mid-Cretaceous Frontier Formation Near the Moxa Arch, Southwestern Wyoming

The Mid-Cretaceous Frontier Formation Near the Moxa Arch, Southwestern Wyoming U.S. GEOLOGICAL SURiVEY PROFESSIONAL PAPER 1290! The Mid-Cretaceous Frontier Formation Near the Moxa Arch, Southwestern Wyoming By E. A. MEREWETHER, PAUL D. BLACKMON, and J. C. WEBB U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1290 A stratigraphic description, including some paleontologic and petrographic data, of lower Upper Cretaceous rocks in the Green River Basin UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON 1984 DEPARTMENT OF THE INTERIOR WILLIAM P. CLARK, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director Library of Congress Cataloging in Publication Data Merewether, E. A. (Edward Alien), 1930- The mid-Cretaceous frontier formation near the Moxa arch, southwestern Wyoming. (Geological Survey Professional Paper; 1290) Bibliography: 29 p. Supt. of Docs. No.: 119.16:1290 1. Geology, Stratigraphic Cretaceous. 2. Geology Green River Watershed (Wyo.-Utah) I. Blackmon, Paul D. II. Webb, J. C. III. Title. IV. Series. QE687.M468 1984 551.7'7 83-600107 For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 CONTENTS Page Abstract Core-sample descriptions . 13 Borehole 1 ........... Introduction ..... 13 Borehole 2 ........... Acknowledgments 15 Borehole 3 ........... 15 Previous work . Borehole 6 ............ 23 Stratigraphy ........... Borehole 8 ........... 23 Overthrust belt ....... Borehole 11 .......... 24 Uinta Mountains ...... Borehole 18 .......... 24 Moxa arch .......... Summary and interpretations 26 Stratigraphic interpretations References cited .......... 28 ILLUSTRATIONS FIGURE 1. Map of southwestern Wyoming, northeastern Utah, and northwestern Colorado, showing outcrops of Frontier Forma tion, the crest of the Moxa arch, and location of selected gas fields, boreholes, outcrop sections, and fossil localities . 3 2. Correlation chart of the lower Upper Cretaceous formations at selected localities in Wyoming and Colorado ... 4 3. Stratigraphic diagram of the Frontier Formation and Mowry Shale at boreholes and outcrop in northwestern Colorado, northeastern Utah, and southwestern Wyoming .................................... 10 4. Stratigraphic diagram of the Frontier Formation and Mowry Shale at boreholes and outcrop on the Moxa arch and the overthrust belt, southwestern Wyoming ...................................... 11 5. Stratigraphic diagram of the Frontier Formation and Mowry Shale at boreholes on the Moxa arch, southwestern Wyoming ............................................................ 12 6. Logs of cored and sampled strata in the Frontier Formation in borehole 1 on the Moxa arch, Wyoming ..... 14 7. Photomicrographs of thin sections of sandstone from boreholes 1, 2, and 3 in the Frontier Formation of southwestern Wyoming .......................................................... 17 8. Logs of cored and sampled strata in the Frontier Formation and Hilliard Shale in borehole 2 on the Moxa arch, Wyoming 20 9. Logs of cored and sampled strata in the Frontier Formation in borehole 3 on the Moxa arch, Wyoming ..... 22 10. Photomicrographs of sandstone from boreholes 3 and 11 in the Frontier Formation of southwestern Wyoming, taken with a scanning electron microscope ........................................... 25 11. Logs of cored and sampled strata in the Frontier Formation in borehole 8 on the Rock Springs uplift, Wyoming . 26 12. Logs of cored and sampled strata in the Frontier Formation in borehole 11 on the Moxa arch, Wyoming .... 27 TABLES TABLE 1. Location of selected boreholes and outcrop sections in the Green River Basin, Wyoming, Utah, and Colorado ... 9 2. Location, depth, lithology, and depositional environment of core samples from the Frontier Formation and the lower part of the Hilliard Shale in southwestern Wyoming .................................. 14 3. Grain sizes of core samples of sandstone from the Frontier Formation of southwestern Wyoming .......... 15 4. Description of thin sections of sandstone from core samples of the Frontier Formation of southwestern Wyoming . 16 5. Composition (in percent) of thin sections of sandstone from core samples of the Frontier Formation of southwestern Wyoming ..................*,.^.,,...,...............~.............. 18 6. Estimated mineral and organic-carbon content of core samples of sandstone from the Frontier Formation of southwestern Wyoming ................................. ^ ......................... 18 7. Content of principal oxides (in weight percent) in core samples of sandstone from the Frontier Formation of southwestern Wyoming ........................................................... 19 ni IV CONTENTS Page TABLE 8. Approximate content of selected oxides and elements in core samples of sandstone from the Frontier Formation of south western Wyoming, determined by emission spectrographic analysis .......................... 21 9. Estimated mineral content by X-ray diffraction of core samples of shale from the Frontier Formation and Hilliard Shale of southwestern Wyoming .................................................. 21 10. Organic composition, vitrinite reflectance, and hydrocarbon potential of core samples of shale from the Frontier Formation and Hilliard Shale of southwestern Wyoming ....................................... 22 11. Correlation coefficients for amounts of sand, silt, clay, organic carbon, and selected elements in eleven samples of sandstone of the Frontier Formation in southwestern Wyoming .................................. 28 THE MID-CRETACEOUS FRONTIER FORMATION NEAR THE MOXA ARCH, SOUTHWESTERN WYOMING By E. A. MEREWETHER, PAUL D. BLACKMON, and J. C. WEBB ABSTRACT organic matter. Most of the sampled shale units are thermally mature, in terms of oil generation, and a few probably are source rocks for The Frontier Formation in the Green River Basin of Wyoming, oil and gas. Utah, and Colorado, consists of sandstone, siltstone, and shale, and minor conglomerate, coal, and bentonite. These strata were deposited in several marine and nonmarine environments during early Late Cre INTRODUCTION taceous time. At north-trending outcrops along the eastern edge of the overthrust belt, the Frontier is of Cenomanian, Turonian, and The Frontier Formation in the southern part of the early Coniacian age, and commonly is about 610 m (2,000 ft) thick. Green River Basin (fig. 1), is composed largely of shale, The formation in that area conformably overlies the Lower Creta siltstone, and sandstone of marine and nonmarine ori ceous Aspen Shale and is divided into the following members, in as cending order: Chalk Creek, Coalville, Alien Hollow, Oyster Ridge gin. Molluscan fossils in the marine beds indicate that Sandstone, and Dry Hollow. In west-trending outcrops on the north the formation is of early Late Cretaceous age (Cenoma ern flank of the Uinta Mountains in Utah, the Frontier is middle nian, Turonian, and Coniacian) (fig. 2). The Frontier and late Turonian, and is about 60 m (200 ft) thick. These strata is about 60 m (200 ft) thick and disconformably overlies disconformably overlie the Lower Cretaceous Mowry Shale. In the Lower Cretaceous Mowry Shale at outcrops along boreholes on the Moxa arch, the upper part of the Frontier is of middle Turonian to early Coniacian age and unconformably overlies the northern flank of the Uinta Mountains in Utah, and the lower part of the formation, which is early Cenomanian at the is about 610 m (2,000 ft) thick and conformably overlies south end and probably Cenomanian to early Turonian at the north the Lower Cretaceous Aspen Shale at outcrops on the end. The Frontier on the arch thickens northward from less than east side of the overthrust belt in Wyoming (fig. 1). 100 m (328 ft) to more than 300 m (984 ft) and conformably overlies Sandstone units at the top of the Frontier are overlain the Mowry. The marine and nonmarine Frontier near the Uinta Mountains, comformably by the Upper Cretaceous Hilliard Shale marine and nonmarine beds in the upper part of the formation on in southwestern Wyoming and by the Upper Creta the Moxa arc ., and the largely nonmarine Dry Hollow Member at ceous Mancos Shale in northwestern Colorado (fig. 2). the top of the Frontier in the overthrust belt are similar in age. The main purposes of this study of the Frontier For Older strata in the formation, which are represented by the discon- mation are to synthesize relevant published and unpub formable basal contact of the Frontier near the Uinta Mountains, thicken northward along the Moxa arch and westward between the lished stratigraphic data, to provide new paleontologic arch and the overthrust belt. The large changes in thickness of the and petrographic information, and to present interpre Frontier in the Green River Basin were caused mainly by differential tations concerning the areal extent and depositional ori uplift and truncation of the lower part of the formation during the gin of some strata within the formation. Outcrops were early to middle Turonian and by the shoreward addition of progres examined and fossils were collected for this investiga sively younger sandstone units at the top of the formation during the late Turonian and early Coniacian. tion by W. A. Cobban and E. A. Merewether in 1974 The sandstone in cores of the Frontier, from boreholes on the Moxa and by E. A. Merewether in 1979. The Frontier in the arch and the northern plunge of the Rock Springs uplift, consists subsurface was studied in 1980 by using borehole logs of very fine grained and fine-grained

Load more