Rme-2040 Airborne Reconnaissance in The
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Y 3. At7 A CR RME-2040 GEOLOGY AND MINERALOGY AIRBORNE RECONNAISSANCE IN THE VALLEY OF FIRE-MUDDY MOUNTAINS REGION, NEVADA By Donald C. Barrett Neil Mallory September 1955 r'sl7 BfRAMY Salt Lake Branch Office, AEC b 5 Grand Junction Operations Office Salt Lake City, Utah IlItt WER~EFr OFC LDING~ ~QaaN t UNITED STATES ATOMIC ENERGY COMMISSION Technical Information Service metadc783669 LEGAL NOTICE This report was prepared as an account of Government sponsored work. Neither the United States, nor the Commission, nor any person acting on behalf of the Commission: A. Makes any warranty or representation, expressed or implied, with respect to the accu- racy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any information, apparatus, method, or process disclosed in this report. As used in the above, "person acting on behalf of the Commission" includes any em- ployee or contractor of the Commission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor. This report has been reproduced directly from the best available copy. Printed in USA. Price 50 cents. Available from the Office of Technical Services, Department of Commerce, Washing- ton 25, D. C. e S AEC Technical Information Service Extension Oak Ridge, Tennessee RME -2040 U. S. ATOMIC ENERGY COMMISSION GRAND JUNCTION OPERATIONS OFFICE DIVISION OF RAW MATERIALS SALT LAKE BRANCH OFFICE AIRBORNE RECONNAISSANCE IN THE VALLEY OF FIRE- MUDDY MOUNTAINS REGION, NEVADA by Donald C. Barrett and Neil Mallory September 1955 Salt Lake City, Utah 1 AIRBORNE RECONNAISSANCE IN THE VALLEY OF FIRE- MUDDY MOUNTAINS REGION, NEVADA CONTENTS Page Abstract ------------------------------------------------- 5 Introduction ----------------------------------------------- 5 Physiography----------------------------------------------5 Climate-------------------------------------------------7 Geology---------------------------------------------------7 Precambrian---------------------------------------------7 Paleozoic------------------------------------------------7 Mesozoic ----------------------------------------------- 8 Triassic and Jurassic ---------------------------------- 8 Cretaceous---------------------------------------------9 Cenozoic ------------------------------------------------ 10 Regional structure ---------------------------------------- 10 Uranium occurrences in sedimentary rocks ----------------- 10 Airborne procedures--------------------------------------11 Results -------------------------- ----------------------- 11 Ground investigations-------------------------------------- 13 Conclusions -----------------------------------------------14 References-----------------------------------------------14 3 AIRBORNE RECONNAISSANCE IN THE VALLEY OF FIRE- MUDDY MOUNTAINS REGION, NEVADA ILLUSTRATIONS Page Figure 1. Index map of Nevada ---------------------- 6 2. Airborne reconnaissance, Valley of Fire- Muddy Mountains, Clark County, Nevada ---------------------------------- 12 4 AIRBORNE RECONNAISSANCE IN THE VALLEY OF FIRE- MUDDY MOUNTAINS REGION, NEVADA ABSTRACT The Valley of Fire-Muddy Mountains region, located 20 to 30 miles northeast of Las Vegas, Nevada, was given approximately 25- percent airborne radiometric coverage during the fall of 1954. Rocks in the area range from Cambrian to Miocene in age. Uranium was known to occur at two sedimentary horizons at the time the airborne program began. One new uranium-bearing sedimentary horizon was discovered by the airborne reconnaissance. Of 15 anomalies detected, only .11 were posted as the remainder were claimed at the time of the survey. INTRODUCTION The Valley of Fire is about 30 miles northeast of Las Vegas, Nevada (fig. 1). An airborne radiometric survey of this area was begun October 15, 1954, and completed December 26, 1954. The area was given approximately 25-percent coverage. This area came to the attention of the Manhattan Project during World War II as a potential source of domestic uranium (Carper, 1946). At that time, the workings of the Perkins brothers' claim, the Carnotite No. 1, consisted of about 10 small open cuts and a shaft 20 feet deep. Carnotite was noted in five of the pits. In addition to the uranium indications on the Perkins brothers' claims, radioactive petrified logs had been found in the Valley of Fire State Park. These previously known uranium localities and a recent general reconnaissance of the area which verified the presence of extensive exposures of the Shinarump and Chinle formations in the area led Commission geologists to recommend the Valley of Fire region for an airborne radiometric survey. PHYSIOGRA PHY Maximum relief in the area is about 3, 800 feet. Muddy Peak rises to 5, 790 feet and is the highest point in the region. Several other peaks and ridges are over 4, 000 feet in elevation, whereas bottoms of intermontane valleys are locally less than 2, 000 feet above sea level. 5 N E V A D A I L I N C 0 L N C 0 U N T Y c Losa ego 11 r- C L A R -K N Y E Glendale 12 I CS nf U N T Y leatnon COU U NT AREA Scale5meie Los Vegas Boulder City Fig. 1 INDEX MAP OF NEVADA Showing location of Kingman AREA COVERED BY AIRBORNE RECONNAISANG CLARK COUNTY, NEVADA 0 5 0 20 30 4 50ee Scale miles 6 FLOWNo0200 U. S. Highway No. 91 forms the northern and western boundaries of the surveyed area. To the south and east, Lake Mead forms the boundary, thus the only practical access into the Muddy Peak region is from the north. Only two passable dirt roads lead southward from U. S. Highway No. 91 toward Lake Mead. The junction of one of these roads and Highway No. 91 is just northeast of Nellis Air Force Base. The other dirt road leaves U. S. Highway No. 91 at Crystal, about 30 miles northeast of Las Vegas, Nevada, and continues on to Overton, Nevada, which it enters from the south. This road passes north of Muddy Peak and through the southern end of the Valley of Fire. Several poor dirt roads lead directly to the Valley of Fire south of Glendale, one of which leaves the valley at Overton and is the access road to the Carnotite No. 1 claim. Climate Winters in the Muddy Mountains-Valley of Fire region are generally milder than in most of Nevada, although snow is common at higher ele- vations. In the town of Overton, the winters are very mild. During the summer, however, temperatures above 1100 F. are common. The average rainfall, which occurs as thunder showers mainly in July and August, is 5.01 inches. Natural vegetation is sparse and trees suitable for mine timber are not available in the Muddy Mountains. GEOLOGY Precambrian Although not exposed in the immediate area, Precambrian crystalline rocks occur to the east and south of the Valley of Fire and the Muddy Mountains. These basement rocks consist of various types of schist and gneiss which have been intruded by coarse-grained granitic rocks. Paleozoic In the Virgin Mountains east of Overton, about 400 feet of quartzite, sandstone, and shale overlie the Precambrian complex. Above these clastic sediments is 775 feet of dark-gray compact limestone which is 7 tentatively correlated with the Muav limestone of Middle Cambrian age of the Grand Canyon district (Longwell, 1928). Longwell (1928) believes that the limestone and dolomite, exposed at the base of an overthrust, are probably Cambrian and if so, are the oldest strata exposed in the Muddy Mountains. The oldest formation having recognizable fossils is the Muddy Peak limestone of Middle Devonian age which consists of dense, hard limestone and dolomite, siliceous in appearance, with alternating light and dark beds. The Mississippian section of the Muddy Mountains region is divided into two formations on the basis of fossils. The lower unit, the Rogers Spring limestone, consists mainly of 600 feet of gray crystalline lime- stone with some cherty zones. The Bluepoint limestone of Upper Mississippian age is lithologically similar to the lower unitexcept that it is finer grained and has a greater percentage of dark-gray carbonaceous beds. Above the Bluepoint limestone is the Callville limestone of Pennsylvanian age, which consists of 2, 000 feet or more of thin-bedded gray limestone interbedded with sandstone at the top. Longwell (1949) lists 2, 000 feet of unnamed red beds beneath the Kaibab limestone of Permian age, which had been correlated earlier with the underlying Supai formation of the Colorado Plateau. The Kaibab limestone is roughly divided into two limestone members separated by a 100-foot gypseous bed. Its thickness ranges from 600 to 800 feet. Mesozoic Triassic and Jurassic-- The Lower Triassic Moenkopi formation of Nevada may be divided into two units. The lower unit, which seems to be limited to the western extent of the formation, consists mainly of marine limestone and thin-bedded calcareous shale interbedded with two crossbedded sandstones. This unit grades upward into nonmarine gray, pink, and chocolate-colored shales containing abundant gypsum. The thickness is about 1, 500 feet. Overlying the Moenkopi is the Shinarump member of the Chinle formation of Upper(?) Triassic age. The conglomerate ranges from 10 to approximately 200