/ h / -) S D /O I f CAPITOL REEF <$il - imptecjiyid-rej) hs>c/c MINERS unuivrin TTTinnnnur n nir innr OCCURRENCES By J. Wallace Gwynn Assisted By -Bilt-Oalness 1967
CAPITOL REEF-MINERS MOUNTAIN BITUMINOUS SANDSTONE BTBDY SETTING The capitol Reef bituninous sandstone area occures mainly on the northern and northeastern portions of the area known as Miners Mountain. This is a dome structure of the Teasdale anticline, the axis of which parallels the Teasdale fault system. STRATIGRAPHY The rocks with which this study was involved were of the Permian and Triassic System, and were represented by the Coconino sandstone, KJ^bab limestone, and the Moenkopi formation, The Coconino sandstone is a fine grained, white to gray quartz sandstone in wedge-shaped lenses of large sweeping tangential crossbeds* It has an exposed thickness of about 800 feetin some of the deeper canyons in the area, and well data indicates a thickness of about 1,250 feet. The Coconino is exposed only in some of the more deeply cut canyons in the area. The Kiabab limestone is composed mainly of cherty limestone and dolomite with many interbedded sandstones and dense siltstones. It ranges from 250 to 350 feet in thickness and is exposed in the more deeply cut canyons as is the Coconino. In certain areas along the northern and eastern portion of Miners Mountain, certain sandstone horizons are lightly to heavily saturated with bituminous material, as well as the interior vugs of geodes from certain areas, mainly in Capitol Wash.
-2- The Moenkopl formation is composed mainly of red-brown siltstones, mudstones, and sandstones, with one prominant limestone unit (Sinbad member) near the center of the formation. This formation ranges in thickness from about 760 to 970 feet, and covers almost the entire surface of the study area except where drainage has cut into the underlying formations. There is some saturation in the Moinkopi, but this is confined to a few limestone beds near the center of the formation, : assumed to be the Sinbad member of the Moenkopl formation. STRUCTURE Miners Mountain, a dome structure, is a surface expression of the southern part of the Teasdale anticline. It is bounded on the southwest by the Teasdale fault system. Throughout the area there are numerous smaller faults which are located in the northern portion of the area, and in the Capitol Wash area. Structure contours taken on the top of 1 the Chinle formation indicate that there is a structural closure of about 800 to 1000 feet. DESCRIPTION OF THE B &rf There are several occurrences of bituminous material in the Miners Mountain area. They occur in the Moenkopl formation, the Kiabab formation, ai and in the geodes found in the Kiabab formation. The Sinbad limestone member of the Moenkopl is a yellowish-gray to yellowish-brown sequence of limestones, dolomites, and calcareous sand and siltstones. The saturation is found in a dense medium bedded limestone. Although the weathered surface gives little indication as to porosity or saturation, a fresh surfa3ce reveasl zones of light gray fine crystalline limestone, ofter fossiliferous, with many small pores and vugs which are often filled or stained with black petroliferous material. In most cases the rock carries a petroliferous odor upon breaking.
-3- This pore space constitutes a small percentage of the rock, perhaps as small as 1 to 5 percent. The thickness of the zone of saturation^has not been determined^ but the lateral extent seems to extend,1 in most cases, to wherever the Sinbad member is found in the area. There is also a thin zone of fairly rich saturation in the lower part of the upper Moinkopi. This is in a thin bed of calcareous sandy siltstone, its lateral extent, however, was perhaps 10 feet in length. a i " The Kiabab formation is found in the deeply eroded canyons of Miners Mountain. The saturation found in these rocks is in the canyons along the southeastern face of the mountain. It occures as finely divided specks of bituminous material disseminated throughout the sandstone* In some cases the saturation is very even throughout the rock, and in other cases it forms a mottled pattern. The saturation in I tiles Kiabab is rated as very weak to poor. The thickness of these stained sands varies from place to place. In the southern part of the area, stained rock may consist of only spotty areas a few feet in extent, but in Capitol Wash, there may be as much as a hundred feet of stained sandstone in the lower part of the formation. Mo saturation was found in the Kiabab outcrops on the western side of the mountain near Grover. The geodes found in the Kiabab may give the best explanation to the saturation pattern within the area. The geodes found on the western side of the mountain consist in general of solid chert nodules, and contain no bituminous material. As geodes are found farther east in the Kiabab exposures, they begin to contain calcite fillings which often give a weak to strong petroliferous smell upon breaking them open.
-4. Often those with a strong odor contain small specks of free bitumen in them and it is noted that the calcite would ofter be very dark and oily looking. Ceodes in the Capitol Wash area are almost all stained or filled with bituminous material. In some cases the bitumen occures as specks and chunks between the calcite crystals, but dois not coat the calcite crystals. In other cases, the calcite crystals are coated as if they had been painted. There are a few evidences of control associated with the deposition of bitumen in the area* It can be first noted that the saturation is located on the north and northeastern portions of the dome structure. The heaviest saturation being located near or around the Capitol Wash area is also the area of considerable localized east-west, north-east trending faulting. It was also noted in some Kiabab exposures that there has been some joint or fracture control of the saturation, the saturation being strong along one side of a fracture and absent of the other. Saturation is also controlled by bedding within a certain rock sequence, and by changes in lithology. FORMATION OF DEE9SJT With the exception of the Sinbad member of the Moenkopi, it could be assumed that the saturation in this area has migrated into the area by way of vertical fractures and faults frora depth, and has been trapped in the porous and permeable sandstones of the dome structure. This is evidenced by the presence of the local faulting, the accumulation in the northern part of the structure only, and the fracture control of the saturation in some of the massive homogeneous rocks.
The Sinbad member of the Moenkopi, on the other hand is a tight impermeable limestone except in the thin zones which are porous or filled with small vugs. It is in these immediate areas th8t the vugs, and sometimes the surrounding rock is saturated. Because of the tightness of the limestone, and the localized nature of the saturated zones, it could be assumed that this sparse saturation is an in situ condition, rather than a migration condition, Because of limited accessability to these areas of saturation, the small exposures, and the extreme weakness of the saturation, the Capitol Reed deposit is considered to be of no economic importance at the present time. The following are notes taken on eleven specific locations throughout the Miners Mountain area. /- Section 8, T30S. R6E. Geodes found in the Kaibab are solid with no visual indications or odor of petroliferous material. 7 NE Section 2, T30S, R6E. In this location both geodes and bituminous limestone were found in the stream bed at about the top of the Kaibab. The geodes give off a brief petroliferous odor upon breaking, but contain no visable staining with bitumen. The limestone is a gray massive rock which weathers smooth with no outward apparent porosity, but inside it, there are small vugs which are stained as well as stained fossil fragments. r- Section 15, T30S, R6E. Saturation is found near the top of the plateau as it breaks into the canyon. The saturation is found in two blocky zones of gray, porous limestone, probably in the Sinbad limestone. The bitumen occures as filling and staining in the limestone vugs.
-6. >?- NE Section 13, T30S, R6E, southern tributary of Capitol Wash, / rrj^^r) In the lower upper Moenkopi, the saturation found in a sandy limestone in in general weak with the exception of a short zjp4ie ^t,jrxcb_ aj^uxajej45.n about a fpot_thick. In the Sinbad limestone, saturation was found as coatings on the inside of small vugs. In the upper Kaibab, saturation is found in a massive limestone as flecks of bituminous material, Geodes are also found which contain considerable amounts of hard, dry bituminous material. In the lower Kaibab, much of the sandy portion of the formation contains small amounts of bituminous material, perhaps 100 feet in thickness or more. r -> - SE Section 30, T3QS, R7E, Pleasant Creek. Some saturation is found;/,' w^' in a porous Kaibab limestone, but only a few feet thick. The geodes in the area contain a few specks of bitumen, and some odor. 6 " SW Section 35, T29S, R6E. Staining is found in a white, calcareous,.,_,-_ Kaibab siltstone, and is controlled by fractures and jointing. Only a very few geodes are present which have a petroliferous odor, none stained. 7- NE SW Section 35, T29S, R6E. The entire thickness of Sinbad limestone seems to be filled with stained and filled vugs. Saturation seems to be stronger near the top of the limestone. Z~ SW SW Section 2, T30S, R6E. Here a siltstone unit of the Kaibab is found to contain very weak mottled saturation. 7 NW NW Section 11, T30S, R6E. Very weak staining is found in a thin lens, of Kaibab calcareous siltstone. The geodes are non-petroliferous. /O- SE NE Section 10, T30S, R6E. Saturation found in the blocky fossiliferous Sinbad member as staining in small vugs. //- Section 17, etc., T29S, R6E, Sulfur Creek. No saturation in either the Moenkope or the Kaibab was noted, nor were any significant geodes found in the area.
-7- EC0N0M1CS There has been no evident exploration work or exploitation of the tar sands in this area. The Pacific Western Oil Corp. drilled a well on the crest of the Teasdale anticline in 1949 to a depth of 4,932 feet, but only a small amount of staining wqs found in the Coconino sandstone* Other than this exploration work for oil in the immediate area, and a few other wells away from Miners Mountain, the only mining or prospecting has been for uranium, copper, building stone, and manganese. STATISTICS At the present there have been vo analyses made of any of the tars or bitumen from this area. It is proposed that 8 sulfur isotope analysis be made on the tars in order to extablish the age of the bitumen found in the area. BIBLIOGRAPHY Erifckson, R.L., A.T. Myers, and C.A. Horr. Association of Uranium and Other Metals With Crude Oil, Asphalt, and Petroliferous Rocks. Am. Assoc. Petrol. Geol. Bull., v. 38, 1954, pp 2200-2218. Smith, J.F., Jr., L.C. Huff, E.N. Hinrichs, and R.G. Luedke. Geology of the Capitol Reef A r ea, Wayne and Garfield Counties, Utah. U.S. Geol. Survey Prof. Paper 363, 1963, 102 pp. Surface and Shallow Oil-Impregnated Rocks and Shallow Oil Fields In the United States. Compiled By Ball Associates, Ltd. Monograph 12, Bureau of Mines, 1965