BLM LIBRARY 88026536 ©lores 'River Condon - \ahe.o^ne Cree,k Area GEOLOGICAL RESOURCE AREA (GRA) 8 FINAL REPORT PHASE 1: GEM (GEOLOGICAL, ENERGY and MINERALS) RESOURCE ASSESSMENT FOR REGION 4, COLORADO PLATEAU . CRAIO JUNCTION CO vo DENVER **°° SUBMITTED TO: U.S. DEPARTMENT OF THE INTERIOR BUREAU OF LAND MANAGEMENT DENVER SERVICE CENTER DENVER, COLORADO 80225 sHr MSME/WALLABY ENTERPRISES «-|» A JOINT VENTURE OF MOUNTAIN STATES MINERAL ENTERPRISES, INC. and WALLABY ENTERPRISES, INC. BLM Library , £& "c O COO * *s - £3* ■ -I o H Z 03 3S0M1N0W < o £5 o ♦ t\ !■*■ * ♦ 0) UJ o coz t-UJ OOC mUi3 Q.O > ooo I5 Q o o-^J 7fd o sl H s= V J- 063-OCO-OD z 00 z 5 <0 00 CD 0_ T- < 1 2> HI o (L O 3 o CD -J LL o UJ o o o q o CV4 in < O CO EXPLANATION Quaternary Qae (Approximately Qa 2 million years Qap before present Qc (mybp) to Qct present) Qcl Qat Cretaceous Kmvg (Approximately Kmvu 135-62 mybp) Kc Kb Kmv Kmvr Kmb Km Kmu Kmfe Kml Kd Kbc Kdb Kmdb Jurassic Jm (Approximately Jmb 195-135 mybp) Jms Js Jem Je Jsem Jse Jwe Alluvial and eolian deposits Alluvium deposits Pediment gravels Colluvial deposits Talus Landslide deposits Terrace gravels Mesaverde Group Upper part of Mesaverde Group Castlegate Sandstone Upper member of Blackhawk Formation Mesaverde Formation Mesaverde Formation, Rollins Sandstone Member Buck Tongue of the Mancos Shale Mancos Shale, undifferentiated Mancos Shale, upper shale Member Mancos Shale, Ferron Sandstone Member Mancos Shale, lower shale Member Dakota Sandstone Burro Canyon Formation Dakota Sandstone and Burro Canyon Formation Mancos Shale, Dakota Sandstone, and Burro Canyon Formation Morrison Formation Morrison Formation, Brushy Basin Shale Member Morrison Formation, Salt Wash Sandstone Member Summerville Formation Entrada Sandstone, Moab Sandstone Member Entrada Sandstone Summerville Formation and Moab Sandstone Member of Entrada Sandstone Summerville Formation and Entrada Sandstone Wanakah Formation and Entrada Sandstone Jurassic and J Tr sen Triassic J Tr n J Tr gc Triassic Trk (Approximately Trw 225-195 mybp) Tr kw Trd Tr wc Tr c Tr cu Tr cb Summerville Formation, Entrada Sandstone, and Navajo Sandstone Navajo Sandstone Glen Canyon Group - Navajo Sandstone, Kayenta Formation and Wingate Sandstone Kayenta Formation Wingate Sandstone Kayenta Formation and Wingate Sandstone Dolores Formation Wingate Sandstone and Chinle Formation Chinle Formation, undifferentiated Upper part of Chinle Formation Chinle Formation, Moss Back Member 1-4 Triassic continued Tr cm Chinle and Moenkopi Formations Tr m Moenkopi Formation Permian (Approximately 280-255 mybp) Pe Pea Pew Pco Pec Pcwo Pcac Cutler Cutler Cutler Cutler Culter Cutler Organ Cutler Formation, Formation, Formation, Formation, Formation, Formation, Rock Tongue Formation, undifferentiated arkose and arkosic conglomerate White Rim Sandstone Member Organ Rock Tongue Cedar Mesa Sandstone Member White Rim Sandstone Member and Transition zone, arkosic beds and Cedar Mesa Sandstone Member Permian & Pennsylvanian P Pr Rico Formation P Per Cutler and Rico Formations Pennsylvanian Ph (Approximately Phu 320-280 mybp) Php Hermosa Formation, undifferentiated Upper Member of Hermosa Formation Paradox Member of Hermosa Formation Precambrian (Approximately 3400-600 mybp) pC Precambrian rocks, undifferentiated 1-5 LEGEND CZD -0 OIL FIELD B C.'.D -G GAS F,ELD a y D C_J -Os OIL SHALE x ( ) -C COAL REGION >— • OIL WELL ^ ^ OIL ft GAS WELL . B ■$ GAS WELL ? \±r SHOW OF GAS 0 3 SHOW OF OIL ^ >4r show of oil a gas ^ • -c COAL deposit .„ O -C COAL OCCURRENCE A SHUT-IN WELL X 0 C02 OR He=HELIUM -RICH WELL A DRY WELL-ABANDONED C^3 MILL n PLANT O jO NATURAL GAS PROCESSING tj Ufj PLANT fflii REF,NERY 0 OIL Cb LIGNITE G GAS Cp PEAT Os OIL SHALE Ag SILVER 01 TAR SANDS Au GOLD Gi GILSONITE Cu COPPER C COAL CI CLAY 1-6 MINERAL OREBOD Y MINERAL DEPOSIT MINERAL OCCURRENCE PROSPECT ACCESSIBLE ADIT INACCESSIBLE ADIT VERTICAL SHAFT INCLINED SHAFT MINE TYPE UNKNOWN ACTIVE OPEN PIT, OR QUARRY INACTIVE OPEN PIT, OR QUARRY ACTIVE GRAVEL OR CLAY (CI) PIT INACTIVE GRAVEL OR CLAY (CI) PIT EXPLORATION HOLE WITH DATA AVAILABLE EXPLORATION HOLE WITHOUT DATA AVAILABLE UNPATENTED MINING CLAIM PATENTED MINING CLAIM MINERAL OR OIL a GAS LEASE Ds DIMENSION STONE Fc IRON Mn MANGANESE Pb LEAD U URANIUM V VANADIUM Zn ZINC SECTION II GEOLOGY PHYSIOGRAPHY The GRA boundary includes valley, canyon, and plateau areas along the course of the Dolores and San Miguel Rivers and in the Paradox Valley area. In the northeast portion of the GRA, an area essentially bounded by the Paradox Valley area on the southwest, are the drainages of the Dolores River, San Miguel River and Tabegauche Creek. This area is characterized by deep canyons that cut into the resistant Mesozoic rocks and leave behind a series of ridges, mesas and rough tributary drainages that feed into the main river systems. The ridges stand out as prominent topographic highs that rise almost 1,000 feet above the river beds. Such features as Martin Mesa, Atkinson Mesa, Atkinson Breaks, Spring Creek Mesa, Long Mesa, and Third Park are local flat-topped mesa, ridge and park areas where the topography gently slopes down to the west. The valleys of the major fluvial systems that cut through the area (Dolores River, San Miguel River and Tabeguache Creek) are narrow. The Dolores and San Miguel River drainages are alligned northwest-southeast and are parallel to the axes of the major fold structures that are found in the region, and the trend of the Uncompahgre Plateau. Within the GRA, the valley of the Dolores River is a narrow meandering canyon until it meets the San Miguel River just east of Martin Mesa. Upstream from the junction of the San Miguel with the Dolores River, to the point where the Dolores begins to cross Paradox Valley, there are a series of "goosenecks" in the river channel flanked by a spectacular canyon feature on the southeast side of Martin Mesa. The Paradox Valley cuts across the GRA in a northwest to southeast direction and is a prominent feature of the region. The valley floor is relatively flat with less than 500 feet of vertical relief. The valley is approximately 23 miles long, 2 to 4 miles wide and is crossed at right angles by the Dolores River. To the northwest and southwest of the Paradox Valley are a series of ridges and cliffs that define the valley. The vertical relief from the floor of the Paradox Valley to the tops of these ridge and cliff features is approximately 1,000 feet. The ridges and mesa tops southwest of Paradox Valley include resistent remnants of Mesozoic rocks and include such prominent topographic features as Skein Mesa, Mono- gram Mesa, Steer Mesa, Davis Mesa, Nyswonger Mesa, Buck Mesa and The Horn. These mesa areas are relatively flat, and have been moderately incised by the tributary drainage systems of the Dolores River. The most prominent physiographic feature of the area southwest of Paradox Valley is the Dolores River canyon. This major flu- vial feature is found along the course of the upper-middle drainages of the Dolores River and includes the La Sal Creek and Coyote Creek Drainages. Vertical relief in the canyon is approximately 1,000 to 1,200 feet. The Dolores has cut down into resistant beds of the Mesozoic section and carved a meandering canyon. The following descriptions address the physiographic composition of each of the individual WSA's within the Dolores River Canyon-Tabeguache Creek GRA. II-l DOLORES RIVER CANYON WSA (CO-030-290) Within the boundary of the WSA the Dolores River has cut a deep canyon into the resistant Mesozoic rock section. The vertical relief within the meandering canyon is approximately 1,000 to 1,200 feet. Lower benches of resistant bedrock, and a few rocky ridges are found within the WSA. These features rise 500 to 700 feet above the bottom of the canyon. Also included within the WSA are various tributary drainages that flow into the La Sal Creek-Coyote Wash-Dolores River drainage system. TABEGUACHE CREEK WSA (CO-030-300) Within this WSA is found a series of connected canyons that form the tributaries and main portion of Tabeguache Creek canyon. Within the canyon system, the verti- cal relief is approximately 800-1,000 feet. The adjacent ridges and mesa tops have been included within the WSA and are cut by the crooked tributary canyons of the Tabeguache Creek canyon system. Vertical relief from the bottom of the Tabeguache Creek drainage to the top of the mesas and ridges is approximately 1,000-1,200 feet . ROCK UNITS Within the Dolores River Canyon-Tabeguache Creek GRA is found a variety of rock units that represent a large part of Precambrian, Paleozoic, Mesozoic and Quaterna- ry time. The Precambrian section is represented by a complex of quartz-biotite and quartz- feldspar gneisses and schists that have been intruded by younger Precambrian felsic and mafic bodies (pegmatites-aplites-lamprophyres) . All of these units have been moderately deformed. The Precambrian sequence is relatively unstudied in this area and has not been extensively dated or correlated to other sections of Colorado. The exposures of these units are found in the northern and central parts of the GRA. The best described and exposed section of Precambrian Rocks is found in the nearby Unaweep Canyon area (Williams, 1964). In the Paradox Valley area, the Paleozoic section has been brought to the surface by tectonic and salt dome activity. The Pennsylvanian Hermosa Formation is exposed and consists of sandstone, black shale, gypsum, salt, fossiliferous limestone and thin bedded shale units (Cater, 1955). This portion of the sequence is thought to represent a period of rapidly fluctuating marine and terrestrial deposition. The basal portion of the Hermosa Formation is the well-known Paradox Member, which is thought to be a part of a salt dome system. This unit consists of a thick section of alternating gypsum, salt, anhydrite and marine limestone units with occasional units of gray sandstone and black shale (Williams, 1964). This unit has associated gas deposits in the south-central portion of the GRA, and is a potential source of brines, sulfur, gypsum, salt and anydrite. Also in the Paradox Valley are expo- sures of fluvial arkoses and conglomerates of the Permian Cutler Formation. This unit is thought to represent a period of fluvial deposition in shallow basins adja- cent to the eroding Precambrian highlands (Carter et al, 1965; Williams, 1964). II-2 The overlying Mesozoic section consists of Triassic mudstones, sandstones, silt- stones and conglomerates of the Chinle, Wingate, and Kayenta Formations. These units are thought to be of terrestrial origin and were probably deposited in a fluvial or eolian environment adjacent to a series of shallow inland lacustrine basins. Thin limestone units in the Kayenta Formation are thought to represent periods of fresh water lacustrine deposition (Carter et al, 1965; Williams, 1964). Directly underlying this sequence and conformably overlying the Paleozoic strati- graphy is the Triassic Moenkopi Formation. This unit is separated from the rest of the Triassic stratigraphy by a regional unconformity. It consists of sandstone and mudstone members with local beds of arkosic conglomerate and gypsum (Carter et al, 1965 ; Williams, 1964). The Moenkopi appears to have been deposited in a shallow water fluvial or lacustrine setting that was subjected to periodic dessication. The overlying Moss Back Member of the Chinle Formation is known to contain abundant plant remains in other parts of Colorado and Utah, and is the uranium-vanadium bearing host rock in the Lisbon Valley area of eastern Utah. An equivalent to this unit may exist in the GRA, and, thus, have potential for the occurrence of uranium- vanadium deposits (Carter et al, 1965; Williams, 1964). Directly overlying the Triassic sequence and sometimes mapped with it is the Navajo Sandstone. This Triassic- Jurassic eolian terrestrial sandstone is found in only a few areas in the southwestern part of the GRA, and is thought to represent a period of inland sand dune deposition or a desert environment (Carter et al, 1965). The Jurassic over- lying sequence begins with Entrada Sandstone and the overlying Summerville Forma- tion. These units are thought to represent a period of terrestrial fluvial and eolian deposition in small, restricted basins (Carter et al, 1965). They outcrop throughout the GRA and have been known to contain tabular uranium-vanadium deposits in the nearby Slick Rock area (Williams, 1964). The Morrison Formation completes the upper Jurassic sequence of terrestrial fluvial and lacustrine sediments. This unit is well known for its uranium-vanadium depos- its in this and other areas of Colorado. This unit is known to contain numerous uranium-vanadium deposits within the GRA. The fluvial and lacustrine shale, mud- stone, sandstone, and limestone units of the Morrison Formation are thought to have been deposited in fluvial environments adjacent to shallow, fresh-water lakes in shallow, inland, terrestrial basins (Carter et al, 1965). The major uranium-vanadium deposits of the region have been found in the sandstones units of the Salt Wash Sandstone Member. This unit outcrops throughout the cen- tral, southern, and northern portions of the GRA and has major potential for "roll- front" sandstone hosted uranium-vanadium mineralization. "Roll-front" mineraliza- tion consists of elongate concretionary structures encompassed by rich vein-like concentrations of uranium-vanadium-bearing clay minerals. The upper member (Brushy Basin Shale Member) of the Morrison is also known to contain uranium- vanadium deposits. This unit contains beds of bentonitic mudstone, fluvial sand- stone and conglomerate lenses. The uranium-vanadium mineralization of the Brushy Basin Shale Member appears to be confined to the fluvial environment with the best concentrations of mineralization being found in conglomerate lenses, and in associ- ation with organic "trash." Some of this "trash" is fossil plant and saurian mate- rial (Carter et al, 1965; Williams, 1964); and, thus, has been recognized as a paleontological resource for Jurassic vertebrates. II-3 The Lower Cretaceous section is represented in the GRA by the Burro Canyon Forma- tion. This unit consists of a series of mudstone, siltstone, and shale units that are interbedded with fluvial sandstone and conglomerate units, and a few, thin beds of impure limestone (Williams, 1964). The fluvial character of these clastic units suggests that the environment of deposition was one of sedimentation along meandering river systems with adjacent, shallow terrestrial lakes. The area may have also been undergoing uplift during this period, as there is an unconformity at the top of Burro Canyon which represents a period of nondeposition and erosion (Carter et al, 1965). As a result, the Upper Cretaceous Dakota Sandstone unconfor- mably overlies the Burro Canyon Formation. This unit consists of quartzitic sand- tone, conglomeratic sandstone, carbonaceous non-marine shale and a coarse, basal conglomerate (Williams, 1964). The shale units of the Dakota are well known for fossil plant remains, and locally contain thin seams of coal (Gentry, Personal Communication, 1982). This unit has some potential as a source of coal, but it outcrops in only a few areas within the GRA. It is mainly found on mesa tops in the central and western portion of the GRA. The basal part of the Upper Cretaceous Mancos Shale outcrops in the Nucla syncline and consists of a series of black fissile shale units with interbedded sandstone beds (Williams, 1964). The rest of the Mesozoic and all of the Cenezoic section does not outcrop within the GRA. Unconformably overlying the exposed Precambrian, Paleozoic, and Mesozoic strati- graphy is a series of Quaternary fluvial, eolian, colluvial, and alluvial deposits- that represent periods of recent erosion and fluvial deposition. The following descriptions address the rock units of each of the individual WSA's within the Dolores River Canyon-Tabeguache Creek GRA. DOLORES RIVER CANYON WSA (CO-030-290) Within the boundaries of the WSA, the Precambrian rocks are not exposed. According to drilling information, the Paleozoic Hermosa Formation underlies most of the WSA (Heylmun, Personal Communication, 1982; Shoemaker, 1955; Cater, 1955; Cater, 1970). Pre-Pennsylvanian Paleozoic Formations are also thought to exist at depth under the WSA and are thought to represent a thick sequence of marine sedimentation (Baars et al, 1981). The Precambrian probably does exist at great depth (10,000 feet or more) and probably consists of older Precambrian gneisses, schists and fel- sic intrusives that have been deformed and intruded by a later, granitic intrusive felsic-mafic complex (Williams, 1964; Baars et al, 1981). Northwest striking fault systems that bound the Paradox Valley on the southwest side separate outcrops of the Pennsylvanian Hermosa Formation in the Paradox Valley from the Triassic section that crops out(Cater, 1955). The oldest Triassic unit that crops out within the WSA is the Triassic Chinle Formation, a series of terres- trial sandstone, shale, siltstone, limestone-pebble conglomerate and quartz pebble conglomerate units. The lower clastic units may be equivalent to the uranium- vanadium bearing units of the Lisbon Valley area of Utah. Directly overlying these units are the massive, thick bedded eolian sandstone units of the Wingate Sand- stone. Within the WSA both the Chinle and the Wingate are known to host copper- silver deposits (Cliff Dweller and Cashin Mines) that may be partially syngenetic in origin ( Gilmour, Personal Communication, 1982; Williams, 1964; Shoemaker, 1956). Similar deposits have been found in other areas of Colorado in association with fault and shear systems that cut the Chinle-Wingate strata. II-4 In all cases, mineralization occurred at specific horizons in the units, and was only brought up to economic grade by remobilization of the mineral material along faults and within shear zones (Gilmour, Personal Communication, 1982; Schwochow, 1978; Vanderwilt, 1947). Directly overlying the Wingate Sandstone is the Triassic Kayenta Formation which is characterized within the WSA as a series of fluvial sandstone, shale, and siltstone units with thin beds of limestone and shale-pellet conglomerate (Williams, 1964). Throughout the WSA, the Triassic- Jurassic Navajo Sandstone Formation crops out and lies directly on the Kayenta. This well-crossbedded eolian sandstone unit is thought to represent a period of terrestrial arid deposition in an inland basin. (Carter, 1958; Cater, 1955; Shoemaker, 1955; Cater, 1954). The Jurassic section that has been included within the WSA include outcrops of the Entrada Sandstone, Summerville and Morrison Formations. These units are exposed in only a few areas of the WSA, and are characterized as a series of sandstone, silt- stone, shale, mudstone, fluvial mudstone, bentonitic mudstone and lacustrine shale units with local conglomerate and limestone beds. All of these units are known to contain uranium-vanadium mineralization in areas surrounding the WSA, and in other portions of the Uravan Uranium-Vanadium Belt (Schwochow, 1978; Vanderwilt, 1947). Quaternary fluvial deposits and alluvial material are found lying directly upon the exposed Triassic and Jurassic stratigraphic units in the canyon bottoms. TABEGUACHE CREEK WSA (CO-030-300) Within the boundaries of the WSA the Triassic Chinle, Wingate and Kayenta Forma- tions, in ascending order, crop out in the bottom of Tabeguache Creek canyon. These units represent a section of mudstones, shales, sandstones and siltstones that are thought to be of terrestrial origin. Within the WSA, there is no reported copper- silver or uranium-vanadium mineralization, as is often found in other areas of Colorado and Utah. The Triassic- Jurassic Navajo Sandstone is not found in this area and probably was never deposited this far east (Carter et al , 1958). Jurassic Units that have been mapped in the area include, in descending order, the Brushy Basin Member of the Morrison Formation, and the Summerville Formation and Entrada Sandstone. These units are characterized within the WSA as a series of sandstone, shale, siltstone and mudstone units with conglomerate and limestone members (Williams, 1964). While these units are the major producers of uranium and vanadium in other, adjacent areas of the Uravan Uranium- Vanadium Belt, they are not known to contain such mineralization within the boundaries of the Tabeguache WSA (Williams, 1964a). Cretaceous units that crop out on mesa tops include the Burro Canyon Formation and the Dakota Sandstone. These units are characterized as a series of shale, sand- stone, siltstone, mudstone, and conglomerate units with beds of nonmarine carbonaceous shale and coal in the Dakota. The coal beds within the Dakota are considered an energy resource by the United States Geological Survey and are being mined commerciably in the nearby Nucla-Naturita Coal Field, found within the GRA. (USGS & CGS, 1978; Speltz, 1978; Gentry, Personal Communication, 1982). Quaternary fluvial material directly overlies the exposed Triassic and Jurassic rocks throughout most of the Tabeguache Creek drainage. II-5 STRUCTURAL GEOLOGY AND TECTONICS Tectonic features found within the GRA include high angle faults, shear zones and joint systems that strike northwest and northeast and parallel major regional structural features (Shoemaker, 1951). In the southern part of the GRA, in the Paradox 7.5 minute quadrangle, is a series of north-northeast and northeast striking faults and shear zones that have associated copper-silver mineralization (Withington, 1955). One of the major regional structural systems that cuts through the area is the Castle Valley-Paradox Valley Anticlinal trend. Part of this major fold system is found in the Paradox Valley area and consists of a belt of folded and faulted Paleozoic and Mesozoic units. Numerous northwest striking, high angle, normal and reverse faults, found along the margins of this fold feature, are associated with the trace of the axial plane of this fold system (Williams, 1964; Withington, 1955; Mattox, 1968). On the northeastern flank of this anticlinal trend is a series of paralleling structures that mark a major rift system that has been active since the Precambrian and defines the northeast edge of the Paradox Basin, a regional structural feature (Baars et al, 1981). The northwest and northeast striking structures of the Paradox Valley have localized oil and gas deposits within the area, and have acted as structural con- trols for the salt dome deposits of salt, anhydrite, gypsum, and metal-rich brines (Baars et al, 1981; Heylmun, Personal Communication; Mattox, 1968; Shoemaker, 1951; Eyde, Personal Communication, 1982). In the northeast portion of the GRA are found a series of northwest and west-north- west striking high angle faults that expose the Precambrian and Lower Mesozoic units that rest on the Precambrian strata of the Uncompahgre Uplift. The Uncompahgre Uplift is a highland area in western Colorado that rises 3,000 to 5,000 feet higher than the surrounding terrain (Baars et al , 1981). These structures have a similar orientation to others that have localized copper-silver-gold- amythyst mineralization in other areas of western Colorado (Unaweep Canyon & Dominguez Canyon areas). (Schwochow, 1978; Vanderwilt, 1947). Within the GRA are a number of major unconformities that have been identified by drilling and stratigraphic studies. The stratigraphy of the southwestern portion of the GRA has been extensively studied by major oil companies and the Federal government (Williams, 1964; Baars et al, 1981; Heylmun, Personal Communication, 1982). In addition, the stratigraphy of the central area of the GRA has also been thoroughly investigated due to the potential for occurrence of uranium-vanadium in the Mesozoic rocks in the area. Other parts of the GRA have been mapped by the United States Geological Survey and various students. From the work that has been done, it appears that there is a major unconformity at the base of the Paleozoic section. The stratigraphy in the Paradox Valley area tends to indicate that there is some break in sedimentation in the lower Paleozoic time and that the Pennsylvan- ian underlying the Middle Paleozoic units may rest directly upon the Precambrian basement complex (Baars et al, 1981). In areas to the northeast of the Paradox Valley and adjacent to the Paradox structural basin the Permian Cutler Formation lies directly upon the Precambrian basement. II-6 In the extreme northeast portion of the GRA, the Triassic Chinle Formation, togeth- er with its overlying Wingate Sandstone, lies directly and unconformably upon the Precambrian units (Williams, 1964). This situation probably describes a time- transgressive unconformity that existed from lower Paleozoic to lower Mesozoic time. During this period, the mass of the Uncompahgre Uplift was shedding sedi- ments into a series of deep basins that made up the Paradox structural basin fea- ture (Baars et al, 1981). The following descriptions address the structural and tectonic characteristics of each of the individual WSA's within the Dolores River Canyon-Tabeguache Creek GRA. DOLORES RIVER CANYON WSA (CO-030-290) Structural features within the Dolores River Canyon WSA include northwest striking faults that parallel the axes of the various regional fold structures; north-northeast and northeast striking faults and shear zones that have associated copper-silver mineralization, and northwest striking fold structures that were caused by periods of Paleozoic and Tertiary tectonism (Withington, 1955; Baars et al, 1981). High-angle joint systems parallel most of the major faults and control the drainage pattern of the Dolores River within the WSA. Northeast trending canyons are intersected by northwest-striking drainages. The result is a meandering river system characterized by canyons and cliffs. Within the WSA are a number of northwest striking faults that have acted as structural traps for oil and gas deposits in other parts of the Paradox Valley (T46N, R 17-18W). The north-northeast and northeast striking faults that have localized copper-silver mineralization at the Cliff Dweller and Cashin Mines in the northern part of the WSA are thought to be earlier features that were rejuvenated in Tertiary time (Withington, 1955). There are no known unconformities exposed within the WSA. A possible unconformity at the base of the Paleozoic section may exist at great depth under the WSA but has not been confirmed. The Jurassic Morrison Formation is the youngest Mesozoic unit that crops out within the WSA. Quaternary alluvial material has been deposited along the course of the Dolores River and directly overlies Triassic and Jurassic units (Withington, 1955). TABEGUACHE CREEK WSA (CO-030-300) Significant structural features within this WSA include high-angle northeast- striking faults, shear zones, and joint systems that cut across the dominant northwesterly striking structural fabric of the area. Northwest striking faults and joint systems cut through the northeastern portion of the WSA paralleling the axial plane of the regional fold systems and the trend of the Uncompahgre Uplift. Tabeguache Creek canyon trends generally east-west and is primarily controlled by a series of intersecting northwest and northeast striking joint systems. Underlying the WSA, the Mesozoic section is thought to directly and unconformably overlie the Precambrian basement complex. This relationship is not exposed, but exists 2 miles northeast of the WSA. If such an unconformity does indeed exist, it would indicate that the area within the WSA was undergoing uplift and erosion in Paleozoic and part of Mesozoic times. II-7 The WSA is located on the east flank of the Paradox Basin in an area thought to be underlain by the Uncompahgre Uplift Precambrian complex. Recent seismic work and stratigraphic studies suggest that the area is underlain by a major thrust system at depth and that portions of the Precambrian section have been thrust southwestward, over units of the Paleozoic, that are known to contain oil and gas deposits (Heylmun, Personal Communication, 1982). This relationship has not been confirmed as of this date by drilling. Within the WSA, there may exist an unconformity at the base of the Cretaceous Dakota Sandstone that represents a period of nondeposition (Withington, 1955). Directly overlying the Mesozoic section are a series of Quaternary deposits which represent periods of alluvial and eolian deposition on existing bedrock surfaces and along fluvial systems. PALEONTOLOGY Paleontological resources of the GRA have been extensively studied by both private industry and the Federal government in conjunction with oil, gas, and mineral exploration and stratigraphic studies (Shawe et al, 1968; Craig et al, 1955; Baars et al, 1981; Wengerd et al, 1958; NPS File Data, 1982). Most of these were detailed studies of various units in the Mesozoic and Paleozoic stratigraphy and dealt only superficially with the fossil occurrences and localities. From the studies, it is known that fossilif erous units do occur in various members of the Pennsylvanian Hermosa Formation (Withington, 1955). This is a normally thick sequence that has abundant marine fossils (Withington, 1955). The Salt Wash member of the Jurassic Morrison Formation is also known to contain fossil wood, carbonaceous material, plant remains and occasional reptile remains (Withington, 1955). Plant remains have been reported associated with impure coal seams in the Cretaceous Dakota Sandstone (Withington, 1955). The Triassic Moenkopi, Chinle and Wingate Formations that crop out throughout the GRA are also known to contain fossil reptile, amphibian and wood material in other areas of Colorado, Utah and Arizona (NPS File Data, 1982), and may contain such material within the GRA. The following description address the paleontological resources of each of the individual WSA's within the Dolores River Canyon-Tabeguache Creek GRA. DOLORES RIVER CANYON (CO-030-290) Within the WSA, the Chinle Formation and Wingate Sandstone may contain fossil reptile, amphibian, and wood remains as are found in other, surrounding areas of western Colorado and Utah. The Triassic- Jurassic Navajo Sandstone is known to contain saurian tracks in other areas of Colorado and Arizona, and may also in areas of the WSA. These resources are considered of scientific interest and it is recommended that a thorough study be made prior to any evaluation of the potential for paleontological resources within the WSA (NPS File Data, 1982; Withington, 1955). Isolated outcrops of the Jurassic Morrison Formation occur within the boundary of the WSA and probably contain fossil plant and animal material (Withington, 1955; Gilmour, Personal Communication, 1982). II-8 TABEGUACHE CREEK WSA (CO-030-300) The WSA contains no known or reported localities of fossil material. In other areas of Colorado, the Upper Cretaceous Dakota Sandstone is known to contain fossil plant material (Shawe et al, 1968). Isolated outcrops of the Jurassic Morrison Formation occur within the boundary of the WSA and may contain fossil plant mate- rial (Craig et al, 1955). HISTORICAL GEOLOGY During Middle Precambrian time the entire GRA was receiving sediments from both cratonic and island arc sources (Gilmour, Personal Communication, 1982). It appears that this was a time of persistent volcanism and tectonic activity. Marine deposition of eugeosynclinal sediments was interrupted by the ebb and flow of cratonic and island arc volcanism, and a period of extreme deformation was caused by plate collissions and regional uplifting. These older Precambrian units were metamorphased, deformed, and intruded by a series of younger Precambrian mafic and felsic bodies. In this study area, the Precambrian rocks are thought to be mainly intrusive masses of granite that have partially absorbed the earlier gneiss and schist material. Some of these intrusives contained anomalous amounts of metals, and have mineral deposits associated with them in other parts of Colorado and western United States (Vanderwilt, 1947). Other base and precious metal deposit types called exhalative deposits, are commonly found in Precambrian lithologies. These exahalative depos- its, found in association with marine basins and rhyolitic volcanic systems, are commonly associated with the older Precambrian lithologies. Younger Precambrian or Paleozoic intrusives have intruded the older, highly metamorphosed and deformed complex of granite, gneiss, schist, pegmatite, aplite and lamprophyre lithologies. This later granitic unit appears to have altered the units it intruded, and may be partially responsible for vein deposits of base and precious metals, beryl, and fluorspar that are found in adjacent areas to the east of the GRA. The Precambrian sequence is relatively unstudied in this area and has only been partially correlated with other areas of Colorado (Cater, 1955). In parts of northwestern Colorado, the younger Precambrian is partially preserved, and consists of a thick section of clastic sediments. These lithologies represent a period of clastic deposition in a marine environment. The only area within the boundaries of the GRA where such an environment may have existed is along southern and western boundaries of the GRA, west of the Uncompahgre Uplift. From the seismic and drilling information that is currently available, it appears that the younger Precambrian units of this area were deposited in a deep, marine basin that persisted through Paleozoic time (Baars et al, 1981). Approximately 1,700 million years before present during Precambrian, there was a period of uplift and rift formation that set the stage for all subsequent events in southwestern Colorado (Baars et al, 1981). These events, which caused the forma- tion of a large and deep rift basin adjacent to the Uncompahgre Uplift, were caused by deep north-south compressional crustal forces (Baars et al, 1981). With the formation of this deep basin, all sedimentation was restricted to the basinal area, and the exposed, deformed and intruded Precambrian basement complex ringing the basin was subjected to erosion. Within the GRA, it is thought that this deposition continued through Permian time. Though the only Paleozoic rocks that outcrop in the GRA are the Pennsylvanian and Permian lithologies, it is very probably that II-9 the full Paleozoic section exists under the western portion of the GRA (Baars et al, 1978; Shoemaker, 1951). This period of early and middle Paleozoic deposition was characterized by the formation of a series of shallow basins along the deep rift valley. It is thought that these basins were progressively filled by Cambrian, Devonian, and Mississippian sediments (Baars et al, 1981). These units were then downfaulted into the rift zone during periods of tectonic activity. These periods of vertical movement were precursors to the extreme orogenic episodes that occurred in the beginning of Middle Pennsylvanian time, when Precambrian units were uplifted rapidly and formed highlands that shed between 15,000 and 20,000 feet of clastic sediments (Baars et al, 1981). These sediments filled the deeper parts of the adjacent structural trough. This highland continued to exist throughout Pennsylvanian and Permian time, and was partially inundated by the clastic sequences of the Permian Cutler Formation. During most of the Paleozoic, the deep rift basins teamed with plant and animal life. Reef communities grew on shallow marine bedrock highs in association with algal bioherms. Northwest striking faults and shear systems were active within the basins, and caused much in the way of up and down movement of the basement blocks that formed the floor of these basins. Certain basins along the rift zone were isolated by tectonic activity and became stagnant, inland, lacustrine bodies that were so filled with terrestrial sediments that they were unable to support life and became depositories of thick marine evaporite sequences (Baars et al, 1981). As a result of these evaporites being in isolated basins, salt domes, anticlines, and diapirs formed. These features were caused when the plastic evaporitic lithologies began to flow in response to tectonic stresses. The result of this movement was to form structures that displaced up to 14,000 feet of strata and created a series of diapirs and tight folds (Shoemaker, 1951; Baars et al, 1981). Faults that formed along the margins and axial planes of these flowage features were active in Pennsylvanian and Permian time, and added to the structural complexity of the pre-existing basins. In the Mesozoic, the area was the site of fluvial and lacustrine deposition in a terrestrial environment. The Triassic Moenkopi Formation overlies the Paleozoic units in portions of the GRA, and is thought to represent an era when shallow, fresh-water lakes in enclosed basins were subjected to periods of dessication and shallow-water, clastic deposition. The Moenkopi Formation is known for its saurian tracks and vertebrate fossils in other areas of western Colorado. Thus, it is reasonable to assume that amphibian and reptile life may have existed within the GRA during this period (NPS File Data, 1982). The Chinle, Wingate, and Kayenta Formations of the Glen Canyon Group represent a time of Triassic sedimentation in a near-shore environment with episodes of eolian deposition of well cross-bedded beach and dune sand deposits. Certain fluvial and shallow water lacustrine deposits have also been identified in this sequence of sandstone, shale, siltstone, mudstone, limestone, and conglomerate. It appears that the Triassic units were deposited along the margins of great open seas and restricted inland basins that had existed since Paleozoic time. As the shorelines of these seas moved back and forth in response to orogenic episodes and basin filling, the localized environments in the GRA changed from marine to terrestrial. During this time, shallow-water and near-shore swamps were formed. In other areas of Colorado, these Upper Triassic near-shore sediments are the host for copper-silver "redbed" deposits that were deposited in areas of rapidly changing Eh-pH conditions in the aqueous solutions within the rock strata. The presence of these deposits within 11-10 the GRA and in other, widely dispersed areas of western Colorado is ample evidence that conditions favorable for these types of environments did, indeed, exist in the Triassic Period. The Navajo Sandstone outcrops in the southwestern portion of the GRA and is thought to represent a period of inland sand dune accumulation in a terrestrial desert environment (Carter et al, 1965). This Triassic- Jurassic time unit thins to the east and probably was not deposited on top of the Uncompahgre Uplift (Baars et al, 1981). The unconformity between the Navajo Sandstone and the overlying Jurassic Entrada Formation is probably a local feature that represents a period of non-deposition (Shawe, 1968). The Navajo is known to exist only in selected, desert environments or basins, and may have never been deposited in some areas west of the Uncompahgre Uplift. The Jurassic Entrada, however, is thought to have been deposited during a period of terrestrial fluvial and eolian deposition in small, restricted basins that eventually coalesced and buried the majority of the Uncompahgre Uplift features (Carter et al, 1965). The Navajo-Entrada unconformity may then represent a period when the last remnants of the Uncompahgre topographic high were being eroded into flanking shallow Jurassic basins. The Jurassic Summerville and overlying Morrison Formations were being deposited in near-shore lagoonal environments, or shallow water marine and fluvial systems. Some fresh-water lacustrine and fresh water fluvial deposits have also been identified from these rocks. As in the earlier Triassic section, mineral deposits are commonly found associated with limey sandstones, shales, and siltstones that were deposited in shallow, neritic basins that had fluvial channels meandering through them. Uranium-vanadium and minor copper-silver mineralization occurs in these units as roll-front and organically precipitated "stream-channel" deposits (Withington, 1955). "Stream-channel" deposits occur where uranium-vanadium waters encountered structural traps and/or clastic organic accumulations and deposited minerals in a reducing environment. Such mineral deposits are very important economically as they contain high grade uranium-vanadium ores, and are known to occur throughout the GRA. These deposits are thought to have been emplaced in an environment similar to that of the present lower Mississippi Basin. Fossil-plant material from this period is indicative of a tropical environment that was adjacent to an active fluvial or lacustrine system. During Lower Cretaceous time, much of western Colorado was the site of the shallow water deposition in a lagoonal or swamp environment. The Lower Cretaceous Burro Canyon Formation appears to have been deposited in a series of meandering river systems with adjacent terrestrial lakes. The terrestrial, clastic nature of this formation is thought to be characteristic of a beach or littoral environment (Young, 1955). The Upper Cretaceous Dakota Sandstone unconformably overlies the Burro Canyon Formation, and was probably deposited on an irregular upper surface of Burro Canyon rather than a true erosion surface (Carter et al, 1965). Portions of the Dakota are found as channel fillings in the upper Burro Canyon paleosurface . From fossil evidence, it appears that the lower sections of the Dakota were deposited in shallow basins or stream channels and having the source of the material being eroding masses of Pennsylvanian and Permian rocks that were then exposed to the west (Carter et al, 1965). The carbonaceous shales of the Dakota are known to contain abundant plant remains, and were probably deposited in a near-shore swamp or lacustrine environment. Thin coal beds are known to exist within the Dakota in certain areas and these may have economic potential. 11-11 During the Tertiary, the thick. Pennsylvanian salt sequences and the overlying Paleozoic and Mesozoic clastic, terrestrial sediments were folded and uplifted along the flanks of the Uncorapahgre Plateau. The evaporitic sequences actually were deformed into topographic highs within the areas of the sedimentary basins (i.e., Sinbad Valley, Castle Valley and Paradox Valley), which were subjected to rapid erosion (Cater, 1955). During this time, at least two periods of major uplift along the Uncompahgre Plateau have been identified. These orogenic episodes caused highlands to be formed which may have had topographic relief of several thousands of feet equivalent to the present day Front Range near Denver, Colorado. This area shed sediments into the ancestral Colorado River drainage Basin and major Uinta and Wasatch basins of northwestern Colorado. Within the GRA, the majority of the Upper Cretaceous and Tertiary section is missing. The Upper Cretaceous Mancos Formation was probably deposited over much of the GRA and is preserved along the west of the Uncompahgre Plateau. The Upper Cretaceous and Lower Tertiary was a time of mountain building, base and precious metal mineralization and sedimentation in shallow, broad basins (Carpenter, Personal Communication, 1982). Within the GRA, the dominant processes evolving the region were tectonic and orogenic rather than sedimentary (Carter, 1955; Baars et al, 1981). The unconformably , overlying the older rocks, Quaternary fluvial, eolian, colluvial and alluvial deposits represent periods of recent erosion and fluvial deposition. These units contain fragments of the Precambrian, Paleozoic, and Mesozoic strata that were exposed and have been eroded since the Tertiary. The following addresses the historical geology of each of the WSA's in the Dolores River Canyon - Tabeguache Creek GRA. DOLORES RIVER CANYON WSA (CO-020-290) The basal Precambrian section is thought to consist of quartz-feldspar, and quartz- biotite gneisses containing schists that have been intruded by older and younger Precambrian granites, aplites, pegmatites, and lamprophyres . This group of units may exist at depth but is not exposed in the WSA. The units are probably moder- ately deformed. Base and precious metal deposits associated with these lithologies have been found in the Unaweep Canyon area 24 miles to the north (Schwochow, 1981). The Paleozoic section is found outcropping within the WSA in the Little Gypsum Valley area. On the eastern side of the WSA, a fault system exists between Mesozoic section and the adjacent Pennsylvanian Hermosa Formation. This probably represents a period during which most of the Paradox Valley was undergoing subsidence and uplift. The Hermosa and Permian Cutler Formations are thought to represent a period of clastic and chemical deposition on the flanks of the Uncompahgre Uplift. These units are thought to exist at depth under the WSA and are known oil-and gas-bearing units, southeast of the WSA. The mesozoic rocks exposed within the WSA are thought to represent periods of fluvial and lacustrine deposition in a terrestrial environment. The lacustrine deposits of the Triassic Moenkopi Formation are thought to exist under the WSA and may contain thin gypsum and anhydrite beds which have possible economic potential. In other areas of Utah and Colorado, the Chinle Formation is the host for major uranium/ vanadium deposits. Within the GRA, this unit and the overlying Wingate Sandstone are known to contain copper-silver deposits that have been mined in the past. The Chinle, Wingate, and Kayenta Formations of the Glen Canyon Group are 11-12 thought to represent a time of Triassic sedimentation in a near-shore environment with episodes of eolian deposition of cross-bedded sandstones. Fluvial portions of the sequence include fresh water sandstone, shale, siltstone and mudstone with interbedded impure limestone units. Though the information pertaining directly to the WSA is limited, it is reasonable to assume that the Triassic environments favorable for copper-silver mineralization may have existed throughout this area during this period. The Jurassic rocks exposed in the WSA are thought to represent a period of fluvial and eolian deposition in small, restricted basins. The out- crops of the Jurassic Entrada, Sumraerville, and Morrison Formations have been heavily prospected for uranium-vanadium mineralization. Airborne radiometric anomalies were followed up by the Department of Energy and other government agencies under a number of different programs. To date, no major orebodies have been identified within the boundaries of the WSA. Conditions favorable for uranium-vanadium mineralization are thought to exist in this general suite of Jurassic rocks, but the only known mineralization is found associated with outcrops of the Salt Wash Member of the Morrison in the Wild Steer Canyon area. Subsequent to Jurassic time, the area underwent uplift and erosion. No post- Jurassic Mesozoic or Cenezoic rock units are known to exist within the boundaries of the WSA, only on nearby mesas. Quaternary alluvial and colluvial deposits exist along La Sal Creek and the Dolores River. These Quaternary units have provided sand and gravel material for local use in the past and may represent an industrial mineral resource (BLM MRI Maps and File Data). TABEGUACHE CREEK WSA (CO-030-300) Within the boundaries of the WSA, the Precambrian section is not exposed. The Precambrian units are known to underlie this area, but have been found only in upfaulted blocks that are within 10,000 feet of the present surface. This was a time of intrusion of granitic bodies into the older Precambrian sequence of gneiss, schist and intrusives. The drilling in the nearby Paradox Valley area has encountered granitic units at depths up to 10,000 to 15,000 feet (Baars et al . , 1981). The pre-Pennsylvanian Paleozoic section is not exposed within the study area, but may exist at some depth under the WSA. During this period of early and middle Paleozoic deposition, basins that formed along the margins of the Uncom- pahgre Uplift were receiving sediments from the adjacent terrestrial highlands. These basins were filled with clastic marine sediments and were, in turn, down- faulted into mobile rift zones (Baars et al., 1981). During Pennsylvanian times, thick evaporite sequences were laid down in these basins and were subsequently deformed by tectonic stresses into salt anticlinal and domal features (Baars et al., 1981). Directly west of the WSA in the Paradox Valley area, the clastic units of the Permian Cutler Formation are locally directly underlain by the Triassic Moenkopi Formation. The Culter, thus, may also be present within the boundaries of the WSA. This unit represents a period of clastic deposition adjacent to a terrestrial highland. It is thought that this sedimentation continued until the Precambrian and Lower Paleozoic topographic highs were inundated by sediments. It is thought that this unit was deposited as a fanglomerate adjacent to a rapidly eroding terrestrial high (Shoemaker, 1956). 11-13 The basal units exposed within the WSA include the Triassic Chinle Formation and Wingate Sandstones. The Chinle and Wingate Formations crop out in the bottom of the canyons that cut through the WSA. These units and the overlying Jurassic sec- tion are thought to represent a period of sedimentation in a near-shore marine and terrestrial environments with episodes of eolian deposition. The overlying Kayenta Formation units were probably also deposited in a terrestrial and near-shore marine environment. The Jurassic sequence is represented by a few outcrops of the Entrada Sandstone and Summerville Formation in the central part of the WSA. These units were deposited in fluvial and lacustrine environments that were adjacent to near- shore lagoons. The outcrops of the Jurassic Morrison Formation found in the WSA are thought to have been deposited in a fluvial environment. Uranium-vanadium- copper mineralization has been found nearby associated with the Salt Wash Member of the Morrison in the vicinity of Uravan, Colorado some 10 miles to the west. Uranium-vanadium mineralization commonly occurs in the Salt Wash Member associated with roll fronts and accumulations of organic material in meandering fluvial systems (Shoemaker, 1956). During Lower Cretaceous time, the area was the site of shallow-water deposition in a lagoonal or swamp environment. The Lower Cretaceous Burro Canyon Formation appears to have been deposited in a series of meandering river systems with adjacent terrestrial lakes. The terrestrial, clastic nature of this formation is thought to be characteristic of a beach or marine environment (Young, 1955). The Upper Cretaceous Dakota Sandstone unconf ormably overlies the Burro Canyon Forma- tion, and was probably deposited on an irregular surface of Burro Canyon outcrops rather than a true erosion surface (Carter et al, 1965). Portions of the Dakota are found as channel fillings upon the Burro Canyon paleosurface. From fossil evidence, it appears that the lower sections of the Dakota were deposited in shallow basins or stream channels with the source of the material being eroded masses of Pennsylvanian and Permian rocks that were then exposed (Carter et al, 1965). The carbonaceous shales of the Dakota are known to contain abundant plant remains, and were probably deposited in a near-shore swamp or lacustrine environ- ment. Thin coal seams are known to exist within the Dakota may have economic potential. The marine Mancos Shale is known to outcrop along the crest of the Nucla syncline and was probably deposited over much of the WSA. Subsequent to the Cretaceous, the area underwent uplift and erosion. No post- Cretaceous or Cenezoic deposits are known to exist within the boundaries of the WSA. Quaternary alluvial and colluvial deposits exist in the stream bed of Tabeguache Creek and may to represent a sand and gravel resource (BLM MRI Maps and File Data). Figures II-l through II-8 is a pictoral summary of the geological and physiographic characteristics of the GRA and associated WSA's. 11-14 DOLORES RIVER CANYON FIGURE 11-1 Confluence of Wild Star Canyon (right) and the Dolores River (looking NW). Area contains oil and gas wells (extension of producing field of Paradox Basin to right of photo). FIGURE II— 2 View looking SE along front of Davis Mesa. Uranium workings in Jurassic Morrison. DOLORES RIVER CANYON 11-15 >*: * afatt *M FIGURE 11-3 La Sal Creek Cashin copper-silver mine. DOLORES RIVER CANYON FIGURE 11-4 La Sal Canyon, Cliff Dweller mine in WSA. DOLORES RIVER CANYON 11-16 Fault or fracture Dolores — sandstone FIGURE 11-5 DOLORES RIVER CANYON Closeup of portal of Cliff Dweller mine. FauH mammmmM FIGURE 11-6 —Dolores I c o O 1 Forest Service Wilderness ■ ',.,''•< :1r'\l Proposed National Park Service ■■•'■■ ••■■■'■ or Forest Service Wilderness I / Hi k / T 47 N 5 Miles (After BLM, 1980) MMS/LEASABLE RESOURCES Figure IV- lb IV- 6 LEGEND FOR MINERALS MANAGEMENT SERVICE CLASSIFICATIONS Defined KGS and/or Coal Leasing Areas V Areas Prospectively Valuable for Sodium or Potassium Defined Oil Shale Leasing Area J Coal [PV] OG[PV] L_ Areas Identified as Prospectively Valuable for Coal or Oil, Gas Coal [NPV] OG [NPV] Areas Identified as Not Being Prospectively Valuable for Coal, or Oil, Gas IV- 7 LOCATABLE MINERALS DOLORES RIVER CANYON WSA (CO-030-290) Precious Metals 4D Base Metals 4D Ag, Au mineralization associated with Triassic Chinle and Wingate Formations, post production, active mining operations in adjacent areas. Cu mineralization associated with Triassic Chinle and Wingate Formations, post production, active mining operations in adjacent area. Locatable Energy Minerals 2B U-V mineralization potential associated with Triassic Chinle Formation. Other Locatable Minerals 3C Cypsum is known to occur in the Paradox Member, moderate economic potential TOBEGUACHE CREEK WSA (CO-03-300) Precious Metals 2B Ag mineralization potential in Triassic Chinle and Wingate Sandstone Formations, favorable section present . Base Metals 2B Cu mineralization potential in Triassic Chinle and Wingate Sandstone Formations, favorable section present. Locatable Energy Minerals 2B U-V mineralization potential Jurassic Morrison Formation. in Other Locatable Minerals 3C Gypsum is known to occur in the Paradox Member, poor economic potential IV-8 CO-030-290 Dolores River Canyon/Coyote Wash LOCATABLE RESOURCES Figure IV- 2a f* IV-9 CO 030 300 Tabeguache Creek R 16 W R 15 W 5 Miles (After BLM. 1980) LOCATABLE RESOURCES Figure IV- 2b IV-10 SALABLE RESOURCES Resource Limestone DOLORES RIVER CANYON WSA (CO-030-290) Classifications 3C Comments The Paradox Formation may contain favorable units. Moderate economic potential. Resource Building or Dimension Stone TABEGUACHE CREEK WSA (CO-030-300) Classifications Comments 4D The Dakota Formation is a favorable unit The economic potential is low to moderate. IV- 11 CO-030290 Dolores River Canyon/Coyote Wash LU (/) O DC H t,1 ^ ""P O CO 0» SALABLE RESOURCES Figure IV- 3a {* IV- 12 CO-030-300 Tabeguache Creek R 16 W R 15 W Proposed National Park Service or Forest Service Wilderness "T^l. I \ E>»K" 5 Miles (After BLM, 1880) SALABLE RESOURCES Figure IV- 3b IV- 13 SECTION V RECOMMENDATIONS FOR FURTHER STUDY In the course of analyzing, assessing, and evaluating each of the WSA's in the Dolores River Canyon-Tabeguache Creek. GRA, both in the field and in available data, certain unknowns were uncovered that should be investigated in order that each WSA's GEM resources be more fully documented. This section recommends the type of studies and data gathering that should be made to inventory more completely each WSA. DOLORES RIVER CANYON WSA (CO-030-290) Since this area is known to have potential for oil, gas, base, precious metal, and uranium resources, it is recommended that every effort be made to ascertain the full extent of this potential. Cooperative agreements should be made with various oil and gas producers to obtain proprietary information not available to this study. Such information as the projected reserves of the area, the importance of structural and stratigraphic zones in localizing oil and gas pools, and the exact identification of pay zones within the generally favorable lithologies is of vital importance in the exact areal delineation of subsurface potential. Examination of any outcrops of the Jurassic Morrison within the WSA for uranium- vanadium should be made in the course of any geologic mapping program. Detailed geologic and geochemical studies are warranted to ascertain the mineral potential of the Mesozoic lithologies. Within Triassic Chinle and Wingate Forma- tions, stratigraphic and lithogacies mapping should be carried out to determine if any environments with favorable depositional characteristics exist. A relatively low-cost way to accomplish these goals is to conduct a stream sediment and outcrop sampling program in conjunction with a geologic mapping effort. Any prospects and known mineral occurrences within the WSA should be verified, mapped, and thoroughly sampled to delineate the full extent of the existing mineralization and the potential of the host lithologies. This is of particular importance in the determination of the uranium- vanadium potential of the Jurassic Morrison Formation. With regards to this specific unit, a detailed study should be made of facies changes within it and correlation made with other units in western Colorado and eastern Utah. Within the WSA and in adjacent areas, the Salt Wash Member of the Morrison Formation is known to have significant uranium-vanadium mineralization and thus, should be studied in this area. Though the airborne and ground (NURE-HSSR-ARMS) information does not delineate any specific areas within the WSA with anomalous values, ground radiometrics in conjunction with the geological-geochemical would be helpful in identifying any areas of mineral poten- tial. Stream-sediment samples should be analyzed for their copper, molybdenum, lead, arsenic, uranium, vanadium, and gold content. This data will supplement the exist- ing NURE-HSSR-ARMS information. V-l Since some of the Mesozoic units have been used in the past as a source of local road building material, it would be wise to do further work on the demand for this material. In conclusion, from the work to date and the material compiled in the course of this project, it appears that the potential for GEM resources in this area is largely unknown. It is recommended that this area receive further extensive study prior to any decision as to its inclusion in the Wilderness System. (For further detailed discussion of the potential thought to exist within the WSA, refer to Section IV). TABEGUACHE CREEK WSA (CO-030-300) In this area the potential for GEM resources is largely unknown. Detailed geologic and geochemical studies are warranted to ascertain the mineral potential of the Precambrian and Mesozoic lithologies. Special attention should be paid to possible sedimentary and felsic lithologic assemblages associated with Precambrian base and precious metal exhalite systems. Of equal importance is the potential for base metal mineralization in the Triassic Chinle and Wingate Formations. Stratigraphic and lithofacies mapping should be carried out to determine if any environments with favorable depositional characteristics exist. A relatively low-cost way to accomplish these goals is to conduct a stream sediment and outcrop sampling program in conjunction with a geologic mapping effort. Any prospects and mineral occurrences should be verified, mapped, and thoroughly sampled to delineate the full extent of the existing mineralization and the poten- tial of the host lithologies. This is of particular importance in the determina- tion of the uranium-vanadium potential of the Jurassic Morrison Formation and the coal potential of the Cretaceous Dakota Sandstone. With regards to these specific units, a detailed study should be made of facies changes within these units, and the correlations with other units in western Colorado and eastern Utah. In other areas these units have significant potential GEM resources and thus, should be studied in this area where there is little available information. Though the airborne and ground NURE-HSSR-ARMS information does not delineate any areas with anomalous values, ground radiometrics in conjunction with the geological- geochemical would be helpful in identifying any areas of mineral potential. The potential coal beds in the Cretaceous Dakota section should be mapped in detail and sampled. Analysis for Btu, ash and sulphur content of each deposit should be made and the extent of the bed or beds delineated. Stream sediment samples should be analyzed for their copper, molybdenum, lead, arsenic, uranium, vanadium and gold content. This data will supplement the exist- ing NURE-HSSR information. In conclusion, from the work to date and the material compiled in the course of this GRA, it appears that the potential for GEM resources in this area is largely unknown. It is recommended that this are receive further extensive study (For fur- ther detailed discussion of the potential thought to exist within the WSA, please refer to Section IV) . V-2 SECTION VI REFERENCES AND SELECTED BIBLIOGRAPHY REFERENCES Baars, D.L. et al, 1981, Tectonic evaluation of the Paradox Basin, Utah and Colorado: in Geology of the Paradox Basin; Rocky Mountain Associated Geology, Field Conf., Guidebook 1981, pp 23-31. Bureau of Land Management, 1982, Mineral Resources Inventory, File Data, BLM Grand Junction District Office. Carpenter, Dr. R. , Personal Communication; Expert on mineral deposits and geology of Colorado. Carter, Kenneth, E., 1958, Relation of Paradox Basin oil to stratigraphy; in Guidebook of the Black Mesa Basin, Northweastern Arizona 9th Field Conf., p 202. Carter, W.D. et al, 1965, Geology and Uranium-Vanadium deposits of the LaSal quandrangle, San Juan County, Utah and Montrose County, Colorado; USGS Prof. Paper 508. Cater, F.W., Jr. 1955, Geology of the Anderson Mesa quadrangle; U.S.G.S. Geol. Quad. Maps, GQ-77, scale 1:24,000. Cater, F.W., Jr., 1955, Geology of the Davis Mesa quadrangle; U.S.G.S. Geol. Quad. Maps, GQ-71, Scale 1:24,000. Cater, F.W., Jr. 1955, Geology of the Calamity Mesa quadrangle; U.S.G.S. Geol. Quad. Maps, GQ-61, Scale 1:24,000. Cater, F.W., Jr., 1955, Geologic map of the Gateway quadrangle, Colorado; U.S.G.S., Geol. Quad. Maps GQ-55, Scale 1:24,000. Cater, F.W., 1970, Geology of the Salt Anticline region in southwestern Colorado; U.S.G.S. Prof. Paper 637. Colorado Division of Mines, 1981, A summary of mineral industry activities in Colorado, 1980, Part I: Coal and Part II: Metal-Nonmetal. Craig, L.C. et al, 1955, Stratigraphy of the Morrison and related formations, Colorado Plateau region - a preliminary report; U.S.G.S. Bull. 1009-E, pp 125-168. Engineering and Mining Journal, December, 1982. Eyde, T. 1982, Personal Communication; Expert on industrial mineral resources. Fisher, R.P. 1956, Uranium-vanadium-copper deposits on the Colorado Plateau; U.S.G.S. Prof. Paper 300, pp 143-154. VI-1 Fisher, R.P. 1936, Peculiar hydro thermal copper-bearing veins of the northeastern Colorado Plateau, Econ. Geol., Vol. 31, pp 571-599. Gentry, Dr. D. 1982, Personal Communication; Expert on coal and oil shale deposits in Colorado. Gilmour, Dr. P. 1982, Personal Communication; Expert on Precambrian mineral resources . Heylmun, E. 1982, Personal Communication; Expert on oil, gas, and oil shale deposits in the western U.S. Jones, D., and Murray, D. K. 1976, Oil and gas fields of Colorado, statistical data; Colo. Geol. Surv., Info. Ser. 3. Landis, E.R. 1959, Coal resources in Colorado; U.S.G.S. Bull. 1072-C. Mattox, R.B. 1968, Salt anticline field area, Paradox Basin, Colorado and Utah; Geol. Soc Am., Spec. Paper 88, pp 5-16. Molenaar, CM. 1981, Mesozoic stratigraphy of the Paradox Basin - an overview: in Geology of the Paradox Basin; Rocky Mtn. Assoc. Geol., Field Conf . , Guidebook, 1981, pp 119-127. National Park Service (NPS) 1982; Field data. Peterson, J. A. , 1963; Regional stratigraphy of the Paradox Basin [abstr.), GSA Spec. Paper 73; pp 280. Petroleum Times Price Report, October 15, 1982. Schwochow, S. 1978, Mineral Resources of Mesa County - a model study; Colo. Gel. Surv., Res. Ser. 2, HOp. Scott, G.L. et al, 1981, Seismic surveying, salt anticline region, Paradox Basin: in Geology of the Paradox Basin; Rocky Mtn. Assoc. Geol., Field Conf., 1981, pp 161-168. 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Speltz, C.N., 1976, Strippable coal resources of Colorado; location, tonnage, and characteristics of coal and overburden; USBM IC-8713. Steenland, Nelson, C, 1962, Gravity and aeromagnetic exploration in the Paradox Basin; Geophysics, Vol. 27, No. 1, p 73-89. Stewart, J.H., 1960, Triassic strata of the Salt anticline region, Colorado and Utah, in Geology of the Paradox Basin fold and fault belt; Four Corners Geol. Soc, 3rd Field Conf. Guidebook, pp 98-106. Stokes, Wiliam L., 1948, Geology of the Utah-Colorado Salt Dome Region with emphasis on Gypsum Valley, Colorado; Utah Geol. Soc, Guidebook, No. 3, 50 p. Sugiura, Ray, and Kitcho, K.A., 1981, Collapse structures in the Paradox Basin; in Geology of the Paradox Basin, Rocky Mtn. Assn. Geol., Field Conf., Guidebook, 1981, pp 33-45. Thompson, M.E., 1957, Duttonite, a new quadrivalent vanadium oxide from the Peanut Mine, Montrose County, Colorado; Am. Mineralogist, Vol. 42, No. 7-8, pp 455-460. 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