Abstract Paradox Valley is located in west-central Colorado, in western Montrose County (Fig. 1). The valley is approximately 23 mi (37 km) long and averages 3 mi (5 km) in width. It occupies a large part of T.46N., R.17W.;T.47N., R.18 and 19W.; and T.48N., R. 19W. Colorado 90 traverses the valley for nearly its full length. This highway begins at Vancorum, which is on Colorado 141 about 2 mi (3 km) west of Naturita, Colorado. Naturita, the largest settlement in the area, is about 100 mi ( 161 km) south of Grand Junction, Colorado, on Colorado 141. After leaving the northwest end of Par Utah. Paradox and Bedrock, Colorado, are the only settlements in the valley. County roads (marked with signs) provide access to the rims of the valley as well as the canyon of the Dolores River on both sides of the valley. Molenaar and others (1981, p. 7–9) give a detailed road log of the valley. The majority of land in the Paradox Valley area is in the public domain, administered by the Bureau of Land Management. West oprivate land, owned by ranchers in Paradox. About 15 percent of the valley floor east of the river is privately owned. The vallems are all public domain, with the exception of numerous patented mining claims.

Abstract DAY ONE - GRAND JUNCTION TO MOAB OCTOBER 20, 7:00 AM HAVE VEHICLES GASSED UP; IT IS 193 MILES TO MOAB, UTAH, WITH VERY LIMITED AND UNRELIABLE SERVICES; WATER AND LUNCH PROVIDED AS PART OF TRIP REGISTRATION. 0.0 (0.0) Depart from the parking lot of the Super 8 Motel, near the intersection of Horizon Drive and Interstate 25. Right turn onto Horizon Drive. 0.1 (0.1) Right turn and enter Interstate 25, Eastbound. Interstate 25 is built on Cretaceous Mancos Shale (marine); Mesa Verde Group sandstone strata capping the Book Cliffs (right) were deposited on the regressive margin of the Cretaceous Interior Seaway section (off-shore sand bars, lagoons, fluvial systems and coal swamps). The promontory on the right near the highway is Mount Garfield, the east end of the Book Cliffs, which extend from Price, Utah to Grand Junction, as a continuous topographic feature. The high plateau on the skyline (12:00) is Grand Mesa, elevation over 10,000 ft. Across the Grand Valley, to the west, is the Uncompaghre Plateau, which the field trip will cross through Unaweep Canyon. 5.5 (5.4) Exit Interstate 25 (Exit 37) to Clifton and Delta; I-70 Business Loop. 6.5 (1.0) First stop light; go straight through. 6.9 (0.4) Second stop light; left turn onto Colorado Highway 141, to US-50, Delta and Montrose. Last predictable chance for gasoline, food, and bathrooms is service stations in the next 2

Abstract In the Paradox basin, epigenetic, post-lithification deposition of copper sulfides in stratiform sediment-hosted deposits is the result of two sequential episodes of basinal fluid expulsion. The earlier fluid was a sulfur-bearing, reducing, aqueous fluid that bleached red sandstones as hematite was reduced to pyrite ( Thorson, 2004 ; MacIntyre et al., 2004 , 2005 ). This fluid rose buoyantly through the section along marginal breccia zones adjacent to salt diapirs, or along faults, and flowed laterally in permeable strata. Regional geology and burial history analyses suggest a Late Jurassic age for the early fluid event as organic-rich black shale in the Paradox Formation evaporites entered the oil window. The second episode of fluid expulsion involved oxidized warm saline brines carrying copper, silver, and other base metals. At Lisbon Valley and Cashin mine, minerals deposited by the second fluid are zoned from hematite ± native copper, through chalcocite, bornite, and chalcopyrite zones, to peripheral pyrite + lead and zinc. Copper sulfides are disseminated, partially or completely filling intergranular spaces in sandstone bleached during alteration by the first fluid. Gangue minerals in feeder fault structures are saddle dolomite and barite. Homogenization temperatures from fluid inclusions in these gangue minerals are between 70° and 110°C; salinities are variable but as high as 21% NaCl equiv ( Morrison and Parry, 1986 ; Breit and Meunier, 1990 ; Gray et al., 1996 ). Fluid inclusions from bleached Jurassic sandstones and from the Cashin fault contain hydrocarbon droplets from Pennsylvanian Paradox blac shale source rocks. Paleomagnetic data and burial history analyses suggest a Late Cretaceous or early Tertiary age for the second episode of fluid expulsion as Cutler Formation arkosic red beds subsided into the oil window. The copper deposit at Lisbon Valley and Cashin mines are the result of both fluid expulsion episodes. The earlier fluid prepared otherwise unfavorable host rocks by reducing hematite to pyrite and depositing hydrocarbons. The second fluid deposited copper as sulfides that replaced pyrite, calcite, bituminous hydrocarbon, and coaly plant material. The Paradox basin is a Pennsylvanian halfgraben rift that initially received several thousand feet of evaporites designated as the Paradox Formation or the Paradox member of the Hermosa Formation (Fig. 1 ). Many authors define the Paradox basin by the zero thickness edge of the evaporite facies, but a significant area of Pennsylvanian shelf carbonates was deposited in less restricted conditions on the west, south, and east sides of the basin (Fig. 2 , this paper; Hite, 1970). The evaporites occur as cyclical deposits of silty dolomite, black shale, anhydrite, and halite; a few cycles in the most restricted areas contain potassium salts (Hite, 1961; Hite and Buckner, 1981).