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Showing 71 to 76 of 76 (0.077 seconds)Spelling suggestions: "subject:"sedimentary rocks"" "subject:"redimentary rocks""
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Stratigraphy and Depositional History of the Pantano Formation (Oligocene-Early Miocene), Pima County, ArizonaBalcer, Richard Allen January 1984 (has links)
The Pantano Formation comprises 1,250 m of alluvial, fluvial, lacustrine, and volcanic rocks deposited in a basin formed in response to regional extension during mid- Tertiary time in southeastern Arizona. During deposition, the locations and composition of sediment source areas varied as contemporaneous uplift occurred adjacent to the basin. The lower half of the formation was deposited as alluvial fans that prograded northward, westward, and southward; the upper half was deposited during southwestward retreat of alluvial fan deposition and the onset of lacustrine deposition. An andesite flow separates the two depositional regimes. Radiometric dates of 24.4 ± 2.6 m.y. B.P. for the andesite and 36.7 ± 1.1 m.y. B.P. for a rhyolitic tuff disconformably underlying the formation indicate that deposition occurred during Oligocene to early Miocene time. Proper stratigraphic sequencing and description, paleocurrent analysis, and gravel provenance study aided in understanding the depositional history of the formation.
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Groundwater Geology of Fort Valley, Coconino County, ArizonaDeWitt, Ronald H. 05 May 1973 (has links)
From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / All groundwater in fort valley is presently found in perched aquifers. The regional water table in the area is estimated to lie at a depth of approximately 1750 feet. Groundwater reservoirs are perched on impermeable clay zones located at the base of alluvial units. Groundwater is also found in highly fractured volcanic zones overlaying impermeable clay zones. Perched aquifers also occur in interflow zones above either impermeable clays or unfractured volcanics. Groundwater in fort valley is the result of infiltration or runoff and from precipitation. This recharge water infiltrates the alluvium or fractured volcanic rocks until an impermeable zone is reached where it becomes perched groundwater. Greatest well yields come from these recharge aquifers; their reliability is largely dependent on precipitation and runoff. Most wells in the fort valley area supply adequate amounts of water for domestic use.
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Geology and Origin of the Breccias in the Morenci-Metcalf District, Greenlee County, ArizonaBennett, Kenneth Carlton January 1975 (has links)
Rocks of the Morenci-Metcalf district consist of Precambrian metaquartzite-schist, granodiorite, and granite overlain by Paleozoic and Mesozoic sediments. Intrusion of igneous rocks, emplacement of breccia masses, and associated hydrothermal activity occurred in Laramide time. Breccias of the district are associated with the youngest sialic intrusive complex. This sequence includes intrusion of the Older Granite Porphyry stock, main stage district hydrothermal alteration, quartz veining, breccia formation, main stage district hydrothermal mineralization, and intrusion of the Younger Granite Porphyry plug. Breccia formation in the Morenci-Metcalf district is similar to breccia descriptions reported in the literature for other porphyry copper deposits. Three breccia types, of separate and distinct origins, are herein described as the Morenci, Metcalf and King, and Candelaria Breccias. The Morenci Breccia is an intrusion breccia that has formed along a pre-existing structural feature during the ascent and emplacement of the Older Granite Porphyry stock. It exhibits an oblate lenticular shape with angular to subrounded fragments in a matrix of quartz, K-feldspar, biotite, and minor rock flour. The Metcalf-King Breccias and numerous smaller breccia masses are the remnants of an original Older Granite Porphyry mantle above the ascending Younger Granite Porphyry complex. The breccia masses occur as large 'xenoliths' floating within the Younger Granite Porphyry plug and were formed by surging and collapse during emplacement of this intrusive. Fragments in the Metcalf and King Breccias grade from angular in the central core to rounded at the contacts and occur in a matrix of sericite, K- feldspar, quartz, and rock flour. The Candelaria Breccia is an explosion pipe and is the largest continuous breccia mass in the district. It is oval with an inverted cone appearance consisting of angular to subangular equidimensional fragments in a matrix of sericite, quartz, specularite, and rock flour. All the breccia masses occur within and subsequent to the district phyllic (quartz-sericite-pyrite) alteration zone. Main stage district copper mineralization postdates emplacement of the Older Granite Porphyry stock and breccia formation, and is prior to the intrusion of the Younger Granite Porphyry plug. Late stage quartz-sericite-pyrite-chalcopyrite veinlets occur in the Metcalf-King Breccia group. Field mapping and laboratory studies indicate that the Older Granite Porphyry stock appears to have been the main district mineralizer.
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Paleocurrents and Depositional Environments of the Dakota Group (Cretaceous), San Miguel County, New MexicoBejnar, Craig Russel January 1975 (has links)
The Dakota Group surrounding Las Vegas, New Mexico, consists of three units: 1) a basal, predominately trough cross-stratified, conglomeratic sandstone, 2) middle intercalated, thin-bedded sandstone and carbonaceous shale, and 3) upper, predominately tabular-planar cross-stratified, sandstone containing trace fossils. These units represent, respectively, 1) a fluvial piedmont plain, 2) fluvial coastal plain, and 3) a beach, littoral, and shallow marine complex. The cross-stratification in the lower sandstone unit indicates an easterly paleoslope. The cross-stratification in the upper sandstone unit has a bimodal distribution almost at right angles to the paleoslope, suggesting deposition by longshore currents. The standard deviation of the cross-stratification in the lower sandstone unit of 78° is typical of fluvial deposits. The standard deviation in the upper sandstone unit of 97° indicates a marine origin.
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Charakterisierung des hydromechanischen Verhaltens der Gesteine des Mittleren Buntsandsteins im Hinblick auf eine geothermische Nutzung: Strukturgeologische Geländeaufnahmen, gesteinsmechanische Untersuchungen und numerische Modellierungen / Characterisation of hydro-mechanical processes in the Middle Buntsandstein formation with regard to the utilisation of geothermal energy: Field studies, geomechanical measurements and numerical modellingMüller, Christian 21 July 2009 (has links)
No description available.
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Stratigraphy and Sedimentology of the Bisbee Group in the Whetstone Mountains, Pima and Cochise Counties, Southeastern ArizonaArchibald, Lawrence Eben January 1982 (has links)
The Aptian-Santonian(?) Bisbee Group in the Whetstone Mountains comprises 2375 m of clastic sedimentary rocks and limestones. The basal Glance Conglomerate unconformably overlies the Pennsylvanian-Permian Naco Group. It consists of limestone conglomerates which were deposited in proximal alluvial fan environments. The superadjacent Willow Canyon Formation contains finer grained rocks which were deposited in the distal portions of alluvial fans. The lacustrine limestones in the Apache Canyon Formation interfinger with and overlie these alluvial fan facies. The overlying Shellenberger Canyon Formation is composed mostly of terrigenous rocks derived from westerly terranes. This formation contains thick sequences of fluvio-deltaic facies as well as a thin interval of estuarine deposits which mark a northwestern extension of the marine transgression in the Bisbee -Chihuahua Embayment. The youngest formation (Upper Cretaceous?) in the Bisbee Group, the Turney Ranch Formation, consists of interbedded sandstones and marls which were deposited by fluvial and marine(?) processes.
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