The Swisshelm Quartz Monsonite covers about two square miles on the western slope of the Swisshelm Mountains, Cochise County, Arizona. Field observation and petrographic study indicate that the quartz monsonite was derived by differentiation and late-stage alkali metasomation of probably a quartz dioritic magma rich in alkali and volatile constituents. The high concentration of the volatiles is believed to be of great importance in the development of the different facies and rock types. Four different facies of the Swisshelm Quartz Monsonite have been distinguished as (1) the normal facies, (2) the altered facies, (3) the fine-grained facies, and (4) the contact facies. Also, several aplite dikes, local beryl-bearing pegmatite patches, and numerous quartz veins are present and attributed to late magmatic differentiation. Inclusions of an early and late magmatic facies are sparcely disseminated through the quartz monsonite. The Swisshelm Quartz Monsonite magma has intruded and metamorphosed the Upper Paleozoic sediments of the Mace Group as well as the Lower Cretaceous sediments of the Bisbee Group. The metamorphism is of a contact metasomatic type to which the mineralogical and textural changes in the country rocks have been attributed.

No description available.

No description available.

Greenschist-facies, Lower Proterozoic metasedimentary rocks of the Johnny Lyon Rills and Little Dragoon Mountains of southeastern Arizona were deposited prior to the intrusion of an approximately 1690 Ma rhyodacite pluton. Well-preserved primary structures indicate deposition by turbidity currents in an intermediate to neardistal setting. Sandstone compositions suggest derivation from either a complex, heterogeneous source or multiple source terranes that provided mature, quartzose sediment as well as lesser quantities of volcaniclastic detritus. Earliest deformation, predating both intrusion of the rhyodacite and metamorphism, produced sections of melange composed primarily of dismembered turbidite beds, but also incorporating large (up to several km long) blocks of deformed basalt. Subsequent deformation, in part post-dating intrusion of the rhyodacite and in part coinciding with metamorphism, affected both melange and coherent strata, and involved isoclinal folding and layerparallel faulting and shearing. It is proposed that turbidite deposition occurred in a trench associated with a north-dipping subduction zone or on ocean floor outboard of such a trench. Melange formed primarily by ductile disruption of unlithified sediments within the subduction zone. Basalt blocks incorporated within the melange represent fragments of oceanic crust or seamounts detached from the lower plate during subduction. Later deformation and intrusion of the rhyodacite occurred within an accretionary prism above the subduction zone. Deformation within the prism ended prior to intrusion of the 1625 ± 10 Ma posttectonic Johnny Lyon Granodiorite.

A complex late Quaternary alluvial sequence is exposed in Whitewater Draw arroyo, Cochise County, Arizona. The alluvial history is characterized by: (1) sand and gravel deposition in a through-flowing stream between 15,000-8,000 yr B.P. and 6,700-5,500 yr B.P. and (2) cycles of erosion and clay-and-silt deposition in large wet meadows or cienegas between 8,000-6,700 yr B.P. and 5,500 yr B.P.-historic period. Modern arroyo entrenchment began after A.D. 1885 and was largely completed before 1910. The alluvial sequence of the Douglas basin differs in timing, character, and number of degradational and aggradational events, with the exception of the arroyo cutting and filling episode between 6,700 and 5,500 yr B.P., when compared to the alluvial sequence of the adjacent San Pedro Valley and the generalized alluvial chronology for the West. Megafaunal extinction occurred in the Douglas basin no later than 10,400 yr B.P. as evidenced by the occurrence of articulated camel and mammoth remains in sediments of this age. Mammoth, horse, camel, and dire wolf remains from deposits dating 10,400 to 7,000 yr B.P. are in secondary contexts, redeposited from older units. Archaeological remains of the Cochise Culture occur in nearly all the Upper Quaternary deposits of Whitewater Draw. Artifacts of the Sulphur Spring phase, the earliest phase of the Cochise Culture, are found at four sites in Whitewater Draw and at the Lehner site, where they overlie the Clovis horizon. Ground-stone artifacts are the most common element of the Sulphur Spring artifact assemblage and indicate that the Douglas basin was the site of specialized plant gathering and processing. Flaked-stone artifacts are poorly represented and are primarily unifacially retouched flake tools but also include bifacially flaked projectile points. The Sulphur Spring phase dates from 8,000 to 10,000 yr B.P. and probably to 10,500 yr B.P. Evidence suggests that the Sulphur Spring people may have temporally overlapped with relict populations of Pleistocene megafauna during the onset of the Holocene. The Sulphur Spring and western San Dieguito I complex are considered to be temporal equivalents. The Cazador phase is no longer considered a valid phase of the Cochise Culture. Cazador artifacts at the type site occur in deposits equivalent in age to sediments containing Sulphur Spring remains.

A physically based, distributed parameter, event oriented, nonlinear, numerical model of watershed response is developed to accommodate the spatial changes in topography, surface roughness, soil properties, concentrated flow patterns and geometry, and land use conditions. The Green and Ampt equation with the ponding time calculation for an unsteady rain is used to compute rainfall excess rates. The kinematic wave equations are used to describe the unsteady one-dimensional overland and channel flow. The unsteady and spatially varying erosion/deposition process on hillslopes and channel systems is described dynamically using simultaneous rates of sediment entrainment and deposition rather than the conventional approach using steady state sediment transport functions. To apply the model the watershed is represented by a simplified geometry consisting of discrete overland flow planes and channel elements. Each plane or channel is characterized by a length, width, and a roughness parameter. For channel elements, a cross-section geometry is also needed. A modular computer program called WESP (Watershed Erosion Simulation Program) is developed to provide the vehicle for performing the computer simulations. Rainfall simulator plots are used to estimate infiltration parameters, hydraulic roughness, and soil erodibility parameters for raindrop impact and overland flow. The ability of the model to simulate watershed response (hydrograph and sedigraph) to a variety of rainfall inputs and antecedent soil moisture conditions is verified using data collected on two small watersheds. The good agreement between the simulated watershed response and the observed watershed response indicates that the governing equations, initial and upper boundary conditions, and structural framework of the model can describe satisfactorily the physical processes controlling watershed response.

Soils darken upon wetting due to changes in the scattering properties of the individual soil particles. The objective of this research was to develop a procedure to map the distribution of wet soils using the radiance measurements acquired by a spaceborne imaging scanner. The soil-mapping procedure was designed for use in the regional exploration for ground water resources. The soil-mapping procedure was based upon the detection of reflectance changes in a comparison of Landsat 5 Thematic Mapper (TM) scenes acquired before and after a rain. The Stronghold watershed, which is situated on the western slopes of the Dragoon Mountains, Cochise County, Arizona, was chosen as the test site for the soil-mapping procedure. TM scenes depicting the watershed on 7 June 1985 and 14 November 1985 were used in the change-detection analysis. The region was dry at the time of the June overpass, the November overpass occurred two days after a rain. The recovery of reflectance from radiance requires knowledge of 1) the orientation of the surface relative to the sun and the satellite, 2) the exoatmospheric solar irradiance, 3) the atmospheric optical depth, and 4) the atmospheric path radiance. The orientation of the surface elements were defined through the use of a digital elevation model of the Stronghold watershed. The solar irradiance and atmospheric optical depth were obtained from the literature; the atmospheric path radiance was estimated from shadowed areas depicted in the images. Temporal changes in reflectance were detected by subtracting the November reflectance estimates from those recovered from the June radiance measurements. Changes significant at the 0.05 level were identified through use of the Student-t test. The identical significance level was used to identify temporal changes in the Perpendicular Vegetation Index, or PVI. A surface element was classified as an anomaly if there was a significant temporal change in reflectance with no attendant change in PVI. Field checks of the anomalies proved that wet soils could be mapped via the remote detection of changes in their reflectance. The majority of the false anomalies could be attributed to the disparity between the spatial resolutions of the radiance measurements and the topographic data.

No description available.

No description available.

No description available.