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Relation between ages and elevations of Martian channels

Mapping highland and lowland channels and reassessing their time-stratigraphic positions shows that many channels in the cratered highlands are younger than Noachian, that all channels in the lowland plains are Hesperian or younger, and that although Martian channels formed throughout the planet's history, the rate of their formation appears to have declined with time. This detailed examination of the age relation between Martian terrains and the channels that transect them was made possible by the completion of the global geologic maps of Mars and the availability of other geologic maps at scales of 1:5,000,000, 1:2,000,000, and 1:500,000. The present study focuses on the sources (heads) of the channels of the initial study to see if there is a relation between channel age and elevation.

Dohm, James M.↗

Application of remote sensing techniques to the geology of the bonanza volcanic center

A program is reported for evaluating remote sensing as an aid to geologic mapping for the past four years. Data tested in this evaluation include color and color infrared photography, multiband photography, low sun-angle photography, thermal infrared scanner imagery, and side-looking airborne radar. The relative utility of color and color infrared photography was tested as it was used to refine geologic maps in previously mapped areas, as field photos while mapping in the field, and in making photogeologic maps prior to field mapping. The latter technique served as a test of the maximum utility of the photography. In this application the photography was used successfully to locate 75% of all faults in a portion of the geologically complex Bonanza volcanic center and to map and correctly identify 93% of all Quaternary deposits and 62% of all areas of Tertiary volcanic outcrop in the area.

Marrs, R. W.↗

Geological-structural interpretation using products of remote sensing in the region of Carrancas, Minas Gerais, Brazil

The efficiency of some criteria developed for the utilization of small scale and low resolution remote sensing products to map geological and structural features was demonstrated. Those criteria were adapted from the Logical Method of Photointerpretation which consists of textural qualitative analysis of landforms and drainage net patterns. LANDSAT images of channel 5 and 7, 4 LANDSAT-RBV scenes, and 1 radar mosiac were utilized. The region of study is characterized by supracrustal metassediments (quartzites and micaschist) folded according to a "zig-zag" pattern and gnaissic basement. Lithological-structural definition was considered outstanding when compared to data acquired during field work, bibliographic data and geologic maps acquired in larger scales.

Parada, N. D. J.↗

Beta Regio rift system on Venus: Geologic interpretation of Magellan images

Magellan SAR images and altimetric data were used to produce a new geologic map of the Northern part of Beta Regio within the frames of C1-30N279 mapsheet. It was part of our contributions into C1-formate geologic mapping efforts. The original map is at 1:8,000,000 scale. The rift structures are typical for Beta Regio on Venus. There are many large uplifted tessera areas on Beta upland. They occupy areas of higher topography. These tessera are partly burried by younger volcanic cover of plain material. These observations show that Beta upland was formed mainly due to lithospheric tectonical uplifting, and only partly was constructed by volcanic activity. A number of rift valleis traverse Beta upland and spread to the surrounding lowlands. The largest rift crosses Beta N to S. Typical width of rifts is 40 to 160 km. Rift valleis in this region are structurally represented by crustal grabens and half-grabens. There are symmetrical and asymmetrical rifts. A lot of them have shoulder uplifts with the relative high up to 0.5-1 km and width 40 to 60 km. Preliminary analysis of the largest rift valley structural cross-sections leads to the conclusion that it originated due to a 5-10 percent crustal extension. The prominent shield volcano - Theia Mons - is located at the center of Beta rift system. It could be considered as the surface manifestation of the upper mantle hot spot. Most of the rift belts are located radially to Theia Mons. The set of these data leads to conclusion that Beta rift system has an 'active-passive' origin. It was formed due to the regional tectonic lithospheric extension. Rifting was accelerated by the upper mantle hot spot located under the center of passive extension (under Beta Regio).

Nikishin, A. M.↗

Classification of high dimensional multispectral image data

A method for classifying high dimensional remote sensing data is described. The technique uses a radiometric adjustment to allow a human operator to identify and label training pixels by visually comparing the remotely sensed spectra to laboratory reflectance spectra. Training pixels for material without obvious spectral features are identified by traditional means. Features which are effective for discriminating between the classes are then derived from the original radiance data and used to classify the scene. This technique is applied to Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data taken over Cuprite, Nevada in 1992, and the results are compared to an existing geologic map. This technique performed well even with noisy data and the fact that some of the materials in the scene lack absorption features. No adjustment for the atmosphere or other scene variables was made to the data classified. While the experimental results compare favorably with an existing geologic map, the primary purpose of this research was to demonstrate the classification method, as compared to the geology of the Cuprite scene.

Hoffbeck, Joseph P.↗

Mars paleostratigraphy

The relative time of emplacement of some major rock units on Mars was recognized to some degree from geologic mapping using Mariner Images. Correlation charts showing the map units and their position in sequence, however, displayed little discrimination in their vertical range of occurrence. A more detailed time-stratigraphy is currently being developed as Viking geologic mapping of the planet progresses.

Scott, D. H.↗

An inventory of undiscovered Canadian mineral resources

Unit regional value (URV) and unit regional weight are area standardized measures of the expected value and quantity, respectively, of the mineral resources of a region. Estimation and manipulation of the URV statistic is the basis of an approach to mineral resource evaluation. Estimates of the kind and value of exploitable mineral resources yet to be discovered in the provinces of Canada are used as an illustration of the procedure. The URV statistic is set within a previously developed model wherein geology, as measured by point counting geologic maps, is related to the historical record of mineral resource production of well-developed regions of the world, such as the 50 states of the U.S.A.; these may be considered the training set. The Canadian provinces are related to this training set using geological information obtained in the same way from geologic maps of the provinces. The desired predictions of yet to be discovered mineral resources in the Canadian provinces arise as a consequence. The implicit assumption is that regions of similar geology, if equally well developed, will produce similar weights and values of mineral resources.

Labovitz, M. L.↗

Faulting and its relation to volcanism: Mars western equatorial region

Recently completed geologic maps of Mars show the global distribution of lava flows that were emplaced during each of the three Martian time-stratigraphic periods and the faults and ridges that originated during these periods. These data were extracted from the geologic maps to make a series of volcano-tectonic maps for the Noachian, Hesperian, and Amazonian Periods. The map series is being compiled on Viking photomosaics at 1:15,000,000 scale. These maps will provide a basis for assessing the interactive roles of volcanism and tectonism in the crustal evolution of Mars.

Scott, David H.↗

Mapping Hesperia Planum, Mars

Hesperia Planum, characterized by a high concentration of mare-type wrinkle ridges and ridge rings [1-4], encompasses > 2 million km2 in the southern highlands of Mars (Fig. 1). The most common interpretation is that the plains were emplaced as flood lavas with total thicknesses of <3 km [4-10]. The wrinkle ridges on its surface make Hesperia Planum the type locale for Hesperian-aged ridged plains on Mars [e.g., 9], and recent investigations reveal that wrinkle-ridge formation occurred in more than one episode [4]. Hesperia Planum s stratigraphic position and crater-retention age [e.g., 9, 11-12] define the base of the Hesperian System. However, preliminary results of geologic mapping reveal that the whole of Hesperia Planum is unlikely to be composed of the same materials, emplaced at the same geologic time. To unravel these complexities, we are generating a 1:1.5M-scale geologic map of Hesperia Planum and its surroundings (Fig. 1). To date, we have identified 4 distinct plains units within Hesperia Planum and are attempting to determine the nature and relative ages of these materials (Fig. 2) [13-15].

Gregg, Tracy K. P.↗

Mapping Tyrrhena Patera and Hesperia Planum, Mars

Hesperia Planum, characterized by a high concentration of mare-type wrinkle ridges and ridge rings [1-4], encompasses > 2 million sq km in the southern highlands of Mars (Fig. 1). The most common interpretation is that the plains were emplaced as "flood" lavas with total thicknesses of <3 km [4-10]. The wrinkle ridges on its surface make Hesperia Planum the type locale for "Hesperian-aged ridged plains" on Mars [e.g., 9], and recent investigations reveal that wrinkle-ridge formation occurred in more than one episode [4]. Hesperia Planum?s stratigraphic position and crater-retention age [e.g., 9, 11-12] define the base of the Hesperian System. However, results of geologic mapping reveal that the whole of Hesperia Planum is unlikely to be composed of the same materials, emplaced at the same geologic time. To unravel these complexities, we are generating a 1:1.5M-scale geologic map of Hesperia Planum and its surroundings (Fig. 1). We have identified 4 distinct plains units within Hesperia Planum and are attempting to determine the nature and relative ages of these materials (Fig. 2) [13, 14]. The volcano Tyrrhena Patera (22degS, 104degE) is located within Hesperia Planum. Its products are both embayed by, and superpose, Hesperia Planum materials [15, 16]. We were previously funded to generate a 1:1 million scale map of Mars Transverse Mercator (MTM) quadrangles -15257 and -20257, which include the Tyrrhena Patera materials north and west of the Tyrrhena Patera summit. The goal for these maps was to constrain the nature and extent of the Tyrrhena Patera deposits, and to determine the relationship between Tyrrhena Patera materials, Hesperia Planum, and the adjacent highlands [16].

Crown, David A.↗

Martian terrains

Terrain studies of candidate landing sites for a future rover/sample-return mission to Mars are being conducted to evaluate the geologic and trafficability aspects of each site. An optimum site should have geologic units of widely diverse ages and chemical compositions occurring in close enough proximity and in smooth enough terrain so that a roving vehicle of limited traverse ability (+ or - 100 km) could collect representative samples. In FY 1986, geologic maps were compiled at 1:500,000 and 1:2 million scales of the Mangala Valles, Kasei Valles, Chasma Boreale (north polar), and Planum Australe (south polar) areas, and a study was begun of the topography and surface roughness characteristics of the Mangala Valles site. Geologic mapping has been greatly facilitated by specially enhanced, high-resolution Viking photographs, which clarify stratigraphic relations of units unrecognized earlier. Photoclinometric profiles of topographic features provide width and depth measurements of four classes of channels, the thickness of some volcanic units, and the throw on some faults. Estimates of the surface roughness of units are calculated using a newly developed USGS computer program and using measurements derived from Earth-based radar.

Masursky, Harold↗

Age discrimination among eruptives of Menengai Caldera, Kenya, using vegetation parameters from satellite imagery

Results are presented of an investigation to determine the degree to which digitally processed Landsat TM imagery can be used to discriminate among vegetated lava flows of different ages in the Menengai Caldera, Kenya. A selective series of five images, consisting of a color-coded Landsat 5 classification and four color composites, are compared with geologic maps. The most recent of more than 70 postcaldera flows within the caldera are trachytes, which are variably covered by shrubs and subsidiary grasses. Soil development evolves as a function of time, and as such supports a changing plant community. Progressively older flows exhibit the increasing dominance of grasses over bushes. The Landsat images correlated well with geologic maps, but the two mapped age classes could be further subdivided on the basis of different vegetation communities. It is concluded that field maps can be modified, and in some cases corrected by use of such imagery, and that digitally enhanced Landsat imagery can be a useful aid to field mapping in similar terrains.

Blodget, Herbert W.↗

Multidisciplinary study of Wyoming test sites

The author has identified the following significant results. Investigation of a variety of applications of EREP photographic data demonstrated that EREP S-190 data offer a unique combination of synoptic coverage and image detail. The broad coverage is ideal for regional geologic mapping and tectonic analysis while the detail is adequate for mapping of crops, mines, urban areas, and other relatively small features. The investigative team at the University of Wyoming has applied the EREP S-190 data to: (1) analysis of photolinear elements of the Powder River Basin, southern Montana, and the Wind River Mountains; (2) drainage analysis of the Powder River Basin and Beartooth Mountains; (3) lithologic and geologic mapping in the Powder River Basin, Black Hills, Green River Basin, Bighorn Basin and Southern Bighorn Mountains; (4) location of possible mineralization in the Absaroka Range; and (5) land use mapping near Riverton and Gillette. All of these applications were successful to some degree. Image enhancement procedures were useful in some efforts requiring distinction of small objects or subtle contrasts.

Houston, R. S.↗

ERTS-A data as a teaching and research tool in the Department of Geology

The author has identified the following significant results. ERTS-1 prints have been used extensively in a geology of Alaska class to give a basic framework of the geology of the state. In addition, they have been intermittantly used in such diverse classes as: (1) Economic Geology (e.g. the Sn-bearing granites of the Seward Peninsula are particularly noticeable due to their wide contact metamorphic aureoles.) (2) A canned geology of Alaska lecture which has been given to two different introductory geology courses. (3) Structural Geology (e.g. the Fairweather and Denali faults are striking obvious). It was found most convenient for larger classes to prepare 35mm slides of the ERTS-1 prints that are used in conjunction with slides of the topographic and geologic maps at about the same scale. Thus the emphasis has been in integration of the ERTS-1 material into existing courses. As such, the ERTS-1 data has provided a unique and striking viewpoint that never fails to initiate favorable comment. In addition, prints have been examined by numerous researchers to develop a regional, integrated overview of such varied topics as regional geology to a background for local geologic mapping to studies of ore deposits and to the definition of a formation to be studied in detail at its type locality.

Grybeck, D.↗

Geophysical models of Western Aphrodite-Niobe region: Venus

The new topography and gravitational field data for Venus expressed in spherical harmonics of degree and order up to 50 allow us to analyze the crust-mantle boundary relief and stress state of the Venusian lithosphere. In these models, we consider models in which convection is confined beneath a thick, buoyant lithosphere. We divide the convection regime into an upper mantle and lower mantle component. The lateral scales are smaller than on Earth. In these models, relative to Earth, convection is reflected in higher order terms of the gravitational field. On Venus geoid height and topography are highly correlated, although the topography appears to be largely compensated. We hypothesize that Venus topography for those wavelengths that correlate well with the geoid is partly compensated at the crust-mantle boundary, while for the others compensation may be distributed over the whole mantle. In turn the strong sensitivity of the stresses to parameters of the models of the external layers of Venus together with geological mapping allows us to begin investigations of the tectonics and geodynamics of the planet. For stress calculations we use a new technique of space- and time-dependent Green's response functions using Venus models with rheologically stratified lithosphere and mantle and a ductile lower crust. In the basic model of Venus the mean crust is 50-70 km thick, the density contrast across the crust-mantle boundary is in the range from 0.3 to 0.4 g/cm(exp -3). The thickness of a weak mantle zone may be from 350 to 1000 km. Strong sensitivity of calculated stress to various parameters of the layered model of Venus together with geological mapping and analysis of surface tectonic patterns allow us to investigate the tectonics and geodynamics of the planet. The results are presented in the form of maps of compression-extension and maximum shear stresses in the lithosphere and maps of crust-mantle boundary relief, which can be presented as a function of time. We have modeled the region of Western Aphrodite and the Niobe plains to get reasonable depths of compensation. Crust mantle boundary relief is calculated for Western Aphrodite-Niobe relative to a mean crustal thickness of 50 km. The calculations include the consequences of simple crust models and more complicated models with a weak, ductile lower crust, a strong upper mantle and a weak lower mantle layer.

Marchenkov, K. I.↗

Manual for 70 mm hand-held photography from Skylab

A manual and atlas used on the Skylab mission for hand-held photography are presented. The manual covers terrain, environmental, meteorological, and dim light photography while the atlas covers sections from the Army Map Service 1:40.000,000 world map, a glossary of geologic terms, geologic maps, and recommended exposure times.

Lowman, P. D., Jr.↗