Rim Rock Research Articles

Future changes in habitat availability for two specialist snake species in the imperiled rocklands of South Florida, USA

AbstractRockland habitat in South Florida, USA, is a threatened ecosystem that has been lost, fragmented, or degraded because of urbanization or other anthropogenic disturbance. Furthermore, low‐lying islands and coastal areas are experiencing sea level rise (SLR) and an increased frequency and intensity of tidal flooding, putting rockland habitats there at increasing risk of ecological change. We evaluated changes in the extent of rockland habitat under various scenarios of future SLR, tidal flooding, and human development for two endemic state‐listed threatened species of snakes, the Rim Rock Crowned Snake (Tantilla oolitica) and the Key Ring‐necked Snake (Diadophis punctatus acricus). Both snakes are restricted to South Florida. We used recent and historical species' records to determine each species' habitat range. We then estimated the extent of future habitat loss due to SLR and continued human development, as well as degradation of the remaining habitat. We also asked whether the future potential drivers of habitat loss and degradation differ between the two species and across their habitat ranges. We predicted that saltwater intrusion could negatively affect rocklands by 2050, resulting in degradation of 80% of the existing habitat because of an anticipated 42 cm of SLR. Moreover, our model suggests short‐term stochastic events such as storm surge and high tides may increasingly saturate the root zone of rockland vegetation before complete inundation. Under the extreme scenario, we predict most of the rockland habitat used by these two species of snakes may be inundated by 2080. Under the extreme SLR scenario, current rocklands are likely to convert to more halophytic habitat (mangrove or salt marsh wetland) within 50–60 years. Under the low scenario, 31% of rockland habitat may be lost due to human development by 2030. Therefore, mitigation actions may help to conserve specialist species within rockland habitat threatened by human activities and climate change.

Degradation of Endeavour Crater Based on Orbital and Rover‐Based Observations in Combination With Landscape Evolution Modeling

AbstractExploration of Endeavour crater's Shoemaker formation rim rocks by the Opportunity rover, combined with extensive observations from the Mars Express and Mars Reconnaissance Orbiters, provides unique and quantitative insights into the processes that have degraded this 22‐km diameter Noachian age impact crater. These insights are informed by comparisons between Endeavour and the relatively young, and morphologically fresh appearing, 19‐km diameter Bopolu crater located 65 km to the southwest. Analyses of rover and orbiter data, combined with landscape evolution modeling using Bopolu topography as a starting point, demonstrate that significant weathering and fluvial degradation of Endeavour occurred during the Noachian Period, with ~0.3 km of vertical rim removal, ~0.9‐km backwasting of the rim, and deposition of ~0.5 km of fluvial‐deltaic‐lacustrine sediments on the crater floor, sourced from rim erosion. Pediments formed on external rim segments, with characteristic thin regolith covers over graded bedrock. Late Noachian to Early Hesperian age Grasberg formation draping sediments, and Burns formation sulfate‐rich sandstones, subsequently embayed all but high standing Shoemaker formation rocks. Burns formation strata accumulated in the crater interior up to a depth of ~0.8 km. Subsequent wind erosion of the interior deposits is indicated by an interior mound and moat, together with yardangs carved into Shoemaker formation rocks, and graded topographic profiles from Grasberg and Burns formation rocks up and through the interior rim Shoemaker formation outcrops. Up to ~0.4 km of Burns formation rocks were exhumed from within the crater by wind erosion to produce the mound and moat.

Three tier transition of Neoarchean TTG-sanukitoid magmatism in the Beit Bridge Complex, Southern Africa

Neoarchean TTG-sanukitoid associations of contrasting scales occur within the Beit Bridge Complex terrane of the Limpopo Complex in southern Africa. These include the smaller ~2.65–2.63Ga Avoca granitoid and the voluminous ~2.73–2.64Ga Alldays granitoid. This study characterizes the wide compositional spectrum preserved in these two granitoids. The elliptical Avoca pluton consists of a biotite-amphibole-orthopyroxene±clinopyroxene-bearing core that is dominantly trondhjemite with less dominant tonalite and granodiorite variants, and a thin amphibole-biotite-bearing granite rim, with local occurrence of two-pyroxene-bearing metabasite boudins. While both the core and rim rocks exhibit a linear fabric, the granite in addition preserves a penetrative foliation. Field relations of granite enclaves in the core rocks together with available ages indicate that the core rocks intruded the granite. The foliated biotite±amphibole-bearing Alldays granitoid contains inclusions of older supracrustals and rocks of the Messina layered intrusion, and is widely distributed. Compositionally, it include tonalites and granodiorites and to a lesser extent trondhjemites. Both the Avoca core and rim rocks are characterized by difference in mineral chemistry, with the mafic minerals Mg-rich in the TTG core, while they are Fe-rich in the granite and metabasite. In comparison, biotite is Mg-rich and amphibole is Fe-rich in the Alldays granitoid.Two groups of Alldays TTG can be delineated in terms of whole-rock geochemical characteristics, and are comparable to the low- to medium-pressure TTG groups delineated by Moyen (2011), while the Avoca TTG is similar to the high-pressure TTG group. The lowest silica samples from each group of granitoid have geochemical characteristics comparable to Archean sanukitoids, with those from the Avoca granitoid similar to low-Ti sanukitoids, and those from the Alldays granitoid similar to low-Ti and high-Ti sanukitoids. Separate petrogenetic models are suggested for different phases of the Avoca core, with the trondhjemite-tonalites considered as high-pressure melts of metabasalt, while the granodiorite with lower SiO2 content, higher K2O and MgO contents, and higher incompatible element contents, than the trondhjemite-tonalites, is a product of hybridization of earlier TTG melts and peridodite. Granite from the Avoca rim are low-pressure melts of pre-existing crustal lithologies. The two groups of Alldays TTG with lower Sr/Y ratios than the Avoca TTG are considered as low- to medium-pressure melts of metabasalt, whose progressive interaction with peridotitic mantle at shallower angles account for the unique composition of Alldays low-Ti and high-Ti sanukitoids. Taken together with their spatial and temporal transition from southeastern (~2.73–2.72Ga; low-pressure TTG-low-Ti sanukitoid) to central (~2.65–2.64Ga; medium-pressure TTG-high-Ti sanukitoid) to northwestern (~2.63Ga; high-pressure TTG-low-Ti sanukitoid) parts of the Beit Bridge Complex, the three tier transition of TTG-sanukitoid magmatism argues for the southern margin of the Beit Bridge Complex to represent an active arc in the Neoarchean.

Basement control of alkalic flood rhyolite magmatism of the Davis Mountains volcanic field, Trans-Pecos Texas, U.S.A.

Voluminous silicic lava flows, erupted ~37.4Ma from widespread centers within the Davis Mountains Volcanic Field (DMVF), covered approximately 10,000km2 with an initial volume as great as 1000km3. Lava flows form three major stratigraphic units: the Star Mountain Rhyolite (minimum 220km3) of the eastern Davis Mountains and adjacent Barilla Mountains, the Crossen Formation (~75km3) of the southern Davis Mountains, and the Bracks Rhyolite (~75km3) of the Rim Rock region west of the Davis Mountains proper. Similar extensive rhyolite lava also occurs in slightly younger units (Adobe Canyon Rhyolite, ~125km3, 37.1Ma), Sheep Pasture Formation (~125km3, ~36Ma) and, less voluminously, in the Paisano central volcano (~36.9Ma) and younger units in the Davis Mountains. Individual lava flows from these units formed fields as extensive as 55km and 300-m-thick.Flood rhyolite lavas of the Davis Mountains are marginally peralkaline quartz trachyte to low-silica rhyolite. Phenocrysts include alkali feldspar, clinopyroxene, FeTi oxides, and apatite, and, rarely, fayalite, as well as zircon in less peralkaline units. Many Star Mountain flows may be assigned to one of four geochemical groupings. Temperatures were moderately high, ranging from ~911 to 860°C in quartz trachyte and low silica rhyolite. We suggest that flood rhyolite magma evolved from trachyte magma by filter pressing processes, and trachyte from mafic magma in deeper seated plutons.The Davis Mountains segment of Trans-Pecos Texas overlies Grenville basement and is separated from the older Southern Granite and Rhyolite Province to the north by the Grenville Front, and from the younger Coahuila terrane to the south by the Ouachita Front. We suggest that basement structure strongly influenced the timing and nature of Trans-Pecos magmatism, probably in varying degrees of impeding the ascent of mantle-derived mafic magmas, which were produced by upwelling of asthenospheric mantle above the foundered Farallon slab. Basalt was able to penetrate Coahuila crust in the Big Bend region. Thicker Grenville crust under the Davis Mountains retarded ascent of mafic magmas, allowing mafic plutons to differentiate into silicic magma that was eventually erupted as flood lava. North of the Grenville Front, magmatism was further delayed and thicker, older crust there may have helped concentrate magmatism under the Davis Mountain region. Only after the onset of Basin and Range faulting was true basalt erupted over much of the Trans Pecos.

Proposing 3SEMCS- Three Step Encryption Method for Cyber Security in Modern Cryptography

Cyber security is a critical issue now a days in various different domains in different disciplines. This paper presents a review analysis of cyber hacking attacks along with its experimental results and proposes a new methodology 3SEMCS named as three step encryption method for cyber security. By utilizing this new designed methodology, security at highest level will be easily provided especially on the time of request submission in the search engine as like google during client server communication. During its working a group of separate encryption algorithms are used. The benefit to utilize this three step encryption is to provide more tighten security by applying three separate encryption algorithms in each phase having different operations. And the additional benefit to utilize this methodology is to run over new designed private browser named as “RR” that is termed as Rim Rocks correspondingly this also help to check the authenticated sites or phishing sites by utilizing the strategy of passing URL address from phishing tank. This may help to block the phisher sites and user will relocate on previous page. The purpose to design this personnel browser is to enhance the level of security by sign_in on the time of client server communication that correspondingly reduce the normal attacks on browser based attacks as like ManIn-The-Middle-Attack (MITMA). This new designed private browser may help to provide online security by applying 3step automatic encryption on path during request movement of google page from the one to the next or ultimately/towards web server by following auto-generated encrypted hash address approach. At end, this rim rocks browser provides tighten security with anti-phishing facility during client server communication.

Mars Science Laboratory Mission and Science Investigation

Scheduled to land in August of 2012, the Mars Science Laboratory (MSL) Mission was initiated to explore the habitability of Mars. This includes both modern environments as well as ancient environments recorded by the stratigraphic rock record preserved at the Gale crater landing site. The Curiosity rover has a designed lifetime of at least one Mars year (∼23 months), and drive capability of at least 20 km. Curiosity’s science payload was specifically assembled to assess habitability and includes a gas chromatograph-mass spectrometer and gas analyzer that will search for organic carbon in rocks, regolith fines, and the atmosphere (SAM instrument); an x-ray diffractometer that will determine mineralogical diversity (CheMin instrument); focusable cameras that can image landscapes and rock/regolith textures in natural color (MAHLI, MARDI, and Mastcam instruments); an alpha-particle x-ray spectrometer for in situ determination of rock and soil chemistry (APXS instrument); a laser-induced breakdown spectrometer to remotely sense the chemical composition of rocks and minerals (ChemCam instrument); an active neutron spectrometer designed to search for water in rocks/regolith (DAN instrument); a weather station to measure modern-day environmental variables (REMS instrument); and a sensor designed for continuous monitoring of background solar and cosmic radiation (RAD instrument). The various payload elements will work together to detect and study potential sampling targets with remote and in situ measurements; to acquire samples of rock, soil, and atmosphere and analyze them in onboard analytical instruments; and to observe the environment around the rover. The 155-km diameter Gale crater was chosen as Curiosity’s field site based on several attributes: an interior mountain of ancient flat-lying strata extending almost 5 km above the elevation of the landing site; the lower few hundred meters of the mountain show a progression with relative age from clay-bearing to sulfate-bearing strata, separated by an unconformity from overlying likely anhydrous strata; the landing ellipse is characterized by a mixture of alluvial fan and high thermal inertia/high albedo stratified deposits; and a number of stratigraphically/geomorphically distinct fluvial features. Samples of the crater wall and rim rock, and more recent to currently active surface materials also may be studied. Gale has a well-defined regional context and strong evidence for a progression through multiple potentially habitable environments. These environments are represented by a stratigraphic record of extraordinary extent, and insure preservation of a rich record of the environmental history of early Mars. The interior mountain of Gale Crater has been informally designated at Mount Sharp, in honor of the pioneering planetary scientist Robert Sharp. The major subsystems of the MSL Project consist of a single rover (with science payload), a Multi-Mission Radioisotope Thermoelectric Generator, an Earth-Mars cruise stage, an entry, descent, and landing system, a launch vehicle, and the mission operations and ground data systems. The primary communication path for downlink is relay through the Mars Reconnaissance Orbiter. The primary path for uplink to the rover is Direct-from-Earth. The secondary paths for downlink are Direct-to-Earth and relay through the Mars Odyssey orbiter. Curiosity is a scaled version of the 6-wheel drive, 4-wheel steering, rocker bogie system from the Mars Exploration Rovers (MER) Spirit and Opportunity and the Mars Pathfinder Sojourner. Like Spirit and Opportunity, Curiosity offers three primary modes of navigation: blind-drive, visual odometry, and visual odometry with hazard avoidance. Creation of terrain maps based on HiRISE (High Resolution Imaging Science Experiment) and other remote sensing data were used to conduct simulated driving with Curiosity in these various modes, and allowed selection of the Gale crater landing site which requires climbing the base of a mountain to achieve its primary science goals. The Sample Acquisition, Processing, and Handling (SA/SPaH) subsystem is responsible for the acquisition of rock and soil samples from the Martian surface and the processing of these samples into fine particles that are then distributed to the analytical science instruments. The SA/SPaH subsystem is also responsible for the placement of the two contact instruments (APXS, MAHLI) on rock and soil targets. SA/SPaH consists of a robotic arm and turret-mounted devices on the end of the arm, which include a drill, brush, soil scoop, sample processing device, and the mechanical and electrical interfaces to the two contact science instruments. SA/SPaH also includes drill bit boxes, the organic check material, and an observation tray, which are all mounted on the front of the rover, and inlet cover mechanisms that are placed over the SAM and CheMin solid sample inlet tubes on the rover top deck.

Impact of the deeper geological basement on soil gas and indoor radon concentrations in areas of Quaternary fluvial sediments (Bohemian Massif, Czech Republic)

The relationship of soil gas radon Rn222 and indoor radon was studied within the Quaternary fluvial sediments of the Czech Republic. The processing of data selection from the radon database of the Czech Geological Survey and indoor radon data (database of the National Radiation Protection institute) has proved the concentration dependence of radon in Quaternary fluvial sediments on deeper bedrock. The ArcGIS processing was accompanied by the field verification in five profiles, intersecting the granitoid Central Bohemian Plutonic Complex and its rim rock types. Both theoretical and experimental results show dependence of soil gas radon and indoor radon concentrations in Quaternary fluvial sediments on deeper geological basement, thus leading to the conclusion that the lateral transport of Quaternary sediments does not play such a dominant role in radon concentrations, as was thought previously. This fact will enable to determine precisely the radon index of Quaternary sediments (in the Czech radon mapping classified as an intermediate index) into three categories according to the lithology of their geological basement.

Identification of the Bloody Creek structure, a possible impact crater in southwestern Nova Scotia, Canada

Abstract— An approximately 0.4 km diameter elliptical structure formed in Devonian granite in southwestern Nova Scotia, herein named the Bloody Creek structure (BCS), is identified as a possible impact crater. Evidence for an impact origin is based on integrated geomorphic, geophysical, and petrographic data. A near‐continuous geomorphic rim and a 10 m deep crater that is infilled with lacustrine sediments and peat define the BCS. Ground penetrating radar shows that the crater has a depressed inner floor that is sharply ringed by a 1 m high buried scarp. Heterogeneous material under the floor, interpreted as deposits from collapse of the transient cavity walls, is overlain by stratified and faulted lacustrine and wetland sediments.Alteration features found only in rim rocks include common grain comminution, polymict lithic microbreccias, kink‐banded feldspar and biotite, single and multiple sets of closely spaced planar microstructures (PMs) in quartz and feldspar, and quartz mosaicism, rare reduced mineral birefringence, and chlorite showing plastic deformation and flow microtextures. Based on their form and crystallographic orientations, the quartz PMs consist of planar deformation features that document shock‐metamorphic pressures ≤25 GPa.The age of the BCS is not determined. The low depth to diameter ratio of the crater, coupled with anomalously high shock‐metamorphic pressures recorded at its exposed rim, may be a result of significant post‐impact erosion. Alternatively, impact onto glacier ice during the waning stages of Wisconsinian deglaciation (about 12 ka BP) may have resulted in dissipation of much impact energy into the ice, resulting in the present morphology of the BCS.

Rare metal mineralization at the Salpeterkop carbonatite complex, Western Cape Province, South Africa

The Salpeterkop complex is an eroded central volcano of Late Cretaceous (66 Ma) age with a sediment-filled crater remnant 1 km in diameter associated with radial and concentric carbonatite/K-trachyte dykes as well as K-trachyte, breccia and olivine melilitite plugs. The sedimentary country rocks have been domed. Geochemical anomalies for Ti, Y, Zr, Nb, Th, V, Zn and Mo, based on a core-drilling programme, were found to outline a mineralized zone coinciding with the crater rim, especially on the western and southern sides. The rim rocks are volcanic breccias intimately mixed and veined by decomposed, silicified and ferruginized carbonatite and carbonatitic tuff. A large variety of very fine-grained minerals have been identified in a groundmass consisting mainly of goethite and chalcedony. The principal Nb ore mineral is niobian brookite occurring as microscopic disseminated grains of several morphological types. High-Nb (12% Nb 2O 5) and low-Nb (8% Nb 2O 5) brookites have been distinguished. Some of them contain inclusions of ilmenorutile. Delicate brookite crystal aggregates crystallized in situ. No discrete V and Zn minerals could be identified but Th occurs as thorianite and thorite, Zr occurs in eudialyte and an unidentified KNb silicate and Y occurs as xenotime. Nepheline and eudialyte are probably xenocrysts from an unexposed body of nepheline syenite. It is concluded that mineralization took place in three overlapping stages: 1. i)primary magmatic, with concentration of Nb, Zr, Th, V in both carbonatite and associated silicate rocks; 2. ii)mesothermal, with oxidation and introduction of Fe, Ti, REE, Mo and F; 3. iii)epithermal, with hydration and dissolution of carbonates, removal of Ca and Mg, redistribution of Y, Ti, Nb, Zn and deposition of Si, Ba, Mn and other mobile elements. The suggestion is made that the preservation and extent of the third stage, which may be linked to fumarolic activity, distinguishes the multi-element mineralization at Salpeterkop from other carbonatite complexes. Secondary alteration in the weathered zone merged with the third stage, but is less important.

Geologic Controls of In-Situ Processing of Tar Sands, N.W. Asphalt Ridge, Utah: ABSTRACT

End_Page 630------------------------------The Laramie Energy Technology Center completed three in-situ oil-recovery experiments from tar sands at N.W. Asphalt Ridge, Utah. The 10-acre (4 ha.) tract is part of the Sohio Shale Oil Co. D tract located west of Vernal, in Uintah County. Asphalt Ridge, lying on the northern boundary of the Uinta basin, is a northwest-southeast-trending ridge. The area on the northwest is structurally a monocline dipping southwest. The 3.28 to 14.75 m thick experimental tar-sand zones are in the Rim Rock Sandstone Member of the Mesaverde Formation of Cretaceous age. The beds dip 28°SW, and overburden thicknesses range from 89 to 164 m. Two known faults, with throws up to 66 m, bound the tract. Three experiments were performed at the tract on varying partial acreages from 1975 to 1980. Two combustion tests using reverse combustion and a combination reverse and forward combustion were completed in a tar-sand bed 3.28 to 3.93 m thick. Recovered oil and water for the experiments ranged from 65 to 580 bbl and 167 to 600 bbl, respectively. The third test used steam injection on a 14.75 m thick bed. Production was 1,150 bbl of oil and 6,250 bbl of water. Tar-sand analyses yielded the following range of data for the three tests: extracted porosity, 26.1 to 31.1%; absolute air permeability, 651 to 2,175 md; oil saturation, 62 to 75% pore volume; water saturation, 2.4 to 7.9% pore volume. Various geologic controls can determine the effectiveness of the extraction process. These inclu e the dip of the beds, reservoir thickness, water and oil saturation, porosity, permeability, vertical and horizontal continuity of section, confinement of zone, and potential fractures and faulting in area. End_of_Article - Last_Page 631------------

Morphology of Lonar Crater, India: Comparisons and implications

Lonar Crater is a young meteorite impact crater emplaced in Deccan basalt. Data from 5 drillholes, a gravity network, and field mapping are used to reconstruct its original dimensions, delineate the nature of the pre-impact target rocks, and interpret the emplacement mode of the ejecta. Our estimates of the pre-erosion dimensions are: average diameter of 1710 m; average rim height of 40 m (30–35 m of rim rock uplift, 5–10 m of ejected debris); depth of 230–245 m (from rim crest to crater floor). The crater's circularity index is 0.9 and is unlikely to have been lower in the past. There are minor irregularities in the original crater floor (present sediment-breccia boundary) possibly due to incipient rebound effects. A continuous ejecta blanket extends an average of 1410 m beyond the pre-erosion rim crest. In general, ‘fresh’ terrestrial craters, less than 10 km in diameter, have smaller depth/diameter and larger rim height/diameter ratios than their lunar counterparts. Both ratios are intermediate for Mercurian craters, suggesting that crater shape is gravity dependent, all else being equal. Lonar demonstrates that all else is not always equal. Its depth/diameter ratio is normal but, because of less rim rock uplift, its rim height/diameter ratio is much smaller than both ‘fresh’ terrestrial and lunar impact craters. The target rock column at Lonar consists of one or more layers of weathered, soft basalt capped by fresh, dense flows. Plastic deformation and/or compaction of this lower, incompetent material probably absorbed much of the energy normally available in the cratering process for rim rock uplift. A variety of features within the ejecta blanket and the immediately underlying substrate, plus the broad extent of the blanket boundaries, suggest that a fluidized debris surge was the dominant mechanism of ejecta transportation and deposition at Lonar. In these aspects, Lonar should be a good analog for the ‘fluidized craters’ of Mars.

Discussion on the Flinders Range breccias of S Australia—diapirs or décollement?

D rs C. R. D algarno & R. P. C oats write: We disagree with the hypothesis presented by Burns et al. (1977) for the origin of the breccias of the Blinman Dome and other Flinders Ranges structures. Uplift and erosion of breccia cores occurred during deposition of the rim rocks, as indicated by marginal upturning with local unconformities and onlapping conglomerates. This is associated with stratigraphic thinning on the flanks of structures during late Precambrian (Sturtian) and Lower Cambrian sedimentation. Burns et al. suggested that the conglomerates within the rim sediments ‘may have been emplaced by mass movement from topographic highs composed of Willouran rocks’, although they do not envisage origin of the (Blinman) domes until the late Cambrian orogeny when they describe a ‘brecciation front which simply migrated upwards through the Callanna Beds and overlying Sturtian tillite’. This concept is considered by them to explain blocks of basement granite within the breccias as derived in situ from Sturtian tillites containing erratics. Our alternative suggestion is that the granites have been plucked off the basement by diapirs. The Geological Survey considers that the diapir model applies to the whole province in which cross sectional views of some structures are afforded by steep dips. Burns et al. also suggested that the breccias are flat plates or tabular rafts, and that the features are similar to those found in sedimentary breccias caused by gravitational sliding. These characters do not apply to the breccias described by Coats (1964) and Dalgarno & Johnson (1968), which are related

Field Test of Reverse-Combustion Oil Recovery From A Utah Tar Sand

Abstract A field experiment to recover oil from tar sand by reverse combustion was conducted at Northwest Asphalt Ridge, near Vernal, Utah. This test was in a 10-foot interval of the Rim Rock sandstone member of the Mesa Verde Formation at a depth of approximately 300 feet. Ignition was accomplished on November 25, 1975, and the reverse combustion front was propagated successfully through the formation. Results of the field experiment differed significantly from the -results of laboratory tests that were used in the design of the field test. This difference is attributed primarily to the extreme heterogeneity of the tar sand formation. Observed temperatures in the burned area were lower than expected, but a large portion of the tar sand within the pattern boundaries was heated to the extent that the bitumen became mobile enough to be produced. After 31/2 weeks of operation, the project was terminated because of the inability of the surface production equipment to accommodate the heavy hydrocarbons being produced. Although the formation of the cracked products of reverse combustion was less than expected, this recovery process may be used successfully to heat the tar sand reservoir to a temperahl.re high enough that the bitumen become mobile enough to be produced. Introduction THE RECOVERY of oil from tar sands in the United States has received only limited interest in the past. Recently, oil price increases and the decline of domestic oil reserves have made this source of energy more attractive. Deposits of tar sand are widely distributed throughout the U.S., but the most significant tar sand deposits are in the state of Utah. An efficient means of recovering oil from tar sands could increase the hydrocarbon reserves of this country by billions of barrels. One area of research within the Laramie Energy Research Center of ERDA is devoted to development of methods for recovering oil from tar sands. 1nsitu methods are of primary consideration, because only a small portion of the tar sand resource is thought to be mineable, and because of environmental concern. After a laboratory study using Utah tar sands(1), the reverse-combustion oil recovery processwas selected for further investigation in a field test. The reverse-combustion process was designed to recover oil from formations containing very viscousor semi-solid hydrocarbons(2). This method differs from forward combustion in that the combustion front travels in the direction opposite to the direction of air flow. An advantage of the reverse-combustion method is that the hydrocarbons flow with the combustion gasses through the hot region of the reservoir. In forward combustion, hot mobile oil can flow into the cooler region ahead of the front where it can congeal, plugging the formation to further flow. Another attractive feature of reverse combustion is that the original bitumen is cracked into a lighter oil as the combustion front passes through the formation. This oil remains in the vapour state while passing through the hot, previously burned zone.

Petrology of Volcanic Sedimentary Rocks, Vieja Group, Southern Rim Rock Country, Trans-Pecos Texas

ABSTRACT Primary mineral facies, depositional facies, and diagenetic assemblage zones can be mapped in the Vieja Group (Eocene-Oligocene). Variations of primary mineralogy can be ascribed to both source and environmental effects. By recognizing those attributable to source effects, and by consideration of the depositional environments present, the sequence of eruption of volcanos and the nature of their activity can he deduced. When they were deposited, volcanic-sedimentary rocks of the Vieja Group were composed mostly of three types of volcano-derived detrital constituents: glass shards and pumice fragments, volcanic rock fragments (VRF's), and monocrystalline mineral grains. Crystal fragments were most abundant in medium sandstones, glass fragments predominated in finer grained rocks and VRF's predominated in coarse sandstones and conglomerates. The actual abundance of any type of constituent was also a function of the abundance in which it was provided by the various volcanic sources and of the environment of deposition of the sediment. The volcano active during deposition of the Colmena formation provided abundant VRF's and plagioclase. One erupting during deposition of the Chambers formation produced de ris rich in sanidine and quartz. During deposition of the Capote Mountain formation, the Chinati Mountains-Pinto Canyon center produced abundant glass. The rocks were deposited on a bajada-like apron by streams or mudflows that flowed radially away from volcanic eruptive centers, or in valleys where streams flowed between eruptive centers to the north and south. The streams entered the Southern Rim Rock Country from the west and continued eastward across the Trans-Pecos volcanic field. Stream channel and overbank deposits, with common paleosoil features, make up the valley facies. Medium sandstones in the valley facies are enriched in crystals relative to those deposited on aprons, either because of sorting by depositional processes or selective abrasion of glass fragments during transportation. Non-volcanic constituents are present in minor amounts in most valley facies rocks. They are the predominant grain type only in the valley f cies part of the Colmena Formation. Detrital clay is present in valley facies rocks and in the mudflow deposits of the Colmena Formation. Some rocks are the result of deposition by aeolian processes.

ROTER KAMM: EVIDENCE FOR AN IMPACT ORIGIN

Roter Kamm, located in the Namib Desert of SW Africa, is an 8,000‐foot‐diameter crater developed essentially in Precambrian granitic rocks. Sand overburden is pervasive both inside ami outside the crater and the only significant rock exposures are high in the crater rim. In most cases these exposed rocks proved entirely normal when examined microscopically but two specimens were found which exhibited features compatible with, and suggestive of, shock pressures in the range of 50 to 100 kilobars. Both specimens are probably foreign to the rim environment and may represent remnants of ejecta from the crater formation. There is a strong negative residual gravity anomaly across the structure which reaches a maximum of −9.3 milligals. The size and shape of the anomaly are fully compatible with a meteorite impact structure of “normal” dimensions. It is more difficult to interpret the gravity data in terms of an explosive volcanic origin and neither is there any evidence of such an origin in the rim rock exposures. An impact origin for the crater is strongly suggested by all the evidence to date. Definitive evidence of shock metamorphism could perhaps be found by a further search for “exotic” rocks in the rim.

Age of Rim Rock Dike Swarm, Trans-Pecos, Texas

Potassium-argon dates for basaltic rocks from the Rim Rock dike swarm of Trans-Pecos Texas range from 18 to 23 m.y. Because these dikes are closely associated with major normal faults, they indicate the age of Basin-Range faulting in the region. Two sets of dikes are distinguishable not only by strike and petrology, but also by age. The older, basaltic and trachy-basaltic set and the younger, more alkalic set have average ages of 22.3 and 19.2 m.y., respectively. Extensive deuteric alteration has not modified significantly the K-Ar dates of the rocks.

Stratigraphic succession, potassium-argon dates, and vertebrate faunas, Vieja Group, Rim Rock country, Trans-Pecos, Texas

Potassium-argon dates from a superpositional succession of igneous and sedimentary rocks of the Vieja, Garren, and Buck Hill Groups are critically evaluated. Five new faunas of vertebrate fossils collected from the interbedded tuffs are named, and tentative faunal lists are given. Misidentification of fossil vertebrates in an earlier collection are corrected. Abandonment of a previously published K-Ar date of 33.1 m.y. is urged because of lack of stratigraphic and geographic data. An Eocene-Oligocene boundary based upon vertebrates seems to fall within the Duchesnean Age.

Chadron vertebrate fossils from below the Rim Rock of Presidio County, Texas

Chadron vertebrate fossils from below the Rim Rock of Presidio County, Texas

Geology of the Cretaceous of the Uinta Basin, Utah

The Cretaceous rocks of the Uinta Basin, Utah, are exposed along the south flank of the Uinta Mountain anticline and are overlain unconformably by Tertiary sediments throughout this area. The Dakota (?) sandstone of this paper disconformably overlies the Jurassic Morrison and is overlain conformably by the Mancos shale. It probably represents rocks of both Upper and Lower Cretaceous age. The Mancos shale, as mapped and studied, comprises only a lithologic unit since in the Vernal vicinity it is equivalent in age and stratigraphic position to the Mesaverde group sandstones of the Tabby Mountain region to the west. The Mancos is divided into the following members, all easily identified throughout the Basin: lower shale member, Aspen shale, middle shale member, Frontier sandstone, and upper shale member. The Mesaverde group refers only to a lithologic facies since at the west end of the area it is predominantly Niobrara in age, whereas at the east it is completely post-Niobrara. In the Vernal region it is divided into three members: the Asphalt Ridge sandstone, the Rim Rock sandstone, and the Williams Fork formation (contains more than type Williams Fork). The lower members of the Mesaverde group intertongue with the upper portion of the Mancos shale and wedge out toward the east. The name Currant Creek is proposed for a sequence of conglomerate beds unconformably overlying the Mesaverde group in the Tabby Mountain region. This new formation is tentatively referred to the Upper Cretaceous but it probably represents the transitional strata deposited from late Upper Cretaceous to Eocene during the early phases of the Laramide folding. The Uinta Basin is an asymmetrical syncline with its steep side along the flank of the Uinta Mountain anticline to the north from which numerous small noses and supplementary folds plunge southward. The Basin's structural history involves the following movements: local uplift in the west end in early Montana time; folding, progressively from west to east, during late Cretaceous to early Eocene; first uplift during post-Green River (Eocene)—pre-Uinta (Eocene); second uplift during post-Uinta (Eocene)—pre-Duchesne River (Oligocene); regional tilting in post-Duchesne River (Oligocene)—pre-Bishop (Miocene?); subsidence in post Bishop (Miocene?)—pre-Quaternary; continental uplift in late Tertiary or early Quaternary.

Structure of Turner Valley Gas and Oil Field, Alberta

Turner Valley is structurally probably the most complicated oil field in North America. It is a highly folded and faulted compound anticlinal overthrust sheet bordering the outer Foothills Belt of Alberta. It involves Paleozoic limestones, dolomites, and shales, Jurassic shale, and Cretaceous rocks. From the surface, the structure appears to be rather simple, with apparently uninterrupted east and west rim rocks of Belly River sandstone enclosing Colorado shale. The major overthrust fault, which underlies part or all of the structure, is of considerable magnitude and appears to be warped. A high-gravity naphtha is produced with large volumes of gas from a dolomitized zone in the Paleozoic limestone, whereas small amounts of high-gravity crude are obtained from Mesozoic sa dstones at shallower depths. No connate water has been encountered in either the limestone or the upper producing sands. The heavier oils are found in the youngest formations and show a progressive decrease in gravity with depth. This paper consists of a discussion of the salient structural features, including two structure-contour maps, seven cross sections, an abridged geologic column, production statistics, and several photographs.