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Sample records for colluvium

  1. Defining Colluvium and Alluvium: An Experiment to Discuss and Consolidate Perspectives

    NASA Astrophysics Data System (ADS)

    Miller, Bradley; Juilleret, Jérôme

    2016-04-01

    Describing Earth materials with a shared terminology facilitates international collaboration because it reduces misunderstandings about the connections being made between observations and interpretations. The terms colluvium and alluvium are widely used, but their meanings vary almost as widely. Definitions for these terms can include connections to different geomorphic processes, landscape positions, or hydrology. In soil science, colluvium can be particularly influential as it is recognized in some national classification systems (e.g. France, Germany) as diagnostic material for "Colluvisols." Clarifying the meaning and diagnostic criteria of colluvium versus alluvium is especially important today because some definitions connect colluvium directly to erosion processes that are wide-spread and enhanced by anthropogenic activities. For example, the German "kolluvium" is pronounced the same as colluvium, but describes deposits at the base of hillslopes produced by water and/or tillage erosion. This contrasts with the common North American definition of colluvium describing materials transported primarily by gravity (i.e. mass movement). This poster raises awareness of the issue by illustrating the variety of published definitions for both colluvium and alluvium. Then it asks viewers to engage in the conversation by completing a survey either on paper or later online. The viewers are also invited to join the discussion on the same question, posed on the ResearchGate website (https://www.researchgate.net/post/How_do_you_define_colluvium).

  2. The origin and its environmental significance of thick colluvium on the coast of Xiaolanyu Isle, Taiwan

    NASA Astrophysics Data System (ADS)

    Chyi, Shyh-Jeng; Jen, Chia-Hung; Ho, Lih-Der; Chen, Jia-Hong; Yen, Jiun-Yee; Liou, Ying-San; Chang, Chung-Pai; Lee, Chi-Yu; Lin, Jian-Wei; Yu, Neng-Ti; Yen, I.-Chin; Lu, Cheng-Hao

    2016-04-01

    The thick colluvium and a terrace are located at the northern and southern coast of Xiaolanyu Isle, Taiwan. Xiaolanyu Isle is the youngest volcanic island in the northern Luzon Arc, which lava was dated as 0.04 to 0.02 Ma. In its southern coast, the horizontal layers of sedimentary sequences are exposed on the 20-meter-high terrace scarp which mainly consisted of fine-grained, volcanic origin materials with soft-sediment deformation structures, which indicate the sediment layers are clarinetist origin. The sediment layers are extended to the hill of lava and covered by the thick colluvium in the southeast corner of the island. Six 14C samples collected from those sediment layers yield the dates between 1.0 ka and 1.3 ka. The results of our works show that the collapse of volcanic materials and the formation of dammed lake created the horizontal sediment layers near the edge of the exposed terrace scarp. The residual collapsed material near the eastern part of the south coast of Xiaolanyu Isle was the volcanic debris without clear layers, and the previous volcanic landform, which caused the colluvium and the nature dam was vanished. In the northern coast, the hill of lava in the northeast corner is also covered by a thick colluvium. There is an erosional surface near the bottom of the collapsed material with rounded pebbles of 1 meter diameter and coarse sand layer on the top. It should be the strath surface and sediments near the coast before the collapsing of colluvium. Five 14C samples of seashell, charcoal and coral were collected from the rounded bounder layer and the bottom of colluvium. The date of four seashell and charcoal samples were between 1.7 ka and 1.9 ka and the coral sample was about 2.7 ka. The results demonstrated that the volcano in the eastern Xiaolanyu Isle had been generated large landslides around 1.7 ka and 1.2 ka, which destroyed the volcanic landform. The main sliding bodies and dammed lake were destroyed afterwards. The coastal erosion

  3. Colluvium supply in humid regions limits the frequency of storm-triggered landslides

    PubMed Central

    Parker, Robert N.; Hales, Tristram C.; Mudd, Simon M.; Grieve, Stuart W. D.; Constantine, José A.

    2016-01-01

    Shallow landslides, triggered by extreme rainfall, are a significant hazard in mountainous landscapes. The hazard posed by shallow landslides depends on the availability and strength of colluvial material in landslide source areas and the frequency and intensity of extreme rainfall events. Here we investigate how the time taken to accumulate colluvium affects landslide triggering rate in the Southern Appalachian Mountains, USA and how this may affect future landslide hazards. We calculated the failure potential of 283 hollows by comparing colluvium depths to the minimum (critical) soil depth required for landslide initiation in each hollow. Our data show that most hollow soil depths are close to their critical depth, with 62% of hollows having soils that are too thin to fail. Our results, supported by numerical modeling, reveal that landslide frequency in many humid landscapes may be insensitive to projected changes in the frequency of intense rainfall events. PMID:27688039

  4. Colluvium supply in humid regions limits the frequency of storm-triggered landslides

    NASA Astrophysics Data System (ADS)

    Parker, Robert N.; Hales, Tristram C.; Mudd, Simon M.; Grieve, Stuart W. D.; Constantine, José A.

    2016-09-01

    Shallow landslides, triggered by extreme rainfall, are a significant hazard in mountainous landscapes. The hazard posed by shallow landslides depends on the availability and strength of colluvial material in landslide source areas and the frequency and intensity of extreme rainfall events. Here we investigate how the time taken to accumulate colluvium affects landslide triggering rate in the Southern Appalachian Mountains, USA and how this may affect future landslide hazards. We calculated the failure potential of 283 hollows by comparing colluvium depths to the minimum (critical) soil depth required for landslide initiation in each hollow. Our data show that most hollow soil depths are close to their critical depth, with 62% of hollows having soils that are too thin to fail. Our results, supported by numerical modeling, reveal that landslide frequency in many humid landscapes may be insensitive to projected changes in the frequency of intense rainfall events.

  5. Colluvium supply in humid regions limits the frequency of storm-triggered landslides.

    PubMed

    Parker, Robert N; Hales, Tristram C; Mudd, Simon M; Grieve, Stuart W D; Constantine, José A

    2016-09-30

    Shallow landslides, triggered by extreme rainfall, are a significant hazard in mountainous landscapes. The hazard posed by shallow landslides depends on the availability and strength of colluvial material in landslide source areas and the frequency and intensity of extreme rainfall events. Here we investigate how the time taken to accumulate colluvium affects landslide triggering rate in the Southern Appalachian Mountains, USA and how this may affect future landslide hazards. We calculated the failure potential of 283 hollows by comparing colluvium depths to the minimum (critical) soil depth required for landslide initiation in each hollow. Our data show that most hollow soil depths are close to their critical depth, with 62% of hollows having soils that are too thin to fail. Our results, supported by numerical modeling, reveal that landslide frequency in many humid landscapes may be insensitive to projected changes in the frequency of intense rainfall events.

  6. Sedimentology, petrography and early diagenesis of a travertine-colluvium succession from Chusang (southern Tibet)

    NASA Astrophysics Data System (ADS)

    Wang, Zhijun; Meyer, Michael C.; Hoffmann, Dirk L.

    2016-08-01

    The Chusang travertine is situated in southern Tibet at an altitude of ~ 4200 m asl. in a cold-arid, periglacial environment and is characterized by interbedding of hydrothermal carbonate with colluvium. Here we present sedimentological and petrographical data to elucidate the depositional environment and sedimentary processes responsible for hydrothermal carbonate precipitation and early diagenetic alteration as well as clastic sediment accumulation and provide initial 230Th/U ages to constrain the time-depth of this travertine-colluvium succession. Three main travertine lithofacies have been identified: 1) a dense laminated lithofacies, 2) a porous layered lithofacies and 3) an intraclastic lithofacies that results from erosion of pre-existing hot spring carbonate. The colluvium is composed of cohesive debris flow layers that derived from mass-wasting events from the adjacent hillslopes. Micro-fabric analyses suggest that dense laminated travertine forms via rapid calcite precipitation from hot spring water seasonally subjected to severe winter cooling, while porous layered travertine results from seasonal dilution of hot spring water with rain water during the summer monsoon months, which in turn stimulates biological productivity and gives rise to a porous summer layer. Early diagenesis in the form of recrystallization and extensive formation of pore cements is common in the Chusang travertine, but never eradicates the original crystal fabrics completely. The sedimentary architecture of the deposit is conditioned by (i) the gently dipping (~ 10°) pre-existing terrain on which hot spring water is discharged from multiple travertine mounds causing laterally extensive travertine sheets to precipitate, and (ii) the adjacent much steeper (up to 30°) periglacial hillslopes that are the source area of repeated debris flows that accumulate on the travertine surface. The resulting travertine-colluvium succession has a total thickness of ~ 24 m and 230Th/U dating

  7. Thermoluminescence dating of fault-scarp-derived colluvium: Deciphering the timing of paleoearthquakes on the Weber segment of the Wasatch fault zone, north central Utah

    SciTech Connect

    Forman, S.L. ); Nelson, A.R. ); McCalpin J.P. )

    1991-01-10

    The timing of middle to late Holocene faulting on the Weber segment of the Wasatch fault zone, Utah, is constrained by thermoluminescence (TL) and radiocarbon age estimates on fine-grained, fault-related colluvial sediments. The stratigraphy in two trenches excavated across fault scarps is characterized by a stack of three colluvial wedges, deposited in response to three separate faulting events, the oldest of which buried a soil developed on a middle Holocene debris flow. Thermoluminescence age estimates by the partial and total bleach methods and the regeneration method on fine-grained colluvium from the trenches agree within 1 sigma and are concordant with the radiocarbon chronology. A synthesis of the TL and {sup 14}C age estimates indicate that these three faulting events occurred sometime between 4,500 and 3,500, between 3,200 and 2,500, and between 1,400 and 1,000 years ago. Detailed investigation of a sequence of fine-grained, scarp-derived distal colluvium shows that much of the sediment was deposited during <600-year intervals immediately after faulting. The sedimentation rate of colluvium is inferred to increase shortly after faulting, and TL dating of these sediments provides additional information to constrain the timing of faulting events.

  8. Characteristics of ground motion and threshold values for colluvium slope displacement induced by heavy rainfall: a case study in northern Taiwan

    NASA Astrophysics Data System (ADS)

    Jeng, Ching-Jiang; Sue, Dar-Zen

    2016-06-01

    The Huafan University campus is located in the Ta-lun Shan area in northern Taiwan, which is characterized by a dip slope covered by colluvium soil of various depths. For slope disaster prevention, a monitoring system was constructed that consisted of inclinometers, tiltmeters, crack gages, groundwater level observation wells, settlement and displacement observation marks, rebar strain gages, concrete strain gages, and rain gages. The monitoring data derived from hundreds of settlement and displacement observation marks were analyzed and compared with the displacement recorded by inclinometers. The analysis results revealed that the maximum settlement and displacement were concentrated on the areas around the Hui-Tsui, Zhi-An, and Wu-Ming buildings and coincided with periods of heavy rainfall. The computer program STABL was applied for slope stability analysis and modeling of slope failure. For prevention of slope instability, a drainage system and tieback anchors with additional stability measures were proposed to discharge excess groundwater following rainfall. Finally, threshold value curves of rainfall based on slope displacement were proposed. The curves can be applied for predicting slope stability when typhoons are expected to bring heavy rainfall and should be significant in slope disaster prevention.

  9. Hydrogeology and simulation of source areas of water to production wells in a colluvium-mantled carbonate-bedrock aquifer near Shippensburg, Cumberland and Franklin Counties, Pennsylvania

    USGS Publications Warehouse

    Lindsey, Bruce D.

    2005-01-01

    This report presents the results of a study by the U.S. Geological Survey in cooperation with the Shippensburg Borough Authority to evaluate the source areas of water to production wells in a colluvium-mantled carbonate-bedrock aquifer in Cumberland and Franklin Counties, Pa. The areal extent of the zone of contribution was simulated for three production wells near Shippensburg, Pa. by use of a ground-water-flow model. A 111-square-mile area was selected as the model area and includes areas of the South Mountain Section and the Great Valley Section of the Valley and Ridge Physiographic Province. Within the model area, the geologic units in the South Mountain area are predominantly metamorphic rocks and the geologic units in the Great Valley are predominantly carbonate rocks. Hydrologic and geologic information were compiled to establish a conceptual model of ground-water flow. Characteristics of aquifer materials were determined, and streamflow and water levels were measured. Streamflow measurements in November 2003 showed all streams lost water as they flowed from South Mountain over the colluvium-mantled carbonate aquifer into the Great Valley. Some streams lost more than 1 cubic foot per second to the aquifer in this area. The Shippensburg Borough Authority owns three production wells in the model area. Two wells, Cu 969 and Fr 823, are currently (2004) used as production wells and produce 500,000 and 800,000 gallons per day, respectively. Well Cu 970 is intended to be brought on line as a production well in the future. Water levels were measured in 43 wells to use for model calibration. Water-level fluctuations and geophysical logs indicated confined conditions in well Cu 970. Ground-water flow was simulated with a model that consisted of two vertical layers, with five zones in each layer. The units were hydrostratigraphic units that initially were based on geologic formations, but boundaries were adjusted during model calibration. Model calibration resulted in

  10. Landslide initiation in saprolite and colluvium in southern Brazil: Field and laboratory observations

    NASA Astrophysics Data System (ADS)

    Lacerda, Willy A.

    2007-06-01

    The weathering of granitic and gneissic rocks in tropical regions can reach depths of more than 100 m. In southeast Brazil there are situations where landslide initiation depends on the fluctuation of the groundwater level, on the impact of falling rocks and on intense rainfall, causing superficial slides. The fluctuation of groundwater induces cyclical variations of the pore water pressure, and consequently of the effective stresses. This variation causes cyclic expansion and contraction of the structure of the saprolitic soil, weakening the imbrication of grains and loss of the cementation that may exist. This could be called a "fatigue" phenomenon. The practical effect is the lowering of the Mohr shear strength envelope, and a sudden rupture of the soil at a lower groundwater level than that which would be compatible with the intact soil strength properties, initiating a landslide. Another situation arises during intense rains, when a rock slab or a rock block detaches from the uppermost parts of a slope. This occurs where steep rock outcrops exhibit relief joints or where residual blocks of granite roll down the slope, impacting the compressible, saturated colluvial soil overlying the saprolitic soil. The sudden increase of pore pressure can liquefy the soil. Finally, another mechanism is that of the advance of a saturation front in a steep slope of unsaturated saprolitic soil, reaching a depth below the root zone. The loss of the cohesion due to suction, without the beneficial contribution of the roots to the shearing strength, causes a sudden slide. During extreme rain episodes literally hundreds of such superficial slides, reaching 1 to 3 m in depth, occur in a given basin. The concentrated runoff that flows along the surface of the thalweg of the basin carries this soil in a muddy state, and a debris flow ensues.

  11. Pedogenesis of black shale-influenced soils of the Knobs region of eastern Kentucky

    SciTech Connect

    Sobecki, T.M.

    1989-01-01

    Investigation of acid soils on forested hillslopes truncating Devonian-age black shales in the Knobs of eastern Kentucky established the impact of parent material and landscape position on colluvium occurrence and soil properties. Colluvium was thickest in headslopes, thinner in nose- and sideslopes, where illitic Typic Hapludults formed in acid gray and black shale residuum and colluvium, and sandstone colluvium. Base saturation and pH increased with depth in nose- and sideslopes, and decreased with depth in headslopes. The pH of black shale colluvium and residuum was {lt}4.0 in noseslopes, and Al saturation {gt}90%. Morphology, particle size, and TiO{sub 2}/ZrO{sub 2} ratios were used to assess parent material homogeneity and colluvium source. Compositions of soil solutions, mineral stability, and clay mineral analyses were used to evaluate illite weathering. Smectite randomly interstratified with illite was an initial illite weathering product in the noseslope black shale soil. High charge smectite (HCS), randomly interstratified with illite, predominated in noseslope pedons of black and gray shale, however. Vermiculite occurred in black and gray shale headslope pedons. Lithologic discontinuities prevented attribution of clay mineral suites solely to weathering. Soil solution compositions, clay mineral ratios, and thermodynamic stability of the clay minerals, however, suggested a weathering sequence of illite {yields} smectite {yields} HCS or vermiculite {yields} kaolinite or complete dissolution. Column leaching experiments suggested carbon, iron, and sulfur loss as the initial black shale weathering step, with silicate alteration following at a later stage. Young landscapes coupled with the loss of soluble weathering products from these soils is suggested as an explanation for the maintenance of illitic mineralogy despite undersaturation with respect to illite.

  12. 43 CFR 3832.21 - How do I locate a lode or placer mining claim?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...) or is not a deposit of placer, alluvial (deposited by water), eluvial (deposited by wind), colluvial... shaft, or running a tunnel or drift to a sufficient depth. (b) Placer claims. (1) Your placer claim is... (deposited by wind), colluvium (deposited by gravity), talus, or other rock not in its original place;...

  13. 43 CFR 3832.21 - How do I locate a lode or placer mining claim?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ...) or is not a deposit of placer, alluvial (deposited by water), eluvial (deposited by wind), colluvial... shaft, or running a tunnel or drift to a sufficient depth. (b) Placer claims. (1) Your placer claim is... (deposited by wind), colluvium (deposited by gravity), talus, or other rock not in its original place;...

  14. 43 CFR 3832.21 - How do I locate a lode or placer mining claim?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...) or is not a deposit of placer, alluvial (deposited by water), eluvial (deposited by wind), colluvial... shaft, or running a tunnel or drift to a sufficient depth. (b) Placer claims. (1) Your placer claim is... (deposited by wind), colluvium (deposited by gravity), talus, or other rock not in its original place;...

  15. Environmental Assessment with Finding of No Significant Impact (EA/FONSI) for New Mobile Aircraft Fire Trainer

    DTIC Science & Technology

    2010-04-23

    Dawson Arkose of the Cretaceous and Paleocene age. The Dawson Arkose consists of coarse arkosic sandstone and of interbedded lenticular siltstone and...clay. The surface geology in the vicinity of the proposed action consists primarily of Husted Alluvium and Colluvium overlaying the Dawson Arkose . The

  16. Soils and geomorphic evolution of bedrock facets on a tectonically active mountain front, western Sangre de Cristo Mountains, New Mexico

    NASA Astrophysics Data System (ADS)

    Menges, Christopher M.

    1990-09-01

    Soil profiles, colluvial stratigraphy, and detailed hillslope morphology are key elements used for geomorphic interpretations of the form and long-term evolution of triangular facets on a 1200 m high, tectonically active mountain front. The facets are developed on Precambrian gneisses and Tertiary volcanic and plutonic rocks along a complexly segmented, active normal-fault zone in the Rio Grande rift of northern New Mexico. The detailed morphologies of 20- to 350 m high facets are defined by statistical and time-series analyses of 40 field transects that were keyed to observations of colluvium, bedrock, microtopography, and vegetation. The undissected parts of most facets are transport-limited hillslopes mantled with varying thicknesses (0.1 to > 1 m thick) of sand and gravel colluvium between generally sparse (≤10-30%) bedrock outcrops. Facet soils range from (a) thin (≤ 0.2 m) weakly developed soils with cumulic silty A or transitional A/B epipedons above Cox horizons in bedrock or colluvium, to (b) deep (≥0.5-1 m) moderately to strongly developed profiles containing thick cambic (Bw) and/or argillic (Bt) horizons that commonly extend into highly weathered saprolitic bedrock. The presence of strongly weathered profiles and thick colluvium suggests that rates of colluvial transport and hillslope erosion are less than or equal to rates of soil development over at least a large part of the Holocene. The catenary variation of soils and colluvium on selected facet transects indicate that the degree of soil development generally increases and the thickness of colluvium decreases upslope on most facets. This overall pattern is commonly disrupted on large facet hillslopes by irregular secondary soil variations linked to intermediate-scale (20-60 + m long) concave slope elements. These features are interpreted to reflect discontinuous transport and erosion of colluvium down-slope below bedrock outcrops. The degree of weathering in subsurface bedrock commonly

  17. Overview of landslide problems, research, and mitigation, Cincinnati, Ohio, area

    USGS Publications Warehouse

    Baum, Rex L.; Johnson, Arvid M.

    1996-01-01

    Landslides cause much damage to property throughout the metropolitan area of Cincinnati, Ohio. Most landslides occur in unconsolidated deposits, including colluvium, till, glacial lake clays, and man-made fill derived from colluvium and glacial deposits. Landslides in thin colluvium are widespread on steeper slopes that wall the valleys of the Ohio River and its tributaries. Abundant landslides also form in thick colluvium on flatter slopes, especially where the colluvium has been disturbed by earthwork. Unusual block glides and block-extrusion glides form where till rests on lake clay. Through the years, knowledge of the distribution and causes of landslides has increased as a result of many investigations. This knowledge became part of the basis for landslide mitigation programs adopted by the City of Cincinnati and Hamilton County, Ohio. In 1974 the Cincinnati City Council passed an excavation and fill ordinance to help reduce landslide damage in areas of new construction. In 1989 following much additional study, Cincinnati created a geotechnical office within its Department of Public Works. The office, which is staffed by a geotechnical engineer, an engineering geologist, and two technicians, carries out a mitigation program. Since 1989, members of the geotechnical staff have worked in several ways to reduce landslide damage in the city; their work includes engineering-geologic mapping of selected parts of the city, inspection of retaining walls that impact public right-of-way, review of proposed construction in hillside areas, inspecting and arranging for repair of landslide areas that affect city property, and compiling geologic and geotechnical data on landslide areas within the city. In 1990, Hamilton County also adopted an excavation and fill ordinance to help reduce the damage due to landslides in areas of new construction.

  18. A model of late quaternary landscape development in the Delaware Valley, New Jersey and Pennsylvania

    USGS Publications Warehouse

    Ridge, J.C.; Evenson, E.B.; Sevon, W.D.

    1992-01-01

    In the Delaware Valley of New Jersey and eastern Pennsylvania the late Quaternary history of colluviation, fluvial adjustment, and soil formation is based on the ages of pre-Wisconsinan soils and glacial deposits which are indicated by feld relationships and inferred from mid-latitude climate changes indicated by marine oxygen-isotope records. The area is divided into four terranes characterized by sandstone, gneiss, slate and carbonate rocks. Since the last pre-Wisconsinan glaciation (> 130 ka, inferred to be late Illinoian), each terrane responded differently to chemical and mechanical weathering. During the Sangamon interglacial stage (??? 130-75 ka) in situ weathering is inferred to have occurred at rates greater than transportation of material which resulted in the formation of deep, highly weathered soil and saprolite, and dissolution of carbonate rocks. Cold climatic conditions during the Wisconsinan, on the other hand, induced erosion of the landscape at rates faster than soil development. Upland erosion during the Wisconsinan removed pre-Wisconsinan soil and glacial sediment and bedrock to produce muddy to blocky colluvium, gre??zes lite??es, and alluvial fans on footslopes. Fluvial gravel and overlying colluvium in the Delaware Valley, both buried by late Wisconsinan outwash, are inferred to represent episodes of early and middle Wisconsinan (??? 75-25 ka) upland erosion and river aggradiation followed by river degradation and colluvium deposition. Early-middle Wisconsinan colluvium is more voluminous than later colluvium despite colder, possibly permafrost conditions during the late Wisconsinan ??? 25-10 ka). Extensive colluviation during the early and middle Wisconsinan resulted from a longer (50 kyr), generally cold interval of erosion with a greater availability of easily eroded pre-Wisconsinan surficial materials on uplands than during the late Wisconsinan. After recession of late Wisconsinan ice from its terminal position, soil formation and

  19. Map showing recent and historic landslide activity on coastal bluffs of Puget Sound between Shilshole Bay and Everett, Washington

    USGS Publications Warehouse

    Baum, R.L.; Harp, E.L.; Hultman, W.A.

    2000-01-01

    Many landslides occurred on the coastal bluffs between Seattle and Everett, Washington during the winters of 1996 and 1997. Shallow earth slides and debris flows were the most common, but a few deep-seated rotational earth slides also occurred. The landslides caused significant property damage and interfered with rail traffic; future landslides in the area pose significant hazards to property and public safety. Field observations indicate that ground-water seepage, runoff concentration, and dumping at the tops of the bluffs all contributed to instability of the bluffs. Most landslides in the study area occurred in colluvium, residuum, and landslide deposits derived from the Vashon Drift, particularly the advance outwash. In the northern part of the area, colluvium derived from the Pleistocene Whidbey Formation was also involved in shallow landslides. Comparison of recent activity with historic records in the southern part of the map area indicates that landslides tend to occur in many of the same areas as previous landslides.

  20. Active faulting on the Wallula fault within the Olympic-Wallowa Lineament (OWL), eastern Washington State

    NASA Astrophysics Data System (ADS)

    Sherrod, B. L.; Lasher, J. P.; Barnett, E. A.

    2013-12-01

    Several studies over the last 40 years focused on a segment of the Wallula fault exposed in a quarry at Finley, Washington. The Wallula fault is important because it is part of the Olympic-Wallowa lineament (OWL), a ~500-km-long topographic and structural lineament extending from Vancouver Island, British Columbia to Walla Walla, Washington that accommodates Basin and Range extension. The origin and nature of the OWL is of interest because it contains potentially active faults that are within 50 km of high-level nuclear waste facilities at the Hanford Site. Mapping in the 1970's and 1980's suggested the Wallula fault did not offset Holocene and late Pleistocene deposits and is therefore inactive. New exposures of the Finley quarry wall studied here suggest otherwise. We map three main packages of rocks and sediments in a ~10 m high quarry exposure. The oldest rocks are very fine grained basalts of the Columbia River Basalt Group (~13.5 Ma). The next youngest deposits include a thin layer of vesicular basalt, white volcaniclastic deposits, colluvium containing clasts of vesicular basalt, and indurated paleosols. A distinct angular unconformity separates these vesicular basalt-bearing units from overlying late Pleistocene flood deposits, two colluvium layers containing angular clasts of basalt, and Holocene tephra-bearing loess. A tephra within the loess likely correlates to nearby outcrops of Mazama ash. We recognize three styles of faults: 1) a near vertical master reverse or oblique fault juxtaposing very fine grained basalt against late Tertiary-Holocene deposits, and marked by a thick (~40 cm) vertical seam of carbonate cemented breccia; 2) subvertical faults that flatten upwards and displace late Tertiary(?) to Quaternary(?) soils, colluvium, and volcaniclastic deposits; and 3) flexural slip faults along bedding planes in folded deposits in the footwall. We infer at least two Holocene earthquakes from the quarry exposure. The first Holocene earthquake deformed

  1. Multiple large earthquakes in the past 1500 years on a fault in metropolitan Manila, the Philippines

    USGS Publications Warehouse

    Nelson, A.R.; Personius, S.F.; Rimando, R.E.; Punongbayan, R.S.; Tungol, N.; Mirabueno, H.; Rasdas, A.

    2000-01-01

    The first 14C-based paleoseismic study of an active fault in the Philippines shows that a right-lateral fault on the northeast edge of metropolitan Manila poses a greater seismic hazard than previously thought. Faulted hillslope colluvium, stream-channel alluvium, and debris-flow deposits exposed in trenches across the northern part of the west Marikina Valley fault record two or three surface-faulting events. Three eroded, clay-rich soil B horizons suggest thousands of years between surface faulting events, whereas 14C ages on detrital charcoal constrain the entire stratigraphic sequence to the past 1300-1700 years. We rely on the 14C ages to infer faulting recurrence of hundreds rather than thousands of years. Minimal soil development and modern 14C ages from colluvium overlying a faulted debris-flow deposit in a nearby stream exposure point to a historic age for a probable third or fourth (most recent) faulting event.

  2. BISON ANTIQUUS OCCURRENCE AND PLEISTOCENE-HOLOCENE STRATIGRAPHY, CANADA DEL BUEY, PAJARITO PLATEAU, NEW MEXICO

    SciTech Connect

    RENEAU, STEVEN L.; DRAKOS, PAUL G.; MORGAN, GARY S.

    2007-02-12

    A Bison. (probable Bison antiguus) distal humerus fragment was found within a Pleistocene colluvial deposit on a hillslope above Canada del Buey near White Rock, New Mexico. The Bison fossil is preserved within a buried soil with an inferred age of ca. 50-100 ka, based on soil properties and on stratigraphic position below a deposit of ca. 50-60 ka EI Cajete pumice. This represents the second oldest dated Bison in New Mexico, and one of the few occurrences of this genus in the northern mountains of the state. It is also only the second record of a Pleistocene vertebrate from Los Alamos County, and is a rare occurrence of a pre-25 ka Bison fossil in good stratigraphic context. Hillslopes in the study area are underlain by a sequence of truncated Pleistocene and Holocene soils that are inferred to represent colluvial deposition and soil formation followed by erosion in the mid Pleistocene (buried soil 'b3'), the late Pleistocene (buried soil 'b2'), and the mid-to-late Holocene (buried soil 'b1'). The surface soil is developed in depOSits that overlie 600-800 year-old Ancestral Puebloan sites. Colluvium is dominated by relatively fine-grained (fine to very fine sand) slopewash colluvium deposited by overland flow, but also includes rocky colluvium on hillslopes below mesas. The fine-grained colluvium is likely derived mainly from reworking of eolian deposits. Episodic colluvial deposition appears to, at least in part, accompany and follow episodic eolian events, with intervening periods dominated by erosion and the development of truncated soils.

  3. Summary of lithologic logging of new and existing boreholes at Yucca Mountain, Nevada, March 1994 to June 1994

    SciTech Connect

    Geslin, J.K.; Moyer, T.C.

    1995-04-01

    This report summarizes lithologic logging of core from boreholes at Yucca Mountain, Nevada, conducted from March 1994 to June 1994. Units encountered during logging include Quaternary-Tertiary alluvium and colluvium, Tertiary Rainier Mesa Tuff, all units in the Tertiary Paintbrush Group, and Tertiary Calico Hills Formation. Logging results are presented in a table of contact depths for core from unsaturated zone neutron (UZN) boreholes and graphic lithologic logs for core from north ramp geology (NRG) boreholes.

  4. Environmental Assessment for the Construction and Operation of a New Facility to House the Center for Character and Leadership Development Program

    DTIC Science & Technology

    2010-06-30

    the Fountain Formation of Pennsylvania and Permian age with the predominant bedrock being the Dawson Arkose of the Cretaceous and Paleocene age...The Dawson Arkose consists of coarse arkosic sandstone and of interbedded lenticular siltstone and clay. The surface geology in the vicinity of the...Preferred Alternative consists primarily of Husted Alluvium and Colluvium overlaying the Dawson Arkose . The Dawson Formation bedrock consists of weakly

  5. Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Eastern Mountains and Piedmont Region (Version 2.0)

    DTIC Science & Technology

    2012-04-01

    older igneous and metamorphic rocks (Atwood 1940; Hunt 1974; USGS 2004). Caverns and karst features are found in marble formations in the Piedmont...colluvium derived from sandstone, shale, limestone, and metamorphic and igneous rocks . Other parent materials include deposits of wind-blown loess...lain by highly weathered and eroded Precambrian and Paleozoic metamor- phic and igneous rocks . A number of down-faulted basins contain younger

  6. Interim Regional Supplement to the Corps of Engineers Wetland Delineation Manual: Eastern Mountains and Piedmont Region

    DTIC Science & Technology

    2010-07-01

    6 largely of folded and eroded sedimentary strata and exposed older igneous and metamorphic rocks (Atwood 1940; Hunt 1974; USGS 2004). Caverns...the weathering of local rock formations and include residuum and colluvium derived from sandstone, shale, limestone, and metamorphic and igneous ...and igneous rocks . A number of down-faulted basins contain younger Triassic and Jurassic sandstones, shales, and other sedimentary rocks . The

  7. University of Kansas Research and Educational Support for U.S. Army Programs and Initiatives at Fort Leavenworth, Kansas

    DTIC Science & Technology

    2013-09-03

    alluvium and colluvium flanked primarily by the older Cretaceous and Triassic igneous rocks (Fig. 4.3). Figure 4.2. Natural-color image mosaic of...the flanking ranges are Cretaceous and Triassic igneous and metamorphic rocks . (O’Leary & Whitney, USGS Geologic Map of the Kandahar Region, 2005...concentrations also occur along the periphery of the basin, but these are a result of the bedrock, primarily dolomites, with some igneous intrusions. 42

  8. Transformation of dilative and contractive landslide debris into debris flows-An example from marin County, California

    USGS Publications Warehouse

    Fleming, R.W.; Ellen, S.D.; Algus, M.A.

    1989-01-01

    The severe rainstorm of January 3, 4 and 5, 1982, in the San Francisco Bay area, California, produced numerous landslides, many of which transformed into damaging debris flows. The process of transformation was studied in detail at one site where only part of a landslide mobilized into several episodes of debris flow. The focus of our investigation was to learn whether the landslide debris dilated or contracted during the transformation from slide to flow. The landslide debris consisted of sandy colluvium that was separable into three soil horizons that occupied the axis of a small topographic swale. Failure involved the entire thickness of colluvium; however, over parts of the landslide, the soil A-horizon failed separately from the remainder of the colluvium. Undisturbed samples were taken for density measurements from outside the landslide, from the failure zone and overlying material from the part of the landslide that did not mobilize into debris flows, and from the debris-flow deposits. The soil A-horizon was contractive and mobilized to flows in a process analogous to liquefaction of loose, granular soils during earthquakes. The soil B- and C-horizons were dilative and underwent 2 to 5% volumetric expansion during landslide movement that permitted mobilization of debris-flow episodes. Several criteria can be used in the field to differentiate between contractive and dilative behavior including lag time between landsliding and mobilization of flow, episodic mobilization of flows, and partial or complete transformation of the landslide. ?? 1989.

  9. Applying Distributed, Coupled Hydrological Slope-Stability Models for Landslide Hazard Assessments

    NASA Astrophysics Data System (ADS)

    Godt, J. W.; Baum, R. L.; Lu, N.; Savage, W. Z.; McKenna, J. P.

    2006-12-01

    Application of distributed, coupled hydrological slope-stability models requires knowledge of hydraulic and material-strength properties at the scale of landslide processes. We describe results from a suite of laboratory and field tests that were used to define the soil-water characteristics of landslide-prone colluvium on the steep coastal bluffs in the Seattle, Washington area and then use these results in a coupled model. Many commonly used tests to determine soil-water characteristics are performed for the drying process. Because most soils display a pronounced hysteresis in the relation between moisture content and matric suction, results from such tests may not accurately describe the soil-water characteristics for the wetting process during rainfall infiltration. Open-tube capillary-rise and constant-flow permeameter tests on bluff colluvium were performed in the laboratory to determine the soil-water characteristic curves (SWCC) and unsaturated hydraulic conductivity functions (HCF) for the wetting process. Field-tests using a borehole permeameter were used to determine the saturated hydraulic conductivity of colluvial materials. Measurements of pore-water response to rainfall were used in an inverse numerical modeling procedure to determine the in-situ hydraulic parameters of hillside colluvium at the scale of the instrument installation. Comparison of laboratory and field results show that although both techniques generally produce SWCCs and HCFs with similar shapes, differences in bulk density among field and lab tests yield differences in saturated moisture content and saturated hydrologic conductivity. We use these material properties in an application of a new version of a distributed transient slope stability model (TRIGRS) that accounts for the effects of the unsaturated zone on the infiltration process. Applied over a LiDAR-based digital landscape of part of the Seattle area for an hourly rainfall history known to trigger shallow landslides, the

  10. Determination of paleoseismic activity over a large time-scale: Fault scarp dating with 36Cl

    NASA Astrophysics Data System (ADS)

    Mozafari Amiri, Nasim; Tikhomirov, Dmitry; Sümer, Ökmen; Özkaymak, Çaǧlar; Uzel, Bora; Ivy-Ochs, Susan; Vockenhuber, Christof; Sözbilir, Hasan; Akçar, Naki

    2016-04-01

    Bedrock fault scarps are the most direct evidence of past earthquakes to reconstruct seismic activity in a large time-scale using cosmogenic 36Cl dating if built in carbonates. For this method, a surface along the fault scarp with a minimum amount of erosion is required to be chosen as an ideal target point. The section of the fault selected for sampling should cover at least two meters of the fault surface from the lower part of the scarp, where intersects with colluvium wedge. Ideally, sampling should be performed on a continuous strip along the direction of the fault slip direction. First, samples of 10 cm high and 15 cm wide are marked on the fault surface. Then, they are collected using cutters, hammer and chisel in a thickness of 3 cm. The main geometrical factors of scarp dip, scarp height, top surface dip and colluvium dip are also measured. Topographic shielding in the sampling spot is important to be estimated as well. Moreover, density of the fault scarp and colluvium are calculated. The physical and chemical preparations are carried in laboratory for AMS and chemical analysis of the samples. A Matlab® code is used for modelling of seismically active periods based on increasing production rate of 36Cl following each rupture, when a buried section of a fault is exposed. Therefore, by measuring the amount of cosmogenic 36Cl versus height, the timing of major ruptures and their offsets are determined. In our study, Manastır, Mugırtepe and Rahmiye faults in Gediz graben, Priene-Sazlı, Kalafat and Yavansu faults in Büyük Menderes graben and Ören fault in Gökava half-graben have been examined in the seismically active region of Western Turkey. Our results reconstruct at least five periods of high seismic activity during the Holocene time, three of which reveal seismic ruptures beyond the historical pre-existing data.

  11. Initiation conditions for debris flows generated by runoff at Chalk Cliffs, central Colorado

    NASA Astrophysics Data System (ADS)

    Coe, Jeffrey A.; Kinner, David A.; Godt, Jonathan W.

    2008-04-01

    We have monitored initiation conditions for six debris flows between May 2004 and July 2006 in a 0.3 km 2 drainage basin at Chalk Cliffs; a band of hydrothermally-altered quartz monzonite in central Colorado. Debris flows were initiated by water runoff from colluvium and bedrock that entrained sediment from rills and channels with slopes ranging from about 14° to 45°. The availability of channel material is essentially unlimited because of thick channel fill and refilling following debris flows by rock fall and dry ravel processes. Rainfall exceeding I = 6.61( D) - 0.77 , where I is rainfall intensity (mm/h), and D is duration (h), was required for the initiation of debris flows in the drainage basin. The approximate minimum runoff discharge from the surface of bedrock required to initiate debris flows in the channels was 0.15 m 3/s. Colluvium in the basin was unsaturated immediately prior to (antecedent) and during debris flows. Antecedent, volumetric moisture levels in colluvium at depths of 1 cm and 29 cm ranged from 4-9%, and 4-7%, respectively. During debris flows, peak moisture levels in colluvium at depths of 1 cm and 29 cm ranged from 10-20%, and 4-12%, respectively. Channel sediment at a depth of 45 cm was unsaturated before and during debris flows; antecedent moisture ranged from 20-22%, and peak moisture ranged from 24-38%. Although we have no measurements from shallow rill or channel sediment, we infer that it was unsaturated before debris flows, and saturated by surface-water runoff during debris flows. Our results allow us to make the following general statements with regard to debris flows generated by runoff in semi-arid to arid mountainous regions: 1) high antecedent moisture levels in hillslope and channel sediment are not required for the initiation of debris flows by runoff, 2) locations of entrainment of sediment by successive runoff events can vary within a basin as a function of variations in the thickness of existing channel fill and the

  12. Youngest volcanism about 1 million years ago at Kahoolawe Island, Hawaii

    USGS Publications Warehouse

    Sano, H.; Sherrod, D.R.; Tagami, Takahiro

    2006-01-01

    Young volcanic deposits in Kahoolawe Island, cutting up through the caldera-filling lava, colluvium and talus in the west wall of Kanapou Bay, had long been stratigraphically considered the rejuvenated-stage products. New K-Ar ages, combined with magnetic polarity data, show that young volcanism was at about 0.98-1.04 Ma and indicate no substantial quiescence between the filling of the caldera and the young volcanism. This result, and the tholeiitic characteristics of the young deposits, suggest they are a component of late shield-stage volcanism. ?? 2005 Elsevier B.V. All rights reserved.

  13. Directable weathering of concave rock using curvature estimation.

    PubMed

    Jones, Michael D; Farley, McKay; Butler, Joseph; Beardall, Matthew

    2010-01-01

    We address the problem of directable weathering of exposed concave rock for use in computer-generated animation or games. Previous weathering models that admit concave surfaces are computationally inefficient and difficult to control. In nature, the spheroidal and cavernous weathering rates depend on the surface curvature. Spheroidal weathering is fastest in areas with large positive mean curvature and cavernous weathering is fastest in areas with large negative mean curvature. We simulate both processes using an approximation of mean curvature on a voxel grid. Both weathering rates are also influenced by rock durability. The user controls rock durability by editing a durability graph before and during weathering simulation. Simulations of rockfall and colluvium deposition further improve realism. The profile of the final weathered rock matches the shape of the durability graph up to the effects of weathering and colluvium deposition. We demonstrate the top-down directability and visual plausibility of the resulting model through a series of screenshots and rendered images. The results include the weathering of a cube into a sphere and of a sheltered inside corner into a cavern as predicted by the underlying geomorphological models.

  14. Identifying Colluvial Slopes by Airborne LiDAR Analysis

    NASA Astrophysics Data System (ADS)

    Kasai, M.; Marutani, T.; Yoshida, H.

    2015-12-01

    Colluvial slopes are one of major sources of landslides. Identifying the locations of the slopes will help reduce the risk of disasters, by avoiding building infrastructure and properties nearby, or if they are already there, by applying appropriate counter measures before it suddenly moves. In this study, airborne LiDAR data was analyzed to find their geomorphic characteristics to use for extracting their locations. The study site was set in the suburb of Sapporo City, Hokkaido in Japan. The area is underlain by Andesite and Tuff and prone to landslides. Slope angle and surface roughness were calculated from 5 m resolution DEM. These filters were chosen because colluvial materials deposit at around the angle of repose and accumulation of loose materials was considered to form a peculiar surface texture differentiable from other slope types. Field survey conducted together suggested that colluvial slopes could be identified by the filters with a probability of 80 percent. Repeat LiDAR monitoring of the site by an unmanned helicopter indicated that those slopes detected as colluviums appeared to be moving at a slow rate. In comparison with a similar study from the crushed zone in Japan, the range of slope angle indicative of colluviums agreed with the Sapporo site, while the texture was rougher due to larger debris composing the slopes.

  15. Soils, surficial geology, and geomorphology of the Bear Creek Valley Low-Level Waste Disposal Development and Demonstration Program site

    SciTech Connect

    Lietzke, D.A.; Lee, S.Y.; Lambert, R.E.

    1988-04-01

    An intensive soil survey was conducted on the proposed Low-Level Waste Disposal Development and Demonstration Program site (LLWDDD) in Bear Creek Valley. Soils on the site were related to the underlying residuum and to the surficial colluvium and alluvium. Within any particular geologic formation, soils were subdivided based mostly on the degree of weathering, as reflected by saprolite weathering and morphologic features of the soils. Degree of weathering was related both to slope shape and gradient and to the joint-fracture system. Erosion classes were also used to make further subdivisions of any particular soil. Deep pits were dug in each of the major Conasauga Group formations (Pumpkin Valley, Rogersville, Maryville, and Nolichucky) for soil and saprolite characterization. Because of the widespread presence of alluvium and colluvium, which are potential sources of fill and final cover material, pits and trenches were dug to characterize the properties of these soils and to try to understand the past geomorphic history of the site. The results of the soil survey investigation indicated that the deeply weathered Pumpkin Valley residuum has good potential for the construction of tumuli or other types of belowground or aboveground burial of prepackaged compacted waste. 11 refs., 30 figs., 3 tabs.

  16. Debris Flow Initiation and Fan Reworking in the Green River Canyons of the Eastern Uinta Mountains: The Limited Role of Wildfire and the Significance of Low-Magnitude Floods

    NASA Astrophysics Data System (ADS)

    Larsen, I. J.; Schmidt, J. C.; Pederson, J. L.; Martin, J. A.

    2003-12-01

    The primary determinant on channel organization of the Green River in the canyons of the eastern Uinta Mountains is the occurrence and frequency of debris flows in tributary watersheds. The frequency of these debris flows appears to be related to climatic factors, not factors related to wildfire. Debris flows in the eastern Uinta Mountains occur by a process known as the firehose effect, wherein overland flow generated on bedrock slopes cascades down steep cliffs and saturates and impacts colluvium stored in bedrock hollows. The colluvium fails, initiating debris flows that travel downslope to the Green River. The dry climate and high-strength bedrock cause hillslopes to be weathering-limited, prohibiting the formation of extensive regolith and vegetative cover. This reduces the degree vegetation regulates geomorphic processes and, in turn, causes wildfire to have little influence on debris flow initiation; slight increases in watershed runoff do not appear to alter the likelihood of this process occurring. A secondary determinant on channel organization in debris fan-dominated canyons are the magnitude of mainstem discharges and the degree to which they rework debris flow deposits; in this case flows are regulated by Flaming Gorge Dam. Substantial reworking of debris flow deposits can be accomplished by mainstem floods with discharges greater than 75%\\ of the pre-dam two year flood, whereas floods with magnitudes less than 40%\\ of the pre-dam 2-year flood do little reworking.

  17. Numerical modeling of rainfall thresholds for shallow landsliding in the Seattle, Washington, area

    USGS Publications Warehouse

    Godt, Jonathan W.; McKenna, Jonathan P.

    2008-01-01

    The temporal forecasting of landslide hazard has typically relied on empirical relations between rainfall characteristics and landslide occurrence to identify conditions that may cause shallow landslides. Here, we describe an alternate, deterministic approach to define rainfall thresholds for landslide occurrence in the Seattle, Washington, area. This approach combines an infinite slope-stability model with a variably saturated flow model to determine the rainfall intensity and duration that leads to shallow failure of hillside colluvium. We examine the influence of variation in particle-size distribution on the unsaturated hydraulic properties of the colluvium by performing capillary-rise tests on glacial outwash sand and three experimental soils with increasing amounts of fine-grained material. Observations of pore-water response to rainfall collected as part of a program to monitor the near-surface hydrology of steep coastal bluffs along Puget Sound were used to test the numerical model results and in an inverse modeling procedure to determine the in situ hydraulic properties. Modeling results are given in terms of a destabilizing rainfall intensity and duration, and comparisons with empirical observations of landslide occurrence and triggering rainfall indicate that the modeling approach may be useful for forecasting landslide occurrence.

  18. Preliminary palaeoseismological results from the Kaparelli fault (Central Greece)

    NASA Astrophysics Data System (ADS)

    Pavlides, S.; Koukouvelas, I.; Ganas, A.; Kokkalas, S.; Tsodoulos, I.; Stamatopoulos, L.; Goyntromichou, C.; Valkaniotis, S.

    2003-04-01

    The roughly E-W trending Kaparelli-Plataees Fault is an on-shore normal fault segment located at the eastern end of the Gulf of Corinth Rift. The fault is a segment of the greater Plataees-Avlon fault zone (Beotia-Attica). It was activated during the third event of the February- March 1981 Alkyonides seismic sequence (Ms 6.7; 6.6; 6.4). The ground offset was 70cm, although some values of more than 1m have been reported too. The slip vector was 200-220 o/60-70 o (azimuth, rake). This presentation is a brief account of our efforts to search the seismic history and to resolve slip of the Kaparelli normal fault, in terms of trenching techniques, tectonostratigraphy of fault-related colluvial deposits and dating palaeoevents. Three (3) trenches have been excavated across the 1981 fault trace during May-June 2002. They are oriented perpendicular to the fault strike, and are located in Holocene deformed sediments (colluvium), in contact with bedrock limestone. Trenches have lengths of 15 to 30 m and depths of 2-4 m and their walls were mapped in scale 1:20. The KAP1 comprises a sequence of clay, sand, colluvial wedges and soil. In this trench the last (1981) event is clearly shown within a greater fault zone of 3m width. The hangingwall block of the reactivated fault strand during the 1981 event comprises a strongly rotated (>60o) sedimentary sequence corresponding with cumulative fault deformation. KAP2 and KAP3 trenches constitute of typical colluvium (unconsolidated angular limestone fragments and soil), which includes occasionaly tile fragments, some charcoal and pottery fragments. We have identified at least three (3) seismic events based on a) colluvium tectonostratigraphy mainly, b) deposition of sedimentary layers, c)formation of soil, and d) small displacement of few horizons. Although previous works have suggested that the fault was activated approximately 3 times during the last 20 ka years and remained quiet for 10 ka years our preliminary results from the

  19. Volumetric analysis and hydrologic characterization of a modern debris flow near Yucca Mountain, Nevada

    USGS Publications Warehouse

    Coe, J.A.; Glancy, P.A.; Whitney, J.W.

    1997-01-01

    On July 21 or 22, 1984, debris flows triggered by rainfall occurred on the southern hillslope of Jake Ridge, about 6 km east of the crest of Yucca Mountain, Nevada. Rain gages near Jake Ridge recorded 65 mm and 69 mm on July 21, and 20 mm and 17 mm on July 22. Rates of rainfall intensity ranged up to 73 mm/h on the twenty-first, and 15 mm/h on the twenty-second. Digital elevation models with 2.0 m grid-node spacing, measured from pre-storm and post-storm aerial stereo-photographs, were used to map hillslope erosion and the downslope distribution of debris. Volumetric calculations indicate that about 7040 m3 of debris was redistributed on the 49,132 m2 hillslope study area during the two-day storm period. About 4580 m3 (65%) of the eroded sediment was deposited within the study area and the remaining 35% was deposited outside the study area in a short tributary to Fortymile Wash and in the wash itself. The maximum and mean depths of erosion in the study area were about 1.8 m and 5 cm, respectively. The mean depths of erosion on the upper and middle hillslope were 27 cm and 4 cm, respectively. The mean depth of deposition on the lower hillslope was 16 cm. Analysis of the values of cumulative precipitation in the context of the precipitation-frequency atlas of the National Oceanic and Atmospheric Administration indicates that precipitation from the main storm on July 21 was more than double that expected, on average, once during a 100-year period. The relations of precipitation intensity/duration, developed from data recorded at a nearby precipitation gage, indicate a storm interval of 500 years or greater. The amount of erosion caused by such a storm is primarily dependent on three variables: storm intensity, development of the drainage network on the hillslope, and the amount of available colluvium. Additionally, the erosive ability of successive storms of equal intensity will decrease because such storms would tend to progressively isolate and reduce the amount of

  20. Field and laboratory rainfall simulation as a tool to investigate Quaternary badland geomorphic development

    NASA Astrophysics Data System (ADS)

    Kuhn, Nikolaus; Kasanin-Grubin, Milica; Yair, Aaron; Rorke, Brian; Schwanghart, Wolfgang

    2010-05-01

    . However, the stability is achieved in different ways. In the Dinosaur Badlands, weathering rates are low compared to erosion capacity, maintaining continuous evacuation of sediment from slopes to the flood planes of the Red Deer River system. Only a very pronounced contrast between winter weathering and drier summers would generate a colluvium and thus change slope hydrology. In the Zin Valley, the development of a thick colluvium at the foot of the slopes has increased infiltration capacity, reducing runoff and sediment yield into the floodplain. Only an increase in rainfall magnitude would improve runoff continuity and induce the erosion of the colluvium. The somewhat surprising, long-term resilience of the badland slope systems identified in this study illustrates the versatility combining rainfall simulation experiments with numerical modeling in landscape evolution studies.

  1. Experimental investigation into Quaternary badland geomorphic development

    NASA Astrophysics Data System (ADS)

    Kasanin-Grubin, Milica; Kuhn, Nikolaus; Yair, Aaron; Bryan, Rorke; Schwanghart, Wolfgang

    2010-05-01

    to the flood planes of the Red Deer River system. Only a very pronounced contrast between winter weathering and drier summers would generate a colluvium and thus change slope hydrology. In the Zin Valley the development of a thick colluvium at the foot of the slopes has increased infiltration capacity, reducing runoff and sediment yield into the floodplain. Here, only an increase in rainfall magnitude would improve runoff continuity and induce the erosion of the colluvium. This would in turn reduce infiltration capacity and thus initiate a positive feedback on runoff and sediment yield into the Zin River. Overall, Holocene climate change appears to be insufficient to change the geomorphic development in both badlands. However, this stability is achieved not despite of climate, but because of the specific history of geomorphic development. In addition, the combination of erosion and weathering experiments with numerical modeling demonstrates the versatility of Experimental Geomorphology in landscape evolution studies.

  2. The mineral resource potential of the Wadi Habawnah and Najran quadrangles, sheets 17/44A and 17/44C, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Fenton, Michael D.

    1983-01-01

    The metallic resource potential of the Wadi Habawnah and Najran quadrangles in the southern Precambrian Arabian Shield has been determined primarily by reconnaissance rock geochemistry, limited wadi-sediment and colluvium geochemistry, and gossanous and ferruginous outcrop geochemistry. These surveys were guided by geological information acquired during previous reconnaissance mapping. Locally anomalous areas in alkalic and calc-alkalic granitic terrane are possible sources of niobium-zirconiumthorium-fluorite, tin-tungsten, and copper-molybdenum, although the potential of these areas does not appear to be outstanding. The reconnaissance geochemistry of the layered volcanic terrane and the geochemistry of gossanous and ferruginous outcrops indicate that the potential for stratiform base metal sulfide deposits is low.

  3. Summary of lithologic logging of new and existing boreholes at Yucca Mountain, Nevada, August 1993 to February 1994

    SciTech Connect

    Geslin, J.K.; Moyer, T.C.; Buesch, D.C.

    1995-05-01

    Yucca Mountain, Nevada, is being investigated as a potential site for a high-level radioactive waste repository. This report summarizes the lithologic logging of new and existing boreholes at Yucca Mountain that was done from August 1993 to February 1994 by the Rock Characteristics Section, Yucca Mountain Project Branch, US Geological Survey (USGS). Units encountered during logging include Quaternary-Tertiary alluvium/colluvium, Tertiary Rainier Mesa Tuff, all units in the Tertiary Paintbrush Group, Tertiary Calico Hills Formation and Tertiary Prow Pass Tuff. We present criteria used for recognition of stratigraphic contacts, logging results as tables of contact depths for core from neutron (UZN) boreholes and graphical lithologic logs for core from non-UZN boreholes, and descriptions of several distinctive nonwelded tuffs recognized in the PTn hydrogeologic unit of the Paintbrush Group.

  4. Estimation of debris-flow prone basins based on geomorphic quantities and rainfall amount on granite slopes in Japan

    NASA Astrophysics Data System (ADS)

    Wakatsuki, Tsuyoshi; Sato, Masato; Inomata, Yasuhiro; Takeda, Naofumi; Aoki, Shinya

    2016-04-01

    In Japan, debris flows generally occur by fluidization of colluviums of soil slips after heavy rainfall on steep slopes. For the reduction of debris-flow disasters, the relationship among geomorphic quantities of the mountainous small drainage basin, the arrival of the debris flow to the basin outlet, and rainfall characteristics was examined by using the distribution maps of slope movements and digital elevation models (DEM) on five granite slopes. The results showed that there were geomorphic thresholds determining the lower limit of the arrival of the debris flow to the basin outlet based on the drainage area and the relief ratio. The geomorphic thresholds become smaller with an increase in rainfall amount, which increases the debris-flow risk in many basins.

  5. Quaternary geology of Avery Island, Louisiana

    SciTech Connect

    Autin, W.J.; McCulloh, R.P.; Davison, A.T.

    1986-09-01

    Avery Island, one of the Five Islands salt domes of south-central Louisiana, is a piercement-type dome that has been uplifted from several kilometers' depth. It is nearly circular in plan with a maximum elevation approximately 50 m above the surrounding coastal marsh. Dissection has produced a terrain of gullies and steep slopes. The features identified indicate a complex geologic history for Avery Island. Deposition of late Pleistocene sediments in a low-relief alluvial plain and subsequent soil development predate domal uplift. The stratigraphy of loess and colluvial silts indicates the island was emergent during loess depositions. The degree of dissection, distribution of colluvium, and shearing of Quaternary sediments reflects continual uplift after loess deposition.

  6. Thirty-one years of debris-flow observation and monitoring near La Honda, California, USA

    USGS Publications Warehouse

    Wieczorek, G.F.; Wilson, R.C.; Ellen, S.D.; Reid, M.E.; Jayko, A.S.

    2007-01-01

    From 1975 until 2006,18 intense storms triggered at least 248 debris flows within 10 km2 northwest of the town of La Honda within the Santa Cruz Mountains, California. In addition to mapping debris flows and other types of landslides, studies included soil sampling and geologic mapping, piezometric and tensiometer monitoring, and rainfall measurement and recording. From 1985 until 1995, a system with radio telemetered rain gages and piezometers within the La Honda region was used for issuing six debris-flow warnings within the San Francisco Bay region through the NOAA ALERT system. Depending upon the relative intensity of rainfall during storms, debris flows were generated from deep slumps, shallow slumps, shallow slides in colluvium and shallow slides over bedrock. Analysis shows the storms with abundant antecedent rainfall followed by several days of steady heavy intense rainfall triggered the most abundant debris flows. ?? 2007 millpress.

  7. Location of photographs showing landslide features in the Little North Santiam River Basin, Oregon

    USGS Publications Warehouse

    Sobieszczyk, Steven

    2010-01-01

    Data points represent locations of photographs taken of landslides in the Little North Santiam River Basin, Oregon. Photos were taken in spring of 2010 during field verification of landslide locations (deposits previously mapped using LiDAR-derived imagery). The photographs depict various landslide features, such as scarps, pistol-butt trees, or colluvium deposits. This work was completed as part of the Master's thesis "Turbidity Monitoring and LiDAR Imagery Indicate Landslides are Primary Source of Suspended-Sediment Load in the Little North Santiam River Basin, Oregon, Winter 2009-2010" by Steven Sobieszczyk, Portland State University and U.S. Geological Survey. Data layers in this geodatabase include: landslide deposit boundaries (Deposits); field-verfied location imagery (Photos); head scarp or scarp flanks (Scarp_Flanks); and secondary scarp features (Scarps).The geodatabase template was developed by the Oregon Department of Geology and Mineral Industries (Burns and Madin, 2009).

  8. A comparative analysis of simulated and observed landslide locations triggered by Hurricane Camille in Nelson County, Virginia

    USGS Publications Warehouse

    Morrissey, M.M.; Wieczorek, G.F.; Morgan, B.A.

    2008-01-01

    In 1969, Nelson County, Virginia received up to 71 cm of rain within 12 h starting at 7 p.m. on August 19. The total rainfall from the storm exceeded the 1000-year return period in the region. Several thousands of landslides were induced by rainfall associated with Hurricane Camille causing fatalities and destroying infrastructure. We apply a distributed transient response model for regional slope stability analysis to shallow landslides. Initiation points of over 3000 debris flows and effects of flooding from this storm are applied to the model. Geotechnical data used in the calculations are published data from samples of colluvium. Results from these calculations are compared with field observations such as landslide trigger location and timing of debris flows to assess how well the model predicts the spatial and temporal distribution. of landslide initiation locations. The model predicts many of the initiation locations in areas where debris flows are observed. Copyright ?? 2007 John Wiley & Sons, Ltd.

  9. Dating of ancient debris fan complexes from Lantau Island, Hong Kong: The potential relationship between landslide activity and climate change

    NASA Astrophysics Data System (ADS)

    Sewell, R. J.; Wong, J.; Wang, N.

    2013-12-01

    Debris fan complexes along mountain range fronts are known to be sensitive indicators of changes in hydrological conditions and hence may serve as a proxy for climate change. We have obtained fifty-two Optically Stimulated Luminescence (OSL) ages from debris fan complexes at five sites bordering the coastal foothills of western Lantau Island, Hong Kong. The debris fan complexes generally comprise an upper sequence of dominantly loose, gravelly colluvium and alluvium representing mainly debris flood deposits, and a lower sequence of dominantly cohesive, bouldery colluvium representing debris flow deposits. The age data from the debris fan complexes suggest three main periods of accumulation: <5,000 yr BP, 8,000 - 15,000 yr BP, and 20,000 - 40,000 yr BP. The youngest two periods appear to be dominated by debris flood deposition, whereas the older period is dominated mainly by debris flow deposition. We hypothesize that immediately prior to the Last Glacial Maximum (LGM, i.e. 21,000 yr BP), the climate was cool and dry. Upland areas were probably devoid of vegetation, providing favorable conditions for sediment production in source areas. These debris-laden source areas are likely to have been mobilized en masse during periodic intense rainstorm activity leading to accumulation of thick debris lobes along the coastal foothills. During post-LGM, the climate was warmer and more humid. Pluvial conditions predominated; forests occupied the upland source areas, leading to possibly reduced sediment yields, more frequent flash floods and deposition of debris dominated by debris flood. Compared with recent studies on the weathering and erosion history of the Pearl River Delta, our landslide age data suggest a potential link between increased landslide activity and intensification of the Asian Monsoon during the Early Holocene to Middle Holocene.

  10. Paleoseismic investigations of the Paintbrush Canyon fault in southern Midway Valley, Yucca Mountain, Nevada: Preliminary results

    SciTech Connect

    Swan, F.H.; Wesling, J.R.; Thomas, A.P. )

    1993-04-01

    Trench mapping in southern Midway Valley provides evidence of multiple surface-faulting events on a western splay of the Paintbrush Canyon fault during the middle to late Pleistocene. The 6-m-wide fault zone exposed in the trench strikes N30-45E and dips steeply ([approximately]78[degree]) to the west, although some shears within the zone dip to the east. Tertiary volcanic bedrock is exposed only on the footwall block within the trench. Unconsolidated colluvial and eolian deposits are present in the hanging-wall block and above bedrock in the footwall block. These deposits tentatively are assigned, respectively, mid Pleistocene and late Pleistocene ages based on correlations with surficial map units in Midway Valley. Three to five displacement events are inferred based on faulted colluvial and eolian deposits, and scarp-derived colluvial wedges. Total cumulative dip-slip displacement of the oldest middle Pleistocene subunit is estimated to be about 170 to 270 cm. The dip-slip displacement associated with the youngest event is about 15 cm. The earlier displacements are estimated to have produced between 40 and 85 cm of dip-slip displacement per event. The most recent event occurred after deposition of late Pleistocene colluvium deposited against the fault scarp but before deposition of an overlying hillslope-derived colluvium of probable late pleistocene age. Based on the preliminary results of the authors study, the middle to late Quaternary rate of dip-slip displacement is approximately 0.01 m/kyr or less. Ongoing work, including soil-stratigraphic studies and numerical dating of deposits, should better constrain the timing and a rate of faulting along this western splay of the Paintbrush Canyon fault.

  11. Paleoseismology of a possible fault scarp in Wenas Valley, central Washington

    USGS Publications Warehouse

    Sherrod, Brian L.; Barnett, Elizabeth A.; Knepprath, Nichole; Foit, Franklin F.

    2013-01-01

    In October 2009, two trenches excavated across an 11-kilometer-long scarp at Wenas Valley in central Washington exposed evidence for late Quaternary deformation. Lidar imagery of the Wenas Valley illuminated the west-northwest-trending, 2- to 8-meter-high scarp as it bisected alluvial fans developed at the mouths of canyons along the south side of Umtanum Ridge. The alignment of the scarp and aeromagnetic lineaments suggested that the scarp may be a product of and controlled by the same tectonic structure that produced the magnetic lineaments. Several large landslides mapped in the area demonstrated the potential for large mass-wasting events in the area. In order to test whether the scarp was the result of an earthquake-generated surface rupture or a landslide, trenches were excavated at Hessler Flats and McCabe Place. The profiles of bedrock and soil stratigraphy that underlie the scarp in each trench were photographed, mapped, and described, and a sequence of depositional and deformational events established for each trench. The McCabe Place trench exposed a sequence of volcaniclastic deposits overlain by soils and alluvial deposits separated by three unconformities. Six normal faults and two possible reverse faults deformed the exposed strata. Crosscutting relations indicated that up to five earthquakes occurred on a blind reverse fault, and a microprobe analysis of lapilli suggested that the earliest faulting occurred after 47,000 years before present. The Hessler Flat trench exposure revealed weathered bedrock that abuts loess and colluvium deposits and is overlain by soil, an upper sequence of loess, and colluvium. The latter two units bury a distinctive paloesol.

  12. Aggradation-incision transition in arid environments at the end of the Pleistocene: An example from the Negev Highlands, southern Israel

    NASA Astrophysics Data System (ADS)

    Faershtein, Galina; Porat, Naomi; Avni, Yoav; Matmon, Ari

    2016-01-01

    One of the most significant environmental processes that occurred at the transition from the last glacial phase into the present inter-glacial phase in arid regions was the shift from aggradation to incision in the drainage systems. This is evident by the sharp transition from a fluvial regime depositing fine-grained sediment within the wadis to intensive incision which formed gullies and narrow channels that dissected the late Pleistocene sediments. In order to investigate this transition, we studied three small-scale basins in the arid region of the Negev Highlands, southern Israel. Although the selected basins drain toward different base levels, their geomorphological parameters, particle size distribution of alluvial units and their OSL ages are similar. Sediments from the penultimate glacial cycle are found in patches in the bigger catchments. Fluvial loess was widely deposited since at least 67 ka until after 28 ka, covering valleys and slopes. Between 28 and 24 ka, loess was washed from the slopes into the channels, exposing the underlying colluvium. At 24 ka erosion began with the transport of slope colluvium as gravels into the valleys that eroded the underlying loess sediments. Incision became dominant at 12 ka and is still ongoing and intensifying. Dust and reworked loess continued to be deposited during the main incision stages. It is proposed that the transition from aggradation to incision was controlled by rates of loess supply and removal. Until 24 ka dust choked the drainage system and only after reduction in dust supply was erosion and incision possible. It began first on the slopes and then in the channels. Our results show that an increase in precipitation is not a prerequisite for initiation of incision as is often assumed. Similar processes are described in other arid zones around the world.

  13. Evidence for Late Holocene earthquakes on the Utsalady Point fault, Northern Puget Lowland, Washington

    USGS Publications Warehouse

    Johnson, S.Y.; Nelson, A.R.; Personius, S.F.; Wells, R.E.; Kelsey, H.M.; Sherrod, B.L.; Okumura, K.; Koehler, R.; Witter, R.C.; Bradley, L.-A.; Harding, D.J.

    2004-01-01

    Trenches across the Utsalady Point fault in the northern Puget Lowland of Washington reveal evidence of at least one and probably two late Holocene earthquakes. The "Teeka" and "Duffers" trenches were located along a 1.4-km-long, 1-to 4-m-high, northwest-trending, southwest-facing, topographic scarp recognized from Airborne Laser Swath Mapping. Glaciomarine drift exposed in the trenches reveals evidence of about 95 to 150 cm of vertical and 200 to 220 cm of left-lateral slip in the Teeka trench. Radiocarbon ages from a buried soil A horizon and overlying slope colluvium along with the historical record of earthquakes suggest that this faulting occurred 100 to 400 calendar years B.P. (A.D. 1550 to 1850). In the Duffers trench, 370 to 450 cm of vertical separation is accommodated by faulting (???210 cm) and folding (???160 to 240 cm), with probable but undetermined amounts of lateral slip. Stratigraphic relations and radiocarbon ages from buried soil, colluvium, and fissure fill in the hanging wall suggest the deformation at Duffers is most likely from two earthquakes that occurred between 100 to 500 and 1100 to 2200 calendar years B.P., but deformation during a single earthquake is also possible. For the two-earthquake hypothesis, deformation at Teeka trench in the first event involved folding but not faulting. Regional relations suggest that the earthquake(s) were M ??? ???6.7 and that offshore rupture may have produced tsunamis. Based on this investigation and related recent studies, the maximum recurrence interval for large ground-rupturing crustal-fault earthquakes in the Puget Lowland is about 400 to 600 years or less.

  14. Geohydrologic data collected from shallow neutron-access boreholes and resultant-preliminary geohydrologic evaluations, Yucca Mountain area, Nye County, Nevada

    SciTech Connect

    Blout, D.O.; Hammermeister, D.P.; Loskot, C.L.; Chornack, M.P.

    1994-12-31

    In cooperation with the US Department of Energy, 74 neutron-access boreholes were drilled in and near the southwestern part of the Nevada Test Site, Nye County, Nevada. Drilling, coring, sample collection and handling, and lithologic and preliminary geohydrologic data are presented in this report. The boreholes were drilled in a combination of alluvium/colluvium, ash-flow tuff, ash-fall tuff, or bedded tuff to depths of 4.6 to 36.6 meters. Air was used as a drilling medium to minimize disturbance of the water content and water potential of drill cuttings, core, and formation rock. Drill cuttings were collected at approximately 0.6-meter intervals. Core was taken at selected intervals from the alluvium/colluvium using drive-coring methods and from tuff using rotary-coring methods. Nonwelded and bedded tuffs were continuously cored using rotary-coring methods. Gravimetric water-content and water-potential values of core generally were greater than those of corresponding drill cuttings. Gravimetric water-content, porosity, and water-potential values of samples generally decreased, and bulk density values increased, as the degree of welding increased. Grain-density values remained fairly constant with changes in the degree of welding. A high degree of spatial variability in water-content and water-potential profiles was noted in closely spaced boreholes that penetrate similar lithologic subunits and was also noted in adjacent boreholes located in different topographic positions. Variability within a thick lithologic unit usually was small. 18 refs., 21 figs., 17 tabs.

  15. Holocene debris flows on the Colorado Plateau: The influence of clay mineralogy and chemistry

    USGS Publications Warehouse

    Webb, R.H.; Griffiths, P.G.; Rudd, L.P.

    2008-01-01

    Holocene debris flows do not occur uniformly on the Colorado Plateau province of North America. Debris flows occur in specific areas of the plateau, resulting in general from the combination of steep topography, intense convective precipitation, abundant poorly sorted material not stabilized by vegetation, and the exposure of certain fine-grained bedrock units in cliffs or in colluvium beneath those cliffs. In Grand and Cataract Canyons, fine-grained bedrock that produces debris flows contains primarily single-layer clays - notably illite and kaolinite - and has low multilayer clay content. This clay-mineral suite also occurs in the colluvium that produces debris flows as well as in debris-flow deposits, although unconsolidated deposits have less illite than the source bedrock. We investigate the relation between the clay mineralogy and major-cation chemistry of fine-grained bedrock units and the occurrence of debris flows on the entire Colorado Plateau. We determined that 85 mapped fine-grained bedrock units potentially could produce debris flows, and we analyzed clay mineralogy and major-cation concentration of 52 of the most widely distributed units, particularly those exposed in steep topography. Fine-grained bedrock units that produce debris flows contained an average of 71% kaolinite and illite and 5% montmorillonite and have a higher concentration of potassium and magnesium than nonproducing units, which have an average of 51% montmorillonite and a higher concentration of sodium. We used multivariate statistics to discriminate fine-grained bedrock units with the potential to produce debris flows, and we used digital-elevation models and mapped distribution of debris-flow producing units to derive a map that predicts potential occurrence of Holocene debris flows on the Colorado Plateau. ?? 2008 Geological Society of America.

  16. A Detailed Study of Debris Flow Source Areas in the Northern Colorado Front Range.

    NASA Astrophysics Data System (ADS)

    Arana-Morales, A.; Baum, R. L.; Godt, J.

    2014-12-01

    Nearly continuous, heavy rainfall occurred during 9-13 September 2013 causing flooding and widespread landslides and debris flows in the northern Colorado Front Range. Whereas many recent studies have identified erosion as the most common process leading to debris flows in the mountains of Colorado, nearly all of the debris flows mapped in this event began as small, shallow landslides. We mapped the boundaries of 415 September 2013 debris flows in the Eldorado Springs and Boulder 7.5-minute quadrangles using 0.5-m-resolution satellite imagery. We characterized the landslide source areas of six debris flows in the field as part of an effort to identify what factors controlled their locations. Four were on a dip slope in sedimentary rocks in the Pinebrook Hills area, near Boulder, and the other two were in granitic rocks near Gross Reservoir. Although we observed no obvious geomorphic differences between the source areas and surrounding non-landslide areas, we noted several characteristics that the source areas all had in common. Slopes of the source areas ranged from 28° to 35° and most occurred on planar or slightly concave slopes that were vegetated with grass, small shrubs, and sparse trees. The source areas were shallow, irregularly shaped, and elongated downslope: widths ranged from 4 to 9 m, lengths from 6 to 40 m and depths ranged from 0.7 to 1.2 m. Colluvium was the source material for all of the debris flows and bedrock was exposed in the basal surface of all of the source areas. We observed no evidence for concentrated surface runoff upslope from the sources. Local curvature and roughness of bedrock and surface topography, and depth distribution and heterogeneity of the colluvium appear to have controlled the specific locations of these shallow debris-flow source areas. The observed distribution and characteristics of the source areas help guide ongoing efforts to model initiation of the debris flows.

  17. High frequency space and time temperature observations for the monitoring of soil water content in a clay-rich subsoil

    NASA Astrophysics Data System (ADS)

    Gance, Julien; Malet, Jean-Philippe; Sailhac, Pascal; Malet, Florian; Marc, Vincent

    2015-04-01

    The tracing of water infiltration and the monitoring of soil water content at high spatial and temporal frequency in the vadose zone is a key element of various hydrological, agronomical, ecological and environmental studies. In this work, we evaluate the ability of soil temperature monitoring for the quantification of soil water content changes for a heterogeneous clay-rich soil. A Distributed Temperature Sensing system (AP Sensing) constituted of a datalogger, 250 m of reinforced fiber optic cable buried at 0.1, 0.2 and 0.3 m of depth and at the soil surface along a 60 m profile is used. The monitoring site is the Draix-Bleone catchment in the South French Alps, mainly composed of weathered clay-shales. The monitoring profile crosses three different soil units consisting of argillaceous weathered black marls, silty colluvium under grass and silty colluvium under forest. Soil temperature is measured every 6 minutes at a spatial resolution of 0.5 m. We show that the spatial and temporal variation, although first linked to the air temperature variations are related at the second order to the occurrence of rainfall events. The spatial and temporal evolution of the temperature in the subsoil is governed by the heat equation which involve soil thermal properties (such as thermal diffusivity). These properties are themselves affected by the soil water content. The processing of the temperature data therefore consists in inverting the soil water content that impacts the soil thermal properties such as the temperature computed from the heat equation fit the measured data. The changes of soil temperature and soil water content for the three units are compared for a period of four months. They indicate different processes of water infiltration at different velocities in relation to the presence of roots and the soil permeability. This indirect measurement technique is promising for the future; some limitations in the measurements are also discussed.

  18. Mayan urbanism: impact on a tropical karst environment.

    PubMed

    Deevey, E S; Rice, D S; Rice, P M; Vaughan, H H; Brenner, M; Flannery, M S

    1979-10-19

    From the first millennium B.C. through the 9th-century A.D. Classic Maya collapse, nonurban populations grew exponentially, doubling every 408 years, in the twin-lake (Yaxha-Sacnab) basin that contained the Classic urban center of Yaxha. Pollen data show that forests were essentially cleared by Early Classic time. Sharply accelerated slopewash and colluviation, amplified in the Yaxha subbasin by urban construction, transferred nutrients plus calcareous, silty clay to both lakes. Except for the urban silt, colluvium appearing as lake sediments has a mean total phosphorus concentration close to that of basin soils. From this fact, from abundance and distribution of soil phosphorus, and from continuing post-Maya influxes (80 to 86 milligrams of phosphorus per square meter each year), which have no other apparent source, we conclude that riparian soils are anthrosols and that the mechanism of long-term phosphorus loading in lakes is mass transport of soil. Per capita deliveries of phosphorus match physiological outputs, approximately 0.5 kilogram of phosphorus per capita per year. Smaller apparent deliveries reflect the nonphosphatic composition of urban silt; larger societal outputs, expressing excess phosphorus from deforestation and from food waste and mortuary disposal, are probable but cannot be evaluated from our data. Eutrophication is not demonstrable and was probably impeded, even in less-impacted lakes, by suspended Maya silt. Environmental strain, the product of accelerating agroengineering demand and sequestering of nutrients in colluvium, developed too slowly to act as a servomechanism, damping population growth, at least until Late Classic time.

  19. A comparative analysis of hazard models for predicting debris flows in Madison County, VA

    USGS Publications Warehouse

    Morrissey, Meghan M.; Wieczorek, Gerald F.; Morgan, Benjamin A.

    2001-01-01

    During the rainstorm of June 27, 1995, roughly 330-750 mm of rain fell within a sixteen-hour period, initiating floods and over 600 debris flows in a small area (130 km2) of Madison County, Virginia. Field studies showed that the majority (70%) of these debris flows initiated with a thickness of 0.5 to 3.0 m in colluvium on slopes from 17 o to 41 o (Wieczorek et al., 2000). This paper evaluated and compared the approaches of SINMAP, LISA, and Iverson's (2000) transient response model for slope stability analysis by applying each model to the landslide data from Madison County. Of these three stability models, only Iverson's transient response model evaluated stability conditions as a function of time and depth. Iverson?s model would be the preferred method of the three models to evaluate landslide hazards on a regional scale in areas prone to rain-induced landslides as it considers both the transient and spatial response of pore pressure in its calculation of slope stability. The stability calculation used in SINMAP and LISA is similar and utilizes probability distribution functions for certain parameters. Unlike SINMAP that only considers soil cohesion, internal friction angle and rainfall-rate distributions, LISA allows the use of distributed data for all parameters, so it is the preferred model to evaluate slope stability over SINMAP. Results from all three models suggested similar soil and hydrologic properties for triggering the landslides that occurred during the 1995 storm in Madison County, Virginia. The colluvium probably had cohesion of less than 2KPa. The root-soil system is above the failure plane and consequently root strength and tree surcharge had negligible effect on slope stability. The result that the final location of the water table was near the ground surface is supported by the water budget analysis of the rainstorm conducted by Smith et al. (1996).

  20. A mass balance model for the hydrologic response of fine-grained hillside soils to rainfall

    SciTech Connect

    Haneberg, W.C. . New Mexico Bureau of Mines and Mineral Resources)

    1992-01-01

    For a sloping soil layer of uniform thickness D, length L, and angle of inclination B, slope-normal influx per unit breadth is given by Q[sub in] = R L cos B, where R is net recharge. Slope-parallel discharge is given by Q[sub out] = K D sin B, where K is saturated hydraulic conductivity. If the long-term ratio of discharge to influx is > 1, then the slope is self-draining. If the ratio is < 1, then the slope is self-filling. Self-filling slopes will be more susceptible to failure because they cannot easily dissipate infiltration-induced pore pressure increases. For time-variant recharge, the rate of change in volumetric soil moisture content is given by d[Theta]/dt = (R/D) cos B--(K/L) sin B. Calculations using data from a thin colluvium landslide along the Ohio River give an average annual steady-state value of Q[sub out]/Q[sub in] = 1.06. A finite difference solution of the transient mass balance equation agrees fairly well with observed daily mean pressure heads from spring 1988. Stochastic simulations using temporally uncorrelated rainfall distributions fitted to the observed data tend to produce smoother hydrographs than simulations using observed rainfall values. This is due to a mismatch between the observed and fitted distributions, which caused the frequency of large storms to be underestimated and the frequency of small storms to be overestimated. Long-term trends in the stochastic simulations, however, were self-draining in three out of five trials. The mildly self-draining nature of thin colluvium hillsides along the Ohio River may explain why these slopes are marginally stable to unstable, and the general agreement between observed and simulated values suggests that mass balance models may be useful for assessing the susceptibility of hillside soils to precipitation-induced landsliding.

  1. Soils of Walker Branch Watershed

    SciTech Connect

    Lietzke, D.A.

    1994-01-01

    The soil survey of Walker Branch Watershed (WBW) utilized the most up-to-date knowledge of soils, geology, and geohydrology in building the soils data base needed to reinterpret past research and to begin new research in the watershed. The soils of WBW were also compared with soils mapped elsewhere along Chestnut Ridge on the Oak Ridge Reservation to (1) establish whether knowledge obtained elsewhere could be used within the watershed, (2) determine whether there were any soils restricted to the watershed, and (3) evaluate geologic formation lateral variability. Soils, surficial geology, and geomorphology were mapped at a scale of 1:1200 using a paper base map having 2-ft contour intervals. Most of the contours seemed to reasonably represent actual landform configurations, except for dense wooded areas. For example, the very large dolines or sinkholes were shown on the contour base map, but numerous smaller ones were not. In addition, small drainageways and gullies were often not shown. These often small but important features were located approximately as soil mapping progressed. WBW is underlain by dolostones of the Knox Group, but only a very small part of the surface area contains outcroppings of rock and most outcrops were located in the lower part. Soil mapping revealed the presence of both ancient alluvium and ancient colluvium deposits, not recognized in previous soil surveys, that have been preserved in high-elevation stable portions of present-day landforms. An erosional geomorphic process of topographic inversion requiring several millions of years within the Pleistocene is necessary to bring about the degree of inversion that is expressed in the watershed. Indeed, some of these ancient alluvial and colluvial remnants may date back into the Tertiary. Also evident in the watershed, and preserved in the broad, nearly level bottoms of dolines, are multiple deposits of silty material either devoid or nearly devoid of coarse fragments. Recent research

  2. Extreme Ground-Motion Rockfall Deposits on the Nevada Test Site

    NASA Astrophysics Data System (ADS)

    Whitney, J. W.; Buckingham, S. E.; Magner, J. E.; Finkel, R. C.; Brune, J. N.; von Seggern, D.; Honke, J. S.

    2007-12-01

    In order to detect the evidence of extreme ground motion in the past, we have begun to catalog geomorphic characteristics that distinguish slope deposits strongly influenced by extreme ground motion from deposits primarily influenced by climate processes. Underground nuclear explosions (UNEs) of yields between 200 kilotons and 1.3 megatons were conducted under Pahute Mesa at the Nevada Test site from 1962 to 1992. The primary surface effects from these tests were surface cracks, triggered earthquakes, offsets on pre-existing faults, and changes in land surface topography. Rockfall and rock spall were observed along cliffs after a few nuclear tests; however, few observations of accumulations of shattered rock were documented. A large volume of rockfall located along a 1.5-km¬-long cliff of welded ash-flow tuff resulted from extreme ground motions from two nearby UNEs. In 1968 UNE Rickey released maximum ground motions of 500 cm/s peak ground velocity (PGV) at the closest cliff face and PGV decreased to about 300 cm/s at the north end of the cliff. Large boulders with 1-3-m average diameters were shaken loose from fracture planes and cooling joints to form a stack of jumbled boulders at the base of the cliff. Very few large boulders rolled to the base of the hillslope. Subsequently, in 1976, UNE Pool induced 300-350 cm/s PGV along the same cliff. A significant volume of rock, also released along fractures and joints, was added to the coarse boulder colluvium shaken loose in 1968. Ground motion from Pool also rearranged the hillslope boulders from UNE Rickey, but did not cause many boulders to roll downslope. Extreme ground motions from these two UNEs resulted in 1.5-3.0 m of physical erosion to the cliff face. Rockfall from less welded ash-flow tuff units situated above and below the cliff produced significantly less boulder colluvium. Our observations indicate that boulder size and rockfall volume from a cliff or ridge crest due to extreme ground motion are

  3. The River Mondego terraces at the Figueira da Foz coastal area (western central Portugal): Geomorphological and sedimentological characterization of a terrace staircase affected by differential uplift and glacio-eustasy

    NASA Astrophysics Data System (ADS)

    Ramos, Anabela M.; Cunha, Pedro P.; Cunha, Lúcio S.; Gomes, Alberto; Lopes, Fernando C.; Buylaert, Jan-Pieter; Murray, Andrew S.

    2012-09-01

    A geomorphological and sedimentological characterization of the River Mondego terraces in the Figueira da Foz coastal area, Portugal, is presented. The relief is dominated by a Pliocene a marine sandy unit ~ 10-15 m thick, reaching ~ 250 m a.s.l., that covers a shore platform surface. The River Mondego has incised into the Pliocene relief and its long drainage evolution is recorded within a series of inset river terrace landforms. These river terraces are better preserved on the right-hand (northern) bank, where they form a staircase developed against the uplifted Serra da Boa Viagem structure. A set of five river terraces, represented by sedimentary deposits or erosional straths, are identified, namely: T1 at 128-125 m; T2 at 101-90 m; T3 at 70-60 m; T4 at 29-24 m; T5 at 11-10 m a.s.l. Some luminescence dating ages were obtained from the river terrace deposits: > 390 ka from the middle of T4; > 170 ka from the top of T4; ~ 120 ka from the base of T5; ~ 109 ka from T5 (average age for three samples); and 53 ± 3 ka from a colluvium at 35 m a.s.l. Some differences in altitude of the uppermost sedimentary unit and of the terraces are here interpreted as resulting from vertical displacements of active faults during the Quaternary. The main tectonic structure is the WNW-ESE trending Quiaios fault, responsible for the regional tilting towards SW. Other probably active faults and tectonic lineaments trend NNW-SSE to N-S, NNE-SSW to NE-SW and WNW-ESE. This study reports a long-term uplift rate of 0.004-0.055 m/ka for the last 3.6 Ma, but 0.017-0.118 m/ka for the last ~ 1.8 Ma (using as references, respectively, the base and the surface of the uppermost sedimentary unit). The facies associations that characterize the older terrace deposits (T1 and T2) consist of poorly sorted fluvial sandy-gravels and silts, but also some colluvium at the top of each terrace. The younger terraces (T3, T4 and T5) show better developed sedimentary structures and less sedimentary matrix; the

  4. Preliminary Geologic Map of the Thousand Oaks 7.5' Quadrangle, Southern California: A Digital Database

    USGS Publications Warehouse

    Yerkes, R.F.; Campbell, Russell H.

    1995-01-01

    -Pleistocene marine and nonmarine Pico and Saugus formations, which crop out on the southern flank of South Mountain-Oak Ridge and on the Las Posas uplands and Las Posas Hills. Locally, the Pico Formation consists of marine siltstone and silty shale with minor sandstone and pebbly sandstone. The Saugus Formation overlies and interfingers with the Pico Formation and is composed of interbedded shallow-marine to brackish water sandstone, siltstone, pebble-cobble conglomerate, and coquina beds that grade laterally and vertically into non-marine sandstone, siltstone, and conglomerate. A local member of the Saugus Formation is exposed in the southeast corner of the map area. It is predominantly a volcanic breccia conglomerate that resembles the Conejo Volcanics breccia, but is believed to represent remnants of landslide debris shed from the Conejo Formation into a local trough during Saugus time. Eroded from, and overlying, these bedrock formations are a series of recent alluvial units. These alluvial units include Quaternary alluvium comprised of alluvium, stream deposits, alluvial fan and floodplain deposits, beach deposits, dissected older alluvial deposits. Also present are Quaternary landslides and colluvium composed of landslide deposits and colluvium deposits. The colluvium represents relatively thick continuous deposits of soil and rock fragments that are common on the steep slopes of the coastal canyons, and generally feed the many landslides, soil slips, and debris flows.

  5. Preliminary Geotechnical Investigation of Two Basaltic Landslide Sites in Mauritius, Offshore Africa

    NASA Astrophysics Data System (ADS)

    Dabycharun, Bhoopendra; Kuwano, Takeshi; Ichikawa, Kensuke; Fukuoka, Hiroshi

    2016-04-01

    Landslide hazards in developing areas in Mauritius became a great challenge as well as a fundamental concern for the government and the citizen of the country. In recent years, landslide disasters have caused losses of both public and private properties. In 2005, a large-scale landslide at Chitrakoot affected 54 houses and infrastructures, and it was reactivated in 2006, damaging another 14 houses. Vallee Pitot landslide is frequently reactivated in these years and threatening several houses in densely-populated zone. Although the long-term annual precipitation show slightly decreasing trend, number of tropical cyclone over Mauritius is clearly increasing at least in the past 3 decades. Being of volcanic origin, Mauritius has observed dramatic and quick weathering of the soil which may partly contributes to creating landslide-prone geo-environment. This study focuses on the preliminary geotechnical investigation of the above-mentioned two basaltic landslide areas in Mauritius. Recent investigation was conducted jointly by JICA (Japan International Cooperation Agency) and Ministry of Public Infrastructure and Land Transport of Government of Mauritius on both sites from 2012 to 2015 to survey the landslide surface and to implement countermeasures works. In the field investigation, aerial photo interpretation was used to investigate the zone of cracks and scarps for both sites. The landslide areas for Chitrakoot and Vallee Pitot were estimated to 1.8 km2 and 5,000 m2 respectively. Both sites are located in the highly populated area in the capital city of Mauritius. The geological features of the sites were studied with the borehole core logging data obtained from 6 boreholes and it was found that possible sliding surface was observed in the colluvium layer consisting of gravels and stiff silty-clays, at depths from 6 to 10 m below the ground surface. The rate of landslide movement during heavy rainfall amount exceeding 100 mm/hr was elaborated with past records of

  6. Paleoseismic Study on the Peninsula Section of the San Andreas Fault South of Crystal Springs Reservoir, San Mateo County, California

    NASA Astrophysics Data System (ADS)

    Zachariasen, J. A.; Prentice, C. S.; Kozaci, O.; Sickler, R. R.; Baldwin, J. N.; Sanquini, A.; Knudsen, K. L.

    2010-12-01

    The Peninsula section of the San Andreas Fault is a significant hazard for the San Francisco Bay area, but little is known about the timing of earthquakes on this section of the fault prior to the great earthquake of April 18, 1906. An earthquake in 1838 resulted in strong shaking on the San Francisco Peninsula. Estimates of the magnitude of the 1838 earthquake vary from 6.8 to 7.4, based on historical accounts, and most workers have assumed that this event occurred on the San Andreas Fault. However, paleoseismic excavations across the fault near San Andreas Lake failed to provide evidence that the 1838 earthquake was associated with surface rupture on the Peninsula section of the San Andreas Fault (Prentice et al., 2008, 2009). Earlier work at the Filoli Estate, south of Crystal Springs Reservoirs, by Hall et al. (1999) suggested that both the 1838 and 1906 earthquakes ruptured the Peninsula section, based on the projected offsets of buried stream channels that crossed the fault. While this interpretation is permissible, the data also allow alternative interpretations that do not require surface rupture in 1838. We used LiDAR images produced from data collected by the GeoEarthScope project to search for promising paleoseismic sites along the Peninsula section of the San Andreas Fault. At a site about 1.2 km southeast of Crystal Springs Reservoir, we excavated two trenches across the fault and exposed fluvial gravel and overbank deposits cut by two distinct generations of faults. The younger set of faults break nearly to the ground surface, and we interpret these to represent 1906 surface faulting that has been buried post-1906 sediments. The older faults terminate below a colluvial wedge derived from one of the fluvial gravel deposits. The scarp-derived colluvium overlies a faulted fine-grained overbank deposit that in turn rests on the channel gravel, and represents the ground surface at the time of the older earthquake. The scarp-derived colluvium is overlain by

  7. Water supply for the Nuclear Rocket Development Station at the U.S. Atomic Energy Commission's Nevada Test Site

    USGS Publications Warehouse

    Young, Richard Arden

    1972-01-01

    The Nuclear Rocket Development Station, in Jackass Flats, occupies about 123 square miles in the southwestern part of the U.S. Atomic Energy Commission's Nevada Test Site. Jackass Flats, an intermontane valley bordered by highlands on all sides except for a drainage outlet in the southwestern corner, has an average annual rainfall of 4 inches. Jackass Flats is underlain by alluvium, colluvium, and volcanic rocks of Cenozoic age and, at greater depth, by sedimentary rocks of Paleozoic age. The alluvium and the colluvium lie above the saturated zone throughout nearly all of Jackass Flats. The Paleozoic sedimentary rocks contain limestone and dolomite units that are excellent water producers elsewhere ; however, these units are too deep in Jackass Flats to be economic sources of water. The only important water-producing unit known in the vicinity of the Nuclear Rocket Development Station is a welded-tuff aquifer, the Topopah Spring Member of the Paintbrush Tuff, which receives no significant recharge. This member contains about 500 feet of highly fractured rock underlying an area 11 miles long and 3 miles wide in western Jackass Flats. Permeability of the aquifer is derived mostly from joints and fractures; however, some permeability may be derived from gas bubbles in the upper part of the unit. Transmissivity, obtained from pumping tests, ranges from 68,000 to 488,000 gallons per day per foot. Volume of the saturated part of the aquifer is about 3.5 cubic miles, and the average specific yield probably ranges from 1 to 5 percent. The volume of ground water in storage is probably within the range of 37-187 billion gallons. This large amount of water should be sufficient to supply the needs of the Nuclear Rocket Development Station for many years. Water at the Nuclear Rocket Development Station is used for public supply, construction, test-cell coolant, exhaust cooling, and thermal shielding during nuclear reactor and engine testing, and washdown. Present (1967) average

  8. Fire-related debris flows in the Iberian Range, Spain

    NASA Astrophysics Data System (ADS)

    García-Ruiz, José M.; Arnáez, José; Gómez-Villar, Amelia; Ortigosa, Luis; Lana-Renault, Noemí

    2013-08-01

    Debris flows occurred three weeks after a wildfire in August 1986 in the Najerilla River valley in the Iberian Range, northern Spain. The flows were triggered by a brief, intense rainstorm (approximately 25 mm h- 1 over 15 min) in a small area with steep slopes covered by a thick colluvium of quartzite clasts. This storm resulted in the development of several unconfined hillslope debris flows and the formation of an alluvial fan at the mouth of the Pítare stream, which partially blocked the Najerilla River. We analysed the conditions that led to the development of the debris flows, and estimated the rainfall threshold for the debris flows to occur as well as the total volume of mobilised sediment. Four factors contributed to the debris flows: (i) the occurrence of a rainstorm three weeks after a wildfire, which had removed the plant cover from the soil; (ii) the steep slopes in the area (> 30°), which were the most affected by debris flows; (iii) the presence of quartzite scarps on the hillslopes, which favoured the development of a 'firehose effect' involving channelised surface runoff; and (iv) the low plasticity index values of the fine material of the colluvium (indices of 7 to 8), which enabled rapid liquefaction. Estimates of rainfall intensity derived from the estimated peak flow in the Pítare stream suggests that around 80 mm of rainfall fell in approximately 15 min, although this is clearly an overestimated value given the high proportion of sediment load transported during the peak flow. Various equations estimated a rainfall-threshold of approximately 25 mm h- 1 considering a concentration time of 15 min. The total sediment transported by the debris flows was 10,500 m3 (15,750 Mg, 6800 Mg km- 2), and the Pítare stream alone transported a minimum of 4000 m3 (6000 Mg, 2500 Mg km- 2). These results suggest that the rainfall threshold for initiating debris flows decreases following a wildfire, such that an ordinary rainstorm is able to trigger a severe

  9. Wildfire impacts on the processes that generate debris flows in burned watersheds

    USGS Publications Warehouse

    Parise, M.; Cannon, S.H.

    2012-01-01

    Every year, and in many countries worldwide, wildfires cause significant damage and economic losses due to both the direct effects of the fires and the subsequent accelerated runoff, erosion, and debris flow. Wildfires can have profound effects on the hydrologic response of watersheds by changing the infiltration characteristics and erodibility of the soil, which leads to decreased rainfall infiltration, significantly increased overland flow and runoff in channels, and movement of soil. Debris-flow activity is among the most destructive consequences of these changes, often causing extensive damage to human infrastructure. Data from the Mediterranean area and Western United States of America help identify the primary processes that result in debris flows in recently burned areas. Two primary processes for the initiation of fire-related debris flows have been so far identified: (1) runoff-dominated erosion by surface overland flow; and (2) infiltration-triggered failure and mobilization of a discrete landslide mass. The first process is frequently documented immediately post-fire and leads to the generation of debris flows through progressive bulking of storm runoff with sediment eroded from the hillslopes and channels. As sediment is incorporated into water, runoff can convert to debris flow. The conversion to debris flow may be observed at a position within a drainage network that appears to be controlled by threshold values of upslope contributing area and its gradient. At these locations, sufficient eroded material has been incorporated, relative to the volume of contributing surface runoff, to generate debris flows. Debris flows have also been generated from burned basins in response to increased runoff by water cascading over a steep, bedrock cliff, and incorporating material from readily erodible colluvium or channel bed. Post-fire debris flows have also been generated by infiltration-triggered landslide failures which then mobilize into debris flows. However

  10. Initiation and Frequency of Debris Flows in Grand Canyon, Arizona

    USGS Publications Warehouse

    Griffiths, Peter G.; Webb, Robert H.; Melis, Theodore S.

    1996-01-01

    Debris flows occur in 600 tributaries of the Colorado River in Grand Canyon, Arizona when intense precipitation causes slope failures in bedrock or colluvium. These slurries transport poorly sorted sediment, including very large boulders that form rapids at the mouths of tributaries and control the longitudinal profile of the Colorado River. Although the amount of rainfall on the days of historic debris flows typically is not unusual, the storm rainfall on consecutive days before the debris flows typically had recurrence intervals greater than 10 yrs. Four types of failure mechanisms initiate debris flows: bedrock failure (12 percent), failure of colluvial wedges by rainfall (21 percent), failure of colluvial wedges by runoff (the ?firehose effect;? 36 percent), and combinations of these failure mechanisms (30 percent). Failure points are directly or indirectly associated with terrestrial shales, particularly the Permian Hermit Shale, shale units within the Permian Esplanade Sandstone of the Supai Group, and the Cambrian Bright Angel Shale. Shales either directly fail, produce colluvial wedges downslope that contain clay, or form benches that store poorly sorted colluvium in wedge-shaped deposits. Terrestrial shales provide the fine particles and clay minerals?particularly kaolinite and illite?essential to long-distance debris-flow transport, whereas marine shales mostly contain smectites, which inhibit debris-flow initiation. Using repeat photography, we determined whether or not a debris flow occurred in the last century in 164 of 600 tributaries in Grand Canyon. We used logistic regression to model the binomial frequency data using 21 morphometric and lithologic variables. The location of shale units, particularly the Hermit Shale, within the tributary is the most consistent variable related to debris-flow frequency in Grand Canyon. Other statistically significant variables vary with large scale changes in canyon morphology. Standard morphometric measures such

  11. High permafrost ice contents in Holocene slope deposits as observed from shallow geophysics and a coring program in Pangnirtung, Nunavut, Canada

    NASA Astrophysics Data System (ADS)

    Carbonneau, A.; Allard, M.; L'Hérault, E.; LeBlanc, A.

    2011-12-01

    A study of permafrost conditions was undertaken in the Hamlet of Pangnirtung, Nunavut, by the Geological Survey of Canada (GSC) and Université Laval's Centre d'études nordiques (CEN) to support decision makers in their community planning work. The methods used for this project were based on geophysical and geomorphological approaches, including permafrost cores drilled in surficial deposits and ground penetrating radar surveys using a GPR Pulse EKKO 100 extending to the complete community area and to its projected expansion sector. Laboratory analysis allowed a detailed characterization of permafrost in terms of water contents, salinity and grain size. Cryostratigraphic analysis was done via CT-Scan imagery of frozen cores using medical imaging softwares such as Osiris. This non destructive method allows a 3D imaging of the entire core in order to locate the amount of the excess ice, determine the volumetric ice content and also interpret the ice-formation processes that took place during freezing of the permafrost. Our new map of the permafrost conditions in Pangnirtung illustrates that the dominant mapping unit consist of ice-rich colluvial deposits. Aggradationnal ice formed syngenitically with slope sedimentation. Buried soils were found imbedded in this colluvial layer and demonstrates that colluviation associated with overland-flow during snowmelt occurred almost continuously since 7080 cal. BP. In the eastern sector of town, the 1 to 4 meters thick colluviums cover till and a network of ice wedges that were revealed as spaced hyperbolic reflectors on GPR profiles. The colluviums also cover ice-rich marine silt and bedrock in the western sector of the hamlet; marine shells found in a permafrost core yielded a radiocarbon date of 9553 cal. BP which provides a revised age for the local deglaciation and also a revised marine submergence limit. Among the applied methods, shallow drilling in coarse grained permafrost, core recovery and CT-Scan allowed the

  12. The synergetic effect of moisture protection, substrate quality and biotic acclimation on soil organic carbon persistence along a cultivated loamy hillslope

    NASA Astrophysics Data System (ADS)

    Wiaux, François; Vanclooster, Marnik; Cornelis, Jean-Thomas; Van Oost, Kristof

    2014-05-01

    The combination of hydrologic, geomorphic and biogeochemical approaches is required to determine organic carbon (OC) persistence and dynamics within landscapes. Here, we used soil in-situ surface heterotrophic respiration measurement as an indicator of OC persistence along a hillslope (crop field on the loess belt under temperate climate), characterized by an important erosion-induced OC stock colluvium downslope. Along this topographical gradient, we quantified the space-time structure of soil water and temperature, and soil OC amount and quality (from a chemical point of view based on NaOCl oxidation) in relation to CO2 fluxes. We used a Generalized Least Square (GLS) regression model to identify the role of each abiotic factor as well as their interactions on observed soil respiration rates, and to calculate time-average values of these CO2 fluxes at each studied slope positions. We observed significant differences between the observed respiration rates along the topographical gradient (up to 30% more CO2 emissions downslope and 50% backslope, relative to un-eroded summit position). Despite mean CO2 fluxes (standardized at 15°C) at the bottom of the slope are significantly higher (p<0.05) than at the top of the hillslope, this difference is lower than expected given the high OC stock found downslope (c.2 times higher than at the summit position). In the cultivated loamy hillslope, the soil OC persistence is mainly controlled by the stabilizing effect of the high moisture content, implying large amount of OC. This provides evidence that soil OC dynamic (sink or source) can be mainly governed by site-specific abiotic conditions (e.g. soil moisture). On the other hand, OC found downslope was showed to be especially vulnerable for OC mineralization (it would emit 26% to c.40% more CO2 in case of temperature increase), due to both (i) improved efficiency of soil-micro-organisms in stabilizing conditions, and (ii) high quality of OC stock (easy to decompose for soil

  13. Using the accumulation of CBD-extractable iron and clay content to estimate soil age on stable surfaces and nearby slopes, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Dethier, David P.; Birkeland, Peter W.; McCarthy, James A.

    2012-11-01

    In many transport-limited environments, morphology, pedogenic iron and clay content provide a basis for estimating the exposure age of soils and associated landforms. We measured citrate-buffered dithionite (CBD)-extractable Fe (Fed) and clay concentration in fresh rock, saprolite, morainal and colluvial materials, and soil horizons from stable surfaces and hillslopes in the Colorado Front Range. Fresh igneous and high-grade metamorphic rocks contain < 1% Fed and 1 to 5% clay. As bedrock and surficial deposits age, Fed and clay accumulate from weathering and dustfall. Late Holocene regolith at warm, dry sites contains small amounts of Fed and clay, but relatively moist soils developed on early Holocene cirque deposits contain as much as 1.5% Fed and 8% clay. Concentrations and total profile accumulation of Fed and clay increase with age in soils developed on stable surfaces of glacial deposits as old as ~ 130 kyr. On stable sites, Fed and clay accumulation from weathering and dust is ~ 0.02 g cm- 2 kyr- 1 and ~ 0.2 g cm- 2 kyr- 1, respectively. We used the Fed and clay inventory in soil profiles at dated, stable Front Range surfaces to calculate accumulation functions, which allowed us to estimate soil age at hillslope sites. Heterogeneous parent material, particularly on hillslopes, and climate-related effects add to variability in measured relations. Mobile regolith in Gordon Gulch, one of the Boulder Creek Critical Zone Observatory (CZO) catchments, yields profile ages from about 0.5 to 5 × 104 yr, comparable to values measured using other techniques. Calculated profile ages are older on a north- vs. south-facing slope and increase from the drainage divide to the footslope. Ages calculated for stabilized colluvium and well-developed buried profiles at nearby hillslope sites (Lefthand, Ward and Rollinsville) suggest that these soils have stabilized over periods > 105 yr. In the absence of radiometric ages, the accumulation of Fed and clay in soils on stable

  14. Syn and post- emplacement transformations of the Misti (Peru) volcanic debris avalanches into lahars

    NASA Astrophysics Data System (ADS)

    Bernard, K.; Van Wyk de Vries, B.; Thouret, J.

    2012-12-01

    We identify stratigraphic, sedimentological and structural variations in lithofacies of debris-avalanche deposits from El Misti volcano in the Quebrada San Lazaro and Río Chili Valley, near the city of Arequipa (south Peru), to determine lithofacies transformations. We describe the internal process associated to the external conditions acting on debris-avalanche deposits in order to assess stages of transformations from the proximal to distal debris-avalanche deposits and the associated epiclastic deposits. Syn-emplacement transformations inside the volcanic debris-avalanche deposits in the upper course of the Rio Chili Valley: within a few meters, the proximal block facies of the sheared debris-avalanche deposit is transformed at the contact of the ash-rich alluvial deposits in thick units comprising a strongly sheared base of the deposit, then stratified matrix dominated beds with normally sorted boulders aligned with the beds. This is interpreted as the effect of strong shearing inside the confined and proximal debris avalanche during motion, which generated a localised stretching near the base of the deposit and the bulking of the thin water saturated basal layers: the bearing capacity of the matrix debris- avalanche is modified, the block facies has been transformed in a stratified matrix facies. The transformations by bulking along a strong sheared contact contribute to reduce the run-out distance of the debris avalanches in the Río Chili valley. Post-deposition evolutions of the debris-avalanche deposits in the Quebrada San Lazaro: in the upper course of the valley, the landslides in the debris- avalanche deposits related to water circulation destabilise the covering scree and volcanic colluvium dipping at 70°. The fragmentation and sorting due to gravity and water are the external processes which separate matrix and block elements; This is the first stage of transformation. The remobilisation of these separated fractions into lahars transforms this

  15. Detection of early stage large scale landslides in forested areas by 2 m LiDAR DEM analysis. The example of Portainé (Central Pyrenees)

    NASA Astrophysics Data System (ADS)

    Guinau, Marta; Ortuño, Maria; Calvet, Jaume; Furdada, Glòria; Bordonau, Jaume; Ruiz, Antonio; Camafort, Miquel

    2016-04-01

    Mass movements have been classically detected by field inspection and air-photo interpretation. However, airborne LiDAR has significant potential for generating high-resolution digital terrain models, which provide considerable advantages over conventional surveying techniques. In this work, we present the identification and characterization of six slope failures previously undetected in the Orri massif, at the core of the Pyrenean range. The landforms had not been previously detected and were identified by the analysis of high resolution 2 m LiDAR derived bared earth topography. Most of the scarps within these failures are not detectable by photo interpretation or the analysis of 5 m resolution topographic maps owing to their small heights (ranging between 0.5 and 2 m) and their location within forest areas. 2D and 3D visualization of hillshade maps with different sun azimuths, allowed to obtain the overall picture of the scarp assemblage and to analyze the geometry and location of the scarps with respect to the slope and the structural fabric. Near 120 scarps were mapped and interpreted as part of slow gravitational deformation, incipient slow flow affecting a colluvium, rotational rock-sliding and slope creep. Landforms interpreted as incipient slow flow affecting a colluvium have headscarps with horse-shoe shape and superficial (< 20 m) basal planes whereas sackung features have open headscarps and basal planes that are likely located at 200-250 m maximum depth. Other distinctive features are toppling or extensive scarps, double ridges and rock rotational landslides. The sharpness of the scarps suggests their recent activity, which may pose a potential risk for the Port-Ainé sky resort users and facilities. These results suggest that the systematic analysis of 2 m LIDAR derived bared earth topography would significantly help in the rapid detection and mapping of early stage slope deformations in high mountain areas, which could contribute to 1) a better

  16. The Influence of The Geological and Geomorphological Settings On The Shallow Landslides Triggered During The 19th June, 1996 Heavy Rainfalls In Southern Apuan Alps (italy)

    NASA Astrophysics Data System (ADS)

    D'Amato Avanzi, G.; Giannecchini, R.; Puccinelli, A.

    On June the 19th, 1996 many disastrous shallow landslides (nearly 700) occurred in the southern Apuan Alps (Tuscany, Italy) as a consequence of an exceptionally heavy rainstorm (474 mm/12 hours). Here, the results of the studies on the landslides oc- curred in the most severely damaged basins (Cardoso, Mulina and Turrite di Galli- cano torrents) are summarized. The most significant parameters of the landslides were analysed, to identify the factors which most influenced their activation. Moreover, the total amount of mobilized material was estimated. The most common type of landslide movement was complex, from very to extremely rapid, debris slide-debris flow, with a high length to breadth ratio. Most of them were probably first time landslides; ca. 90% of them involved the colluvium cover of slopes. The studies in the landslide sites also highlighted many geomorphically and geologically recurrent factors, summarized be- low. 85% of landslides occurred on rather steep slopes (30-45), in first-order basins and hollows. In these situations, the concave geometry of the colluvium/bedrock inter- face favoured the convergence of groundwater flow and the build-up of pore pressure, leading to failure. In landslide sites, a concave shape of the surface and a rectilinear profile of the slope were a frequent feature. The bedrock of landslide sites was gener- ally made up of impervious or scarcely pervious rocks. In many cases, the presence of a main discontinuity in the bedrock (bedding or schistosity) dipping downslope was significant. The total surface involved in landslides of June 19, 1996 was estimated at ca. 1 Km2, 2.2% of the basins surface. More than 80% of this surface was covered by chestnut trees: thus, ca. 7,000 chestnut trees were uprooted by the landslides and fell into the riverbeds. This significantly contributed to the extensive destruction and blockage of bridge spans. The total volume of mobilized material was estimated at ca. 1,350,000 m3: most of this

  17. Geology of five small Australian impact craters

    USGS Publications Warehouse

    Shoemaker, E.M.; Macdonald, F.A.; Shoemaker, C.S.

    2005-01-01

    Here we present detailed geological maps and cross-sections of Liverpool, Wolfe Creek, Boxhole, Veevers and Dalgaranga craters. Liverpool crater and Wolfe Creek Meteorite Crater are classic bowlshaped, Barringer-type craters, Liverpool was likely formed during the Neoproterozoic and was filled and covered with sediments soon thereafter. In the Cenozoic, this cover was exhumed exposing the crater's brecciated wall rocks. Wolfe Creek Meteorite Crater displays many striking features, including well-bedded ejecta units, crater-floor faults and sinkholes, a ringed aeromagnetic anomaly, rim-skirting dunes, and numerous iron-rich shale balls. Boxhole Meteorite Crater, Veevers Meteorite Crater and Dalgaranga crater are smaller, Odessa-type craters without fully developed, steep, overturned rims. Boxhole and Dalgaranga craters are developed in highly follated Precambrian basement rocks with a veneer of Holocene colluvium. The pre-existing structure at these two sites complicates structural analyses of the craters, and may have influenced target deformation during impact. Veevers Meteorite Crater is formed in Cenozoic laterites, and is one of the best-preserved impact craters on Earth. The craters discussed herein were formed in different target materials, ranging from crystalline rocks to loosely consolidated sediments, containing evidence that the impactors struck at an array of angles and velocities. This facilitates a comparative study of the influence of these factors on the structural and topographic form of small impact craters. ?? Geological Society of Australia.

  18. Using a 2.5D Electrical Resistivity Imaging Method for Locating the House Remnants and Possible Landslide Victims of Typhoon Morak

    NASA Astrophysics Data System (ADS)

    Chang, S.; Chang, P.; Chen, H.; Jan, P.

    2009-12-01

    The Typhoon Morak hits Taiwan on August 8th, 2009, and pours huge amount of precipitation (over 2000 mm in just three days) into the southern part of the island. The heavy precipitation induces many landslides in the mountain area and costs over 500 deaths. To help searching the remnants of the buildings and possible victims that may be buried under the buildings, we utilized the 2.5D electrical resistivity tomography (2.5D) technique in one landslide location near the Baolai village area in the Kaohsiung County. A family of 5 was reported missing in the landslide and only parts of the bodies were recovered in the rescue mission. We conducted 2.5D electrical resistivity tomography in two possible areas marked by the rescue team along four 20-meter long parallel lines. The remnants of the house and bodies were believed to be buried under the thick colluvium sediments. To search for possible anomalies from these man-made objects, we chose dipole-dipole method and the 0.5-m electrode spacing for the survey.

  19. Analyzing debris flows with the statistically calibrated empirical model LAHARZ in southeastern Arizona, USA

    USGS Publications Warehouse

    Magirl, Christopher S.; Griffiths, Peter G.; Webb, Robert H.

    2010-01-01

    Hazard-zone delineation for extreme events is essential for floodplain management near mountain fronts in arid and semiarid regions. On 31 July 2006, unprecedented debris flows occurred in the Santa Catalina Mountains of southeastern Arizona following extreme multiday precipitation (recurrence interval > 1000 years for 4-day precipitation). Most mobilized sediment contributing to debris flows was derived from shallow-seated failures of colluvium on steep slopes. A total of 435 slope failures in the southern Santa Catalina Mountains released 1.34 million Mg of sediment into the channels of 10 drainage basins. Five drainages produced debris flows that moved to the apices of alluvial fans on the southern edge of the mountain front, damaging infrastructure and aggrading channels to reduce future flood conveyance. Using the statistically calibrated, empirical debris-flow model LAHARZ and modified model coefficients developed to better match conditions in southeastern Arizona, we predicted the approximate area of deposition and travel distance in comparison to observed depositional areas and travel distance for seven debris flows. Two of the modeled debris flows represented single slope failures that terminated downslope with no additive influence of other debris flows or streamflow flooding. Five of the simulated debris flows represented the aggregation of multiple slope failures and streamflow flooding into multiple debris-flow pulses. Because LAHARZ is a debris-flow hazard-zone delineation tool, the complexity of alternating transport and deposition zones in channels with abrupt expansions and contractions reduces the applicability of the model in some drainage basins.

  20. Constraining the Origin of Basaltic Volcanic Rocks Observed by Opportunity Along the Rim of Endeavour Crater

    NASA Technical Reports Server (NTRS)

    Bouchard, M. C.; Jolliff, B. L.; Farrand, W. H.; Mittlefehldt, D. W.

    2017-01-01

    The Mars Exploration Rover (MER) Opportunity continues its exploration along the rim of Endeavour Crater. While the primary focus for investigation has been to seek evidence of aqueous alteration, Opportunity has observed a variety of rock types, including some that are hard and relatively unaltered. These rocks tend to occur most commonly as "float rocks" or "erratics" where the geologic setting does not clearly reveal their origin. Along the rim of Endeavour crater (Fig. 1), such rocks, commonly noted in Panoramic Camera (Pancam) left eye composites as "blue rocks", are abundant components of some of the Endeavour crater rim deposits, scree slopes, and colluvium deposits. In this abstract, we examine the similarity of several of these rocks analyzed using Opportunity's Alpha Particle X-Ray Spectrometer (APXS), images and color from the Pancam, and textures observed with the Microscopic Imager (MI. At issue is the blue rocks origin; are they impact melt or volcanic, what is their age relative to Endeavour crater, and how they are related to each other?

  1. Roman, Visigothic and Islamic evidence of earthquakes recorded in the archaeological site of “El Tolmo de Minateda” (Prebetic Zone, southeast of Spain)

    USGS Publications Warehouse

    Rodríguez-Pascua, M.A.; Abad Casal, L.; Pérez-López, R.; Gamo Parra, B.; Silva, P.G.; Garduño-Monroy, V.H.; Giner-Robles, J.L.; Perucha, M.A.; Israde-Alcántara, I.; Bischoff, J.; Calvo, J.P.

    2013-01-01

    The archaeological site of “El Tolmo de Minateda” is located within the Albacete province (SE of Spain) and shows a continuous time record of ancient civilizations from 3500 yr BP onwards. However, three temporal gaps were identified in this archaeological record, all of them in relationship with a sudden and unclear abandonment of the city (Centuries 1st, 7th and 9-10th). The Archaeological Earthquake Effects (EAEs) supports the possibility that moderate to strong earthquakes were the cause of such abandonments: oriented columns fallen, collapsed walls and arches, abandonment of irrigation systems and fresh-water supplies, crashed pottery, etc. Despite of the scarce of instrumental seismicity and a few historical chronicles, paleoseismic studies performed in the neighbouring zone (Tobarra) suggest the presence of closer seismic sources as faults (Pozohondo Fault) affecting Quaternary alluvial, lacustrine deposits and colluviums. In this work, we propose the possibility that three moderate earthquakes devastated the ancient Roman city of Ilunum (Century 1st AD), the Visigothic city of Elo (Century 7th AD) and the Islamic city of Madinat Iyih (Century 9th-10thAD), all of them the same place: “El Tolmo de Minateda”.

  2. Infinite slope stability under steady unsaturated seepage conditions

    USGS Publications Warehouse

    Lu, N.; Godt, J.

    2008-01-01

    [1] We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework. Copyright 2008 by the American Geophysical Union.

  3. Natural versus anthropogenic genesis of mardels (closed depressions) on the Gutland plateau (Luxembourg); archaeometrical and palynological evidence of Roman clay excavation from mardels.

    NASA Astrophysics Data System (ADS)

    van Mourik, Jan; Braekmans, Dennis; Doorenbosch, Marieke; Kuijper, Wim; van der Plicht, Hans

    2016-04-01

    Mardels, small closed depressions, are distinctive landforms on the Luxembourger Gutland plateau. In the present landscape most mardels are shallow fens, filled with colluvial sediments. The genesis of mardels has been studied intensively, inside and outside Luxembourg. Some researchers suggested a natural development and consider mardels as subsidence basins due to subsurface solution of gypsum veins, other researchers suggested cultural causes and consider mardels as prehistorical quarries. In the Gutland, mardels occur on various substrates. Mardels on the Strassen marls (li3) are abandoned quarries, related to clay excavation in Roman Time. Mardels on the Luxembourger sandstone (li2) are sinkholes, related to joint patterns in the sandstone formation. Mardels on the Keuper marls (km1,3) are originally subsidence basins, related to subsurface dissolutions of gypsum lenses and veins, filled with colluvial clay. The results of pollen analysis and archaeometrical tests demonstrate Roman extraction of clay for the production of ancient ceramics. So, the natural depressions have been enlarged to the present mardels. After excavation, the sedimentation of colluvium restarted in the abandoned quarries.

  4. Infinite slope stability under steady unsaturated seepage conditions

    NASA Astrophysics Data System (ADS)

    Lu, Ning; Godt, Jonathan

    2008-11-01

    We present a generalized framework for the stability of infinite slopes under steady unsaturated seepage conditions. The analytical framework allows the water table to be located at any depth below the ground surface and variation of soil suction and moisture content above the water table under steady infiltration conditions. The framework also explicitly considers the effect of weathering and porosity increase near the ground surface on changes in the friction angle of the soil. The factor of safety is conceptualized as a function of the depth within the vadose zone and can be reduced to the classical analytical solution for subaerial infinite slopes in the saturated zone. Slope stability analyses with hypothetical sandy and silty soils are conducted to illustrate the effectiveness of the framework. These analyses indicate that for hillslopes of both sandy and silty soils, failure can occur above the water table under steady infiltration conditions, which is consistent with some field observations that cannot be predicted by the classical infinite slope theory. A case study of shallow slope failures of sandy colluvium on steep coastal hillslopes near Seattle, Washington, is presented to examine the predictive utility of the proposed framework.

  5. Geohydrology of Monitoring Wells Drilled in Oasis Valley near Beatty, Nye County, Nevada, 1997

    USGS Publications Warehouse

    Robledo, Armando R.; Ryder, Philip L.; Fenelon, Joseph M.; Paillet, Frederick L.

    1999-01-01

    Twelve monitoring wells were installed in 1997 at seven sites in and near Oasis Valley, Nevada. The wells, ranging in depth from 65 to 642 feet, were installed to measure water levels and to collect water-quality samples. Well-construction data and geologic and geophysical logs are presented in this report. Seven geologic units were identified and described from samples collected during the drilling: (1) Ammonia Tanks Tuff; (2) Tuff of Cutoff Road; (3) tuffs, not formally named but informally referred to in this report as the 'tuff of Oasis Valley'; (4) lavas informally named the 'rhyolitic lavas of Colson Pond'; (5) Tertiary colluvial and alluvial gravelly deposits; (6) Tertiary and Quaternary colluvium; and (7) Quaternary alluvium. Water levels in the wells were measured in October 1997 and February 1998 and ranged from about 18 to 350 feet below land surface. Transmissive zones in one of the boreholes penetrating volcanic rock were identified using flowmeter data. Zones with the highest transmissivity are at depths of about 205 feet in the 'rhyolitic lavas of Colson Pond' and 340 feet within the 'tuff of Oasis Valley.'

  6. Geologic Map of the Round Spring Quadrangle, Shannon County, Missouri

    USGS Publications Warehouse

    Orndorff, Randall C.; Weary, David J.

    2009-01-01

    The Round Spring 7.5-minute quadrangle is located in Shannon County, south-central Missouri on the Salem Plateau of the Ozark Plateaus physiographic province. As much as 1,350 feet (ft) of flat-lying to gently dipping Upper Cambrian and Lower Ordovician rocks, mostly dolomite, overlie Mesoproterozoic volcanic rocks. The bedrock is overlain by unconsolidated residuum, colluvium, terrace deposits, and alluvium. Karst features, such as small sinkholes and caves, have formed in the carbonate rocks, and many streams are spring fed. The topography is a dissected karst plain with elevation ranging from 650 ft along the Current River on the eastern edge of the quadrangle to almost 1,200 ft at various places on the ridge tops. The area is mostly forested but contains some farmlands and includes sections of the Ozark National Scenic Riverways of the National Park Service along the Current River. Geologic mapping for this investigation began in the spring of 2001 and was completed in the spring of 2002.

  7. Reconstructing paleo- and initial landscapes using a multi-method approach in hummocky NE Germany

    NASA Astrophysics Data System (ADS)

    van der Meij, Marijn; Temme, Arnaud; Sommer, Michael

    2016-04-01

    The unknown state of the landscape at the onset of soil and landscape formation is one of the main sources of uncertainty in landscape evolution modelling. Reconstruction of these initial conditions is not straightforward due to the problems of polygenesis and equifinality: different initial landscapes can change through different sets of processes to an identical end state. Many attempts have been done to reconstruct this initial landscape. These include remote sensing, reverse modelling and the usage of soil properties. However, each of these methods is only applicable on a certain spatial scale and comes with its own uncertainties. Here we present a new framework and preliminary results of reconstructing paleo-landscapes in an eroding setting, where we combine reverse modelling, remote sensing, geochronology, historical data and present soil data. With the combination of these different approaches, different spatial scales can be covered and the uncertainty in the reconstructed landscape can be reduced. The study area is located in north-east Germany, where the landscape consists of a collection of small local depressions, acting as closed catchments. This postglacial hummocky landscape is suitable to test our new multi-method approach because of several reasons: i) the closed catchments enable a full mass balance of erosion and deposition, due to the collection of colluvium in these depressions, ii) significant topography changes only started recently with medieval deforestation and recent intensification of agriculture and iii) due to extensive previous research a large dataset is readily available.

  8. Paleoseismology of a newly discovered scarp in the Yakima fold-and-thrust belt, Kittitas County, Washington

    USGS Publications Warehouse

    Barnett, Elizabeth A.; Sherrod, Brian L.; Norris, Robert; Gibbons, Douglas

    2013-01-01

    The Boylston Mountains anticlinal ridge is one of several that are cored by rocks of the Columbia River Basalt Group and, with the interceding synclinal valleys, constitute the Yakima fold-and-thrust belt of central Washington. Lidar data acquired from the U.S. Army's Yakima Training Center reveal a prominent, northwest-side-up, 65°- to 70°-trending, 3- to 4-meter-high scarp that cuts across the western end of the Boylston Mountains, perpendicular to the mapped anticline. The scarp continues to the northeast from the ridge on the southern side of Park Creek and across the low ridges for a total length of about 3 kilometers. A small stream deeply incises its flood plain where it projects across Johnson Canyon. The scarp is inferred to be late Quaternary in age based on its presence on the modern landscape and the incised flood-plain sediments in Johnson Canyon. Two trenches were excavated across this scarp. The most informative of the two, the Horned Lizard trench, exposed shallow, 15.5-Ma Grande Ronde Basalt, which is split by a deep, wide crack that is coincident with the base of the scarp and filled with wedges of silty gravels that are interpreted to represent at least two generations of fault colluvium that offset a buried soil.

  9. The impact of glacial/interglacial climate changes on fluvial and mass-wasting processes in the Taiwan's mountains

    NASA Astrophysics Data System (ADS)

    Li, W. L.; Hsieh, M. L.; Tsui, H. K.; Hsiao, Y. T.

    2014-12-01

    The Taiwan orogenic belt, located in Southeastern Asia, is under monsoon climate, frequently attacked by tropical typhoons, and characterized by rapid tectonic uplift with high seismicity. Researchers have been linking the Taiwan's landscapes to active tectonic uplift. In this study, we show the significance of glacial/interglacial climate changes in shaping the landscapes. We focus on the mountain areas that have never been glaciated. Based on >400 radiocarbon dates (70 of which >12 ka), we find that both the slope and fluvial activities were generally low during the glacial time. Still, extensive alluviation had occurred at certain time periods, forming large debris slopes or alluvial fans (typically along mountain fronts), and causing significant aggradation along some major rivers. In contrast, with numerous landslides and debris flows, river incision has dominated during the postglacial time. Episodic river aggradation with alluvial-terrace development (typically at tributary mouths) also occurred during this time period, but was less extensive than previously. Some huge postglacial alluvial terraces have been proved sourced from the colluviums deposited in the glacial time. We attribute the low landscape activities of the glacial period to the dryness during the period. However, even in this time rare but severe rainfall events must have occurred to trigger some extensive alluviation. In contrast, the increase in both rainfall and typhoon frequency during the postglacial time drastically increased the slope instability and sediment yield. The great stream power, along with the sufficient coarse debris acting as erosion tools, ensured the rapid river incision during this time.

  10. Large quaternary landslides in the central appalachian valley and ridge province near Petersburg, West Virginia

    USGS Publications Warehouse

    Scott, Southworth C.

    1988-01-01

    Geological mapping and photointerpretation of side-looking airborne radar images and color-infrared aerial photographs reveal two large Quaternary landslides in the Valley and Ridge province of the central Appalachians near Petersburg, W. Va. The Elkhorn Mountain rock avalanche occurs on the thrust-faulted northwestern flank of the Elkhorn Mountain anticlinorium. A minimum of 7 ?? 106 m3 of quartzite colluvium was transported more than 3 km from a 91 m high escarpment of Silurian Tuscarora Quartzite. The extensively vegetated deposit may owe, in part, its transport and weathering to periglacial conditions during the Pleistocene. In contrast, the Gap Mountain rock block slide is a single allochthonous block that is 1.2 km long, 0.6 km wide, and at least 60 m thick. The 43 ?? 106 m3 block is composed of limestone of the Helderberg Group and the Oriskany Sanstone of Early Devonian age. Planar detachment probably occurred along a dissolution bedding plane near the Shriver Chert and the Oriskany Sandstone contact. Failure probably was initiated by downcutting of the South Branch Potomac River during the Pleistocene. Landslides of this magnitude suggest accelerated erosion during periglacial climates in the Pleistocene. The recognition of these large slope failures may provide evidence of paleoclimatic conditions and, thereby, increase our understanding of the geomorphologic development of the Valley and Ridge province. ?? 1988.

  11. Geochemical and C, O, Sr, and U-series isotopic evidence for the meteoric origin of calcrete at Solitario Wash, Crater Flat, Nevada, USA

    USGS Publications Warehouse

    Neymark, L.A.; Paces, J.B.; Marshall, B.D.; Peterman, Z.E.; Whelan, J.F.

    2005-01-01

    Calcite-rich soils (calcrete) in alluvium and colluvium at Solitario Wash, Crater Flat, Nevada, USA, contain pedogenic calcite and opaline silica similar to soils present elsewhere in the semi-arid southwestern United States. Nevertheless, a ground-water discharge origin for the Solitario Wash soil deposits was proposed in a series of publications proposing elevation-dependent variations of carbon and oxygen isotopes in calcrete samples. Discharge of ground water in the past would raise the possibility of future flooding in the unsaturated zone at Yucca Mountain, Nevada, site of a proposed high-level nuclear waste repository. New geochemical and carbon, oxygen, strontium, and uranium-series isotopic data disprove the presence of systematic elevation-isotopic composition relations, which are the main justification given for a proposed ground-water discharge origin of the calcrete deposits at Solitario Wash. Values of ??13C (-4.1 to -7.8 per mil [???]), ??18O (23.8-17.2???), 87Sr/ 86Sr (0.71270-0.71146), and initial 234U/238U activity ratios of about 1.6 in the new calcrete samples are within ranges previously observed in pedogenic carbonate deposits at Yucca Mountain and are incompatible with a ground-water origin for the calcrete. Variations in carbon and oxygen isotopes in Solitario Wash calcrete likely are caused by pedogenic deposition from meteoric water under varying Quaternary climatic conditions over hundreds of thousands of years. ?? Springer-Verlag 2005.

  12. Evidence for Regional Stream Aggradation in the Central Oregon Coast Range during the Pleistocene-Holocene Transition

    NASA Astrophysics Data System (ADS)

    Personius, Stephen F.; Kelsey, Harvey M.; Grabau, Paul C.

    1993-11-01

    Low, nearly continuous terraces of similar age are present along streams in drainage basins that range in size from Drift Creek (190 km 2) to the Umpqua River (11,800 km 2) in the Oregon Coast Range. Radiocarbon ages from near the bose of fluvial sediments underlying these terraces are clustered at about 9000-11,000 14C yr B.P. Beveled bedrock surfaces (straths) that underlie the fluvial sediments are 1-8 m above summer stream levels and are present along most of the nontidal reaches of the rivers that we studied. Where exposed, the bedrock straths are overlain by 2-11 m of fluvial sediment that consists of a bottom-stratum (channel) facies of sandy pebble-cobble gravel and a top-stratum (overbank) facies of sandy silt or silt. Eight radiocarbon ages from the fluvial sediments allow correlation of the lowest continuous terrace over a wide area and thus indicate that a regional aggradation episode occurred in Coast Range drainage basins during the Pleistocene-Holocene transition. The cause of such widespread aggradation is unknown but may be related to climate-induced changes in the frequency of evacuation of colluvium from hollows, which are common in all drainage basins in the region.

  13. Evidence for Regional Stream Aggradation in the Central Oregon Coast Range during the Pleistocene-Holocene Transition

    USGS Publications Warehouse

    Personius, S.F.; Kelsey, H.M.; Grabau, P.C.

    1993-01-01

    Low, nearly continuous terraces of similar age are present along streams in drainage basins that range in size from Drift Creek (190 km2) to the Umpqua River (11,800 km2) in the Oregon Coast Range. Radiocarbon ages from near the bose of fluvial sediments underlying these terraces are clustered at about 9000-11,000 14C yr B.P. Beveled bedrock surfaces (straths) that underlie the fluvial sediments are 1-8 m above summer stream levels and are present along most of the nontidal reaches of the rivers that we studied. Where exposed, the bedrock straths are overlain by 2-11 m of fluvial sediment that consists of a bottom-stratum (channel) facies of sandy pebble-cobble gravel and a top-stratum (overbank) facies of sandy silt or silt. Eight radiocarbon ages from the fluvial sediments allow correlation of the lowest continuous terrace over a wide area and thus indicate that a regional aggradation episode occurred in Coast Range drainage basins during the Pleistocene-Holocene transition. The cause of such widespread aggradation is unknown but may be related to climate-induced changes in the frequency of evacuation of colluvium from hollows, which are common in all drainage basins in the region.

  14. Flood geomorphology of Arthurs Rock Gulch, Colorado: paleoflood history

    NASA Astrophysics Data System (ADS)

    Waythomas, Christopher F.; Jarrett, Robert D.

    1994-11-01

    Episodic late Quaternary flooding is recorded by bouldery deposits and slackwater sediments along Arthurs Rock Gulch, an ephemeral stream west of Fort Collins, Colorado. Flood deposits consist of individual granodiorite and pegmatite boulders, boulder bars, and coarse overbank sediment that rest on erosional terrace segments along the channel. We identified evidence for at least five flood in the lower two thirds of the 1.84 km 2 drainage basin. Flood deposits are differentiated by their position above the active channel, weathering characteristics, degree of boulder burial by colluvium, amount of lichen cover, and position with respect to terrace and colluvial deposits. Age estimates for the flood deposits are based on radiocarbon dating, tree-ring analyses, and relative-age criteria from four sites in the basin. At least two floods occurred in the last 300 years; a third flood is at least 5000 years old, but likely younger than 10,000 yr BP; and the two oldest floods occurred at least 40,000 years BP.

  15. Identification of a Buried Late Cenozoic Maar-Diatreme Structure (North Moravia, Czech Republic)

    NASA Astrophysics Data System (ADS)

    Šešulka, Vojtěch; Sedláková, Iva; Bábek, OndŘej; PŘichystal, Antonín

    2015-01-01

    The maar-diatreme volcanic structure in the vicinity of the village of Lomnice near the town of Bruntál (North Moravia, Czech Republic) has been investigated using a set of geophysical methods including ground magnetometry, gravimetry and electrical resistivity tomography. The structure was detected by an aerial magnetic survey in the second half of the 20th century. Since its discovery only limited information about this buried structure has been available. The coherence of the magnetic anomaly of 190 nT and Bouguer anomaly of -4.7 mGal indicates a volcanic origin of the structure. The funnel-shaped maar-diatreme structure is filled with lacustrine clay and colluvium of Car-boniferous greywacke, which forms the country rock. The surface diameter of the structure is about 600 m, the depth is more than 400 m. The spatial association with other volcanic centers in the surroundings of the town of Bruntál infers the relative dating of the Lomnice maar. The phreatic eruption and maar-diatreme formation could be an indirect conse-quence of effusive activity of the nearby Velký Roudný volcano. The Lomnice structure is the first Plio-Pleistocene maar-diatreme ever described in North Moravia and Silesia.

  16. Flood geomorphology of Arthurs Rock Gulch, Colorado: paleoflood history

    USGS Publications Warehouse

    Waythomas, C.F.; Jarrett, R.D.

    1994-01-01

    Episodic late Quaternary flooding is recorded by bouldery deposits and slackwater sediments along Arthurs Rock Gulch, an ephemeral stream west of Fort Collins, Colorado. Flood deposits consist of individual granodiorite and pegmatite boulders, boulder bars, and coarse overbank sediment that rest on erosional terrace segments along the channel. We identified evidence for at least five flood in the lower two thirds of the 1.84 km2 drainage basin. Flood deposits are differentiated by their position above the active channel, weathering characteristics, degree of boulder burial by colluvium, amount of lichen cover, and position with respect to terrace and colluvial deposits. Age estimates for the flood deposits are based on radiocarbon dating, tree-ring analyses, and relative-age criteria from four sites in the basin. At least two floods occurred in the last 300 years; a third flood is at least 5000 years old, but likely younger than 10,000 yr BP; and the two oldest floods occurred at least 40,000 years BP. ?? 1994.

  17. Geologic map of the Jam Up Cave and Pine Crest quadrangles, Shannon, Texas, and Howell Counties, Missouri

    USGS Publications Warehouse

    Weary, David J.; Orndorff, Randall C.; Repetski, John E.

    2013-01-01

    The Jam Up Cave and Pine Crest 7.5-minute quadrangles are located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 2,400 to 3,100 feet (ft) of flat-lying to gently dipping Lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic igneous basement rocks. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Numerous karst features, such as sinkholes, caves, and springs, have formed in the carbonate rocks. Many streams are spring fed. The topography is a dissected karst plain with elevations ranging from about 690 ft where the Jacks Fork River exits the northeastern corner of the Jam Up Cave quadrangle to about 1,350 ft in upland areas along the north-central edge and southwestern corner of the Pine Crest quadrangle. The most prominent physiographic feature is the valley of the Jacks Fork River. This reach of the upper Jacks Fork, with its clean, swiftly-flowing water confined by low cliffs and bluffs, provides one of the most beautiful canoe float trips in the nation. Most of the land in the quadrangles is privately owned and used primarily for grazing cattle and horses and growing timber. A large minority of the land within the quadrangles is publicly owned by the Ozark National Scenic Riverways of the National Park Service. Geologic mapping for this investigation was conducted in 2005 and 2006.

  18. Saline-seep development in the Hailstone Basin, northern Stillwater County, Montana

    USGS Publications Warehouse

    Lewis, Barney D.; Custer, Stephen G.; Miller, Marvin R.

    1979-01-01

    As a result of an increase in saline seep occurrence in Montana, a study was begun in 1974 to determine the hydrogeology of saline seeps in the Hailstone basin. The aquifer is composed of colluvium of Holocene age. The impermeable Cretaceous Niobrara Formation underlies the saturated zone basinwide. The ground-water system is shallow, unconfined, and locally recharged. Ground-water levels and size of the saline seeps respond rapidly to precipitation in the basin. The appearance and growth of saline seeps are related to precipitation patterns; the agricultural practice of summer follow; topography; the presence of a shallow, unconfined, and locally recharged ground-water system; and a soluble salt source. Continuous cropping could reduce the amount of water percolating beneath local recharge areas, and thus minimize the water available for seep formation and growth. The lateral variation in chemical quality of water from wells suggests a shallow flow system. The field specific conductance of 29 ground-water samples collected in 1976 ranged from 2,160 to 14,000 micromhos per centimeter and averaged 6,660 micromhos per centimeter. Water from saline seeps in the study area contains principally sodium, magnesium, calcium, and sulfate. Nitrate is present in the ground water in concentrations of as much as 855 milligrams per liter. The high nitrate concentrations are interpreted to originate primarily from oxidation of organic material once native sod is broken by cultivation. (USGS).

  19. Geologic factors contributing to landslide generation in a pyroclastic area: August 1998 Nishigo Village, Japan

    NASA Astrophysics Data System (ADS)

    Chigira, Masahiro

    2002-07-01

    Vertical contrasts in permeability, particularly where permeable surface materials overlie impermeable materials that prohibit the downward infiltration of groundwater, concentrate the groundwater and become an important focus of landslides that are triggered by intense rainfall. Just such a hydrogeological structure is present within the pyroclastics in Nishigo Village in Fukushima Prefecture, Japan, where intense rainfall of 1200 mm in 6 days generated more than 1000 landslides in August 1998. Three types of landslides occurred. The first type occurred along the edges of small plateaus, where horizontal beds of permeable ash, scoria, and pumice overlie impermeable mudflow deposits consisting of tuffaceous fines and andesite blocks, and massive, weakly consolidated ignimbrites. The rainfall on the plateaus infiltrated downward first, then laterally within the permeable beds, finally gushing out at the plateau edges and triggering landslides. The second type of landslide occurred where weathered tuff of the same ignimbrite was present with a slip surface at the base of the heavily weathered zone. Within this heavily weathered zone, the tuff exfoliated into thin weak plates running parallel to the slope surface. The third type of landslide involved failure of colluvium or ash that filled hollows. This type occurred as a result of subsurface erosion caused by the groundwater infiltrating the superficial beds above the impermeable tuff.

  20. Terrain, vegetation, and landscape evolution of the R4D research site, Brooks Range Foothills, Alaska

    USGS Publications Warehouse

    Walker, D.A.; Binnian, Emily F.; Evans, B. M.; Lederer, N.D.; Nordstrand, E.A.; Webber, P.J.

    1989-01-01

    Maps of the vegetation and terrain of a 22 km2 area centered on the Department of Energy (DOE) R4D (Response, Resistance, Resilience to and Recovery from Disturbance in Arctic Ecosystems) study site in the Southern Foothills Physiographic Province of Alaska were made using integrated geobotanical mapping procedures and a geographic-information system. Typical land forms and surface f orms include hillslope water tracks, Sagavanirktok-age till deposits, nonsorted stone stripes, and colluvial-basin deposits. Thirty-two plant communities are described; the dominant vegetation (51% of the mapped area) is moist tussock-sedge, dwarf-shrub tundra dominated by Eriophorum vaginatum or Carex bigelowii. Much of the spatial variation in the mapped geobotanical characters reflects different-aged glaciated surfaces. Shannon-Wienerin dices indicate that the more mature landscapes, represented by retransported hillslope deposits and basin colluvium, are less heterogeneous than newer landscapes such as surficial till deposits and floodplains. A typical toposequence on a mid-Pleistocene-age surface is discussed with respect to evolution of the landscape. Thick Sphagnum moss layers occur on lower hillslopes, and the patterns of moss-layer development, heat flux, active layer thickness, and ground-ice are seen as keys to developing thermokarst-susceptibility maps.

  1. Geologic map of the greater Denver area, Front Range urban corridor, Colorado

    USGS Publications Warehouse

    Trimble, Donald E.; Machette, Michael N.

    1979-01-01

    This digital map shows the areal extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette from 1973 to 1977 and published in 1979 under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999) was digitized under the USGS Front Range Infrastructure Resources Project. In general, the mountainous areas in the western part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle comprises eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and a few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

  2. Geologic map of the White Hall quadrangle, Frederick County, Virginia, and Berkeley County, West Virginia

    USGS Publications Warehouse

    Doctor, Daniel H.; Orndorff, Randall C.; Parker, Ronald A.; Weary, David J.; Repetski, John E.

    2010-01-01

    The White Hall 7.5-minute quadrangle is located within the Valley and Ridge province of northern Virginia and the eastern panhandle of West Virginia. The quadrangle is one of several being mapped to investigate the geologic framework and groundwater resources of Frederick County, Va., as well as other areas in the northern Shenandoah Valley of Virginia and West Virginia. All exposed bedrock outcrops are clastic and carbonate strata of Paleozoic age ranging from Middle Cambrian to Late Devonian. Surficial materials include unconsolidated alluvium, colluvium, and terrace deposits of Quaternary age, and local paleo-terrace deposits possibly of Tertiary age. The quadrangle lies across the northeast plunge of the Great North Mountain anticlinorium and includes several other regional folds. The North Mountain fault zone cuts through the eastern part of the quadrangle; it is a series of thrust faults generally oriented northeast-southwest that separate the Silurian and Devonian clastic rocks from the Cambrian and Ordovician carbonate rocks and shales. Karst development in the quadrangle occurs in all of the carbonate rocks. Springs occur mainly near or on faults. Sinkholes occur within all of the carbonate rock units, especially where the rocks have undergone locally intensified deformation through folding, faulting, or some combination.

  3. Generalized surficial geology map of the Pueblo 1 degree by 2 degrees quadrangle, Colorado

    USGS Publications Warehouse

    Moore, D.W.; Straub, A.W.; Berry, M.E.; Baker, M.L.; Brandt, T.R.

    2002-01-01

    Fifty-three types of surficial geologic deposits and residual materials of Quaternary age are described in a pamphlet and located on a map of the greater Pueblo area, in part of the Front Range, in the Wet and Sangre de Cristo Mountains, and on the plains east of Colorado Springs and Pueblo. Deposits formed by landslides, wind, and glaciers, as well as colluvium, residuum, alluvium, and others are described in terms of predominant grain size, mineral or rock composition (e.g., gypsiferous, calcareous, granitic, andesitic), thickness, and other physical characteristics. Origins and ages of the deposits and geologic hazards related to them are noted. Many lines drawn between units on our map were placed by generalizing contacts on published maps. However, in 1997-1999 we mapped new boundaries as well. The map was projected to the UTM projection. This large map area extends from near Salida (on the west edge), eastward about 107 mi (172 km), and from Antero Reservoir and Woodland Park on the north edge to near Colorado City at the south edge (68 mi; 109 km).

  4. Great earthquake surface ruptures along backthrust of the Janauri anticline, NW Himalaya

    NASA Astrophysics Data System (ADS)

    Jayangondaperumal, R.; Kumahara, Y.; Thakur, V. C.; Kumar, Anil; Srivastava, Pradeep; Dubey, Shubhanshu; Joevivek, V.; Dubey, Ashok Kumar

    2017-01-01

    Results of a paleoseismic trenching investigation on a backthrust in the northern margin of Janauri hill, at Mehandpur (31°18‧11.37″N, 76°18‧31.47″E), Sub-Himalayan range of the Himachal Himalaya are presented. The active backthrust revealed the last event took place after 0.8 ± 0.03 ka ago (i.e. post CE 1200). The age of the last earthquake with a minimum fault slip ∼1 m along F1 fault and presence of single colluvium on the back thrust nearly matches with an earthquake event previously documented on the Bhatpur forethrust of the Himalayan frontal thrust system. Uplifted and truncated fluvial terraces due to displacement on the backthrust are preserved along several north flowing river valley sections in the northern limb of Janauri anticline. The long-term vertical uplift rate calculated through dividing difference between current elevation and elevation of current river grade is 1.08 ± 0.08 mm/yr. Field evidence shows fore and backthrusts are active and they form simultaneously, but displacements are episodic suggesting the backthrust develops either due to locking of forethrust or to accommodate a large amount of fault slip due to magnitude of earthquake event along the forethrust. Further, the backthrust may be used as an indirect method of inferring the age of the last event that took place along the forethrust.

  5. Reinterpretation of the Robein and Plano Silts, northeastern Illinois

    SciTech Connect

    Curry, B.B.; Kempton, J.P.

    1985-01-01

    Reinterpretation of till stratigraphy in northern Illinois and recently obtained radiocarbon dates suggest the Plano Silt is lithologically and stratigraphically indistinguishable from the Robein Silt. These recent data suggest colluvial silt and organic-rich sediment were deposited in most of the northern Illinois between >50,000 and 23,000 RCBP. This age range agrees with radiocarbon dates from the Mid-Wisconsinan Sidney Interstadial Soil of the Huron-Erie Lobe. Altonian (Early to Mid-Wisconsinan)-age till associated with the Lake Michigan Lobe has not yet been identified. Horberg and others recognize in northeastern Illinois a single basal Wisconsinan organic-rich zone; peat, silt and loess of the Farmdalian Substage were interpreted to overlie Sangamon Soil developed in Illinoian drift. They also interpreted a reddish-brown diamicton overlying the Plano Silt at its type section as the Capron Till Member of late Altonian age. The new data support the earlier interpretation of a single organic-rich deposit between Wisconsinan and Illinoian drifts. The Plano Silt should be abandoned as a rock-stratigraphic unit. The Robein Silt includes colluvium and organic-rich sediment not only of Farmdalian age, but also Altonian age in most of northern Illinois, similar to the rest of the upper Mississippi River Valley. The evidence of nearly continuous Robein deposition restricts possible Altonian-age glacial deposits to a narrow band on Capron Ridge in northern Illinois and southern Wisconsin.

  6. Identification of areas of recharge and discharge using Landsat-TM satellite imagery and aerial photography mapping techniques

    NASA Astrophysics Data System (ADS)

    Salama, R. B.; Tapley, I.; Ishii, T.; Hawkes, G.

    1994-10-01

    Aerial photographs (AP) and Landsat (TM) colour composites were used to map the geomorphology, geology and structures of the Salt River System of Western Australia. Geomorphic features identified are sand plains, dissected etchplain, colluvium, lateritic duricrust and rock outcrops. The hydrogeomorphic units include streams, lakes and playas, palaeochannels and palaeodeltas. The structural features are linear and curvilinear lineaments, ring structures and dolerite dykes. Suture lines control the course of the main river channel. Permeable areas around the circular granitic plutons were found to be the main areas of recharge in the uplands. Recharge was also found to occur in the highly permeable areas of the sandplains. Discharge was shown to be primarily along the main drainage lines, on the edge of the circular sandplains, in depressions and in lakes. The groundwater occurrence and hydrogeological classification of the recharge potential of the different units were used to classify the mapped areas into recharge and discharge zones. The results also show that TM colour composites provide a viable source of data comparable with AP for mapping and delineating areas of recharge and discharge on a regional scale.

  7. Sagging and collapse sinkholes over hypogenic hydrothermal karst in a carbonate terrain

    NASA Astrophysics Data System (ADS)

    Frumkin, Amos; Zaidner, Yossi; Na'aman, Israel; Tsatskin, Alexander; Porat, Naomi; Vulfson, Leonid

    2015-01-01

    We show that clusters of karst sinkholes can occur on carbonate hypogene karst terrains. Unlike common doline karst of dissolution origin, the studied sinkholes form mainly by sagging and collapse. Thermal survey, OSL dating and morphologic analysis during quarrying and excavations are applied to study the sinkholes at the Ayyalon karst, Israel. The thermal survey shows the spatial pattern of rising warm water plumes, whose temperature is > 2 °C warmer than the surrounding aquifer water. These plumes dissolve the limestone, creating large voids and maze caves. Mass wasting forms surface sinkholes mainly by sagging and collapse. Both types of deformation often occur within the same depression. Lack of hydrologic connection between the surface and underground voids constrain drainage and promote rapid accumulation of colluvium, dust and pedogenic clays. These have filled the sinkholes up to their rim before the late Holocene. OSL dating constrains the rate of sediment accumulation within the sinkholes. The average filling rate (thickness divided by elapsed time) is ~ 47 mm ka- 1 for the last 53 ± 4 ka in Sinkhole 1, while in Sinkhole 2 ("Nesher Ramla karst depression"), the rate is ~ 61 mm ka- 1 from ~ 200 to 78 ka, and ~ 173 mm ka- 1 since ~ 78 ka. Between ~ 170 and 78 ka, Sinkhole 2 was intensively used by Middle Paleolithic hominins. The studied sinkholes may be considered as a type locality for hypogene sinkhole terrain on carbonate rocks.

  8. Geologic Map of the Abiquiu Quadrangle, Rio Arriba County, New Mexico

    USGS Publications Warehouse

    Maldonado, Florian

    2008-01-01

    The Abiquiu 1:24,000-scale quadrangle is located along the Colorado Plateau-Rio Grande rift margin in north-central New Mexico. The map area lies within the Abiquiu embayment, an early (pre-Miocene) extensional basin of the Rio Grande rift. Rocks exposed include continental Paleozoic and Mesozoic rocks of the Colorado Plateau and Cenozoic basin-fill deposits and volcanic rocks of the Rio Grande rift. Paleozoic units include the Late Pennsylvanian to Early Permian Cutler Group, undivided. Mesozoic units are Upper Triassic Chinle Group, undivided, middle Jurassic Entrada Sandstone, and Todilto Limestone Member of the Wanakah Formation. Mesozoic rocks are folded in some areas and overlain disconformably by Cenozoic rocks. Cenozoic sedimentary rocks are composed of the Eocene El Rito Formation, Oligocene Ritito Conglomerate, Oligocene-Miocene Abiquiu Formation, and Miocene Chama-El Rito and Ojo Caliente Sandstone Members of the Tesuque Formation of the Santa Fe Group. Volcanic rocks include the Lobato Basalt, the El Alto Basalt, and dacite of the Tschicoma Formation. Quaternary deposits consist of inset ancestral axial and tributary Rio Chama deposits and Holocene floodplain alluvium, fan and pediment alluvium, and landslide colluvium.

  9. Geologic controls on movement of produced-water releases at US geological survey research Site A, Skiatook lake, Osage county, Oklahoma

    USGS Publications Warehouse

    Otton, J.K.; Zielinski, R.A.; Smith, B.D.; Abbott, M.M.

    2007-01-01

    Highly saline produced water was released from multiple sources during oil field operations from 1913 to 1973 at the USGS research Site A on Skiatook Lake in northeastern Oklahoma. Two pits, designed to hold produced water and oil, were major sources for release of these fluids at the site. Produced water spills from these and other features moved downslope following topography and downdip by percolating through permeable eolian sand and colluvium, underlying permeable sandstone, and, to a lesser extent, through shales and mudstones. Saline water penetrated progressively deeper units as it moved through the gently dipping bedrock to the north and NW. A large eroded salt scar north of the pits coincides with underlying fine-grained rocks that have retained substantial concentrations of salt, causing slow revegetation. Where not eroded, thick eolian sand or permeable sandstone bedrock is near the surface, and vegetation has been little affected or has reestablished itself after the introduced salt was flushed by precipitation. The extent of salt-contaminated bedrock extends well beyond existing surface salt scars. These results indicate that one of the legacies of surface salt spills can be a volume of subsurface salinization larger than the visible surface disturbance. ?? 2007.

  10. Fabric variability associated with periglacial mass-wasting at Eagle Summit, Alaska

    NASA Astrophysics Data System (ADS)

    Millar, Susan W. S.

    2005-12-01

    Fabric analysis is a frequently applied technique and, when used in concert with other tools, aids the interpretation of glacigenic and colluvial depositional environments. The research presented here focuses on its application to periglacial colluvium, using a stratified systematic unaligned sampling framework in order to assess the variation of fabrics generated. The range of possible variation in fabric is necessary information for its application to periglacial paleoenvironmental interpretation. Fabric strength and shape from 68 samples, of 50 stones each on a range of microgeomorphic settings across terrain influenced by periglacial mass-wasting in central Alaska, were analyzed in relation to local slope orientation, clast characteristics, organic mat thickness, stone density, distance downslope from the divide, soil texture and soil moisture. Principal components analysis (PCA) was used to reduce stone characteristics to three factors. Multiple regression analyses of the three factors and environmental variables, with the fabric strength parameters as dependent variables, indicate that stone characteristics, particularly size and platyness, are the most significant factors determining fabric strength. No distinct fabric strength or shape was associated with specific landforms. These results raise serious doubts as to the time-cost effectiveness of the application of fabric analysis as a paleoenvironmental tool to identify periglacial landforms from their deposits.

  11. Genesis and continuity of quaternary sand and gravel in glacigenic sediment at a proposed low-level radioactive waste disposal site in east-central Illinois

    USGS Publications Warehouse

    Troost, K.G.; Curry, B. Brandon

    1991-01-01

    The Illinois Department of Nuclear Safety has characterized the Martinsville Alternative Site (MAS) for a proposed low-level radioactive waste disposal facility. The MAS is located in east-central Illinois approximately 1.6 km (1 mi) north of the city of Martinsville. Geologic investigation of the 5.5-km2 (1380-acre) site revealed a sequence of chiefly Illinoian glacigenic sediments from 6 to 60 m (20-200 ft) thick overlying two major bedrock valleys carved in Pennsylvanian strata. Relatively permeable buried units include basal, preglacial alluvium; a complex of intraglacial and subglacial sediment; englacial deposits; and supraglacial fluvial deposits. Postglacial alluvium underlies stream valleys on and adjacent to the site. In most areas, the buried sand units are confined by low-permeability till, lacustrine sediment, colluvium, and loess. The distribution and thickness of the most extensive and continuous buried sand units have been modified considerably by subglacial erosion, and their distributions have been influenced by the buried bedrock valleys. The most continuous of the various sand units were deposited as preglacial and postglacial alluvium and are the uppermost and lowermost stratigraphic units at the alternative site. Sand units that were deposited in englacial or ice-marginal environments are less continuous. Aquifer pumping tests, potentiometric head data, and groundwater geochemistry analyses indicate minimal interaction of groundwater across localized interconnections of the permeable units. ?? 1991 Springer-Verlag New York Inc.

  12. Geologic map of the Alley Spring quadrangle, Shannon County, Missouri

    USGS Publications Warehouse

    Weary, David J.; Orndorff, Randall C.

    2012-01-01

    The Alley Spring 7.5-minute quadrangle is located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 1,990 feet (ft) of flat-lying to gently dipping Lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic volcanic rocks. A small exposure of the volcanic rocks exists near the eastern edge of the quadrangle. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Karst features, such as sinkholes, caves, and springs, have formed in the carbonate rocks. Many streams are spring fed. Alley Spring, the largest karst spring in the quadrangle, has an average discharge of 81 million gallons per day. The topography is a dissected karst plain with elevation ranging from 630 ft where the Jacks Fork River exits the quadrangle to more than 1,140 ft at numerous places in the northern half of the quadrangle. The most prominent physiographic feature is the valley of the Jacks Fork River. Most of the land in the quadrangle is privately owned and used primarily for grazing cattle and horses and growing timber. A large minority of the land within the quadrangle is publicly owned, either by the Missouri State Forests or by the Ozark National Scenic Riverways of the National Park Service. Geologic mapping for this investigation was conducted in 2003 and 2004.

  13. Regoliths of the middle-Atlantic Piedmont and evolution of a polymorphic landscape

    USGS Publications Warehouse

    Cleaves, E.T.

    2000-01-01

    The regolith overlying the alumino-silicate rocks of the middle-Atlantic Piedmont Province consists primarily of saprolite with a thin veneer of diamictons of colluvial origin. Thickness and distribution of the saprolite is related to landform and lithology. For example, on uplands isovolumetric weathering of the Loch Raven Schist produces saprolite averaging 55 ft (17 m) thick. On Port Deposit Gneiss, saprolite beneath uplands averages 42 ft (13 m) in thickness. The saprolite results from the reaction of alumino-silicate rocks with through-flowing groundwater. Chemical weathering of the rock results in clay and resistate minerals, residual rock layers, corestones, and pinnacles. Surface erosion of saprolite with quartzite and metagraywacke residual layers may produce a 'washboard' topography. Surface erosion of a metagabbro saprolite containing corestones and pinnacles results in a surface with lag deposits of corestones and emergent pinnacles. The diamicton material comes from the underlying saprolite, weathered rock and bedrock. Generally, diamictons are thinner on uplands and upper slopes, and thicker at the base of slopes and in hollows and gathering areas of first-order streams. The saprolite and colluvium reflect response of geomorphic processes (chemical weathering, fluvial incision, and periglacial processes) to rock lithology and landscape. The modifications to the landscape have been driven by neotectonic crustal warping and alternating periglacial-humid temperate climates. Altogether these varied interactions have resulted in a Holocene polymorphic landscape.

  14. Landslide susceptibility in the Tully Valley area, Finger Lakes region, New York

    USGS Publications Warehouse

    Jager, Stefan; Wieczorek, Gerald E.

    1994-01-01

    As a consequence of a large landslide in the Tully Valley, Onondaga County, New York, an investigation was undertaken to determine the factors responsible for the landslide in order to develop a model for regional landslide susceptibility. The April 27, 1993 Tully Valley landslide occurred within glacial lake clays overlain by till and colluvium on gentle slopes of 9-12 degrees. The landslide was triggered by extreme climatic events of prolonged heavy rainfall combined with rapid melting of a winter snowpack. A photoinventory and field checking of landslides within a 415 km2 study area, including the Tully Valley, revealed small recently-active landslides and other large dormant prehistoric landslides, probably Pleistocene in age. Similar to the larger Tully Valley landslide, the smaller recently-active landslides occurred in red, glacial lake clays very likely triggered by seasonal rainfall. The large dormant landslides have been stable for long periods as evidenced by slope denudational processes that have modified the landslides. These old and ancient landslides correspond with proglacial lake levels during the Pleistocene, suggesting that either inundation or rapid drainage was responsible for triggering these landslides. A logistic regression analysis was performed within a Geographic Information System (GIS) environment to develop a model of landslide susceptibility for the Tully Valley study area. Presence of glacial clays, slope angle, and glacial lake levels were used as explanatory variables for landslide incidence. The spatial probability of landsliding, categorized as low, moderate and high, is portrayed within 90-m square cells on the susceptibility map.

  15. Lipid biomarker and compound-specific isotope analysis of cave sediments: a new approach to investigating past vegetation change

    NASA Astrophysics Data System (ADS)

    Blyth, A.; Griffiths, T.; Robson, S.

    2009-12-01

    Caves are vital archives for records of terrestrial palaeoenvironmental change, as they form sheltered sediment traps capable of preserving long environmental sequences. Due to their unique role in the landscape, they are also intimately connected to the archaeology and palaeoecology of the parent region. Chemical proxy records preserved in speleothems (chemically precipitated cave deposits) have long been used as a tool in palaeoclimatic research, but clastic sediments deposited by air, water, and breakdown of the surrounding rock also have much to contribute. However, although well researched in a sedimentary context, the geochemical records contained in these deposits, especially organic parameters, have been less well-studied. Here we present the first in-depth study of the organic geochemistry of cave sediment sequences, using samples from two south-east Asian caves, and focusing on plant-derived lipid biomarkers and their associated compound-specific carbon isotope records. The work aimed to establish: whether routine extraction and analysis of compounds was feasible in this context at acceptable sample sizes; whether there was a significant vegetation-derived contribution to the record; whether the depositional mode of the sediment (colluvium, midden, channel fill etc) affects the organic composition; and whether the records show coherent and interpretable variation through time. Two sites were studied: Niah Cave in Borneo, where the sediments recovered are a mixture of colluvium and channel fill and date back to >40 ka; and Hang Boi in Vietnam, where the principal deposit is a Holocene occupation midden dominated by land-snail shells. To recover the lipid fraction 7 g aliquots of freeze-dried sediment were extracted by sonication in 95:5 dichloromethane:methanol. Excess solvent was then removed via rotary evaporation and the extracts derivatised with BF3-Methanol and BSTFA prior to analysis by GC-MS. The lipid extracts contain a range of compounds including

  16. Ground ice conditions in Salluit, Northern Quebec

    NASA Astrophysics Data System (ADS)

    Allard, M.; Fortier, R.; Calmels, F.; Gagnon, O.; L'Hérault, E.

    2011-12-01

    Salluit in Northern Québec (ca. 1300 inhabitants) faces difficult ground ice conditions for its development. The village is located in a U-shaped valley, along a fjord that was deglaciated around 8000 cal BP. The post-glacial marine limit is at the current elevation of 150 m ASL. Among the mapped surficial geology units, three contain particularly ice-rich permafrost: marine clays, till and silty colluviums. A diamond drill was used to extract 10 permafrost cores down to 23 m deep. In addition, 18 shallow cores (to 5 m deep) were extracted with a portable drill. All the frozen cores were shipped to Québec city where ground ice contents were measured and cryostructures were imaged by CT-Scanning. Water contents, grain-size and pore water salinity were measured. Refraction seismic profiles were run to measure the depth to bedrock. GPR and electrical resistivity surveys helped to map ice-rich areas. Three cone penetration tests (CPT) were run in the frozen clays to depths ranging from 8 to 21 m. Maximum clay thickness is ca. 50 m deep near the shoreline. The cone penetration tests and all the cores in clays revealed large amounts of both segregated and aggradational ice (volumetric contents up to 93% over thicknesses of one meter) to depths varying between 2.5 and 4 m, below which the ice content decreases and the salinity increases (values measured up to 42 gr/L between 4.5 and 6 m deep). Chunks of organic matter buried below the actual active layer base indicate past cryoturbations under a somewhat warmer climate, most probably associated with intense frost boil action, as widely observed today. The stony till has developed large quantities of segregation ice which can be seen in larger concentrations and as thicker lenses under boulders and in matrix rich (≥ 50% sand and silt) parts of the glacial sediment. As digging for a sewage pond was undertaken in winter 2008 by blasting, the clast-influenced cryostructure of the till could be observed in cuts and in

  17. Fluvial system autogenesis in the Sneeuberg Mountains, South Africa: implications for reconstructing trajectories of landscape response.

    NASA Astrophysics Data System (ADS)

    Oldknow, Chris; Hooke, Janet; Lang, Andreas

    2015-04-01

    South-draining small upland catchments (< 5 km2) of the Sneeuberg Mountains, South Africa contain dendritic gully networks incised into deep deposits (up to 6 m) of colluvium and alluvium. Alluvial fans and flood-outs are common on upper slopes, while lower valley segments are occupied by wedges of alluvium and colluvium of varying depth and, in some instances, truncated laterally impinging fans where local hillslope-channel coupling is high. Several key sediment outcrops show a complex of cut and fill sequences, with subtle variations in soil overprinting pointing to a succession of phases of geomorphic instability and stability. Similar sequences also occur in main valleys and upstream of a nearby canyon. Gully cross sectional morphology changes significantly according to local valley morphology with loss of confinement upstream of headcuts through Permo-Triassic Beaufort Group sandstone/mudstones and intrusive dolerite dykes of the Drakensberg Group. These outcrops have acted as barriers to local sediment connectivity in the past, but many are now partially or completely incised. Local geomorphic 'niches' relating to these changes in valley and channel morphology mean that autogenic processes predominate and thus significant leads and lags in the response of the landscape to climatic perturbations are highly probable. The palaeoenvironmental significance of these non-continuous clastic sedimentary archives can be evaluated, at least in part, via detailed analysis of modern analogues to interpret the depositional and pedogenic environments recorded in terrace fills, in tandem with the development of a new conceptual model detailing the likely trajectories of landscape response. Here we present results from two fieldwork campaigns in which detailed DGPS surveys of river long profiles, terrace height and delimitation of principal morphostratigraphic units in relation to barriers of different configuration and longevity were obtained. The resulting

  18. Preliminary Assessment of Landslides Along the Florida River Downstream from Lemon Reservoir, La Plata County, Colorado

    USGS Publications Warehouse

    Schulz, William H.; Coe, Jeffrey A.; Ellis, William L.; Kibler, John D.

    2006-01-01

    Nearly two-dozen shallow landslides were active during spring 2005 on a hillside located along the east side of the Florida River about one kilometer downstream from Lemon Reservoir in La Plata County, southwestern Colorado. Landslides on the hillside directly threaten human safety, residential structures, a county roadway, utilities, and the Florida River, and indirectly threaten downstream areas and Lemon Dam. Most of the area where the landslides occurred was burned during the 2002 Missionary Ridge wildfire. We performed geologic mapping, subsurface exploration and sampling, radiocarbon dating, and shallow ground-water and ground-displacement monitoring to assess landslide activity. Active landslides during spring 2005 were as large as 35,000 m3 and confined to colluvium. Debris flows were mobilized from most of the landslides, were as large as 1,500 m3, and traveled as far as 250 m. Landslide activity was triggered by elevated ground-water pressures within the colluvium caused by infiltration of snowmelt. Landslide activity ceased as ground-water pressures dropped during the summer. Shallow landslides on the hillside appear to be much more likely following the Missionary Ridge fire because of the loss of tree root strength and evapotranspiration. We used monitoring data and observations to develop preliminary, approximate rainfall/snowmelt thresholds above which shallow landslide activity can be expected. Landslides triggered during spring 2005 occurred within a 1.97 x 107 m3 older landslide that extends, on average, about 40 m into bedrock. The south end of this older landslide appears to have experienced deep secondary landsliding. Radiocarbon dating of sediments at the head of the older landslide suggests that the landslide was active about 1,424-1,696 years ago. A relatively widespread wildfire may have preceded the older landslide, and the landslide may have occurred during a wetter time. The wetter climate and effects of the wildfire would likely have

  19. Depth of Small Scale Landslide in Slate Area : Case of 2009 Typhoon Morakot in Ai-Liao River, South Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, T. C.; Yen, H. Y.; Zhou, F. L.

    2015-12-01

    This study focuses on the depth and magnitude of the small scale landslide in slate area in Ai-Liao-Shi catchment, South Taiwan. Landslide inventory of 2009 Typhoon Morakot, 5×5 m DEM, and aero photo have been interpreted by GIS software to assess the slope type and the scale of landslide events. The research database includes 276 landslides which orthographic projection areas are smaller than 1 ha. The slopes were also classified into dip, orthoclinical-dip, escarpment, and orthoclinical- escarpment 4 types of slope based on the slope aspect to the bedding orientation. The sliding plane, or so call the failure plane, was identified by aero photo, field reconnaissance and verification, and DEM before and after the typhoon event. Colluvium material deposited on the slip plane was removed based on the scarp and foot position, mass movement pattern, weak plane orientation, and the micro topography of a landslide to achieve the reasonable sliding plane. The maximum depth of sliding surface is explored through the slope type and sliding plane in total of 276 landslide cases. Results demonstrate that the average maximum depth, Dam, of dip slope is 4.6 m, Dam of orthoclinical-dip, escarpment, and orthoclinical-escarpment slopes are 5.8, 6.0, and 6.3 m respectively. In general, Dam is creasing with the average slope of landslide, the relationship of both factor is achieved in the study. Meanwhile, the orthographic projection area of landslide is increasing with the slope angle till the angle up to 40 degree then decreasing. The depth also varies with landslide magnitude. Finally, the relation of the depth normal to slope surface and the depth in gravity direction of landslides in four types slope are proposed, the R square values are 0.862 to 0.891 showing a good correlation between two types of depth.

  20. Assessing landslide potential on coastal bluffs near Mukilteo, Washington—Geologic site characterization for hydrologic monitoring

    USGS Publications Warehouse

    Mirus, Benjamin B.; Smith, Joel B.; Benjamin Stark,; York Lewis,; Abigail Michel,; Baum, Rex L.

    2016-07-01

    During the summer 2015, the U.S. Geological Survey collected geologic and geotechnical data for two sites on coastal bluffs along the eastern shore of Puget Sound, Washington. The U.S. Geological Survey also installed hydrologic instrumentation at the sites and collected specimens for laboratory testing. The two sites are located on City of Mukilteo open-space land and are about 0.6 kilometers apart. The bluffs at each site are approximately 42 meters high, and rise steeply from the shoreline with 32–35° slopes. The more northerly of the two sites occupies an active landslide and is mostly unvegetated. The other site is forested, and although stable during the preparation of this report, shows evidence of historical and potential landslide activity. The slopes of the bluffs at both sites are mantled by a thin, nonuniform colluvium underlain by clay-rich glacial deposits and tills of the Whidbey Formation or Double Bluff Drift. Till consisting of sand, gravel, and cobbles caps the bluffs and rests on finer grained glacial deposits of sand, silt, and clay. These types of different glacial deposits are dense, vertically fractured, and generally have low permeability, but field observations indicate that locally the deposits are sufficiently permeable to allow lateral flow of water along fractures and subhorizontal boundaries between deposits of different texture. Laboratory tests indicate that many of the deposits are highly plastic, with low hydraulic conductivity, and moderate shear strength. Steep slopes combined with the strength and hydraulic characteristics of the deposits leave the bluffs prone to slope instability, particularly during the wet season when infiltrating rainfall changes moisture content, pore-water pressure, and effective stress within the hillslope. The instrumentation was designed to primarily observe rainfall variability and hydrologic changes in the subsurface that can affect stability of the bluffs, and also to compare the hydrologic

  1. A spatial database of bedding attitudes to accompany Geologic map of the greater Denver area, Front Range Urban Corridor, Colorado

    USGS Publications Warehouse

    Trimble, Donald E.; Machette, Michael N.; Brandt, Theodore R.; Moore, David W.; Murray, Kyle E.

    2003-01-01

    This digital map shows bedding attitude symbols display over the geographic extent of surficial deposits and rock stratigraphic units (formations) as compiled by Trimble and Machette 1973-1977 and published in 1979 (U.S. Geological Survey Map I-856-H) under the Front Range Urban Corridor Geology Program. Trimble and Machette compiled their geologic map from published geologic maps and unpublished geologic mapping having varied map unit schemes. A convenient feature of the compiled map is its uniform classification of geologic units that mostly matches those of companion maps to the north (USGS I-855-G) and to the south (USGS I-857-F). Published as a color paper map, the Trimble and Machette map was intended for land-use planning in the Front Range Urban Corridor. This map recently (1997-1999), was digitized under the USGS Front Range Infrastructure Resources Project (see cross-reference). In general, the mountainous areas in the west part of the map exhibit various igneous and metamorphic bedrock units of Precambrian age, major faults, and fault brecciation zones at the east margin (5-20 km wide) of the Front Range. The eastern and central parts of the map (Colorado Piedmont) depict a mantle of unconsolidated deposits of Quaternary age and interspersed outcroppings of Cretaceous or Tertiary-Cretaceous sedimentary bedrock. The Quaternary mantle is comprised of eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone, shale, and limestone bedrock formations form hogbacks and intervening valleys.

  2. A spatial database of bedding attitudes to accompany Geologic Map of Boulder-Fort Collins-Greeley Area, Colorado

    USGS Publications Warehouse

    Colton, Roger B.; Brandt, Theodore R.; Moore, David W.; Murray, Kyle E.

    2003-01-01

    This digital map shows bedding attitude data displayed over the geographic extent of rock stratigraphic units (formations) as compiled by Colton in 1976 (U.S.Geological Survey Map I-855-G) under the Front Range Urban Corridor Geology Program. Colton used his own mapping and published geologic maps having varied map unit schemes to compile one map with a uniform classification of geologic units. The resulting published color paper map was intended for planning for use of land in the Front Range Urban Corridor. In 1997-1999, under the USGS Front Range Infrastructure Resources Project, Colton's map was digitized to provide data at 1:100,000 scale to address urban growth issues(see cross-reference). In general, the west part of the map shows a variety of Precambrian igneous and metamorphic rocks, major faults and brecciated zones along an eastern strip (5-20 km wide) of the Front Range. The eastern and central part of the map (Colorado Piedmont) depicts a mantle of Quaternary unconsolidated deposits and interspersed Cretaceous or Tertiary-Cretaceous sedimentary rock outcrops. The Quaternary mantle is comprised of eolian deposits (quartz sand and silt), alluvium (gravel, sand, and silt of variable composition), colluvium, and few landslides. At the mountain front, north-trending, dipping Paleozoic and Mesozoic sandstone and shale formations (and sparse limestone) form hogbacks, intervening valleys, and in range-front folds, anticlines, and fault blocks. Localized dikes and sills of Tertiary rhyodacite and basalt intrude rocks near the range front, mostly in the Boulder area.

  3. An establishment on the hazard mitigation system of large scale landslides for Zengwen reservoir watershed management in Taiwan

    NASA Astrophysics Data System (ADS)

    Tsai, Kuang-Jung; Lee, Ming-Hsi; Chen, Yie-Ruey; Huang, Meng-Hsuan; Yu, Chia-Ching

    2016-04-01

    Extremely heavy rainfall with accumulated rainfall amount more than 2900mm within continuous 3 day event occurred at southern Taiwan has been recognized as a serious natural hazard caused by Morakot typhoon in august, 2009. Very destructive large scale landslides and debris flows were induced by this heavy rainfall event. According to the satellite image processing and monitoring project was conducted by Soil & Water Conservation Bureau after Morakot typhoon. More than 10904 sites of landslide with total sliding area of 18113 ha were significantly found by this project. Also, the field investigation on all landslide areas were executed by this research on the basis of disaster type, scale and location related to the topographic condition, colluvium soil characteristics, bedrock formation and geological structure after Morakot hazard. The mechanism, characteristics and behavior of this large scale landslide combined with debris flow disasters are analyzed and Investigated to rule out the interaction of factors concerned above and identify the disaster extent of rainfall induced landslide during the period of this study. In order to reduce the disaster risk of large scale landslide and debris flow, the adaption strategy of hazard mitigation system should be set up as soon as possible and taken into consideration of slope land conservation, landslide control countermeasure planning, disaster database establishment, environment impact analysis and disaster risk assessment respectively. As a result, this 3-year research has been focused on the field investigation by using GPS/GIS/RS integration, mechanism and behavior study regarding to the rainfall induced landslide occurrence, disaster database and hazard mitigation system establishment. In fact, this project has become an important issue which was seriously concerned by the government and people live in Taiwan. Hopefully, all results come from this research can be used as a guidance for the disaster prevention and

  4. Analyzing Layers of Soil Colluvia for Reconstruction of Soil Erosion and Holocene Landscape Genesis With Ground Penetrating Radar

    NASA Astrophysics Data System (ADS)

    Werban, U.; Dreibrodt, S.; Rabbel, W.; Bork, H.; Al Hagrey, S.

    2005-05-01

    Since the GPR method is suitable to differentiate soil layers with different water content based on the dielectric contrast, we apply it to solve landscape genetic and geomorphological questions. Historical and recent soil erosion events, caused by surface runoff, are documented in sequences of soil colluvia. These depositional areas called geoarchives often contain dateable objects, such as artifacts (potsherd or bricks) and charcoal. Geoarchives, e.g. colluvial fans and trench in-fills, are used as a source of information about past environmental conditions and for determination of land use impacts caused by human activities. Large exposures are common to characterize soil colluvia stratigraphy, and additional drillings are needed to correlate the layers and horizons found in different exposures. Often, soil colluvia sequences are characterized by a well defined layering and consecutive layers show different grain size. These layers have different saturation-suction relationships (pF-curve) and varied moisture contents. Our research focuses on radar mapping and characterizing these layers of soil colluvia in consideration of different moisture distributions. We present measurements with 200 MHz and 400 MHz antennas determined in a catchment area in northern Germany. Common offset measurements were used to map the distribution of accumulated sediments. GPR travel times were depth migrated to correlate them with the exposure survey. The velocity distribution with depth was determined with multi offset measurements and analysis of reflections of a metal rod in a known depth. TDR measurements in different layers within the exposure are used to verify the moisture distribution with depth. We mapped the boundary between soil colluvium and the underlying parent material (weichselian till, glaciofluviatil sand) and differentiated layers within the soil colluvia. Consequently a more detailed balancing of erosion and accumulation rates to quantify historical soil losses is

  5. Geologic Map of the San Luis Quadrangle, Costilla County, Colorado

    USGS Publications Warehouse

    Machette, Michael N.; Thompson, Ren A.; Drenth, Benjamin J.

    2008-01-01

    The map area includes San Luis and the primarily rural surrounding area. San Luis, the county seat of Costilla County, is the oldest surviving settlement in Colorado (1851). West of the town are San Pedro and San Luis mesas (basalt-covered tablelands), which are horsts with the San Luis fault zone to the east and the southern Sangre de Cristo fault zone to the west. The map also includes the Sanchez graben (part of the larger Culebra graben), a deep structural basin that lies between the San Luis fault zone (on the west) and the central Sangre de Cristo fault zone (on the east). The oldest rocks exposed in the map area are the Pliocene to upper Oligocene basin-fill sediments of the Santa Fe Group, and Pliocene Servilleta Basalt, a regional series of 3.7?4.8 Ma old flood basalts. Landslide deposits and colluvium that rest on sediments of the Santa Fe Group cover the steep margins of the mesas. Rare exposures of the sediment are comprised of siltstones, sandstones, and minor fluvial conglomerates. Most of the low ground surrounding the mesas and in the graben is covered by surficial deposits of Quaternary age. The alluvial deposits are subdivided into three Pleistocene-age units and three Holocene-age units. The oldest Pleistocene gravel (unit Qao) forms extensive coalesced alluvial fan and piedmont surfaces, the largest of which is known as the Costilla Plain. This surface extends west from San Pedro Mesa to the Rio Grande. The primary geologic hazards in the map area are from earthquakes, landslides, and localized flooding. There are three major fault zones in the area (as discussed above), and they all show evidence for late Pleistocene to possible Holocene movement. The landslides may have seismogenic origins; that is, they may be stimulated by strong ground shaking during large earthquakes. Machette and Thompson based this geologic map entirely on new mapping, whereas Drenth supplied geophysical data and interpretations.

  6. Integrating Near-Real Time Hydrologic-Response Monitoring and Modeling for Improved Assessments of Slope Stability Along the Coastal Bluffs of the Puget Sound Rail Corridor, Washington State

    NASA Astrophysics Data System (ADS)

    Mirus, B. B.; Baum, R. L.; Stark, B.; Smith, J. B.; Michel, A.

    2015-12-01

    Previous USGS research on landslide potential in hillside areas and coastal bluffs around Puget Sound, WA, has identified rainfall thresholds and antecedent moisture conditions that correlate with heightened probability of shallow landslides. However, physically based assessments of temporal and spatial variability in landslide potential require improved quantitative characterization of the hydrologic controls on landslide initiation in heterogeneous geologic materials. Here we present preliminary steps towards integrating monitoring of hydrologic response with physically based numerical modeling to inform the development of a landslide warning system for a railway corridor along the eastern shore of Puget Sound. We instrumented two sites along the steep coastal bluffs - one active landslide and one currently stable slope with the potential for failure - to monitor rainfall, soil-moisture, and pore-pressure dynamics in near-real time. We applied a distributed model of variably saturated subsurface flow for each site, with heterogeneous hydraulic-property distributions based on our detailed site characterization of the surficial colluvium and the underlying glacial-lacustrine deposits that form the bluffs. We calibrated the model with observed volumetric water content and matric potential time series, then used simulated pore pressures from the calibrated model to calculate the suction stress and the corresponding distribution of the factor of safety against landsliding with the infinite slope approximation. Although the utility of the model is limited by uncertainty in the deeper groundwater flow system, the continuous simulation of near-surface hydrologic response can help to quantify the temporal variations in the potential for shallow slope failures at the two sites. Thus the integration of near-real time monitoring and physically based modeling contributes a useful tool towards mitigating hazards along the Puget Sound railway corridor.

  7. Geologic Map of The Volcanoes Quadrangle, Bernalillo and Sandoval Counties, New Mexico

    USGS Publications Warehouse

    Thompson, Ren A.; Shroba, Ralph R.; Menges, Christopher M.; Schmidt, Dwight L.; Personius, Stephen F.; Brandt, Theodore R.

    2009-01-01

    This geologic map, in support of the U.S. Geological Survey Middle Rio Grande Basin Geologic Mapping Project, shows the spatial distribution of surficial deposits, lava flows, and related sediments of the Albuquerque volcanoes, upper Santa Fe Group sediments, faults, and fault-related structural features. These deposits are on, along, and beneath the Llano de Albuquerque (West Mesa) west of Albuquerque, New Mexico. Some of these deposits are in the western part of Petroglyph National Monument. Artificial fill deposits are mapped chiefly beneath and near the City of Albuquerque Soil Amendment Facility and the Double Eagle II Airport. Alluvial deposits were mapped in and along stream channels, beneath terrace surfaces, and on the Llano de Albuquerque and its adjacent hill slopes. Deposits composed of alluvium and colluvium are also mapped on hill slopes. Wedge-shaped deposits composed chiefly of sandy sheetwash deposits, eolian sand, and intercalated calcic soils have formed on the downthrown-sides of faults. Deposits of active and inactive eolian sand and sandy sheetwash deposits mantle the Llano de Albuquerque. Lava flows and related sediments of the Albuquerque volcanoes were mapped near the southeast corner of the map area. They include eleven young lava flow units and, where discernable, associated vent and near-vent pyroclastic deposits associated with cinder cones. Upper Santa Fe Group sediments are chiefly fluvial in origin, and are well exposed near the western boundary of the map area. From youngest to oldest they include a gravel unit, pebbly sand unit, tan sand and mud unit, tan sand unit, tan sand and clay unit, and silty sand unit. Undivided upper Santa Fe Group sediments are mapped in the eastern part of the map area. Faults were identified on the basis of surface expression determined from field mapping and interpretation of aeromagnetic data where concealed beneath surficial deposits. Fault-related structural features are exposed and were mapped near

  8. Eolian Signal of the Onset of the Late Paleozoic Ice Age in North America Re-Deposited and Preserved As Paleo-Cave Sediments, Southwestern Colorado, U.S.a.

    NASA Astrophysics Data System (ADS)

    Evans, J. E.; Soreghan, M. J.

    2014-12-01

    The Molas Formation is a loessite consisting of reddish silt of Early Pennsylvanian (Bashkirian) age. U-Pb age spectra of accessory zircons indicate long-distance (>2000 km) transport from the Grenville province in northeastern North America plus sources from the peri-Gondwanan terranes in southeastern North America and local sources in the Ancestral Rocky Mountains uplift. These eolian sediments formed a blanket deposit <30 m thick above a paleokarst landscape in southwestern Colorado, infilling solution valleys and burying karst towers developed on the underlying Mississippian (Tournaisian-Visean) Leadville Limestone. The loessite is an eolian signal for the probable onset of glaciation at multiple locations in tectonically uplifted mountainous areas in North America. However, the loessite is easily eroded and has low preservation potential. Prior to lithification, significant amounts of the loess were remobilized and transported into the underlying karst system. As paleo-cave deposits, encased in limestone and dolostone, the silt-rich deposits have a higher preservation potential, and the eolian signal of the onset of the Late Paleozoic Ice Age in North America is still recognizable. However, the following signal modification processes need to be understood: (1) source area weathering and pedogenesis; (2) land-atmosphere transfer processes; (3) deposition effects of paleotopography, vegetation and moisture conditions, and infiltration into open fractures and/or the matrix of colluvium; (4) remobilization by surface runoff into open fractures and/or groundwater piping/sapping processes in loess soils; (5) transport into vadose and phreatic karst passageways by episodic ("streamflood") hydrologic events, forming event deposits (debrites, inundites, and jointites); (6) breakout dome collapse (forming interbedded cave sediments, karst breccias, and speleothems); (7) lithification and diagenesis; (8) post-lithification modification including pervasive hydrothermal

  9. Characterizing the Iron Wash fault: A fault line scarp in Utah

    NASA Astrophysics Data System (ADS)

    Kozaci, O.; Ostenaa, D.; Goodman, J.; Zellman, M.; Hoeft, J.; Sowers, J. M.; Retson, T.

    2015-12-01

    The Iron Wash fault (IWF) is an approximately 30 mile-long, NW-SE trending structure, oriented perpendicular to the San Rafael Monocline near Green River in Utah. IWF exhibits well-expressed geomorphic features such as a linear escarpment with consistently north side down displacement. The fault coincides with an abrupt change in San Rafael Monocline dip angle along its eastern margin. The IWF is exposed in incised drainages where Jurassic Navajo sandstone (oldest) and Lower Carmel Formation (old), are juxtaposed against Jurassic Entrada sandstone (younger) and Quaternary alluvium (youngest). To assess the recency of activity of the IWF we performed detailed geomorphic mapping and a paleoseismic trenching investigation. A benched trench was excavated across a Quaternary fluvial terrace remnant across the mapped trace of the IWF. The uppermost gravel units and overlying colluvium are exposed in the trench across the projection of the fault. In addition, we mapped the basal contact of the Quaternary gravel deposit in relation to the adjacent fault exposures in detail to show the geometry of the basal contact near and across the fault. We find no evidence of vertical displacement of these Quaternary gravels. A preliminary U-series date of calcite cementing unfaulted fluvial gravels and OSL dating of a sand lens within the unfaulted fluvial gravels yielded approximately 304,000 years and 78,000 years, respectively. These preliminary results of independent dating methods constrains the timing of last activity of the IWF to greater than 78,000 years before present suggesting that IWF not an active structure. Its distinct geomorphic expression is most likely the result of differential erosion, forming a fault-line scarp.

  10. Soil survey of Solid Waste Storage Area 6

    SciTech Connect

    Lietzke, D.A.; Lee, S.Y.

    1986-06-01

    An intensive soil survey was made of Solid Waste Storage Area (SWSA) 6 (Oak Ridge National Laboratory) at a scale of 1:1200. The amount of chemical weathering, the thickness of upland soils, and the depth to unoxidized rock are dependent on slope gradient, water-flow pathways, degree of rock fracturing, and the extent of soil and rock erosion by late Pleistocene and Holocene geomorphic processes. Foot-slope landforms have generally concave slope shapes where sediment accumulates. Colluvium stratigraphy exhibits at least one lithologic discontinuity, but there may be two discontinuities preserved in some thicker colluvia. One or more paleosols, either complete or partially truncated, are preserved in these concave landforms. Alluvial soils were not examined in detail but were separated from colluvial soils because of their wetness. A small area of ancient alluvium was located on a stable upland summit that formed the highest elevation in SWSA-6. On the nearly level summit, a thin loess cap was preserved on the older alluvial soil. Upland and colluvial soils are all highly leached and strongly acid even though they are formed from a calcareous parent rock. The highly fractured rock, being relatively permeable, has been leached free of carbonates in the upper levels so that there is a wide pH gradient from the surface downward. Most of the soils were classified as Ultisols, with minimal areas of Alfisols, Inceptisols, and Entisols. Based on the soil survey, representative landforms and soils will be selected to study physical, chemical, and mineralogical properties of the soil and weathered rock. Those properties will be used to predict both the amount and duration of leachate filtration and purification in downward migration to the water table or lateral migration through colluvial and alluvial soils to ground-water seeps.

  11. Geomorphological, pedological and dendrochronological signatures of a relict landslide terrain, Mt Garbatka (Kamienne Mts), SW Poland

    NASA Astrophysics Data System (ADS)

    Migoń, Piotr; Kacprzak, Andrzej; Malik, Ireneusz; Kasprzak, Marek; Owczarek, Piotr; Wistuba, Małgorzata; Pánek, Tomaš

    2014-08-01

    In the Kamienne Mountains the largest concentration of apparently relict landslides in the Sudetes range occurs. On the northern slopes of Mt Garbatka mass movements re-shaped two adjacent slope hollows and a wide depositional area is located down the valley. The main landslide body is nearly 1 km long and 200-300 m wide. Its flattened surface morphology and the occurrence of large dispersed allochtonous boulders in the distal part suggests a flow-like movement, initiated by shallow translational slides in the upper slopes. The thickness of colluvium, determined by an ERT survey, may reach 10 m. Geomorphic signatures of mass movement are subdued, suggesting that considerable time has elapsed since the origin of the landslide and that large-scale mass movements are likely pre-Holocene in age. This is consistent with the results of an extensive soil survey within the landslide body and on the surrounding slopes. Similarity of soil properties and well-developed horizonation of profiles both within the landslide and outside it shows that no major disturbance has taken place during the soil formation period. Dendrogeomorphological research, in turn, yielded evidence of numerous growth disturbances recorded in tree rings of Norway spruce growing on the landslide body. These signals are interpreted that the slope surface is not entirely stable under current environmental conditions. Flow or creep of landslide material is not very likely, given the characteristics of cover materials, and it is hypothesized that dendrochronological signals develop in response to ground deformation through piping and throughflow. Landslide hazard in the valley below Mt Garbatka appears low at present but to claim complete stability would be premature.

  12. Multi-stage evolution process of large scale landslides at the Patanpunas stream, Taiwan

    NASA Astrophysics Data System (ADS)

    Lin, Ming-Lang; Lee, Kuo-Chen; Lo, Chia-Ming; Weng, Meng-Chia; Lee, Shun-Min

    2016-04-01

    This study used multi-temporal terrain and remote sensing images to investigate the geomorphological evolution of the Putanpunas stream caused by large-scale landslides over the last decade. We conducted an analysis of the landslides evolution process within the study area, which included a multi-temporal terrain analysis, remote sensing interpretation, surface displacement analysis, and mechanism investigation. By integrating the results from these analyses, we provided explanations for the topographic and geomorphologic action processes of the deep-seated landslides as well as the development of the potential collapsing mechanisms within the study area. Then, discrete element method was used to simulate the process of landslide movement and deposition. The results show that the evolution process of large-scale landslides in the Putanpunas stream can be divided into four stages, namely downcutting of the stream gully and decompression of the river gully in the early stage, creep and deformation of the rock slope, sliding surface development of the deformed bands in the rock strata, and movement of the sliding mass. The results of terrain analysis and interpretation show topographical changes in the alluvial fan downstream and the deposits in the midstream and downstream segments of the Putanpunas Stream between 2005 and 2009. In 2009, torrential rainfall induced large-scale landslides that greatly altered the terrain of the Putanpunas Stream and the alluvial fan. There still exists 7.2 × 107 m3 of unstable colluvium accumulated at the slope surface and stream gully within the upstream and midstream areas. In 2012, further large-scale landslides turned the colluvial layer into debris flows that cut across the Ryukyu Terraces downstream to the downstream segment of the Laonong Stream to the southwest. This greatly changed later debris flows and alluvial fan deposits. Key Words: large-scale landslides, multi-temporal terrain, remote sensing, discrete element method

  13. Landslide Geohazard Monitoring, Early Warning and Stabilization Control Methods

    NASA Astrophysics Data System (ADS)

    Bednarczyk, Zbigniew

    2014-03-01

    This paper is a presentation of landslide monitoring, early warning and remediation methods recommended for the Polish Carpathians. Instrumentation included standard and automatic on-line measurements with the real-time transfer of data to an Internet web server. The research was funded through EU Innovative Economy Programme and also by the SOPO Landslide Counteraction Project. The landslides investigated were characterized by relatively low rates of the displacements. These ranged from a few millimetres to several centimetres per year. Colluviums of clayey flysch deposits were of a soil-rock type with a very high plasticity and moisture content. The instrumentation consisted of 23 standard inclinometers set to depths of 5-21 m. The starting point of monitoring measurements was in January 2006. These were performed every 1-2 months over the period of 8 years. The measurements taken detected displacements from several millimetres to 40 cm set at a depth of 1-17 m. The modern, on-line monitoring and early warning system was installed in May 2010. The system is the first of its kind in Poland and only one of several such real-time systems in the world. The installation was working with the Local Road Authority in Gorlice. It contained three automatic field stations for investigation of landslide parameters to depths of 12-16 m and weather station. In-place tilt transducers and innovative 3D continuous inclinometer systems with sensors located every 0.5 m were used. It has the possibility of measuring a much greater range of movements compared to standard systems. The conventional and real-time data obtained provided a better recognition of the triggering parameters and the control of geohazard stabilizations. The monitoring methods chosen supplemented by numerical modelling could lead to more reliable forecasting of such landslides and could thus provide better control and landslide remediation possibilities also to stabilization works which prevent landslides.

  14. Comparison of Logistic Regression and Random Forests techniques for shallow landslide susceptibility assessment in Giampilieri (NE Sicily, Italy)

    NASA Astrophysics Data System (ADS)

    Trigila, Alessandro; Iadanza, Carla; Esposito, Carlo; Scarascia-Mugnozza, Gabriele

    2015-11-01

    The aim of this work is to define reliable susceptibility models for shallow landslides using Logistic Regression and Random Forests multivariate statistical techniques. The study area, located in North-East Sicily, was hit on October 1st 2009 by a severe rainstorm (225 mm of cumulative rainfall in 7 h) which caused flash floods and more than 1000 landslides. Several small villages, such as Giampilieri, were hit with 31 fatalities, 6 missing persons and damage to buildings and transportation infrastructures. Landslides, mainly types such as earth and debris translational slides evolving into debris flows, were triggered on steep slopes and involved colluvium and regolith materials which cover the underlying metamorphic bedrock. The work has been carried out with the following steps: i) realization of a detailed event landslide inventory map through field surveys coupled with observation of high resolution aerial colour orthophoto; ii) identification of landslide source areas; iii) data preparation of landslide controlling factors and descriptive statistics based on a bivariate method (Frequency Ratio) to get an initial overview on existing relationships between causative factors and shallow landslide source areas; iv) choice of criteria for the selection and sizing of the mapping unit; v) implementation of 5 multivariate statistical susceptibility models based on Logistic Regression and Random Forests techniques and focused on landslide source areas; vi) evaluation of the influence of sample size and type of sampling on results and performance of the models; vii) evaluation of the predictive capabilities of the models using ROC curve, AUC and contingency tables; viii) comparison of model results and obtained susceptibility maps; and ix) analysis of temporal variation of landslide susceptibility related to input parameter changes. Models based on Logistic Regression and Random Forests have demonstrated excellent predictive capabilities. Land use and wildfire

  15. Nivation landforms in the western Great Basin and their paleoclimatic significance

    USGS Publications Warehouse

    Dohrenwend, J.C.

    1984-01-01

    More than 10,000 nivation landforms occur in the higher mountain ranges of the western Great Basin. They range from small, subtle hollows with head scarps a few meters high and a few tens of meters long to broad, clearly defined terraces as much as 220 m wide bounded by bold, steeply sloping head scarps as much as 30 m high and 1600 m long. Distribution of these nivation hollows is strongly influenced by elevation, slope orientation, local relief, and substrate lithology. About 95% occur between 2200 and 3000 m elevation, and nearly 80% are situated on north-northwest-to east-northeast-facing slopes. They occur mainly in areas of moderately sloping terrain and moderate local relief, and they are preferentially developed on relatively incompetent substrates including terrigenous sedimentary deposits, volcanic and metavolcanic rocks of intermediate composition, and deeply weathered granitoid rocks. Nearly all of these nivation hollows are relict. They are most abundant near areas of late Pleistocene glaciation but rarely occur within such areas. Most are veneered with colluvium and are well vegetated, and many hollows in the Mono Basin area are veneered with volcanic ash at least 700 yr old. Distribution of nivation hollows suggests that (1) the full-glacial nivation threshold altitude (NTA) rose from north to south at 190 m per degree of latitude, subparallel to, and approximately 740 m lower than, the full-glacial equilibrium-line altitude (ELA) and about 1370 m lower than the estimated modern ELA; (2) the difference between the full-glacial and modern ELAs indicates an approximate 7??C full-glacial mean-annual-temperature depression throughout the Great Basin; and (3) the full-glacial mean annual temperature at the NTA is estimated to have been approximately 0?? to 1??C, assuming little change in accumulation-season precipitation. ?? 1984.

  16. A record of large earthquakes on the southern Hayward fault for the past 1800 years

    USGS Publications Warehouse

    Lienkaemper, J.J.; Williams, P.L.

    2007-01-01

    This is the second article presenting evidence of the occurrence and timing of paleoearthquakes on the southern Hayward fault as interpreted from trenches excavated within a sag pond at the Tyson's Lagoon site in Fremont, California. We use the information to estimate the mean value and aperiodicity of the fault's recurrence interval (RI): two fundamental parameters for estimation of regional seismic hazard. An earlier article documented the four most recent earthquakes, including the historic 1868 earthquake. In this article we present evidence for at least seven earlier paleoruptures since about A.D. 170. We document these events with evidence for ground rupture, such as the presence of blocky colluvium at the base of the main trace fault scarp, and by corroborating evidence such as simultaneous liquefaction or an increase in deformation immediately below event horizons. The mean RI is 170 ?? 82 yr (1??, standard deviation of the sample), aperiodicity is 0.48, and individual intervals may be expected to range from 30 to 370 yr (95.4% confidence). The mean RI is consistent with the recurrence model of the Working Group on California Earthquake Probabilities (2003) (mean, 161 yr; range, 99 yr [2.5%]; 283 yr [97.5%]). We note that the mean RI for the five most recent events may have been only 138 ?? 58 yr (1??). Hypothesis tests for the shorter RI do not demonstrate that any recent acceleration has occurred compared to the earlier period or the entire 1800-yr record, principally because of inherent uncertainties of the event ages.

  17. Geologic map of the South Sierra Wilderness and South Sierra Roadless area, southern Sierra Nevada, California

    SciTech Connect

    Diggles, M.F. ); Carter, K.E. )

    1993-04-01

    The study area is underlain predominantly by granitoid rocks of the Sierra Nevada batholith. Metamorphic rocks are present in roof pendants mainly in the southwest corner of the study area and consist of quartz-biotite schist, phyllite, quartzite, marble, calc-silicate hornfels, and meta-dacite. Among the seven Triassic and (or) Jurassic plutons are three newly described units that consist of the gabbro of Deer Mountain, the tonalite of Falls Creek, and the quartz diorite of Round Mountain. The map shows one newly described unit that intrudes Triassic rocks: the granodiorite of Monache Creek which is a leucocratic, medium-grained, equi-granular, locally porphyritic biotite hornblende granodiorite. Among the seven Cretaceous plutons are two newly described units. The Cretaceous rocks are generally medium- to coarse-grained, potassium-feldspar porphyritic granite with biotite and minor hornblende; it includes abundant pods of alaskite. The granite of Haiwee Creek is similar but only locally potassium-feldspar porphyritic and with only minor hornblende. Major-element data plotted on Harker diagrams show the older rocks to be higher in iron and magnesium and lower in silica than the younger rocks. There are abundant local pods of alaskite throughout the study area that consist of medium- to coarse-grained, leucocratic granite, alkali-feldspar granite and associated aplite and pegmatite bodies occurring as small pods and highly leucocratic border phases of nearby plutons. Tertiary and Quaternary volcanic rock include the rhyolite of Monache Mountain and Quaternary surficial deposits: fan, stream-channel, colluvium, talus, meadow-filling, rock-glacier, and glacial-moraine deposits. Important structures include the Sierran front fault and a possible extensional feature along which Bacon (1978) suggests Monache Mountain erupted.

  18. Geology of the Harpers Ferry Quadrangle, Virginia, Maryland, and West Virginia

    USGS Publications Warehouse

    Southworth, Scott; Brezinski, David K.

    1996-01-01

    The Harpers Ferry quadrangle covers a portion of the northeast-plunging Blue Ridge-South Mountain anticlinorium, a west-verging allochthonous fold complex of the late Paleozoic Alleghanian orogeny. The core of the anticlinorium consists of high-grade paragneisses and granitic gneisses that are related to the Grenville orogeny. These rocks are intruded by Late Proterozoic metadiabase and metarhyolite dikes and are unconformably overlain by Late Proterozoic metasedimentary rocks of the Swift Run Formation and metavolcanic rocks of the Catoctin Formation, which accumulated during continental rifting of Laurentia (native North America) that resulted in the opening of the Iapetus Ocean. Lower Cambrian metasedimentary rocks of the Loudoun, Weverton, Harpers, and Antietam Formations and carbonate rocks of the Tomstown Formation were deposited in the rift-to-drift transition as the early Paleozoic passive continental margin evolved. The Short Hill fault is an early Paleozoic normal fault that was contractionally reactivated as a thrust fault and folded in the late Paleozoic. The Keedysville detachment is a folded thrust fault at the contact of the Antietam and Tomstown Formations. Late Paleozoic shear zones and thrust faults are common. These rocks were deformed and metamorphosed to greenschist-facies during the formation of the anticlinorium. The Alleghanian deformation was accompanied by a main fold phase and a regional penetrative axial plane cleavage, which was followed by a minor fold phase with crenulation cleavage. Early Jurassic diabase dikes transected the anticlinorium during Mesozoic continental rifting that resulted in the opening of the Atlantic Ocean. Cenozoic deposits that overlie the bedrock include bedrock landslides, terraces, colluvium, and alluvium.

  19. Conditions for generation of fire-related debris flows, Capulin Canyon, New Mexico

    USGS Publications Warehouse

    Cannon, S.H.; Reneau, S.L.

    2000-01-01

    Comparison of the responses of three drainage basins burned by the Dome fire of 1996 in New Mexico is used to identify the hillslope, channel and fire characteristics that indicate a susceptibility specifically to wildfire-related debris flow. Summer thunderstorms generated three distinct erosive responses from each of three basins. The Capulin Canyon basin showed widespread erosive sheetwash and rilling from hillslopes, and severe flooding occurred in the channel; the North Tributary basin exhibited extensive erosion of the mineral soil to a depth of 5 cm and downslope movement of up to boulder-sized material, and at least one debris flow occurred in the channel; negligible surface runoff was observed in the South Tributary basin. The negligible surface runoff observed in the South Tributary basin is attributed to the limited extent and severity of the fire in that basin. The factors that best distinguish between debris-flow producing and flood-producing drainages are drainage basin morphology and lithology. A rugged drainage basin morphology, an average 12 per cent channel gradient, and steep, rough hillslopes coupled with colluvium and soil weathered from volcaniclastic and volcanic rocks promoted the generation of debris flows. A less rugged basin morphology, an average gradient of 5 per cent, and long, smooth slopes mantled with pumice promoted flooding. Flood and debris-flow responses were produced without the presence of water-repellent soils. The continuity and severity of the burn mosaic, the condition of the riparian vegetation, the condition of the fibrous root mat, accumulations of dry ravel and colluvial material in the channel and on hillslopes, and past debris-flow activity, appeared to have little bearing on the distinctive responses of the basins. Published in 2000 by John Wiley and Sons, Ltd.

  20. Instrumental record of debris flow initiation during natural rainfall: Implications for modeling slope stability

    USGS Publications Warehouse

    Montgomery, D.R.; Schmidt, K.M.; Dietrich, W.E.; McKean, J.

    2009-01-01

    The middle of a hillslope hollow in the Oregon Coast Range failed and mobilized as a debris flow during heavy rainfall in November 1996. Automated pressure transducers recorded high spatial variability of pore water pressure within the area that mobilized as a debris flow, which initiated where local upward flow from bedrock developed into overlying colluvium. Postfailure observations of the bedrock surface exposed in the debris flow scar reveal a strong spatial correspondence between elevated piezometric response and water discharging from bedrock fractures. Measurements of apparent root cohesion on the basal (Cb) and lateral (Cl) scarp demonstrate substantial local variability, with areally weighted values of Cb = 0.1 and Cl = 4.6 kPa. Using measured soil properties and basal root strength, the widely used infinite slope model, employed assuming slope parallel groundwater flow, provides a poor prediction of hydrologie conditions at failure. In contrast, a model including lateral root strength (but neglecting lateral frictional strength) gave a predicted critical value of relative soil saturation that fell within the range defined by the arithmetic and geometric mean values at the time of failure. The 3-D slope stability model CLARA-W, used with locally observed pore water pressure, predicted small areas with lower factors of safety within the overall slide mass at sites consistent with field observations of where the failure initiated. This highly variable and localized nature of small areas of high pore pressure that can trigger slope failure means, however, that substantial uncertainty appears inevitable for estimating hydrologie conditions within incipient debris flows under natural conditions. Copyright 2009 by the American Geophysical Union.

  1. Challenges in Modeling Debris-Flow Initiation during the Exceptional September 2013 Northern Colorado Front Range Rainstorm

    NASA Astrophysics Data System (ADS)

    Baum, R. L.; Coe, J. A.; Godt, J.; Kean, J. W.

    2014-12-01

    Heavy rainfall during 9 - 13 September 2013 induced about 1100 debris flows in the foothills and mountains of the northern Colorado Front Range. Eye-witness accounts and fire-department records put the times of greatest landslide activity during the times of heaviest rainfall on September 12 - 13. Antecedent soil moisture was relatively low, particularly at elevations below 2250 m where many of the debris flows occurred, based on 45 - 125 mm of summer precipitation and absence of rainfall for about 2 weeks before the storm. Mapping from post-event imagery and field observations indicated that most debris flows initiated as small, shallow landslides. These landslides typically formed in colluvium that consisted of angular clasts in a sandy or silty matrix, depending on the nature of the parent bedrock. Weathered bedrock was partially exposed in the basal surfaces of many of the shallow source areas at depths ranging from 0.2 to 5 m, and source areas commonly occupied less than 500 m2. Although 49% of the source areas occurred in swales and 3 % in channels, where convergent flow might have contributed to pore-pressure build up during the rainfall, 48% of the source areas occurred on open slopes. Upslope contributing areas of most landslides (58%) were small (< 1000 m2) and 78% of the slides occurred on south-facing slopes (90°≤ aspect ≤270°). These observations pose challenges for modeling initiation of the debris flows. Effects of variable soil depth and properties, vegetation, and rainfall must be examined to explain the dominance of debris flows on south-facing slopes. Accounting for the small sizes and mixed swale and open-slope settings of source areas demands new approaches for resolving soil-depth and physical-properties variability. The low-moisture initial conditions require consideration of unsaturated zone effects. Ongoing fieldwork and computational modeling are aimed at addressing these challenges related to initiation of the September 2013 debris

  2. Late Quaternary Surface Rupture Along the Seattle Fault Zone Near Bellevue, Washington

    NASA Astrophysics Data System (ADS)

    Sherrod, B. L.

    2002-12-01

    Fault strands in the eastern part of the Seattle fault zone (SFZ) ruptured the ground surface at least two times in late Quaternary time. Previous paleoseismic evidence for late Holocene surface faulting along the SFZ focused on north-dipping thrust faults between Seattle and Bremerton. In contrast, several exposures along the SFZ east of Seattle show surface rupture on south-dipping thrust faults. At Factoria, about 12 km east of Seattle, a ravine crossing the fault zone exposes proglacial lake sediments thrust over younger outwash to the north. Locally, this fault may account for a south side up topographic scarp. At Vasa Park on the west shore of Lake Sammamish about 16 km east of Seattle, recent excavations at two sites (RipRap and Blackberry) exposed a W to NNW-striking fault zone. At the RipRap site, NNW-striking subvertical dip-slip faults form a contact between glacial till and Miocene bedrock, and appear to accommodate bedding-plane slip in the steeply dipping till. The vertical faults merge upward with or are truncated by SW-dipping thrust faults in the overlying bedrock. A radiocarbon age on charcoal immediately overlying bedrock-derived colluvium suggests that the last event occurred between ~16,000 and ~4500 years BP. At the Blackberry trench about 200 m east of the RipRap site, Miocene volcanic mudstone and Quaternary glacial deposits are thrust northward over late Quaternary glacial deposits and a Holocene forest soil. Stratigraphic relationships suggest at least 3 m of horizontal motion and 2m of vertical motion during the last earthquake. A radiocarbon age on charcoal at the top of the buried soil indicates that the last event postdates 11550+/-40 years BP. Pending radiocarbon analyses will help refine the age of the last event. Thrusts cut by a Pleistocene (?) stream channel eroded into the hanging wall suggest at least one earlier episode of faulting.

  3. Land use history, floodplain development, and soil erosion in the vicinity of a millstone production center since the Iron Age in the Segbachtal near Mayen (eastern Eifel, Germany)

    NASA Astrophysics Data System (ADS)

    Dotterweich, Markus; Wenzel, Stefan; Schreg, Rainer; Fülling, Alexander; Engel, Max

    2015-04-01

    In Roman times, the stone and pottery production near Mayen in western Germany reached a very high intensity which would have satisfied the needs of a much wider area. The rate and volume of production was unprecedented and never reached the same level thereafter. The Segbach valley study site with an area of only a few square kilometres offers a very special geoarchaeological archive. The Roman land use structures were completely preserved under a 2 meter thick layer of sediment and are now partially exposed in a gully due to erosion. Pedological, sedimentological and geophysical studies at the colluvium and floodplain sediments as well as relict field structures showed that in the last 2500 years there has been a considerable human impact on both water and sediment budgets. This also had various implications on the further development of water courses, soils and relief. Evidence for the development of flood plain sediments can be traced as far back as the late La Tène period, the Roman Iron Age, and since the Middle Ages. On one particular south-facing slope we found evidence of recultivation measures on a former quarry tailing heap dating from the Middle Ages. This and other human construction activities and land uses lead to a significant change in erosion and sedimentation patterns. It is surprising that sedimentation in flood plains was largely absent during the Roman Iron Age despite intensive land use. Evidence shows that flash flood events with intensive accumulation of soil matter in flood plains only occurred during the High Middle Ages. Sediments from the late Middle ages and the Modern Times are largely missing. The research undertaken in Segbach valley not only offers new insights into specific local historical land uses and land use changes but also fundamental knowledge about the principles and impacts of long-term human-environment interactions.

  4. Hydro-geochemical appraisal of groundwater quality from weathered basement aquifers in Northern Malawi

    NASA Astrophysics Data System (ADS)

    Wanda, Elijah; Monjerezi, Maurice; Mwatseteza, Jonas F.; Kazembe, Lawrence N.

    The obligation to ensure adequate potable water supply to everyone, has necessitated the development of groundwater resources for reliable rural water supply in most developing countries. An understanding of spatial variation and processes affecting water quality is essential in sustaining usable water supplies under changing climate and local environmental pressures. In this study, an assessment of quality and dominant hydro-geochemical processes affecting the quality of groundwater from weathered basement aquifers in Mzimba district, Northern Malawi, has been conducted. Groundwater samples were collected from 172 hand-pumped boreholes, drilled for domestic rural water supply and analysed for major and minor ions, pH and total dissolved solids (TDS). In general, groundwater is of low mineralisation (TDS range: 29-1896 mg L -1 for the dry season), with hydro-geochemical facies dominated by Ca-HCO 3, which evolves to Ca-Cl water type. Multivariate statistical analysis (HCA and PCA) and geochemical interpretation showed that the Ca-HCO 3 groundwater type result from hydrolysis of silicate minerals, which causes the solution to reach equilibrium with kaolinite. The processes of cation exchange of Na + and K + in the groundwater for Ca 2+ and Mg 2+ on clay minerals, carbonate precipitation and evaporation, are shown to modify the chemical composition from Ca-HCO 3 types to Ca-Cl types. Groundwater is generally of good quality in both rainy and dry seasons, with little seasonal changes. The United States Salinity Laboratory Staff and Wilcox diagrams showed that most samples were also suitable for irrigation except for 4% (eight samples) of the groundwater samples (with EC > 2000 μS cm -1). These are located in alluviums and colluviums localised near river banks and in inter hill valleys.

  5. Drilling and coring methods that minimize the disturbance of cuttings, core, and rock formation in the unsaturated zone, Yucca Mountain, Nevada

    SciTech Connect

    Hammermeister, D.P.; Blout, D.O.; McDaniel, J.C.

    1985-12-31

    A drilling-and-casing method (Odex 115 system) utilizing air as a drilling fluid was used successfully to drill through various rock types within the unsaturated zone at Yucca Mountain, Nevada. This paper describes this method and the equipment used to rapidly penetrate bouldery alluvial-colluvial deposits, poorly consolidated bedded and nonwelded tuff, and fractured, densely welded tuff to depths of about 130 meters. A comparison of water-content and water-potential data from drill cuttings with similar measurements on rock cores indicates that drill cuttings were only slightly disturbed for several of the rock types penetrated. Coring, sampling, and handling methods were devised to obtain minimally disturbed drive core from bouldery alluvial-colluvial deposits. Bulk-density values obtained from bulk samples dug from nearby trenches were compared to bulk-density values obtained from drive core to determine the effects of drive coring on the porosity of the core. Rotary coring methods utilizing a triple-tube core barrel and air as the drilling fluid were used to obtain core from welded and nonwelded tuff. Results indicate that the disturbance of the water content of the core was minimal. Water-content distributions in alluvium-colluvium were determined before drilling occurred by drive-core methods. After drilling, water-content distributions were determined by nuclear-logging methods. A comparison of the water-content distributions made before and after drilling indicates that Odex 115 drilling minimally disturbs the water content of the formation rock. 10 refs., 12 figs., 4 tabs.

  6. Tartarus Colles: A sampling of the Martian highlands

    NASA Technical Reports Server (NTRS)

    Murchie, Scott; Treiman, Allan

    1994-01-01

    Several of the most fundamental issues about the geology of Mars can be addressed using information on composition and structure of the plateau plains ('highlands') that cover approximately half the planet. The units that compose the highlands are interpreted as a mixture of volcanic, fluvial, lacustrine, and impact ejecta deposits. A more precise inventory of differing of igneous and sedimentary lithologies in highland rock units would not only lead to a better understanding of how the plateau plains formed, but would also clarify the nature of the surface environment during the first 800 m.y. of martian history. Structural features including bedforms, joints, and small faults that are unresolved from orbit record a history of the emplacement and deformation of the highlands. In addition, weathering products present in this very ancient terrain represent a mineralogic record of past climate and of the pathways by which bedrock is altered chemically. Their similarity or dissimilarity to bright soils observed spectroscopically and in situ at the Viking Lander sites will be evidence for the relative roles of regional sources and global eolian transport in producing the widespread cover of 'dust.' Unfortunately, these issues are difficult to address in the plateau plains proper, because bedrock is covered by mobile sand and weathering products, which dominate both surface composition and remotely measurable spectral properties. However, the 'Tartarus Colles' site, located at 11.41 deg N, 197.69 deg W at an elevation of -1 km, provides an excellent opportunity to address the highland geology within the mission constraints of Mars Pathfinder. The site is mapped as unit HNu, and consists of knobby remnants of deeply eroded highlands. It contains rolling hills, but lacks steep escarpments and massifs common in most highland remnants, and is free of large channels that would have removed colluvium from eroded upper portions of the stratigraphic column. These

  7. Tartarus Colles: A sampling of the Martian highlands

    NASA Astrophysics Data System (ADS)

    Murchie, Scott; Treiman, Allan

    Several of the most fundamental issues about the geology of Mars can be addressed using information on composition and structure of the plateau plains ('highlands') that cover approximately half the planet. The units that compose the highlands are interpreted as a mixture of volcanic, fluvial, lacustrine, and impact ejecta deposits. A more precise inventory of differing of igneous and sedimentary lithologies in highland rock units would not only lead to a better understanding of how the plateau plains formed, but would also clarify the nature of the surface environment during the first 800 m.y. of martian history. Structural features including bedforms, joints, and small faults that are unresolved from orbit record a history of the emplacement and deformation of the highlands. In addition, weathering products present in this very ancient terrain represent a mineralogic record of past climate and of the pathways by which bedrock is altered chemically. Their similarity or dissimilarity to bright soils observed spectroscopically and in situ at the Viking Lander sites will be evidence for the relative roles of regional sources and global eolian transport in producing the widespread cover of 'dust.' Unfortunately, these issues are difficult to address in the plateau plains proper, because bedrock is covered by mobile sand and weathering products, which dominate both surface composition and remotely measurable spectral properties. However, the 'Tartarus Colles' site, located at 11.41 deg N, 197.69 deg W at an elevation of -1 km, provides an excellent opportunity to address the highland geology within the mission constraints of Mars Pathfinder. The site is mapped as unit HNu, and consists of knobby remnants of deeply eroded highlands. It contains rolling hills, but lacks steep escarpments and massifs common in most highland remnants, and is free of large channels that would have removed colluvium from eroded upper portions of the stratigraphic column. These

  8. Late Quaternary climate and landscape changes in Southern Africa based on integrative analyses of geoarchives

    NASA Astrophysics Data System (ADS)

    Huerkamp, K.; Voelkel, J.; Heine, K.; Bens, O.; Winkelbauer, J.

    2009-12-01

    Although it is clear that large, rapid temperature changes have occurred during the last glacial-interglacial cycle and the Holocene in Southern Africa, we have only limited, and often imprecise, knowledge of how the major moisture-bearing atmospheric circulation systems have reacted to these changes. Using slope deposits, soils and sediments as palaeoclimatic geoarchives we will overcome these constraints. The role of many geoarchives in the reconstruction of the Quaternary climate in Southern Africa remains controversial, since the palaeoclimate data are based on evidence from marine cores, lake sediments, speleothems and spring sinter, fluvial sediments, aeolian sands and dust, colluvium, and coastal sediments. To elucidate climate controls on Quaternary landscape evolution and to use these data for palaeoclimatic reconstructions, slope deposits, soils and sediments have been investigated. The project will employ state-of-the-art geoscience methodology to interpret the record of precipitation changes of the Late Quaternary, including the shifting of the summer and winter rain belts, the chronology of catastrophic floods, the wind intensity and direction, and the role climatic factors may have played for prehistoric cultures. High resolution Late Quaternary records are provided by analysing the interstratification of slope deposits and soils with fluvial, lacustrine and aeolian sediment sequences. Earlier research has shown that aeolian and fluvial processes were active at the same time in the southwestern Kalahari during the LGM, documented by sequences of alternate bedding of aeolian, colluvial and fluvial sediments. The interfingering of slope deposits with fluvial flood sediments (slackwater deposits) in Namib Desert valleys document extreme precipitation events in the upper highland catchments and rains at the same time in the desert itself.

  9. Geologic map of the Montauk quadrangle, Dent, Texas, and Shannon Counties, Missouri

    USGS Publications Warehouse

    Weary, David J.

    2015-04-30

    The Montauk 7.5-minute quadrangle is located in south-central Missouri within the Salem Plateau region of the Ozark Plateaus physiographic province. About 2,000 feet (ft) of flat-lying to gently dipping lower Paleozoic sedimentary rocks, mostly dolomite, chert, sandstone, and orthoquartzite, overlie Mesoproterozoic igneous basement rocks. Unconsolidated residuum, colluvium, terrace deposits, and alluvium overlie the sedimentary rocks. Numerous karst features, such as caves, springs, and sinkholes, have formed in the carbonate rocks. Many streams are spring fed. The topography is a dissected karst plain with elevations ranging from approximately 830 ft where the Current River exits the middle-eastern edge of the quadrangle to about 1,320 ft in sec. 16, T. 31 N., R. 7 W., in the southwestern part of the quadrangle. The most prominent physiographic features within the quadrangle are the deeply incised valleys of the Current River and its major tributaries located in the center of the map area. The Montauk quadrangle is named for Montauk Springs, a cluster of several springs that resurge in sec. 22, T. 32 N., R. 7 W. These springs supply clean, cold water for the Montauk Fish Hatchery, and the addition of their flow to that of Pigeon Creek produces the headwaters of the Current River, the centerpiece of the Ozark National Scenic Riverways park. Most of the land in the quadrangle is privately owned and used primarily for grazing cattle and horses and growing timber. A smaller portion of the land within the quadrangle is publicly owned by either Montauk State Park or the Ozark National Scenic Riverways (National Park Service). Geologic mapping for this investigation was conducted in 2007 and 2009.

  10. Evidence for a twelfth large earthquake on the southern hayward fault in the past 1900 years

    USGS Publications Warehouse

    Lienkaemper, J.J.; Williams, P.L.; Guilderson, T.P.

    2010-01-01

    We present age and stratigraphic evidence for an additional paleoearthquake at the Tyson Lagoon site. The acquisition of 19 additional radiocarbon dates and the inclusion of this additional event has resolved a large age discrepancy in our earlier earthquake chronology. The age of event E10 was previously poorly constrained, thus increasing the uncertainty in the mean recurrence interval (RI), a critical factor in seismic hazard evaluation. Reinspection of many trench logs revealed substantial evidence suggesting that an additional earthquake occurred between E10 and E9 within unit u45. Strata in older u45 are faulted in the main fault zone and overlain by scarp colluviums in two locations.We conclude that an additional surfacerupturing event (E9.5) occurred between E9 and E10. Since 91 A.D. (??40 yr, 1??), 11 paleoearthquakes preceded the M 6:8 earthquake in 1868, yielding a mean RI of 161 ?? 65 yr (1??, standard deviation of recurrence intervals). However, the standard error of the mean (SEM) is well determined at ??10 yr. Since ~1300 A.D., the mean rate has increased slightly, but is indistinguishable from the overall rate within the uncertainties. Recurrence for the 12-event sequence seems fairly regular: the coefficient of variation is 0.40, and it yields a 30-yr earthquake probability of 29%. The apparent regularity in timing implied by this earthquake chronology lends support for the use of time-dependent renewal models rather than assuming a random process to forecast earthquakes, at least for the southern Hayward fault.

  11. Shallow electrical resistivity imaging of the Limón fault, Chagres River Watershed, Panama Canal

    NASA Astrophysics Data System (ADS)

    Mojica, Alexis; Pérez, Tatiana; Toral, Jaime; Miranda, Roberto; Franceschi, Pastora; Calderón, Carlos; Vergara, Fidedigna

    2017-03-01

    The aim of this study was the use of electrical resistivity imaging to investigate the geometry of the southwest portion of one of the most important geologic fault zones of the Panama Canal Watershed: the Limón fault. This fault is characterized by its juxtaposition of pre-Tertiary andesitic basalt (Playa Venado Formation) against late Oligocene Tertiary sediments (Caimito Formation). In this zone, four 2D electrical resistivity tomography profiles were conducted perpendicular to the fault trace: T-1, T-2, T-3 and T-4. The T-1, T-3, and T-4 profiles were long profiles (235 m for the first two and 215 m for the last one), with a goal of determining the depth of the geologic boundary between the sedimentary and andesitic deposits. The T-2 profile was a short profile (23.5 m), with the objective of calibrating the results with data provided by the paleoseismic trenching previously developed in the area of interest. For these tests, two electrode arrays of types Wenner-Schlumberger and Dipole-Dipole, were used. For the inversion routine, two regularized least-squares methods were used: the smoothness-constrained method and robust inversion. The long electrical resistivity tomography profiles were able to identify a set of electrical anomalies associated with the andesitic basalt and the Tertiary sediments and with that, the contact geometry between these formations. In these profiles, fault angle measurements ranged from 60° to 80° with respect to the ground surface. In the T-2 profile, the electrical anomalies showed a good association with the results of the paleoseismic study. This allowed identification of the colluvium and alluvium covering the gravel and sand debris that mark the gradual transition to the soils of the Caimito Formation. Finally, a set of 2D synthetic models was developed for each of the T-1, T-3, and T-4 profiles with the objective of optimizing interpretation of the field results.

  12. Reorganization of vegetation, hydrology and soil carbon after permafrost degradation across heterogeneous boreal landscapes

    USGS Publications Warehouse

    Jorgenson, M. Torre; Harden, Jennifer; Kanevskiy, Mikhail; O'Donnell, Jonathan; Wickland, Kim; Ewing, Stephanie; Manies, Kristen; Zhuang, Qianlai; Shur, Yuri; Striegl, Robert; Koch, Josh

    2013-01-01

    The diversity of ecosystems across boreal landscapes, successional changes after disturbance and complicated permafrost histories, present enormous challenges for assessing how vegetation, water and soil carbon may respond to climate change in boreal regions. To address this complexity, we used a chronosequence approach to assess changes in vegetation composition, water storage and soil organic carbon (SOC) stocks along successional gradients within four landscapes: (1) rocky uplands on ice-poor hillside colluvium, (2) silty uplands on extremely ice-rich loess, (3) gravelly–sandy lowlands on ice-poor eolian sand and (4) peaty–silty lowlands on thick ice-rich peat deposits over reworked lowland loess. In rocky uplands, after fire permafrost thawed rapidly due to low ice contents, soils became well drained and SOC stocks decreased slightly. In silty uplands, after fire permafrost persisted, soils remained saturated and SOC decreased slightly. In gravelly–sandy lowlands where permafrost persisted in drier forest soils, loss of deeper permafrost around lakes has allowed recent widespread drainage of lakes that has exposed limnic material with high SOC to aerobic decomposition. In peaty–silty lowlands, 2–4 m of thaw settlement led to fragmented drainage patterns in isolated thermokarst bogs and flooding of soils, and surface soils accumulated new bog peat. We were not able to detect SOC changes in deeper soils, however, due to high variability. Complicated soil stratigraphy revealed that permafrost has repeatedly aggraded and degraded in all landscapes during the Holocene, although in silty uplands only the upper permafrost was affected. Overall, permafrost thaw has led to the reorganization of vegetation, water storage and flow paths, and patterns of SOC accumulation. However, changes have occurred over different timescales among landscapes: over decades in rocky uplands and gravelly–sandy lowlands in response to fire and lake drainage, over decades to

  13. Kinematic indicators on active normal faults in Western Turkey

    NASA Astrophysics Data System (ADS)

    Hancock, P. L.; Barka, A. A.

    Quaternary normal fault zones in western Turkey comprise multiple slip planes and zone-parallel layers of fault breccia. They also contain several little-known kinematic indicators that are probably typical of many formed at shallow levels in extending terrains. The recent exhumation by contractors of about 2000 m 2 of slip planes in a SSE-dipping fault zone separating Quaternary colluvium from bedrock carbonates at Yavansu (7 km SE of Kuşadasi) permits an unusually complete inventory of the indicators to be compiled. The most spectacular indicators are metre-scale 69°W-pitching corrugations in slip planes and recemented breccia sheets underlying them. Corrugations, characterized by sinusoidal profiles normal to their long axes and, less commonly, culminations and depression along their axes possibly developed as a result of upwards-propagating slip planes seeking undemanding pathways through heterogeneous fault-precursor breccias that formed in advance of tip lines. Parallel to corrugation long axes are those of gutters, flat-floored, sleep-sided channels a few centimetres wide, probably related to the abrasion of subslip-plane breccia sheets. Centimetre-scale tool tracks scored in the uppermost subslip-plane breccia sheet by resistant colluvial clasts are irregular at their proximal ends but distally they swing into alignment with corrugation axes. Frictional-wear striae, centimetres long but only a few millimetres wide and pitching 78°W, are superimposed on the other slip-parallel lineations. Comb fractures nearly perpendicular to slip planes define an intersection lineation which is normal to corrugation axes. Fault-plane solutions of earthquakes on SSE-dipping active faults in the West Anatolian extensional province indicate that mainly normal, combined with minor dextral slip is the dominant mode, a conclusion in accord with the sense of slip inferred from the indicators exposed on the Yavansu slip planes.

  14. Heavy rainfall intensity triggering the landslide at Sungai Ruil Cameron Highland Malaysia - A Case study

    NASA Astrophysics Data System (ADS)

    Jaafar, K. B.

    2012-04-01

    Landslide in the village of Sungai Ruil, Brinchang, Cameron Highlands, Malaysia occurred on August 7, 2011 at 5:50 pm. This incident has caused six houses buried by debris or mud which engaged seven fatalities and two injuries This landslide has been classified as landslide debris flow. Total area of the village involved is around 40 hectares whilst the catchment area of the village is around 80 hectares. The landslide forensic investigation was carried out to identify the caused of the failure. There are three methods in conducting the study that involved geological mapping and interpretation for assessment of geological hazards. The second method is the debris flow hazard assessment in all the drainage including rainfall analysis. The rainfall analysis was carried out to produce the snake line and critical line. The third method is an analysis of slope stability in locations with high potential of slope failure in the area. There are three factors identified that resulted from this incident. The first factor is the presence of geological factors weakness (covered by colluviums), weathered material, orientation and location of adversely discontinuities and relict slope failure. While the second factor is the appearance of the morphology of hilly terrain, presence of channel order 0 or 'ephemeral drainage' and river bed gradient more than 35 degrees. The third factor is human activity that build water barrier. While the high intensity of rainfall in a short period of time is believed to be a triggering factor. This paper will discuss in detail on how intensity and duration of rainfall induce the landslide and predict the threshold value at the area.

  15. Late Cenozoic surficial deposits and valley evolution of unglaciated northern New Jersey

    USGS Publications Warehouse

    Stanford, S.D.

    1993-01-01

    Multiple alluvial, colluvial, and eolian deposits in unglaciated northern New Jersey, and the eroded bedrock surfaces on which they rest, provide evidence of both long-term valley evolution driven by sustained eustatic baselevel lowering and short-term filling and excavation of valleys during glacial and interglacial climate cycles. The long-term changes occur over durations of 106 years, the short-term features evolve over durations of 104 to 105 years. Direct glacial effects, including blockage of valleys by glacial ice and sediment, and valley gradient reversals induced by crustal depression, are relatively sudden changes that account for several major Pleistocene drainage shifts. After deposition of the Beacon Hill fluvial gravel in the Late Miocene, lowering of sea level, perhaps in response to growth of the Antarctic ice sheet, led to almost complete dissection of the gravel. A suite of alluvial, colluvial, and eolian sediments was deposited in the dissected landscape. The fluvial Bridgeton Formation was deposited in the Raritan lowland, in the Amboy-Trenton lowland, and in the Delaware valley. Following southeastward diversion of the main Bridgeton river, perhaps during Late Pliocene or Early Pleistocene glaciation, northeastward drainage was established on the inactive Bridgeton fluvial plain. About 30 to 45 m of entrenchment followed, forming narrow, incised valleys within which Late Pleistocene deposits rest. This entrenchment may have occurred in response to lowered sea level caused by growth of ice sheets in the northern hemisphere. Under periglacial conditions in the Middle and Late Pleistocene, valleys were partially filled with alluvium and colluvium. During interglacials slopes were stabilized by vegetation and the alluvial and colluvial valley-fill was excavated by gullying, bank erosion, and spring sapping. During Illinoian and late Wisconsinan glaciation, the lower Raritan River was diverted when glacial deposits blocked its valley, and the

  16. The Temporal and Spatial Quantification of Holocene Sediment Dynamics in a meso-scale catchment in northern Bavaria/Germany

    NASA Astrophysics Data System (ADS)

    Fuchs, Markus; Will, Mathias; Kreutzer, Sebastian

    2013-04-01

    The Aufsess River catchment (97 km2) in northern Bavaria, Germany, is studied to establish a Holocene sediment budget and to investigate the sediment dynamics since the early times of farming in the 3rd millennium BCE. The temporal characterization of the sediment dynamics is based on an intensive dating program with 73 OSL and 14 14C ages. To estimate soil erosion and deposition, colluvial and alluvial archives are investigated in the field by piling and trenching, supported by laboratory analyses. The sediment budget shows that 58% of these sediments are stored as colluvium in on- and foot-slope positions, 9% are stored as alluvium in the floodplains and 33% are exported from the Aufsess River catchment. Colluviation starts in the End-Neolithic (ca. 3100 BCE), while first indicators of soil erosion derived alluviation is recorded ca. 2-3 ka later. The pattern of sedimentation rates also displays differences between the colluvial and alluvial system, with a distinct increase in the Middle Ages (ca. 1000 CE) for the alluvial system, while the colluvial system records low sedimentation rates for this period. A contrast is also observed since Modern Times (ca. 1500 CE), with increasing sedimentation rates for the colluvial system, whereas the alluvial system records decreasing rates. The different behavior of the colluvial and alluvial system clearly shows the non-linear behavior of the catchment's fluvial system. The results further suggest that human impact is most probably the dominant factor influencing the sediment dynamics of the catchment since the introduction of farming. Fuchs, M., Will, M., Kunert, E., Kreutzer, S., Fischer, M. & Reverman, R. 2011. The temporal and spatial quantification of Holocene sediment dynamics in a meso-scale catchment in northern Bavaria / Germany. The Holocene 21, 1093-1104. Fuchs, M., Fischer, M. & Reverman, R. 2010. Colluvial and alluvial sediment archives temporally resolved by OSL dating: Implications for reconstructing soil

  17. Geologic map of the Boulder-Fort Collins-Greeley Area, Colorado

    USGS Publications Warehouse

    Colton, Roger B.

    1978-01-01

    This digital map shows the geographic extent of rock stratigraphic units (formations) as compiled by Colton in 1976 under the Front Range Urban Corridor Geology Program. Colton used his own geologic mapping and previously published geologic maps to compile one map having a single classification of geologic units. The resulting published color paper map (USGS Map I-855-G, Colton, 1978) was intended for land-use planning and to depict the regional geology. In 1997-1999, another USGS project designed to address urban growth issues was undertaken. This project, the USGS Front Range Infrastructure Resources Project, undertook to digitize Colton's map at 1:100,000 scale, making it useable in Geographical Information Systems (GIS). That product is described here. In general, the digitized map depicts in its western part Precambrian igneous and metamorphic rocks, Pennsylvanian and younger sedimentary rock units, major faults, and brecciated zones along an eastern strip (5-20 km wide) of the Front Range. The central and eastern parts of the map (Colorado Piedmont) show a mantle of Quaternary unconsolidated deposits and interspersed outcrops of sedimentary rock of Cretaceous or Tertiary age. A surficial mantle of unconsolidated deposits of Quaternary age is differentiated and depicted as eolium (wind-blown sand and silt), alluvium (river gravel, sand, and silt of variable composition), colluvium, and a few landslide deposits. At the mountain front, north-trending, Paleozoic and Mesozoic formations of sandstone, shale, and minor limestone dip mostly eastward and form folds, fault blocks, hogbacks and intervening valleys. Local dikes and sills of Tertiary rhyodacite and basalt intrude rocks near the range front, mostly in the Boulder area.

  18. Terrestrial slopes in northern high latitudes: A paradigm shift regarding sediment origin, composition, and dynamic evolution

    NASA Astrophysics Data System (ADS)

    Lønne, Ida

    2017-01-01

    High-Arctic terrestrial slopes have received limited systematic research interest, but increased vulnerability related to regional warming has driven the call for better knowledge of the dynamics of these systems. Studies of sediment transport from a plateau area in Adventdalen, Svalbard, and associated slopes extending to sea level demonstrate that glacial processes play a more prominent role than earlier anticipated, - especially the impact of glacial meltwater. Traces of drainage at the plateau and the dissection of the plateau edge and upper slope were clearly initiated during various stages of Late Glacial runoff. Further, there is a close association between the sediment distribution and composition at the plateau and the evolution of various types of slopes. The reconstructed sedimentation history shows that the landscape will undergo four stages with contrasting modes of sediment transport: 1) subglacial processes related to active ice, 2) processes related to the margin of active ice, 3) processes related to the melting of inactive ice, and 4) nonglacial processes. These stages form four successions, referred to as supply regimes A-D, which control the supply of water and sediments to a given slope segment. In this landscape, traces of glacial meltwater occur at most altitudes, in "odd" positions and in slope segments "without" catchments. The associated depocenters (isolated, composite or coalescing into aprons), are often outsized compared to the apparent slope catchment. Reworked glacial sediments form a significant part of the slope-debris but are covered partly or entirely by products of physical weathering. Colluvium, senso stricto, thus masks a distinct system shift related to the local termination of glacial meltwater. Consequently, the weathering part of the slope sediment budget in this region is considerably overestimated.

  19. Dip-slope and Dip-slope Failures in Taiwan - a Review

    NASA Astrophysics Data System (ADS)

    Lee, C.

    2011-12-01

    Taiwan is famous for dip-slope and dip-slope slides. Dip-slopes exist at many places in the fold-and-thrust belt of Taiwan. Under active cutting of stream channels and man-made excavations, a dip-slope may become unstable and susceptible for mass sliding. Daylight of a bedding parallel clay seam is the most dangerous type for dip-slope sliding. Buckling or shear-off features may also happen at toe of a long dip-slope. Besides, a dip-slope is also dangerous for shallow debris slides, if the slope angle is between 25 to 45 degrees and the debris (colluvium or slope wash) is thick (>1m). These unstable slopes may slide during a triggering event, earthquake or typhoon storm; or even slide without a triggering event, like the 2010 Tapu case. Initial buckling feature had been found in the dip-slope of the Feitsui arch dam abutment after detailed explorations. Shear-off feature have also been found in dip-slope located in right bank of the Nahua reservoir after field investigation and drilling. The Chiufengerhshan slide may also be shear-off type. On the other hand, the Tapu, the Tsaoling slides and others are of direct slide type. The Neihoo Bishan slide is a shallow debris slide on dip-slope. All these cases demonstrate the four different types of dip-slope slide. The hazard of a dip-slope should be investigated to cover these possible types of failure. The existence of bedding parallel clay seams is critical for the stability of a dip-slope, either for direct slide or buckling or shear-off type of failure, and is a hot point during investigation. Because, the stability of a dip-slope is changing with time, therefore, detailed explorations to including weathering and erosion rates are also very necessary to ensure the long-term stability of a dip-slope.

  20. Evidence for debris flow gully formation initiated by shallow subsurface water on Mars

    USGS Publications Warehouse

    Lanza, N.L.; Meyer, G.A.; Okubo, C.H.; Newsom, Horton E.; Wiens, R.C.

    2010-01-01

    The morphologies of some martian gullies appear similar to terrestrial features associated with debris flow initiation, erosion, and deposition. On Earth, debris flows are often triggered by shallow subsurface throughflow of liquid water in slope-mantling colluvium. This flow causes increased levels of pore pressure and thus decreased shear strength, which can lead to slide failure of slope materials and subsequent debris flow. The threshold for pore pressure-induced failure creates a distinct relationship between the contributing area supplying the subsurface flow and the slope gradient. To provide initial tests of a similar debris flow initiation hypothesis for martian gullies, measurements of the contributing areas and slope gradients were made at the channel heads of martian gullies seen in three HiRISE stereo pairs. These gullies exhibit morphologies suggestive of debris flows such as leveed channels and lobate debris fans, and have well-defined channel heads and limited evidence for multiple flows. Our results show an area-slope relationship for these martian gullies that is consistent with that observed for terrestrial gullies formed by debris flow, supporting the hypothesis that these gullies formed as the result of saturation of near-surface regolith by a liquid. This model favors a source of liquid that is broadly distributed within the source area and shallow; we suggest that such liquid could be generated by melting of broadly distributed icy materials such as snow or permafrost. This interpretation is strengthened by observations of polygonal and mantled terrain in the study areas, which are both suggestive of near-surface ice. ?? 2009 Elsevier Inc.

  1. Maps of the Bonsall area of the San Luis Rey River valley, San Diego County, California, showing geology, hydrology, and ground-water quality

    USGS Publications Warehouse

    Izbicki, John A.

    1985-01-01

    In November 1984, 84 wells and 1 spring in the Bonsall area of the San Luis Rey River valley were inventoried by U.S. Geological Survey personnel. Depth to water in 38 wells ranged from 1.3 to 38 ft and 23 wells had depths to water less than 10 feet. Dissolved solids concentration of water from 29 wells and 1 spring sampled in autumn 1983 and spring 1984 ranged from 574 to 2,370 mgs/L. Groundwater with a dissolved solids concentration less than 1,000 mgs/L was generally restricted to the eastern part of the aquifer. The total volume of alluvial fill in the Bonsall area is 113,000 acre-feet; the amount of groundwater storage available in the alluvial aquifer is 18,000 acre-feet. The alluvial aquifer is, in part, surrounded and underlain by colluvium and weathered crystalline rock that add some additional groundwater storage capacity to the system. Data in this report are presented on five maps showing well locations , thickness of alluvial fill, water level contours in November 1983 and hydrographs of selected wells, groundwater quality in spring 1960 and graphs showing changes in dissolved solids concentrations of water from selected wells with time, and groundwater quality in spring 1984. This report is part of a larger cooperative project between the Rainbow Municipal Irrigation District and the U.S. Geological Survey. The purpose of the larger project is to develop an appropriate groundwater management plan for the Bonsall area of the San Luis Rey River valley. (USGS)

  2. Gravity and magnetic data in the vicinity of Virgin Valley, southern Nevada

    USGS Publications Warehouse

    Morin, Robert L.

    2006-01-01

    This report contains 10 interpretive cross sections and an integrated text describing the geology of parts of the Colorado, White River, and Death Valley regional ground-water flow systems, Nevada, Utah, and Arizona. The primary purpose of the report is to provide geologic framework data for input into a numerical ground-water model. Therefore, the stratigraphic and structural summaries are written in a hydrogeologic context. The oldest rocks (basement) are Early Proterozoic metamorphic and intrusive crystalline rocks that are considered confining units because of their low permeability. Late Proterozoic to Lower Cambrian clastic units overlie the crystalline rocks and are also considered confining units within the regional flow systems. Above the clastic units are Middle Cambrian to Lower Permian carbonate rocks that are the primary aquifers in the flow systems. The Middle Cambrian to Lower Permian carbonate rocks are overlain by a sequence of mainly clastic rocks of late Paleozoic to Mesozoic age that are mostly considered confining units, but they may be permeable where faulted. Tertiary volcanic and plutonic rocks are exposed in the northern and southern parts of the study area. In the Clover and Delamar Mountains, these rocks are highly deformed by north- and northwest-striking normal and strike-slip faults that are probably important conduits in transmitting ground water from the basins in the northern Colorado and White River flow systems to basins in the southern part of the flow systems. The youngest rocks in the region are Tertiary to Quaternary basin-fill deposits. These rocks consist of middle to late Tertiary sediments consisting of limestone, conglomerate, sandstone, tuff, and gypsum, and younger Quaternary surficial units consisting of alluvium, colluvium, playa deposits, and eolian deposits. Basin-fill deposits are both aquifers and aquitards.

  3. Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington

    USGS Publications Warehouse

    Nelson, A.R.; Johnson, S.Y.; Kelsey, H.M.; Wells, R.E.; Sherrod, B.L.; Pezzopane, S.K.; Bradley, L.-A.; Koehler, R. D.; Bucknam, R.C.

    2003-01-01

    Five trenches across a Holocene fault scarp yield the first radiocarbon-measured earthquake recurrence intervals for a crustal fault in western Washington. The scarp, the first to be revealed by laser imagery, marks the Toe Jam Hill fault, a north-dipping backthrust to the Seattle fault. Folded and faulted strata, liquefaction features, and forest soil A horizons buried by hanging-wall-collapse colluvium record three, or possibly four, earthquakes between 2500 and 1000 yr ago. The most recent earthquake is probably the 1050-1020 cal. (calibrated) yr B.P. (A.D. 900-930) earthquake that raised marine terraces and triggered a tsunami in Puget Sound. Vertical deformation estimated from stratigraphic and surface offsets at trench sites suggests late Holocene earthquake magnitudes near M7, corresponding to surface ruptures >36 km long. Deformation features recording poorly understood latest Pleistocene earthquakes suggest that they were smaller than late Holocene earthquakes. Postglacial earthquake recurrence intervals based on 97 radiocarbon ages, most on detrital charcoal, range from ???12,000 yr to as little as a century or less; corresponding fault-slip rates are 0.2 mm/yr for the past 16,000 yr and 2 mm/yr for the past 2500 yr. Because the Toe Jam Hill fault is a backthrust to the Seattle fault, it may not have ruptured during every earthquake on the Seattle fault. But the earthquake history of the Toe Jam Hill fault is at least a partial proxy for the history of the rest of the Seattle fault zone.

  4. Field and Laboratory Data From an Earthquake History Study of Scarps in the Hanging Wall of the Tacoma Fault, Mason and Pierce Counties, Washington

    USGS Publications Warehouse

    Nelson, Alan R.; Personius, Stephen F.; Sherrod, Brian L.; Buck, Jason; Bradley, Lee-Ann; Henley, Gary; Liberty, Lee M.; Kelsey, Harvey M.; Witter, Robert C.; Koehler, R.D.; Schermer, Elizabeth R.; Nemser, Eliza S.; Cladouhos, Trenton T.

    2008-01-01

    As part of the effort to assess seismic hazard in the Puget Sound region, we map fault scarps on Airborne Laser Swath Mapping (ALSM, an application of LiDAR) imagery (with 2.5-m elevation contours on 1:4,000-scale maps) and show field and laboratory data from backhoe trenches across the scarps that are being used to develop a latest Pleistocene and Holocene history of large earthquakes on the Tacoma fault. We supplement previous Tacoma fault paleoseismic studies with data from five trenches on the hanging wall of the fault. In a new trench across the Catfish Lake scarp, broad folding of more tightly folded glacial sediment does not predate 4.3 ka because detrital charcoal of this age was found in stream-channel sand in the trench beneath the crest of the scarp. A post-4.3-ka age for scarp folding is consistent with previously identified uplift across the fault during AD 770-1160. In the trench across the younger of the two Stansberry Lake scarps, six maximum 14C ages on detrital charcoal in pre-faulting B and C soil horizons and three minimum ages on a tree root in post-faulting colluvium, limit a single oblique-slip (right-lateral) surface faulting event to AD 410-990. Stratigraphy and sedimentary structures in the trench across the older scarp at the same site show eroded glacial sediments, probably cut by a meltwater channel, with no evidence of post-glacial deformation. At the northeast end of the Sunset Beach scarps, charcoal ages in two trenches across graben-forming scarps give a close maximum age of 1.3 ka for graben formation. The ages that best limit the time of faulting and folding in each of the trenches are consistent with the time of the large regional earthquake in southern Puget Sound about AD 900-930.

  5. Surficial geologic maps along the riparian zone of the Animas River and its headwater tributaries, Silverton to Durango, Colorado, with upper Animas River watershed gradient profiles

    USGS Publications Warehouse

    Blair, R.W.; Yager, D.B.; Church, S.E.

    2002-01-01

    This product consists of Adobe Acrobat .PDF format documents for 10 surficial geologic strip maps along the Animas River watershed from its major headwater tributaries, south to Durango, Colorado. The Animas River originates in the San Juan Mountains north of the historic mining town of Silverton, Colorado. The surficial geologic maps identify surficial deposits, such as flood-plain and terrace gravels, alluvial fans, glacial till, talus, colluvium, landslides, and bogs. Sixteen primary units were mapped that included human-related deposits and structures, eight alluvial, four colluvial, one glacial, travertine deposits, and undifferentiated bedrock. Each of the surficial geologic strip maps has .PDF links to surficial geology photographs, which enable the user to take a virtual tour of these deposits. Geochemical data collected from mapped surficial deposits that pre- and postdate mining activity have aided in determining the geochemical baseline in the watershed. Several photographs with their corresponding geochemical baseline profiles are accessible through .PDF links from several of the maps. A single coverage for all surficial deposits mapped is included as an ArcInfo shape file as an Arc Export format .e00 file. A gradient map for major headwater tributary streams to the Animas River is also included. The gradient map has stream segments that are color-coded based on relative variations in slope and .PDF format links to each stream gradient profile. Stream gradients were derived from U.S. Geological Survey 10-m digital elevation model data. This project was accomplished in support of the U.S. Geological Survey's Abandoned Mine Lands Initiative in the San Juan Mountains, Colorado.

  6. Paleoearthquakes and Eolian-dominated fault sedimentation along the Hubbell Spring fault zone near Albuquerque, New Mexico

    USGS Publications Warehouse

    Personius, S.F.; Mahan, S.A.

    2003-01-01

    The Hubbell Spring fault zone forms the modern eastern margin of the Rio Grande rift in the Albuquerque basin of north-central New Mexico. Knowledge of its seismic potential is important because the fault zone transects Kirtland Air Force Base/Sandia National Laboratories and underlies the southern Albuquerque metropolitan area. No earthquakes larger than ML 5.5 have been reported in the last 150 years in this region, so we excavated the first trench across this fault zone to determine its late Quaternary paleoseismic history. Our trench excavations revealed a complex, 16-m-wide fault zone overlain by four tapered blankets of mixed eolian sand and minor colluvium that we infer were deposited after four large-magnitude, surface-rupturing earthquakes. Although the first (oldest) rupture event is undated, we used luminescence (thermoluminescence and infrared-stimulated luminescence) ages to determine that the subsequent three rupture events occurred about 56 ?? 6, 29 ?? 3, and 12 ?? 1 ka. These ages yield recurrence intervals of 27 and 17 k.y. between events and an elapsed time of 12 k.y. since the latest surface-rupturing paleoearthquake. Slip rates are not well constrained, but our preferred average slip rate since rupture event 2 (post-56 ka) is 0.05 mm/yr, and interval slip rates between the last three events are 0.06 and 0.09 mm/yr, respectively. Vertical displacements of 1-2 m per event and probable rupture lengths of 34-43 km indicate probable paleoearthquake magnitudes (Ms or Mw) of 6.8-7.1. Future earthquakes of this size likely would cause strong ground motions in the Albuquerque metropolitan area.

  7. Post-wildfire erosion response in two geologic terrains in the western USA

    USGS Publications Warehouse

    Moody, J.A.; Martin, D.A.; Cannon, S.H.

    2008-01-01

    Volumes of eroded sediment after wildfires vary substantially throughout different geologic terrains across the western United States. These volumes are difficult to compare because they represent the response to rainstorms and runoff with different characteristics. However, by measuring the erosion response as the erodibility efficiency of water to detach and transport sediment on hillslopes and in channels, the erosion response from different geologic terrains can be compared. Specifically, the erodibility efficiency is the percentage of the total available stream power expended to detach, remobilize, or transport a mass of sediment. Erodibility efficiencies were calculated for the (i) initial detachment, and for the (ii) remobilization and transport of sediment on the hillslopes and in the channels after wildfire in two different geological terrains. The initial detachment efficiencies for the main channel and tributary channel in the granitic terrain were 10 ?? 9% and 5 ?? 4% and were similar to those for the volcanic terrain, which were 5 ?? 5% and 1 ?? 1%. No initial detachment efficiency could be measured for the hillslopes in the granitic terrain because hillslope measurements were started after the first major rainstorm. The initial detachment efficiency in the volcanic terrain was 1.3 ?? 0.41%. The average remobilization and transport efficiencies associated with flash floods in the channels also were similar in the granitic (0.18 ?? 0.57%) and volcanic (0.11 ?? 0.41%) terrains. On the hillslope the remobilization and transport efficiency was greater in the volcanic terrain (2.4%) than in the granitic terrain (0.65%). However, this may reflect the reduced sediment availability after the first major rainstorm (30-min maximum rainfall intensity ??? 90??mm h- 1) in the granitic terrain, while easily erodible fine colluvium remained on the hillslope after the first rainstorm (30-min maximum rainfall intensity = 7.2??mm h- 1) in the volcanic terrain. The

  8. An examination of the factors governing the development of karst topography in the Cumberland Valley of Pennsylvania

    SciTech Connect

    Ackerman, R.V. . Dept. of Geological Sciences)

    1993-03-01

    The landscape of the Cumberland Valley of South Central Pennsylvania is dominated by karst topography. A study was initiated to determine if the development of karst was controlled primarily by geologic structure or by lithologic differences. Existing data concerning the geographic locations of karst features, the hydrogeologic characteristics of the Cumberland Valley, and the chemistry of the eleven carbonate formations within the 518 km[sup 2] study area were compiled. Data concerning 366 mapped sinkholes and over 9,000 additional karst features and their relations to the structural, lithological and spatial characteristics of the study area were collected and compiled into the database. Other factors contributing to karst development such as groundwater flow, soil and colluvium characteristics, and geographic distribution were considered. The data suggest that structure dominates lithology in the development of karst features within the study area. Structural features such as fractures, joints and folds, which create secondary porosity, are prerequisite for solution of the carbonate bedrock. Joint systems, fold axes, igneous intrusions, caves, springs and groundwater flow have a significant impact on the development of karst features. The presence of faults proved inconclusive. There are a greater number of karst features per unit area in areas of purer limestones (units with a lower percentage of acid insoluble residue). Lithological variations impact karst development only when structural features are present to provide secondary porosity that enhances chemical weathering. The distribution of karst features and the geologic factors governing their development and distribution should be taken into account when land-use decisions in karst terrains are made.

  9. Pedogenesis and Stability of Two Late Cenozoic Paleosols Developed on Alluvium in East-Central Pennsylvania

    NASA Astrophysics Data System (ADS)

    Cummins, K. T.; Peters, S.; Pazzaglia, F. J.

    2014-12-01

    The ridge and valley province of central Pennsylvania is named for the resistant ridges of sandstone and quartzite adjacent to more easily eroded valleys of limestone and shale. Colluvium and alluvium have accumulated against the base of the ridges, enabling pedogenic processes to develop and preserve a rich history of paleoenvironmental conditions in buried soils. Our group builds on the legacy of existing scholarship on these paleosols by deciphering the timing of the initiation of pedogenesis, and characterizing the most likely paleoenvironmental conditions of soil formation. In this work, we report on our first efforts to study two paleosols developed through alluvium deposited on the north-facing slope of South Mountain adjacent to the Cumberland and Lehigh Valleys. The first is a periglacial kame deposit near Emmaus, Pennsylvania that hosts a 4 meter thick soil, and the second deposit is a series of alluvial fan sequences near Mainsville, Pennsylvania that host a 10 meter thick soil. Common features observed in both these soils include a deeply rubified color and horizons with abundant iron and manganese oxides. In some localities, these iron oxides were abundant enough to be a source of iron ore during in the late 1800s. The relative proportion of amorphous iron oxides, as calculated from the ratio of oxalate extractable iron to dithionite extractable iron can be used to coarsely estimate an age for these soils. Ratios in the shallow modern brown-colored soils range from 0.21 to 0.35, and then evolve towards values of 0.088 to 0.143 in the rubified paleosols as the amorphous iron is converted to crystalline iron minerals. Evolution of iron crystallinity from comparable profiles reported in the literature takes between 1e5 and 1e6 years, suggesting a fairly long period of stability in these hillslopes.

  10. Sediment characterization, stocks and erodible relief quantification in alpine context using sloping local base level, from single watersheds to large-scale source-to-sink systems

    NASA Astrophysics Data System (ADS)

    Rudaz, Benjamin; Gavillet, Lauren; Jaboyedoff, Michel

    2014-05-01

    Erosion rates in alpine context since the last glacial maximum are classically calculated from accumulated sediments in glacial overdeepenings. Such erosion rates omit stored sediments in lateral valleys and secondary glacial troughs that have yet to get transported to the final sink. Their potential availability to the dominant mass wasting processes, such as landslides and debris-flows, is also important to assess, since sediment production and availability is a major driver of those hazardous phenomenon. In this study, a methodology to characterize sediment stocks and estimate their volume is applied to several watersheds, ranging from single torrential systems up to whole lateral valleys, and finally the complete source-to-sink system of the alpine Rhône river. First, areas occupied by colluvium, Holocene processes deposits and slope instabilities are mapped, using geological maps and HR-DEM hillshade. Each area is identified by its dominant formation process, and its situation in regard to glacially shaped valley geometry. For instance, glacial troughs are treated differently from valley walls and glacial cirques. The volume of sediments is given by subtracting a bedrock surface estimated with the SLBL methodology, with rock outcrops as fixed points, from the current topography. Where available, coring and geophysical data are used to constrain the geometry of the bedrock surface. Secondly, erodible relief is identified by considering the upper reaches of hydrologic networks as base levels. The volumes are constrained at the base with a slope angle derived from rock mechanics literature, thus changing with lithology, to emulate future potential slope movements towards the river network. The estimated stocks are then analyzed by process, age, and situation in the sediment cascade. The erodible relief allows localisation of future mass wasting potential, including the remobilization of existing stocks and future input from the still intact rock mass. The

  11. Terrestrial sedimentation and the carbon cycle: coupling weathering and erosion to carbon burial

    USGS Publications Warehouse

    Stallard, R.F.

    1998-01-01

    This paper examines the linkages between the carbon cycle and sedimentary processes on land. Available data suggest that sedimentation on land can bury vast quantities of organic carbon, roughly 1015 g C yr-1. To evaluate the relative roles of various classes of processes in the burial of carbon on land, terrestrial sedimentation was modeled as a series of 864 scenarios. Each scenario represents a unique choice of intensities for seven classes of processes and two different global wetland distributions. Comparison was made with presumed preagricultural conditions. The classes of processes were divided into two major component parts: clastic sedimentation of soil-derived carbon and organic sedimentation of autochthonous carbon. For clastic sedimentation, masses of sediment were considered for burial as reservoir sediment, lake sediment, and combined colluvium, alluvium, and aeolian deposits. When the ensemble of models is examined, the human-induced burial of 0.6-1.5.1015 g yr-1 of carbon on land is entirely plausible. This sink reaches its maximum strength between 30 ?? and 50??N. Paddy lands stand out as a type of land use that warrants future study, but the many faces of rice agriculture limit generalization. In an extreme scenario, paddy lands alone could be made to bury about 1.1015 g C yr-1. Arguing that terrestrial sedimentation processes could be much of the sink for the so called 'missing carbon' is reasonable. Such a hypothesis, however, requires major redesign of how the carbon cycle is modeled. Unlike ecosystem processes that are amenable to satellite monitoring and parallel modeling, many aspects of terrestrial sedimentation are hidden from space.

  12. Inventory of landslides in southern Illinois near the New Madrid Seismic Zone and the possible failure mechanism at three sites

    SciTech Connect

    Su, Wen June . Engineering Geology Section)

    1992-01-01

    A total of 221 landslides was inventoried along a 200-kilometer reach of the Ohio and the Mississippi Rivers from Olmsted to Chester, IL using Side-Looking Airborne Radar imagery, vertical, stereoscopic, black and white aerial photography at various scales, and low altitude, oblique color and color infrared photography. Features observed on aerial photographs were used to classify landslides into three types (rock/debris fall, block slide, and rotational/translational slide) at three levels of confidence: certain, probable, or possible. Some landslides combined two or more types at a single site. Only a few of the landslides showed evidence of repeated activity; most are ancient landforms. Most of the landslides were developed in the loess, alluvium, colluvium, and weak clay layers of the Chesterian Series or in the Porter's Creek Clay and McNairy Formation. Failure of three representative landslides was modeled under static (aseismic) and dynamic (seismic) situations using three different sliding mechanisms. Both the pseudo-static method and a simplified method of the Newmark displacement analysis were used to determine the stability of the slope under earthquake conditions. The three representative landslides selected for detailed slope stability analysis were the Ford Hill, Jones Ridge, and Olmsted landslides. The Ford Hill and Jones Ridge landslides have similar slope geometries. Their modes of failure were recognized as a translational block slide on a weak clay layer. The Olmsted landslide is a complex of several rotational slides of different ages and a mega block slide on weak clay layers. The stability analyses of these three landslides suggest that they would not have occurred under aseismic conditions. However, under earthquake loadings similar to those generated by the 1811-12 earthquakes, most of the slopes could have experienced large displacements leading to landslide initiation.

  13. Relations between rainfall amount, soil moisture and landslides in Hamilton County, Ohio, measured by strain survey and tensiometers

    SciTech Connect

    Bechtel, B.; Mayer, L. . Dept. of Geology)

    1993-03-01

    The movement of water through fill material and natural colluvium in a cut slope is being monitored at two sites with past landslide activity adjacent to I-275 in Hamilton County, Ohio. Quadrilaterals and an array of wooden stakes were placed immediately adjacent to the slide area to monitor movement of the slope at Site 1. To correlate any movement with soil moisture levels, rain gauges were installed. Changes in line-length measurements over a 3-month period are < 14 mm, and most differences average about 4 mm. Since measurement errors of up to 5--6 mm can be expected using a steel tape, more measurements over time will be needed to determine if significant displacement is occurring. Tensiometers were placed at 12 and 36 inches depth in the soil from mid-September through early November 1992, in order to measure matric suction. The 36 inch tensiometer indicated that the soil remained saturated at that depth. The 12 inch tensiometer measured 8 centibars, which occurred following a week of rain-free weather. Gravimetric measurements of soil samples show that surface soil moisture ranges from 14--39% immediately following a storm to 7--29% following at least 10 days of dry weather. At Site 2, quadrilaterals were set up in mid-August 1992; resurveys of the quadrilaterals shows very little, if any, movement. Movement of 38 mm occurred in one quadrilateral; movement in other quadrilaterals averaged close to 5 mm. The slide is not steadily moving, and may be following a pattern, where slides in Hamilton County were more likely to move in late winter or early spring.

  14. The landslide response of alpine basins to post-Little Ice Age glacial thinning and retreat in southwestern British Columbia

    NASA Astrophysics Data System (ADS)

    Holm, Kris; Bovis, Michael; Jakob, Matthias

    2004-02-01

    The role of post-Little Ice Age (LIA) Neoglacial retreat on landslide activity is investigated in 19 alpine basins along the upper Lillooet River Valley, British Columbia. We examine how Neoglacial scouring and glacial recession have modified hillslope form and slope stability, and construct a decision-making flowchart to identify landslide hazards associated with glacial retreat. This work is based on field mapping, GIS analysis, statistical associations between landslides and terrain attributes, and a comparison between Neoglaciated and non-Neoglaciated terrain within each basin. The bedrock landslide response to glacial retreat varies appreciably according to lithology and the extent of glacial scour below the LIA trimline. Valleys carved in weak Quaternary volcanics show significant erosional oversteepening and contain deep-seated slope movement features, active rock fall, rock slides, and rock avalanches near glacial trimlines. Basins in stronger granitic rock rarely show increased bedrock instability resulting from post-LIA retreat, except for shallow-seated rock slides along some trimlines and failures on previously unstable slopes. In surficial materials, landslides associated with post-LIA retreat originate in till or colluvium, as debris slides or debris avalanches, and are concentrated along lateral moraines or glacial trimlines. Significant spatial association was also observed between recent catastrophic failures, gravitational slope deformation, and slopes that were oversteepened then debuttressed by glacial erosion. Eight out of nine catastrophic rock slope failures occurred just above glacial trimlines and all occurred in areas with a previous history of deep-seated gravitational slope movement, implying that this type of deformation is a precursor to catastrophic detachment.

  15. Hypothesis on the cause of extinction of the South American mastodonts

    NASA Astrophysics Data System (ADS)

    Ficcarelli, G.; Azzaroli, A.; Bertini, A.; Coltorti, M.; Mazza, P.; Mezzabotta, C.; Espinosa, M. Moreno; Rook, L.; Torre, D.

    1997-01-01

    Paleontological, geomorphological and sedimentological investigations on the Cangahua Formation in the Interandean depression of Northern and Central Ecuador have provided information on the evolution of the Andean paleoenvironment during the Late Pleistocene. Pyroclastic and windblown sediments were deposited during cold and dry phases of the last glaciation, interrupted many times by the development of forest-steppe and steppe paleosoils during interstadials. An erosional phase which closed the Cangahua sedimentation was followed by the deposition of colluvial sediments, characterized by a high number of minor pedogenetic episodes. The colluviums are confidently referable to the Holocene. The upper part of the Cangahua Formation is rich in mammal fossils and is probably referable to the Last Glacial Maximum. The fossiliferous sequences suggest that mastodonts disappeared before mylodonts and equids. We hypothesize that the increased cold and aridity of the Last Glacial Maximum, which deeply affected the Cordillera, caused the extinction of most of the megafauna and the mastodonts seem to have been the most sensitive to the environmental degradation. The final history of South American mastodonts, represented by Haplomastodon and Stegomastodon, spans the latest Pleistocene and probably the earliest Holocene. Haplomastodon was dispersed in the highlands within the tropical belt and Stegomastodon in plains of the southernmost part of Brazil, in Paraguay, Uraguay, Argentine, central and northern Chile. Both Haplomastodon and Stegomastodon suffered the same negative effects of the Last Glacial Maximum when their habitats underwent intense desertifications under dry and cold conditions. They disappeared in a mosaic way in the course of the latest Pleistocene, the last representatives probably surviving in favorable restricted areas where however the considerably increased selective pressure was in the long run devastating. In our opinion the human impact was not a

  16. An overview of recent large landslides in northern British Columbia, Canada.

    NASA Astrophysics Data System (ADS)

    Geertsema, M.; Clague, J. J.; Schwab, J. W.; Evans, S. G.

    2003-04-01

    Within the last few decades, at least twenty-four, long-runout rapid landslides, each in excess of 1 million m^3, have occurred in northern British Columbia. Fifteen of the landslides have happened within the last 10 years alone. The landslides include low- gradient rapid flowslides in cohesive sediments, rock avalanches, and complex rock slide - flowslides and rock slide - debris flows. The flowslides have occurred in a variety of sediments, including glaciolacustrine deposits, clay-rich tills, and clay-rich colluvium. The rock failures have involved weak shales overlain by sandstone, and volcanic rocks. We are cataloguing these landslides in a compendium of natural hazards for northern British Columbia. Pre- and post-landslide aerial photographs have been obtained for fifteen of the landslides, and detailed topographic maps have been generated from these photographs. In addition we have determined soil properties, including Atterberg tests for six of the flowslides. The rock avalanches occur in three types of settings: (1) dip slopes in sedimentary rocks in the Rocky Mountain foothills; (2) escarpments of flat-lying sedimentary rocks where spreading is happening; and (3) unstable cirque walls. Infrastructure and resources at risk from these types of large landslides include settlements, forest roads and highways, pipelines, fish habitat, forests, and farmland. One rock avalanche terminated within 2 km of the Alaska Highway, and a rock slide came within a few kilometres of a farm house. Most of these landslides have impounded streams or rivers, thus the hazard associated with upstream inundation and catastrophic dam failure must also be considered. There appears to be an increase in the frequency of large landslides in northern British Columbia. Is this due to climate change? Can we expect this trend to continue?

  17. Geologic map of the Eagle Quadrangle, Eagle County, Colorado

    USGS Publications Warehouse

    Lidke, D.J.

    2002-01-01

    basaltic rocks, by dissolution or flowage of the evaporite in the subsurface. Quaternary and late Tertiary(?) surficial deposits in the map area consist mainly of Quaternary alluvium and colluvium, late and middle Pleistocene terrace gravels of the Eagle River, Miocene(?) gravel remnants of the ancestral Eagle River and its tributaries, and Pleistocene to recent mass movement deposits that include landslides and debris flows. Potential geologic hazards in the map area include landslides, debris flows, rockfalls, local flooding, ground subsidence, and expansive and corrosive soils.

  18. Multi-proxy record of land use change derived from colluvial soils of the western Pyrenees Mountains, France

    NASA Astrophysics Data System (ADS)

    Leigh, David S.; Gragson, Theodore L.; Coughlan, Michael R.

    2016-04-01

    Archaeological evidence and paleoenvironmental proxies from wetland bogs (e.g. charcoal, pastoral pollen, fungal spores of sheep dung) clearly outline the regional chronology of Holocene pastoral activity in the Pyrenees. We increase the spatial and temporal resolution of this chronology through a place-based, millennial-scale investigation of land use activities within individual fields in the commune of Larrau, Pyrénées Atlantiques, France. We have identified several stratigraphic records of slopewash colluvium that span the entire Holocene that occur at the outlets of zero-order watersheds, each draining several hectares. To examine forest-to-pasture transformation, two to three meter long auger holes were sampled in contiguous five centimeter intervals. These samples were analyzed for charcoal content, radiocarbon age, magnetic susceptibility, particle size, organic matter, and n-alkane concentrations. Results indicate that intentional burning and clearing were initiated by the Late Neolithic (ca. 5000-6000 cal. BP), but more intense burning, clearing, and pronounced soil erosion occurred later during the Bronze Age and Iron Age. Charcoal concentrations and low frequency magnetic susceptibility provide evidence of initial burning and subsequent variation in the intensity of fire use. Radiocarbon chronologies exhibit order-of-magnitude spikes in sedimentation rates (1-10 mm/yr) during the Bronze Age and Iron Age that are asynchronous between sites. Asynchronous records suggest anthropic, rather than climatic, drivers and imply that land use varied in intensity across the landscape, unlike the uniform intensity of pasture use typical of the modern landscape. Sedimentation rates, and presumably erosion rates, returned to very near pre-pastoral background levels (<1mm/yr) during the last 1500 years. A pristine-degraded-recovery cycle is thus indicated for the span of the Holocene illustrating that not all pastures around the world persist with stereotypical

  19. Geology and ground-water hydrology of the Angostura irrigation project, South Dakota, with a section on the mineral quality of the waters

    USGS Publications Warehouse

    Littleton, Robert T.; Swenson, Herbert A.

    1949-01-01

    The lands to be irrigated from water stored in the Angostura Reservoir are situated on the lover of two terraces along the southeast side of the Cheyenne River in northeastern Fall River County and on the terrace known as Harrison Plat in southeastern Custer County, S. Dak. The terrace deposits are composed of relatively permeable sands and gravels that rest on a shale bedrock platform. The terrace surfaces are mantled in part by slope wash derived from higher shale slopes and by wind-blown sand. Ground water occurs under water-table conditions in the river alluvium and in terraces above the river. Although the zone of saturation in the terrace deposits is 6enerally thin, it is essentially continuous in the area southeast of the river, and the water issues as springs in the terrace faces along the inner valley of the river and along the valleys of tributary streams cuttin6 back into the terraces. A zone of saturation is present only in part of the Harrison Plat area, and it extends to the terrace face only along Cottonwood Creek. Wells in the unconsolidated mantle rock supply water for domestic and stock purposes, but yields are small. Abundant supplies of artesian water are available at depths ranging up to 3,000 feet but are not now utilized except at the extreme western end of the area where the bedrock aquifer is close below the surface. The effect of applying irrigation water on the terrace lands will depend on the character of the underlying material and on the measures taken to forestall waterlogging and other undesirable effects. Terrace areas that are mantled by slope wash will be especially susceptible to waterlogging, as will valley-bottom areas mantled by colluvium that are adjacent to irrigated terracea. Periodic measurements of water levels in observation wells will give warning of potential waterlogging in time to permit taking preventive measures. Analyses of samples of both ground water and surface water indicate a high mineral content. In general

  20. Evolution of the Holocene uplifted terraces along the Chihshang Fault, Eastern Taiwan: Interactions between tectonic vertical movement and fluvial sedimentation

    NASA Astrophysics Data System (ADS)

    Chang, Q.; Lee, J. C.; Wang, S. L.; Chen, R. F.; Chen, Y. G.

    2014-12-01

    The Chihshang terrace group is located on the hanging wall of the Chihshang Fault, one of the most active segments of the Longitudinal Valley Fault which represents the onland plate-suture fault between the Eurasian and Philippine Sea plates in eastern Taiwan. Being different from common river terraces usually developed on two sides of river channel, the Chihshang terrace group is located on the toe area of the large alluvial fan of east-flowing Xinwulyu River, which derived from the Central Range and crosses the 5-7-km-wide Longitudinal Valley to reach the Coastal Rang and has been cut through by the west-thrusting Chihshang Fault. The 5-m DEM morphology analyses results show the Chihshang terrace group can be divided into ten levels of various height differences. The spatial distribution of terraces is uneven: higher levels (T5 to T10, >34 m high) and lower levels (T1 and T2, <23 m high) distribute on the northern part of alluvial fan, medium levels (T3 and T4, around 25-32 m high) on the middle part, and no terraces can be found on the southern part. Field investigations and the observations from six trenches on terraces surface show that the compositing units of terraces from top to bottom are: the Coastal Range colluviums deposits from local hills or tributaries, the Central Range deposits from Xinwulyu River channel deposits, and the bedrock. Based on these results it appears that the Chihshang terrace group was formed under influence of the continuous thrusting movement of the Chihshang Fault and the episodic lateral erosion and sedimentation of Xinwulyu River on to the hanging wall area. The uneven geographic distribution of terraces reveals the channel migration history of the Xinwulyu River. 14C dating result of the Coastal Range deposits in a high level terrace (T7, around 30 m high from the footwall) is 5,750-6,880 cal yr B.P. Combine with previous reported data (290-490 cal yr B.P. of lowest level terrace) it reveals that the Xinwulyu River flowed to

  1. Late Quaternary landscape evolution in the Great Karoo, South Africa: Processes and drivers.

    NASA Astrophysics Data System (ADS)

    Oldknow, Chris; Hooke, Janet; Lang, Andreas

    2016-04-01

    The Great Karoo spans the north-central part of South Africa at a major climatic boundary. The characteristics, sequences, spatial patterns and drivers of river response to Late Quaternary climate changes in this region remain unclear due to the fragmentary alluvial/colluvial stratigraphic record and the lack of dated palaeoclimatic archives. Dendritic gully networks incised into deep deposits (up to 6 m) of colluvium and alluvium in the upper Sundays River catchment expose a legacy of "cut and fill" features. In 1st order tributaries, these are predominantly discontinuous palaeochannels and flood-outs with localised palaeosols, whereas in 2nd & 3rd order tributaries there are: 1) incised palaeo-geomorphic surfaces, 2) semi-continuous inset terrace sequences, 3) buried palaeo-gully topography. Using a combination of field mapping, logging of sediment outcrops, soil micromorphological and grain size analysis, mineral magnetic measurements and radiometric dating (OSL & 14C), we derive a stratigraphic evolution model which demonstrates a) the number of phases of incision, aggradation and pedogenesis, b) the spatial and temporal extent of each phase and c) the drivers of alluviation and associated feedbacks. Our reconstruction of regional valley alluviation indicates four distinct terrace units of contrasting depositional age. The base of the succession reflects slow aggradation under periglacial conditions associated with the Last Glacial Maximum. Subsequent channel entrenchment, causing terrace abandonment (T1) occurred in the deglacial period when vegetation and rainfall were in anti-phase. Re-instatement of connectivity with deep upland colluvial stores resulted in the injection of a pulse of sediment to valley floors, triggering compartmentalised backfilling (aggradation of T2) which propagated upstream as far as the second order drainage lines. This backfilling restructured the local hydrology, which, in concert with enhanced summer-rainfall, contributed to a

  2. Structural and Geomorphic Controls on Dryland Salinity and Regolith Distribution in the Critical Zone, North-east Tasmania, Australia.

    NASA Astrophysics Data System (ADS)

    Sweeney, M. E.; Moore, C. L.

    2015-12-01

    Salinity occurs in the drier and flatter Australian landscapes because there is insufficient rain to flush salts from critical zone. Changes in land use due to agriculture and urbanisation can accelerate salinity effects, leading to soil and water degradation and threatening infrastructure and ecosystems. The dominant lithology in the salt affected regions of North-east Tasmania is dolerite. The geochemistry of dolerite regolith has been examined in order to understand the association between salinity and weathered dolerite. The electrical conductivity of 1:5 soil-waters is higher in the more weathered material (maximum 4.9 dS/m). This confirms field observations that highly weathered dolerite can serve as a significant store for salt in the landscape. However, the clay content and salinity varies, depending on the local geomorphic context. Dolerite weathering on well-drained slopes has favoured the formation of 1:1 kaolinite clays, and sometimes bauxite formation. Kaolinite-bearing regolith can store salt via matrix diffusion processes. However, there are fault-bounded pockets of colluvium and highly-weathered in situmaterial, where the supply of cations has not been diminished and 2:1 montmorillonite clays dominate. These regions have the capacity to store large volumes of salts. The geomorphology also affects the volume of rain and flux of salt from windblown dust and oceanic aerosols. The chemistry of rainwater from an array of bulk deposition collectors was studied from Spring 2013 to Winter 2014. The average salt flux was 79± 10 kg/ha/yr in the study region, ranging from 170± 12 kg/ha/yr in the north to 42 ± 6 kg/ha/yr inland. To assist in understanding why salt is found in certain parts of the landscape but not in others, it is essential to model how water moves through the critical zone and geological structures. By exploring the complex interactions of geomorphology and other biophysical parameters the study area has been divided into Hydrogeological

  3. Geologic Map of the Shenandoah National Park Region, Virginia

    USGS Publications Warehouse

    Southworth, Scott; Aleinikoff, John N.; Bailey, Christopher M.; Burton, William C.; Crider, E.A.; Hackley, Paul C.; Smoot, Joseph P.; Tollo, Richard P.

    2009-01-01

    ridges from 800 to 400 meters in altitude. The Page Valley is underlain by Cambrian and Ordovician carbonate rocks. Siliciclastic rocks are mostly west of the South Fork of the Shenandoah River and underlie Massanutten Mountain. Surficial deposits in the highlands include colluvium and debris fans. The lowlands have broad alluvial fans, alluvial plains, and fluvial terraces. Ridges underlain by siliciclastic rocks have abundant boulder fields. Numerous sinkholes and caves are due to the dissolution of the carbonate bedrock.

  4. Applying Terzaghi's method of slope characterization to the recognition of Holocene land slippage

    NASA Astrophysics Data System (ADS)

    Rogers, J. David; Chung, Jae-won

    2016-07-01

    During site investigations, engineering geologists are expected to recognize landslides, both active and dormant. Those without substantial experience evaluating the evolution of geomorphic features associated with localized mass wasting often mischaracterize site conditions. Karl Terzaghi suggested seven steps in characterizing natural hillslopes, including (1) a literature review, (2) site reconnaissance, (3) a program of subsurface exploration, (4) preparation of sketches and diagrams illustrating the essential features, (5) preparation of a preliminary geology report, (6) observation and mapping of geologic structures exposed during excavation for construction, and (7) development of contingency plans for anticipated variations in old landslide features. Based on our interpretation of Terzaghi's original principles, we review some of the most common interpretive problems with nomenclature of landslide features, describe common mistakes in characterizing old landslides, and present technical approaches that often aid in the recognition of old landslide features. A wide variance in geological terms exists for describing landslides, and various terms have been applied to the same features by workers in different areas, which often leads to confusion. Some of these terms include nomenclature such as slip surfaces, alluvial fans, colluvium, and slope creep. Active surficial landslides are relatively easy to recognize when they are well exposed. Although these features tend to become obscured with time, anomalous, hummocky topography often provide key recognition features of a slope's geomorphic evolution. Deeper-seated bedrock landslides can be more difficult to recognize because their features become increasingly mollified with time. These features can often be identified by anomalous geomorphic features, such as isolated saddles or anomalous/discontinuous benches. These features are some of the best locations to excavate borings or exploratory trenches. Well

  5. Geology of the Western Part of Los Alamos National Laboratory (TA-3 to TA-16), Rio Grande Rift, New Mexico

    SciTech Connect

    C.J.Lewis; A.Lavine; S.L.Reneau; J.N.Gardner; R.Channell; C.W.Criswell

    2002-12-01

    We present data that elucidate the stratigraphy, geomorphology, and structure in the western part of Los Alamos National Laboratory between Technical Areas 3 and 16 (TA-3 and TA-16). Data include those gathered by geologic mapping of surficial, post-Bandelier Tuff strata, conventional and high-precision geologic mapping and geochemical analysis of cooling units within the Bandelier Tuff, logging of boreholes and a gas pipeline trench, and structural analysis using profiles, cross sections, structure contour maps, and stereographic projections. This work contributes to an improved understanding of the paleoseismic and geomorphic history of the area, which will aid in future seismic hazard evaluations and other investigations. The study area lies at the base of the main, 120-m (400-ft) high escarpment formed by the Pajarito fault, an active fault of the Rio Grande rift that bounds Los Alamos National Laboratory on the west. Subsidiary fracturing, faulting, and folding associated with the Pajarito fault zone extends at least 1,500 m (5,000 ft) to the east of the main Pajarito fault escarpment. Stratigraphic units in the study area include upper units of the Tshirege Member of the early Pleistocene Bandelier Tuff, early Pleistocene alluvial fan deposits that predate incision of canyons on this part of the Pajarito Plateau, and younger Pleistocene and Holocene alluvium and colluvium that postdate drainage incision. We discriminate four sets of structures in the area between TA-3 and TA-16: (a) north-striking faults and folds that mark the main zone of deformation, including a graben in the central part of the study area; (b) north-northwest-striking fractures and rare faults that bound the eastern side of the principal zone of deformation and may be the surface expression of deep-seated faulting; (c) rare northeast-striking structures near the northern limit of the area associated with the southern end of the Rendija Canyon fault; and (d) several small east

  6. Alpine debris flows triggered by a 28 July 1999 thunderstorm in the central Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Godt, Jonathan W.; Coe, Jeffrey A.

    2007-02-01

    On 28 July 1999, about 480 alpine debris flows were triggered by an afternoon thunderstorm along the Continental Divide in Clear Creek and Summit counties in the central Front Range of Colorado. The thunderstorm produced about 43 mm of rain in 4 h, 35 mm of which fell in the first 2 h. Several debris flows triggered by the storm impacted Interstate Highway 70, U.S. Highway 6, and the Arapahoe Basin ski area. We mapped the debris flows from color aerial photography and inspected many of them in the field. Three processes initiated debris flows. The first process initiated 11% of the debris flows and involved the mobilization of shallow landslides in thick, often well vegetated, colluvium. The second process, which was responsible for 79% of the flows, was the transport of material eroded from steep unvegetated hillslopes via a system of coalescing rills. The third, which has been termed the "firehose effect," initiated 10% of the debris flows and occurred where overland flow became concentrated in steep bedrock channels and scoured debris from talus deposits and the heads of debris fans. These three processes initiated high on steep hillsides (> 30°) in catchments with small contributing areas (< 8000 m 2), however, shallow landslides occurred on slopes that were significantly less steep than either overland flow process. Based on field observations and examination of soils mapping of the northern part of the study area, we identified a relation between the degree of soil development and the process type that generated debris flows. In general, areas with greater soil development were less likely to generate runoff and therefore less likely to generate debris flows by the firehose effect or by rilling. The character of the surficial cover and the spatially variable hydrologic response to intense rainfall, rather than a threshold of contributing area and topographic slope, appears to control the initiation process in the high alpine of the Front Range. Because

  7. Using of high resolution morphometric thalweg analyses of dry valleys under woodland to assess land use impact and soil erosion in the late Holocene

    NASA Astrophysics Data System (ADS)

    Dotterweich, M.; Bub, S.

    2012-04-01

    During the Holocene, geomorphic processes have been greatly hindered by the natural vegetation cover in central Europe. On the majority of land surfaces, processes of soil development dominate, hence producing stable geomorphodynamic systems. The removal of trees for timber, the construction of pathways or clear-cuts to enable agriculture creates temporarily or permanently bare soil surfaces which are highly vulnerable to soil erosion. During rainfall events run-off produces erosional forms like rills and gullies on slopes and along the thalweg. The eroded material accumulates as colluvium on the footslopes and as hillslope terraces, and at the outlet of gullies or dry valleys as colluvial fans. Hence, these forms are a topographical legacy of land use and intensive rainfall events in the past. In central Europe, many of these forms are well preserved under woodland. LiDAR data provide an excellent basis to identify, survey, and quantify their spatial distribution by geo-statistical methods. This paper presents automatic morphometric analyses of cross-sections along dry valleys using ArcGIS®. The idea behind this approach is that in cross-section the deposition of sediments leads to a flattening of small valley bottoms from a v-shaped to a u-shaped form while linear erosion deepens the thalweg in a morphometric form different to the natural situation. The study area has a size of about 100 km2 and is located in the central part of the Palatinate forest of the German-Lorraine Triassic escarpment. The low-mountain range landscape is characterized by steep slopes with an alternation of scarps with exposed bedrock of the Bunter sandstone. In the southern part, agriculture and clear-cuts for timber use were dominant between the 18th to mid-19th century while in the remote northern part the harvest of trees occurred only occasionally. After the automatic generation of cross-sections in a GIS, each profile was analysed and compared to typical natural or erosional forms

  8. Rare Earth Elements reveal past earthquakes on limestone normal faults

    NASA Astrophysics Data System (ADS)

    Manighetti, I.; Boucher, E.; Chauvel, C.; Schlagenhauf, A.; Benedetti, L.

    2009-12-01

    In 2008, we suggested that the chemical composition of the rocks which form well preserved, seismically exhumed fault scarps might record past major earthquakes (Carcaillet et al., 2008) because those scarp surfaces consist of a vertical succession of zones that have been exposed at different times by the repeating earthquakes, thus weathered over different time spans. In this pioneer study, we validated this hypothesis using the changes in chemical compositions (major and trace elements) of 15 carbonate rock samples collected from the base to the top of the seismically exhumed, 10 m-high Magnola normal fault scarp (Abruzzes, Central Italy). However, the number of available samples was insufficient to fully assess the validity of the model. Here we present trace element data on 27 additional samples collected systematically every 25 cm along the Magnola scarp, as well as on 7 scarp samples buried below the colluvium hence representing the first 4 meters of the scarp before exhumation. The scarp rocks buried in the first meter of the ground appear significantly enriched in Rare Earth elements (REE): they contain 60% more REE than the rocks located either deeper in the ground or immediately above the ground level. This concentration peak most probably results from enrichment of the scarp rocks by interaction with the impurity-doped, acidic, upper soil. Above the ground surface and along the scarp, most element concentrations (70%) decrease up-dip, generally by more than 50%; we attribute this trend to leaching and dissolution-recrystallization of purer calcite through time. The top of the scarp having been exposed for a longer period of time, its surface lost more of the trace elements contained in the rocks. However, the upward decrease in REE contents is not linear and 4 REE concentration peaks can be recognized along the exposed scarp. The position of these 4 peaks coincide with the zones identified by Schlagenhauf et al. (2009) and Palumbo et al. (2004) as

  9. Late Quaternary mass-wasting records and formation of alluvial terraces in the actively uplifting Lao-nong catchment, southwestern Taiwan

    NASA Astrophysics Data System (ADS)

    Tsui, H. K.; Hsieh, M. L.; Li, W. L.; Hsiao, Y. T.

    2014-12-01

    , and frequency of the events. Our field observation suggests that at least some of the large Holocene tributary-fan terraces were sourced from pre-Holocene colluviums.

  10. Geologic Map of the Clark Peak Quadrangle, Jackson and Larimer Counties, Colorado

    USGS Publications Warehouse

    Kellogg, Karl S.; Ruleman, Chester A.; Shroba, Ralph R.; Braddock, William A.

    2008-01-01

    deposits (mostly of Pinedale age), rock glaciers, block-slope deposits, landslide deposits, talus deposits, fan deposits, colluvium, and alluvium comprise the surficial deposits of the map area.

  11. Cold Climate Related Structural Sinks Accommodate Unusual Soil Constituents, Pinelands National Reserve, New Jersey, USA

    NASA Astrophysics Data System (ADS)

    Demitroff, M.; Lecompte, M. A.; Rock, B. N.

    2009-12-01

    Firestone and others proposed an extraterrestrial (ET) impact upon the Laurentide Ice Sheet 12,900 years ago led to abrupt climate change and left behind a distinct suite of microscopic soil markers. If so, then soil memory of such an extreme event should be apparent across a wide swath of ice-marginal North America. New Jersey’s Pine Barrens has a remarkably well-preserved record of Late Pleistocene soil structures that provide snapshots of rigorous climatic episodes, the youngest of which are potential reservoirs for ET markers. Cryogenic macrostructures are fissures related to episodic temperature and moisture extremes providing excellent chronostratigraphic control - unlike soil horizons that are often affected by denudation and pedogenic modification. Three distinct ground structures were sampled for evidence of infill-related ET markers: 1) two ground (soil) wedges (early Holocene?); 2) a younger sand-wedge cast (late-Wisconsinan?); and 3) an older sand-wedge cast (early-Wisconsinan?). Attendant host sediment and capping colluvium coversand samples were also collected for evidence of ET markers to detect potential source sinks. Our pedocomplex contained elements ranging from Miocene Cohansey Formation basement sands to early-Holocene fluvioeolian coversands. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive x-ray analysis (EDX) are being used to characterize soil constituents of interest. Carbon and luminescence dating are underway to provide geomorphic events timing associated with specific soil constituent trap formation. Fly ash collected from a coal-fired electrical plant 13-km distant was also examined. Several soil constituents atypical to the local petrology as currently understood were found. Infill from two ground (soil) wedges contained ~100,000 to ~500,000 magnetic spherules/kg, 25 to 50 translucent amber-colored spherules/kg, 250 to 500 carbon spherules/kg, charcoal, and pieces of glass-like carbon

  12. Structural analysis of the Cordillera Blanca detachment: Geometry, kinematics and fault rocks

    NASA Astrophysics Data System (ADS)

    Shaw, C. A.; Jessup, M. J.; Hughes, C. A.; Newell, D. L.

    2015-12-01

    The Cordillera Banca Detachment (CBD) in the north-central Peruvian Andes is recognized as a rare example of active extension parallel to the direction of shortening within a convergent orogenic setting. Despite longstanding interest in the geodynamic significance of the CBD relatively little work has been done to characterize the basic geometry, kinematics and evolution of the detachment or the petrology and distribution of brittle and ductile tectonites within the fault zone. This contribution presents preliminary results of a basic structural analysis of the CBD based on field observations, laboratory results, and GIS analysis. Basic structural observations of fault geometry and kinematics are needed to constrain the regional geodynamic role of the CBD. The NNW topographic trace of the CBD is defined by faceted ridges up to 2000 m in height. The lower slopes of the facets are locally cut by steep fault scarps that offset quaternary glacial moraines, debris fans and colluvium. The shear zone comprises both brittle and ductile tectonites including mylonite series rocks, pseudotachylyte, and breccia - often highly silicified. Highly polished mirrored surfaces are observed locally. Deformation mechanisms show a consistent progression from plastic in structurally lower positions to brittle in structurally higher positions. Evidence for overprinting deformation mechanisms is preserved in many samples. The shear zone ranges up to about 200 m thick. The average orientation of mylonitic foliation and fault slip surfaces (strike/dip = 140/30) and lineations/slickenlines (plunge-trend = 35-235) is quite consistent along the ~200 km detachment, but some systematic variation along strike may be related to concave fault segments or corrugations. Slip indicators are nearly down-dip with a minor left-lateral or right-lateral component in some locations. Offsets in marker horizons constrain total offset between about 4500 m near the central section of the fault to near zero

  13. Geologic map of the Kings Mountain and Grover quadrangles, Cleveland and Gaston Counties, North Carolina, and Cherokee and York Counties, South Carolina

    USGS Publications Warehouse

    Horton, J. Wright

    2006-01-01

    show a westward decrease from upper amphibolite facies (sillimanite zone) near the High Shoals Granite on the east side of the map to greenschist (epidote-amphibolite) facies in the south-central part of the area near the Kings Mountain shear zone. Amphibolite-facies mineral assemblages in the Inner Piedmont terrane increase in grade from the kyanite zone near the Kings Mountain shear zone to the sillimanite zone in the northwest part of the map. Surficial deposits include alluvium in the stream valleys and colluvium along ridges and steep slopes. These quadrangles are unusual in their richness and variety of mineral deposits, which include spodumene (lithium), cassiterite (tin), mica, feldspar, silica, clay, marble, kyanite and sillimanite, barite, manganese, sand and gravel, gold, pyrite, and iron. (Abstract from pamphlet.)

  14. Geologic Map of the Kings Mountain and Grover Quadrangles, Cleveland and Gaston Counties, North Carolina, and Cherokee and York Counties, South Carolina

    USGS Publications Warehouse

    Horton, J. Wright

    2008-01-01

    sequence show a westward decrease from upper amphibolite facies (sillimanite zone) near the High Shoals Granite in the eastern side of the map area to upper greenschist (epidote-amphibolite) facies in the south-central part of the area near the Kings Mountain shear zone. Amphibolite-facies mineral assemblages in the Inner Piedmont terrane increase in grade from the kyanite zone near the Kings Mountain shear zone to the sillimanite zone in the northwestern part of the map area. Surficial deposits include alluvium in the stream valleys and colluvium along ridges and steep slopes. These quadrangles are unusual in the richness and variety of the mineral deposits that they contain, which include spodumene (lithium), cassiterite (tin), mica, feldspar, silica, clay, marble, kyanite and sillimanite, barite, manganese, sand and gravel, gold, pyrite, and iron.

  15. Violent Explosive Eruptions in the Ararat Valley, Armenia and Associated Volcanic Hazards

    NASA Astrophysics Data System (ADS)

    Meliksetian, Khachatur; Savov, Ivan; Connor, Charles; Gevorgyan, Hripsime; Connor, Laura; Navasardyan, Gevorg; Manucharyan, Davit; Jrbashyan, Ruben; Ghukasyan, Yura

    2016-04-01

    The Anatolian-Armenian-Iranian volcanically active orogenic plateau is located in the collision zone between the Arabian and Eurasian plates. The majority of regional geodynamic and petrologic models of collision-related magmatism use the model proposed by Keskin (2003), where volcanism is driven by Neo-Tethyan slab break-off, however an updated model by Neill et al. (2015) and Skolbeltsyn et al.(2014) comprise break-off of two slabs. One of the significant (and understudied) features of the regionally extensive collision zone volcanism is the diversity of eruption styles and also the presence of large number of highly explosive (Plinian) eruptions with VEI≥5 during the Middle-Upper Pleistocene. Geological records of the Ararat depression include several generations of thick low aspect ratio Quaternary ignimbrites erupted from Aragats volcano, as well as up to 3 m thick ash and pumice fall deposit from the Holocene-historically active Ararat volcano. The Ararat tephra fall deposit is studied at 12 newly discovered outcrops covering an area ˜1000 km2. It is noteworthy, that the Ararat tephra deposits are loose and unwelded and observed only in cross-sections in small depressions or in areas where they were rapidly covered by younger, colluvium deposits, presumably of Holocene age. Therefore, the spatial extent of the explosive deposits of Ararat is much bigger but not well preserved due to rapid erosion. Whole rock elemental, isotope (Sr, Nd) and mineral chemistry data demonstrate significant difference in the magma sources of the large Aragats and Ararat stratovolcanoes. Lavas and pyroclastic products of Aragats are high K calc-alkaline, and nearly always deprived from H2O rich phases such as amphibole. In contrasts lavas and pyroclastic products from Ararat are medium K calc-alkaline and volatile-rich (>4.6 wt% H2O and amphibole bearing) magmas. Here we shall attempt to reveal possible geochemical triggers of explosive eruptions in these volcanoes and assess

  16. Trapping carbon in small ponds and wetlands

    NASA Astrophysics Data System (ADS)

    Quinton, J. N.; Ockenden, M. C.; Deasy, C.; Favaretto, N.

    2012-04-01

    There is no doubt that carbon (C) is on the move. Recent estimates have suggested that the global sediment flux in agricultural landscapes due to water and tillage erosion is 35±10 Pg C y-1. Some of this C is oxidised and lost to the atmosphere, other material may be deposited and burried in colluvium and some may be delivered through both surface and subsurface flow paths to surface waters. In many agricultural landscapes these surface waters may take the form of small ponds and wetlands (field wetlands). In this paper we explore the potential of field wetlands to trap particulate C and influence the fate of dissolved organic carbon within the context of a small agricultural catchments in England. Since 2008 the mitigation options for phosphorus and sediment project (MOPS) has established ten monitored field wetlands across three catchments in the UK at Crake Trees, Cumbria (silt soils, rainfall 1500 mm y-1), Whinton Hill Cumbria (sandy soils, rainfall 1200 mm y-1), Newton Rigg, Cumbria (Silt soils, rainfall c1200 mm y-1) and Loddington, Leicestershire (Clay soils, rainfall 650 mm y-1). Although originally designed to capture sediment and phosphorus, their potential for influencing catchment scale C dynamics is becoming apparent. The C contents of sediments from the three catchments are typically in the range of 1.8 - 3.0% at Crake Trees Catchment, 2.5 to 9% at Whinton Hill and 2.0 to 3.1 % at Crake Trees. At the high rainfall sites the wetlands trap upwards of 20 t y-1 of sediment equating to several hundred kilograms of C. There is also some evidence that the ponds and wetlands may influence DOC, with DOC concentrations falling from approximately 35 mg l-1 to 15 mg l-1 at the Whinton Hill site as water passes through a series of field wetlands. In this paper we will present data from the last two years of monitoring and consider the wider implications for C sequestration by ponds and wetlands in agricultural landscapes.

  17. Erosion of an ancient mountain range, the Great Smoky Mountains, North Carolina and Tennessee

    USGS Publications Warehouse

    Matmon, A.; Bierman, P.R.; Larsen, J.; Southworth, S.; Pavich, M.; Finkel, R.; Caffee, M.

    2003-01-01

    Analysis of 10Be and 26Al in bedrock (n=10), colluvium (n=5 including grain size splits), and alluvial sediments (n=59 including grain size splits), coupled with field observations and GIS analysis, suggest that erosion rates in the Great Smoky Mountains are controlled by subsurface bedrock erosion and diffusive slope processes. The results indicate rapid alluvial transport, minimal alluvial storage, and suggest that most of the cosmogenic nuclide inventory in sediments is accumulated while they are eroding from bedrock and traveling down hill slopes. Spatially homogeneous erosion rates of 25 - 30 mm Ky-1 are calculated throughout the Great Smoky Mountains using measured concentrations of cosmogenic 10Be and 26Al in quartz separated from alluvial sediment. 10Be and 26Al concentrations in sediments collected from headwater tributaries that have no upstream samples (n=18) are consistent with an average erosion rate of 28 ?? 8 mm Ky-1, similar to that of the outlet rivers (n=16, 24 ?? 6 mm Ky-1), which carry most of the sediment out of the mountain range. Grain-size-specific analysis of 6 alluvial sediment samples shows higher nuclide concentrations in smaller grain sizes than in larger ones. The difference in concentrations arises from the large elevation distribution of the source of the smaller grains compared with the narrow and relatively low source elevation of the large grains. Large sandstone clasts disaggregate into sand-size grains rapidly during weathering and downslope transport; thus, only clasts from the lower parts of slopes reach the streams. 26Al/10Be ratios do not suggest significant burial periods for our samples. However, alluvial samples have lower 26Al/10Be ratios than bedrock and colluvial samples, a trend consistent with a longer integrated cosmic ray exposure history that includes periods of burial during down-slope transport. The results confirm some of the basic ideas embedded in Davis' geographic cycle model, such as the reduction of relief

  18. Alpine debris flows triggered by a 28 July 1999 thunderstorm in the central Front Range, Colorado

    USGS Publications Warehouse

    Godt, J.W.; Coe, J.A.

    2007-01-01

    On 28 July 1999, about 480 alpine debris flows were triggered by an afternoon thunderstorm along the Continental Divide in Clear Creek and Summit counties in the central Front Range of Colorado. The thunderstorm produced about 43??mm of rain in 4??h, 35??mm of which fell in the first 2??h. Several debris flows triggered by the storm impacted Interstate Highway 70, U.S. Highway 6, and the Arapahoe Basin ski area. We mapped the debris flows from color aerial photography and inspected many of them in the field. Three processes initiated debris flows. The first process initiated 11% of the debris flows and involved the mobilization of shallow landslides in thick, often well vegetated, colluvium. The second process, which was responsible for 79% of the flows, was the transport of material eroded from steep unvegetated hillslopes via a system of coalescing rills. The third, which has been termed the "firehose effect," initiated 10% of the debris flows and occurred where overland flow became concentrated in steep bedrock channels and scoured debris from talus deposits and the heads of debris fans. These three processes initiated high on steep hillsides (> 30??) in catchments with small contributing areas (< 8000??m2), however, shallow landslides occurred on slopes that were significantly less steep than either overland flow process. Based on field observations and examination of soils mapping of the northern part of the study area, we identified a relation between the degree of soil development and the process type that generated debris flows. In general, areas with greater soil development were less likely to generate runoff and therefore less likely to generate debris flows by the firehose effect or by rilling. The character of the surficial cover and the spatially variable hydrologic response to intense rainfall, rather than a threshold of contributing area and topographic slope, appears to control the initiation process in the high alpine of the Front Range. Because

  19. Near-Channel Sources and Sinks along a Mountainous Stream: Establishing the Controls and Time Scales of the Lateral Transfer of Sediment and Carbon

    NASA Astrophysics Data System (ADS)

    Gartner, J. D.; Renshaw, C. E.

    2015-12-01

    River channels exchange sediment, carbon, and other matter with hillslopes and floodplains. An ongoing challenge is to quantify the time and length scales of these lateral interactions, and to establish physical controls on direction of transfer. Here we investigate whether downstream changes in stream power (Ω) can predict near-channel sources or sinks of matter on decadal time scales in a case study of Mink Brook, a 50 km2 watershed in New Hampshire, USA. Building on the Exner equation, we hypothesize that reaches with downstream increases in stream power (Ω↑) exhibit near-channel deposition and accumulation of organic matter, and reaches of downstream decreases in stream power (Ω↓) exhibit near-channel erosion and stripping of organic matter. We measured 210Pbex inventory (an indicator of erosion versus deposition), organic matter inventory, grain size, and depth of alluvium/colluvium in 29 soil pits at 6 cross sections along the brook. Sites had equivalent total Ω for a given storm event. However, 3 cross sections exhibited Ω↑, and 3 exhibited Ω↓. All cross sections showed a general trend of stripping of organic matter and fine sediment particles in the channel, paired with loading of matter at the ~2-year flood elevation. From the ~2- to ~25-year flood elevation, a marked difference appeared between sites. The Ω↑ cross sections exhibited several locations of erosion and stripping of organic matter, as evidenced by low 210Pbex inventories (70 to 1,000 bq m-2), low organic matter inventories (17 to 219 kg m-2), and thin alluvial cover (average 23 cm). The low 210Pbex inventories, below the characteristic 6,000 bq m-2 of stable soil profiles in this region, suggest no areas had consistent deposition over the last century. In contrast, the Ω↓ cross sections exhibited deposition of fine particles and organic matter from the ~2- to ~25-year flood elevation, as evidenced by elevated 210Pbex inventories (up to 9,100 bq m-2), elevated organic matter

  20. Deriving earthquake history of the Knidos Fault Zone, SW Turkey, using cosmogenic 36Cl surface exposure dating of the fault scarp.

    NASA Astrophysics Data System (ADS)

    Yildirim, Cengiz; Ersen Aksoy, Murat; Akif Sarikaya, Mehmet; Tuysuz, Okan; Genc, S. Can; Ertekin Doksanalti, Mustafa; Sahin, Sefa; Benedetti, Lucilla; Tesson, Jim; Aster Team

    2016-04-01

    Formation of bedrock fault scarps in extensional provinces is a result of large and successive earthquakes that ruptured the surface several times. Extraction of seismic history of such faults is critical to understand the recurrence intervals and the magnitude of paleo-earthquakes and to better constrain the regional seismic hazard. Knidos on the Datca Peninsula (SW Turkey) is one of the largest cities of the antique times and sits on a terraced hill slope formed by en-echelon W-SW oriented normal faults. The Datça Peninsula constitutes the southern boundary of the Gulf of Gökova, one of the largest grabens developed on the southernmost part of the Western Anatolian Extensional Province. Our investigation relies on cosmogenic 36Cl surface exposure dating of limestone faults scarps. This method is a powerful tool to reconstruct the seismic history of normal faults (e.g. Schlagenhauf et al 2010, Benedetti et al. 2013). We focus on one of the most prominent fault scarp (hereinafter Mezarlık Fault) of the Knidos fault zone cutting through the antique Knidos city. We collected 128 pieces of tablet size (10x20cm) 3-cm thick samples along the fault dip and opened 4 conventional paleoseismic trenches at the base of the fault scarp. Our 36Cl concentration profile indicates that 3 to 4 seismic events ruptured the Mezarlık Fault since Last Glacial Maximum (LGM). The results from the paleoseismic trenching are also compatible with 36Cl results, indicating 3 or 4 seismic events that disturbed the colluvium deposited at the base of the scarp. Here we will present implications for the seismic history and the derived slip-rate of the Mezarlık Fault based on those results. This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 113Y436) and it was conducted with the Decision of the Council of Ministers with No. 2013/5387 on the date 30.09.2013 and was done with the permission of Knidos Presidency of excavation in

  1. Multiple-Event Deformation on the West Tahoe Fault from Lidar and Trenching: Reconciling On and Offshore Paleoseismology

    NASA Astrophysics Data System (ADS)

    Seitz, G. G.; Mareschal, M.

    2014-12-01

    The West Tahoe Fault has a mapped length of 45 km, and its vertical slip rate is estimated at 0.6-1.0 mm/yr (Dingler et al., 2009). It is the range bounding, east dipping normal fault along the west margin of the basin, and the highest slip rate section is located along the western base of Lake Tahoe at a water depth of 400-500 m. In the lake, the fault has clearly defined scarps that displace submarine fans, lake-bottom sediments, and the ~50 ka age (Kent et al., 2005; Smith et al, 2013) McKinney Bay slide. Onshore the fault displaces tree-covered glacial and fluvial landforms. In October 2013 we conducted the first trenching study of the geomorphically well-defined West Tahoe Fault. Using Lidar, we selected a site with fine-grained surface sediments, as opposed to the boulder-rich moraine sediments that cover most of the onshore fault. The site is located ~3.5 km from the southern end of the mapped fault, adjacent to Osgood Swamp. In the excavation, we observed an east-dipping, normal fault juxtaposing glacial deposits against datable peat-bearing and charcoal-rich younger alluvial sediments. The glacial deposits and peat layers can be matched across the fault. Clear evidence for two earthquakes was based on scarp-derived colluvium, fissures, faulted scarp-related alluvium, liquefaction, and upward terminations of faults. Retrodeformation of the sediments results in nearly equal vertical displacements of about 1.7 m/event. Results from multiple C-14 analysis place the most recent event at ~5.3 ka and the penultimate event at ~7.4 ka. The fault scarp at the trench is 3.5 m high; at the bottom of the lake at a depth of 400 m a postulated same-age fan as the trench site post-glacial deposits, has a vertical scarp of 10-12 m. As expected the slip rate decreases towards the southern end of the fault. However, if the same number of events resulted in the underwater scarp then events must average about 5-6 m vertical displacement per event. This has serious implications

  2. Holocene earthquakes and right-lateral slip on the left-lateral Darrington-Devils Mountain fault zone, northern Puget Sound, Washington

    USGS Publications Warehouse

    Personius, Stephen F.; Briggs, Richard W.; Nelson, Alan R.; Schermer, Elizabeth R; Maharrey, J. Zebulon; Sherrod, Brian; Spaulding, Sarah A.; Bradley, Lee-Ann

    2014-01-01

    Sources of seismic hazard in the Puget Sound region of northwestern Washington include deep earthquakes associated with the Cascadia subduction zone, and shallow earthquakes associated with some of the numerous crustal (upper-plate) faults that crisscross the region. Our paleoseismic investigations on one of the more prominent crustal faults, the Darrington–Devils Mountain fault zone, included trenching of fault scarps developed on latest Pleistocene glacial sediments and analysis of cores from an adjacent wetland near Lake Creek, 14 km southeast of Mount Vernon, Washington. Trench excavations revealed evidence of a single earthquake, radiocarbon dated to ca. 2 ka, but extensive burrowing and root mixing of sediments within 50–100 cm of the ground surface may have destroyed evidence of other earthquakes. Cores in a small wetland adjacent to our trench site provided stratigraphic evidence (formation of a laterally extensive, prograding wedge of hillslope colluvium) of an earthquake ca. 2 ka, which we interpret to be the same earthquake documented in the trenches. A similar colluvial wedge lower in the wetland section provides possible evidence for a second earthquake dated to ca. 8 ka. Three-dimensional trenching techniques revealed evidence for 2.2 ± 1.1 m of right-lateral offset of a glacial outwash channel margin, and 45–70 cm of north-side-up vertical separation across the fault zone. These offsets indicate a net slip vector of 2.3 ± 1.1 m, plunging 14° west on a 286°-striking, 90°-dipping fault plane. The dominant right-lateral sense of slip is supported by the presence of numerous Riedel R shears preserved in two of our trenches, and probable right-lateral offset of a distinctive bedrock fault zone in a third trench. Holocene north-side-up, right-lateral oblique slip is opposite the south-side-up, left-lateral oblique sense of slip inferred from geologic mapping of Eocene and older rocks along the fault zone. The cause of this slip reversal is

  3. Characterizing Controls of Riparian Width for Mountain Streams in the Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Polvi, L. E.; Wohl, E. E.

    2007-12-01

    High variability of mountain streams causes riparian width to vary greatly from changes in drainage, valley and channel characteristics. GIS- based models for predicting flood-prone width, valley bottoms, or riparian zones may not accurately reflect processes at the reach scale, therefore field verification and reach-specific studies are needed. Management of riparian areas often designates a generalized width, which may under- or over-estimate the true riparian width. This study examines correlations between potential control variables and riparian zone width in the Colorado Front Range. Results from this study will be used to predict the riparian zone as a proxy for flood-prone width in the semi-arid Colorado Front Range. We hypothesize that local controls interact with large- scale controls to determine floodplain processes. Large-scale controls identified are elevation, which reflects hydroclimatology and glacial history, gradient and drainage area. Local controls are entrenchment, the ratio of the valley width to channel width, connectedness, defined as the distance from the channel to valley edge, presence of colluvium, and vegetation type, affecting roughness during flooding and bank stability. We chose twenty reaches based on elevation, connectedness, gradient and drainage area using a GIS base map in anthropogenically undisturbed areas of the Colorado Front Range, which included the Cache la Poudre and North St. Vrain drainages. Riparian width was defined using a three-tiered approach: evidence of fluvial processes and presence of riparian vegetation, compared with the Q100 stage. A longitudinal and two valley and channel cross-section surveys were completed at each stream reach to determine valley and channel geometry and bed gradient. Preliminary results show significant positive correlations between drainage area, entrenchment, and connectedness and riparian width, and negative correlations between gradient and riparian width, supporting the hypothesis

  4. Pleistocene glaciation of volcano Ajusco, central Mexico, and comparison with the standard Mexican glacial sequence

    NASA Astrophysics Data System (ADS)

    White, Sidney E.; Valastro, Salvatore

    1984-01-01

    Three Pleistocene glaciations and two Holocene Neoglacial advances occurred on volcano Ajusco in central Mexico. Lateral moraines of the oldest glaciation, the Marqués, above 3250 m are made of light-gray indurated till and are extensively modified by erosion. Below 3200 m the till is dark red, decomposed, and buried beneath volcanic colluvium and tephra. Very strongly to strongly developed soil profiles (Inceptisols) have formed in the Marqués till and in overlying colluvia and tephra. Large sharp-crested moraines of the second glaciation, the Santo Tomás, above 3300 m are composed of pale-brown firm till and are somewhat eroded by gullies. Below 3250 m the till is light reddish brown, cemented, and weathered. Less-strongly developed soil profiles (Inceptisols) have formed in the Santo Tomás till and in overlying colluvia and tephra. Narrow-crested moraines of yellowish-brown loose till of the third glaciation, the Albergue, are uneroded. Weakly developed soil profiles (Inceptisols) in the Albergue till have black ash in the upper horizon. Two small Neoglacial moraines of yellowish-brown bouldery till on the cirque floor of the largest valley support weakly developed soil profiles with only A and Cox horizons and no ash in the upper soil horizons. Radiocarbon dating of organic matter of the B horizons developed in tills, volcanic ash, and colluvial volcanic sand includes ages for both the soil-organic residue and the humic-acid fraction, with differences from 140 to 660 yr. The dating provides minimum ages of about 27,000 yr for the Marqués glaciation and about 25,000 yr for the Santo Tomás glaciation. Dates for the overlying tephra indicate a complex volcanic history for at least another 15,000 yr. Comparison of the Ajusco glacial sequence with that on Iztaccíhuatl to the east suggests that the Marqués and Santo Tomás glaciations may be equivalent to the Diamantes glaciation First and Second advances, the Albergue to the Alcalican glaciations, and the

  5. Drainage Area-Dependent Knickpoint Generation Mechanisms, Smith River, northern California

    NASA Astrophysics Data System (ADS)

    Caldwell, D. J.; Kelsey, H. M.

    2011-12-01

    , that knickpoints in upper drainage area positions (less than about 250 km2) are a response to hillslope instabilities that catastrophically deposit colluvium in channels creating a stationary knickpoint on geologic timescales.

  6. Whole watershed quantification of net carbon fluxes by erosion and deposition within the Christina River Basin Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Aufdenkampe, A. K.; Karwan, D. L.; Aalto, R. E.; Marquard, J.; Yoo, K.; Wenell, B.; Chen, C.

    2012-12-01

    We have proposed that the rate at which fresh, carbon-free minerals are delivered to and mix with fresh organic matter determines the rate of carbon preservation at a watershed scale (Aufdenkampe et al. 2011). Although many studies have examined the role of erosion in carbon balances, none consider that fresh carbon and fresh minerals interact. We believe that this mechanism may be a dominant sequestration process in watersheds with strong anthropogenic impacts. Our hypothesis - that the rate of mixing fresh carbon with fresh, carbon-free minerals is a primary control on watershed-scale carbon sequestration - is central to our Christina River Basin Critical Zone Observatory project (CRB-CZO, http://www.udel.edu/czo/). The Christina River Basin spans 1440 km2 from piedmont to Atlantic coastal plain physiographic provinces in the states of Pennsylvania and Delaware, and experienced intensive deforestation and land use beginning in the colonial period of the USA. Here we present a synthesis of multi-disciplinary data from the CRB-CZO on materials as they are transported from sapprolite to topsoils to colluvium to suspended solids to floodplains, wetlands and eventually to the Delaware Bay estuary. At the heart of our analysis is a spatially-integrated, flux-weighted comparison of the organic carbon to mineral surface area ratio (OC/SA) of erosion source materials versus transported and deposited materials. Because source end-members - such as forest topsoils, farmed topsoils, gullied subsoils and stream banks - represent a wide distribution of initial, pre-erosion OC/SA, we quantify source contributions using geochemical sediment fingerprinting approaches (Walling 2005). Analytes used for sediment fingerprinting include: total mineral elemental composition (including rare earth elements), fallout radioisotope activity for common erosion tracers (beryllium-7, beryllium-10, lead-210, cesium-137), particle size distribution and mineral specific surface area, in addition

  7. Whole Watershed Quantification of Net Carbon Fluxes by Erosion and Deposition within the Christina River Basin Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Aufdenkampe, A. K.; Karwan, D. L.; Aalto, R. E.; Marquard, J.; Yoo, K.; Wenell, B.; Chen, C.

    2013-12-01

    We have proposed that the rate at which fresh, carbon-free minerals are delivered to and mix with fresh organic matter determines the rate of carbon preservation at a watershed scale (Aufdenkampe et al. 2011). Although many studies have examined the role of erosion in carbon balances, none consider that fresh carbon and fresh minerals interact. We believe that this mechanism may be a dominant sequestration process in watersheds with strong anthropogenic impacts. Our hypothesis - that the rate of mixing fresh carbon with fresh, carbon-free minerals is a primary control on watershed-scale carbon sequestration - is central to our Christina River Basin Critical Zone Observatory project (CRB-CZO, http://www.udel.edu/czo/). The Christina River Basin spans 1440 km2 from piedmont to Atlantic coastal plain physiographic provinces in the states of Pennsylvania and Delaware, and experienced intensive deforestation and land use beginning in the colonial period of the USA. Here we present a synthesis of multi-disciplinary data from the CRB-CZO on materials as they are transported from sapprolite to topsoils to colluvium to suspended solids to floodplains, wetlands and eventually to the Delaware Bay estuary. At the heart of our analysis is a spatially-integrated, flux-weighted comparison of the organic carbon to mineral surface area ratio (OC/SA) of erosion source materials versus transported and deposited materials. Because source end-members - such as forest topsoils, farmed topsoils, gullied subsoils and stream banks - represent a wide distribution of initial, pre-erosion OC/SA, we quantify source contributions using geochemical sediment fingerprinting approaches (Walling 2005). Analytes used for sediment fingerprinting include: total mineral elemental composition (including rare earth elements), fallout radioisotope activity for common erosion tracers (beryllium-7, beryllium-10, lead-210, cesium-137), particle size distribution and mineral specific surface area, in addition

  8. Using Logistic Regression and Random Forests multivariate statistical methods for landslide spatial probability assessment in North-Est Sicily, Italy

    NASA Astrophysics Data System (ADS)

    Trigila, Alessandro; Iadanza, Carla; Esposito, Carlo; Scarascia-Mugnozza, Gabriele

    2015-04-01

    North-East Sicily is strongly exposed to shallow landslide events. On October, 1st 2009 a severe rainstorm (225.5 mm of cumulative rainfall in 9 hours) caused flash floods and more than 1000 landslides, which struck several small villages as Giampilieri, Altolia, Molino, Pezzolo, Scaletta Zanclea, Itala, with 31 fatalities, 6 missing persons and damage to buildings and transportation infrastructures. Landslides, mainly consisting in earth and debris translational slides evolving into debris flows, triggered on steep slopes involving colluvium and regolith materials which cover the underlying metamorphic bedrock of Peloritani Mountains. In this area catchments are small (about 10 square kilometres), elongated, with steep slopes, low order streams, short time of concentration, and discharge directly into the sea. In the past, landslides occurred at Altolia in 1613 and 2000, at Molino in 1750, 1805 and 2000, at Giampilieri in 1791, 1918, 1929, 1932, 2000 and on October 25, 2007. The aim of this work is to define susceptibility models for shallow landslides using multivariate statistical analyses in the Giampilieri area (25 square kilometres). A detailed landslide inventory map has been produced, as the first step, through field surveys coupled with the observation of high resolution aerial colour orthophoto taken immediately after the event. 1,490 initiation zones have been identified; most of them have planimetric dimensions ranging between tens to few hundreds of square metres. The spatial hazard assessment has been focused on the detachment areas. Susceptibility models, performed in a GIS environment, took into account several parameters. The morphometric and hydrologic parameters has been derived from a detailed LiDAR 1×1 m. Square grid cells of 4×4 m were adopted as mapping units, on the basis of the area-frequency distribution of the detachment zones, and the optimal representation of the local morphometric conditions (e.g. slope angle, plan curvature). A

  9. Fault-scarp morphology and amount of surface offset on late-Quaternary surficial deposits, eastern escarpment of the central Sierra Nevada, CA

    SciTech Connect

    Berry, M.E. . Dept. of Geology)

    1992-01-01

    Faults scarps, formed on glacial deposits and an alluvial fan near the east-central Sierra Nevada mountain front by late-Quaternary movement on the Hilton Creek (HCF), Wheeler Crest (WCFZ) and Coyote Warp (CWFZ) fault zones, were profiled to determine the amount and to estimate the recency of fault offset. Areas studied include McGee (N--near Lake Crowley), Pine, Mount Tom, Basin Mountain, McGee (S--near Bishop), and Bishop Creek drainages. The profile data indicate that movement of the range-front faults (HCF and WCFZ), which is characterized by normal slip, has offset Tioga-age deposits 6.5-26 m. Offset of Tahoe-age moraines cannot be measured directly because the landforms are buried at the mountain-front by moraines from later glaciations. However, the amount of offset is estimated at 52--130 m, based on crest-height differences between Tahoe and Tioga moraines. The rates of slip are highest on the northern end of the HCF, at McGee (N) Creek; the higher slip rates in this latter area may be related to its close proximity to the Long Valley caldera, where tectonic processes are complex and considered closely related to ongoing magmatic activity. The preservation of bevels on the fault scarps in both HCF and WCFZ, combined with the amounts of surface offset on the late-Pleistocene moraines, and AMS C-14 dates for charcoal found in fault-scarp colluvium, indicate that large ground-rupturing events have occurred on these faults during the Holocene. In contrast to the mountain-front faults, faults in the CWFZ, on a broad warp that separates the WCFZ from range-front faults to the south of Bishop, do not cross Tioga moraines, implying that surface rupture has not occurred in the CWFZ for at least 15,000-25,000 years. The degraded morphology of the fault scarps on adjacent Tahoe and pre-Tahoe moraines, which have been offset between 10.5 and 30 m, attests to the lack of late-Pleistocene and Holocene fault activity in this latter area.

  10. Detrital shocked minerals: microstructural provenance indicators of impact craters

    NASA Astrophysics Data System (ADS)

    Cavosie, A. J.

    2014-12-01

    The study of detrital shocked minerals (DSMs) merges planetary science, sedimentology, mineralogy/crystallography, accessory mineral geochemistry, and geochronology, with the goal of identifying and determining provenance of shock metamorphosed sand grains. Diagnostic high-pressure impact-generated microstructures (planar fractures, planar deformation features) are readily identified on external grain surfaces using standard SEM imaging methods (BSE), and when found, unambiguously confirm an impact origin for a given sand grain. DSMs, including quartz, zircon, monazite, and apatite, have thus far been documented at the Vredefort Dome [1,2,3], Sudbury [4], Rock Elm [5], and Santa Fe [6,7] impact structures. DSMs have been identified in alluvium, colluvium, beach sand, and glacial deposits. Two main processes are recognized that imply the global siliciclastic record contains DSMs: they survive extreme distal transport, and they survive 'deep time' lithification. Distal transport: In South Africa, shocked minerals are preserved in alluvium from the Vaal River >750 km downstream from the Vredefort impact; SHRIMP U-Pb geochronology has confirmed the origin of detrital shocked zircon and monazite from shocked Vredefort bedrock [2]. Vredefort-derived shocked zircons have also been found at the mouth of the Orange River on the Atlantic coast, having travelled ~2000 km downriver from Vredefort [8]. Deep time preservation: Vredefort-derived shocked zircon and quartz has been documented in glacial diamictite from the 300 Myr-old Dwyka Group in South Africa. Shocked minerals were thus entrained and transported in Paleozoic ice sheets that passed over Vredefort [9]. An impact crater can thus be viewed as a unique 'point source', in some cases for billions of years [2,4]; DSMs thus have applications in studying eroded impact craters, sedimentary provenance, landscape evolution, and long-term sediment transport processes throughout the geologic record. This work was supported by

  11. Revised Geologic Map of the Fort Garland Quadrangle, Costilla County, Colorado

    USGS Publications Warehouse

    Wallace, Alan R.; Machette, Michael N.

    2008-01-01

    The map area includes Fort Garland, Colo., and the surrounding area, which is primarily rural. Fort Garland was established in 1858 to protect settlers in the San Luis Valley, then part of the Territory of New Mexico. East of the town are the Garland mesas (basalt-covered tablelands), which are uplifted as horsts with the Central Sangre de Cristo fault zone. The map also includes the northern part of the Culebra graben, a deep structural basin that extends from south of San Luis (as the Sanchez graben) to near Blanca, about 8 km west of Fort Garland. The oldest rocks exposed in the map area are early Proterozic basement rocks (granites in Ikes Creek block) that occupy an intermediate structural position between the strongly uplifted Blanca Peak block and the Culebra graben. The basement rocks are overlain by Oligocene volcanic and volcaniclastic rocks of unknown origin. The volcanic rocks were buried by a thick sequence of basin-fill deposits of the Santa Fe Group as the Rio Grande rift formed about 25 million years ago. The Servilleta Basalt, a regional series of 3.7?4.8 Ma old flood basalts, was deposited within sediment, and locally provides a basis for dividing the group into upper and lower parts. Landslide deposits and colluvium that rest on sediments of the Santa Fe Group cover the steep margins of the mesas. Exposures of the sediment beneath the basalt and within the low foothills east of the Central Sangre de Cristo fault zone are comprised of siltstones, sandstones, and minor fluvial conglomerates. Most of the low ground surrounding the mesas and in the graben is covered by surficial deposits of Quaternary age. The alluvial deposits are subdivided into three Pleistocene-age units and three Holocene-age units. The oldest Pleistocene gravel (unit Qao) is preserved as isolated remnants that cap high surfaces north and east of Fort Garland. The primary geologic hazards in the map area are from earthquakes, landslides, and localized flooding. The Central

  12. Flashy Water and Sediment Delivery to Fluvial Megafan andFan Delta Systems on Opposing Shorelines of an Early Eocene Lake

    NASA Astrophysics Data System (ADS)

    Jones, E. R.; Plink-Bjorklund, P.

    2015-12-01

    Flashy delivery of water and sediment had distinct effects on the process of deposition in coeval fluvial megafan and fan delta deposits on opposing shorelines of a paleolake that occupied the Uinta Basin throughout the Eocene. The Tertiary Uinta Basin was an asymmetric continental interior basin with a steep northern margin, adjacent to the block uplift controlling basin subsidence, and a low gradient southern margin. A ~140 km wide fluvial megafan with catchments as far as ~750 km away occupied the southern margin of the lacustrine basin. Within this megafan system, fluvial deposits contain within-channel continental bioturbation and paleosol development on bar accretion surfaces that are evidence of prolonged periods of groundwater flow or channel abandonment. These are punctuated by channel fills exhibiting a suite of both high-deposition rate and upper flow regime sedimentary structures that were deposited by very rapid suspension-fallout during seasonal to episodic river flooding events. A series of small (~8 km wide) and proximally sourced fan deltas fed sediment into the steeper northern margin of the lacustrine basin. 35-50% of the deposits in the delta plain environment of these fan deltas are very sandy debris flows with as low as 5% clay and silt sized material. Detrital zircon geochronology shows that these fan deltas were tapping catchments where mostly unconsolidated Cretaceous sedimentary cover and thick Jurassic eolianites were being eroded. A combination of flashy precipitation, arid climate, catchments mantled by abundant loose sand-sized colluvium, and steep depositional gradients promoted generation of abundant very sandy (5-10% clay and silt sized material) debris flows. In this way, the Wasatch and Green River Formations in the Uinta Basin, Utah, U.S.A. gives us two very different examples of how routing flashy water and sediment delivery (associated with pulses of hyperthermal climate change during the Early Eocene) through different

  13. Numerical Study on Response of Groundwater Level to Rainfall at a Hillslope in Mid-Levels, Hong Kong

    NASA Astrophysics Data System (ADS)

    Nandy, S.; Jiao, J. J.

    2001-12-01

    Mid-Levels is an area on the north-facing slopes of Victoria Peak on Hong Kong Island, Hong Kong, China. The lower part of the area is probably one of the most extensively urbanized areas in the world, with sky scrapping buildings along the coast of Victoria Harbour, while the upper part of the area comprises natural steep slopes with well-developed vegetations. This area consists of volcanic and granite rocks overlain by colluvium and residual soils and has a history of instability owing to the steep topography. Some piezometer clusters were installed in early 1980s in this region for a geotechnical project associated with slope stability study. The piezometers in the transitional zone between the natural slopes and the urbanized areas indicated a delayed but significant response to rainfall and obvious upward groundwater flow, while those in the urbanized area were much less sensitive to rainfall and did not show any upward flow. To understand these piezometric responses to rainfall in the hillslope, a typical cross section through two piezometer clusters is chosen for detailed study. The groundwater flow along the section is represented by a two-dimensional multilayered numerical model and simulated by MODFLOW. The aquifer parameters and structure of the aquifer system are calibrated by comparing the simulated water levels with the observed ones. To reproduce the observed behavior of the water levels, the model has to include two important characteristics. One is a highly permeable zone at the rockhead. The other is that the hydraulic conductivities of the urbanized area are one order of magnitude lower than those of the upper natural part of the hillside. The high permeability zone in the model confirms the previous discussion elsewhere by the authors on the hydraulic conductivity distribution of a typical weathering profile of igneous rocks in Hong Kong. The significant reduction in the lateral hydraulic conductivity may reflect the reduction in the overall

  14. A 3000-year record of ground-rupturing earthquakes along the central North Anatolian fault near Lake Ladik, Turkey

    USGS Publications Warehouse

    Fraser, J.; Pigati, J.S.; Hubert-Ferrari, A.; Vanneste, K.; Avsar, U.; Altinok, S.

    2009-01-01

    The North Anatolian fault (NAF) is a ???1500 km long, arcuate, dextral strike-slip fault zone in northern Turkey that extends from the Karliova triple junction to the Aegean Sea. East of Bolu, the fault zone exhibits evidence of a sequence of large (Mw >7) earthquakes that occurred during the twentieth century that displayed a migrating earthquake sequence from east to west. Prolonged human occupation in this region provides an extensive, but not exhaustive, historical record of large earthquakes prior to the twentieth century that covers much of the last 2000 yr. In this study, we extend our knowledge of rupture events in the region by evaluating the stratigraphy and chronology of sediments exposed in a paleoseismic trench across a splay of the NAF at Destek, ???6:5 km east of Lake Ladik (40.868?? N, 36.121?? E). The trenched fault strand forms an uphill-facing scarp and associated sediment trap below a small catchment area. The trench exposed a narrow fault zone that has juxtaposed a sequence of weakly defined paleosols interbedded with colluvium against highly fractured bedrock. We mapped magnetic susceptibility variations on the trench walls and found evidence for multiple visually unrecognized colluvial wedges. This technique was also used to constrain a predominantly dip-slip style of displacement on this fault splay. Sediments exposed in the trench were dated using both charcoal and terrestrial gastropod shells to constrain the timing of the earthquake events. While the gastropod shells consistently yielded 14 C ages that were too old (by ???900 yr), we obtained highly reliable 14 C ages from the charcoal by dating multiple components of the sample material. Our radiocarbon chronology constrains the timing of seven large earthquakes over the past 3000 yr prior to the 1943 Tosya earthquake, including event ages of (2?? error): A.D. 1437-1788, A.D. 1034-1321, A.D. 549-719, A.D. 17-585 (1-3 events), 35 B.C.-A.D. 28, 700-392 B.C., 912-596 B.C. Our results

  15. Field and Laboratory Data From an Earthquake History Study of Scarps of the Lake Creek-Boundary Creek Fault Between the Elwha River and Siebert Creek, Clallam County, Washington

    USGS Publications Warehouse

    Nelson, Alan R.; Personius, Stephen F.; Buck, Jason; Bradley, Lee-Ann; Wells, Ray E.; Schermer, Elizabeth R.

    2007-01-01

    Fault scarps recently discovered on Airborne Laser Swath Mapping (ALSM; also known as LiDAR) imagery show Holocene movement on the Lake Creek-Boundary Creek fault on the north flank of the Olympic Mountains of northwestern Washington State. Such recent movement suggests the fault is a potential source of large earthquakes. As part of the effort to assess seismic hazard in the Puget Sound region, we map scarps on ALSM imagery and show primary field and laboratory data from backhoe trenches across scarps that are being used to develop a latest Pleistocene and Holocene history of large earthquakes on the fault. Although some scarp segments 0.5-2 km long along the fault are remarkably straight and distinct on shaded ASLM imagery, most scarps displace the ground surface <1 m, and, therefore, are difficult to locate in dense brush and forest. We are confident of a surface-faulting or folding origin and a latest Pleistocene to Holocene age only for scarps between Lake Aldwell and the easternmost fork of Siebert Creek, a distance of 22 km. Stratigraphy in five trenches at four sites help determine the history of surface-deforming earthquakes since glacier recession and alluvial deposition 11-17 ka. Although the trend and plunge of indicators of fault slip were measured only in the weathered basalt exposed in one trench, upward-splaying fault patterns and inconsistent displacement of successive beds along faults in three of the five trenches suggest significant lateral as well as vertical slip during the surface-faulting or folding earthquakes that produced the scarps. Radiocarbon ages on fragments of wood charcoal from two wedges of scarp-derived colluvium in a graben-fault trench suggest two surface-faulting earthquakes between 2,000 and 700 years ago. The three youngest of nine radiocarbon ages on charcoal fragments from probable scarp-derived colluvum in a fold-scarp trench 1.2 km to the west suggest a possible earlier surface-faulting earthquake less than 5,000 years

  16. Can the flow dynamics of debris flows be identified from seismic data?

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; Coe, J. A.; Smith, J. B.; Coviello, V.; McCoy, S. W.

    2014-12-01

    There is growing interest in the use of seismic and acoustic data to interpret a variety of geomorphic processes including landslides and debris flows. This measurement technique is attractive because a broad area can be monitored from a safe distance, unlike more direct methods of instrumentation, which are restricted to known flow paths and are vulnerable to damage by the flow. Previous work has shown that measurements of ground vibrations are capable of detecting the timing, speed, and location of landslides and debris flows. A remaining question is whether or not additional flow properties, such as basal stress, impact force, or flow magnitude can be inferred reliably from seismic data. This question has been difficult to answer, because detailed, independent measurements of flow dynamics are lacking. Here, we explore characteristics of debris-flow induced ground vibrations using new data from the Chalk Cliffs monitoring site in central Colorado. Monitoring included a heavily instrumented cross-section consisting of two tri-axial geophones to record ground vibrations (at 333 Hz), a small, 225 cm2 force plate to record basal impact forces (at 333 Hz), a laser distance meter to record flow stage over the plate (at 10 Hz), and a high definition camera to record flow dynamics (at 24 Hz). One geophone (A) was mounted on a boulder partially buried in colluvium; the other (B) was mounted directly to weathered bedrock typical of the site. This combination of instrumentation allowed us to compare the spectral response of different geophone installations to independently measured flow depth and basal impact force. We also compared the response of the geophones to surges that flowed over a sediment-covered bed (40-cm thick) to surges that flowed over a bare bedrock channel. Preliminary results showed that site conditions have a large effect on recorded debris-flow vibrations. The seismic signature of debris flow was very different between the geophones, with geophone B

  17. High N2O emission in an N-saturated subtropical forest, southwest China

    NASA Astrophysics Data System (ADS)

    Dörsch, P.; Zhu, J.; Mulder, J.

    2012-04-01

    Nitrogen (N)-saturated forests in subtropical China are significant N sinks, despite low forest growth rates. In a forested headwater catchment at Tieshanping, Chongqing, SW China, with 4 g N m-2a-1 atmogenic deposition (60% of which as NH4+-N) and leaching of only 0.6 g N m-2 a-1 (NO3--N dominated), we applied state-of-the-art field and laboratory methodologies to investigate the nature of the N sinks. The study included the determination of spatiotemporal patterns of N2O emission, a 15N labeling experiment and laboratory incubations to determine nitrification and denitrification characteristics and their gaseous product stoichiometries. Emission of N2O occurred predominantly during the wet season (summer), driven by rain episodes. N2O emission rates were particularly high along a hill slope (HS) with a thin organic surface layer overlaying an argic B horizon causing transient interflow during storm flow conditions. Lower N2O emission rates were observed at the foot slope in a colluvium-derived groundwater discharge zone (GDZ). Laboratory incubation experiments suggested that the difference in N2O emission rate is primarily due to higher N2O/N2 product ratios of denitrification in the HS topsoil being exposed to frequent drying-rewetting. Lower N2O/N2 product ratios in soils of the GDZ, in turn, could be attributed to more stable anoxia, lower NO3- availability and higher pH as compared with the hillslope, all of which favor the expression of N2O reductase. Estimated annual N2O emission for the relatively dry hydrological year 2009-2010 was 0.4 g N m-2, which is equivalent to approximately 10% of the annual input of reactive N. Measurements during summer 2009 indicated that N2O emissions can be even higher during wet years. A 15NO3- labeling experiment conducted on HS soils during summer revealed that between 75 and 86% of the N2O emission derived from denitrification during the first 6 days after label addition, accounting for 8-15% of the applied NO3--N. Our

  18. On the similarity in shape between debris-flow channels and high-gradient flood channels: Initial insight from continuum models for granular and water flow

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; McCoy, S. W.; Tucker, G. E.

    2011-12-01

    The cross-sectional shape of high-gradient bedrock channels carved by debris flows is often very similar to that of channels formed by fluvial erosion. Both tend to have narrow U-shapes with width-to-depth ratios much less than 10. Gullies and channels cut into colluvium by both water erosion and debris-flow erosion have similarly narrow geometries. Given that the physics governing debris flow and turbulent water flow are very different, why are channels eroded by these two processes so similar in shape? To begin to investigate this question, we conducted a series of numerical simulations using continuum models for the end-member cases of granular flow and water flow. Each model is used to evolve the steady-state channel shape formed by uniform flow of the respective material. The granular model is based on the constitutive equation for dense granular flow proposed by Jop et al. (Nature, 2006). They demonstrated that without any fitting parameters, a numerical model using this constitutive equation could reproduce the velocity and depth profiles observed in granular-flow laboratory experiments. The model for water flow uses a ray-isovel turbulence closure to calculate the boundary shear stress across the wetted perimeter of the channel. This fully predictive model has also been shown to be in good agreement with laboratory data. We start the calculations for the granular and water-flow cases by determining the velocity and boundary shear-stress fields in an initial V-shape cross section. We then erode both channels using a simple wear law scaled linearly by the bed-normal boundary shear stress. The calculation is repeated until the channel reaches an equilibrium shape. Initial comparisons of the granular and water-flow channels show that they have very similar width-to-depth ratios of about four, and only moderate differences in bottom geometries and boundary shear-stress distributions. The structure of the velocity field differs more substantially between the two

  19. Holocene tectonics and fault reactivation in the foothills of the north Cascade Mountains, Washington

    USGS Publications Warehouse

    Sherrod, Brian L.; Barnett, Elizabeth; Schermer, Elizabeth; Kelsey, Harvey M.; Hughes, Jonathan; Foit, Franklin F.; Weaver, Craig S.; Haugerud, Ralph; Hyatt, Tim

    2013-01-01

    We use LiDAR imagery to identify two fault scarps on latest Pleistocene glacial outwash deposits along the North Fork Nooksack River in Whatcom County, Washington (United States). Mapping and paleoseismic investigation of these previously unknown scarps provide constraints on the earthquake history and seismic hazard in the northern Puget Lowland. The Kendall scarp lies along the mapped trace of the Boulder Creek fault, a south-dipping Tertiary normal fault, and the Canyon Creek scarp lies in close proximity to the south-dipping Canyon Creek fault and the south-dipping Glacier Extensional fault. Both scarps are south-side-up, opposite the sense of displacement observed on the nearby bedrock faults. Trenches excavated across these scarps exposed folded and faulted late Quaternary glacial outwash, locally dated between ca. 12 and 13 ka, and Holocene buried soils and scarp colluvium. Reverse and oblique faulting of the soils and colluvial deposits indicates at least two late Holocene earthquakes, while folding of the glacial outwash prior to formation of the post-glacial soil suggests an earlier Holocene earthquake. Abrupt changes in bed thickness across faults in the Canyon Creek excavation suggest a lateral component of slip. Sediments in a wetland adjacent to the Kendall scarp record three pond-forming episodes during the Holocene—we infer that surface ruptures on the Boulder Creek fault during past earthquakes temporarily blocked the stream channel and created an ephemeral lake. The Boulder Creek and Canyon Creek faults formed in the early to mid-Tertiary as normal faults and likely lay dormant until reactivated as reverse faults in a new stress regime. The most recent earthquakes—each likely Mw > 6.3 and dating to ca. 8050–7250 calendar years B.P. (cal yr B.P.), 3190–2980 cal. yr B.P., and 910–740 cal. yr B.P.—demonstrate that reverse faulting in the northern Puget Lowland poses a hazard to urban areas between Seattle (Washington) and Vancouver

  20. Cosmogenic Exposure Dating of Paleo-Rockfall Deposits, Christchurch, New Zealand

    NASA Astrophysics Data System (ADS)

    Mackey, B. H.; Quigley, M.

    2013-12-01

    The 22nd February 2011 MW 6.2 Christchurch earthquake occurred on a previously unrecognized blind thrust fault and generated severe localized vertical ground accelerations (>2 g). Constraining rupture history for such faults is challenging as there is no surface evidence of faulting (e.g., scarps, fault traces) which can be studied directly. However, the earthquake generated a range of secondary effects, including extensive rockfall and cliff collapse at many locations around the Port Hills south of Christchurch, remnants of a Miocene strato-shield volcanic complex. Many of these sites also exhibit pre-historic rockfall deposits. Here we ask whether ancient rockfall deposits can serve as off-fault evidence for paleo-earthquakes, and can be used to constrain the timing of previous episodes of severe shaking? Our site at Rapaki Bay west of Lyttelton is ideally suited for analysis of paleo-rockfall events as it has a prominent 60 m high sub-vertical cliff comprised of stratified lava flows, and a 600-m-long planar fore-slope. The site experienced significant, well-documented rockfall during the 2011 event, and has large (2-10 m diameter), lichen-covered boulders scattered down slope and partially embedded in late Quaternary loess and colluvium. We employ cosmogenic exposure dating of paleo-rockfall boulders to establish the timing of boulder emplacement. The basalt rock contains abundant clinopyroxene (augite) which is able to quantitatively retain cosmogenic 3He. This approach requires constraining the inherited 3He from non-cosmogenic sources, the potential cosmogenic exposure while boulders are on the cliff, and the background erosion rate. The probability distribution of exposure ages from the surface of pre-historically emplaced boulders show significant clustering of ages in the mid Holocene, with a long tail of individual ages out to ~60 ka. Comparison with numerical modeling of a range of rockfall event scenarios reveals the measured age distribution is most

  1. Extensive Quaternary aeolian deposits in the Drakensberg foothills, Rooiberge, South Africa

    NASA Astrophysics Data System (ADS)

    Telfer, M. W.; Mills, S. C.; Mather, A. E.

    2014-08-01

    Deposits of aeolian sand are known to have accumulated in periglacial environments during the cold phases of the late Quaternary. In many instances, however, they form low-relief topographic units which may not be readily identified without detailed field survey. This study aims to use a multidisciplinary approach, combining remotely sensed data analysis and field survey, to investigate the extent and palaeoenvironmental significance of sand ramps in the Drakensberg/Rooiberge foothills of South Africa. Analysis of Google Earth™ imagery has demonstrated that gully systems are a common component of the landscape, and heterogeneously distributed across the landscape. Field investigation confirmed the hypothesis that the gullies are mainly eroding into sand ramps of fine sands and very coarse silts which mantle many of the lower hillslopes of the region. These sand units include palaeosols and occasional gravel lags, but are otherwise remarkable for their homogenous composition, cross-bedding and the complete absence of clasts. Much of the sediment is thus interpreted as aeolian in origin. The deposits are sufficiently similar in many respects to the Masotcheni Formation, a late Quaternary colluvium which outcrops abundantly in the Drakensberg, to propose an assignation to this unit. However, an aeolian component in the Masotcheni has not previously been described. The distribution of aeolian accumulation in the region is consistent with southward transport during late Quaternary cold phases from a source on the Highveld to the north of the study area. The low relief and complex fluvial network in this region would concentrate sediment eroded from the Drakensberg/Rooiberge, which would subsequently be available for deflation when the balance between fluvial flow regime, seasonally frozen ground and north-westerly trade winds were optimal for aeolian entrainment. Deposition is primarily topographically controlled, and is in places sufficiently extensive that it may be

  2. Preferential flow paths in paraglacial catchments: first order controls on the long-term stability of 'biodiversity hotspots' in a changing climate

    NASA Astrophysics Data System (ADS)

    Grocott, Michael; Kettridge, Nick; Bradley, Chris; Milner, Alexander

    2016-04-01

    PFPs are a fundamental first order control upon the occurrence of 'biodiversity hotspots' within paraglacial floodplains, and highlights their role as an important conduit for hillslope-floodplain connectivity. Given the expected changes in the hydrological dynamics of paraglacial catchments this research raises questions about the long-term stability of GW-fed streams, and whether the increasing relative importance of groundwater sources (e.g. from colluvium) can sustain flow of GW-fed streams. In addition glacial retreat and associated long-term declines in sediment yields could have negative implications for the development and renewal of PFPs across paraglacial floodplains, which would be detrimental to the persistence of 'biodiversity hotspots'.

  3. Late Pleistocene tectonic-geomorphological development within a passive margin — The Cariatá trough, northeastern Brazil

    NASA Astrophysics Data System (ADS)

    Bezerra, Francisco H. R.; Brito Neves, Benjamim B.; Corrêa, Antonio C. B.; Barreto, Alcina M. F.; Suguio, Kenitiro

    2008-05-01

    Studies on the geomorphological evolution of the South American passive margin have been based on the pediplanation model, which predicts that its morphology is a response to regional uniform uplift and concomitant development of erosion surfaces. We combined remote sensing, geological mapping, lithostratigraphic and facies analyses, and luminescence dating in the Cariatá trough, northeastern Brazil, in order to determine how brittle tectonics and climate influenced colluviation and the shaping of local landforms in the Quaternary. Our work indicates that Cariatá is an asymmetrical trough ˜ 40 km long, ˜ 25 km wide, 250-550 m deep, and delimited by ENE-WSW-trending faults to the north and south. We recognized an ENE-WSW-oriented compression related to a strike-slip faulting regime, which corresponds to the present-day stress field in the region. This faulting event led to the deposition of colluvial fans, shed from adjacent uplifted crustal blocks, in a tectonically controlled depression. The colluvial succession is ˜ 45 m thick and presents two facies assemblages that filled the southern and, in particular, the northern borders of the trough: non-cohesive debrisflow and mudflow deposits. Optically stimulated luminescence dates of the sedimentary infill yielded ages at 224-128 ka and 45-28 ka, dominated by debrisflow and mudflow deposits, respectively. These ages may be over-estimated due to poor bleaching of colluvium, but they and our field data suggest that the margins of the trough were tectonically uplifted and eroded twice in the Late Pleistocene. The spasmodic colluvial accretion reflects the occurrence of high-magnitude, low-recurrence episodes probably associated with climate shifts in a semi-arid hillslope system. It follows that the present-day low-lying piedmont in which the Cariatá trough occurs is a juxtaposition of surfaces of various ages. This trough may have counterparts across the region. These conclusions do not corroborate the application

  4. Reach-Scale Channel Adjustments to Channel Network Geometry in Mountain Bedrock Streams

    NASA Astrophysics Data System (ADS)

    Plitzuweit, S. J.; Springer, G. S.

    2008-12-01

    surveys in order to analyze whether stream power and shear stress are adjusted to reflect CNG at the reach- scale. These models are compared to those with discharges calculated using drainage area and precipitation totals alone. We conclude that gradients in bedrock mountain streams may reflect basin-scale hydrology (CNG) and not simply local geological or geomorphic factors. This challenges the conclusions of others who ascribe local channel adjustments to: i) lithology and structure alone, or ii) local colluvium grain sizes.

  5. Erosion processes, fluvial sediment transport, and reservoir sedimentation in a part of the Newell and Zayante Creek basins, Santa Cruz County, California

    USGS Publications Warehouse

    Brown, W. M.

    1973-01-01

    The drainage basins upstream from Loch Lomond, a water-supply reservoir on Newell Creek, and a proposed reservoir site on Zayante Creek were investigated for their characteristics with respect to the erosion, transportation, and deposition of sediment. The study area is underlain predominantly by sandstone, siltstone, and shale of Tertiary age that decompose readily into moderately deep soils, friable colluvium, and easily transported sediment particles. The Rices Mudstone and Twobar, Shale Members of the San Lorenzo Formation of Brabb (1964) underlie steep dip slopes in the study area, and probably are the most highly erodible of the several geologic units present there. However, nearly all of the geologic units have shown a propensity for accelerated erosion accompanying the disturbance of the land surface by the roadbuilding practices that predominate over other types of sediment-producing land-use activities in the study area. Sediment transport in the study area was estimated from (1) a reservoir survey of Loch Lomond in 1971 that was compared with a preconstruction survey of 1960, and (2) sampling of sediment transported in suspension by Zayante Creek during the 1970 and 1971 water years. At least 46 acre-feet of sediment accumulated in Loch Lomond in a 10-year period, and an unmeasured quantity of very fine sediment in the form of a thin layer over much of the reservoir bottom was observed. The measured quantity of deposited sediment in a 10-year period represented a sediment yield of about 1,100 tons annually per square mile of drainage basin upstream from the reservoir arms where the major deposition occurred. This sediment occupied less than i percent of the original capacity of Loch Lomond, but the volume of measured sediment deposition is probably conservative in view of the unmeasured deposits observed and a reservoir trap efficiency of about 95 percent. Sediment sampling on Zayante Creek indicated suspended-sediment yields of about 4,570 and 570 tons

  6. Landslides triggered by the 1946 Ancash earthquake, Peru

    NASA Astrophysics Data System (ADS)

    Kampherm, T. S.; Evans, S. G.; Valderrama Murillo, P.

    2009-04-01

    The 1946 M7.3 Ancash Earthquake triggered a large number of landslides in an epicentral area that straddled the Continental Divide of South America in the Andes of Peru. A small number of landslides were described in reconnaissance reports by E. Silgado and Arnold Heim published shortly after the earthquake, but further details of the landslides triggered by the earthquake have not been reported since. Utilising field traverses, aerial photograph interpretation and GIS, our study mapped 45 landslides inferred to have been triggered by the event. 83% were rock avalanches involving Cretaceous limestones interbedded with shales. The five largest rock/debris avalanches occurred at Rio Llama (est. vol. 37 M m3), Suytucocha (est. vol., 13.5 Mm3), Quiches (est. vol. 10.5 Mm3 ), Pelagatos (est. vol. 8 Mm3), and Shundoy (est. vol. 8 Mm3). The Suytucocha, Quiches, and Pelagatos landslides were reported by Silgado and Heim. Rock slope failure was most common on slopes with a southwest aspect, an orientation corresponding to the regional dip direction of major planar structures in the Andean foreland belt (bedding planes and thrust faults). In valleys oriented transverse to the NW-SE structural grain of the epicentral area, south-westerly dipping bedding planes combined with orthogonal joint sets to form numerous wedge failures. Many initial rock slope failures were transformed into rock/debris avalanches by the entrainment of colluvium in their path. At Acobamba, a rock avalanche that transformed into a debris avalanche (est. vol. 4.3 Mm3) overwhelmed a village resulting in the deaths of 217 people. The cumulative volume-frequency plot shows a strong power law relation below a marked rollover, similar in form to that derived for landslides triggered by the 1994 Northridge Earthquake. The total volume of the 45 landslides is approximately 93 Mm3. The data point for the Ancash Earthquake plots near the regression line calculated by Keefer (1994), and modified by Malamud et al

  7. Woodland clearance alters geomorphic, hydrologic, and pedogenic drivers of ecosystem services: examples from the southern Blue Ridge (USA) and the French western Pyrenees Mountains

    NASA Astrophysics Data System (ADS)

    Leigh, David

    2016-04-01

    The southern Blue Ridge (USA) and French western Pyrenees both are humid-temperate mountains where native woodlands have been cleared on soils formed in residuum and colluvium on hillslopes. Forest removal increased rates of erosion and sediment yield that drove both negative and positive ecosystem services. For example, the supportive ecosystem service of soil formation was diminished on eroded hillslopes, but may have been enhanced by accumulation of sediment on bottomlands far downstream from the highland source areas. Negative effects on provisional ecosystem services (e.g. water supply) resulted in aggraded bottomlands by increasing the depth to the water table. Legacy effects linger on hillslopes that reforested (diminished soil properties), and ongoing alteration of pedogenic and hydrologic processes affect pastures that persisted from cleared woodlands. Beyond those general similarities, pastures of the two regions exhibit very different pedogenic pathways and ecosystem service outcomes. Soils of the Blue Ridge pastures adhere to a typical degradation scenario of erosion, compaction, and reduced infiltration capacities, whereas Pyrenees pastures exhibit soil qualities trending in the opposite direction and arguably now are better quality soils than their forested predecessors. Major differences in temporal duration and management styles apparently have led to such contrasts in soil quality. The Blue Ridge pastures are only tens to hundreds of years old, whereas Pyrenees pastures are thousands of years old. Blue Ridge pastures are maintained by mowing with tractors and year-round grazing primarily with beef cattle, whereas Pyrenees pastures (outfields) lack tractors and are only grazed seasonally (summer), primarily with sheep. Fire is rarely used as a management tool in the Blue Ridge, while Pyrenees pastures frequently are burned. Such management practices, and their influence on pedogenic and hydrologic processes, generally have resulted in negative

  8. Laboratory Study of Quaternary Sediment Resistivity Related to Groundwater Contamination at Mae-Hia Landfill, Mueang District, Chiang Mai Province

    NASA Astrophysics Data System (ADS)

    Sichan, N.

    2007-12-01

    This study was aimed to understand the nature of the resistivity value of the sediment when it is contaminated, in order to use the information solving the obscure interpretation in the field. The pilot laboratory experiments were designed to simulate various degree of contamination and degree of saturation then observe the resulting changes in resistivity. The study was expected to get a better understanding of how various physical parameters effect the resistivity values in term of mathematic function. And also expected to apply those obtained function to a practical quantitatively interpretation. The sediment underlying the Mae-Hia Landfill consists of clay-rich material, with interfingerings of colluvium and sandy alluvium. A systematic study identified four kinds of sediment, sand, clayey sand, sandy clay, and clay. Representative sediment and leachate samples were taken from the field and returned to the laboratory. Both the physical and chemical properties of the sediments and leachate were analyzed to delineate the necessary parameters that could be used in Archie's equation. Sediment samples were mixed with various concentration of leachate solutions. Then the resistivity values were measured at various controlled steps in the saturation degree in a well- calibrated six-electrode model resistivity box. The measured resistivity values for sand, clayey sand, sandy clay when fully and partly saturated were collected, then plotted and fitted to Archie's equation, to obtain a mathematical relationship between bulk resistivity, porosity, saturation degree and resistivity of pore fluid. The results fit well to Archie's equation, and it was possible to determine all the unknown parameters representative of the sediment samples. For sand, clayey sand, sandy clay, and clay, the formation resistivity factors (F) are 2.90, 5.77, 7.85, and 7.85 with the products of cementation factor (m) and the pore geometry factors (a) (in term of -am) are 1.49, -1.63, -1.92, -2

  9. Environmental impacts of oil production on soil, bedrock, and vegetation at the U.S. Geological Survey Osage-Skiatook Petroleum Environmental Research site A, Osage County, Oklahoma

    USGS Publications Warehouse

    Otton, J.K.; Zielinski, R.A.; Smith, B.D.; Abbott, M.M.; Keeland, B.D.

    2005-01-01

    The U.S. Geological Survey is investigating the impacts of oil and gas production on soils, groundwater, surface water, and ecosystems in the United States. Two sites in northeastern Oklahoma (sites A and B) are presently being investigated under the Osage-Skiatook Petroleum Environmental Research project. Oil wells on the lease surrounding site A in Osage County, Oklahoma, produced about 100,000 bbl of oil between 1913 ard 1981. Prominent production features on the 1.5-ha (3.7-ac) site A include a tank battery, an oil-filled trench, pipelines, storage pits for both produced water and oil, and an old power unit. Site activities and historic releases have left open areas in the local oak forest adjacent to these features and a deeply eroded salt scar downslope from the pits that extends to nearby Skiatook Lake. The site is underlain by surficial sediments comprised of very fine-grained eolian sand and colluvium as much as 1.4 m (4.6 ft) thick, which, in turn, overlie flat-lying, fractured bedrock comprised of sandstone, clayey sandstone, mudstone, and shale. A geophysical survey of ground conductance and concentration measurements of aqueous extracts (1:1 by weight) of core samples taken in the salt scar and adjacent areas indicate that unusual concentrations of NaCl-rich salt are present at depths to at least 8 m (26 ft) in the bedrock; however, little salt occurs in the eolian sand. Historic aerial photographs, anecdotal reports from oil-lease operators, and tree-ring records indicate that the surrounding oak forest was largely established after 1935 and thus postdates the majority of surface damage at the site. Blackjack oaks adjacent to the salt scar have anomalously elevated chloride (>400 ppm) in their leaves and record the presence of NaCl-rich salt or salty water in the shallow subsurface. The geophysical measurements also indicate moderately elevated conductance beneath the oak forest adjoining the salt scar. Copyright ?? 2005. The American Association of

  10. Large mid-Holocene and late Pleistocene earthquakes on the Oquirrh fault zone, Utah

    USGS Publications Warehouse

    Olig, S.S.; Lund, W.R.; Black, B.D.

    1994-01-01

    The Oquirrh fault zone is a range-front normal fault that bounds the east side of Tooele Valley and it has long been recognized as a potential source for large earthquakes that pose a significant hazard to population centers along the Wasatch Front in central Utah. Scarps of the Oquirrh fault zone offset the Provo shoreline of Lake Bonneville and previous studies of scarp morphology suggested that the most recent surface-faulting earthquake occurred between 9000 and 13,500 years ago. Based on a potential rupture length of 12 to 21 km from previous mapping, moment magnitude (Mw) estimates for this event range from 6.3 to 6.6 In contrast, our results from detailed mapping and trench excavations at two sites indicate that the most-recent event actually occurred between 4300 and 6900 yr B.P. (4800 and 7900 cal B.P.) and net vertical displacements were 2.2 to 2.7 m, much larger than expected considering estimated rupture lengths for this event. Empirical relations between magnitude and displacement yield Mw 7.0 to 7.2. A few, short discontinuous fault scarps as far south as Stockton, Utah have been identified in a recent mapping investigation and our results suggest that they may be part of the Oquirrh fault zone, increasing the total fault length to 32 km. These results emphasize the importance of integrating stratigraphic and geomorphic information in fault investigations for earthquake hazard evaluations. At both the Big Canyon and Pole Canyon sites, trenches exposed faulted Lake Bonneville sediments and thick wedges of fault-scarp derived colluvium associated with the most-recent event. Bulk sediment samples from a faulted debris-flow deposit at the Big Canyon site yield radiocarbon ages of 7650 ?? 90 yr B.P. and 6840 ?? 100 yr B.P. (all lab errors are ??1??). A bulk sediment sample from unfaulted fluvial deposits that bury the fault scarp yield a radiocarbon age estimate of 4340 ?? 60 yr B.P. Stratigraphic evidence for a pre-Bonneville lake cycle penultimate

  11. Seismic, magnetic, and geotechnical properties of a landslide and clinker deposits, Powder River basin, Wyoming and Montana

    USGS Publications Warehouse

    Miller, C.H.

    1979-01-01

    Exploitation of vast coal and other resources in the Powder River Basin has caused recent, rapid increases in population and in commercial and residential development and has prompted land utilization studies. Two aspects of land utilization were studied for this report: (1) the seismic and geotechnical properties of a landslide and (2) the seismic, magnetic, and geotechnical properties of clinker deposits. (1) The landslide seismic survey revealed two layers in the slide area. The upper (low-velocity) layer is a relatively weak mantle of colluvium and unconsolidated and weathered bedrock that ranges in thickness from 3.0 to 7.5 m and has an average seismic velocity of about 390 m/s. It overlies high-velocity, relatively strong sedimentary bedrock that has velocities greater than about 1330 m/s. The low-velocity layer is also present at the other eight seismic refraction sites in the basin; a similar layer has also been reported in the Soviet Union in a landslide area over similar bedrock. The buried contact of the low- and high-velocity layers is relatively smooth and is nearly parallel with the restored topographic surface. There is no indication that any of the high-velocity layer (bedrock) has been displaced or removed. The seismic data also show that the shear modulus of the low-velocity layer is only about one-tenth that of the high-velocity layer and the shear strength (at failure) is only about one-thirtieth. Much of the slide failure is clearly in the shear mode, and failure is, therefore, concluded to be confined to the low-velocity layer. The major immediate factor contributing to landslide failure is apparently the addition of moisture to the low-velocity layer. The study implies that the low-velocity layer can be defined over some of the basin by seismic surveys and that they can help predict or delineate potential slides. Preventative actions that could then be taken include avoidance, dewatering, prevention of saturation, buttressing the toe, and

  12. Debris Flows and Floods in Southeastern Arizona from Extreme Precipitation in July 2006 - Magnitude, Frequency, and Sediment Delivery

    USGS Publications Warehouse

    Webb, Robert H.; Magirl, Christopher S.; Griffiths, Peter G.; Boyer, Diane E.

    2008-01-01

    fans in the Tucson basin are extremely rare events. Although recent watershed changes - particularly the impacts of recent wildland fires - may be important locally, the record number of slope failures and debris flows were related predominantly to extreme precipitation, not other factors such as fire history. The large number of slope failures and debris flows in an area with few such occurrences historically underscores the rarity of this type of meteorological event in southeastern Arizona. Most slope failures appeared to be shallow-seated slope failures of colluvium on steep slopes that caused deep scour of chutes and substantial aggradation of channels downstream. In the southern Santa Catalina Mountains, we estimate that 1.5 million tons of sediment were released from slope failures into the channels of ten drainage basins. Thirty-six percent of this sediment (527,000 tons) is gravel-sized or smaller and is likely to be transported by streamflow out of the mountain drainages and into the drainage network of metropolitan Tucson. This sediment poses a potential flood hazard by reducing conveyance in fixed-section flood control structures along Rillito Creek and its major tributaries, although our estimates suggest that deposition may be small if it is distributed widely along the channel, which is expected. Using the stochastic debris-flow model LAHARZ, we simulated debris-flow transport from slope failures to the apices of alluvial fans flanking the southern Santa Catalina Mountains. Despite considerable uncertainty in applying coefficients developed from worldwide observations to conditions in the southern Santa Catalina Mountains, we predicted the approximate area of depositional zones for several 2006 debris flows, particularly for Soldier Canyon. Better results could be achieved in some canyons if sediment budgets could be developed to account for alternating transport and deposition zones in channels with abrupt expansions and contractions, such

  13. Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 17. Geomorphology of the Red River Valley, Taos County, New Mexico, and Influence on Ground-Water Flow in the Shallow Alluvial Aquifer

    USGS Publications Warehouse

    Vincent, Kirk R.

    2008-01-01

    where erosion-resistant bedrock, which tends to form vertical cliffs, restricts the width of the valley bottom. Although the presence of a shallow bedrock sill, overlain by shallow alluvium, is a plausible cause of ground-water emergence, this cause was not demonstrated in the study area. The water-table gradient can locally decrease in the downstream direction because of changes in the hydraulic properties of the alluvium, and this may be a contributing cause of ground-water emergence. However, at one site (near Cabin Springs), ground-water emergence could not be explained by spatial changes in geometric or hydraulic properties of the aquifer. Furthermore, the available evidence demonstrates that ground water flowing through bedrock fractures or colluvium entered the north side of the alluvial aquifer, and is the cause of ground-water emergence. At that location the alluvial aquifer was already flowing full, causing the excess water to emerge into the stream. An indirect consequence of altered rock in the tributary watersheds is the rapid erosion rate of alteration scars combined with the hydraulic properties of sediments shed from those scars. Where alteration scars are large the debris fans at the mouths of the tributary watersheds substantially encroach into the Red River Valley. At such locations debris-fan materials dominate the width and thickness of the alluvium in the valley and reduce the rate of flow of ground water within the Red River alluvial aquifer. Most sites of groundwater emergence are located immediately upstream from or along the margins of debris fans. A substantial fraction of the ground water approaching a debris fan can emerge to become streamflow. This last observation has three implications. First, very little water can flow the entire length of the study area entirely within the alluvial aquifer because the ground water repeatedly contacts debris-fan sediments over that length. Second, it follows that emerging water containing

  14. Submarine landslides in the Santa Barbara Channel as potential tsunami sources

    NASA Astrophysics Data System (ADS)

    Greene, H. G.; Murai, L. Y.; Watts, P.; Maher, N. A.; Fisher, M. A.; Paull, C. E.; Eichhubl, P.

    2006-01-01

    distinct narrow scar extends from near the eastern head wall of this slide for over 2km eastward toward the Goleta slide and may represent either an incipient failure or a remnant of a previous failure. Push cores collected within the main head scar of this slide consisted of hydrogen sulfide bearing mud, possibly suggesting active fluid seepage and a vibra-core penetrated ~50 cm of recent sediment overlying colluvium or landslide debris confirming the age of ~300 years as proposed by Lee et al. (2004). However, no seeps or indications of recent movement were observed during our ROV investigation within this narrow head scar indicating that seafloor in the scar is draped with mud.

  15. Fused breccia in Middle Miocene ignimbrites and other deterministic constraints on timing of faulting in Midway Valley, Nevada

    NASA Astrophysics Data System (ADS)

    Buesch, D.

    2011-12-01

    are consistent with deposition on an irregular faulted terrain. Some post-Tmr faulting might have occurred, but it is not constrained by late Miocene events. The Miocene rocks and faults were eroded to a low-relief surface documented in 94 boreholes in Midway Valley. Based on U-Pb geochronologic techniques on pedogenic opal deposits in the post-Miocene valley-filling deposits, the minimum age of the basal colluvium and alluvium is 2.7 Ma to 1.6 Ma with an average of 1.9 Ma (Neymark and others, 2007, GSA abstracts); and parts of the basal alluvium are constrained between 7.3 Ma and 3.2 Ma (Neymark and others, 2010, GSA abstracts). These relations indicate that (1) faulting was active in the hanging wall of the Paintbrush Canyon fault during the mid-Miocene, (2) faulting ceased throughout Midway Valley by the late Pliocene to earliest Pleistocene, and (3) fault activity migrated to the block-bounding Bow Ridge and Paintbrush Canyon faults. Thus, depositional, geochemical, and geochronologic studies, combined with an understanding of mechanical processes by which rocks form and are fractured, provides deterministic bounds on the timing and locations of faulting and resolve the likelihood of future events.

  16. Deterministic Approach for Estimating Critical Rainfall Threshold of Rainfall-induced Landslide in Taiwan

    NASA Astrophysics Data System (ADS)

    Chung, Ming-Chien; Tan, Chih-Hao; Chen, Mien-Min; Su, Tai-Wei

    2013-04-01

    Taiwan is an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin. The inherent complexities of geological nature create numerous discontinuities through rock masses and relatively steep hillside on the island. In recent years, the increase in the frequency and intensity of extreme natural events due to global warming or climate change brought significant landslides. The causes of landslides in these slopes are attributed to a number of factors. As is well known, rainfall is one of the most significant triggering factors for landslide occurrence. In general, the rainfall infiltration results in changing the suction and the moisture of soil, raising the unit weight of soil, and reducing the shear strength of soil in the colluvium of landslide. The stability of landslide is closely related to the groundwater pressure in response to rainfall infiltration, the geological and topographical conditions, and the physical and mechanical parameters. To assess the potential susceptibility to landslide, an effective modeling of rainfall-induced landslide is essential. In this paper, a deterministic approach is adopted to estimate the critical rainfall threshold of the rainfall-induced landslide. The critical rainfall threshold is defined as the accumulated rainfall while the safety factor of the slope is equal to 1.0. First, the process of deterministic approach establishes the hydrogeological conceptual model of the slope based on a series of in-situ investigations, including geological drilling, surface geological investigation, geophysical investigation, and borehole explorations. The material strength and hydraulic properties of the model were given by the field and laboratory tests. Second, the hydraulic and mechanical parameters of the model are calibrated with the long-term monitoring data. Furthermore, a two-dimensional numerical program, GeoStudio, was employed to perform the modelling practice. Finally

  17. Submarine landslides in the Santa Barbara Channel as potential tsunami sources

    USGS Publications Warehouse

    Greene, H. Gary; Murai, L.Y.; Watts, P.; Maher, N.A.; Fisher, M.A.; Paull, C.E.; Eichhubl, P.

    2006-01-01

    distinct narrow scar extends from near the eastern head wall of this slide for over 2 km eastward toward the Goleta slide and may represent either an incipient failure or a remnant of a previous failure. Push cores collected within the main head scar of this slide consisted of hydrogen sulfide bearing mud, possibly suggesting active fluid seepage and a vibra-core penetrated ???50 cm of recent sediment overlying colluvium or landslide debris confirming the age of ???300 years as proposed by Lee et al. (2004). However, no seeps or indications of recent movement were observed during our ROV investigation within this narrow head scar indicating that seafloor in the scar is draped with mud. ?? 2006 Author(s). This work is licensed under a Creative Commons License.

  18. Hydrogeology of, and simulation of ground-water flow in a mantled carbonate-rock system, Cumberland Valley, Pennsylvania

    USGS Publications Warehouse

    Chichester, D.C.

    1996-01-01

    The U.S. Geological Survey conducted a study in a highly productive and complex regolith-mantled carbonate valley in the northeastern part of the Cumberland Valley, Pa., as part of its Appalachian Valleys and Piedmont Regional Aquifer-system Analysis program. The study was designed to quantify the hydrogeologic characteristics and understand the ground-water flow system of a highly productive and complex thickly mantled carbonate valley. The Cumberland Valley is characterized by complexly folded and faulted carbonate bedrock in the valley bottom, by shale and graywacke to the north, and by red-sedimentary and diabase rocks in the east-southeast. Near the southern valley hillslope, the carbonate rock is overlain by wedge-shaped deposit of regolith, up to 450 feet thick, that is composed of residual material, alluvium, and colluvium. Locally, saturated regolith is greater than 200 feet thick. Seepage-run data indicate that stream reaches, near valley walls, are losing water from the stream, through the regolith, to the ground-water system. Results of hydrograph-separation analyses indicate that base flow in stream basins dominated by regolith-mantled carbonate rock, carbonate rock, and carbonate rock and shale are 81.6, 93.0, and 67.7 percent of total streamflow, respectively. The relative high percentage for the regolith-mantled carbonate-rock basin indicates that the regolith stores precipitation and slowly, steadily releases this water to the carbonate-rock aquifer and to streams as base flow. Anomalies in water-table gradients and configuration are a result of topography and differences in the character and distribution of overburden material, permeability, rock type, and geologic structure. Most ground-water flow is local, and ground water discharges to nearby springs and streams. Regional flow is northeastward to the Susquehanna River. Average-annual water budgets were calculated for the period of record from two continuous streamflow-gaging stations. Average

  19. Geologic map of the Hogback Mountain quadrangle, Lewis and Clark and Meagher Counties, Montana

    USGS Publications Warehouse

    Reynolds, Mitchell W.

    2003-01-01

    The geologic map of the Hogback Mountain quadrangle, scale 1:24,000, was made as part of the Montana Investigations Project to provide new information on the stratigraphy, structure, and geologic history of an area in the geologically complex southern part of the Montana disturbed belt. In the Hogback Mountain area, rocks ranging in age from Middle Proterozoic through Cretaceous are strongly folded within and under thrust plates of equivalent rocks. Continental rocks of successive thrust plates have been telescoped eastward over a buttress of the stable continent. Erosional remnants of Oligocene andesitic basalt lie on highest surfaces eroded across the strongly deformed older rocks; younger erosion has dissected the terrain deeply, producing Late Tertiary and Quaternary deposits of alluvium, colluvium, and local landslide debris in the valleys and canyons. Different stratigraphic successions are exposed at different structural levels across the quadrangle. In the northeastern part of the quadrangle at the lowest structural level, rocks of the Upper Mississippian Big Snowy Group, including the Kibbey Formation and the undivided Otter and Heath Formations, the overlying Pennsylvanian Amsden and undivided Quadrant and Phosphoria Formations, the Ellis Group, and the Kootenai Formation, are folded and broken by thrust faults. The next higher structural level, the Avalanche Butte thrust plate, exposes strongly folded and, in places, attenuated strata of Cambrian (Flathead Sandstone, Wolsey Shale, Meagher Limestone, and undivided Pilgrim Formation and Park Shale), Devonian (Maywood Formation, Jefferson Formation, and most of the Three Forks Formation), and Mississippian (uppermost part of the Three Forks Formation and Lodgepole and Mission Canyon Limestones) ages. The overlying Hogback Mountain thrust plate contains strongly folded rocks ranging in age from the Middle Proterozoic Greyson Formation to the Upper and Lower Mississippian Mission Canyon Limestone and

  20. Investigating controls on debris-flow initiation and surge frequency at Chalk Cliffs, USA: initial results from monitoring and modeling

    NASA Astrophysics Data System (ADS)

    Kean, J. W.; McCoy, S. W.; Tucker, G. E.; Staley, D. M.; Coe, J. A.

    2012-04-01

    Recent monitoring of a small (0.3 km2) bedrock-dominated catchment in central Colorado, USA, has revealed distinct differences in debris-flow surge dynamics relative to rainfall intensity. Moderate bursts of rainfall (15-40 mm/hr) typically trigger a set of coarse-grained surges with depths that can exceed 1.0 m. High-intensity bursts of rainfall (40-150 mm/hr), in contrast, often generate only a single moderate-amplitude coarse-grained surge (> 0.5 m depth), followed by several minutes of water-rich flow having comparable or greater peak depth. In both cases, debris flows are observed within minutes of rain bursts due to the rapid concentration of runoff from bedrock cliffs to channels loaded with sediment from dry ravel and rockfall. Video observations have shown that the runoff can initiate debris flows both at a steep (~40 degree) bedrock-colluvium interface, and in a lower gradient (~15 degree) section of channel. This latter style of initiation, which has only been observed at moderate rainfall intensity, involves the formation and failure of a highly porous sediment dam created by bedload transport. We speculate that this process may be responsible for the creation of the consistent surge patterns we observe with moderate intensity rainfall, and may explain the relative lack of granular surges with high-intensity rainfall. To investigate this possibility, we have developed a simple one-dimensional morphodynamic model of the formation and failure of sediment dams in an undulating bedrock channel filled with loose bed sediment. The model consists of a coupled surface-subsurface water flow model, which is used to drive bed-sediment topographic adjustments based on the mathematical divergence of the sediment transport rate. Under certain topographic and water-flow conditions, the shear stress in a section of the channel can fall below the critical shear stress, resulting in local deposition of sediment. Consistent with field observations, the modeled deposit

  1. Controls of catchments` sub-storage contributions to dynamic water quality patterns in the stream network

    NASA Astrophysics Data System (ADS)

    Schuetz, Tobias; Maike Hegenauer, Anja

    2016-04-01

    Water quality is usually observed either continuously at a few stations within a catchment or with few snapshot sampling campaigns throughout the whole stream network. Although we know that the depletion of catchment sub-storages can vary throughout the stream network according to their actual water content (spatial variability of actual storage conditions can be caused amongst others by unevenly distributed rainfall, storage size or spatial differences in soil characteristics and land use), we know little about the impact of this process on spatial water quality patterns. For summer low flow recession periods, when stream water composition can be crucial for aquatic ecosystem conditions and the exceedance of water quality thresholds, knowledge on the controls of the dynamic interplay of catchment storages and stream water composition might improve water quality management and the implementation of corresponding mitigation measures. We studied this process throughout the stream network of a first-order agricultural headwater catchment in south-western Germany during two summer low flow recession periods. The underlying geology of the study area is a deep layer of aeolian loess, whilst the dominating soil is a silty calcaric regosol with gleizations in the colluvium. The land use in the catchment is dominated by viniculture (63 %) and arable crops (18 %). Due to the dense drainpipe network within the catchment we could identify 12 sub-catchments contributing during summer low flow recession periods to total stream discharge. We continuously observed discharge, electrical conductivity and water temperatures for 8 of the sub-catchments and at the catchment outlet. This data set was accomplished by 10 snapshot campaigns where we sampled for water temperatures, electrical conductivity, major ions, pH and O2 throughout the stream network. Using either discharge concentration relationships or time dependent functions, we derived continuous export rates for all measures in

  2. Holocene vegetation, fire and erosional history of City of Rocks National Reserve, South-Central Idaho

    NASA Astrophysics Data System (ADS)

    Weppner, K.; Pierce, J. L.; Betancourt, J. L.

    2011-12-01

    dominant tree species at CIRO. Field observation indicates that sheetflooding is a dominant erosional process at CIRO with sheetflood deposits accounting for ~40% of total measured Holocene alluvial thickness. Only ~20% of this deposition occurred between ~7-2 ka, suggesting a prolonged period of minimal erosion. Furthermore, during this ~5 ka interval, ~60% of alluvium was deposited as sheetfloods with the remainder deposited as overbank and flood deposits, and no recorded debris flows. We hypothesize that during the drier, warmer and possibly more stable climate of the mid-Holocene, decreased vegetation density on hillslopes suppressed colluvial storage, thus limiting the supply of hillslope material for debris flow production. Hillslopes likely experienced more frequent, yet low-volume, sheetflood erosion. Between ~4-2 ka cal yr BP, cooler and wetter conditions returned, as indicated by midden records from central Idaho. After ~2.2 ka, soil horizon development suggests that increased vegetation density re-stabilized hillslopes. This accumulated colluvium supplied material for episodic, post-wildfire debris flow events.

  3. The landslide inventory as the basis of susceptibility and hazard assessment

    NASA Astrophysics Data System (ADS)

    Copons, Ramon; Linares, Rogelio; Cirés, Jordi; Tallada, Anna

    2010-05-01

    40km2 in Tremp (Catalan Pyrenees). The selected area is dominated by a large synclinorium and two main lythologies can be considered inside: (i) the "Garum" Formation composed by plastic clays susceptible to instability, (ii) and a calcareous rock forming rockcliffs faces from ten to hundred meters high where primary rockfalls occurs. Several types of landslides are present in Tremp: rockfalls, topples, slides, earth flows, large lateral spreads and slow earth flows in a large part of slopes. Older events dated reveal an active instability over the Pleistocene with main reactivations during the glacial periods. Nowadays, small landslides affect the superficial colluvium are present during large rainfall periods. These characteristics reveal Tremp like a complex area affected highly by landslides. Two qualified field geologists from different institutions have created two different landslide inventories at a scale 1:10.000 over the same area in Tremp. One of the inventories, which is created by an earth scientist experienced in geormorphological techniques, represents the pessimistic interpretation considering large instabilities affecting large parts of the slope. The other inventory, which is created by a professional geologist experienced in landslide mapping, considers a more optimistic interpretation of the landslides identified. Commonly, parameters considered are the morphology of terrain surface, the lithology of rock outcrops and quaternary deposits, presence of damaged vegetation, and structural patterns. Data has been obtained by using air photographs and field observations. Inventory maps have been compared in order to contrast the existing differences and to detect limitations. Usually, both inventories represent the same large events despite their boundaries can be particulars. However, smaller events mapped are sometimes different on both inventories. Results obtained allow us to contrast the use of parameters considered during the completion of

  4. Stratigraphy of Slick Rock district and vicinity, San Miguel and Dolores Counties, Colorado

    USGS Publications Warehouse

    Shawe, Daniel R.; Simmons, George C.; Archbold, Norbert L.

    1968-01-01

    , siltstone, and conglomerate, of late Paleozoic and Mesozoic age. Above these rocks is as much as 2,300 feet of marine shale of late Mesozoic age. Perhaps about 5,000 feet of clastic sedimentary rocks, dominantly sandstone and in part shale, of late Mesozoic and early Cenozoic age, overlay the older rocks of the district prior to late Cenozoic erosion...Outside the Slick Rock district the Mancos Shale is overlain by dominantly terrestrial sandstone, mudstone, and coaly beds of the Mesaverde Group of Late Cretaceous age, and younger units such as the Wasatch and Green River Formations of Tertiary age, which once may have extended across the district. These units, totaling possibly 5,000 feet in thickness, were removed by erosion following middle Tertiary uplift of the Colorado Plateau.Igneous rocks of Tertiary age crop out in only one small area in the district, but they are intruded extensively in the Mancos Shale east of the district, and, as shown by deep oil test wells, appear to be intruded widely in the Paradox Member of the Hermosa Formation in the southern part of the district and southeast of the district. Andesite porphyry occurs in a dike on Glade Mountain, microgranogabbro and microgranodiorite occur in thin sills east of the district, and rocks of similar composition form thick sills in the subsurface. All are similar chemically to igneous rocks in the San Juan Mountains southeast of the district and probably were the result of a specific igneous episode. They were intruded most likely during the Miocene.Surficial deposits of Quaternary age include glacial till, terrace gravels, alluvial fans, landslide debris, loess, other soil, alluvium, colluvium, and talus. On Glade Mountain, glacial till of probable early Pleistocene age merges westward with terrace gravels that are correlative with terrace gravels which lie on an old weathered surface of Mancos Shale farther west on the rim of the Dolores River Canyon.

  5. Slope Deposits and (Paleo)Soils as Geoarchives to Reconstruct Late Quaternary Environments of Southern Africa

    NASA Astrophysics Data System (ADS)

    Huerkamp, K.; Voelkel, J.; Heine, K.; Bens, O.

    2009-04-01

    Although it is clear that large, rapid temperature changes have occurred during the last glacial-interglacial cycle and the Holocene in southern Africa, we have only limited, and often imprecise, knowledge of how the major moisture-bearing atmospheric circulation systems have reacted to these changes. Using slope deposits and soils as palaeoclimatic geoarchives we will overcome these constraints. The role of many geoarchives in the reconstruction of the Quaternary climate in southern Africa remains controversial, since the paleoclimate data are based on evidence from marine cores, lake sediments, speleothems and spring sinter, fluvial sediments, aeolian sands and dust, colluvium, and coastal sediments. To elucidate climate controls on Quaternary landscape evolution and to use these data for palaeoclimatic reconstructions, thus far slope deposits and soils have been investigated. Climatic controls on these cycles are incompletely known. The availability of results from earlier fieldwork, micromorphology, Optical Stimulated Luminescence (OSL), 14C dating and stable carbon isotope analysis will permit a thorough assessment of slope deposits and soils in terms of their palaeoenvironmental potential. The knowledge of suitable areas and sites in different climatic zones of southern Africa where slope deposits and soils have already been found document the late Quaternary climatic history and even climatic anomalies (e.g. Younger Dryas period at Eksteenfontein, 8.2 ka event at Tsumkwe, 4 ka event in the Auob valley, Little Ice Age in the Namib Desert). The findings will show the late Quaternary history of precipitation fluctuations, of the shifting of the ITCZ (and the ABF - Agulhas-Benguela Front), of wind intensities and directions, and of extreme precipitation events. The project will employ state-of-the-art geoscience methodology to interpret the record of precipitation changes of the late Quaternary, including the shifting of the summer and winter rain belts, the

  6. Aquifer-test results, direction of ground-water flow, and 1984-90 annual ground-water pumpage for irrigation, lower Big Lost River Valley, Idaho

    USGS Publications Warehouse

    Bassick, M.D.; Jones, M.L.

    1992-01-01

    The study area (see index map of Idaho), part of the Big Lost River drainage basin, is at the northern side of the eastern Snake River Plain. The lower Big Lost River Valley extends from the confluence of Antelope Creek and the Big Lost River to about 4 mi south of Arco and encompasses about 145 mi2 (see map showing water-level contours). The study area is about 18 mi long and, at its narrowest, 4 mi wide. Arco, Butte City, and Moore, with populations of 1,016, 59, and 190, respectively, in 1990, are the only incorporated towns. The entire study area, except the extreme northwestern part, is in Butte City. The study area boundary is where alluvium and colluvium pinch out and abut against the White Knob Mountains (chiefly undifferentiated sedimentary rock with lesser amounts of volcanic rock) on the west and the Lost River Range (chiefly sedimentary rock) on the east. Gravel and sand in the valley fill compose the main aquifer. The southern boundary is approximately where Big Lost River valley fill intercalates with or abuts against basalt of the Snake River Group. Spring ground-water levels and flow in the Big Lost River depend primarily on temperature and the amount and timing of precipitation within the entire drainage basin. Periods of abundant water supply and water shortages are, therefore, related to the amount of annual precipitation. Surface reservoir capacity in the valley (Mackay Reservoir, about 20 mi northwest of Moore) is only 20 percent of the average annual flow of the Big Lost River (Crosthwaite and others, 1970, p. 3). Stored surface water is generally unavailable for carryover from years of abundant water supply to help relieve drought conditions in subsequent years. Many farmers have drilled irrigation wells to supplement surface-water supplies and to increase irrigated acreage. Average annual flow of the Big Lost River below Mackay Reservoir near Mackay (gaging station 13127000, not shown) in water years 1905, 1913-14, and 1920-90 was about 224

  7. Tracing the contribution of debris flow-dominated channels to gravel-bed torrential river channel: implementing pit-tags in the upper Guil River (French Alps)

    NASA Astrophysics Data System (ADS)

    Arnaud-Fassetta, Gilles; Lissak, Candide; Fort, Monique; Bétard, François; Carlier, Benoit; Cossart, Etienne; Madelin, Malika; Viel, Vincent; Charnay, Bérengère; Bletterie, Xavier

    2014-05-01

    In the upper, wider reaches of Alpine valleys, shaping of active channels is usually subject to rapid change. It mostly depends upon hydro-climatic variability, runoff concentration and sediment supply, and may result in alternating sequences of fluvial and debris-flow pulses, as recorded in alluvial fans and terraces. Our study, carried in the frame of SAMCO (ANR) project, focuses on the upper Guil River Valley (Queyras, Southern French Alps) cut into the slaty shale "schistes lustrés". Steep, lower order drains carry a contrasted solid discharge, including predominantly sandy-loam particles mixed with gravels and boulders (sandstone schists, ophiolites). Abundant sediment supply by frost shattering, snow avalanche and landslides is then reworked during snowmelt or summer storm runoff events, and may result in catastrophic, very destructive floods along the main channel, as shown by historical records. Following the RI-30 year 2000 flood, our investigations included sediment budgets, i.e. balance of erosion and deposition, and the mapping of the source, transport and storage of various sediments (talus, colluvium, torrential fans, terraces). To better assess sediment fluxes and sediment delivery into the main channel network, we implemented tracers (pit-tags) in selected sub-catchments, significantly contributing to the sediment yield of the valley bottoms during the floods and/or avalanches: Maloqueste, Combe Morel, Bouchouse and Peyronnelle catchments. The first three are direct tributaries of the Guil River whereas the Peyronnelle is a left bank tributary of the Peynin River, which joins the Guil River via an alluvial cone with high human and material stakes. The Maloqueste and the Combe Morel are two tributaries facing each other in the Guil valley, representing a double lateral constraint for the road during flood events of the Guil River. After pit-tag initialisation in laboratory, we set them up along the four tributaries: Maloqueste (20 pit-tags), Combe

  8. Sedimentary facies and depositional environments of early Mesozoic Newark Supergroup basins, eastern North America

    USGS Publications Warehouse

    Smoot, J.P.

    1991-01-01

    The early Mesozoic Newark Supergroup consists of continental sedimentary rocks and basalt flows that occupy a NE-trending belt of elongate basins exposed in eastern North America. The basins were filled over a period of 30-40 m.y. spanning the Late Triassic to Early Jurassic, prior to the opening of the north Atlantic Ocean. The sedimentary rocks are here divided into four principal lithofacies. The alluvial-fan facies includes deposits dominated by: (1) debris flows; (2) shallow braided streams; (3) deeper braided streams (with trough crossbeds); or (4) intense bioturbation or hyperconcentrated flows (tabular, unstratified muddy sandstone). The fluvial facies include deposits of: (1) shallow, ephemeral braided streams; (2) deeper, flashflooding, braided streams (with poor sorting and crossbeds); (3) perennial braided rivers; (4) meandering rivers; (5) meandering streams (with high suspended loads); (6) overbank areas or local flood-plain lakes; or (7) local streams and/or colluvium. The lacustrine facies includes deposits of: (1) deep perennial lakes; (2) shallow perennial lakes; (3) shallow ephemeral lakes; (4) playa dry mudflats; (5) salt-encrusted saline mudflats; or (6) vegetated mudflats. The lake margin clastic facies includes deposits of: (1) birdfoot deltas; (2) stacked Gilbert-type deltas; (3) sheet deltas; (4) wave-reworked alluvial fans; or (5) wave-sorted sand sheets. Coal deposits are present in the lake margin clastic and the lacustrine facies of Carnian age (Late Triassic) only in basins of south-central Virginia and North and South Carolina. Eolian deposits are known only from the basins in Nova Scotia and Connecticut. Evaporites (and their pseudomorphs) occur mainly in the northern basins as deposits of saline soils and less commonly of saline lakes, and some evaporite and alkaline minerals present in the Mesozoic rocks may be a result of later diagenesis. These relationships suggest climatic variations across paleolatitudes, more humid to the

  9. Hydrology of the Helena area bedrock, west-central Montana, 1993-98; with a section on geologic setting and a generalized bedrock geologic map

    USGS Publications Warehouse

    Thamke, Joanna N.; Reynolds, Mitchell W.

    2000-01-01

    The Generalized Bedrock Geologic Map of the Helena Area, West-Central Montana (plate 1 in the report) provides an intermediate-scale overview of bedrock in the Helena area. The geologic map has been compiled at a scale of 1:100,000 from the most widely available sources of geologic map information (see index to geologic mapping on pl. 1). That information has been updated by M.W. Reynolds for this report with more recent geologic mapping and field revision of published maps. All well locations and all bedrock units penetrated during drilling have been confirmed on geologic maps at the largest scale available. Source geologic maps are all at scales larger than 1:100,000 scale. Care has been taken to ensure accurate representation of the original geology at the compilation scale. However, positional accuracy of some features might be somewhat diminished at the smaller scale of the base map when compared with the original data source. Also, line thicknesses for contacts and faults necessarily assume a greater width, relative to the real geologic feature, at the scale of the generalized map than on any original map. The map is not intended for large-scale, site-specific detailed planning. Bedrock units throughout the Helena area are generally covered by young surficial deposits such as alluvium, colluvium, glacial debris, or windblown sediment. Thickness of such deposits varies from veneers through which the underlying bedrock is clearly discernible to major thicknesses that conceal all underlying bedrock and structure. Boundaries of major accumulations of surficial deposits are attributed separately from bedrock contacts. These boundaries should not be considered precise at the map scale or at larger scales. Boundaries shown may be less accurate positionally than bedrock contacts and faults because (1) surficial deposits commonly thin to a knife edge; (2) different mappers will interpret the edge differently when drawing a boundary; or (3) the original geologic map

  10. Surficial Geologic Mapping Using Digital Techniques Reveals Late-Phase Basin Evolution and Role of Paleoclimate, Death Valley Junction 30' × 60' Quadrangle, California and Nevada

    NASA Astrophysics Data System (ADS)

    Slate, J.; Berry, M.; Menges, C. M.

    2010-12-01

    The recently released surficial geologic map of the Death Valley Junction 30' x 60' quadrangle at 1:100,000 scale (USGS SIM 3013) was simultaneously mapped and compiled using digital photogrammetric methods. The map area covers the central part of Death Valley and adjacent mountain ranges—the Panamint Range on the west and the Funeral Mountains on the east—as well as areas east of Death Valley including some of the Amargosa Desert, the Spring Mountains, and Pahrump Valley. We mapped six alluvial units, an eolian unit, three playa or playa-related units, lacustrine beach deposits, colluvium, and marl. Interpretation of surface morphology, tone, relative height, and map pattern in air photos enabled us to differentiate among the alluvial units, which make up about 80 percent of the surficial deposits in the map area. Systematic variations in alluvial surface morphology with age permit us to map and correlate geomorphic surfaces. Surface morphology is a product of depositional and post-depositional processes. Lithologic variations across the map area influence the tone of the alluvial units. Although young alluvial units are often light-toned due to an absence or paucity of rock varnish, they may appear dark where the source rocks are dark. Lithology also influences the development of rock varnish; fine-grained or aphanitic rocks, such as quartzite or basalt, tend to become varnished more quickly than rocks such as limestone or granite. Granite commonly disaggregates to grus before becoming varnished and limestone becomes etched. Relative height (topographic position) is useful for mapping in individual drainage basins near range fronts, but basinward, especially in tectonically inactive areas, most surfaces grade to the same base level, and relative height differs little among the alluvial units. Faulting, both the magnitude and location, also affects the map pattern of alluvial units. As faulting uplifts ranges relative to the basins, streams adjust to new base

  11. Aspect-Driven Changes in Slope Stability Due to Ecohydrologic Feedbacks

    NASA Astrophysics Data System (ADS)

    Poulos, M. J.; Pierce, J. L.; Flores, A. N.; Benner, S. G.; Smith, T. J.; McNamara, J. P.

    2009-12-01

    Seasonally integrated variation in insolation drives feedbacks among evapotranspiration, soil moisture, weathering, and erosion that lead to pronounced contrasts in slope angles and vegetation on north and south-facing hillslopes. Spatial variations in insolation associated with north-south contrasts in topographic aspect leads to corresponding variation in local microclimates and ecohydrologic regimes that, in turn, impact spatial patterns of weathering and erosion, ultimately impacting slope angles on north and south-facing slopes. Aspect-sensitive environments appear to be poised on a balance point between ecohydrologic systems, and may be especially susceptible to climate change. In the semi-arid Colorado Plateau of northeastern Arizona, cliffs often form on south-facing slopes where soil moisture is insufficient for weathering of clay-cemented sandstone that is susceptible to hydration. In contrast, cliffs are rare on northerly slopes, which are dominated by mantles of weathered sandstone and colluvium (Burnett et al., 2008, doi:10.1029/2007JF000789). However, in semi-arid regions of the Idaho Batholith, preliminary results indicate some north-facing slopes are significantly steeper than south-facing slopes. We hypothesize that in semi-arid areas with observable increases in vegetation on north vs. south-facing slopes, north-facing slopes will be steeper due to increased soil cohesion, increased capture of wind-borne loess due to vegetative wind-baffling, and differences in the type and magnitude of erosive processes. In moister areas where aspect does not visibly control vegetation type and density, differences in slope angles with aspect should not be observed. We investigate tectonically quiescent regions of the mostly-homogenous granodioritic Idaho Batholith to locate areas sensitive to aspect-induced variations in insolation and compare slope characteristics on north and south-facing slopes. Hillslopes within the Dry Creek Experimental Watershed, in the

  12. Earthquakes in Barcelonnette (western French Alps, 2003-2015): where are the faults?

    NASA Astrophysics Data System (ADS)

    Palis, Edouard; Larroque, Christophe; Lebourg, Thomas; Jomard, Hervé; Flamand, Aurélie; Courboulex, Françoise; Vidal, Maurin; Robert, Pierre-Louis

    2016-04-01

    surrounding summits. The slope displays creeping landforms developed during the late glacial period and the little ice age, overlying upper-cretaceous deposits (calcareous sandstone, so-called "flyschs à Helminthoides"). A 2150m-long Electrical Resistivity Tomography Profile was performed to image the first hundreds meters depth. To do so, we used 4 electrical lines of 72 electrodes (10m spacing). We did the acquisitions using 2 array types: dipole-dipole and pole-dipole. Both arrays are sensitive to vertical structures and are well suitable for faults detection at depth. Our objective is to detect if faults extends through the epicentral area and if faults scarps, possibly resulting of a postglacial activity are hidden by the recent periglacial deposits and colluviums. From a preliminary analysis, the ERT imagery of the shallow 200m help us to identify: (1) the geometry of the surficial glacial and periglacial deposits (0-20m thick), (2) the folded calcareous sandstone characterized by a shallow resistive area (100m thick) and a deep resistive area (more than 150m thick), and (3) weaker vertical structures cutting the flyschs substratum that we interpreted as a fractured zone.

  13. Landslide overview map of the conterminous United States

    USGS Publications Warehouse

    Radbruch-Hall, Dorothy H.; Colton, Roger B.; Davies, William E.; Lucchitta, Ivo; Skipp, Betty A.; Varnes, David J.

    1982-01-01

    The accompanying landslide overview map of the conterminous United States is one of a series of National Environmental Overview Maps that summarize geologic, hydrogeologic, and topographic data essential to the assessment of national environmental problems. The map delineates areas where large numbers of landslides exist and areas which are susceptible to landsliding. It was prepared by evaluating the geologic map of the United States and classifying the geologic units according to high, medium, or low landslide incidence (number) and high, medium, or low susceptibility to landsliding. Rock types, structures, topography, precipitation, landslide type, and landslide incidence are mentioned for each physical subdivision of the United States. The differences in slope stability between the Colorado Plateau, the Appalachian Highlands, the Coast Ranges of California, and the Southern Rocky Mountains are compared in detail, to illustrate the influence of various natural factors on the types of landsliding that occur in regions having different physical conditions. These four mountainous regions are among the most landslide-prone areas in the United States. The Colorado Plateau is a deformed platform where interbedded sedimentary rocks of varied lithologic properties have been gently warped and deeply eroded. The rocks are extensively fractured. Regional fracture systems, joints associated with individual geologic structures, and joints parallel to topographic surfaces, such as cliff faces, greatly influence slope stability. Detached blocks at the edges of mesas, as well as columns, arched recesses, and many natural arches on the Colorado Plateau, were formed wholly or in part by mass movement. In the Appalachian Highlands, earth flows, debris flows, and debris avalanches predominate in weathered bedrock and colluvium. Damaging debris avalanches result when persistent steady rainfall is followed by a sudden heavy downpour. Landsliding in unweathered bedrock is controlled

  14. Preliminary Geologic Map of the White Sulphur Springs 30' x 60' Quadrangle, Montana

    USGS Publications Warehouse

    Reynolds, Mitchell W.; Brandt, Theodore R.

    2006-01-01

    -Tertiary sediments rest across the older Cenozoic deposits and across all older rocks. The Quaternary and Quaternary-Tertiary deposits generally are gravels that mantle broad erosional surfaces on the flanks of the mountains, gravels in stream channels, and colluvium and landslide deposits on hill sides. Glacial deposits, representing at least two stages of glaciation, are present in the northern part of the Little Belt Mountains. The geologic structure of much of the northwest part of the quadrangle is a broad uplift, in the core of which the Paleoproterozoic and Neoarchean metamorphic rocks are exposed. Down plunge to the east, the succession of Phanerozoic sedimentary rocks define an east-trending arch, cored locally by Mesoproterozoic strata of the Belt Supergroup. The north flank of the arch dips steeply north as a monocline. Stratigraphic relations among Mississippian, Pennsylvanian, and Jurassic strata document the recurrent uplift and erosion on that north flank. The broader arch of the Little Belt Mountains reflects the west plunge of the ancestral Central Montana uplift. The eastern extension of the Lewis and Clark tectonic zone is exposed in the southern half of the quadrangle where the Volcano Valley fault zone curves from west to southeast as a reverse fault along which the latest movement is up on the south side. The fault zone ends in an anticline in the south-central margin of the quadrangle. Stratigraphic overlap of Phanerozoic strata over the truncated edges of Mesoproterozoic units documents that the area of the eastern terminus of the fault zone was tectonically recurrently active. Northeast trending strike-slip faults displace Mesoproterozoic rocks in the northwest and south-central parts of the quadrangle. Several of those faults are overlain unconformably by the Middle Cambrian Flathead Sandstone. Other north-east and west-trending faults across the central part of the quadrangle are intruded by middle Eocene plutons. You

  15. Hydrogeology of the West Branch Delaware River basin, Delaware County, New York

    USGS Publications Warehouse

    Reynolds, Richard J.

    2013-01-01

    In 2009, the U.S. Geological Survey, in cooperation with the New York State Department of Environmental Conservation, began a study of the hydrogeology of the West Branch Delaware River (Cannonsville Reservoir) watershed. There has been recent interest by energy companies in developing the natural gas reserves that are trapped within the Marcellus Shale, which is part of the Hamilton Group of Devonian age that underlies all the West Branch Delaware River Basin. Knowing the extent and thickness of stratified-drift (sand and gravel) aquifers within this basin can help State and Federal regulatory agencies evaluate any effects on these aquifers that gas-well drilling might produce. This report describes the hydrogeology of the 455-square-mile basin in the southwestern Catskill Mountain region of southeastern New York and includes a detailed surficial geologic map of the basin. Analysis of surficial geologic data indicates that the most widespread surficial geologic unit within the basin is till, which is present as deposits of ablation till in major stream valleys and as thick deposits of lodgment till that fill upland basins. Till and colluvium (remobilized till) cover about 89 percent of the West Branch Delaware River Basin, whereas stratified drift (outwash and ice-contact deposits) and alluvium account for 8.9 percent. The Cannonsville Reservoir occupies about 1.9 percent of the basin area. Large areas of outwash and ice-contact deposits occupy the West Branch Delaware River valley along its entire length. These deposits form a stratified-drift aquifer that ranges in thickness from 40 to 50 feet (ft) in the upper West Branch Delaware River valley, from 70 to 140 ft in the middle West Branch Delaware River valley, and from 60 to 70 ft in the lower West Branch Delaware River valley. The gas-bearing Marcellus Shale underlies the entire West Branch Delaware River Basin and ranges in thickness from 600 to 650 ft along the northern divide of the basin to 750 ft thick

  16. Geologic map of the La Mesita Negra SE Quadrangle, Bernalillo County, New Mexico

    USGS Publications Warehouse

    Shroba, Ralph R.; Thompson, Ren A.; Schmidt, Dwight L.; Personius, Stephen F.; Maldonado, Florian; Brandt, Theodore R.

    2003-01-01

    Geologic mapping, in support of the USGS Middle Rio Grande Basin Geologic Mapping Project, shows the spatial distribution of artificial-fill, alluvial, colluvial, and eolian deposits, lava flows and related sediments of the Albuquerque volcanoes, and upper Santa Fe Group sediments. These deposits are on, beneath, and along the West Mesa (Llano de Albuquerque) just west of Albuquerque, New Mexico. Artificial fill deposits are mapped chiefly beneath and near segments of Interstate 40, in an inactive landfill (or dump) north of Interstate 40 near the eastern boundary of the map area, and in the active Cerro Colorado landfill near the southwestern corner of the map area. Alluvial deposits are mapped in stream channels, beneath treads of terraces, and on hill slopes. They include alluvium in stream channels and beneath treads of low terraces, terrace alluvium, sheetwash deposits, gravelly alluvium, and old alluvium and calcic soils of the Llano de Albuquerque. Alluvial and colluvial deposits are mapped on hill slopes. They include young alluvial-slope deposits, alluvium and colluvium, undivided, and old alluvial-slope deposits. Colluvial deposits are also mapped on hill slopes. They include colluvial deposits, undivided, as well as alluvial deposits, eolian sand, and calcic soils associated with fault scarps. Eolian deposits as well as eolian and alluvial deposits mantle gently slopping surfaces on the Llano de Albuquerque. They include active eolian sand, active and inactive eolian sand and sheetwash deposits, undivided, and inactive eolian sand and sheetwash deposits, undivided. Lava flows and related sediments of the Albuquerque volcanoes were mapped near the southeast corner of the map area. They include five young lava flows, two young cinder deposits, and old lava flows. Upper Santa Fe Group sediments are well exposed and mapped in the western part of the map area. They include a gravel unit, a pebbly sand unit, and a mud and sand unit. Undivided upper Santa Fe

  17. Magnitude and frequency data for historic debris flows in Grand Canyon National Park and vicinity, Arizona

    USGS Publications Warehouse

    Melis, T.S.; Webb, R.H.; Griffiths, P.G.; Wise, T.J.

    1995-01-01

    Debris flows occur in 529 tributaries of the Colorado River in Grand Canyon between Lees Ferry and Diamond Creek, Arizona (river miles 0 to 225). An episodic type of flash flood, debris flows transport poorly-sorted sediment ranging in size from clay to boulders into the Colorado River. Debris flows create and maintain debris fans and the hundreds of associated riffles and rapids that control the geomorphic framework of the Colorado River downstream from Glen Canyon Dam. Between 1984 and 1994, debris flows created 4 new rapids and enlarged 17 existing rapids and riffles. Debris flows in Grand Canyon are initiated by slope failures that occur during intense rainfall. Three of these mechanisms of slope failure are documented. Failures in weathered bedrock, particularly in the Hermit Shale and Supai Group, have initiated many historic debris flows in Grand Canyon. A second mechanism, termed the fire-hose effect, occurs when runoff pours over cliffs onto unconsolidated colluvial wedges, triggering a failure. A third initiation mechanism occurs when intense precipitation causes failures in colluvium overlying bedrock. Multiple source areas and extreme topographic relief in Grand Canyon commonly result in combinations of these three initiation mechanisms. Interpretation of 1,107 historical photographs spanning 120 years, supplemented with aerial photography made between 1935 and 1994, yielded information on the frequency of debris flows in 168 of the 529 tributaries (32 percent) of the Colorado River in Grand Canyon. Of the 168 tributaries, 96 contain evidence of debris flows that have occurred since 1872, whereas 72 tributaries have not had a debris flow during the last century. The oldest debris flow we have documented in Grand Canyon occurred 5,400 years ago in an unnamed tributary at river mile 63.3-R. Our results indicate that the frequency of debris flows ranges from one every 10 to 15 years in certain eastern tributaries, to less than one per century in other

  18. An Alternative to Channel-Centered Views of the Landscape for Understanding Modern Streams in the Mid-Atlantic Piedmont Region, Eastern USA

    NASA Astrophysics Data System (ADS)

    Merritts, D. J.; Walter, R. C.; Rahnis, M. A.; Oberholtzer, W.

    2008-12-01

    Stream channels generally are the focus of conceptual models of valley bottom geomorphology. The channel-centered model prevalent in the tectonically inactive eastern U. S. invokes meandering stream channels migrating laterally across valley floors, eroding one bank while depositing relatively coarse sediment in point bars on the other. According to this model, overbank deposition during flooding deposits a veneer of fine sediment over the gravel substrate. Erosion is considered normal, and the net volume of sediment is relatively constant with time. A dramatic change in conditions-land-clearing during European settlement--led to widespread aggradation on valley bottoms. This historic sedimentation was incorporated in the channel-centered view by assuming that meandering streams were overwhelmed by the increased sediment load and rapidly aggraded vertically. Later, elevated stream channels cut through these deposits because of decreased sediment supply and increased stormwater runoff accompanying urbanization. This view can be traced to early ideas of stream equilibrium in which incoming sediment supply and runoff determine stream-channel form. We propose a different conceptual model. Our trenching and field work along hundreds of km of stream length in the mid-Atlantic Piedmont reveal no point bars prior to European settlement. Instead, a polygenetic valley-bottom landscape underlies the drape of historic sediment. The planar surface of this veneer gives the appearance of a broad floodplain generated by long-term meandering and overbank deposition, but the "floodplain" is a recent aggradational surface from regional base-level rise due to thousands of early American dams that spanned valley bottoms. As modern streams incise into the historic fine-grained slackwater sediment, they expose organic-rich hydric soils along original valley bottom centers; talus, colluvium, bedrock, and saprolite with forest soils along valley margins; and weathered Pleistocene (and

  19. High frequency seismic monitoring of debris flows at Chalk Cliffs (CO), USA

    NASA Astrophysics Data System (ADS)

    Coviello, Velio; Kean, Jason; Smith, Joel; Coe, Jeffrey; Arattano, Massimo; McCoy, Scott

    2015-04-01

    A growing number of studies adopt passive seismic monitoring techniques to investigate slope instabilities and landslide processes. These techniques are attractive and convenient because large areas can be monitored from a safe distance. This is particularly true when the phenomena under investigation are rapid and infrequent mass movements like debris flows. Different types of devices are used to monitor debris flow processes, but among them ground vibration detectors (GVDs) present several, specific advantages that encourage their use. These advantages include: (i) the possibility to be installed outside the channel bed, (ii) the high adaptability to different and harsh field conditions, and (iii) the capability to detect the debris flow front arrival tens of seconds earlier than contact and stage sensors. Ground vibration data can provide relevant information on the dynamics of debris flows such as timing and velocity of the main surges. However, the processing of the raw seismic signal is usually needed, both to obtain a more effective representation of waveforms and to decrease the amount of data that need to be recorded and analyzed. With this objective, the methods of Amplitude and Impulses are commonly adopted to transform the raw signal to a 1-Hz signal that allows for a more useful representation of the phenomenon. In that way, peaks and other features become more visible and comparable with data obtained from other monitoring devices. In this work, we present the first debris flows seismic recordings gathered in the Chalk Cliffs instrumented basin, central Colorado, USA. In May 2014, two 4.5-Hz, three-axial geophones were installed in the upper part of the catchment. Seismic data are sampled at 333 Hz and then recorded by a standalone recording unit. One geophone is directly installed on bedrock, the other one mounted on a 1-m boulder partially buried in colluvium. This latter sensor integrates a heavily instrumented cross-section consisting of a 225 cm2

  20. Soils of the coastal area of Santa Fé and Santa Cruz islands (Galápagos). Their micromorphology, mineralogy and genesis compared.

    NASA Astrophysics Data System (ADS)

    Stoops, Georges; Dumon, Mathijs; Van Ranst, Eric

    2015-04-01

    Santa Fé is a small island situated about 15 km SW of Santa Cruz and has a similar petrographic composition. The centre of Santa Cruz reaches up to 950 m a.s.l., Santa Fé is nowhere higher that 255 m. Even in the dry season the high mountain region of Santa Cruz profits therefore of an almost continuous drizzly rain (garrúa) resulting from the cooling of the rising moist air. The dry coastal zones are covered by sparse Opuntia vegetation. In the coastal soils a double to open spaced porphyric c/f related distribution pattern prevails. The micromass is greyish to yellowish brown on Santa Fé, reddish on Santa Cruz. The b-fabric is weakly granostriated, rarely calcitic crystallitic. The coarse material is restricted to fresh grains of plagioclase > iddingsite > augite > rare olivine, and some fresh basalt fragments. Remnants of illuvial clay coatings are more common on Santa Cruz. Only on Santa Fé hard, yellowish nodules (up to 700 µm) with a strongly mosaic speckled b-fabric and first order grey interference colours occur; their nature and genesis is a point of discussion. X-ray diffraction revealed the clay fraction of these soils to be comparable: poorly crystalline 2:1 phyllosilicates with broad irregular 001 reflections swelling to 1.8 nm after glycolation and collapsing to 1.0 nm after K-saturation and heating. Poorly crystalline kaolinite reflections are more prominent on Santa Cruz, whereas mica-like components (1.00 nm reflections) are restricted to Santa Fé. The presence of unweathered coarse material in an abundant micromass of alteration clay indicates a disequilibrium, and points to a transport of the fine material, in solid phase (colluvium) and/or as solution rather than an in situ weathering. Comparing the total chemical composition (corrected for LOI) of the coastal soils of Santa Cruz and Santa Fé with the average rock composition of both islands, one notes in the soils an increase in Al, Fe, Ti and K, and a loss of Mg, Ca and Na. On Santa F

  1. Surficial Geologic Map of the Evansville, Indiana, and Henderson, Kentucky, Area

    USGS Publications Warehouse

    Moore, David W.; Lundstrom, Scott C.; Counts, Ronald C.; Martin, Steven L.; Andrews, William M.; Newell, Wayne L.; Murphy, Michael L.; Thompson, Mark F.; Taylor, Emily M.; Kvale, Erik P.; Brandt, Theodore R.

    2009-01-01

    The geologic map of the Evansville, Indiana, and Henderson, Kentucky, area depicts and describes surficial deposits according to their origin and age. Unconsolidated alluvium and outwash fill the Ohio River bedrock valley and attain maximum thickness of 33-39 m under Diamond Island, Kentucky, and Griffith Slough, south of Newburgh, Indiana. The fill is chiefly unconsolidated, fine- to medium-grained, lithic quartz sand, interbedded with clay, clayey silt, silt, coarse sand, granules, and gravel. Generally, the valley fill fines upward from the buried bedrock surface: a lower part being gravelly sand to sandy gravel, a middle part mostly of sand, and a surficial veneer of silt and clay interspersed with sandy, natural levee deposits at river's edge. Beneath the unconsolidated fill are buried and discontinuous, lesser amounts of consolidated fill unconformably overlying the buried bedrock surface. Most of the glaciofluvial valley fill accumulated during the Wisconsin Episode (late Pleistocene). Other units depicted on the map include creek alluvium, slackwater lake (lacustrine) deposits, colluvium, dune sand, loess, and sparse bedrock outcrops. Creek alluvium underlies creek floodplains and consists of silt, clayey silt, and subordinate interbedded fine sand, granules, and pebbles. Lenses and beds of clay are present locally. Silty and clayey slackwater lake (lacustrine) deposits extensively underlie broad flats northeast of Evansville and around Henderson and are as thick as 28 m. Fossil wood collected from an auger hole in the lake and alluvial deposits of Little Creek, at depths of 10.6 m and 6.4 m, are dated 16,650+-50 and 11,120+-40 radiocarbon years, respectively. Fossil wood collected from lake sediment 16 m below the surface in lake sediment was dated 33,100+-590 radiocarbon years. Covering the hilly bedrock upland is loess (Qel), 3-7.5 m thick in Indiana and 9-15 m thick in Kentucky, deposited about 22,000-12,000 years before present. Most mapped surficial

  2. Permafrost thaw in upland catchments of central Alaska: groundwater connection and landscape evolution as discerned from U isotopes and dissolved organic carbon

    NASA Astrophysics Data System (ADS)

    Ewing, S. A.; O'Donnell, J. A.; Paces, J. B.; Jorgenson, M. T.; Kanevskiy, M. Z.; Harden, J. W.; Aiken, G.; Striegl, R. G.

    2009-12-01

    Permafrost thaw mobilizes carbon and transforms hydrologic flowpaths, with the potential for large feedback effects on climate. Permafrost thaw also results in poorly quantified geomorphic effects that depend on ground ice volumes, sediment texture, and thermal effects of thaw waters. Here we use 234U/238U activity ratios (ARs) to indicate the influence of deep groundwater following fire-induced permafrost thaw in geologically distinct upland catchments in central Alaska. The 234U/238U AR in water or ice increases as a function of contact time with sediment, at a rate that depends on sediment and water U concentrations, surface area, and sediment/water ratio. Combining U series data with solute concentrations for soil porewaters, shallow permafrost and surface streams, we make inferences about the influence of recent thaw (last 100 y) on landscapes, hydrology and dissolved organic carbon (DOC) dynamics in central Alaska. In a loess-dominated catchment where ice-rich silt is present to depths of up to 25 m, the depth of fire-induced thaw is limited to ~50 cm. DOC concentrations in surface waters and soil porewaters showed little seasonal or spatial variation (40±7 ppm in spring and fall 2008) and were positively correlated with solutes indicating mineral contact in fall 2008. In soil porewaters, surface waters and upper permafrost (2 m depth), 234U/238U ARs (1.15-1.27) were lower than those in deep permafrost (up to 1.55) and groundwater (1.54), suggesting no deep thaw or connection to deeper groundwater regardless of time-since-fire. Shallow thaw and soil wetting allowed for post-fire recovery of shallow permafrost and hence black spruce communities on the order of 100 y. Yet we observed landscape responses to thaw including thermokarst pits and channels, bank collapse, and stream incision, suggesting longer-term landscape equilibration. By contrast, in a colluvium-dominated catchment, gravelly textures allow better drainage of thaw water, resulting in deep thaw

  3. Revised geologic cross sections of parts of the Colorado, White River, and Death Valley regional groundwater flow systems, Nevada, Utah, and Arizona

    USGS Publications Warehouse

    Page, William R.; Scheirer, Daniel S.; Langenheim, V.E.; Berger, Mary A.

    2006-01-01

    confining units because of their low permeability. Late Proterozoic to Lower Cambrian clastic units overlie the crystalline rocks and are also considered confining units within the regional flow systems. Above the clastic units are Middle Cambrian to Lower Permian carbonate rocks that are the primary aquifers in the flow systems. The Middle Cambrian to Lower Permian carbonate rocks are overlain by a sequence of mainly clastic rocks of late Paleozoic to Mesozoic age that are mostly considered confining units, but they may be permeable where faulted. Tertiary volcanic and plutonic rocks are exposed in the northern and southern parts of the study area. In the Clover and Delamar Mountains, these rocks are highly deformed by north- and northwest-striking normal and strike-slip faults that are probably important conduits in transmitting groundwater from the basins in the northern Colorado and White River flow systems to basins in the southern part of the flow systems. The youngest rocks in the region are Tertiary to Quaternary basin-fill deposits. These rocks consist of middle to late Tertiary sediments consisting of limestone, conglomerate, sandstone, tuff, and gypsum, and younger Quaternary surficial units consisting of alluvium, colluvium, playa deposits, and eolian deposits. Basin-fill deposits are both aquifers and aquitards. The rocks in the study area were complexly deformed by episodes of Mesozoic compression and Cenozoic extensional tectonism. Some Cretaceous thrust faults and folds of the Sevier orogenic belt form duplex zones and define areas of maximum thickness for the Paleozoic carbonate rocks. Cenozoic faults are important because they are the primary structures that control groundwater flow in the regional flow systems.

  4. "The Great Cataract" - Effects of Late Holocene Debris Flows on Lava Falls Rapid, Grand Canyon National National Park, Arizona

    USGS Publications Warehouse

    Webb, Robert H.; Melis, Theodore S.; Wise, Thomas W.; Elliott, John G.

    1996-01-01

    Lava Falls Rapid is the most formidable reach of whitewater on the Colorado River in Grand Canyon and is one of the most famous rapids in the world. Although the rapid was once thought to be controlled by the remnants of lava dams of Pleistocene age, Lava Falls was created and is maintained by frequent debris flows from Prospect Canyon. We used 232 historical photographs, of which 121 were replicated, and 14C and 3He dating methods to reconstruct the ages and, in some cases, the magnitudes of late Holocene debris flows. We quantified the interaction between Prospect Canyon debris flows and the Colorado River using image processing of the historical photographs. The highest and oldest debris-flow deposits on the debris fan yielded a 3He date of 2.9?0.6 ka (950 BC), which indicates predominately late Holocene aggradation of one of the largest debris fans in Grand Canyon. The deposit, which has a 25-m escarpment caused by river reworking, crossed the Colorado River and raised its base level by 30 m for an indeterminate, although probably short, period. We mapped depositional surfaces of 6 debris flows that occurred after 950 BC. The most recent prehistoric debris flow occurred no more than 500 years ago (AD 1434). From April 1872 to July 1939, no debris flows occurred in Prospect Canyon. Debris flows in 1939, 1954, 1955, 1963, 1966, and 1995 constricted the Colorado River between 35 and 80 percent and completely changed the pattern of flow through the rapid. The debris flows had discharges estimated between about 290 and 1,000 m3/s and transported boulders as heavy as 30 Mg. The recurrence interval of these debris flows, calculated from the volume of the aggraded debris fan, ranged from 35 to 200 yrs. The 1939 debris flow in Prospect Canyon appears to have been the largest debris flow in Grand Canyon during the last 125 years. Debris flows in Prospect Canyon are initiated by streamflow pouring over a 325-m waterfall onto unconsolidated colluvium, a process called the

  5. Preliminary geologic map of the Simi 7.5' quadrangle, Southern California, a digital database

    USGS Publications Warehouse

    Yerkes, R.F.; Campbell, R.H.

    1997-01-01

    valley deposits, colluvium, active alluvial fans, and active stream deposits. Pleistocene- to Holocene-age landslide deposits are widespread throughout the Simi Quadrangle, especially in the finer grained Tertiary sedimentary units where bedding planes are dip slopes. In addition, massive slumps are present in the Sespe and Vaqueros Formations on anti-dip slopes. Seismic and well data from the San Fernando Valley (SFV) document evolution of that region from mid-Miocene rifting to north-south contraction. Formations in the western SFV subsurface (Cretaceous to Paleogene strata, and Miocene Topanga and Modelo Formations) trace southward to outcrops in the Santa Monica Mountains that constrain faulting along the valley's south basin edge. Cretaceous strata in the Simi Uplift to the west are over 2 km higher than equivalent strata beneath the western SFV across a boundary marked by the Chatsworth Reservoir fault, and Neogene thinning and offlap. The Simi fault, located at the eastern end of the Simi-Santa Rosa fault system, bounds the northern margins of the Simi and Tierra Rejada Valleys. West of Simi Valley, the Simi fault has placed Miocene Conejo Volcanics over Plio-Pleistocene Saugus Formation rocks. The 15.5 ± 0.8 m.y.a. base of the Conejo Volcanics, identified in oil well logs, is inferred to have a dip-slip separation of about 425 to 550 m, suggesting a low long-term slip rate of about 0.03 mm/yr. However, substantial late Quaternary offset is suggested by the presence of more than 150 m of Pleistocene and younger alluvium that fills the east-west trending, down-dropped bedrock trough beneath western Simi Valley. In addition, trenching within faulted colluvial deposits in Tierra Rejada Valley has revealed evidence of multiple shears within Holocene (?) deposits.

  6. Ground-Water Resources and the Hydrologic Effects of Petroleum Occurrence and Development, Warren County, Northwestern Pennsylvania

    USGS Publications Warehouse

    Buckwalter, Theodore F.; Moore, Michael E.

    2007-01-01

    Most of the northern half of Warren County is in the Northwestern Glaciated Plateau Section of the Appalachian Plateaus Physiographic Province. The remainder of the county is in the High Plateau Section. The glacial outwash sand and gravel hydrogeologic unit is the most extensively used unconsolidated unit for water supply in Warren County because it is capable of yielding large amounts of water to wells and it is situated in populated valleys. The median well yield for 47 specific- capacity tests was 25 gal/min (gallons per minute); well yields ranged from 2 to 1,600 gal/min. Acceptable well yields for domestic supply also are available from other unconsolidated hydrogeologic units including alluvium, colluvium, glacial drift, ice-contact stratified sand and gravel, and undifferentiated alluvium and glacial lacustrine. The median well yields during specific-capacity tests of wells in these five hydrogeologic units ranged from 8 to 18 gal/min. A comparison of the median specific capacities for wells in the unconsolidated and bedrock hydrogeologic units indicates that wells completed in the outwash sand and gravel hydrogeologic unit had the highest median specific capacity of 6.0 (gal/min)/ft (gallons per minute per foot); specific capacities for wells completed in the outwash sand and gravel unit ranged from 0.14 to 300 (gal/min)/ft. For wells completed in the bedrock hydrogeologic units, their corresponding median specific capacities are Pottsville Group, 0.5 (gal/min)/ft; Shenango Formation, 0.44 (gal/min)/ft; Cuyahoga Formation, 0.24 (gal/min)/ft; Knapp Formation, 0.45 (gal/min)/ft; Corry Sandstone through Riceville Formation, 0.67 (gal/min)/ft; Riceville Formation, 1.5 (gal/min)/ft; Oswayo Formation, 0.07 (gal/min)/ft; Venango Formation, 1.0 (gal/min)/ft; and Chadakoin Formation, 0.71 (gal/min)/ft. Annual precipitation at Warren for the years 1984-87 was above the long-term mean. The 4-year average of the annual hydrologic balance for 1984 indicated 40 percent

  7. Ground-water resources of Riverton irrigation project area, Wyoming

    USGS Publications Warehouse

    Morris, Donald Arthur; Hackett, O.M.; Vanlier, K.E.; Moulder, E.A.; Durum, W.H.

    1959-01-01

    The Riverton irrigation project area is in the northwestern part of the Wind River basin in west-central Wyoming. Because the annual precipitation is only about 9 inches, agriculture, which is the principal occupation in the area, is dependent upon irrigation. Irrigation by surface-water diversion was begum is 1906; water is now supplied to 77,716 acres and irrigation has been proposed for an additional 31,344 acres. This study of the geology and ground-water resources of the Riverton irrigation project, of adjacent irrigated land, and of nearby land proposed for irrigation was begun during the summer of 1948 and was completed in 1951. The purpose of the investigation was to evaluate the ground-water resources of the area and to study the factors that should be considered in the solution of drainage and erosional problems within the area. The Riverton irrigation project area is characterized by flat to gently sloping stream terraces, which are flanked by a combination of badlands, pediment slopes, and broad valleys. These features were formed by long-continued erosion in an arid climate of the essentially horizontal, poorly consolidated beds of the Wind River formation. The principal streams of the area flow south-eastward. Wind River and Fivemile Creek are perennial streams and the others are intermittent. Ground-water discharge and irrigation return flow have created a major problem in erosion control along Fivemile Creek. Similar conditions might develop along Muddy and lower Cottonwood Creeks when land in their drainage basins is irrigated. The bedrock exposed in the area ranges in age from Late Cretaceous to early Tertiary (middle Eocene). The Wind River formation of early and middle Eocene age forms the uppermost bedrock formation in the greater part of the area. Unconsolidated deposits of Quaternary age, which consist of terrace gravel, colluvium, eolian sand and silt. and alluvium, mantle the Wind River formation in much of the area. In the irrigated parts