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Jeffrey R. Knott Joanna M. Fantozzi Kelly M. Ferguson Summer E. Keller Khadija Nadimi Carolyn A. Rath Jennifer M. Tarnowski Michelle L. Vitale 《Quaternary Research》2012,78(2):363-372
Pluvial lake deposits are found throughout western North America and are frequently used to reconstruct regional paleoclimate. In Death Valley, California, USA, we apply the beach particle technique (BPT) of Adams (2003), Sedimentology, 50, 565–577 and Adams (2004), Sedimentology, 51, 671–673 to Lake Manly deposits at the Beatty Junction Bar Complex (BJBC), Desolation Canyon, and Manly Terraces and calculate paleowind velocities of 14–27 m/s. These wind velocities are within the range of present-day wind velocities recorded in the surrounding area. Sedimentary structures and clast provenance at Desolation Canyon and the Manly Terraces indicate sediment transport from north to south. Lake level, based on the elevation of constructional features, indicates that the hill west of the BJBC was an island and that the BJBC spits formed during simple lake regression. The data are consistent with the hypothesis that the present wind regime (velocity and direction) formed the pluvial Lake Manly features. 相似文献
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The Northern Till is a thick (>65 m) deformation till underlying some 7500 km2 of Southern Ontario, Canada including the Peterborough Drumlin Field. It was deposited below the Lake Ontario ice stream of the Laurentide Ice Sheet. The till rests on glaciotectonized aquifer sediments and consists of multiple beds of till up to 6 m thick. These are separated by boulder lags, sometimes in the form of striated pavements, with thin (<30 cm) interbeds of poorly sorted waterlaid sand. The composite till stratigraphy indicates ‘punctuated aggradation’ where the subglacial bed was built up incrementally by the repeated ‘immobilization’ of deforming overpressured till layers. Boulders and sands indicate pauses in subglacial aggradation marked by sluggish sheet flows of water that reworked the top of the underlying till. Interbeds are laterally extensive and correlated using downhole electrical conductivity, core recovery and natural gamma data. A 3-D finite element model (FEFLOW) using data from 200 cored and geophysically logged boreholes, and a large digital water well dataset of 3400 individual records shows that the till functions as a ‘leaky aquitard’ as a consequence of water flow through interbeds. It is proposed that interbeds played a similar role in the subglacial hydraulic system below the Laurentide Ice Sheet by allowing drainage of excess porewater pressures in deforming sediment and promoting deposition of till. This is in agreement with theoretical studies of deforming bed dynamics and observations at modern glaciers where porewater in the deforming layer is discharged into underlying aquifers. In this way, the presence of interbeds may be fundamental in retarding downglacier transport of deforming bed material thereby promoting the build-up of thick subglacial till successions. 相似文献
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The city of Scarborough lies on the eastern margin of the Greater Toronto Area of southern Ontario, Canada, along the northern
coastline of Lake Ontario. The City has a population of 500,000 and is presently one of the fastest growing communities in
Canada. The City is expanding northwards onto rural land on the south slope of the large Pleistocene glacial Oak Ridges Moraine
system. The moraine system is underlain by a thick (150 m) succession of tills, sands and gravels and is a regionally-significant
recharge area for three principle aquifer systems that discharge to numerous watercourses that flow to Lake Ontario. Protection
of deeper aquifers from surface-generated urban contaminants is a particular concern.
A groundwater flow model using Visual MODFLOW was developed for the 350-km2 Rouge River–Highland Creek (RRHC) drainage basin using an extensive GIS-based collection of subsurface geological, geophysical
and hydrogeological data, maps of land use and surficial geology. The RRHC model was calibrated against point water level
data, known potentiometric surfaces of the principal aquifers and baseflow measurements from streamflow gauging stations and
determined to be within acceptable limits. Water balance calculations indicate that 70% of the basin recharge (106,000 m3/day) enters the Upper Aquifer along the crest and immediate flanks of the Oak Ridges Moraine. To the south, Upper Aquifer
water moving through fractured till aquitards accounts for more than 75% of recharge to deeper aquifers. Water quality data
confirm previous observations that urban- and rural-sourced contaminants (chlorides and nitrates) present in Upper Aquifer
waters are moving rapidly into deeper aquifers. Some 83% of total RRHC recharge water is ultimately discharged as baseflow
to creeks draining to Lake Ontario; the remainder discharges to springs and along eroding lakeshore bluffs. Model results
demonstrate that deeper aquifers are poorly protected from urban contaminants and that long-term protection of ground and
surface water quality has to be a priority of municipal planners if the resource is not to be severely degraded.
Electronic Publication 相似文献
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Rock reinforcement systems, such as resin-grouted rock bolts, display complex creep behavior because both grouting materials and bolts show time-dependent behavior. In this paper, only the time-dependent behavior of grouting material was investigated, in which creep tests of grouting material was conducted in triaxial compression apparatus at room temperature. The test specimens were provided from the Araldite epoxy resin used in rock reinforcement. We attempt to predict long-term creep parameter using triaxial creep tests and to define time-dependent characteristics of the bounding material. In short-term creep tests, three different axial and confining stress levels were applied in steps to each specimen. The transient creep for all the stress levels were described by power function which fit properly to time–strain curves. The maximum difference between the proposed model and experimental long-term creep strain was less than 7.1 %. It was observed that the creep rate of a grouting material specimen directly depends on the deviator of stress (i.e., σ1–σ3). 相似文献
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Soil genesis and clay mineralogy studies play an important role in sustainable soil and agriculture management. Soil properties are highly affected by geomorphic position. To study the physicochemical soil properties and clay mineralogy related to geomorphic surfaces, 12 representative pedons on different landforms in the Mahan-Joupar area, central Iran, were selected. Soil moisture and temperature regimes of the area were aridic and mesic, respectively. Rock and mantled pediments, alluvial fan, inselberg, plain, and transitional surfaces were among the different landforms studied. Alluvial fan was also divided into stable and unstable surfaces according to detailed field studies. Argillic horizon found in stable alluvial fan surfaces was attributed to the presence of a more humid paleoclimate in the history of the area. Coating of calcite on clay films observed by SEM showed that clay was illuviated in more humid periods of the past and then followed by calcium carbonate illuviation during arid climates. Smectite, kaolinite, chlorite, illite, and palygorskite clay minerals were identified by X-ray and SEM observations. Finally, a close relationship between the geomorphology and soil genesis and clay mineralogy was found in the area. 相似文献
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The Darreh Sary metapelitic rocks are located in the northeast of Zagros orogenic belt and Sanandaj-Sirjan structural zone. The lithological composition of these rocks includes slate, phyllite, muscovitebiotite schist, garnet schist, staurolite-garnet schist and staurolite schist. The shale is the protolith of these metamorphic rocks, which was originated from the continental island arc tectonic setting and has been subjected to processes of Zagros orogeny. The deformation mechanisms in these rocks include bulging recrystallization (BLG), subgrain rotation recrystallization (SGR) and grain boundary migration recrystallization (GBM), which are considered as the key to estimate the deformation temperature of the rocks. The estimated ranges of deformation temperature and depth in these rocks show the temperatures of 275–375, 375–500, and >500°C and the depths of 10 to 17 km. The observed structures in these rocks such as faults, fractures and folds, often with the NW-SE direction coordinate with the structural trends of Zagros orogenic belt structures. The S-C mylonite fabrics is observed in these rocks with other microstructures such as mica fish, σ fabric and garnet deformation indicate the dextral shear deformation movements of study area. Based on the obtained results of this research, the stages of tectonic evolution of Darreh Sary area were developed. 相似文献
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Alireza Nadimi 《Geotectonics》2015,49(6):560-578
Cherty marbles of Hasan-Robat area, northwest of Isfahan, in the Sanandaj–Sirjan Zone of Iran preserves evidences of multiple deformational events. The Sanandaj–Sirjan Zone is the inner crystalline zone of the Zagros Orogen, which has been highly deformed and exhumed during continental collision between the Arabian Plate and Central Iran. The Hasan-Robat area is an example of the exposed Precambrian–Paleozoic basement rocks that stretched along two NW–SE-trending faults and located in the inner part of the HasanRobat positive flower strcuture. The Hasan-Robat marbles record a complex shortening and shearing history. This lead to the development of disharmonic ptygmatic folds with vertical to sub-vertical axes and some interference patterns of folding that may have been created from deformations during the Pan-African Orogeny and later phases. Based on this research, tectonic evolution of the Hasan-Robat area is interpreted as the product of three major geotectonic events that have been started after Precambrian to Quaternary: (1) old deformation phases (2) contractional movements and (3) strike-slip movements. Different sets and distributions of joints, faults and folds are confirmed with effect of several deformational stages of the area and formation of the flower structure. 相似文献
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