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1.
Estimating groundwater recharge induced by engineering systems in a semiarid area (southeastern Spain) 总被引：2，自引：0，他引：2
W. Martín-Rosales J. Gisbert A. Pulido-Bosch A. Vallejos A. Fernández-Cortés 《Environmental Geology》2007,52(5):985-995
The scarcity of water resources in semiarid regions is usually accompanied by brief periods of quite intense precipitation
that can generate potentially catastrophic floods. In such regions, the use of runoff water for aquifer recharge can contribute
to both flooding prevention and effective management of water resources. This paper presents the results of a study undertaken
in southeastern Spain focusing on the recharge induced by a number of engineering structures (check dams) and gravel pits.
The current network of check dams consists of 107 dams, of which 64 are located over permeable substrates and so we can induce
recharge of the storm runoff retained therein. The hydrological model was performed using the curve number method (CN) of
the Service for the Conservation of Soils, utilizing code HEC-HMS. Results indicate that the proportion of runoff infiltrated
through the check dams varies from 3% to more than 50%, according to the effective volume of water dammed and the substrate.
In addition, hydrological modelling was carried out in a subbasin taking advantage of the presence of one of a number of gravel
pits. The gravel pits are situated in the apical sectors of alluvial fans that overlie hydrogeological units that are widely
overexploited, and so they are well positioned for use for artificial recharge. In this case, we conclude that a pit is capable
of retaining and infiltrating the combined runoff volumes for various return periods (5, 25, 50, and 100 years). Furthermore,
the simulation carried out suggests that the recharge processes in these environments are intimately linked to episodic storm
events. The incorporation of hydrogeological criteria in the design and construction of check dams could therefore be very
useful for the optimum management of water resources in semiarid zones. 相似文献
2.
正断层构造广泛发育于盆地内和造山带中,其对可容空间分配及沉积物分布具有明显的控制作用,从而影响了冲积扇形态。为进一步探究正断层构造对冲积扇沉积过程及其内部构型的控制作用,利用水槽实验对正断层构造发育背景下的冲积扇发育过程进行模拟再现。研究表明,携带大量沉积物的碎屑流优先在上盘近断层处泄载,后经牵引流的改造,形成沿断面垂向生长、尖端指向物源的三角形分水滩。水动力较强时碎屑流越过分水滩并在分水滩尾部发育越滩朵体,水动力较弱时碎屑流遇分水滩尖端分流后沿断面在分水滩两侧发育断面朵体。受控于断面及分水滩的阻挡,冲积扇表面不同位置的沉积物泄载过程差异较大,粒度差异明显,上盘扇体中分水滩沉积物偏粗,越滩朵体次之,断面朵体最细。冲积扇的发育过程依据分水滩砂体厚度和断距大小之间的差异,共分为3个阶段。断距大小还会影响冲积扇沉积构型,断距越大,上盘可容空间越大,分水滩发育时间越长,扇体内部砂体叠置样式越复杂。受控于正断层的冲积扇内部构型在垂直物源剖面上从近端至远端,分别发育纵向沙坝、分水滩及碎屑流朵体,在平行物源剖面上以复合水道主控、分水滩叠复体主控、多期朵体叠复体主控为主。 相似文献
3.
Simulation experiment of sedimentary process and sedimentary architecture of alluvial fan under the control of normal faults 
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下载免费PDF全文 Normal fault structures are widely developed in basins and orogenic belts,which control the accommodation space and the distribution of sediments and thus affecting the morphology of alluvial fans. A flume tank experiment was carried to simulate and clarify the control of normal faults on the sedimentary process and internal architecture of alluvial fans.The results show that the large amount of sediments carried by debris flow tend to be unloaded near the hanging wall of faults and are subsequently reworked by traction current,which result in a triangular distributary gravel bar grows vertically on fault plane with the tip pointing to the source area. When the hydrodynamic force is strong,debris flow goes across distributary gravel bar and forms over-bar lobe at the tail of the distributary gravel bar. When the hydrodynamic force is weak,debris flow forms fault plane-dominated lobe along fault plane and is located on both sides of the distributary gravel bar. Under the control of normal faults and the barrier of distributary gravel bar,the unloading process of sediments varies greatly at different positions on the surface of alluvial fan. The particle size varies greatly among different facies,with coarsest grains developed on the fans of hanging wall,finer grained on over-bar lobe and finest sediments on fault plane-dominated lobe. The development process of alluvial fan can be divided into three stages,according to the sandbody thickness and fault throw of distributary gravel bar. The fault throw also affects the sedimentary architecture of alluvial fan,with larger the fault throw generating larger the accommodation space of hanging wall,longer development time of distributary gravel bar and more complex of the superposition pattern of the sand bodies inside the fan. The internal architecture of alluvial fan that is controlled by normal faults includes longitudinal sandbar,distributary gravel bar and debris flow lobe in the profile vertical perpendicular to the sediment source direction from the proximal to the distal end. Along sediment longitudinal section,composite channel,superimposed distributary gravel bar complex and superimposed bodies of multi-phased lobes are dominant facies. 相似文献
4.
The central part of the Murrumbidgee River meanders across an alluvial plain which is 1.5 km to 5 km wide, and confined between low hills composed of granite and folded lower Palaeozoic rocks. Deposition commenced under humid and reducing conditions during the Miocene, and continued during Pliocene time. Oligomict quartz‐sand and gravel beds are dominant in the sequence, and are interlayered with grey to black clay and silty clay, which contain a prolific pollen fauna. During Pleistocene time, a marked reduction in rainfall and consequent change in vegetation resulted in the deposition of a widespread coarse polymict poorly‐sorted gravel associated with yellow and brown clay and silt. The quartz‐sand and gravel beds within the Pliocene deposits constitute a major aquifer system and contain low salinity water suitable for irrigation and town water‐supply purposes. Since 1968, increasing demand has been made on this aquifer system, and wells sunk for various State and Local Government bodies have a total installed capacity of approximately 1000 litres/sec. The most concentrated exploration and development has been effected east of Wagga Wagga, where a well field was constructed to provide water for a regional water supply scheme. Following a refraction seismic survey, test drilling, and mathematical simulation, four production wells were constructed. Mathematical simulation models developed on a mini‐computer were designed primarily to study the behaviour of the aquifer system in response to pumping from the Pliocene aquifers. An analytical model was used to assist in the location of production wells, and a numerical model was used, after construction of the wells, to determine what additional losses from the Murrumbidgee River would be induced by pumping them. These losses were found to correspond to approximately 90% of the pumping rate during long term pumping. 相似文献
5.
Source, type, and quantity of various components of groundwater, as well as their spatial and temporal variations were determined
by different hydrochemical methods in the alluvial aquifer of the upper Rhone River valley, Bois de Finges, Wallis Canton,
Switzerland. The methods used are hydrochemical modeling, stable-isotope analysis, and chemical analysis of surface water
and groundwater. Sampling during high- and low-water periods determined the spatial distribution of the water chemistry, whereas
monthly sampling over three years provided a basis for understanding seasonal variability. The physico-chemical parameters
of the groundwater have spatial and seasonal variations. The groundwater chemical composition of the Rhone alluvial aquifer
indicates a mixing of weakly mineralized Rhone River water and SO4-rich water entering from the south side of the valley. Temporal changes in groundwater chemistry and in groundwater levels
reflect the seasonal variations of the different contributors to groundwater recharge. The Rhone River recharges the alluvial
aquifer only during the summer high-water period.
Electronic Publication 相似文献
6.
Dredging the alluvial fans for repaving the international road located in the bottom of the Wadi Watir valley produced vertical cliff faces of different heights, and at different locations of the fans. The heights of the cliff faces resulted in considerable elevation differences between the surface of the dredged alluvial fans and the local base level provided by the Watir trunk valley. The principal geomorphic response to this anthropogenic intervention is triggering upstream channel incision waves at different intensities in the fluvial systems of the downstream reaches of the Watir drainage basin. The channel incision processes resulted in subsequent geomorphic adjustment scenarios that vary from widening the active channels on the surface of the dredged fans, triggering rockfalls from the adjacent hillslopes, and transporting coarse alluvial deposits from the main sediment sources of the fluvial systems, and eventually re-depositing them as sheetform gravel, channelform gravel, and new fan lobes. The major outcome of the various geomorphic adjustment processes was changing the role of the alluvial fans within the fluvial systems from buffer zones where fan aggradation was dominant into dynamic coupled zones. Being coupled zones, the dredged alluvial fans allowed high potential of mass transmission from the feeder catchment areas into the Watir trunk valley. Under such conditions, it could be stipulated that considerable changes in the morphology of landscapes are highly anticipated in response to flash flood events that intermittently occur in the Watir drainage basin. 相似文献
7.
Ahmet Apayd?n 《Environmental Earth Sciences》2012,65(1):241-255
This study explains the impact of sand–gravel mining and over-abstraction, and the response of the groundwater system in the
Kazan Plain, Turkey. The plain used to be known for its fresh groundwater potential, valuable agricultural lands and natural
beauty until the 1980s. According to the estimation in 1975, there was 15.5 million m3 annual useable freshwater in the Quaternary sand–gravel aquifer. Groundwater level ranged between 0 and 5 m from the surface
of the plain in the 1970s. Because of the large and deep excavations by the sand–gravel pits during the past 25–30 years,
the aquifer has thinned and removed entirely in some places. In addition, over-abstraction has accelerated the decline of
the groundwater level, particularly in the middle and the upper part of the plain in recent years. As of 2009, about 12% of
the total volume of the aquifer area removed by the pits and groundwater table has been reduced to between 5 and 20 m. The
decline of the water table reaches 15–20 m in the regions where over-abstraction has taken place. To reduce the hazards to
the groundwater system, the sand–gravel pits have to be banned immediately, a reclamation project applied and abstraction
must be reduced. 相似文献
8.
Sinkhole development along the western shore of the Dead Sea became a major concern in 1990 with the appearance of a series
of holes 2–15 m diameter and up to 7 m deep in the Newe Zohar area. One of these sinkholes, below the asphalt surface of the
main road along the western shore of the Dead Sea, was opened by a passing bus. Repeated infilling and collapse of these holes
indicated the extent of this ongoing process and the significance of this developing hazard. Since then sinkholes have developed
in other areas including Qalia, Ein Samar, Ein Gedi and Mineral Beach.
Three main types of sinkholes have been recognized. Gravel holes occurring in alluvial fans, mud holes occurring in the intervening
bays of clay deposits between fans and a combination of both types at the front of young alluvial fans where they overlap
mud flats. Fossil, relict sinkholes have been observed in the channels of some old alluvial fans.
Sinkhole development is directly related to the regression of the Dead Sea and the corresponding lowering of the regional
water table. Continuation of this process widens the neritic zone enveloping the sea and increases the sinkhole hazard of
the region.
Received: 4 February 1999 · Accepted: 8 April 1999 相似文献
9.
Based on this preliminary study, existing sand and gravel mining regulations (in Maine, USA) can be inferred to provide some
protection to water resources. Sand and gravel deposits are important natural resources that have dual uses: mining for construction material and pumping for drinking water. How the mining of sand and gravel affects aquifers and change aquifer vulnerability to contamination
is not well documented. Mining regulations vary greatly by state and local jurisdiction. This study test metrics to measure
the effectiveness of mining regulations. The sand and gravel aquifer system studied is covered with former and active gravel
pits to nearly 25% of its areal extent. Data from homeowner interviews and field measurements found scant evidence of changes
in water quantity. Water quality analyses collected from springs, streams, ponds and wells indicate that the aquifer was vulnerable
to contamination by chloride and nitrate. However, water quality changes can not be related directly to mining activities. 相似文献
10.
LauraPatriciaPerucca JuanParedes 《《幕》》2004,27(3):190-194
The study consists of the identification of landforms subject to alluvial fan flooding in active sectors of the Zonda range piedmont. In the Department of Pocito, located about 5 km southwest of San Juan City, a series of alluvial fans have been identified. These alluvial fans are located downstream of the natural drainage basins covering an area of approximately 130 km^2 towards the eastern slopes of the Zonda range at a median elevation of 2,000 m a.s.l. 相似文献
11.
A large number of valleys and basin systems are present in the northwestern part of the Himalayas in Pakistan which form significant aquifers in the region. Hydrogeophysical investigations in the western part of Nowshera District, a part of the intermontane Peshawar basin, were undertaken to help to determine the availability of groundwater resources in the region. Thirty vertical electrical resistivity soundings (VES) were acquired using a Schlumberger expanding array configuration with a maximum current electrode spacing (AB/2) of 150 m in delineating the groundwater potential in the study area. The results of the interpreted VES data using a combination of curve matching technique and computer iterative modeling methods suggest that the area is underlain by 3 to 5 geo-electric layers. The interpretation results showed that the geo-electrical succession consists of alluvium comprising of alternating layers of clay, silty clay, fine to coarse sands, sand with gravels and gravels of variable thickness. High subsurface resistivity values are correlated with gravel–sand units and low resistivity values with the presence of clays and silts. The modeled VES results were correlated with the pumping tests results and lithological logs of the existing wells. The pumping test suggests the transmissivity of the aquifer sediments is variable corresponding to different sediments within the area. The gravel–sand intervals having high resistivity value show high transmissivity values, whereas clay–silt sediments show low transmissivities. It is concluded that majority of the high resistive gravel–sand sediments belong to an alluvial fan environment. These gravel–sand zones are promising zones for groundwater abstraction which are concentrated in the central part of the study area. 相似文献
12.
红盆内１０９个点砾岩砾石万分、砾径、古流向的系统统计与沉积学研究，确定该红盆历经三期洪积事件，形成了８个冲积扇体。其中期为洪积事件上鼎盛时期，形成５个冲积扇体，并在其内首次发现恐龙蛋化石，属晚白垩世中晚期。 相似文献
13.
One-third of the population of Oman depends upon groundwater extracted from the alluvium of the Batinah Plain, on the coast
of the Gulf of Oman. Deep geophysical exploration techniques were used to determine the depth and nature of the alluvium and
the boundaries of the aquifer. The base and structural controls of the alluvial basin at its contact with Tertiary marine
sediments and Cretaceous ophiolite were mapped with seismic reflection data, recorded originally for oil exploration. The
base of the alluvium dips northward from the foothills of the Northern Oman Mountains, reaching a maximum depth of 2000 m
at the coast. The varying facies of the alluvium are grossly characterised by different, overlapping ranges of electrical
resistivity, depending largely on the clay content and degree of cementation. Resistivities near the coast are reduced by
saline intrusion. These variations of resistivity were mapped with time-domain electromagnetic sounding along 400 km of profile,
to distinguish among the three zones of the alluvial aquifer. The wedge of saline intrusion was also delineated, up to 10 km
from the coast. The thickness of the saturated gravel aquifer ranges from 20–160 m in an area greater than 600 km2.
Received, April 1997 · Revised, January 1998 · Accepted, April 1998 相似文献
14.
《Proceedings of the Geologists' Association. Geologists' Association》2017,128(1):83-109
Over the past 200 years significant research effort has gone into explaining the origin of the obvious former shorelines in Glen Roy (the so-called “Parallel Roads”). The large gravel deposit at the mouth of Glen Turret has attracted similar interest, but a solution to its origin and age remains contested: the same applies to the associated gravel fans in upper Glen Roy. This paper presents the results of systematic mapping and instrumental levelling of these features and new evidence from two previously unrecorded gravel fans in the nearby Allt Chonnal valley. Interpretation of altitudinal and lithofacies data indicates that all the fans (including the one at the mouth of Glen Turret) were deposited in a series of ice-dammed lakes during the Loch Lomond Stadial (Younger Dryas). The largest gravel fans were deposited in the shallow lake heads of the 260 m, 325 m and 350 m lakes in upper Glen Roy, infilling these areas to the extent that deposition was in part subaerial. The absence of foreset bedding from the deposits is explained by the relatively shallow depth of lake waters, which inhibited development of classic Gilbert-type deltas and encouraged Hjulström-type fans. The previous assumption that gravel deposition into the 325 m and 350 m lakes was relatively limited is shown to be erroneous. The Allt Chonnal gravel fans, deposited into these lakes, have an estimated combined volume of 6,000,000 m3 deposited in about 200 years. Significant gravel deposition into these former lakes continued at least until glaciers started to retreat in Glen Roy. When glacier retreat began, gravel deposition was reduced by over 85%. This research also concludes that the glacier which deposited the Turret fan emanated from Glen Gloy, supplied not only by ice from the south but also from ice that spilled into Glen Gloy from the adjacent Great Glen. The Loch Lomond Stadial (LLS) ice cap mapped in the Monadhliath Mountains was connected to the west Highland ice cap, which at the time filled the Great Glen. Regional equilibrium line altitude (ELA) estimates, based solely on the Monadhliath LLS ice cap evidence, may therefore be altitudinally too high. 相似文献
15.
Tectonic controls on the geomorphic evolution of alluvial fans in the Piedmont Zone of Ganga Plain,Uttarakhand, India 总被引：3，自引：0，他引：3
Pradeep K. Goswami Charu C. Pant Shefali Pandey 《Journal of Earth System Science》2009,118(3):245-259
The Piedmont Zone is the least studied part of the Ganga Plain. The northern limit of the Piedmont Zone is defined by the
Himalayan Frontal Thrust (HFT) along which the Himalaya is being thrust over the alluvium of the Ganga Plain. Interpretation
of satellite imagery, Digital Terrain Models (DTMs) and field data has helped in the identification and mapping of various
morphotectonic features in the densely forested and cultivated Piedmont Zone in the Kumaun region of the Uttarakhand state
of India. The Piedmont Zone has formed as a result of coalescing alluvial fans, alluvial aprons and talus deposits. The fans
have differential morphologies and aggradation processes within a common climatic zone and similar litho-tectonic setting
of the catchment area. Morphotectonic analysis reveals that the fan morphologies and aggradation processes in the area are
mainly controlled by the ongoing tectonic activities. Such activities along the HFT and transverse faults have controlled
the accommodation space by causing differential subsidence of the basin, and aggradation processes by causing channel migration,
channel incision and shifting of depocentres. The active tectonic movements have further modified the landscape of the area
in the form of tilted alluvial fan, gravel ridges, terraces and uplifted gravels. 相似文献
16.
ERICH DRAGANITS CHRISTOPH JANDA 《Boreas: An International Journal of Quaternary Research》2003,32(2):436-442
Subaqueous, bowl-shaped depressions found in a Himalayan pond formed in an abandoned river channel in the Lingti Valley (Spiti, NW India) are spring pits (Quirke 1930 ). The occurrence of the spring pits is restricted to the western end of the pond, where coarse-grained, highly permeable alluvial fan material continues below lacustrine mud deposits. The spring pits formed by active vertical discharge of ground water from an underlying artesian alluvial fan aquifer, confined by the overlying fine-grained lacustrine sediments. The aquifer is continuously recharged by down-slope ground-water flow in the alluvial fan. These small artesian springs are comparable with much larger artesian springs described in the literature and a similar mechanism of formation is proposed. Some similarities in their shapes and mechanisms of formation may indicate that spring pits represent small, nearshore examples of pockmarks. The differences of these features, formed by persistent fluidization from short-lived seismic liquefaction processes, are discussed and the utility of the structures for palaeo-environmental and palaeo-ground-water interpretation is evaluated. 相似文献
17.
新疆乌恰萨热克铜矿北矿带库孜贡苏组沉积相、古流向、物源区及其找矿意义——来自砾石统计分析的证据 总被引：1，自引：1，他引：0
萨热克盆地库孜贡苏组是萨热克铜矿的赋矿层位,开展沉积相、物源区及古流向研究对隐伏铜矿的勘探具有重要意义。选取萨热克铜矿北矿带库孜贡苏组地表矿化最好的砾岩展开砾石统计分析,结果表明,偏斜度显示砾岩为冲积扇相沉积,砾石叠瓦状和砂岩斜层理产状统计显示古流向为北北东向;砾石成分主要为石英、石英砂岩、砂岩,石英岩等;粒度分布呈宽峰态或尖峰态;物源区为元古宇长城系阿克苏群变质岩剥蚀区;物源补给分为主河流补给和支河流补给2种方式。冲积扇相、古流向、物源区分析确定了矿体的范围、最优的勘探线布置方位和潜在的找矿靶区,具有很好的勘探意义。 相似文献
18.
In 1985, a former tire manufacturing plant surrounded by agricultural fields in the Salinas Valley was designated a Superfund Site by the US Environmental Protection Agency. The plant had been operating for seventeen years, from 1963 until 1980. When dismantling of the plant was started, it was determined that toxic hydrocarbon solvents and oils from the plant had contaminated soil and groundwater in alluvial deposits alongside the plant. It was determined later that the groundwater contamination also lay beneath the agricultural fields in a narrow groundwater plume that extends about 4.3 km downgradient from the plant. Because of the complex architecture of the aquifer system, the gradient, and extensive pumping of agricultural wells, the contaminants migrated northwestward and downward to deeper levels away from the plant.
The agricultural fields are underlain by an unconfined shallow aquifer and by a system of confined aquifers that extend to more than 180 m below surface. Aquifers are discontinuous beds of channel sand and gravel; confining beds are overbank clay and silt, and estuarine clay.
Geophysical data, logs of existing agricultural and other wells, and careful consideration of the stratigraphic architecture of the depositional environment provided the basis for a conceptual hydrogeologic model and for locating characterization wells for detailed visual and geophysical logging and hydrologic testing. Successive refinements of the characterization by sequential installation of wells indicated optimal locations for installation of extraction and monitoring wells. Validity of the concept of the hydrogeologic regime was verified by close match of predictions made by modeling with the later results of pumping from the extraction wells in a pump-and-treat system.
Successful remediation was accomplished by analyzing data from 110 agricultural wells, the few domestic water wells, nearly 200 sequentially installed stratigraphic-characterization and monitoring wells, 25 extraction wells, and by close cooperation among federal, state and local agencies, and the ranchers and growers.
Total contaminants recovered from activated-charcoal strippers of the treatment system totalled < 230 kg. Large quantities were harmlessly volatilized and dispersed into the atmosphere by air strippers and by agricultural sprinkling systems spraying water onto the fields. Crop testing showed no contamination of food crops. The activity has taken seven years and has cost more than US$22 million. 相似文献
19.
Autogenic dynamics of alluvial fans in endorheic basins: Outcrop examples and stratigraphic significance 总被引：1，自引：0，他引：1
Alluvial fans are relatively simple depositional systems, due to the direct coupling of sediment sources and adjacent accumulation areas. Nonetheless, general models of alluvial‐fan evolution and stratigraphy remain elusive, due to the great sensitivity of such systems to allogenic controls and their strongly case‐specific responses. Autogenic processes intrinsic to alluvial‐fan dynamics can complicate stratigraphic architectures, with effects not easily distinguishable from those of allogenic forcing. A distinction is made here between lateral autogenic dynamics, tied to spatial sediment distribution over fan surfaces, and vertical autogenic dynamics, related to independent incision‐aggradation cycles. Autogenic mechanisms have been highlighted recently by modelling studies, but remain poorly constrained in field‐based studies. Examples are presented here from the margins of the Cenozoic Teruel and Ebro basins (Spain), where alluvial fans accumulated thick successions during phases of basin topographic closure and endorheic drainage which promoted forced aggradation. Fan successions consist of conformable architectures of stacked clastic sheets, laterally continuous and with no evidence of internal unconformities, inset architectures, fan segmentation or preserved incised channels. Continuous aggradation in these closed basins strongly inhibited ‘vertical’ autogenic dynamics in the form of fan head and through fan incision, due to the forced rise in geomorphic base level and the creation of positive accommodation. Furthermore, the lack of incised channels favoured widespread sediment transport and aggradation over broad fan sectors in relatively short time spans, in contrast to the typical occurrence of active lobes and abandoned fan surfaces caused by ‘lateral’ autogenic dynamics. Stratigraphic records of alluvial fans developed in endorheic basins are essentially complete and largely unaffected by autogenic processes. The latter characteristic implies that they can be more unambiguously interpreted in terms of allogenic forcing, because stratigraphic signatures are not complicated by the effects of complex fan autodynamics. 相似文献
20.
Pre-vegetation alluvial fan facies and processes: an example from the Cambro-Ordovician Rozel Conglomerate Formation, Jersey, Channel Islands 总被引：1，自引：0，他引：1
DAVID J. WENT 《Sedimentology》2005,52(4):693-713
Prior to the Silurian a lack of land vegetation is expected to have influenced the processes of sedimentation on alluvial fans, principally by causing increased rates of run-off and erosion in the fan catchments. In the Cambro-Ordovician Rozel Conglomerate Formation, this effect was central to the generation of alluvial fan deposits that are unusually deficient in sand and clay, despite being sourced from a catchment dominated by sandstone and mudstone. Seven facies are identified, interpreted as representing the deposits of: (i) shallow stream and sheetfloods, (ii) channelized, non-cohesive debrisflows, (iii) sub-aerial mud-rich debrisflows, (iv) sub-aqueous mud-rich debrisflows, (v) low energy streams that reworked abandoned fan sectors, (vi) a sandflat-playa lake system and (vii) talus slopes. The first two facies are both clast-supported conglomerate, comprise 98% of the deposit, and represent deposition on active depositional lobes and in the fan head trench. The remaining facies are the products of infrequent sedimentary processes, fan abandonment processes and marginal sub-environments. The facies assemblage in many ways mimics that of a modern-day, water-lain, arid region fan. However, the palaeolatitude of these fans was high and the climate is inferred to have been cool and wet. The near absence of sandstone and mudstone beds with few mudflows is ascribed to rapid hinterland uplift and high rates of erosion resulting in minimal chemical breakdown of source rocks in the catchments. Such high rates of erosion are in turn ascribed to a combination of frequent rainstorms and an absence of vegetation cover. 相似文献