Quaternary alluvium

Oct 1, 2020 · Alluvium was first used to describe gradual and imperceptible deposition of new earth material along rivers by floods. In the 19th century, as coarse, alluvium-like sediment in higher landscape positions was unlikely deposited by annual flooding , geologists explained those “older alluvium” deposits by the biblical deluge and named such ...

Quaternary alluvium. Older alluvium, lake, playa, and terrace deposits. from the 2010 data source metadata: The depiction of Quaternary geologic units on the original map by Jennings (1977) was simplified by the author who noted that "various surficial deposits of Quaternary age are lumped into the unit 'Q'." Since Jennings' work, subdivisions of these deposits ...

The Quaternary alluvial sequence of the Antelope Valley, California | Soils and Quaternary Geology of the Southwestern United States | GeoScienceWorld Books | …

Alluvium, undifferentiated. Unit is present in all counties. Some counties divided the alluvium into younger and older units, and some did not. For those that did not, or used other generalized terms for Quaternary rocks, the unit Qal has been used for the general undivided alluvium. Additionally, when polygons have been edited and changed to ...Quaternary Geology is mapped without regard for any organic soil layer that may overly the deposit. The Connecticut Quaternary Geology information was initially compiled at 1:24,000 scale (1 inch = 2,000 feet) then recompiled for a statewide 1:125,000-scale map, Quaternary Geology Map of Connecticut and Long Island Sound Basin1. Late Quaternary stratigraphy and sedimentation in the Ganga Alluvial Plain and the Bengal Basin have influenced arsenic contamination of groundwater. Arsenic contaminated aquifers are pervasive within lowland organic rich, clayey deltaic sediments in the Bengal Basin and locally within similar facies in narrow, entrenched river valleys within ...The quaternary sequence is further divided into Holocene, i.e., newer alluvium and Pleistocene, i.e., older alluvium [39, 40]. The central and western part of the study area has dominance of ...Quaternary alluvium; may contain some glacial deposits and colluvium in uplands Surficial sediments; Quaternary alluvial, lacustrine, eolian, and glacial-outwash deposits, undivided; Snake River Plain, and Basin-and-Range provinces (Quaternary)in Quaternary alluvium is due to Gibbs et al. (1994). The authors measured Q# in soft sediments by means of borehole measurements of shear signals generated by an air-powered source at the ground ...the Quaternary alluvium. This is comparable to the differential decay between. Gilroy no. 2 and a rock site 1.9 km away (Gilroy no. 1), as measured from the.

Gulf Coast Prairie soils formed in alluvial and marine sediments of (primarily) Quaternary age that were deposited under fluctuating sea-level conditions. The area is characterized by low local relief and dissection by rivers that flow to the Gulf of Mexico. Victoria, Laewest, Edroy, Beaumont, League, and Lake Charles soils are well-developed,Quaternary geology of northern New Jersey and the Trenton area. Subitzky , S. Geology of Selected Areas in New Jersey and Eastern Pennsylvania and Guidebook of Excursions Rutgers University Press New Brunswick, N.J 279 – 313 .Question: Figure 10-10 Geologic sketch map of an area north of the Black Hills. Qal is Quaternary alluvium; all other units are Cretaceous in age. Km is the oldest unit; Kpf is the youngest. (After W. J. Mapel, G. S. Robinson, and P. K. Figure 10-10 Geologic sketch map of an area north of the Black Hills. Qal is Quaternary alluvium; all other ...Sep 6, 2006 · Quaternary alluvium consists of gravel, sand, silt and clay of Ova creek sediments covers the Golbasi formation uncomformably. The engineering geology, groundwater level and liquefaction risk of ... Quaternary Alluvium Alluvial deposits of sand, gravel, silt, and clay. Geologic unit mapped in West Virginia: Alluvial deposits of sand, gravel, silt, and clay.Quaternary terraces and pediments along Ralston Creek and Clear Creek, near Golden, Colorado, are associated with Verdos, Slocum, Louviers, and Broadway Alluviums. ... Subdivision of the Quaternary alluvium east of the Front Range near Denver, Colorado. Geological Society of America Bulletin, 71 (1960), pp. 1541-1543. CrossRef Google Scholar ...Quaternary Geology is mapped without regard for any organic soil layer that may overly the deposit. The Connecticut Quaternary Geology information was initially compiled at 1:24,000 scale (1 inch = 2,000 feet) then recompiled for a statewide 1:125,000-scale map, Quaternary Geology Map of Connecticut and Long Island Sound Basin1.

The areas marked Quaternary Alluvium are areas underlain by unconsolidated gravel, sand, and silt sediments deposited by streams over the last 2.6 million years. The area marked Franciscan Formation is underlain by solid sedimentary, igneous, and metamorphic rocks that are over 65 million years old.Quaternary alluvium and marine deposits (Pliocene to Holocene) Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast. Quaternary sand deposits, unit 2 (inland) (Quaternary)alluvium: [noun] clay, silt, sand, gravel, or similar detrital material deposited by running water.8 de jan. de 2018 ... The Bremer River, Warrill Creek and Purga Creek alluvial systems are composed of Cenozoic to Quaternary alluvial and colluvial sediments, ...Pliocene-Quaternary older alluvium and as well as younger alluvium. The low grade Paleozoic and Mesozoic meta-morphic rocks of the region can be regarded as parts of the Afyon-Bolkardagı Zone of Okay (1986). The region had dis-˘ tinctive stratigraphic, metamorphic, deformational features and an important Alpine orogenic history.

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River, alluvial fan and landslide interactions in a tributary junction setting: Implications for tectonic controls on Quaternary fluvial landscape development (Central Anatolian Plateau northern margin, Turkey) ... Late Quaternary alluvial fans of Emli Valley in the Ecemiş Fault Zone, south central Turkey: insights from cosmogenic nuclides ...northeast on 180 m of Quaternary alluvium overlying Franciscan (Figure 1). The effect of the alluvium was to amplify both horizontal and vertical motion. Peak horizontal acceleration at station 1 was 0.13 g and peak horizontal velocity 10 cm/sec. At station 2 values of 0.26 g and 32 cm/sec were recorded.Quaternary Climate of Narmada Valley: A Case Study on Understanding Provenance, Weathering and Depositional Environment Using Alluvium Geochemistry …[1] Quaternary alluvial fans have diverse surface morphologies related to both depositional and weathering processes. Numerous studies have demonstrated that the surface expression and morphometry of alluvial fans can be used as an indicator of their relative age of deposition, but only recently has there been an effort to utilize high-resolution topographic data to differentiate alluvial fans ...Climatic response of quaternary alluvial deposits in the upper Kali Gandaki valley (West Nepal) Global and Planetary Change (2001) L.A. Owen et al. A note on the extent of glaciation throughout the Himalaya during the global last glacial maximum. Quaternary Science Reviews (2002)

Quaternary alluvial record at the Thar desert margin has been examined using the exposed succession along Mahudi, Sabarmati river, Western India. Different alluvial facies, their associations and granulometry have been studied for palaeoenvironmental recon struction. Clay mineral indices smectite/chlorite andQuaternary downcutting rate of the New River, Virginia, measured from differential decay of cosmogenic 26Al and 10Be in cave-deposited alluvium January 1997 Geology 25(2):107-110Downbasin from Vientiane to Savannakhet, a shallow Quaternary alluvium, mainly fine to coarse sand with some clay and gravel, covers Palaeozoic and Mesozoic rocks in the valley of the Mekong. Mesozoic sandstones and evaporites reappear in the Mekong valley further south beyond this Quaternary cover, locally overlain by shallow …The Late Quaternary Alluvial and Soil Stratigraphy Comprehensive studies of late Quaternary sedimentation in Greece are still rare. Instead, the subject has been dominated by the view of Vita-Finzi (1969), vigorously supported by Bintli1975, 1977), that there were only two late Quaternary alluviations, the Older and the Younger Fill.Quaternary alluvium; may contain some glacial deposits and colluvium in uplands Surficial sediments; Quaternary alluvial, lacustrine, eolian, and glacial-outwash deposits, undivided; Snake River Plain, and Basin-and-Range provinces (Quaternary) Two trenches at this site were excavated in Hennessey Shale and Quaternary alluvium. The trenches did not find convincing stratigraphic evidence of multiple Holocene faulting events; the absence of this evidence may be related to the abundant ductile deformation in the shale, which minimized the likelihood of a surface-rupturing earthquake ...The Quaternary alluvium and terrace deposits adjacent to the Rio Grande were formed by sediment deposition by the river, consisting of irregularly distributed gravels, sands, clay, and silt lenses and beds with a maximum thickness of 61 m (Alvarez and Buckner 1980, Hutchison and Hibbs 2008). Over most of the aquifer system, …Quaternary alluvium and marine deposits (Pliocene to Holocene) Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast. Quaternary sand deposits, unit 2 (inland) (Quaternary) The National Quaternary Geology task seeks to construct continuous Quaternary geologic map coverage to fulfill the mandate of the USGI and to transform …

Downstream of Fochabers, the coarse, gravelly alluvium of the Spey is on average about 6 m thick, locally ranging up to 12 m or more. Near Banff, the floodplain of the Deveron is underlain by 2 to 3 m of silt overlying 7 to 15 m of alluvial deposits including sand and gravel. The floodplain of the Ythan is underlain by 4 to 6 m of gravel ...

Late Quaternary chronostratigraphic framework of terraces and alluvium along the lower Ohio River, southwestern Indiana and western Kentucky, USA. Quaternary Science Reviews, Vol. 110, Issue. , p. ... Alluvial landform and the occurrence of paleosols in a humid-subtropical climate have an effect on long-term soil organic carbon storage ...This study describes the stratigraphical development of the Quaternary alluvial deposits in the Luni basin, Thar Desert of India. On the basis of mode of occurrence, lithofacies assemblages and overall alluvial motif, alluvial deposits have been differentiated into an older Type-1 and a younger Type-2 succession, with chronological control provided by optically stimulated …QUATERNARY ALLUVIUM. Deposits of alluvium, mainly poorly sorted sands, gravels and boulders of streams and alluvial fans, and thin discontinuous veneers of colluvium as loose rock, talus sheets and soil, cover the valley floors and lower slopes of the ranges throughout northeastern Nevada. Colluvium sheets commonly accumulate along slopes of ...When excavating a field of Quaternary alluvium (modern sediments), a layer of limestone bedrock is encountered. The limestone is found to have been intruded by an igneous dike. Both the limestone and the dike are fractured by a fault. Place these features in order from oldest to youngest: Igneous dike, limestone bedrock, quaternary alluvium, fault.Quaternary alluvium and marine deposits. Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast. State. California. Name. Quaternary alluvium and marine deposits. Geologic age. Pleistocene to Holocene. Mirjaveh is in the southeastern tip of Zahedan as a sheet of rocks that includes the Pliocene and Quaternary intermediate period. The city is on the alluvial deposits of Paykoohi. Simultaneously, the Mirjaveh includes gravel deposits with many problems. In the north, land units are in the form of high mountains. The groundwater of the Quaternary alluvium, the Upper Cretaceous Nubian sandstone and the . fractured basement rocks that form good aquifers represent the mai n source of groundwater supply for the .The quaternary alluvium deposit in the Middle Ganga Plain (MGP) consists of a thick layer of cohesionless soil. The chances of liquefaction at shallow depth in this deposit become high due to the presence of a loose state of the soil. Very few studies can be found in the literature on the large strain cyclic behaviour of soil at MGP. Therefore, this paper has been focused on modelling the ...Question: Please help When excavating a field of Quaternary alluvium (modern sediments), a layer of limestone bedrock is encountered. The limestone is found to have been intruded by an igneous dike. Both the limestone and the dike are fractured by a fault. Place these features in order from oldest to youngest: Igneous dike, limestone bedrock, quaternary

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Quaternary Geology is mapped without regard for any organic soil layer that may overly the deposit. The Connecticut Quaternary Geology information was initially compiled at 1:24,000 scale (1 inch = 2,000 feet) then recompiled for a statewide 1:125,000-scale map, Quaternary Geology Map of Connecticut and Long Island Sound Basin1.Quaternary alluvium that influence and control the groundwater oc-currence and movement are: alluvial plains on eastern and western sides of the ridge, Yamuna flood plain deposits, isolated and ...The river near Kratie has an especially noticeable alluvial character, running over a large zone of Quaternary alluvium that overlies Lower to Middle Jurassic and Triassic continental red beds, which are mainly composed of calcareous shales and sands . The river becomes alluvial after passing through Kratie until it reaches the delta .The evolution of alluvial megafans has mainly been investigated in unconfined settings; however, at the boundary of these large depositional systems, the development of fluvial channels can be affected by structural constraints with regional extent. Here we present the study of the eastern sector of the megafan of Isonzo River, in the Gulf of Trieste, where this system …detailed GIS data for the extent of Quaternary alluvium in Colorado. the only statewide product finer scale existed as a patchwork of various sources and scales. While Qal mapping existed for the Colorado Decision Support System (CDSS) Division 1 - South Platte, similar data was not readily available for the other six CDSS divisions. Data also Chang et al. applied a selection criterion involving a takeoff angle larger than 150° and a focus depth deeper than 6 km to study the thickness variations of Quaternary alluvium beneath the Lan-Yang Plain, Taiwan; other studies applied a selection criterion in which the epicentral distance must be smaller than the focal depth (Özalaybey et al ...Relative age of Quaternary alluvial fan deposits have also been found to correlate with potential for flooding. Since these units are important for evaluation of geologic hazards, the 2010 update of the geologic map includes a subdivision of Jennings "Q" into younger alluvium "Q" and older alluvium "Qoa". In general, younger ...Qao - Plains with Duplex Soils on Quaternary, or Older Sediments. Undulating to gently sloping plains on older alluvium in the southern part of the Shire, particularly near Inverleigh. The total area of 9.0 km 2, represents 1.3% of the study area. There are some similarities between Qao and the Tertiary plains of Tgs. The foot slopes are covered by Quaternary alluvium and talus. Tectonically, the study area is distributed in the middle of the Himalayas orogenic belt. Ductile deformation and nappe structures are ... ….

Downbasin from Vientiane to Savannakhet, a shallow Quaternary alluvium, mainly fine to coarse sand with some clay and gravel, covers Palaeozoic and Mesozoic rocks in the valley of the Mekong. Mesozoic sandstones and evaporites reappear in the Mekong valley further south beyond this Quaternary cover, locally overlain by shallow …iii ABSTRACT Characterization of the small-strain shear modulus and the shear wave velocity of soils and rocks is an integral component of various seismic analyses, including site classification, hazardSediments in the shallow depths (0 to ~15 m bgl) represent Quaternary alluvium, which are good aquifers with transmissivity of the order 300 m 2 ·d −1 (Raghava Rao et al., 1976). A stratigraphic section delineating different aquifers and uncertainties is prepared based on the above inferences and shown in Fig. 7 .Over late Quaternary timescales (10 2 to 10 5 years) in tectonically stable regions climate change is the dominant allogenic mechanism and, therefore, the first-order control on the morphology, sedimentology, pedologic characteristics and chronology of alluvial stratigraphic records that meet or exceed the threshold criteria for demonstrating ...Floodplain. Figure 18.5. 2: An alluvial river meanders through its floodplain (Courtesy USGS DDS21) A floodplain is the relatively flat area that borders a stream which is periodically inundated with water during high flow periods. When excess runoff causes the stream discharge to increase beyond the capacity of the channel, water spills out ...Quaternary Surficial Deposits (Aluvial Fan Task Force) California Department of Conservation. California Geological Survey. The present study focuses on the cyclic behaviour of cohesionless soil collected from the quaternary alluvium deposit at the Middle Ganga Plain (MGP). A series of strain-controlled cyclic triaxial tests have been carried out on collected soil samples at various effective confining stresses, shear strain amplitudes and motion frequencies to ... Chang et al. applied a selection criterion involving a takeoff angle larger than 150° and a focus depth deeper than 6 km to study the thickness variations of Quaternary alluvium beneath the Lan-Yang Plain, Taiwan; other studies applied a selection criterion in which the epicentral distance must be smaller than the focal depth (Özalaybey et al ...Qao - Plains with Duplex Soils on Quaternary, or Older Sediments. Undulating to gently sloping plains on older alluvium in the southern part of the Shire, particularly near Inverleigh. The total area of 9.0 km 2, represents 1.3% of the study area. There are some similarities between Qao and the Tertiary plains of Tgs. Quaternary alluvium, Older alluvium is semi cemented eroded deposited and reshaped by water to make non-marine setting. Specimens were tested in for shear strength, hardness and point load index. According to these ..., The lateral flow is from fissure karst water from Pipa Hill and Qing Hill along the topographical gradient, but the hydraulic gradient in the study area varies due to the geological setting. The heterogeneous phreatic aquifer, with overall flow from southeast to northwest, has the same pinching tendency of the Quaternary alluvial strata., Quaternary Surficial Deposits (Aluvial Fan Task Force) California Department of Conservation. California Geological Survey. , The alluvial plains of Central and North Gujarat are made up of thick Quaternary continental deposits of fluvio-marine, fluvial and aeolian origin. Showing record ... Quaternary is still little known and remains a 'grey The coastal miliolite are partly marine and partly area' for lack of age data. However, evidence points to aeolian, while the ..., The Quaternary sand and gravel of the Mississippi River Valley alluvial aquifer continue southward but are considered to be part of the coastal lowlands aquifer system. The layered sequence of aquifer and confining units that lies east and west of the alluvial plain and that is part of the Mississippi embayment aquifer system also extends ..., The quaternary sequence is further divided into Holocene, i.e., newer alluvium and Pleistocene, i.e., older alluvium [39, 40]. The central and western part of the study area has dominance of ..., Comparative uranium-thorium and thermoluminescence dating of weathered quaternary alluvium in the tropics of Northern Australia. ... (TL) age determinations of alluvial sediments in the tropics are evaluated by comparison with U/Th age determinations of pedogenic accumulations in the alluvium of the lower Gilbert River, a large fan delta in the ..., A similar difference in COV was observed between thin Quaternary alluvium throughout California (COV 1⁄4 0.25) and thin Quaternary alluvium located in west Los Angeles (COV 0.15)., Baker VR (1974) Paleohydraulic interpretation of Quaternary alluvium near Golden, Colorado. Quat Res 4: 94–112. CrossRef Google Scholar Baker VR, Ritter DF (1975) Competence of rivers to transport coarse bedload material. Geol Soc Am Bull 86: 975–978. CrossRef Google Scholar, The National Quaternary Geology task seeks to construct continuous Quaternary geologic map coverage to fulfill the mandate of the USGI and to transform …, Aug 1, 2015 · In Tunis City area, soil was classified by El May et al. (2010), according to the morphology, in three zones: (1) alluvial plains area occupied by a variety of recent quaternary alluvial deposits formed by clay, sand, silts and tuff; (2) area surrounding plains and slopes of hills are characterized by a Pleistocene to Holocene outcrops formed by clay, sand and silt, and (3) Hills areas that ... , Feb 22, 2023 · As shown in Figure 9, the stratigraphic structure within the depth of the pit survey mainly consists of the Quaternary artificial accumulation (Q4ml) layer: artificial fill; the Quaternary alluvium (Q4al + pl) layer: clay, round gravel, and powder; and the Quaternary marsh phase sediment (Q4h) layer: peaty soil and organic soil. The gravels are ... , This paper outlines Quaternary nomenclature changes to Zeller (1968) that have been adopted by the Kansas Geological Survey (KGS). The KGS formally recognizes two series/epochs for the Quaternary: the Holocene and Pleistocene. ... The Severance Formation is adopted as a new lithostratigraphic unit for thick packages of late Pleistocene alluvium ..., Quaternary alluvial deposits are the most extended outcrops in Tunis City with an area covering all the plains and relief in the study area (Fig. 1). Since the 1960s, …, The Zaghouan Plain is characterized by an important alluvial Mio-Plio-Quaternary to Quaternary aquifer system (Rekaya 1981; Ben Fraj 2016) (Figs. 1b, 3). …, The Pliocene-Pleistocene Carcar Formation and the Quaternary Alluvium are two major lithologies that rim the entire island province of Cebu. The Carcar Formation (CaF) is predominantly limestone ..., 24 de mai. de 2019 ... Journal of Quaternary Science, 32, 3. National Geographic Alluvial fan. Accessed May 17, 2019. Owen, L.A. et al. (1998) Quaternary alluvial ..., The evolution of alluvial megafans has mainly been investigated in unconfined settings; however, at the boundary of these large depositional systems, the development of fluvial channels can be affected by structural constraints with regional extent. Here we present the study of the eastern sector of the megafan of Isonzo River, in the Gulf of Trieste, where this system …, The Quaternary evolution of an alluvial fan system in the Himalayan foothills reveals two distinct phases. The Early Quaternary Siwalik system (I) and the Late Quaternary intramontane piggy-back system (II) have been studied in detail in the Subathu sub-basin of NW Himalaya (with system I followed by system II)., This aquifer is composed of coarse sand and gravel with clay intercalations. Its thickness varies between few meters in the Wadi deposits to about 100 m in the coastal areas. Figure 4 shows the depth to groundwater level in the Quaternary alluvial deposits which form the main aquifer unit of the region. The map has been prepared from water ..., SUBDIVISION OF THE QUATERNARY ALLUVIUM EAST OF THE FRONT RANGE NEAR DENVER, COLORADO GLENN R SCOTT. GLENN R SCOTT U. S. GEOLOGICAL SURVEY, FEDERAL CENTER, DENVER, COLO. ... Alluvium east of Front Range; Latitude & Longitude N39°45'00" - N39°45'00", W105°00'00" - W105°00'00" View Full GeoRef Record., Oct 17, 2023 · The Alluvium. Alluvium is a loose soil, or sediment, not fused into a rock, formed by erosion, reshaped by water in some form, and redeposited in a riverside setting or by a river. This is suitably represented by the name Alluvium meaning “to wash against”. In simple terms, the soil or sediment deposited or redeposited by continuous erosion ... , Alluvial aquifers associated with Colorado’s major river systems are unconfined and generally consist of unconsolidated silt, sand and gravel that has been deposited during the Quaternary Period by rivers. These alluvial aquifers contain groundwater stored in unconsolidated sediment along river valleys, and as a result, are often referred to ..., The MSF stands out in that it clearly displaces Quaternary alluvial fan and terrace deposits, ranging in age from early Pleistocene to as young as latest Pleistocene-early Holocene (Anderson and O’Connell, 1993). There is obvious evidence for recurrent fault movement in the form of larger fault scarps on older alluvial surfaces, but there are ..., Substantial coarse clastics were carried by the Urumqi River from the range into the Chaiwopu basin and were deposited as the Quaternary alluvial fans (Fig. 1, Fig. 2). Pleistocene aeolian loess extensively mantles several high terrace surfaces developed by this piedmont fluvial system (Yang and Qiu, 1965, Zhang, 1981, Zhou et al., 2002). 3., Question: When excavating a field of Quaternary alluvium (modern sediments), a layer of limestone bedrock is encountered. The limestone is found to have been intruded by an igneous dike. Both the limestone and the dike are fractured by a fault. Place these features in order from oldest to youngest: Igneous dike, Limestone bedrock, Quaternary ... , The upland rivers are incised 5-20 m into their late Quaternary flood plains, Valley cross-sections show two alluvial fills and two river terraces 7 (Fig. lb). , Quaternary alluvium and marine deposits. Alluvium, lake, playa, and terrace deposits; unconsolidated and semi-consolidated. Mostly nonmarine, but includes marine deposits near the coast. State. California. Name. Quaternary alluvium and marine deposits. Geologic age. Pleistocene to Holocene., Eucalyptus tereticornis woodland on Quaternary alluvium: Structure code: Woodland: VMA structure category: Sparse: Description: Eucalyptus tereticornis woodland. Eucalyptus crebra and E. moluccana are sometimes present and may be relatively abundant in places, especially on edges of plains and higher level alluvium., Mirjaveh is in the southeastern tip of Zahedan as a sheet of rocks that includes the Pliocene and Quaternary intermediate period. The city is on the alluvial deposits of Paykoohi. Simultaneously, the Mirjaveh includes gravel deposits with many problems. In the north, land units are in the form of high mountains. , Florida. Alluvium (Pleistocene/Holocene) Alluvium - Undifferentiated Quaternary Sediments - Much of Florida's surface is covered by a varying thickness of undifferentiated sediments consisting of siliciclastics, organics and freshwater carbonates. Where these sediments exceed 20 feet (6.1 meters) thick, they were mapped as discrete units., The groundwater of the Quaternary alluvium, the Upper Cretaceous Nubian sandstone and the . fractured basement rocks that form good aquifers represent the mai n source of groundwater supply for the ., QUATERNARY ALLUVIUM. Deposits of alluvium, mainly poorly sorted sands, gravels and boulders of streams and alluvial fans, and thin discontinuous veneers of colluvium as loose rock, talus sheets and soil, cover the valley floors and lower slopes of the ranges throughout northeastern Nevada. Colluvium sheets commonly accumulate along slopes of ...