Gravel Deposits Research Articles

Development of the Truckee River terraces on the northeastern flank of the Sierra Nevada

The distribution and elevation of the abandoned strath terraces along the Truckee River in the Carson Range on the eastern flank of the Sierra Nevada are mapped and quantified with measurements from Lidar accompanied by field survey. Each mapped strath terrace is formed by incision into the Hunter Creek Sandstone and deposition of fluvial gravel by the Truckee River. The gravel contains granitic boulders sourced from the glaciated headwaters of the Truckee >20 km upstream from the terraces and display boulders ranging from 4 to 12 m in dimension, in comparison to the <1 m dimension of boulders observed in the bedload of the modern Truckee River. Be-10 terrestrial cosmogenic nuclide (TCN) surface exposure dating places limits on the age distribution of the strath terraces. The terrace sediments are suggested to be glacial outwash deposits, temporally linked with glacial cycles, and to record an average of ~0.3 mm/a tectonic uplift with respect to the Reno Basin over the last ~350 ka. Building upon earlier studies, the observations collected here increase the number of terrace levels previously mapped along the Truckee, provide initial quantitative bounds on the age of their formation, and further point to tectonic uplift as an important component in preserving this most extensive suite of strath terraces along the eastern flank of the Sierra Nevada.

Oligocene-Neogene lithospheric-scale reactivation of Mesozoic terrane accretionary structures in the Alaska Range suture zone, southern Alaska, USA

AbstractTerrane accretion forms lithospheric-scale fault systems that commonly experience long and complex slip histories. Unraveling the evolution of these suture zone fault systems yields valuable information regarding the relative importance of various upper crustal structures and their linkage through the lithosphere. We present new bedrock geologic mapping and geochronology data documenting the geologic evolution of reactivated shortening structures and adjacent metamorphic rocks in the Alaska Range suture zone at the inboard margin of the Wrangellia composite terrane in the eastern Alaska Range, Alaska, USA. Detrital zircon uranium-lead (U-Pb) age spectra from metamorphic rocks in our study area reveal two distinct metasedimentary belts. The Maclaren schist occupies the inboard (northern) belt, which was derived from terranes along the western margin of North America during the mid- to Late Cretaceous. In contrast, the Clearwater metasediments occupy the outboard (southern) belt, which was derived from arcs built on the Wrangellia composite terrane during the Late Jurassic to Early Cretaceous. A newly discovered locality of Alaska-type zoned ultramafic bodies within the Clearwater metasediments provides an additional link to the Wrangellia composite terrane. The Maclaren and Clearwater metasedimentary belts are presently juxtaposed by the newly identified Valdez Creek fault, which is an upper crustal reactivation of the Valdez Creek shear zone, the Late Cretaceous plate boundary that initially brought them together. 40Ar/39Ar mica ages reveal independent post-collisional thermal histories of hanging wall and footwall rocks until reactivation localized on the Valdez Creek fault after ca. 32 Ma. Slip on the Valdez Creek fault expanded into a thrust system that progressed southward to the Broxson Gulch fault at the southern margin of the suture zone and eventually into the Wrangellia terrane. Detrital zircon U-Pb age spectra and clast assemblages from fault-bounded Cenozoic gravel deposits indicate that the thrust system was active during the Oligocene and into the Pliocene, likely as a far-field result of ongoing flat-slab subduction and accretion of the Yakutat microplate. The Valdez Creek fault was the primary reactivated structure in the suture zone, likely due to its linkage with the reactivated boundary zone between the Wrangellia composite terrane and North America in the lithospheric mantle.

Problems of 14C dating in fossil soils within tectonically active highlands of Russian Altai in the chronological context of the late Pleistocene megafloods

A complicated tectonic and sedimentation history of the high-mountainous south-eastern part of Russian Altai predetermined the presence of sources of ancient organic matter in the region. During the Pleistocene these deposits were affected by various exogenous processes that leads to mixing of young and old carbon in a unique (for each sample) ratio and strongly affects the results of radiocarbon dating. This paper presents the results of multidisciplinary investigations of pedosedimentary sequences and discusses 14C dating of heterochronous organic matter in paleosols of two locations within the Chuya basin in the chronological context of the late Pleistocene megafloods.In the Kamsug valley reasonable evidence of the oldest (Pleistocene) paleosols in the SE Altai is described for the first time. The mineral composition of sediments and the results of pollen analysis argue for a short-distant redeposition of the Paleogene-Neogene parental substrate. Later it was transformed by Pleistocene pedogenesis: cryogenic processes, particularly solifluction, redox fluctuations resulted in redistribution of Fe and Mn. The analysis of available radiocarbon dates indicates that the contamination of the samples by extraneous carbon and the insufficient data about the features of organic matter of the studied soils don't allow to draw a definite conclusion about the time of the Pleistocene pedogenesis in the region. The presented OSL age 37.0 ± 3.1 ka (GdTL 3424) predates pedogenesis in this location, as well as the last ice-dammed lake formation in the Chuya basin and its further cataclysmic draining followed by the deposition of cross-bedded gravels and pebbles. In the neighbouring Yamanterek valley radiocarbon dating result for paleosol returns erratic (aged) date due to the influx of ancient organic matter. Similarly, this date cannot serve as the upper chronological limit of ice-dammed lakes existence in the Chuya depression. The radiocarbon ages (9.7–11.3 ka cal BP) of charcoals from the underlying lens of humus sands postdate the last ice-dammed lake with the water level at least 1980 m a.s.l.It was demonstrated that short-distant redeposition of the Paleogene-Neogene sediments in the region preserves their main mineralogical and paleontological features. It gives an opportunity to recognise such redeposited sediments which contain geological carbon. Meanwhile the redeposition followed by pedogenesis introduces younger organic matter. Diagenesis of such originally different organic matter contributes the final pool of organic carbon and results in the formation of heterogenous and heterochronous organic matter. This should be taken into account while 14C dating and interpreting the obtained results.

Sedimentary characteristics of muddy deposits in sandy braided fluvial system: A case study from outcrops of the Jurassic Yungang Formation in the Datong Basin, Central China

The sandbodies within braided fluvial deposits are important reservoirs for the oil fields in China, and they usually have complex sedimentary architecture. A lot of research has been concentrated on characterizing the architecture of the sandbodies. Based on the observation that muddy deposits are commonly well preserved in fluvial deposits, we find that understanding the contact relationship between the muddy deposits and surrounding sand bodies can help characterize the depositional process of sandy braided fluvial systems. We have determined the effectiveness of this idea by characterizing a well-exposed outcrop of sandy braided fluvial system in the Datong Basin, Shanxi Province of China. We first define six muddy lithofacies by integrating the thickness of the muddy deposits, the morphology of the muddy deposit, and the lithofacies of surrounding sand deposits. The six muddy lithofacies include floodplain muddy deposits between intermittent channel complex, lateral covering muddy deposits and fall-silt seam muddy deposits between migrated bar complex, muddy gravel deposits in erosional bar complex, and channel-fill muddy deposits and gully-fill muddy deposits in abandoned bar complex. We then analyze the depositional environments according to the defined muddy lithofacies. We finally build the architecture of the outcrops by integrating the lithofacies of sand deposits and evolution of the depositional environments deduced from the muddy lithofacies.

The sediment record of the Unicorn Cave, southern Harz Mountains, Germany

We demonstrate the utility of a multi-pronged approach to geomorphological studies. We show how the synthesis of results from 3-D imaging, varied geotechnical methods, and dating, reveals hitherto unknown features of a cave and of its sediment infill, and elucidates its geomorphological history. The Unicorn Cave (Einhornhöhle, southern Harz Mountains, Germany), long famous for its cave bear, lion, and mammoth fossils, is a dry vadose trunk cave high above base level, characterized by large rooms connected by shallow passages, and filled with sediments up to 40 m thick. The sediment is an archive for natural and anthropogenic environmental change: the succession of river gravels, breccia, and silts and sands provides a paleo-geomorphic and climatic archive; while human artefacts from the Paleolithic period provide information about early settlement phases. Here we derive a detailed description of the Unicorn Cave and its sediment infill by utilising several sources: (i) We synthesise data from the literature into a comprehensive picture of the sediment infill; (ii) We present new geophysical measurements of the sediments in the large room Leibnizhalle, and discuss these new measurements in view of our older findings; (iii) We map the larger chambers with the photogrammetric structure-from-motion method to build three-dimensional models; (iv) We present new age estimates from speleothem samples in the cave and discuss them with other, published, age estimates. Finally we use our newly collected evidence to reconstruct the evolution of the entire Unicorn Cave (including the newly-revealed, not-yet-accessible passages and their pristine sediment infill, as yet undisturbed by fossil hunters). The main period of speleogenesis ended with base-level incision in the mid-Pleistocene; the deposition of basal river gravels, probably in the late Cromerian, was followed by a sequence of clays and loams, capped by speleothem at ~MIS 3; the dates suggest at least two bone beds (MIS 3, and MIS 5e), along with bone material older than MIS 7.

Morpho-sedimentary and stratigraphic characteristics of the 2000 Yigong River landslide dam outburst flood deposits, eastern Tibetan Plateau

Sedimentary characteristics of landslide dam outburst flood deposits are distinct from those of rainfall flood deposits due to their very high hydraulic energy and sediment concentration. While they have been studied well in geological record, investigations of modern outburst flood deposits are relatively rare. Well-preserved flood deposits and landforms caused by the June 2000 landslide dam outburst flood in the Yigong River, eastern Tibet provide an opportunity to evaluate such sedimentological response to a high energy modern event. The sedimentary characteristics of boulder bars and channel evolution over c. 17 km downstream of the breach were investigated by field survey and remote sensing interpretation. The results show that the post-flood channel migrated downstream and increased in curvature. The bar shape is very little changed toward downstream, but the bar area shows a fluctuating decrease. Poorly sorted accumulations composed of massive granular gravels and boulders near the breach indicate sediment-rich bedload depositing processes occurred during rapid rising stage flows. In contrast, there are eddy bars and deposition of fine gravel with horizontally bedded laminations 17 km downstream of the dam, suggesting suspended sediment dominated deposition with a rapid loss of transport capacity. Comparison with previous hydrodynamic simulations indicates that the rates of the rising stage and the falling stage strongly affect the sedimentary characteristics of boulder bars and slackwater deposits.

Earth pressure balance shield tunneling in sandy gravel deposits: a case study of application of soil conditioning

Earth pressure balance shield (EPBS) tunneling techniques originally developed for fine-grained soil deposits have been adopted in a growing number of tunneling projects where challenging geological conditions, such as those with coarse-grained soils, are encountered. However, successful application of EPBS tunneling with soil conditioning could fully address technical challenges during tunneling in coarse-grained strata, such as tunnel face instability, blocking or clogging, severe wear of cutting tools, and low-effiency tunneling. In this paper, a comprehensive case study is presented that EPBS tunneling was successfully used in Beijing Metro Xijiao line with the aid of soil conditioning, where sandy gravel deposit with unfavorable particle size distribution, poor flowabilty, high permeability, and high abrasiveness was encountered. A series of both laboratory and in situ testing was carried to evaluate foaming agents, develop soil conditioning schemes, and verify their effectiveness of modifying the sandy gravel for EPBS tunneling purpose. The homogeneity, workability, permeability, and abrasivity of foamed soils were tested in the laboratory to develop soil conditioning schemes while the effectiveness of soil conditioning schemes during in situ tunneling was further evaluated with slump test and visual inspection. Parameters, such as foam expansion ratio (FER), half-life period, and foam injection ratio (FIR), which are used to evaluate the behavior of foaming agent and performance of conditioning schemes and tunneling schemes, were also discussed.

Remote sensing and three-dimensional photogrammetric analysis of glaciofluvial sand and gravel deposits for aggregate resource assessment in McHenry County, Illinois, USA

Sand and gravel deposits, one of the most common natural resources, are used as aggregates mostly by the construction industry, and their extraction contributes significantly to a region's economy. Thus, it is critical to locate sand and gravel deposits, and evaluate their quantity and quality safely and quickly. However, information on aggregate resources is generally only available from conventional two-dimensional (2-D) geologic maps, and direct field measurements for quality analysis at outcrops are time consuming and are often not possible due to safety concerns, or simply because exposures are too difficult to access. In this study, we presented a methodology to locate and evaluate aggregate resources, including the traditional methods of field surveying and borehole investigation for the entire McHenry County, Illinois, USA and new three-dimensional (3-D) photogrammetric models and remote sensing technologies at an active gravel pit. Thus acquired data sets allowed us to obtain key information for successful aggregate resource management: spatial occurrence, thickness, texture, paleocurrents, lithology and land use compatibility. In addition, remote sensing and photogrammetric techniques allowed for very quick and safe assessment of fundamental properties like particle size, paleocurrent direction and sorting, especially in inaccessible and/or unsafe outcrops. In summary, this paper demonstrated how remote sensing and photogrammetric technology can improve the efficiency and safety in resource assessment strategies, and the methodology used in our study can be applied to the development of autonomous mining and resource asset management elsewhere.

Changes of Technosol properties and vegetation structure along a chronosequence of dredged sediment deposition in areas with alluvial gold mining in Colombia

PurposeAlluvial gold mining leaves a vast amount of dredged sediment that covers the natural soil, destroys riparian ecosystems, and impacts riverbeds and valleys. In Colombia, more than 80,000 ha are covered by dredged sediment. Technosols developed from such deposits undergo strong transformations during the early stages of formation due to the diverse nature of the constituents. The aims of this study are (i) to investigate changes in soil morphological and physicochemical properties at early stages of pedogenesis, (ii) to estimate the variability of size structure distribution of the new plant cover as affected by the time period since establishment and deposit type, and (iii) to determine which soil parameters correlate best with the size structure distribution of vegetation.Materials and methodsSoil characterization through morphological and physicochemical analysis was conducted on Technosols developed from gravel and sandy deposits of different ages (0–12 years). A vegetation survey was conducted to measure tree dimensions and identify the most common species. Data were analyzed using non-parametric tests to avoid the loss of information due to data smoothing.Results and discussionThe studied Technosols are subject to processes similar to those occurring in natural parent materials such as mineral transformations, changes in redox conditions, organic matter accumulation in the topsoil, and a rapid differentiation of horizons. However, the Technosols in our study sites show an unusually fast development not often observed in natural soils, with drastic changes observed at very early stages of formation. Gravel deposits offer more favorable conditions for plant growth, and marked changes in pedogenic processes can be observed compared with sandy deposits, which are reflected in changes of chemical properties.ConclusionsFactors such as the technology used for mining and the continuous deposition of dredged sediments in a cumulative way during the exploitation period, as well as the disturbances after deposition, result in a high diversity of constituents and high heterogeneity of dredged sediment deposits. Gravel and sand deposits, originated from the same sections of the river and after similar separation processes for ore extraction, undergo divergent pedogenic processes at different rates, which could be explained by a remarkable effect of particle size distribution. For vegetation establishment, the selection of tree species should be based on their capacity for nutrient pumping through deep rooting to sequester carbon and to adapt morphologically to heterogeneity in nutrient availability by growing roots in nutrient-rich zones.

High resolution 3D subsurface mapping using a towed transient electromagnetic system ‐ tTEM: case studies

ABSTRACTGeophysical methods are routinely applied for investigation of near surface in areas of infrastructure, water supply, artificial infiltration, farming, waste deposits, construction, etc. A new towed transient electromagnetic tool, called ‘tTEM’, provides rapid, efficient, high‐resolution imaging of subsurface hydrogeology, and can deliver densely spaced profiles of resistivity. These profiles can be used to map a three‐dimensional subsurface in high resolution. In this paper, we present three case studies where the towed transient electromagnetic system was used to map the subsurface at the hectare scale. In the first case, we used towed transient electromagnetic to map raw materials in the northern Jutland, Denmark. The survey was carried out to map possible sand and gravel deposits. In the towed transient electromagnetic models, the potential sand/gravel targets are identified as high resistive bodies in the top 30 m. These bodies can have significant lateral variation at scales much less than one hundred metres. In the second case study, towed transient electromagnetic was used to map the thickness of a protecting clay layer above an aquifer in Vildbjerg, a town in the central part of Denmark. Results show that the overlying clay layer has sufficient thickness (&gt;15 m) to protect the underlying aquifer from pesticide pollution in the area. Finally, in the third case study, we used towed transient electromagnetic for mapping geology in the vicinity of a landfill. The inversion results reveal a hitherto unknown buried valley‐like feature within the top 30 m of the subsurface that was not identified by older, regional TEM surveys – a feature that can have significant impact on the water flow.

Zoophycos in storm-affected environments: a case study from lower Maastrichtian deposits of the Mateur-Beja area (Northern Tunisia)

The lower Maastrichtian deposits of the Mateur-Beja area in northern Tunisia are mainly composed of fine-grained marl and limestone alternations occasionally interbedded by coarse-grained calcarenites and gravel deposits. In the coarse-grained intervals sedimentary structures are indicative of storm-induced high-energy currents in an outer ramp to slope setting and of local reworking by bottom currents in the basin. In deeper environments, fine-grained sediments accumulated mainly while settling from storm-induced suspensions. The lower Maastrichtian deposits contain abundant Zoophycos exhibiting two main morphotypes, skirt-shaped Zoophycos in deposits around storm-wave base and tongue-shaped Zoophycos in somewhat deeper sediments. The types differ in burrow architecture, morphology of lobes, and size of structural elements. These differences are attributed to different behavioral programs modulated by the availability of benthic food that decreased seaward. Storm-affected environments seem to be a prerequisite for these Zoophycos-producers to choose their habitat.

Seabed erosion and deposition related to the typhoon activity of the past millennium on the southeast coast of China

AbstractCatastrophic events often interrupt long‐term Earth surface processes. In coastal areas, although millennial‐scale trends of climatic and sea‐level changes determine the trajectory of sedimentary landform evolution, storm and/or tsunami activity can cause abrupt changes in depositional conditions that may alter the long‐term sedimentary processes. Here, we report a sedimentary hiatus that is widely observed from the late Holocene sedimentary sequence at the seabed along the southeast China coast. This hiatus was discovered by close temporal sedimentary and radiocarbon dating analyses of a seabed sedimentary sequence in the mouth area of the Pearl River estuary. The results suggest that a couple of metres in the middle to late Holocene sediment at the seabed were eroded by a catastrophic event happening c. 1000–800 cal. Years BP. In theory, a mega‐tsunami generated from the Manila Trench could have caused such erosion at the seabed, but there is a lack of direct geological and historical evidence to support such a hypothesis. Much more likely, a super‐typhoon struck the coast and caused the erosion. This hypothesis is strongly supported by the region's historical and geological records, which suggest a period characteristic of intense typhoons ranging from the Medieval Warm Period to the climate transition phase (c. 1000–600 cal. Years BP). During the subsequent Little Ice Age, deposition of sandy sediment continued, suggesting frequent but weaker typhoon activity. Over the past two centuries the deposition of sandy sediment and gravels began, implying the beginning of a phase of intensifying typhoon conditions, possibly a result of the recent warming climate. © 2020 John Wiley &amp; Sons, Ltd.

Intensive Cultural Resources Survey of the Proposed West Fork of the San Jacinto River South Drainage Channel Phase 3 Project, Montgomery County, Texas

Intensive Cultural Resources Survey of the Proposed West Fork of the San Jacinto River South Drainage Channel Phase 3 Project, Montgomery County, Texas

Pliocene short-term climate changes preserved in continental shallow lacustrine-palustrine carbonates: Western Opache Formation, Atacama Desert, Chile

AbstractMultiple climate proxies indicate episodic changes in moisture levels within an ∼1 Ma duration (early–mid Pliocene) interval. Limestones within the Opache Formation, Calama Basin, Atacama Desert region, Chile, contain evidence for wetter and drier periods on short time scales. Proxies include carbonate lithological changes, paleontology (stromatolites, oncolites, gastropods, ostracods and diatoms), O and C stable isotopes, geochemistry, and mineralogical changes (aragonite, calcite, Mg-calcite, dolomite and gypsum) throughout a 30 m stratigraphic section. Stromatolite fossil cyanobacteria dark and light laminations and mesohaline to hypersaline diatom species suggest Pliocene annual seasonality. Short-term changes between wetter and drier conditions indicate that at least this part of the Atacama region was experiencing relatively rapid early–mid Pliocene climate instability. The predominance of limestone in the Opache Formation, in contrast to the 1500 m of Oligocene-Miocene siliciclastic conglomerates and sandstones, interpreted as arid climate alluvium, that underlie it, indicates a shift from arid or hyperarid climate to a semi-arid climate. Semi-arid conditions promoted limestone deposition in a shallow lacustrine-palustrine environment. In this setting, events such as storms with associated surface water flow, erosion, siliciclastic sand, gravel, and intraclast deposition, coupled with significant biological activity, represent sedimentation during more humid periods in a shallow lacustrine depositional environment. In contrast, limestone characterized by mudcracks, Navicula diatoms, and vadose syndepositional cementation, reflect periods of enhanced evaporation, water shallowing, and episodic desiccation, characteristic of a palustrine depositional system. These facies shifts, in conjunction with geochemical and isotopic proxy evidence, yield a sedimentary record of wetter and drier climate shifts.

Wadi gravel – a new concrete aggregate in Qatar: Part 2 –Alkali aggregate reactivity

Deposits of Wadi gravel are available in many parts of the Gulf region, but not widely utilized as aggregate for concrete, mainly due to the possibility of internal sulfate attack, plus the perceived risk of alkali aggregate reactivity (AAR). This paper describes the investigations for AAR of the Wadi gravel in this case, as part of the wider study described in Part 1 of this paper. Wadi gravel from the Mekaines site in Qatar was subjected to petrographic analysis, plus the gel-pat and accelerated mortar-bar test methods. The AAR potential was found to be low to normal. The accelerated mortar-bar test exhibited ‘innocuous’ behaviour after 14 days of immersion in alkali solution. When separately testing the constituent rock types of the Wadi gravel, limestone and quartz returned innocuous results, while rhyolite, granite and quartzite returned potentially alkali silica reactive (ASR) results and some reaction was confirmed using post-expansion petrographic examination. Wadi gravel was classified as potentially reactive in the RILEM AAR-4.1 accelerated concrete prism test, but of ‘low reactivity’ in the BS 812-123 test over the longer period of 12 months. Overcoming the potential problems of gypsum content and AAR successfully provides a valuable local resource of Wadi gravel aggregate for concrete.

Nonlinear Flow Behavior in Packed Beds of Natural and Variably Graded Granular Materials

Under certain flow conditions, fluid flow through porous media starts to deviate from the linear relationship between flow rate and hydraulic gradient. At such flow conditions, Darcy’s law for laminar flow can no longer be assumed and nonlinear relationships are required to predict flow in the Forchheimer regime. To date, most of the nonlinear flow behavior data is obtained from flow experiments on packed beds of uniformly graded granular materials (Cu = d60/d10 < 2) with various average grain sizes, ranging from sands to cobbles. However, natural deposits of sand and gravel in the subsurface could have a wide variety of grain size distributions. Therefore, in the present study we investigated the impact of variable grain size distributions on the extent of nonlinear flow behavior through 18 different packed beds of natural sand and gravel deposits, as well as composite filter sand and gravel mixtures within the investigated range of uniformity (2.0 < Cu < 17.35) and porosity values (0.23 < n < 0.36). Increased flow resistance is observed for the sand and gravel with high Cu values and low porosity values. The present study shows that for granular material with wider grain size distributions (Cu > 2), the d10 instead of the average grain size (d50) as characteristic pore length should be used. Ergun constants A and B with values of 63.1 and 1.72, respectively, resulted in a reasonable prediction of the Forchheimer coefficients for the investigated granular materials.

Processes controlling river-mouth lagoon dynamics on high-energy mixed sand and gravel coasts

The river mouth lagoons of New Zealand's gravel-bed braided rivers are highly dynamic, responding to changes in waves and river flows at timescales of hours and days to years. Unlike other freshwater-dominated coastal wetlands and lagoons, they exist along open coasts that are typically retreating with cliffed hinterlands. These lagoons are common on New Zealand's high energy, coarse sediment coastlines and are known locally as ‘hāpua’. This paper employs field observations from the Hurunui hāpua, to investigate the main processes controlling the dynamics of hāpua lagoons. Based on two years of time-lapse imagery, plus concurrent wave, river flow and sea level data an improved conceptual model of lagoon dynamics was developed. The model describes how onshore bar migration of river sourced gravel and sand drives initial constriction/offsetting of the river mouth following floods. It also explains how gravel deposition in the lagoon reduces the threshold flow required to cause primary breach of the barrier opposite the point the river enters the lagoon. Three processes are identified which affect lagoon width: wave overwashing of the gravel barrier narrows the lagoon; migration of the highly dynamic lagoon outlet channel ‘resets’ the barrier position to seaward; and river floods occurring while the outlet channel is offset from the river flush sediment from the lagoon system, eroding its bed and banks. Both processes affecting lagoon widening rely on lagoon outlet channel migration, indicating that outlet channel dynamics are an important control on lagoon size.

Stuck in a loop: investigating fabric patterns in the Stone Age gravel sequence at Canteen Kopje, Northern Cape Province, South Africa

Canteen Kopje has long been known for its alluvial diamond-bearing gravel deposits, and historically these have featured frequently in archaeological literature over the last century. Studies have shown the site preserves a stratified gravel sequence with assemblages of Fauresmith mixed into the upper gravels, Victoria West Acheulean (1.2 ± 0.07 Ma) and two Early Acheulean assemblages (1.51 ± 0.8 Ma and > 1.51 Ma). Although previous geomorphological studies provide an understanding of site formation, most recently describing the gravels as a splay deposit at the terminal point of a palaeo-channel, or loop, there have been debates regarding their origin and whether they represent colluvial and/or alluvial deposition. This palaeo-channel facilitated the interaction between two nearby koppies and the palaeo-Vaal River, which subsequently influenced the nature, composition and character of the gravel deposits found across the site. Yet no study has investigated the visibly dipping surface of the gravels, nor sought to explain gravel fabric patterns that are preserved in exposed sequences. Through recording fabric data, this study confirms that the gravels retain an easterly dip direction, which provides strong evidence for the east-to-west flow of water from the upstream direction of the palaeo-channel. These findings challenge earlier models suggesting the upper gravels at Canteen Kopje are colluvial, and have implications for understanding the preserved Earlier Stone Age assemblages. This research also provides a better understanding of geomorphological processes involved in site formation and investigates the overall role that colluvial processes have played at Canteen Kopje.

High-Terrace Chert-Gravel Deposits in the Toledo Vicinity, Chase County, Kansas

This study examines high-terrace chert-gravel deposits preserved in several locations near and north of Toledo at the eastern edge of the Flint Hills in Chase County, Kansas. High-terrace gravel deposits are situated in ascending steps north of the Cottonwood River valley at three levels from approximately 90 to 150 feet (×28-45 m) above the Cottonwood River channel. All deposits contain exotic quartzite pebbles and represent the Old Osage River, which gradually shifted southward as it eroded into the modern valley. Assuming a late Pliocene age for the highest terrace gives a vertical incision rate of 1.5 cm/1000 years and a lateral migration rate of 2.2 m/1000 years. The Toledo vicinity provides confirmation for the asymmetric history of valley incision presumably due to regional crustal tilting downward to the south.

Estimation of fast groundwater flow velocity from thermal response test results

This study proposes a practical approach for the simultaneous determination of both the groundwater velocity and the effective thermal conductivity of the soil by using the moving line source theory. It is especially the process for verifying that the theory can be applied to the area where the groundwater velocity exceeds 100 m/y. Thermal response test (TRT) is carried out in Kazuno City, Japan having alluvial gravel deposits of 100 m in its depth. A borehole thermal resistance is calculated by a numerical simulation considering the effect of the groundwater velocity under the condition in which an inside borehole was filled with the porous material having a high permeability. A radius of an equivalent single pipe instead of the borehole radius is applied to the calculation model to calculate the circulating fluid temperature. The method can calculate the temperature variations of the equivalent pipe wall, reflecting a grout thermal resistance affected by the groundwater velocity. The groundwater velocity and the effective thermal conductivity of the soil are determined by using root mean square error between the calculated results and the TRT data. As a result, the groundwater velocity and the effective thermal conductivity of soil calculated by the moving line source theory were 120 m/y and 4.7 W/(m K), respectively.