Transport Histories Research Articles

Automated determination of transport and depositional environments in sand and sandstones

As sand moves across Earth's landscapes, the shapes of individual grains evolve, and microscopic textures accumulate on their surfaces. Because transport processes vary between environments, the shape and suite of microtextures etched on sand grains provide insights into their transport histories. For example, previous efforts to link microtextures to transport environments have demonstrated that they can provide important information about the depositional environments of rocks with few other indicators. However, such analyses rely on 1) subjective human description of microtextures, which can yield biased, error-prone results; 2) nonstandard lists of microtextures; and 3) relatively large sample sizes (>20 grains) to obtain reliable results, the manual documentation of which is extremely labor intensive. These drawbacks have hindered broad adoption of the technique. We address these limitations by developing a deep neural network model, SandAI, that classifies scanning electron microscope images of modern sand grains by transport environment with high accuracy. The SandAI model was developed using images of sand grains from modern environments around the globe. Training data encompass the four most common terrestrial environments: fluvial, eolian, glacial, and beach. We validate the model on quartz grains from modern sites unknown to it, and Jurassic-Pliocene sandstones of known depositional environments. Next, the model is applied to two samples of the Cryogenian Bråvika Member (of contested origin), yielding insights into periglacial systems associated with Snowball Earth. Our results demonstrate the robustness and versatility of the model in quickly and automatically constraining the transport histories recorded in individual grains of quartz sand.

The influence of topography and transport history on the composition of clastic deposits from the Jurassic Tlaxiaco basin, southern Mexico: limitations on the use of mineral and chemical indices as proxies for paleoclimate

ABSTRACT The mineral and chemical composition of clastic deposits is commonly used as a proxy for reconstructing the climatic history of the Earth. A mineralogical and chemical study of clastic deposits from the Jurassic Tlaxiaco basin of southern Mexico illustrates that the entire sedimentary system in which detritus is generated, subaerially transported, and deposited exerts a major control on the composition of sedimentary rocks, placing some constraints on the use of mineral and chemical indices as paleoclimatic proxies. Since clastic deposits of the Tlaxiaco basin were formed under similar humid climatic conditions, but in sedimentary systems with different topography and transport histories, they represent a natural laboratory for testing the control that these parameters exert on the composition of clastic rocks. Our petrographic and chemical results show that, in sedimentary systems associated with low relief and in which detritus had the possibility of being temporarily stored in floodplains and meandering bars, parent rocks and the derivative detritus interacted with weathering fluids over a long time, producing clastic deposits with composition that is representative of the weathering conditions and climate of the region. On the other hand, in environments associated with steep and tectonically active relief, the rates of sediment transport and burial exceed the rate at which weathering can generate detritus, producing sedimentary deposits with composition that largely underestimates potential weathering and provide unreliable information on climate. Mineral and chemical indices should be considered as reliable paleoclimate proxies only when sedimentological data indicate that the sedimentary system allowed sediment interaction with weathering fluids over a long time.

Differential bleaching of quartz and feldspar luminescence signals under high-turbidity conditions

Abstract. Sediment burial dating using optically stimulated luminescence (OSL) is a well-established tool in geochronology. An important but often inapplicable requirement for its successful use is that the OSL signal is sufficiently reset prior to deposition. However, subaqueous bleaching conditions during fluvial transport are vastly understudied; for example the effect of turbidity and sediment mixing on luminescence bleaching rates is only poorly established. The possibility that slow bleaching rates may dominate under certain transport conditions led to the concept that OSL could be used to derive sediment transport histories. The feasibility of this concept is still to be demonstrated, and experimental set-ups are still to be tested. Our contribution to this scientific challenge involves subaquatic bleaching experiments, in which we suspend saturated coastal sand of Miocene age in a circular flume and illuminate it for discrete time intervals with natural light. We record the in situ energy flux density received by the suspended grains in the UV-NIR frequency range by using a broadband spectrometer with a submersible probe. Our analysis includes pre-profiling of each sample following a polymineral multiple signal (PMS) protocol. Using the PMS, the quartz-dominated, blue-stimulated luminescence signal at 125 ∘C (BSL-125) decays slower than the K-feldspar-dominated, infrared-stimulated luminescence signal at 25 ∘C (IR-25) even under subaerial conditions. The BSL-125 from purified quartz shows the opposite behaviour, which renders the PMS unreliable in our case. We find a negative correlation between suspended-sediment concentration and bleaching rate for all the measured signals. For outdoor bleaching experiments we propose to relate the measured luminescence dose to the cumulative received irradiance rather than to the bleaching time. Increases in the sediment concentration lead to a stronger attenuation of the UV–blue compared to the red–NIR wavelength. This attenuation thereby follows an exponential decay that is controlled by the sediment concentration and a wavelength-dependent decay constant, λ. As such λ could potentially be used in numerical models of luminescence signal resetting in turbid suspensions.

Deciphering organic matter distribution by source-specific biomarkers in the shallow Taiwan Strait from a source-to-sink perspective

Sedimentary organic matter (OM) in coastal systems is inherently diverse, often with multiple particulate sources and transport histories. The Taiwan Strait (TS) is a typical shallow conduit region, linking the East and South China Seas. Strong ocean currents, coastal upwellings, distal large rivers, and proximal small mountainous rivers all influence the distribution of OM in the TS. We investigated the covarying patterns in the distribution of gain size classes of sand, silt, and clay; terrestrial-sourced biomarkers (n-C27+29+31 alkanes, n-C26+28+30 fatty acids (FAs), and n-C28+30+32 alkanols); marine-sourced biomarkers (phytoplankton-derived alkenones, brassicasterol, dinosterol, and zooplankton-derived cholesterol) in sea floor sediment; indicator satellite-derived primary production (Chl-a); and water-mass indicator (sea surface temperature, SST). We used an empirical orthogonal/eigen function (EOF) analysis to distinguish the influence of four hypothetical sources that entered the TS through the north, south, west, and east boundaries. Results show that input sources from the south-bound ZMCC (Zhejiang-Fujian Coastal Current) and north-bound SCSWC (South China Sea Warm Current) had the dominant influence on the OM distributions buried in the TS. Input sources via river plumes on lateral boundaries and upwellings in the TS were the secondary factors that affected the sedimentary OM distribution. Within this source-to-sink system of multiple sources and transport processes, silt and clay were the major carriers of the OM signals. Terrestrial biomarkers and primary production (Chl-a) were associated with the two major current systems and river plumes along the edge of TS. Marine biomarkers were associated with upwellings in the interior of the TS. Our finding points out that the physical systems of ocean currents, river plumes, and upwelling not only determine the distributions of biomarkers in the TS but also determine the diversity of OM in the TS.

Spotlight on the traveller: Individual experiences of routine journeys

All travel generates a range of feelings, responses and emotions that can be stimulated by many factors but recovering such responses to everyday travel in the past is difficult. Few conventional sources provide information on the travellers’ experiences of movement and, not surprisingly, most transport histories focus mainly on matters of infrastructure, usage, and technological change. In contrast, contemporary mobilities studies that can talk directly to those who travel do explore the lived experiences of mobility in some detail. This paper shows how, by using a range of life writing drawn from the nineteenth- and twentieth-century Britain, it is possible to begin to recover at least some of the feelings and responses that past travellers experienced. I argue that such an approach provides an important additional perspective to research in transport history.

Meta-analysis of Cryogenian through modern quartz microtextures reveals sediment transport histories

ABSTRACT Quantitative analysis of quartz microtextures by means of scanning electron microscopy (SEM) can reveal the transport histories of modern and ancient sediments. However, because workers identify and count microtextures differently, it is difficult to directly compare quantitative microtextural data analyzed by different workers. As a result, the defining microtextures of certain transport modes and their probabilities of occurrence are not well constrained. We used principal-component analysis (PCA) to directly compare modern and ancient aeolian, fluvial, and glacial samples from the literature with nine new samples from active aeolian and glacial environments. Our results demonstrate that PCA can group microtextural samples by transport mode and differentiate between aeolian transport and fluvial and glacial transport across studies. The PCA ordination indicates that aeolian samples are distinct from fluvial and glacial samples, which are in turn difficult to disambiguate from each other. Ancient and modern sediments are also shown to have quantitatively similar microtextural relationships. Therefore, PCA may be a useful tool to constrain the ambiguous transport histories of some ancient sediment grains. As a case study, we analyzed two samples with ambiguous transport histories from the Cryogenian Bråvika Member (Svalbard). Integrating PCA with field observations, we find evidence that the Bråvika Member facies investigated here includes aeolian deposition and may be analogous to syn-glacial Marinoan aeolian units including the Bakoye Formation in Mali and the Whyalla Sandstone in South Australia.

Detrital cosmogenic 21Ne records decoupling of source-to-sink signals by sediment storage and recycling in Miocene to present rivers of the Great Plains, Nebraska, USA

The preservation of conglomerates far from mountainous sources is commonly interpreted in terms of tectonic or climatic forcing. To relate a depositional signal to changing conditions in source areas, the process and duration of sediment routing from source to sink need to be determined. For the first time, we quantified sediment transport histories using cosmogenic 21Ne in quartzite pebbles from modern river gravels and Neogene conglomerates from the modern and ancient North Platte River of the Great Plains of Nebraska, United States. We demonstrate that at ∼400 km distance from the Front Ranges of the Rocky Mountains, the majority of pebbles were stored in older channel deposits for up to several millions of years before being recycled; this was enabled by very slow to zero basin subsidence rates. This implies that upstream tectonic or climatic controls on surface processes were decoupled from the downstream depositional record—a result supported by the similarities in cosmogenic 21Ne values among Miocene, Pliocene, and modern river channel pebbles despite known changes in tectonic and climatic forcing.

The zircon evidence of temporally changing sediment transport—the NW Gondwana margin during Cambrian to Devonian time (Aoucert and Smara areas, Moroccan Sahara)

Detrital zircon provenance studies are an established tool to develop palaeogeographic models, mostly based on zircon of siliciclastic rocks and isotope data. But zircon is more than just istopes and features well definable morphological characteristics. The latter may indicate single grain transport histories independent of the individual grade of concordance. This additional tool for palaeogeoraphic reconstructions was tested on zircon from siliciclastic and carbonate sedimentary rocks of Palaeozoic age from the Aoucert and Smara areas of the Souttoufides, while findings of zircon in limestone generally open new archives for sedimentary provenance analysis. The morphologies—length, width, roundness, grain surfaces—of 834 detrital zircons from sediments of allochthonous Cambrian, and (par-)autochthonous Ordovician, and Devonian units were studied, while 772 of them were analysed for their U–Th–Pb isotopes by LA-ICP-MS. Mesoproterozoic zircon contents of more than 10% in the Cambrian sediments exclude the West African Craton (WAC) as exclusive source area. Thus, at least one additional external source is suggested. This is likely the western Adrar Souttouf Massif with its significant Mesoproterozoic zircon inheritance, or comparable, yet unknown sources. Decreasing Mesoproterozoic zircon age populations in Ordovician sediments are thought to be linked to the rifting of the terranes in the course of the Rheic Ocean opening and a predominant supply of WAC detritus. The Devonian sediments likely contain reworked material from the Cambrian siliciclastics, which is shown by the zircon age distribution pattern and the zircon morphologies. Therefore, multiple shifts in the direction of sedimentary transport are indicated.

Distinguishing Depositional Setting For Sandy Deposits In Coastal Landscapes Using Grain Shape

Abstract: Several methods exist that use sediment properties to characterize depositional setting and related mechanisms of transport, including analysis of grain-size distributions, sediment petrology, micromorphology, and grain structure. Techniques that rely on electron or optical microscopy produce results with varying degrees of success and applicability. Here, a new method is presented and used to differentiate between littoral and eolian sands that were extracted from recently formed landforms, as well as landforms that are from mid to late Holocene in age. The method utilizes a standard optical microscope with a mounted digital camera, paired with freely available software (ImageJ) to characterize grain shape parameters. The method was tested on nearly 6000 sand grains from samples with varied transport histories, and it was found that grain solidity was the most distinguishable characteristic between eolian and littoral samples, differentiating them 86% of the time for calibration samples. The method was used to correctly identify the mechanism of transport for 76% of the samples. Patterns in the results indicated that this method could be extended to link potential sediment sources to various depositional basins, and future work includes testing the method in areas with a different mineralogy and/or landscape history.

Proportion of Glacially To Fluvially Induced Quartz Grain Microtextures Along the Chitina River, SE Alaska, U.S.A.

Abstract Certain micrometer-scale fractures, or microtextures, on grain surfaces are the result of specific transport processes. Accordingly, these transport-induced microtextures are used to infer depositional setting in ancient deposits. Multiple transport histories complicate the microtextural record because modification of grain surfaces can reduce or eliminate the signal of earlier transport episodes. This study utilizes scanning electron microscopy to analyze surface microtextures to assess the role of fluvial overprint on glacially derived grains along ∼ 188 km of the proglacial Chitina River, SE Alaska. Results indicate that occurrence frequency of glacially induced microtextures (i.e., straight and curved grooves, deep troughs, and crescentic gouges) negatively correlates to distance downstream, yet these microtextures persist in every sample. Conversely, occurrence frequency of fluvially induced microtextures (i.e., v-shaped cracks and edge rounding) positively correlate to distance downstream. At least in the Chitina River watershed, the ratio of fluvially to glacially induced microtextures (F/G ratio) generally records physiographic variation, including increase in fluvial signal after a major tributary confluence, and decrease downstream from the intersection of valley glaciers. These results suggest that analysis of quartz grain microtextures in ancient fluvial deposits can be used to infer glacial influence when other diagnostic sedimentologic indicators of glaciation are lacking. Other potential uses for the proxy may exist, but need to be assessed after other modern proglacial systems are studied, including: 1) estimates of distance to paleo–ice margins using the respective downstream trends of glacially or fluvially induced microtextures, and 2) paleogeography of ancient glacio-fluvial systems through F/G ratio analysis.

Palynomorphs of the Fezouata Shale (Lower Ordovician, Morocco): Age and environmental constraints of the Fezouata Biota

The present study documents new palynological investigations of the Fezouata Shale from the Anti-Atlas (Morocco). Palynomorphs were extracted from samples collected from both outcrops and drill cuttings. Outcrop samples were taken near Zagora, and include some that were collected during excavation of stratigraphic horizons where exceptionally well-preserved fossils of the Fezouata Lagerstätte occur. Subsurface samples were taken from the AZ-1 (Adrar Zouggar Mountain) borehole, which was extracted some 300km to the southwest of Zagora. The palynological samples yielded acritarchs, chitinozoans, scolecodonts, conodonts and fragments of graptolites. The abundance and quality of preservation of palynomorphs varies greatly, but rich and diverse assemblages were recovered from several samples. The diversity and composition of the assemblages points to an open shelf environment. Generally mixed preservation states suggest resedimentation or differential transport histories. The acritarchs can be assigned to the diagnostic messaoudensis-trifidum acritarch assemblage, which is typical of the Tremadocian/Floian boundary interval of the Gondwanan margin in high southern palaeolatitudes. The acritarch taxa present in some of the lower parts of the Fezouata Shale including levels of exceptional preservation can be attributed to sub-assemblages 1–2 of the messaoudensis-trifidum assemblage and thus point to a late Tremadocian age of the Fezouata Lagerstätte, confirming biostratigraphic data provided by graptolites of the Araneograptus murrayi graptolite biozone. Chitinozoans from the Fezouata Shale are from the E. symmetrica and E. brevis biozones and include various species that are well-known from several localities on the Gondwanan margin and from other palaeocontinents (Baltica, Laurentia, and South China), demarcating broad links between those regions. The coincidence between index fossils of these three groups, hitherto not all found in the same level, suggests that the age assignments of chitinozoan biozones may be in need of revision.

“Beachten Sie die Lücken”: Reviewing the Cultural Histories and Geographies of Public Transport in Berlin

In Berlin’s U-Bahn an announcement cautions passengers: “Bitte beachten Sie beim Aussteigen die Lücke zwischen Zug und Bahnsteigkante.” This fastidious rendition of the London Underground’s “mind the gap” warning reveals audio equivalencies between the two transport networks. However, the more numerous curved platforms of the Underground—originally designed for the shorter trains of the past—mean that its gaps are more pronounced than those of the U-Bahn. When it comes to the cultural investigation of each city’s broader public transport histories and geographies, the reverse is true. Unlike in London, public transport in the German capital has escaped the significant scholarly attention of historians in recent years.

Polymer Reaction Engineering in China

Polymer Reaction Engineering in China

Fuels and Flows

Despite obvious links, the relationship between transport and energy remains generally understudied among historians of transport. By briefly examining the ways in which energy resources and energy flows have intersected with transport patterns, transport costs, and transport technology, this thought piece makes a case for bringing considerations of energy into our writing of transport histories. It goes on to argue that a focus on energy and its movement also offers new insights and objects of study to those with broader interests in questions of mobility, for in tracing energy's pathways, we can better see how social, political, and environmental phenomena of varying scales have been constituted and connected in motion.

Assessing the Origin and Variability of Eolian Lithic Material For High-Resolution Paleoceanographic Reconstructions Off Northern Chile (23 S)

Abstract Lithic particles in marine laminated sediments provide the opportunity to reconstruct ocean-climate processes like wind dynamics from the sedimentary record. In Mejillones Bay (23° S), located on the hyperarid coast of the Atacama Desert, marine laminated sediments record paleoceanographic variations related to coastal upwelling and regional South Pacific climate conditions. In this work we assess the provenance of lithic particles found in these laminated sediments and we analyze the relationship between the variability of lithic transport-sedimentation processes and wind. We compared the sedimentological, morphological, and mineralogical characteristics of desert soil particles with those of surface sediments collected at various locations of the bottom of the bay and particles retrieved from marine sediment cores. We also compared horizontal fluxes of particles eroded at the surface of the hyperarid plain (Pampa Mejillones) and vertical fluxes of lithic material settling through the water column in the marine basin. Results show that particles retrieved in dust traps, mostly quartz and feldspars with some calcite fragments, amphiboles, and clay minerals, are similar to those collected in the marine sediment traps. These are characterized by grain-size modes finer than 125–150 µm and decreasing from the pampa towards the bottom of the bay. Together with morphological features such as polished surfaces and “V-shaped” impact marks, this supports the hypothesis of an eolian origin of these particles with complex transport histories from Quaternary uplifted coastal plains towards the marine laminated sediments. From in situ measurements and monitoring we observed a close relationship between the variability of wind intensity, horizontal fluxes of lithic particles across the surface of the desert, and vertical fluxes in the marine water column. This supports the idea that not only in Mejillones Bay but also in other places, quantitative paleoclimate reconstructions could be performed from the quantification of the amount of lithic particles with sizes between 50 and 150 µm contained in laminated sediments.

Settling Velocity and Grain Shape of Maerl Biogenic Gravel

Abstract The importance of a grain-size-dependent shape metric, convexity, for determining the unusual settling velocity characteristics of maerl, a variety of unattached coralline algae, has been quantified by modeling of settling-tube data. A modification of the general settling-velocity equation of Ferguson and Church (2004), involving a dependence of the drag coefficient-related constant, C2, on grain size, produces a satisfactory fit to the experimental observations. For a given grain size and at Reynolds numbers greater than ∼ 220, maerl grains experience greater drag than is predicted for natural quartz grains by Ferguson and Church (2004) because of this grain-size-dependent roughness. Subsequent detailed measurements of maerl grain shape using microscopic image analysis confirm a strong positive linear relationship between grain roughness, quantified by the reciprocal of convexity, and grain size. This departure from the ideal settling characteristics of siliciclastic gravel is hypothesized to explain the observed propensity of maerl, under suitable hydrodynamic conditions, to form beach deposits with a low percentage of sand. Maerl samples from three different sedimentary environments (open marine, intertidal, and beach) exhibit different linear relationships between roughness and grain size, probably resulting from different degrees of abrasion due to a combination of different wave climates and transport histories. This spatial variability in grain texture suggests that a general equation for maerl settling velocity is not possible. However, for maerl, and other branched sediment types, it may only be necessary to measure the convexity of the middle and largest size fractions to estimate the linear variation of C2 with grain size, resulting in an accurate estimate of the settling-velocity curve. In the broader context of physical sedimentology, our results indicate that, over a range of bottom current conditions between 200 and 250 mm s−1, where the settling curve of maerl is flat and grain-size invariant relative to siliciclastic sediment, a larger part of the maerl grain-size distribution can remain in suspension compared to the siliciclastic sediment. This contrast in physical properties may be an effective process for the spatial separation of coarse siliciclastic and biogenic sediment.

Mobility and Modernity in the Urban Transport Systems of Colonial Manila and Singapore

Transport motorization is a critical juncture in the history of mobility, yet there is a pressing need to scrutinize and historicize it further, especially in the historiography of Southeast Asia. In this comparative study of the transport histories of early-twentieth-century Manila and Singapore, two colonial urban centers that exhibited the classical metropole-colony dynamics, I argue that the motorization of urban transportation was not simply a process of technological change. The introduction of the electric streetcar and the motor vehicle in the early twentieth century (1900–1941) led not just to the marginalization of other transport modes but also to profound changes in the formation of modern societies and the very idea of modernity. Such changes were accentuated by colonial conditions and the ideological particularities of the late-colonial era, such as the racialist discourse that informed the notion of technological modernism. Adding complexity to society–technology relations was the reality of appropriation, as the colonized began to participate either as conscious consumers or as laborers in providing transport services.

Intercontinental dispersal of bacteria and archaea by transpacific winds.

Microorganisms are abundant in the upper atmosphere, particularly downwind of arid regions, where winds can mobilize large amounts of topsoil and dust. However, the challenge of collecting samples from the upper atmosphere and reliance upon culture-based characterization methods have prevented a comprehensive understanding of globally dispersed airborne microbes. In spring 2011 at the Mt. Bachelor Observatory in North America (2.8 km above sea level), we captured enough microbial biomass in two transpacific air plumes to permit a microarray analysis using 16S rRNA genes. Thousands of distinct bacterial taxa spanning a wide range of phyla and surface environments were detected before, during, and after each Asian long-range transport event. Interestingly, the transpacific plumes delivered higher concentrations of taxa already in the background air (particularly Proteobacteria, Actinobacteria, and Firmicutes). While some bacterial families and a few marine archaea appeared for the first and only time during the plumes, the microbial community compositions were similar, despite the unique transport histories of the air masses. It seems plausible, when coupled with atmospheric modeling and chemical analysis, that microbial biogeography can be used to pinpoint the source of intercontinental dust plumes. Given the degree of richness measured in our study, the overall contribution of Asian aerosols to microbial species in North American air warrants additional investigation.

14C and 13C characteristics of higher plant biomarkers in Washington margin surface sediments

Plant wax lipids and lignin phenols are the two most common classes of molecular markers that are used to trace vascular plant-derived OM in the marine environment. However, their 13C and 14C compositions have not been directly compared, which can be used to constrain the flux and attenuation of terrestrial carbon in marine environment. In this study, we describe a revised method of isolating individual lignin phenols from complex sedimentary matrices for 14C analysis using high pressure liquid chromatography (HPLC) and compare this approach to a method utilizing preparative capillary gas chromatography (PCGC). We then examine in detail the 13C and 14C compositions of plant wax lipids and lignin phenols in sediments from the inner and mid shelf of the Washington margin that are influenced by discharge of the Columbia River. Plant wax lipids (including n-alkanes, n-alkanoic (fatty) acids, n-alkanols, and n-aldehydes) displayed significant variability in both δ13C (−28.3‰ to −37.5‰) and Δ14C values (−204‰ to +2‰), suggesting varied inputs and/or continental storage and transport histories. In contrast, lignin phenols exhibited similar δ13C values (between −30‰ and −34‰) and a relatively narrow range of Δ14C values (−45‰ to −150‰; HPLC-based measurement) that were similar to, or younger than, bulk OM (−195‰ to −137‰). Moreover, lignin phenol 14C age correlated with the degradation characteristics of this terrestrial biopolymer in that vanillyl phenols were on average ∼500years older than syringyl and cinnamyl phenols that degrade faster in soils and sediments. The isotopic characteristics, abundance, and distribution of lignin phenols in sediments suggest that they serve as promising tracers of recently biosynthesized terrestrial OM during supply to, and dispersal within the marine environment. Lignin phenol 14C measurements may also provide useful constraints on the vascular plant end member in isotopic mixing models for carbon source apportionment, and for interpretation of sedimentary records of past vegetation dynamics.

A revised approach to discriminating sediment transport histories in glacigenic sediments in a temperate alpine environment: a case study from Fox Glacier, New Zealand

ABSTRACTClast shape measurements have developed into a standard method for reconstructing the transport histories of sediments in glacial environments. The majority of studies use the ‘RA‐C40’ covariance approach, with some researchers routinely including clasts of varying lithologies within their samples. The corollary is that variable lithological properties may control clast form and roundness, rather than debris‐transport mechanisms. Despite this, the role of lithology on clast shape in glacial environments has rarely been analysed. Furthermore, some studies have reported difficulties in using the RA‐C40 co‐variance plot in discriminating clasts that have undergone subglacial transport, and clasts that have been modified by fluvial activity. Results from a glacierized valley in a temperate alpine setting indicate that detailed analysis of clast shape where samples are of uniform lithology, although time consuming, is a useful tool in the investigation of deposits in glaciated environments. Copyright © 2012 John Wiley & Sons, Ltd.