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Analysis of sedimentary materials using a portable luminescence reader (or portable optically stimulated luminescence reader POSL), is a useful, rapid (a few minutes per sample), cost-effective and safe (not requiring exposure to chemicals) way to establish relative sample age. Moving beyond information that guides initial field interpretations, or develops targeted sampling strategies for full laboratory-based dating protocols, toward rapid age assessment has been more challenging. This study is the first demonstration of a simple, elegant and practical calibration of POSL signals into sample age estimates. This involved measuring the POSL signals from 144 samples with established published ages from across southern Africa, and a regression analysis. The data show that a regional-specific approach to calibration is needed, with regional patterns in POSL signals that are supported by 148 further undated samples. Four broad regions are defined: the Namib Sand Sea (NSS), the northern Kalahari (barchan dunes on the floor of Makgadigadi) (Nnk-MBa), the western Kalahari (WK) and the southern Kalahari (SK). Sample composition data, such as quartz-to-feldspar ratios (Q/F) appears to account for the largest contrasts within the dataset, whilst inherent POSL signal brightness and grain coloured-coatings (iron and clay) may also influence signals. The strength of the regressions (R 2 of 0.99, 0.93, 0.81 and one moderate at 0.52 for the NSS, SK, WK and NnK-MBa respectively) between POSL signals and sample age, (for ages back to 118, 104 74 and 5 ka for the NSS, SK, WK and NnK-MBa respectively), demonstrates the practicality and huge value of this simple approach. The implication is that region-specific calibrations must be built prior to using the POSL reader for rapid age assessments. This approach is a cost and time-effective method for inter-dunefield landscape-scale analyses, which will cast light on the key climatic variables driving landscape change in sand-rich drylands during the Late Quaternary, and also has the potential for large-scale analysis within other geomorphic settings.

[The Andean cordillera, the Himalayan collisionorogen, and the Apennine thrust belt are archetypes of different orogens associatedwith different sedimentary basins. Sediment storage capacity, maximum inforedeeps where slab retreat induces rapid subsidence of the downgoing plate, isminimum in broken retroarc basins where flat‐slab subduction leads to basininversion and uplift of basement blocks on the overriding plate. , Abstract Central Argentina from the Pampean flat‐slab segment to northern Patagonia (27°–41°S) represents a classic example of a broken retroarc basin with strong tectonic and climatic control on fluvial sediment transport. Combined with previous research focused on coastal sediments, this actualistic provenance study uses framework petrography and heavy‐mineral data to trace multistep dispersal of volcaniclastic detritus first eastwards across central Argentina for up to ca. 1,500 km and next northwards for another 760 km along the Atlantic coast. Although detritus generated in the Andes is largely derived from mesosilicic volcanic rocks of the cordillera, its compositional signatures reflect different tectono‐stratigraphic levels of the orogen uplifted along strike in response to varying subduction geometry as well as different character and crystallization condition of arc magmas through time and space. River sand, thus, changes from feldspatho‐litho‐quartzose or litho‐feldspatho‐quartzose in the north, where sedimentary detritus is more common, to mostly quartzo‐feldspatho‐lithic in the centre and to feldspatho‐lithic in the south, where volcanic detritus is dominant. The transparent‐heavy‐mineral suite changes markedly from amphibole ≫ clinopyroxene > orthopyroxene in the north, to amphibole ≈ clinopyroxene ≈ orthopyroxene in the centre and to orthopyroxene ≥ clinopyroxene ≫ amphibole in the south. In the presently dry climate, fluvial discharge is drastically reduced to the point that even the Desaguadero trunk river has become endorheic and orogenic detritus is dumped in the retroarc basin, reworked by winds and temporarily accumulated in dune fields. During the Quaternary, instead, much larger amounts of water were released by melting of the Cordilleran ice sheet or during pluvial events. The sediment‐laden waters of the Desaguadero and Colorado rivers then rushed from the tract of the Andes with greatest topographic and structural elevation, fostering alluvial fans inland and flowing in much larger valleys than today towards the Atlantic Ocean. Sand and gravel supply to the coast was high enough not only to promote rapid progradation of large deltaic lobes but also to feed a cell of littoral sediment transport extending as far north as the Rio de la Plata estuary.]

The Congo deep-sea fan, the largest on Earth fed entirely with anorogenic detritus, is characterized by quartzose to pure quartzose sand, reflecting multiple recycling coupled with extreme chemical weathering in cratonic equatorial Africa. The very youthful lower course of the Congo River connects directly to a steep canyon, where detritus including quartz grains up to a few millimeters in diameter is funneled towards Atlantic Ocean floors and deposited at abyssal depths more than a thousand kilometers away from shore. This article illustrates for the first time in detail the mineralogical and geochemical signatures of Congo Fan sands and discusses the factors controlling their intersample and intrasample variability as a key to understand how sediment is generated, recycled, and finally transferred to the deep sea. Compositional variability is largely grain-size-dependent. Combined petrographic and Raman spectroscopy analyses demonstrate that quartz increases in coarser samples and size classes, whereas feldspars are concentrated in finer sizes, plagioclase relative to K-feldspar and orthoclase relative to microcline, defining an order of mechanical and chemical durability among detrital tectosilicates. Because of overwhelming quartz abundance and very low heavy-mineral concentration, quartz contributes significantly to the REE budget and up to 40–50% of Nd in coarser samples, characterized by εNd values as low as –21. The strong grain-size-dependent variability of εNd suggests that quartz carries a markedly more negative εNd signature than monazite and other detrital components. This is chiefly ascribed to the durability of quartz grains, able to survive repeated cycles of weathering and diagenesis through Proterozoic and Phanerozoic time better than all other minerals. Neodymium model ages are influenced less by grain size and quartz abundance but more by the Sm/Nd ratio of different detrital components, and samples hydrodynamically enriched in LREE-rich minerals display TNd,CHUR and TNd,DM ages 1.2–1.4 Ga younger than samples enriched in HREE minerals. Not all detritus in the Congo Fan is supplied transversally by the Congo River. Forward-mixing calculations based on mineralogical data indicate that sand entrained northward by longshore currents mixes progressively with Congo River sand along the northernmost Angola coast, penetrates in the Soyo estuary, and is eventually captured in the canyon and transferred to the deep-sea fan, where it is estimated to represents 7 ± 2% of turbidite deposits.

Understanding the evolution of river systems in southern Africa is fundamental to constrain the evolution of landscape and sediment dispersal patterns. It is widely considered that the upper Zambezi River was connected with the Limpopo River during the Cretaceous, forming what was then the largest river in Africa. Crustal flexure during the Paleogene severed the upper Zambezi drainage from the Limpopo, setting the framework of the modern Zambezi and Limpopo River systems. We present first evidence—based on heavy-mineral assemblages from cores drilled offshore of the Limpopo River mouth and samples collected in different reaches of the modern Limpopo River, integrated with magnetic susceptibility, detrital-zircon geochronology, and geomorphological analysis—suggesting that the current Limpopo River formed recently in the Plio-Quaternary. Plio-Quaternary climate change is envisaged to have controlled the recent dynamics of river drainage and consequent distribution of sediment loads, as observed in many other transcontinental rivers worldwide.

Large sediment masses are transferred over many hundreds of kilometres along the coast of passive continental margins worldwide. The relevance of such a phenomenon for source-to-sink studies, environmental issues, and coastal management remains largely unperceived. This study traces the paths of volcaniclastic sand along ca 2170km of the Argentine coast and documents a 760km long cell of littoral transport extending from the formerly larger Río Colorado delta to the edge of the Río de la Plata mouth. During deglaciation stages and humid periods of the Pleistocene, a much greater sediment volume than today was transferred by the Desaguadero and Colorado rivers from the highest-relief tract of the Andean Cordillera to the Atlantic Ocean. Amphibole-rich sand originally supplied by the Río Desaguadero is being recycled today from Pampean lowlands to feed the beaches along Río de la Plata southern shores, whereas pure quartzose sand of Río Paraná is found only adjacent to its prograding delta. Augite-rich sand supplied by the Río Colorado is dominant along the coast of the Buenos Aires Province, where it mixes locally with coarser-grained quartz-rich detritus recycled in the urbanized Mar del Plata area. Hypersthene-rich sand of the Río Negro is dispersed both north and south of the mouth, where heavy-mineral-rich lag deposits are formed in areas of accelerated erosion and retreating sea cliffs. Changes of mineralogical signatures during long-distance littoral transport are largely ascribed to local supply from coastal erosion or hydrodynamic effects rather than to selective breakdown of labile grains. Whereas the relative abundance of amphibole and pyroxene is largely independent of transport distance, olivine is depleted both in the northern part of the Colorado littoral cell and south of the Río Negro mouth, which is chiefly ascribed to dilution by recycling of Neogene sediments that have undergone early intrastratal dissolution rather than to mechanical loss.

This Nile Delta case study provides quantitative information on a process that we must understand and consider in full before attempting provenance interpretation of ancient clastic wedges. Petrographic and heavy-mineral data on partly lithified sand, silt, and mud samples cored from the up to 8.5 km-thick post-Eocene succession of the offshore Nile Delta document systematic unidirectional trends. With increasing age and burial depth, quartz increases at the expense of feldspars and especially of mafic volcanic rock fragments. Heavy-mineral concentration decreases drastically, transparent heavy minerals represent progressively lower percentages of the heavy fraction, and zircon, tourmaline, rutile, apatite, monazite, and Cr-spinel relatively increase at the expense mainly of amphibole in Pliocene sediments and of epidote in Miocene sediments. Recent studies have shown that the entire succession of the Nile Delta was deposited by a long drainage system connected with the Ethiopian volcanic highlands similar to the modern Nile since the lower Oligocene. The original mineralogy should thus have resembled that of modern Delta sand much more closely than the present quartzose residue containing only chemically durable heavy minerals. Stratigraphic compositional trends, although controlled by a complex interplay of different factors, document a selective exponential decay of non-durable species through the cored succession that explains up to 95% of the observed mineralogical variability. Our calculations suggest that heavy minerals may not represent >20% of the original assemblage in sediments buried less than ~1.5 km, >5% in sediments buried between 1.5 and 2.5 km, and >1% for sediments buried >4.5 km. No remarkable difference is detected in the intensity of mineral dissolution in mud, silt, and sand samples, which argues against the widely held idea that unstable minerals are prone to be preserved better in finer-grained and therefore presumably less permeable layers. Intrastratal dissolution, acting through long periods of time at the progressively higher temperatures reached during burial, can modify very drastically the relative abundance of detrital components in sedimentary rocks. Failure to recognize such a fundamental diagenetic bias leads to grossly mistaken paleogeographic reconstructions, as documented paradigmatically by previous provenance studies of ancient Nile sediments.

The Nicobar Fan and Bengal fans can be considered as the eastern and western parts, respectively, of the largest submarine-fan system in the world. This study presents the integrated results of petrographic and provenance studies from the Nicobar Fan and evaluates these in the context of controls on sedimentation. Both fans were predominantly supplied by Himalaya-derived material from the main tectono-stratigraphic sequences as well as the Gangdese arc. A lack of volcanic material in the Nicobar Fan rules out sources from the Sumatra magmatic arc. Overall, the petrographic data shows a progressive decrease in sedimentary detritus and corresponding increase of higher-grade metamorphic detritus up-section. Changes in sediment provenance and exhumation rates in the Himalaya are seen to track changes in sediment accumulation rates. High sediment accumulation rates in the Bengal Fan occurred at ∼13.5–8.3 Ma, and in the Nicobar Fan from ∼9.5–5 Ma. Both fans show peak accumulation rates at 9.5–8.3 Ma (but with the Nicobar Fan being about twice as high), and both record a sharp drop from ∼5.5–5.2 Ma, that coincided with a change in river drainage associated with the Brahmaputra River diverting west of the uplifting Shillong Plateau. At ∼5 Ma, the Nicobar Fan was supplied by an eastern drainage route that finally closed at ∼2 Ma, when sediment accumulation rates in the Nicobar Fan significantly decreased. Sediment provenance record these changes in routing whereby Bengal Fan deposits include granitoid sources from the Namche Barwa massif in the eastern syntaxis that are not seen in the Nicobar Fan, likely due to a more localised eastern drainage that included material from the Indo-Burman wedge. Prior to ∼3 Ma, source exhumation rates were rapid and constant and the short lag-time rules out significant intermediate storage and mixing. In terms of climate versus tectonic controls, tectonically driven changes in the river network have had most influence on fan sedimentation.

The highest peaks in Europe are found in the central Greater Caucasus, an orogenic belt characterized by extremely active tectonic and sedimentary processes. In this rugged mountain region, we have investigated sand generation and erosion patterns by using high-resolution petrographic and heavy-mineral data on river sands complemented by detailed morphometric analysis of 9 major mountain branches of the Terek River. Also presented is an extensive review of sediment-transport data available in the Russian literature on glacial-lake outburst floods and rainfall-triggered debris flows, which owing to global warming and glacier retreat have afflicted the Greater Caucasus with increasing frequency in the last 50 years. The accurate definition of mineralogical signatures characterizing detritus derived from six end-member volcanic, metamorphic basement, and sedimentary/metasedimentary rock units allowed us to calculate the relative contribution of each to the sand load, with particular precision for the Baksan River draining Mt. Elbrus. Results clearly indicate that volcanic and basement rocks supply a disproportionate amount of sand relatively to their outcrop area, testifying to strongly focused erosion in the high-relief axial part of the range. River channels here display extreme steepness (ksn up to 200–300) and low concavity indices (θ 0.15 - 0.35) typical of thalwegs shaped by debris flows. Average erosion rates reach as high as 2–4 mm/a, which is explained by the frequency of catastrophic mass-transport events able to mobilize in one single episode between 106 and 107 tons of detritus, corresponding to 10–50 mm of erosion distributed across the catchment upstream. On 20 September 2002, the Kolka “glacier disaster” mobilized 2 × 108 tons of debris, corresponding to ≥ 400 mm of erosion in the upper Genaldon valley. To quantify the intrinsic capacity of different bedrock types to generate sand isolated from such a strong focused-erosion effect, we used the normalized steepness index ksn as a proxy of erosion rate and thus redefined the sand generation index as S G I * = S A S A A A k s n k s n A . More realistic values are thus obtained, although far more comprehensive data on sediment load than those presently available are required to discriminate robustly between the effect of focused-erosion versus lithological control on sand generation.

The Bangladesh lowlands are traversed by the largest sediment flux on the planet. Detritus generated mostly in Himalayan highlands and conveyed through the Ganga&ndash, Brahmaputra rivers and Meghna estuary reaches the Bay of Bengal, where it forms a composite deltaic system. This study integrates the vast existing database on Ganga&ndash, Brahmaputra sediments of all grain sizes from clay to sand with new petrographic, mineralogical, and geochemical data on estuarine and shallow-marine sands. A large spectrum of compositional signatures was used to: (i) assess the relative supply of the Ganga and Brahmaputra rivers to estuarine and shelfal sediments, (ii) define the compositional variability of estuarine sediments and the impact exerted by hydraulic sorting and climate-related chemical weathering on provenance signals, (iii) define the compositional variability of shelf sediments and the potential hydrodynamic segregation of fast-settling heavy minerals in coastal environments and of slow-settling platy micas on low-energy outer-shelf floors, (iv) consider the potential additional mud supply from the western subaerial part of the delta formerly built by the Ganga River, and (v) draw a preliminary mineralogical comparison between fluvio-deltaic sediments and turbidites of the Bengal&ndash, Nicobar deep-sea fan, thus tracing sediment dispersal across the huge sedimentary system extending from Tibet to the equatorial Indian Ocean. All investigated mineralogical and geochemical parameters, as well as Sr and Nd isotope ratios and clay&ndash, mineral assemblages, showed a clear prevalence in sediment supply from the Brahmaputra (60&ndash, 70%) over the Ganga (30&ndash, 40%). Heavy-mineral suites and Sr and Nd isotope fingerprints of Bengal shelf sediments are nearly identical to those of the Brahmaputra River and Meghna estuary, also because the Brahmaputra carries almost twice as many Ca-plagioclase grains and heavy minerals including epidote than the Ganga, and these minerals control the large majority of the Sr and Nd budgets. The experience gained in modern settings can be directly extrapolated only to the recent past, because sediments older than the late Pleistocene and buried more than a few hundred meters begin to lose less durable ferromagnesian minerals by selective chemical dissolution, which makes quantitative estimates progressively less robust in more deeply buried older strata.

This study illustrates the petrographic, heavy-mineral, geochemical and geochronological signatures of sand transported by various branches of the Irrawaddy (Ayeyarwadi) River, one of the first in the world for sediment flux. Intrasample and intersample compositional variability, weathering and hydraulic-sorting controls are also discussed. Feldspatho-quartzose sand in Irrawaddy headwaters is largely derived first-cycle from mid-crustal metamorphic and plutonic rocks of the Mogok Belt and Lohit complex, whereas feldspatho-litho-quartzose Chindwin sand is largely recycled from supracrustal, sedimentary and very low-grade metasedimentary units. Additional mafic to ultramafic detritus is derived from ophiolites and blueschists exposed from the Indo-Burman Ranges to the Jade Mines and Myitkyina belts, linked northward to the Yarlung-Tsangpo suture of the Himalaya. Volcanic detritus derived from the Popa-Wuntho arc or recycled from forearc-basin strata also occurs. Decreasing concentration of most chemical elements along the Irrawaddy reflects progressive addition of detritus recycled from sedimentary rocks, most evident downstream of the Chindwin confluence. REE patterns with LREE enrichment and negative Eu anomaly reflect the occurrence of allanite, largely derived from granitoid rocks in the Mali catchment. Chemical indices indicate moderate weathering in the monsoon-dominated climate of Myanmar. Young U-Pb ages (15–170 Ma) represent 85% of detrital zircons in Irrawaddy headwater branches, reflecting long-lasting subduction-related magmatism along a ring of fire connecting with the southern and central Lhasa batholiths in Tibet and polyphase metamorphism in the Mogok belt. Chindwin sand contains larger amounts of finer-grained, recycled pre-Mesozoic zircons, also yielding early Mesoproterozoic to Archean ages. Such different petrographic, heavy-mineral, geochemical and geochronological fingerprints characterizing sand in different river branches allowed us to calculate bulk-sediment and zircon-provenance budgets that converge to indicate equivalent sand supply from the Nmai and Mali Rivers to the upper Irrawaddy, and from the Chindwin and upper Irrawaddy to the lower Irrawaddy. This implies that despite of higher erosion potential indicated by stream-profile analysis in high-relief Irrawaddy headwaters, sediment yields and erosion rates are detectably higher in the Chindwin catchment, which is mainly ascribed to higher erodibility of widely exposed siliciclastic rocks. Quantifying sediment provenance and defining erosion patterns based on an integrated compositional database in a big-river system such as the mighty Irrawaddy allows us to expand our understanding of sediment-generation processes with the ultimate goal to increase our capacity to read into the stratigraphic record.

The Changjiang, the fourth longest river on Earth and the largest in Eurasia, has a complex sediment-routing system presently interrupted by the Three Gorges Dam, the world's largest hydroelectric engineering project. To study sediment-generation processes in the huge catchment and compare the different erosion patterns obtained by different methodological approaches, high-resolution petrographic and heavy-mineral analyses were performed on sands from the trunk river and its major tributaries. The frequency distributions of diverse groups of detrital amphiboles were also investigated. Rigorous statistical methods were used to define end-members, evaluate mineralogical variability, assess similarities among samples, and eventually calculate the relative contributions from each major tributary to the trunk river by forward end-member modelling of integrated compositional data. The litho-quartzose sand with few heavy minerals generated in Tibetan headwaters evolves downstream to feldspatho-litho-quartzose with medium-rank metamorphic rock fragments and moderately rich amphibole-epidote suites. Sand across the Sichuan basin and as far as the Three Gorges Dam is enriched in mafic volcanic, clinopyroxene, and carbonate grains eroded from Permian basalts and Paleozoic strata of the South China Block. The final (Yangtze) tract is characterized by litho-feldspatho-quartzose sand with moderately poor, amphibole-dominated suites with epidote, clinopyroxene, and garnet. The orogenic compositional signature acquired in the upper part of the basin is thus carried all the way to the Chinese passive margin, as observed also for the Yellow River in the north. Even after long-distance transport across wide continental areas, detrital modes thus reveal the tectonic character of the source rather than the geodynamic environment of the sink. Quantitative provenance analysis indicates that left-bank tributaries draining the Longmen and Qinlin mountains supply most of the sand reaching the East China Sea. Contributions from Tibetan headwaters are negligible, as those from right-bank tributaries in the middle-lower part of the basin. Sediment budgets and erosion patterns inferred from our integrated petrographic and heavy-mineral data set contrast with those based on detrital-zircon geochronology but agree with stream-profile analysis, revealing close correspondence with slope steepness, precipitation, stream power, tectonic activity, and frequency of major earthquakes. Sediment budgets based on amphibole groups are poorly constrained. We conclude that provenance budgets based on single-mineral species are typically unrobust, particularly because they suffer from inaccurate estimates of mineral concentration in the end-member sources. Exploring in detail a millesimal part of the sediment (typically 1/5000 in the case of zircon) is a risky strategy that may return a distorted picture of reality.

A never solved problem in sedimentary petrology is the origin of sandstone consisting exclusively of quartz and most durable heavy minerals. The Congo River offers an excellent test case to investigate under which tectonic, geomorphological, climatic, and geochemical conditions pure quartzose sand is generated today. In both upper and lowermost parts of the catchment, tributaries contain significant amounts of feldspars, rock fragments, or moderately stable heavy minerals pointing at the central basin as the main location of the “quartz factory”. In Congo sand, quartz is enriched relatively to all other minerals including zircon, as indicated by Si/Zr ratios much higher than in the upper continental crust. Selective elimination of old zircons that accumulated radiation damage through time is suggested by low percentages of grains yielding Archean U Pb ages despite the basin being surrounded by Archean cratonic blocks. Intense weathering is documented by the lack of carbonate grains in sand and by dominant kaolinite and geochemical signatures in mud. In sand, composed almost entirely of SiO2, the weathering effect is masked by massive addition of quartz grains recycled during multiple events of basin inversion since the Proterozoic. Changes in mineralogical, geochemical, and geochronological signatures across Bas-Congo concur to suggest that approximately 10% of the sand supplied to the Atlantic Ocean is generated by rapid fluvial incision into the recently uplifted Atlantic Rise. The Congo River connects with a huge canyon ~30 km upstream of the mouth, and pure quartzose sand is thus funnelled directly toward the deep-sea to feed a huge turbidite fan. Offshore sediments on both sides of the canyon are not derived from the Congo River. They reflect mixed provenance, including illite-rich dust wind-blown from the arid Sahel and augite, hypersthene, and smectite ejected from volcanic centres probably situated along the Cameroon Line in the north. Because mixing of detritus from diverse sources and supply of polycyclic grains almost invariably occurs in the terminal lowland tract of a sediment-routing-system, no ancient sandstone can be safely considered as entirely first-cycle. Moreover, the abundance of pure quartzarenite in the rock record can hardly be explained by chemical weathering or physical recycling alone. The final cleansing of minerals other than quartz, zircon, tourmaline, and rutile requires one or more cycles of chemical dissolution during diagenesis, which operates at higher temperatures and over longer periods than weathering at the Earth's surface.

The Indo-Burman Ranges (IBR) are a mountain range comprised of Mesozoic-Cenozoic rocks which run the length of Western Myanmar, extending into India and Bangladesh; to the west lies the Indian Ocean, and to the east lies the Central Myanmar Basin (CMB) along which the Irrawaddy River flows. The IBR are considered to be an accretionary prism, developed at the juncture of the Indian and Sunda plates, and a number of hypotheses have been proposed for their evolution. However, in order for these hypotheses to be evaluated, the timing of IBR evolution needs to be determined. We undertook a two-pronged approach to determining the timing of uplift of the IBR. (1) We present the first low-temperature thermochronological age elevation profiles of the IBR using ZFT, AFT and ZHe techniques. Our data show: a major period of exhumation occurred around the time of the Oligo-Miocene boundary; we tentatively suggest, subject to further verification, an additional period of exhumation at or before the late Eocene. (2) We carried out a detailed multi-technique provenance study of the sedimentary rocks of the IBR and Arakan Coastal region to their west, and compared data to coeval rocks of the CMB. We determined that during Eocene times, rocks of the CMB and IBR were derived from similar local provenance, that of the Myanmar arc to the east. Therefore at this time there was an open connection from arc to ocean. By contrast, by Miocene times, provenance diverged. Rocks of the CMB were deposited by a through-flowing Irrawaddy River, with detritus derived from its upland source region of the Mogok Metamorphic Belt and Cretaceous-Paleogene granites to the north. Such a provenance is not recorded in coeval rocks of the IBR, indicating that the IBR had uplifted by this time, providing a barrier to transport of material to the west. To the previously published list of viable proposals to explain the exhumation of the range, we add a new suggestion: the period of exhumation around the time of the Oligo-Miocene boundary could have been governed by a change to wedge dynamics instigated by a major increase in the thickness of the incoming Bengal Fan sediment pile.

High-resolution sand petrography and heavy mineral analyses help to frame U-Pb age and Hf isotope data from zircon grains, integrated in turn with geochemical data from detrital apatite, rutile, garnet, and monazite, and with Raman spectroscopy data from detrital amphibole, pyroxene, and epidote-group minerals. This multitechnique approach, including stream-profile analysis, was used to characterize components of the sediment flux and define erosion patterns across the Lhasa block, a complex continental-arc terrane caught in the Himalayan collision. Litho-feldspatho-quartzose detrital modes and hornblende-dominated heavy mineral assemblages suggest that the majority (four fifths) of the sand bed load in the Lhasa River catchment is derived from erosion of granitoid batholiths. Gravel composition, however, is markedly different and dominated by volcanic pebbles in the trunk river, as in all of its four major tributaries, testifying to an order-of-magnitude difference in apparent erosion rates between granitoid batholiths and arc lavas. This marked contrast, partly explained by wide exposures of granitoid rocks in the rugged Nyainqêntanglha Range characterized by active incision, is notably amplified by the high sand-generation potential of granitoid rocks, which, in contrast to dense joint blocks of andesitic lavas, tend to disintegrate to sandy grus upon weathering. Sedimentary strata, making up a good half of exposed rocks, are also underrepresented in sand bed load, suggesting selective mechanical breakdown of nondurable shale/slate grains. This exposes a serious bias affecting estimates based on sand only, and it highlights the necessity for taking into account the entire size spectrum from mud to gravel in order to improve the accuracy of sediment budgets. Provenance analysis should involve multiple methods applied to multiple minerals, rather than be based solely on a single rare mineral, even if it is exceptionally laden with potential provenance information, such as zircon.

This study focuses on the causes, modalities and obstacles of sediment transfer in the longest cell of littoral sand drift documented on Earth so far. Sand derived from the Orange River is dragged by swell waves and persistent southerly winds to accumulate in four successive dunefields in coastal Namibia to Angola. All four dunefields are terminated by river valleys, where aeolian sand is flushed back to the ocean; and yet sediment transport continues at sea, tracing an 1800Âkm long submarine sand highway. Sand drift would extend northward to beyond the Congo if the shelf did not become progressively narrower in southern Angola, where drifting sand is funnelled towards oceanic depths via canyon heads connected to river mouths. Garnet–magnetite placers are widespread along this coastal stretch, indicating systematic loss of the low-density feldspatho-quartzose fraction to the deep ocean. More than half of Moçamedes Desert sand is derived from the Orange River, and the rest in similar proportions from the Cunene River and from the Swakop and other rivers draining the Damara Orogen in Namibia. The Orange fingerprint, characterized by basaltic rock fragments, clinopyroxene grains and bimodal zircon-age spectra with peaks at ca 0·5ÂGa and ca 1·0ÂGa, is lost abruptly at Namibe, and beach sands further north have abundant feldspar, amphibole-epidote suites and unimodal zircon-age spectra with a peak at ca 2·0ÂGa, documenting local provenance from Palaeoproterozoic basement. Along with this oblique-rifted continental margin, beach placers are dominated by Fe–Ti–Cr oxides with more monazite than garnet and thus have a geochemical signature sharply different from beach placers found all the way along the Orange littoral cell. High-resolution mineralogical studies allow us to trace sediment dispersal over distances of thousands of kilometres, providing essential information for the correct reconstruction of ‘source to sink’ relationships in hydrocarbon exploration and to predict the long-term impact of man-made infrastructures on coastal sediment budgets.

The subequatorial Angolan continental margin offers excellent conditions to test textbook theories on the composition of passive-margin sediments generated in different climatic and tectonic regimes. We use here comprehensive petrographic, heavy-mineral, geochemical and zircon-geochronology datasets on modern fluvial, beach, shelfal, and deep-marine sands and muds collected from hyperarid northern Namibia to hyperhumid Congo to investigate and assess: a) how faithfully sand mineralogy reflects the lithological and time structures of source rocks in a tectonically active rifted margin; b) in what climatic and geomorphological conditions the mark of chemical weathering becomes strong and next overwhelming; and, c) to what extent the effect of weathering can be isolated from quartz dilution by recycling of older siliciclastic strata and other physical controls including hydraulic sorting and mechanical wear. A new refined classification of feldspatho-quartzose and quartzose sands and sandstones is proposed. First-cycle quartzo-feldspathic to feldspar-rich feldspatho-quartzose sand eroded from mid-crustal granitoid gneisses of the Angola Block exposed in the dynamically uplifted Bie-Huila dome is deposited in arid southern Angola, whereas quartz-rich feldspatho-quartzose to quartzose sand characterizes the lower-relief, less deeply dissected, and more intensely weathered rifted margin of humid northern Angola. Pure quartzose, largely recycled sand is generated in the vast, low-lying hyperhumid continental interiors drained by the Congo River. The progressive relative increase of durable minerals toward the Equator results from three distinct processes acting in accord: active tectonic uplift in the arid south, and progressively stronger weathering coupled with more extensive recycling in the humid north. The quartz/feldspar ratio increases and the plagioclase/feldspar ratio decreases rapidly in first-cycle sand generated farther inland in the Catumbela catchment, reflecting stronger weathering in wet interior highlands. Discriminating weathering from recycling control is difficult in northern Angola. Although textural features including deep etch pits even on relatively resistant minerals such as quartz and microcline or rounded outline and abraded overgrowths provide valuable independent information, recycling remains as a most elusive problem in provenance analysis of terrigenous sediments.

The Chinese Loess Plateau, the world’s largest and oldest loess record, preserves evidence of Asia’s long-term dust source dynamics, but there is uncertainty over the source of the deposits. Recent single-grain detrital zircon U-Pb age analysis has progressed this issue, but debates remain about source changes, and the generation and interpretation of zircon data. To address this, we analyze different groupings of new and existing datasets from the Loess Plateau and potential sources. We also present the results of a first high resolution sampling, multi-proxy provenance analysis of Beiguoyuan loess using U-Pb dating of detrital zircons and detrital garnet geochemistry. The data shows that some small source differences seem to exist between different areas on the Loess Plateau. However, sediment source appears to be unchanging between loess and palaeosols, supporting a recent material recycling hypothesis. Our zircon and garnet data demonstrates, however, that Beiguoyuan experienced a temporary, abrupt source shift during the last glacial maximum, implying that local dust sources became periodically active during the Quaternary. Our results highlight that grouping data to achieve bigger datasets could cause identification of misleading trends. Additionally, we suggest that multi-proxy single-grain approaches are required to gain further insight into Chinese Loess Plateau dust sources.

Subduction complexes large enough to be exposed subaerially and become significant sources of terrigenous detritus are formed by tectonic accretion above trenches choked with thick sections of remnant-ocean turbidites. They thus need to be connected along strike to a major collision zone, where huge volumes of orogenic detritus are produced and conveyed via a major fluvio-deltaic system to the deep sea. In this article we investigate sediment generation and recycling in the archetype of such settings, the eastern prolongation of the Himalayan collisional system. We illustrate the petrographic and heavy-mineral suites of modern sands produced all along the Indo-Burman-Andaman-Nicobar subduction complex, which includes accreted abyssal-plain sediments overthrust by ophiolites and unconformably overlain by volcaniclastic forearc strata. "Subduction Complex Provenance" is thus composite, and overwhelmingly consists of detritus recycled from largely turbiditic parent rocks (Recycled Clastic Provenance), with local supply from obducted ultramafic and mafic rocks of forearc lithosphere (Ophiolite Provenance) or recycled paleovolcanic to neovolcanic sources (Volcanic Arc Provenance). In order to specifically investigate the effect of recycling, we characterize the diverse detrital signatures of Cenozoic sandstones originally deposited during subsequent stages of "soft" and "hard" Himalayan collision and presently exposed from Bangladesh to the Andaman Islands, and discuss the reasons for compositional discrepancies between parent sandstones and their recycled daughter sands. Long-distance, multistep and multicyclic sediment transfer along and across convergent plate boundaries follows complex trajectories in space and time, which must be resolved whenever we want to obtain a reasonably faithful paleogeographic reconstruction for the recent and less recent geological past. © 2013 Elsevier B.V.

We used petrographic, heavy-mineral, and geochronological signatures of sand-sized grains to document an exceptional case of long-distance sediment transport dominated by eolian processes in a hyperarid climate. Feldspatho-quartzo-lithic orogenic detritus shed by the Anatolia Plateau and Zagros Mountains-including carbonate, chert, volcanic, metabasite, and ultramafic lithic grains with a rich epidote-amphibole-pyroxene-garnet heavy-mineral suite-was carried to the Arabian-Gulf foreland basin via the Euphrates-Tigris-Karun fluvial system and other rivers draining the Zagros, and blown inland by dominant Shamal winds to reach well into the Arabian foreland. Sediment dispersal over a cumulative distance of up to 4000 km took place in multiple steps, involving extensive eolian reworking of older deposits during lowstand stages of the Pleistocene before final accumulation in the Rub' al Khali sand sea. The siliciclastic fraction of Gulf beaches changes southeastwards from litho-quartzose carbonaticlastic and quartzose north of Qatar to quartzo-lithic carbonaticlastic along the Trucial Coast, but invariably contains chert, volcanic, and metabasite lithics, together with epidote, pyroxene, amphibole, and garnet. Dune sand inland is progressively enriched in quartz until composition becomes feldspatho-quartzose, whereas the heavy-mineral assemblage remains virtually unchanged. Beach and dune sands of the Gulf and northeastern Rub' al Khali were derived from Arabia, Anatolia, and the Zagros in varying proportions, with only local contribution from ophiolites of the northern Oman Mountains as revealed by cellular serpentinite and enstatite grains. In all samples detrital zircons yielded mostly Cambrian to Neoproterozoic ages reflecting "Pan-African" crustal growth and amalgamation of the Arabian shield, but several upper Paleozoic, Mesozoic, and Cenozoic zircons with ages as young as 5 Ma in northeastern Rub' al Khali dunes document ultimate provenance from the Anatolia-Zagros orogen. Quartzose dune sand of the southwestern Rub' al Khali, containing a moderately poor, amphibole-rich heavy-mineral assemblage and very few young zircons, is dominantly Arabian-derived. Relatively soft carbonate grains are typically concentrated in finer sand classes, which is ascribed to both mixing with coarser quartz recycled from Arabian siliciclastic covers and selective mechanical wear during multicyclic long-distance transport in high-energy eolian environments. Understanding the complex transfer of huge detrital masses on the Earth's surface, and mixing of sediments derived from different sources along successive tracts of a composite routing system that may cover cumulative distances of thousands of kilometers across climatic and tectonic boundaries over time periods of millions of years, is essential to enhance the resolution of source-to-sink studies and avoid gross oversimplifications in paleogeographic reconstructions.

A practical classification of surface textures observed on detrital grains in sands and sandstones is proposed, in order to enhance data reproducibility among operators and to implement the use of high-resolution heavy-mineral data in studies of sediment-generation, provenance, and diagenesis. Five stages of progressive weathering (unweathered, corroded, etched, deeply etched, skeletal) are recognized for diverse detrital minerals. Archetypal grains displaying increasing degrees of corrosion are illustrated in numerous color tables for visual comparison. This catalog, specifically devised to systematically collect valuable information for paleoclimatic or diagenetic interpretation during routine grain-counting under the microscope, is here shown to represent a useful subsidiary tool to reveal the different degrees of weathering for diverse minerals in modern sands of equatorial Africa, and to identify post-depositional modifications of detrital assemblages in buried orogenic sediments of the Bengal Basin. The data thus obtained need to be interpreted by carefully considering the concentration of heavy minerals in each sample, which provides the fundamental clue to quantify the degree of heavy-mineral depletion caused by either pre-depositional or post-depositional processes. The scrutiny of dissolution effects has applications in the study of the chemical properties of minerals and of diagenetic evolution, helping us to understand the development of secondary porosity and to assess the potential of water and hydrocarbon reservoirs.

We present a detailed sediment-provenance study on the modern Euphrates-Tigris-Karun fluvial system and Mesopotamian foreland basin, one of the cradles of humanity. Our rich petrographic and heavy-mineral dataset, integrated by sand geochemistry and U–Pb age spectra of detrital zircons, highlights the several peculiarities of this large source-to-sink sediment-routing system and widens the spectrum of compositions generally assumed as paradigmatic for orogenic settings. Comparison of classical static versus upgraded dynamic petrologic models enhances the power of provenance analysis, and allows us to derive a more refined conceptual model of reference and to verify the limitations of the approach. Sand derived from the Anatolia-Zagros orogen contains abundant lithic grains eroded from carbonates, cherts, mudrocks, arc volcanics, obducted ophiolites and ophiolitic melanges representing the exposed shallow structural level of the orogen, with relative scarcity of quartz, K-feldspar and mica. This quartz-poor petrographic signature, characterizing the undissected composite tectonic domain of the entire Anatolia-Iranian plateau, is markedly distinct from that of sand shed by more elevated and faster-eroding collision orogens such as the Himalaya. Arid climate in the region allows preservation of chemically unstable grains including carbonate rock fragments and locally even gypsum, and reduces transport capacity of fluvial systems, which dump most of their load in Mesopotamian marshlands upstream of the Arabian/Persian Gulf allochemical carbonate factory. Quartz-poor sediment from the Anatolia-Zagros orogen mixes with quartz-rich recycled sands from Arabia along the western side of the foreland basin, and is traced all along the Gulf shores as far as the Rub' al-Khali sand sea up to 4000 km from Euphrates headwaters.

We use quantitative provenance analysis (geochemical analysis; high- resolution bulk-petrography and heavy-mineral analysis, exploratory compositional data analysis and Aitchison distance) on present-day river sediments of the Changjiang (Yangtze) River to quantify the contributions of each tributary to the Changjiang River Delta, and thus to evaluate sediment provenance in the distinct p arts of the drainage basin.

International audience; River sediments naturally sample and average large areas of eroded continental crust. They are ideal targets not only for provenance studies based on isotopic compositions, but also can be used to establish average continental crust isotopic values. In large fluvial systems, however, mineral sorting processes significantly modify the mineralogy, and thus the geochemistry of the transported sediments. We still do not know, in any quantitative way, to what extent mineral sorting affects and fractionates the isotopic compositions of river sediments. Here, we focus on this issue and try to decipher the role of each mineral species in the bulk isotopic compositions of bedloads and suspended loads sampled at the outflow of the Ganga River that drains the Himalayan mountain range.We analyzed Nd, Hf, Sr, and Pb isotopic compositions as well as trace element contents of a large number of pure mineral fractions (K-feldspar, plagioclase, muscovite, biotite, magnetite, zircon, titanite, apatite, monazite/allanite, amphibole, epidote, garnet, carbonate and clay) separated from bedload and bank sediments. We combine these data with mineral proportions typical of the Ganga sediments to perform Monte Carlo simulations that quantify the contributions of individual mineral species to the Nd, Hf, Sr, and Pb isotopic budgets of bedloads and suspended loads.The isotopic systematics of river sediments are buffered by very few minerals. Despite their extremely low proportions in sediments, zircon and monazite/allanite control Hf and Nd isotopes, respectively. Feldspars, epidote, and carbonate buffer the Sr isotopic budget while clay, feldspars, and heavy minerals dominate Pb isotopes. Hafnium, Sr, and Pb isotopic differences between bedloads and suspended loads are well explained by their different mineral compositions. This confirms that Hf, Sr and Pb isotopic compositions of sediments are strongly biased by mineral sorting processes during fluvial transport; hence they do not always constitute good proxies for provenance studies. In addition, we anticipate that fractionation of the isotopic systems continues at the river/ocean interface to deliver sediments to the deep ocean that are not necessarily similar to their crustal precursors, creating a systematic bias between the compositions of crustal sources and oceanic sediments.

The Indus River, one of Asia’s premier rivers, drains the western Tibetan Plateau and the Nanga Parbat syntaxis. These two areas juxtapose some of the lowest and highest topographic relief and commensurate denudation rates in the Himalaya-Tibet orogen, respectively, yet the spatial pattern of denudation rates upstream of the syntaxis remains largely unclear, as does the way in which major rivers drive headward incision into the Tibetan Plateau. We report a new inventory of ^(10)Be-based basinwide denudation rates from 33 tributaries flanking the Indus River along a 320 km reach across the western Tibetan Plateau margin. We find that denudation rates of up to 110 mm k.y.^(–1) in the Ladakh and Zanskar Ranges systematically decrease eastward to 10 mm k.y.^(–1) toward the Tibetan Plateau. Independent results from bulk petrographic and heavy mineral analyses support this denudation gradient. Assuming that incision along the Indus exerts the base-level control on tributary denudation rates, our data show a systematic eastward decrease of landscape downwearing, reaching its minimum on the Tibetan Plateau. In contrast, denudation rates increase rapidly 150–200 km downstream of a distinct knickpoint that marks the Tibetan Plateau margin in the Indus River longitudinal profile. We infer that any vigorous headward incision and any accompanying erosional waves into the interior of the plateau mostly concerned reaches well below this plateau margin. Moreover, reported long-term (>10^6 yr) exhumation rates from low-temperature chronometry of 0.1–0.75 mm yr^(–1) consistently exceed our ^(10)Be-derived denudation rates. With averaging time scales of 10^3–10^4 yr for our denudation data, we report postglacial rates of downwearing in a tectonically idle landscape. To counterbalance this apparent mismatch, denudation rates must have been higher in the Quaternary during glacial-interglacial intervals.