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 1800 km 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 0·5 Ga and ca 1·0 Ga, 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 2·0 Ga, 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.

Despite the influence of other geological and geomorphological factors, 20 chemical weathering at the Earth's surface is strongly controlled by climate. Thus, a 21 measure of weathering intensity determined from soils or sediments should provide information about the climatic conditions associated with their formation. Available 23 geochemical and mineralogical data on modern fluvial and marine muds from different 24 regions of southern Africa and its Atlantic continental margin are used to review the 25 links between sediment composition and climatic properties together with the 26 possible causes of variance. Although river muds may not be generated exclusively in a 27 single sedimentary cycle and erosion and weathering processes do not necessarily take 28 place in a spatially homogeneous way, significant relationships between mineralogical 29 and geochemical signatures of river mud and rainfall in the corresponding catchment 30 area were recognised. Our study shows that the composition of clay is strongly 31 influenced by climatically-driven weathering, whilst coarser mud fractions tend to be 32 more affected by provenance, grain size, hydraulic sorting, and recycling. In the marine 33 environment the climatic signal may be lost even in clay, because of hydraulic 34 fractionation, authigenic mineral growth and mixing with foreign particles. Given the 35 ubiquitous character of fluvial muds, and the easy and non-expensive methods 36 available for separating and analysing clay fractions, their geochemical fingerprints 37 represent a most precious source of information concerning climate. Any geochemical 38 parameter used as a regional proxy of climate, however, still requires that the diversity 39 of geological, geomorphological, and biological factors that affect its value are 40 cautiously considered.

In the modern era, due to the rapid increase in urbanization and industrialization in the vicinity of the Himalayas, heavy metals contamination in soil has become a key priority for researchers working globally; however, evaluation of the human and ecological risks mainly in hilly areas remains limited. In this study, we analyzed indices like the contamination factor (CF), degree of contamination (DC), enrichment factor (EF), geochemical index (Igeo), pollution ecological risk index (PERI), and pollution load index (PLI), along with cancer risk (CR) and hazard indices (HI), to ascertain the eco-environmental and human risks of using heavy metals in datasets collected from 168 sampling locations in Uttarakhand, India. The evaluation calculated of Igeo, EF, and CF suggests that represented soil samples were moderately contaminated and highly augmented with Rb, while PERI (75.56) advocates a low ecological risk. Further, PLI and DC (PLI: 1.26; DC: 36.66) show a possible health risk for the native population in the vicinity of the studied catchment. The hazard index (HI) is estimated greater than 1 (HI > 1) for Cr and Mn, representing a possible risk for cancer. However, adults are free from cancer risk, and other studied elements have been reported as noncarcinogenic. This assessment gives important information to policymakers, environmentalists, and foresters for taking mitigation measures in advance to mitigate the potential future risk of soil pollution on humans, ecology, and the environment.

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 SiO 2 , 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 windblown 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.

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a b s t r a c tWe present the results of K-feldspar IRSL dating of the four lower terraces (T3-T6) of the Portuguese Tejo River, in the Arripiado-Chamusca area. Terrace correlation was based upon: a) analysis of aerial photographs, geomorphological mapping and field topographic survey; b) sedimentology of the deposits; and c) luminescence dating. Sediment sampled for luminescence dating gave unusually high dose rates, of between 3.4 and 6.2 Gy/ka and, as a result, quartz OSL was often found to be in saturation. We therefore used the IRSL signal from K-feldspar as the principal luminescence technique. The K-feldspar age results support sometimes complex geomorphic correlations, as fluvial terraces have been vertically displaced by faults (known from previous studies). Integration of these new ages with those obtained previously in the more upstream reaches of the Tejo River in Portugal indicates that the corrected K-feldspar IRSL ages are stratigraphically and geomorphologically consistent over a distance of 120 km along the Tejo valley. However, we are sceptical of the accuracy of the K-feldspar ages of samples from the T3 and T4 terraces (with uncorrected D e values >500 Gy). In these cases the Dose Rate Correction (DRC) model puts the natural signals close to luminescence saturation, giving a minimum corrected D e of about 1000 Gy, and thus minimum terrace ages; this may even be true for those doses >200 Gy. Luminescence dating results suggest that: T3 is older than 300 ka, probably ca. 420-360 ka (wMarine Isotope Stage [MIS]11); T4 is ca. 340-150 ka (wMIS9-6); T5 is 136-75 ka (wMIS5); T6 is 60-30 ka (MIS3); an aeolian sand unit that blankets T6 and some of the older terraces is 30-12 ka. Collectively, the luminescence ages seem to indicate that regional river downcutting events may be coincident with periods of low sea level (associated, respectively, with the MIS10, MIS6, MIS4 and MIS2).

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 zircongeochronology 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 *Revised manuscript with no changes marked Click here to view linked References "The present is the key to the past" Archibald Geikie, The Founders of Geology "From this gateway Moment a long eternal lane stretches backward: behind us lies an eternity. Must not what ever can happen, already have happened, been done, passed by before? And if everything has already been here before, what do you think of this moment, dwarf? " Friedrich Nietzsche, Thus Spoke Zarathustra, On the Vision and the Riddle. 9 mineral assemblages and chemical-weathering proxies in river muds (Dinis et al., 2017). Kaolinite, supplied in abundance to the coast by most major Angolan rivers, is largely generated in the wet hinterland, and particularly on ancient flat surfaces decreasing in elevation westward and separated by escarpments of variable relief. Expansive clays, instead, are mainly formed in Meso-Cenozoic basins located in dryer areas along the coast. As a consequence, the smectite/kaolinite ratio is  1 in arid southern Angola, decreases rapidly in the semiarid Benguela region, and is very low in the more humid north with the exception of muds carried by the Longa, Cuanza, and Bengo rivers cutting across the Meso-Cenozoic Cuanza basin in their lower course. 2.5. River systems Apart for the Congo (4,000,000 km 2 , length 4700 km), the largest Angolan rivers draining into the Atlantic Ocean are the Cunene ( 110,000 km 2 ,  1050 km) and the Cuanza ( 150,000 km 2 ,  960 km). The Longa, Queve, Curoca, and Mebridege are  300 km-long and drain  20,000 km 2 each; the Catumbela and Coporolo are 200-250 km-long and drain  15,000 km 2 (Fig. 1B). Of similar length are the Loge, Dande, Bengo, and Bero, which also drain more than 10,000 km 2 each, and another dozen ephemeral rivers draining between 2000 and 7000 km 2. Three major rivers are sourced in the very same area between the cities of Huambo and Katchiungo at  1800 m a.s.l. on the dynamically uplifted Bié-Huila dome: the Queve draining northward, the Cunene draining southward, and the Cubango branch of the Okavango draining southeastwards across the Kalahari (Fig. 1). The Cuanza is instead sourced in the Kalahari and flows northwards around the Angola Block. These river courses may have formed soon after opening of the South Atlantic, although the modern configuration with radial drainage of the Biè-Huila dome was acquired much more recentl...

Geochemical mapping is frequently used to identify the regions of the Planet with critical chemical elements and their natural or anthropogenic sources. In order to understand elements' geochemistry and to identify the area's potentially harmful associations, high‐resolution maps of chemical elements, physico‐chemical parameters, a noncarcinogenic hazard index, and a potential ecological risk index were modelled with soil samples collected in the Himalaya region. It is the first environmental and geochemical atlas for this region. It was found that natural processes are determining the distribution of the variable in this area. The granulometric features seem to be strongly influenced by land use, with coarser grain sizes in forest soils, contrasting with the finer grain sizes in agricultural soils. The map distribution of the noncarcinogenic hazard index showed that there is an expected hazard for some variables for both children and adults. Potential ecological risk is revealed to be low to moderate. Remediation of contaminated soils is necessary to reduce the associated risks, make the land resource available for agricultural production, enhance food security, and scale down land tenure problems arising from changes in the land use pattern. This study is subsequent implementation of natural‐based approaches to system stability in largely unspoilt area.