Search

High-resolution petrographic and heavy-mineral analyses of Bengal Fan turbidites from six cores drilled during IODP Expeditions 353 and 354 elucidate factors controlling their intersample compositional variability as a key to understanding sedimentary processes and erosional evolution of the Himalayan belt since the Miocene. Bengal Fan turbidites are feldspatho-quartzose to litho-feldspatho-quartzose with plagioclase > K-feldspar; slow-settling micas increase in abundance in very fine sand and coarse silt. The feldspar/quartz ratio and higher-rank metamorphic rock fragments notably increase from uppermost Miocene to Pleistocene deposits, which is ascribed to the onset of rapid exhumation of the Eastern Himalayan syntaxis since ∼ 5 Ma. The same trends are documented in Nicobar Fan turbidites, confirming that they belong to the same sedimentary system. Both Bengal and Nicobar fans record a pulse in mass accumulation rate at Tortonian times, when supply of sedimentary and very-low-grade metasedimentary detritus reflected accelerated exhumation of the Lesser Himalaya. In contrast to foreland-basin sediments, where ferromagnesian minerals have been completely dissolved in strata as young as Pliocene–Pleistocene, in both Bengal–Nicobar and Indus fans amphibole invariably represents about half of the moderately rich to rich transparent-heavy-mineral suite, demonstrating that amphibolite-facies Greater Himalaya metamorphic rocks were widely exposed in the Himalayan range well before the late Miocene and possibly since the late Oligocene, as indicated by a few sillimanite and kyanite grains in Bengal Fan sediments as old as 23 Ma and 28 Ma, respectively. Diagenetic dissolution strongly affected olivine and pyroxene in strata older than the middle and early Pleistocene, respectively, whereas amphibole decreases markedly through progressively older Miocene strata. Ferromagnesian minerals and sillimanite are almost completely dissolved in lower Miocene strata, where durable zircon, tourmaline, rutile, and apatite make up half of the strongly depleted heavy-mineral assemblage. Quaternary turbidites from the six studied cores have virtually the same compositional signatures, testifying to efficient homogenization by turbidite transport and reworking across the fan. Turbidites in western cores closer to peninsular India (U1444A and U1454B) are not different from those in eastern cores, indicating very minor supply from the subcontinent. Forward-mixing calculations based on integrated petrographic and heavy-mineral data indicate that sand supply from the Brahmaputra River to Quaternary turbidites was four times larger than supply from the Ganga River, indicating up to six times higher sediment yields and erosion rates in the Brahmaputra than in the Ganga catchment, largely reflecting superfast erosion of the Eastern Himalayan syntaxis.

This study illustrates the clay mineralogy and sedimentary geochemistry of the Red River and its major tributaries and distributaries in northern Vietnam and shows how these methods can be used to unravel grain size, provenance, hydraulic-sorting, and chemical weathering effects. All sand samples are SiO2-rich and consequently depleted in most chemical elements (but Sn and Pb) relative to the upper continental crust (UCC). The order of element mobility indicated by αAlE values, which estimate the degree of depletion in mobile element E relative to the UCC standard, is Ca ≥ Na > Sr > Mg > Ba ≥ K ≥ Rb. In mud fractions, SiO2 decreases, and other elements consequently increase. The grain size-dependent intrasample chemical variability of fluvial sediments reflects the grain size distribution of detrital minerals, which is strictly controlled in turn by the settling-equivalence principle. The 87Sr/86Sr ratio in Red River sands varies widely between 0.716 and 0.748, and εNd ranges from −8.5 to −13.8. The negative εNd values and high 87Sr/86Sr ratios point at a significant contribution from Precambrian crystalline basement, directly or through recycling of Triassic siliciclastic strata. Clay-mineral assemblages, dominated by illite and smectite with subordinate kaolinite and minor chlorite, suggest largely physical erosion in the upper catchment and stronger weathering in the monsoon-drenched lower catchment. Extremely intense weathering is demonstrated by a Quaternary soil sample from the Red River valley in northernmost Vietnam, which is a pure quartzose sand yielding a tourmaline-dominated heavy-mineral suite and a kaolinite-dominated clay-mineral assemblage. In the humid landscapes of northern Vietnam, no detrital mineral, excepting quartz, muscovite, tourmaline, prismatic sillimanite, anatase, and zircon, can resist even shallow early pedogenesis.

We here present the first comprehensive provenance study of the Zambezi deep-sea fan, based on integrated petrographic, heavy-mineral, elemental-geochemistry, isotope-geochemistry, and detrital-zircon-geochronology analyses of middle Pleistocene to Holocene turbidites. The Zambezi Valley and Fan represent the submarine part of an ∼ 5000-km-long sediment-routing system, extending from the heart of the South African Plateau to the abyssal depths of the Indian Ocean. Sediment is derived not only from the African side, but also from Madagascar Island mostly via the Tsiribihina Valley. Being shed by two dissected rifted margins, detritus supplied from opposite sides of the Mozambique Channel shares similar feldspar-rich feldspatho-quartzose composition, although with significant differences in heavy-mineral and geochemical signatures. The εNd values of Madagascar sand are markedly more negative and TNd model ages notably older. Zircon grains yield mostly Irumide (late Stenian) U-Pb ages in African-derived sand and mostly Pan-African (Ediacaran–Cryogenian) U-Pb ages in Madagascar-derived sand, which also yields a few grains as old as Paleoarchean and many discordant ages reflecting Pan-African reworking of Archean cratonic rocks. Lower Valley and Lower Fan deposits have intermediate fingerprints, indicating that sediment supply from Madagascar is not much less than from Africa despite a much smaller catchment area, which can be explained by deposition of a conspicuous part of Africa-derived sediment in the Intermediate Basin confined between the Zambezi Shelf, the Beira High, and the Îles Éparses. By assuming that compositional differences between Quaternary submarine deposits and modern Zambezi River sands primarily resulted from sediment impoundment by large dams, we could evaluate the anthropogenic impact on natural sediment fluxes. Quaternary turbidites are somewhat higher in quartz and poorer in heavy minerals with higher relative amounts of durable ZTR species, and yield more Ediacaran, Neoarchean, and Carboniferous detrital-zircon ages than modern river sands. The Orosirian peak characterizing the Intermediate Basin sample points to prominent supply from the middle and upper parts of the Zambezi catchment in the middle Pleistocene. Rough calculations suggest that pre-dam Zambezi sediments were generated ≤ 10% in the upper catchment, ∼ 60% in the middle catchment, and only ≥ 30% in the lower catchment that provides the totality of sediment reaching the Indian Ocean today.

The relative roles of tectonics and climate change in global and regional desertification are not well constrained. Previous studies have emphasized the role played by climate change as a dominant cause of southeastern (SE) Asia desertification during the mid-Late Cretaceous. The effect of early uplift of the Tibetan Plateau prior to the collision between Eurasia and India on regional desertification remains poorly understood. We present a comprehensive set of provenance data on two aeolian sequences deposited in the Simao Basin and Khorat Plateau desert environments adjacent to southeast Tibet. Our provenance results suggest that the aeolian sandstones of the Pashahe Formation in the Simao Basin were largely recycled from exposed sedimentary rocks of the Songpan-Garze terrane, Southern Qiangtang terranes, and northern Yangtze Block with minor contributions from the magmatic rocks of the Tengchong and Southern Qiangtang terranes. Combined with other evidence, provenance results indicate the source areas started to grow and to be rapidly unroofed and determined the birth of the transcontinental southerly flowing paleo-river, which carried the sand to be stored. In contrast, the Phu Thok aeolian sandstones in the Khorat Plateau were predominantly sourced from the exposed Sibumasu igneous rocks together with recycled detritus in the Sukhothai Arc terrane, which was possibly transported by a local river. Hence, our thesis is that elevated topography caused by the closure of the Bangong-Nujiang Mesotethys profoundly affected the atmospheric circulation and drainage development, leading to mid-Late Cretaceous desertification across SE Asia.

Elemental geochemistry, Nd isotopes, clay minerals, and U-Pb zircon ages integrated by petrographic and heavy-mineral data offer a multi-proxy panorama of mud and sand composition across the Zambezi sediment-routing system. Detrital-zircon geochronology highlights the four major episodes of crustal growth in southern Africa: Irumide ages predominate over Pan-African, Eburnean, and Neoarchean ages. Smectite, dominant in mud generated from Karoo basalts or in the equatorial/winter-dry climate of Mozambican lowlands, prevails over illite and kaolinite. Elemental geochemistry reflects quartz addition by recycling (Uppermost Zambezi), supply from Karoo basalts (Upper Zambezi), and first-cycle provenance from Precambrian basements (Lower Zambezi). Mildly negative for sediments derived from mafic granulites, gabbros, and basalts, åNd values are most negative for sand derived from cratonic gneisses. Intrasample variability among cohesive mud, very coarse silt, and sand is principally caused by the concentration of Nd-rich monazite in the fine tail of the size distribution. The settling-equivalence effect also explains deviations from the theoretical relationship between åNd and TNd,DM model ages, suggesting that monazite carries a more negative åNd signal than less dense and less durable heavy minerals. Elemental geochemistry and Nd isotopes reveal that the Mazowe-Luenha river system contributes most of the sediment reaching the Zambezi Delta today, with minor supply by the Shire River. Sediment yields and erosion rates are lower by an order of magnitude on the low-relief Kalahari Plateau than in rugged Precambrian terranes. On the Plateau, mineralogical and geochemical indices testify to extensive breakdown of feldspars and garnet unjustified by the presently dry climate. Detrital kaolinite is recycled by incision of Cretaceous- Cenozoic paleosols even in the wetter lower catchment, where inefficient hydrolysis is testified by abundant fresh feldspars and undepleted Ca and Na. Mud geochemistry and surficial corrosion of ferromagnesian minerals indicate that, at present, weathering increases only slightly downstream the Zambezi River.

The Zagros orogen, formed by the collision of the Arabian and Eurasian continental margins, represents one of the largest and richest oil and gas provinces in the world. The Zagros fold-thrust belt records collision and convergence along the Neotethys suture zone. By coupling field observations, sandstone modal analysis, U-Pb zircon dating, and Hf isotopic data from the Upper Cretaceous to Pliocene sedimentary succession of the Neyriz region, this paper documents several major provenance changes that allow us to propose a refined scenario for the Zagros orogeny. An ophiolitic complex dated by detrital-zircon U-Pb geochronology as ca. 95 Ma provided detritus to Upper Cretaceous-Paleocene strata deposited along the northeastern margin of the Arabian lower plate (ophiolite provenance). Yet, on the southwestern margin of the Eurasian upper plate, upper Paleocene-lower Eocene strata indicate provenance from Mesozoic magmatic rocks yielding zircons dated as ca. 240 Ma and 170 Ma as well as the recycling of clastic rocks. Since the early Miocene, the sedimentary basin located on the Arabian plate received both ophiolitic detritus and magmatic-arc, recycled clastic, and axial-belt metamorphic detritus from Eurasia. U-Pb ages of detrital zircons reflect polyphase magmatism at 170 Ma, 95 Ma, and 40 Ma on the Eurasian active margin. Our results indicate that progressive accretion, uplift, and exhumation of the Zagros orogen was well under way by the beginning of the Miocene in the Neyriz region. Literature data from adjacent regions suggest that the Arabia/Eurasia collision may have occurred diachronously and later in the Kermanshah and Lurestan areas to the north.

The Yarlung Tsangpo, draining the Himalayan-Tibetan orogen along the Indus-Yarlung suture zone, receives detritus from the deformed remnants of both Indian margin to the south and Asian margin to the north. High resolution petrographic, heavy-mineral and geochemical datasets, combined with published geochronological data, allow us to monitor compositional changes, estimate erosion rates and investigate lithologic, climatic and anthropic controls on sediment fluxes along this large sediment-routing system entirely developed within high mountain areas. Sediment generated from the Lhasa Block along the southern margin of Asia is characterized by abundant feldspar and volcanic rock fragments, amphibole-dominated transparent heavy mineral suite and high concentrations of K, Rb, Be, Th and Pb. Himalayan-derived sand, instead, is characterized by sedimentary to low-rank metasedimentary rock fragments, poor transparent heavy mineral suite dominated by durable recycled (zircon, tourmaline) or metamorphic minerals (chloritoid, garnet) and high Ca concentration. Sand from the ophiolitic suture is distinguished by serpentinite grains and mafic volcanic or metavolcanic detritus, transparent heavy mineral suite including olivine, Cr-spinel, enstatite and clinopyroxene, and high Mg, Cr, Ni and low rare earth elements. Himalayan detritus is prominent in Yarlung Tsangpo upper reaches, whereas detritus from the Lhasa Block becomes progressively predominant in the middle and lower reaches. Provenance budgets based on integrated petrographic, heavy-mineral and geochemical datasets indicate that ca. 83% of the detritus is supplied by the Lhasa Block and the rest mostly from the Himalaya (ca. 12%) and subordinately from the ophiolitic suture (5%). A low average erosion rate of ca. 0.06mm/a was estimated for the Yarlung Tsangpo catchment upstream of the Namche Barwa syntaxis, which resulted from dry climate, relatively mild average relief and sediment storage in wide valley tracts of the middle and lower reaches. The decrease in sediment flux recorded in recent decades is mainly ascribed to growing human activities, which are becoming a prominent control on sediment generation and transportation even in the high-mountain area of South Tibet.

The 3-D seismic dataset is a key tool to analyze and understand the mechanism of structural and stratigraphic hydrocarbon (HC) trapping in the subsurface. Conventionally used subsurface seismic characterization methods for fractures are based on the theory of effective anisotropy medium. The aim of this work is to improve the structural images with dense sampling of 3-D survey to evaluate structural and stratigraphic models for reservoir development to predict reservoir quality. The present study of the Gullfaks Field, located in the Norwegian North Sea Gullfaks sector, identifies the shallowest structural elements. The steepness of westward structural dip decreases eastward during the Upper Jurassic to Lower Cretaceous deposition. Reservoir sands consist of the Middle Jurassic deltaic deposits and Lower Jurassic fluvial channel and delta plain deposits. Sediment supply steadily prevails on sea-level rise and the succession displays a regressive trend indicated by a good continuous stacking pattern. The key factor for the development of reservoirs in the Gullfaks Field is fault transmissibility with spatially distributed pressure. The majority of mapped faults with sand-to-sand contacts are non-sealing, which provide restriction for the HC flow between the fault blocks. The traps for HC accumulation occur between the post-rift and syn-rift strata, i.e. antiform set by extensional system, unconformity trap at the top of syn-deposition, and structural trap due to normal faults. Overall reservoir quality in the studied area is generally excellent with average 35% porosity and permeability in the Darcy range. Our findings are useful to better understand the development of siliciclastic reservoirs in similar geological settings worldwide.

There is no consensus about the geological nature of the westernmost portion of the Iberian Massif. In the present research, the detrital zircon U–Pb signatures of Jurassic strata of the Lusitanian Basin, known to be west-sourced, are combined with published U–Pb data for the Precambrian-Palaeozoic basement and otherLusitanian Basin units to better understand this poorly exposed portion of the Iberian Massif. Cryogenian to Ediacaran ages prevail in a northern Upper Jurassic unit, while Lower and Upper Jurassic rocks in southern locations yield mostly Carboniferous to upper Permian zircons. These age results, coupled with their respective U/Th ratios, suggest that the basin covers two distinct terranes of the Iberian Massif. Another noteworthy feature of west-derived deposits is the abundance of < 310Ma ages. It is proposed that a combination of crustal thinning in the West Iberian Margin with regional eastward basement tilt, favoured the enrichment of relatively young zircon in the western shoulder of the basin relative to its eastern margin. The detrital zircon age signatures also reveal a middle to late Permian thermal event in restricted areas, which is probably associated with the oldest stages of Alpine extension in West Iberia.

[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.

Widespread accumulation of thick carbonates is not typical of orogenic settings. During the mid-Cretaceous, near the Bangong suture in the northern Lhasa terrane, the shallow-marine carbonates of the Langshan Formation, reaching a thickness up to ~1 km, accumulated in an epicontinental seaway over a modern area of 132 × 103 km2, about half of the Arabian/Persian Gulf. The origin of basin-wide carbonate deposits located close to a newly formed orogenic belt is not well understood, partly because of the scarcity of paleogeographic studies on the evolution of the northern Lhasa. Based on a detailed sedimentological and stratigraphic investigation, three stages in the mid-Cretaceous paleogeographic evolution of northern Lhasa were defined: (1) remnant clastic sea with deposition of Duoni/Duba formations (Early to early Late Aptian, ca. 125–116 Ma); (2) expanding carbonate seaway of Langshan Formation (latest Aptian–earliest Cenomanian, ca. 116–99 Ma); and (3) closure of the carbonate seaway represented by the Daxiong/Jingzhushan formations (Early Cenomanian to Turonian, ca. 99–92 Ma). Combined with data on tectonic subsidence and eustatic curves, we emphasized the largely eustatic control on the paleogeographic evolution of the northern Lhasa during the latest Aptian–earliest Cenomanian when the Langshan carbonates accumulated, modulated by long-term slow tectonic subsidence and high carbonate productivity.

Provenance analysis of IODP Expedition 355 cores in the Laxmi Basin sheds new light on the erosional evolution of the Himalayan belt and its western syntaxis during the Neogene and on large-scale mass-wasting and magmatic events that affected the western continental margin of India in the mid-Miocene and early Paleocene. In the cored Laxmi Basin succession, heavy minerals are far less affected by selective diagenetic dissolution than in foreland-basin sandstones exposed along the Himalayan front. Occurrence of euhedral aegirine and apatite in lower Paleocene mudrocks can be tied to alkaline volcanism affecting the adjacent western Indian margin during the late stage of Deccan activity. In the mid-Miocene Nataraja Slide (the second-largest mass-transport deposit reported from passive margins worldwide), dominant carbonate detritus and depleted heavy-mineral suites (including apatite, garnet, and locally augite or rare aegirine) reveal gravitational failure and sliding of the entire succession of carbonate and siliciclastic Paleogene to lower Neogene strata originally accumulated offshore of the Saurashtra margin of western India. Contrary to previous inferences, reworking of Indus-derived detritus by the slide was negligible. The overlying upper Miocene to lower Pleistocene turbidite package has the same feldspatho-litho-quartzose to litho-feldspatho-quartzose signature of modern Indus fluvio-deltaic sand, indicating that amphibolite-facies metamorphic rocks have been widely exposed in the Himalaya–Karakorum orogen since at least the mid-Miocene. Pleistocene nannofossil oozes with planktonic foraminifera at the top of the fan contain a very subordinate litho-feldspatho-quartzose terrigenous fraction including augitic clinopyroxene, suggesting mixing of dominant biogenic debris with minor detritus contributed both by the Indus River and by a river draining western peninsular India, possibly the paleo-Narmada or the paleo-Tapti.

We here review what is known about the dunefields and fluvial systems of the Kalahari Basin in terms of geological setting and Quaternary dynamics and set out what has been hypothesized about the provenance of Kalahari sand so far. Previous work has tackled this problem by applying a limited number of techniques (mostly sediment textures and heavy minerals) to parts of the large dryland. The generally highly quartzose mineralogy of aeolian dunes and their compositional variability have been only broadly evaluated and several sedimentological issues have thus remained controversial, including the relative role played by fluvial processes versus aeolian reworking of older sediments and weathering controls. This reveals a need for a systematic provenance study that considers the entire basin. For this reason, here we combine original petrographic, heavy-mineral, and detrital-zircon geochronology data with previously published clay-mineral, geochemical, and geochronological information to present the first comprehensive provenance study of the vast Kalahari sand sea. Our multi-proxy dataset comprises 100 samples, collected across the Kalahari Basin from 11°S (NW Zambia) to 28°S (NW South Africa) and from 15°E (Angola) to 28°30′W (Zimbabwe). Kalahari aeolian-dune sand mostly consists of monocrystalline quartz associated with durable heavy minerals and thus drastically differs from coastal dunefields of Namibia and Angola, which are notably richer in feldspar, lithic grains, and chemically labile clinopyroxene. The western Kalahari dunefield of southeastern Namibia is distinguished by its quartz-rich feldspatho-quartzose sand, indicating partly first-cycle provenance from the Damara Belt and Mesoproterozoic terranes. Within the basin, supply from Proterozoic outcrops is documented locally. Composition varies notably at the western and eastern edges of the sand sea, reflecting partly first-cycle fluvial supply from crystalline basements of Cambrian to Archean age in central Namibia and western Zimbabwe. Basaltic detritus from Jurassic Karoo lavas is dominant in aeolian dunes near Victoria Falls. Bulk-sediment petrography and geochemistry of northern and central Kalahari pure quartzose sand, together with heavy-mineral and clay-mineral assemblages, indicate extensive recycling via aeolian and ephemeral-fluvial processes in arid climate of sediment strongly weathered during previous humid climatic stages in subequatorial Africa. Distilled homogenized composition of aeolian-dune sand thus reverberates the echo of paleo-weathering passed on to the present landscape through multiple episodes of fluvial and aeolian recycling. Intracratonic sag basins such as the Kalahari contain vast amounts of quartz-rich polycyclic sand that may be tapped by rivers eroding backwards during rejuvenation stages associated with rift propagation. Such an event may considerably increase the sediment flux to the ocean, fostering the progradation of river-fed continental-embankments, as documented by augmented accumulation rates coupled with upward increasing mineralogical durability in the post-Tortonian subsurface succession of the Zambezi Delta. The Central Kalahari is not a true desert. It has none of the naked, shifting sand dunes that typify the Sahara and other great deserts of the world. In some years the rains may exceed twenty — once even forty — inches, awakening a magic green paradise.” Mark Owens, Cry of the Kalahari.

The Zambezi River rises at the center of southern Africa, flows across the low-relief Kalahari Plateau, meets Karoo basalt, plunges into Victoria Falls, follows along Karoo rifts, and pierces through Precambrian basement to eventually deliver its load onto the Mozambican passive margin. Reflecting its polyphase evolution, the river is subdivided into segments with different geological and geomorphological character, a subdivision finally fixed by man’s construction of large reservoirs and faithfully testified by sharp changes in sediment composition. Pure quartzose sand recycled from Kalahari desert dunes in the uppermost tract is next progressively enriched in basaltic rock fragments and clinopyroxene. Sediment load is renewed first downstream of Lake Kariba and next downstream of Lake Cahora Bassa, documenting a stepwise decrease in quartz and durable heavy minerals. Composition becomes quartzo-feldspathic in the lower tract, where most sediment is supplied by high-grade basements rejuvenated by the southward propagation of the East African rift. Feldspar abundance in Lower Zambezi sand has no equivalent among big rivers on Earth and far exceeds that in sediments of the northern delta, shelf, and slope, revealing that provenance signals from the upper reaches have ceased to be transmitted across the routing system after closure of the big dams. This high-resolution petrologic study of Zambezi sand allows us to critically reconsider several dogmas, such as the supposed increase of mineralogical “maturity” during long-distance fluvial transport, and forges a key to unlock the rich information stored in sedimentary archives, with the ultimate goal to accurately reconstruct the evolution of this mighty river flowing across changing African landscapes since the late Mesozoic.

We analyzed the single-grain mineralogical composition of aeolian dust transported to central East Antarctica for provenance purposes. Comparison with data from the last glacial period shows for the first time disappearance of carbonates during the Holocene related to sea level rise and suppressed deflation from the Argentinean continental shelf, exposed during Marine Isotope Stage 2. Zeolites, related to alteration of volcanic glass in the subglacial/periglacial environment of Patagonia, show a similar behavior. The remaining minerals, remarkably similar between the two climatic periods, are compatible with a Pampean and Patagonian provenance, but Holocene data show a more pronounced volcanic and metamorphic imprint and presence of minerals related to warm climate weathering environments compatible with an additional contribution from subtropical latitudes of South America. These results do not imply a major large-scale reorganization of atmospheric circulation after the last climatic transition.

A multidisciplinary mineralogical, geochemical and biomarker study of Indus Fan sediments cored during International Ocean Discovery Program (IODP) Expedition 355 to the Laxmi Basin was carried out to define the different compositional signatures of sand, silt and clay. Upper Pliocene – lower Pleistocene turbidites from sites U1456 and U1457 were selected as the best candidates for this study. The integrated dataset presented here was obtained by coupling traditional and innovative bulk-sediment and single-mineral techniques on the same samples. Turbiditic deposits mostly consist of medium to fine silt, including rich and diverse heavy-mineral assemblages. Such a fine grain size forced us to push the limits of high-resolution quantitative heavy-mineral analysis down to as low as 5 μm. Heavy-mineral analysis allowed us to establish a Himalayan origin of the detritus in the studied turbidites. Heavy-mineral concentrations are higher in channel-fill than in overbank deposits. Mineralogical and geochemical data concur in revealing that fast-settling ultradense minerals such as zircon are preferentially concentrated in channel-fill deposits, whereas the top of overbank deposits are notably enriched with slow-settling platy phyllosilicates. Biomarker analysis represents a most suitable complementary technique that is able to investigate the provenance signature of the finer sediment fraction, largely consisting of clay. This technique allowed us to identify a largely terrigenous origin of organic matter at Site U1456 and an open marine origin at Site U1457. The latter site lies closer to the Laxmi Ridge, where thermal maturity increases with depth to reach the early oil window (127°C at c. 320 m below the seafloor).

This paper shows how heavy minerals and single-grain varietal studies can be conducted on silt (representing c. 50% of world's sediments) sediments to obtain quantitative data as efficiently as for sand-sized sediments. The analytical workflows include heavy mineral separation using a wide grain-size window (15–355 μ) analysed through integrated optical analysis, Raman spectroscopy, QEMSCAN microscopy and U–Pb dating of detrital zircon. Upper Jurassic–Cretaceous silt-sized sediments from the Mandawa Basin of central-southern Tanzania have been selected for the scope of this research. Raman-aided heavy mineral analysis reveals garnet and apatite to be the most common minerals together with durable zircon, tourmaline and subordinate rutile. Accessory but diagnostic phases are titanite, staurolite, epidote and monazite. Etch pits on garnet and cockscomb features on staurolite document the significant effect of diagenesis on the pristine heavy mineral assemblage. Multivariate statistical analysis highlights a close association among durable minerals (zircon, tourmaline and rutile, ZTR) while garnet and apatite plot alone reflecting independence between the three groups of variables with garnet increasing in Jurassic samples. Raman data for garnet end-member analysis document different associations between Jurassic (richer in A, Bi and Bii types) and Cretaceous (dominant A, Ci and Cii types) samples. U–Pb dating of detrital zircon and their statistical integration with the above-mentioned datasets provide further insights into changes in provenance and/or drainage systems. Metamorphic rocks of the early and late Pan-African orogeny terranes of the Mozambique Belt and those of the Irumide Belt acted as main source of sediment during the Jurassic. Cretaceous sediments record a broadening of the drainage system reaching as far as the Usagran–Ubendian Belt and the Tanzanian Archean Craton.

The Sahara is by far the largest hot desert on Earth. Its composite structure includes large dune fields hosted in sedimentary basins separated by elevated areas exposing the roots of Precambrian orogens or created by recent intraplate volcanism. Such an heterogeneity of landscapes and geological formations is contrasted by a remarkably homogeneous composition of dune sand, consisting almost everywhere of quartz and durable minerals such as zircon, tourmaline, and rutile.We here present the first comprehensive provenance study of the Sahara Desert using a combination of multiple provenance proxies such as bulk-petrography, heavy-mineral, and detrital-zircon U–Pb geochronology. A set of statistical tools including Multidimensional Scaling, Correspondence Analysis, Individual Difference Scaling, and General Procrustes Analysis was applied to discriminate among sample groups with the purpose to reveal meaningful compositional patterns and infer sediment transport pathways on a geological scale.Saharan dune fields are, with a few local exceptions, composed of pure quartz with very poor heavy-mineral suites dominated by durable zircon, tourmaline, and rutile. Some more feldspars, amphibole, epidote, garnet, or staurolite occur closer to basement exposures, and carbonate grains, clinopyroxene and olivine near a basaltic field in Libya. Relatively varied compositions also characterize sand along the Nile Valley and the southern front of the Anti-Atlas fold belt in Morocco. Otherwise, from the Sahel to the Mediterranean Sea and from the Nile River to the Atlantic Ocean, sand consists nearly exclusively of quartz and durable minerals. These have been concentrated through multiple cycles of erosion, deposition, and diagenesis during the long period of relative tectonic quiescence that followed the Neoproterozoic Pan-African orogeny, the last episode of major crustal growth in the region. The principal ultimate source of recycled sand is held to be represented by the thick blanket of quartz-rich sandstones that were deposited in the Cambro-Ordovician from the newly formed Arabian-Nubian Shield in the east to Mauritania in the west.The composition and homogeneity of Saharan dune sand reflects similar generative processes and source rocks, and extensive recycling repeated through geological time after the end of the Neoproterozoic, which zircon-age spectra indicate as the last major event of crustal growth in the region. The geographic zircon-age distribution in daughter sands thus chiefly reflects the zircon-age distribution in parent sandstones, and hence sediment dispersal systems existing at those times rather than present wind patterns. This leads to the coclusion that, provenance studies based on detrital-zircon ages, the assumption that observed age patterns reflect transport pathways existing at the time of deposition rather than inheritance from even multiple and remote landscapes of the past thus needs to be carefully investigated and convincingly demonstrated rather than implicitly assumed.

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.

The Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) was one of the major global deep-time hyperthermal events of the past. Studies of shallow-marine PETM records are crucial to understand the continental hydrological response to current global warming. This study presents the first detailed documentation of the PETM in the Xigaze forearc basin located along the northern active continental margin of the eastern Tethys Ocean, and illustrates the associated environmental and hydrological changes. Based on carbon-isotope stratigraphy, foraminiferal biostratigraphy, and zircon U Pb chronostratigraphy, the PETM event was identified within a siliciclastic unit in the largely calcareous Jialazi Formation. Foraminiferal assemblages of Shallow Benthic Zone 4 are present below the siliciclastic unit, but are replaced by Shallow Benthic Zone 6 assemblages above the siliciclastic unit. High-resolution microfacies analysis indicates that the pre-PETM deposits consist of carbonate-ramp sediments followed by a sudden change to syn-PETM siliciclastic rocks, followed in turn by renewed post-PETM carbonate-ramp deposition. The siliciclastic supply increased notably during the PETM, as indicated by the thickness of both sandstone and shale intervals, resulting in a temporary demise of the carbonate ramp. Provenance analysis does not indicate any major change in the source areas of terrigenous detritus through the early Paleogene. Increasing siliciclastic supply is thus chiefly ascribed to the intensification of seasonal precipitation and consequently increased hydrological circulation in the Gangdese arc during the PETM event.

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.