Provenance versus weathering control on the composition of tropical river mud (southern Africa)

Garzanti, Eduardo; Padoan, Marta; Setti, Massimo; López-Galindo, Alberto; Villa, Igor M.

doi:10.1016/j.chemgeo.2013.12.016

Cited by 207 publications

(103 citation statements)

References 75 publications

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“…This study illustrates an integrated petrographic, mineralogical, geochemical and geochronological dataset on modern sands collected along the entire Angolan continental margin, which complements data obtained with the same methods and following the same criteria during previous studies on sediment generation in southwestern Africa (Vermeesch et al, 2010;Garzanti et al, 2012aGarzanti et al, , 2014aGarzanti et al, , 2014bGarzanti et al, , 2014cGarzanti et al, , 2015Garzanti et al, , 2017Dinis et al, 2016Dinis et al, , 2017, to which the reader is referred as aspects specific to adjacent regions are concerned.…”

Section: Introductionmentioning

confidence: 53%

Dynamic uplift, recycling, and climate control on the petrology of passive-margin sand (Angola)

Garzanti

Dinis

Vermeesch

et al. 2018

Sedimentary Geology

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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...

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Section: Introductionmentioning

confidence: 53%

Dynamic uplift, recycling, and climate control on the petrology of passive-margin sand (Angola)

Garzanti

Dinis

Vermeesch

et al. 2018

Sedimentary Geology

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“…In warm and moist climate it is prone to weather into kaolinite, montmorillonite, mixed-layer minerals and other clay minerals. Mica, quartz and feldspar paragenetic assemblage indicates the high debris input in arid climate (Garzanti et al, 2014) . Esquevin (1969) proposed a Chemical Index (CI) to measure the intensity of weathering, which shows the weathering degree of the parent rocks and reveals the climate change of the provenance (Ehrmann, 1998;Kong et al, 2011;Liu et al, 2007).…”

Section: Muscovitementioning

confidence: 99%

The Environment Significance of Aerinite — First Discovered in the UBC Cliffs

Wang

2020

Acta Geologica Sinica (Eng)

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To analyze the composition and structure of the pale blue outcrop from the UBC Cliffs and research the environmental significance of aerinite recorded in the sediments, mineral composition, bulk chemical composition and structural analyses were carried out by means of X‐ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), electron microprobe analysis (EMPA) and X‐ray fluorescence spectra (XRF). Quartz, feldspar, mica, chlorite and aerinite as well as a small amount of amphibole, calcite, clinopyroxene, rutile, perovskite and apatite are recorded in the sediments. It is reported for the first time that the aerinite occurs in a high latitude area and in sediments paragenetic with mica and chlorite. The large span in grain size shows a typical characteristic of fluvioglacial sediments. Geochemistry characteristics (CIA, CIW, PIA, WIP and ICV) verify that there is virtually no chemical weathering. Mineralogy and geochemistry features of the UBC Cliffs sediments indicate that aerinite is accommodate to the high latitude and cold, dry climate. As the sediments show high similarity to those of their provenance, they have great significance in the identification of the forming condition and origin of the aerinite.

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“…The study of African sediments has shown that α Al Na is the chemical index most sensitive to weathering, largely because of the high emigration rate of Na + from plagioclase under active leaching ( [132][133][134][135]). The use of α Al Na-and in general of α Al E indices instead of α Sm Na, α Ti Ca, α Th K, α Nd Sr, and α Th Ba indices-avoids undesired perturbations up to even more than one order of magnitude associated with the locally strong hydraulic concentration or depletion of heavy minerals preferentially hosting Ti or REE (Table 1), and is thus recommended.…”

Section: The Meaning Of Chemical Indicesmentioning

confidence: 99%

Provenance of Bengal Shelf Sediments: 2. Petrology and Geochemistry of Sand

et al. 2019

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The Bangladesh lowlands are traversed by the largest sediment flux on the planet. Detritus generated mostly in Himalayan highlands and conveyed through the Ganga–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–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–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–mineral assemblages, showed a clear prevalence in sediment supply from the Brahmaputra (60–70%) over the Ganga (30–40%). 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.

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Provenance versus weathering control on the composition of tropical river mud (southern Africa)

Cited by 207 publications

References 75 publications

Dynamic uplift, recycling, and climate control on the petrology of passive-margin sand (Angola)

Dynamic uplift, recycling, and climate control on the petrology of passive-margin sand (Angola)

The Environment Significance of Aerinite — First Discovered in the UBC Cliffs

Provenance of Bengal Shelf Sediments: 2. Petrology and Geochemistry of Sand

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