Geochemistry of surface and subsurface waters in quartz-sandstones: significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela)

Mecchia, Marco; Sauro, Francesco; Piccini, Leonardo; Waele, Jo Hilaire Agnes De; Sanna, Laura; Tisato, Nicola; Lira, J.; Vergara, Freddy

doi:10.1016/j.jhydrol.2014.01.029

Cited by 40 publications

(32 citation statements)

References 38 publications

(54 reference statements)

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“…The ∼20–30 Ma old Imawarì Yeuta cave, discovered in the Auyan Tepui (Fig. 1a–c ), is among the less accessible and most pristine places on Earth representing the longest 12 , 13 , and probably oldest, known cave system in quartz-rich lithologies. A heated scientific debate on the genesis of the cave has arisen 14 , 15 , since the extremely low solubility and dissolution rates of quartz would not allow the formation of such giant underground voids in geological times as in well-known carbonate karst terrains.…”

Section: Introductionmentioning

confidence: 99%

Microbial diversity and biosignatures of amorphous silica deposits in orthoquartzite caves

Sauro

Cappelletti

Ghezzi

et al. 2018

Sci Rep

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Chemical mobility of crystalline and amorphous SiO2 plays a fundamental role in several geochemical and biological processes, with silicate minerals being the most abundant components of the Earth’s crust. Although the oldest evidences of life on Earth are fossilized in microcrystalline silica deposits, little is known about the functional role that bacteria can exert on silica mobility at non-thermal and neutral pH conditions. Here, a microbial influence on silica mobilization event occurring in the Earth’s largest orthoquartzite cave is described. Transition from the pristine orthoquartzite to amorphous silica opaline precipitates in the form of stromatolite-like structures is documented through mineralogical, microscopic and geochemical analyses showing an increase of metals and other bioessential elements accompanied by permineralized bacterial cells and ultrastructures. Illumina sequencing of the 16S rRNA gene describes the bacterial diversity characterizing the consecutive amorphization steps to provide clues on the biogeochemical factors playing a role in the silica solubilization and precipitation processes. These results show that both quartz weathering and silica mobility are affected by chemotrophic bacterial communities, providing insights for the understanding of the silica cycle in the subsurface.

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Section: Introductionmentioning

confidence: 99%

Microbial diversity and biosignatures of amorphous silica deposits in orthoquartzite caves

Sauro

Cappelletti

Ghezzi

et al. 2018

Sci Rep

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“…Micas and clay minerals can also be important players in the dissolution of quartz in sandstone (Bjørkum et al 1996;Meyer et al 2006). Laterisation processes due to alteration of micas, feldspar and clay minerals may account for considerable generation of porosity (Corrêa Neto 2000;Aubrecht et al 2011) and favour arenisation along or around specific beds (Mecchia et al 2014). Iron can also be significantly mobilised through various pro-cesses involving microbiological agents, contributing to porosity generation (Chalcraft & Pye 1984;Striebel & Schaferjohann 1997;Barton 2013;.…”

Section: Discussionmentioning

confidence: 99%

“…Although studies have been performed since the early 1960s (white et al 1966), systematic research on this topic is rather recent, with new information being produced every year. A significant FABIANA P. FABRI, AUGUSTO S. AULER, ALLAN S. CALUx, ROBERTO CASSIMIRO & CRISTINA H. R. R. AUGUSTIN portion of new data comes from the tepui area of southern Venezuela, where the longest and largest quartzite caves in the world have recently been discovered (Aubrecht et al 2013;Mecchia et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…The existence of dissolution processes is demonstrated by the frequent occurrence of silica speleothems, mostly coralloids (wray 2007Aubrecht et al 2008), with opal being the dominant mineral. Hydrochemical studies (e.g., Piccini & Mecchia 2009;Mecchia et al 2014) have supported a quantitatively restricted role of dissolution, with low SiO 2 content in most quartzite cave waters. However, given the long term geomorphic evolution of the area, even low levels of silica can be relevant to arenisation.…”

Section: Introductionmentioning

confidence: 99%

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Cave morphology and controls on speleogenesis in quartzite: The example of the Itambé do Mato Dentro area in southeastern Brazil

Fabri

Auler

Calux

et al. 2015

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Dentro v jogovzhodni Braziliji V članku opisujemo rezultate podrobnega kartiranja krasa v kvarcitu na 417 km 2 velikem območju v jugovzodni Braziliji. Z izjemo stolpov in udornic na območju ni površinskih kraških oblik, značilnih za karbonatni kras. Jame so najbolj značilen kraški pojav, čeprav je njihova gostota precej manjša od tiste na karbonatnem krasu. Na celotnem območju smo izmerili in detaljno raziskali 11 jam, ki so razvite plitvo in vzporedno s površjem. Glavna dejavnika razvoja jam sta litologija in hidravlični gradient. Petrografske analize kažejo, da je razvoj jam najbolj aktiven v območjih plitve freatične cone, kjer se v kvarcitu pojavljajo leče sljude (sericit) ter kjer sericit in železo obdajata kremenčeva zrna. V the območjih prihaja do razpadanja in mehanskega odnašanja zrn. V jugovzhodni Braziliji so kvarcitne jame pogost pojav, vendar so med seboj pravilpoma nepovezane, kar kaže na to, da v primerjavi s karbonatnim krasom v kvarcitu ne prihaja do razvoja velikih povezanih kraških drenažnih sistemov.

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“…The observation of large, abundant scarps in the remnants of sedimentary cover suggests that scarp retreat may have been an important process in generating the modern topography of the Shillong Plateau. Indeed, scarp retreat has been identified as a fundamental process of landscape evolution in many landscapes where significant thicknesses of sub horizontal, well-stratified sediments are being eroded, for example: in the Colorado Plateau in the southwest USA (e.g., Schmidt, 1989); in the hapada do Araripe plateau in Northern Brazil (de Carvalho Júnior, 2015; Peulvast and Bétard, 2015); in the Tepui landscape of the Gran Sabana in Venezuela (Piccini and Mecchia, 2009;Mecchia et al, 2014). Karstic cave formation and subsequent collapse has been shown to be an important mechanism for generating the scarp-bound Tepui plateaus in Venezuela (Wray, 2009;Mecchia et al, 2014).…”

Section: Stripping Mechanisms In the Southern Shillong Plateaumentioning

confidence: 99%

Lithological control on the geomorphic evolution of the Shillong Plateau in Northeast India

et al. 2019

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The Shillong Plateau in Northeast India is a block of raised topography in the Himalayan foreland which consists of crystalline basement rocks partially covered by a Cretaceous to Miocene sedimentary succession. It is dominated by a mature, low relief landscape surrounded by high relief, fluvially dissected margins, particularly along its southern flank which is bounded by the Dauki thrust Fault. We use river profiles and geological relationships to show that the low relief plateau is a topographic expression of a re-exposed basement palaeosurface following the stripping of sedimentary cover by scarp retreat. We show that initiation of the wave of incision does not require surface rupture on the Dauki Fault or an increase in fault slip rate at the end of the Miocene, as suggested by previous studies. We propose that incision has been spatially controlled by the slope of the basement palaeosurface, likely moderated by an incision threshold. River profiles in the Shillong Plateau cannot be interpreted as simple records of surface uplift. The observed heterogeneous spatial pattern of steepness is a function of a dynamic landscape response to the erosion of layered lithology with contrasting erodibility. Such dynamics have *Revised manuscript with no changes marked Click here to view linked References implications for fluvial geomorphology, highlighting that near-horizontal lithological contacts can strongly influence river profiles and topography, even when no longer physically preserved. The topography of the northern Shillong Plateau is controlled by the structure of basement rocks and is reminiscent of stable cratonic interior landscapes, consistent with its surface exposure during late Cretaceous times.

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Geochemistry of surface and subsurface waters in quartz-sandstones: significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela)

Cited by 40 publications

References 38 publications

Microbial diversity and biosignatures of amorphous silica deposits in orthoquartzite caves

Microbial diversity and biosignatures of amorphous silica deposits in orthoquartzite caves

Cave morphology and controls on speleogenesis in quartzite: The example of the Itambé do Mato Dentro area in southeastern Brazil

Lithological control on the geomorphic evolution of the Shillong Plateau in Northeast India

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