http://www.cnr.it/ontology/cnr/individuo/prodotto/ID292021
Geochemistry of surface and subsurface waters in quartz-sandstones: Significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela) (Articolo in rivista)
- Type
- Label
- Geochemistry of surface and subsurface waters in quartz-sandstones: Significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela) (Articolo in rivista) (literal)
- Anno
- 2014-01-01T00:00:00+01:00 (literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
- 10.1016/j.jhydrol.2014.01.029 (literal)
- Alternative label
Marco Mecchia M, Francesco Sauro, Leonardo Piccini, Jo De Waele, Laura Sanna, Nicola Tisato, Jesus Lira, Freddy Vergara (2014)
Geochemistry of surface and subsurface waters in quartz-sandstones: Significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela)
in Journal of hydrology (Amst.); Elsevier B.V., Amsterdam (Belgio)
(literal)
- Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
- Marco Mecchia M, Francesco Sauro, Leonardo Piccini, Jo De Waele, Laura Sanna, Nicola Tisato, Jesus Lira, Freddy Vergara (literal)
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- http://www.scopus.com/inward/record.url?eid=2-s2.0-84893632044&partnerID=q2rCbXpz (literal)
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- Note
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- La Venta Geographic Explorations Association; Department of Biological, Geological and Environmental Sciences, Italian Institute of Speleology, Bologna University, Bologna, Italy; Department of Earth Sciences, Florence University, Florence, Italy; Institute of Biometeorology, National Research Council of Italy, Sassari, Italy; ETH Zurich, Geological Institute, Zurich, Switzerland; Istituto Nacional de Parques, Caracas, Venezuela Teraphosa Exploring Team, Puerto Ordaz, Venezuela (literal)
- Titolo
- Geochemistry of surface and subsurface waters in quartz-sandstones: Significance for the geomorphic evolution of tepui table mountains (Gran Sabana, Venezuela) (literal)
- Abstract
- In situ measurements of discharge, pH, electric conductivity (EC), temperature, and SiO2 content have been
carried out during five expeditions in the last 20 years on the summit plateaus, inside caves and along the
rivers of the surrounding lowlands of three tepui massifs in Venezuela (Auyan, Roraima, and Chimanta).
Additionally, detailed chemical analyses were performed on waters sampled in a newly discovered extensive
quartz-sandstone cave system on the Auyan Tepui. Rock samples of the quartz-sandstone bedrock
from different locations have been analysed to obtain their chemical composition with a wavelength dispersive
X-ray fluorescence spectrometer. These data show that the majority of silica present in surface and
subsurface water comes from dissolution of quartz and only in minor amount from hydrolysis of other silicate
minerals. Probably the presence of a hardened crust of iron hydroxides limits the dissolution of silica
on the top surface of tepuis. Dissolution in the subsurface, instead, is more significant and causes, in the
long term, the ''arenisation'' of the quartz-sandstone and its subsequent removal by mechanical erosion.
On the other hand, waters flowing on the arkosic rock outcropping on the lowland below the tepuis obtain
their high dissolved silica content mainly from hydrolysis of silicates.
The morphological evolution of these table mountains appears thus to be controlled mainly by the
underground weathering of the quartz-sandstone, with the opening of deep fractures (grietas) and the collapse
of large underground horizontal cave systems. Scarp retreat, instead, seems to be related to the
higher weathering rate of the more arkosic formations underlying the quartz-sandstones. (literal)
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