Publication: Detrital modes in sedimenticlastic sands from low-order streams in
the Iberian Range, Spain: the potential for sand generation by
different sedimentary rocks
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Publication Date
2003
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Elsevier
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Abstract
The composition of modern stream sands derived from sedimentary source rocks in the Iberian Range has been analyzed in
order to evaluate the contributions of the different bedrock types (mainly sandstones, limestones and dolostones). Temperate to
subhumid climate and short transport conditions promote a weathering-limited denudation regime. As expected, sand
composition proved to be essentially quartzolithic, with variable amounts of penecontemporaneous carbonates.
Sand compositional data were compared with the exposure areas of the different bedrocks in the drainage sub-basins
considered for semi-quantitative assessment of the sand generation potential of each bedrock type. Siliciclastic formations
(sandstones) appear to be by far the most significant sand producers, with Sand Generation Indices (SGIs) in the medium sand
fraction ranging from 4 to 20; i.e., 4 to 20 times greater than the SGI of carbonate rocks. Composition and texture are the main
factors controlling carbonate sand generation. Sparitic limestones yield higher SGIs (2.8 to 20) when source terrains are
constituted exclusively by carbonate rocks. High sparite grain content in the sands is enhanced by supplies from additional
sources, such as calcitized dolostones. Dolomicrite sources are strongly under-represented in the sands analyzed (very low SGI),
whereas the proportion of micritic limestone grains tends to be an accurate reflection of that bedrock at the source.
Even though the results presented here refer to the first stage of sand generation with negligible transport effects, we think
they may be helpful in the analysis and reconstruction of source terrains in ancient sedimenticlastic deposits