%0 Journal Article
%A Arribas Mocoroa, María Eugenia
%A Rodríguez López, Juan Pedro
%A Meléndez Hevia, Nieves
%A Soria de Miguel, Ana Rosa
%A De Boer, Poppe
%T Giant calcite concretions in aeolian dune sandstones; sedimentological andarchitectural controls on diagenetic heterogeneity, mid-Cretaceous IberianDesert System, Spain
%D 2012
%@ 0037-0738
%U https://hdl.handle.net/20.500.14352/42416
%X Aeolian dune sandstones of the Iberian erg system (Cretaceous, Spain) host giant calcite concretions that constituteheterogeneities of diagenetic origin within a potential aeolian reservoir. The giant calcite concretionsdeveloped in large-scale aeolian dune foresets, at the transition between aeolian dune toeset and damp interduneelements, and in medium-scale superimposed aeolian dune sets. The chemical composition of the giantconcretions is very homogeneous. They formed during early burial by lowMg-calcite precipitation frommeteoricpore waters. Carbonate componentswith yellow/orange luminescence form the nuclei of the poikilotopic calcitecement. These cements postdate earlier diagenetic features, characterized by earlymechanical compaction,Fe-oxide cements and clay rims around windblown quartz grains resulting from the redistribution of aeoliandust over the grain surfaces. The intergranular volume (IGV) in friable aeolian sandstone ranges from 7.3 to15.3%, whereas in cemented aeolian sandstone it is 18.6 to 25.3%. The giant-calcite concretions developed duringearly diagenesis under the influence of meteoric waters associated with the groundwater flow of the desertbasin, although local (e.g. activity of fluid flow through extensional faults) and/or other regional controls(e.g. variations of the phreatic level associated with a variable water influx to the erg system and varyingsea level) could have favoured the local development of giant-calcite concretions. The spatial distributionpattern of carbonate grains and the main bounding surfaces determined the spatial distribution of the concretions.In particular, the geometry of the giant calcite concretions is closely associated with main boundingaeolian surfaces. Thus, interdune, superimposition and reactivation surfaces exerted a control on the concretiongeometries ranging fromflat and tabular ones (e.g. bounded by interdunes) towedge-shaped concretions at thedune foresets (e.g. bounded by superimposition and reactivation surfaces) determining the spatial distribution ofthe heterogeneities of diagenetic origin in the aeolian reservoir.
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