%0 Journal Article
%A Riaza García, Asunción
%A Mediavilla López, Rosa María
%A Santisteban Navarro, Juan Ignacio
%T Mapping geological stages of climate-dependent iron and clayweathering alteration on lithologically uniform sedimentary units usingThematic Mapper imagery (Tertiary Duero Basin, Spain)
%D 2000
%@ 0143-1161
%U https://hdl.handle.net/20.500.14352/57037
%X Weathering processes are responsible for slight surface mineralogicaldifferences allowing the distinction between lithologically similar geological unitsusing Thematic Mapper (TM) data. Two different stages throughout time ofoverlying iron alteration are notoriously distinctive on the imagery and laboratoryspectra. Their diverse spectral behaviour follows the dominant iron hydroxidewith kaolinite and carbonate crusts on the Pliocene Ochre Alteration typical ofa humid warm climate, compared with the dominant nonhydratated iron oxideswith smectite on the Miocene Red Alteration developed under a mediterraneandry climate. Iron materials with carbonate hinder appearance of the typical ironabsorption features in the visible wavebands. Therefore, the iron weatheringalteration coatings will be obscured on the imagery when it is developed oncarbonate sediments or detritic sediments with carbonate cement or matrix. Thepresence of carbonate within the sediment as cement or alteration productdecreases the overall reflectance of laboratory nonconsolidated rocks and the claysize fraction from rocks, apart from smoothing the 2200 nm absorption typical ofOH-bearing minerals. The presence of carbonate cement and carbonate crustsfavours the differentiation of some units. Digital mapping through image processingof different series of digital data leads to a sequential masking of classesto produce a final map. The sequence of masking produces different maps whichcan be used as a tool to model aspects of the sedimentary basin and geologicalprocesses throughout time.
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