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| Autore principale: | |
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| Natura: | Artículo científico |
| Lingua: | en |
| Pubblicazione: |
Universitat de Barcelona
2007
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| Accesso online: | https://www.redalyc.org/articulo.oa?id=50550204 |
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Sommario:
- Controlling factors on clay mineral assemblages: insights from facies analysis of Pliocene to Pleistocene coastal margin deposits, Western Portugal P. Dinis A.F. Soares Ciencias de la Tierra Facies Provenance Clay minerals Paleogeography The clay fractions in the Pliocene to Pleistocene coastal margin record are usually dominated by kaolinite andillite, with lesser amounts of vermiculite, 10-14 mixed layer clays and smectite. The high clay mineral crystallinity,the mineralogical relations to facies and depositional setting and some horizontal variations alongcoeval deposits suggest that clay assemblages are mainly detrital. Illite is more important in inner shelf depositsand particularly in alluvial deposits from eastern locations. The high illite content in eastern alluvial deposits isexplained by the input from the neighbouring Iberian Variscan Massif that is rich in mica. The high kaolinitecontent in prograding sand and gravel coastal plain is partially explained by the availability of this mineral inthe drainage areas. Given the arkosic nature of some of these deposits, post-depositional feldspars weatheringwould also contribute to an increase in kaolinite content. Vermiculite is particularly important close to the surfaceand to unconformities, in horizons influenced by pedogenetic processes that have more aluminous illitewith relatively low crystallinity. In organic rich mud sediments low pH conditions favour post-depositionaltransformation of illite to vermiculite and mixed layer clays. 2007 artículo científico 1695-6133 https://www.redalyc.org/articulo.oa?id=50550204 en http://www.redalyc.org/revista.oa?id=505 Geologica Acta: an international earth science journal application/pdf Universitat de Barcelona Geologica Acta: an international earth science journal (España) Num.2 Vol.5