Resumen de Los minerales de la arcilla en los ambientes deposicionales de la Fm/ Escucha (Albiense Medio, Sistema Ibérico).
Feliciano Plana, Ignasi Queralt Mitjans, José Luis Fernández Turiel, Teófilo Sanfeliu Montolío
The Escucha Fm. (middle Albian, Iberian Range, NE Spain) consists of alternating coal bering ans fine siliciclastic depisots up to 550 m thick. Durnig Albian times fluvio-deltaic, swamp and marine environments prevailed in this area. Paleoenvironmental modelization were realized from sedimentology data in an earlier study (Querol, 1990) and allow us to distinguish five depositional zones (a/fluvio-deltaic plain, b/ peat bog flat, c/ brackish water swamp belt, d/ delta front, e/ prodelta) in order to recognize different mineral assemblages. Mineralogical analysis in the whole rock and the clay fraction from 49 sample of sediments interbedded in coal sequences were performed by X-Ray diffraction means. A semiquantitativew estimation of mineral contents in the whole rock and of the clay mineral in fine fraction was obtained follwing the criterion of Chung (1974) and Inglés & Anadón (1991). The mineral assamblages in the rocks studied are formed mainly by quartz and kaolinite. Substantial amounts of illite and mixed layer illete/smectite are present, and it is also possible occasionally to identity feldespars, calcite, gypsum, jarosite, hematite and pyrite. There is no correlation betwenn the mineral features od assembalges and the location of the samples in the vertical profiles. The obtained results show a relationship between mineral distribution and the different depositional zones. In this sense, it can be regarded that the amount of the mixed layer illite/smectite- increases to the prodelta sediments-, the ranges of quartz distribution illite crystallinity spreading to the fluvio-deltaic deposits and the kaolinite/illite ratio lower in prodeltaic environment are reflecting the changes in the physico-chemical conditions of deposition.
