Mineralogía de arcillas y diagénesis en la sección tipo de la formación de Gordexola (Albiense inferior a medio, flanco sur del anticlinorio de Bilbao)
- María Cruz Zuluaga Ibargallartu
- José Javier Arostegi García
- Francisco García Garmilla
- Francisco Velasco
ISSN: 0210-6558
Year of publication: 1992
Volume: 15
Issue: 0
Pages: 113-122
Type: Article
More publications in: Boletín de la Sociedad Española de Mineralogía
Abstract
The Gordexola Formation (Gordexola Fm), maximum thickness 2400 m in the typesection, lower to middle Albian, widely outcrops at the south limb of the Bilbao anticlinorium whose structural trend is NW-SE. The bulk rock, the < 2 pm and the 2-20 pm fractions of 165 samples of pelitic rocks were analised by X-Ray Diffraction method. The bulk mineralogy is very homogeneous, with clay minerals and quartz as major phases (both constitute 75% as an average). The 3). The Kübler’s index has been measured and the values obtained for the finer fraction are considerabely higher: 1.5°20 and O.65°20 as an average for the < 2 pm and 2-20 pm fractions, respectively. The illite/semectite mixed layer distribution observed in both fractions and the Kiibler’s index values permits to atribute the Gordexola Fm. to the middle diagenesis zone. In the general scheme of the continuous evolution of the diagenesis in the south limb of the Bilbao anticlinorium, the Gordexola Fm. presents a delay in the diagenetic evolution.