Coalification history of the Stephanian Ciñera- Matallana pull- part basin, NW Spain: Combining anisotropy of vitrinite reflectance and thermal modelling

Journal article
(Original article)


Publication Details

Author(s): de Wall H
Journal: International Journal of Earth Sciences
Publication year: 2004
Volume: 93
Journal issue: 93
Pages range: 92-106
ISSN: 1437-3254


Abstract


The Stephanian Cinera-Matallana Basin of NW Spain comprises 1,500 m of alluvial to lacustrine coal-bearing sediments, which were deposited in a late Variscan transtensional/transpressional pull-apart setting. The relationship between coalification pattern and rock deformation was evaluated by measurements of the anisotropy of vitrinite reflectance (AVR). The AVR ellipsoids reveal both pre-tectonic elements related to the bedding fabric and syn-tectonic elements related to folding, producing biaxial ellipsoid shapes with the maximum reflectance parallel to fold axes. The mean coalification gradient for the Stephanian succession is about 0.62 %Rr/km. Calculations of the mean palaeogeothermal gradient are presented on the basis of three different empirical equations. A palaeo-geothermal gradient of 85 degreesC/km is considered the most realistic, with an overburden of about 1,000 m. 1-D numerical modelling of the burial history results in two possible scenarios, the most preferable involving a palaeo-heat flow of 150 mW/ m 2 and an overburden of ca. 1,050 m. These results indicate that maximum coalification was related to a localised but high palaeo-heat flow/-geothermal gradient. The anisotropy of vitrinite reflectance highlights the interactive and transitional nature of sedimentary compaction and rock deformation on the maturation of organic material within strike-slip fault zones.



FAU Authors / FAU Editors

de Wall, Helga Prof. Dr.
Professur für Geologie unter besonderer Berücksichtigung der Strukturgeologie [Tektonik] und Photogeologie

Last updated on 2018-11-08 at 01:12