Resumen de La aplicación de la estratigrafía secuencial en el análisis de una cuenca extensional pirenaica: la cuenca de Organyá.
Josep-María Bernaus, Esmeralda Caus Gracia, Annie Arnaud Vanneau
Sequence stratigraphic concepts are applied to an extensional basin filled with more than 1000 m of carbonate platform sediments (Urgonian facies) deposited during a period (Barremian-Lower Aptian) when the basin subsided very quickly. Four depositional sequences (OR-1 to OR-4) have been recognised, separated by sequence boundary type 1 (Sb-C and Sb-F) or type 2 (Sb-D and SbE). Fhe age of the sequence boundaries is upper Barremian (Sb-C and Sb-D), close to the Barremian/ Aptian boundary (Sb-E) and lower Aptian (Sb-F), respectively. Fhe last sequence boundary corresponds to the demise and drowning of the carbonate platform. High subsidence rates characterised this basin and were responsible for I) the very thick depositional sequences and gradual changes in facies, 2) the occurrence of type 2 sequence boundaries during a period when eustatic sea-level fall matched the subsidence rate, 3) the occurrence of lowstand system tracts (LST), consisting of brackish/t'resh-water carbonates (charophyte limestone), and 4) a temporary anoxic episode at the base of the early Aptian. However, the main global eustatic changes recognised on the northern margin ofTethys were also identified here, in spite ot the strong tectonic control on deposition.
