Sequence stratigraphy and carbon isotope stratigraphy of an Aptian mixed carbonate-siliciclastic platform to basin transition (Galve sub-basin, NE Spain).
Résumé
A 380 m thick Aptian platform to basin transition has been studied along a 16 km long transect of excellent and continuous outcrops in NE Spain. The series has been dated using biostratigraphy (foraminifera and ammonites) and carbon-isotope stratigraphy, and has been subdivided at four scales of depositional sequences. The Aptian marine succession is subdivided into two-large scale sequences separated by a middle Aptian sub-aerial exposure surface. A characteristic trend of the floral-faunal fossil assemblages is present, which evolves from orbitolinid-ooid dominated ramps in Sequence I-1, to a coral-stromatoporoid-microbialite dominated platform in Sequence I-2, to a rudist-dominated platform top in Sequence II-1, and finally to a second episode of orbitolinid-ooid dominated ramp system in Sequence II-2. There was an influx of siliciclastic sediments at the base and at the top of this succession. The detailed carbon-isotope curve measured along the Miravete section and covering almost the complete Aptian succession, is compared with published Aptian curves recorded in both basinal and carbonate platform settings along the northern and southern NeoTethys margins. It shows that the Galve sub-basin curve represents all the major isotope excursions of the lower and upper Aptian, in a dominantly shallow-water succession.