Diversity patterns of Early Jurassic brachiopod assemblages from the westernmost Tethys (Eastern Subbetic)
Abstract A detailed faunal succession based upon 6400 brachiopods from the Early Jurassic in the Eastern External Subbetic palaeogeographical domain (Betic Range, Spain) is characterized and analyzed. This study allows recognition of five assemblages with original biostratigraphical data in sediments where biostratigraphical markers were very scarce. It also enables a sound diversity dynamics pattern to be established among the brachiopod assemblages recorded. This pattern shows progressive diversification from the Sinemurian to the Late Pliensbachian, although with significant episodes. During the Sinemurian–Pliensbachian transition, the first initial pulses of the disintegration of the South Iberian palaeomargin played an important role in the brachiopod assemblages, as a notable faunal renewal event is detected (Assemblage 1 to Assemblage 2). Maximum biodiversity and abundance were reached in the Pliensbachian–Toarcian transition, due to the partial contemporaneity of Assemblages 2 and 3 and the settlement of taxa from nearby palaeogeographical basins. A decrease related to the Early Toarcian Anoxic Event (ETOAE) global effect is suggested, after which a slight recovery began, with colonization by opportunistic taxa (Soaresirhynchia bouchardi) but pre-ETOAE diversity and abundance were subsequently never again reached. A palaeogeographical analysis has been carried out to compare taxonomic diversity dynamics in the Eastern Subbetic with other representative Tethyan basins. This study also enables palaeobiogeographical affinities to be established for the Eastern Subbetic domain, showing Mediterranean palaeobioprovince influences until the Late Pliensbachian–Early Toarcian, a period when replacement occurred that shows faunal unification. Free connection between the Sub-boreal and Mediterranean provinces may be inferred from the Late Pliensbachian–Early Toarcian onwards.