Early Jurassic benthic foraminiferal diversification and biozones in shallow-marine carbonates of western Tethys

Abstract

Low-latitude carbonate platforms dominated the southern and northern margins and microplates of western Tethys during the Early Jurassic. However, these have proved difficult to date in the past partly due to a lack of study but also a perception of low biotic diversity following the Triassic-Jurassic extinction event. Detailed logging and sampling of seven continuously exposed sections of Lower Jurassic shallow-marine carbonates in Gibraltar, Morocco, Tunisia, Greece, Italy, and in Spain reveals the occurrence of 12 benthic foraminifera species. These taxa are described and illustrated, and include: one new speciesTextulariopsis sinemurensis, new records for the Early Jurassic, and new records for this region. Five new biozones for the late Hettangian to early Pliensbachian time interval are erected from the consecutive appearance of benthic foraminifera within these sections, from top to base:Lituosepta compressa, Lituosepta recoarensis, Everticyclammina praevirguliana, Siphovalvulina colomi andSiphovalvulina gibraltarensis. This has enabled the correlation of these sections for the first time from the northern and southern Tethys margins and from the Apuleian and Pelagonian microplates within Tethys. The foraminiferal occurrences indicate a similarity of associations from the southern and northern shallow carbonate shelves of Tethys, whilst reflecting the relative isolation of the Apuleian and Pelagonian microplates within Tethys. The foraminifera show a progressive diversification of forms through the late Hettangian to early Pliensbachian interval that is interpreted to reflect the evolutionary recovery and diversification of these biotas following the Triassic-Jurassic extinction event.