Biostratigraphic indices for Lower Jurassic carbonate-platform deposits (Perdido Group), Overthrust Terrane Association, Timor-Leste

Lower Jurassic carbonate-platform deposits in Timor-Leste have been subject to much controversy. The Perdido Group contains the Bahamian-type facies shallow-water limestone of the Lower Jurassic that had been mixed with an upper Oligocene-lowest Miocene carbonate unit in Audley-Charles's Cablac Limestone. Foraminiferal assemblages from five sites in the Perdido Group are used to confirm a Sinemurian-Pliensbachian age. Species recorded for the first time from Timor and from the broader region, are Biokovina sp., Bosniella oenensis Gu.sic, Endotriadella ifranensis Bassoullet, Boutakiout, Vachard, Lituosepta recoarensis Cati, Palaeocyclammina complanata Bassoullet, Boutakiout and Echarfaoui, Planisepta compressa (Hottinger), and Radoicicina ciarapicae Gale, Barattolo and Rettori. Previously Siphovalvulina spp. and Meandrovoluta asiagoensis Fugagnoli and Rettori were described from the group. These species allow distinction between the Perdido Group (part of the Overthrust Terrane Association in Timor-Leste) and the carbonate-platform Upper Triassic Bandeira Group (part of the East Gondwana Interior Rift Association). No equivalent facies coeval with the Perdido Group and with similar foraminiferal assemblages have been recognized in the Indonesian, Malayasian, Timor-Leste, or north-west Australian regions. The closest known Sinemurian-Pliensbachian occurrence containing some of the species found in the Perdido Group, is in Western Thailand, with a fauna including Lituosepta cf. recoarensis.

Automated summary

This study investigates the Lower Jurassic carbonate-platform deposits in Timor-Leste, confirming their age using foraminiferal assemblages and identifying new species in the region. The research distinguishes the Perdido Group from the Bandeira Group and highlights the lack of equivalent facies in other neighboring regions with similar foraminiferal assemblages.