Palaeobiogeographic and tectonic significance of mid-Cretaceous invertebrate taxa from Batavia Knoll, eastern Indian Ocean

Abstract

A newly described fossil suite from Batavia Knoll, eastern Indian Ocean, adds insight to the palaeobiogeographic connections between assemblages around the nascent Indian Ocean, during the breakup of Gondwana in the mid-Cretaceous (Albian and Cenomanian). Analyses were completed on the biotic similitude of the Batavia Knoll and five other suites from around the Indian Ocean, being northern Australia, central and southern Indian, Madagascar, and south-eastern Africa. Employing Jaccard coefficients (J) to determine degrees of similarity between the suites, it was determined that the Batavia Knoll invertebrate assemblage maintains strong connections to the others included in the study (J > 0.18), with the exception of the central Indian assemblages (J = 0.091). This pattern was followed by most of the other suites, cementing Batavia Knoll's palaeobiogeographic position within the East African Palaeobiogeographic Province. The results of the analysis also extended the eastern boundary of that province to include the northern coast of Australia, with fauna there exhibiting similar strong affinities with other circum-Indian suites.