Considering Ngalau Sirantai Cave as the Historic Sibrambang Site: New Speleological and Chronological Evidence

Benyamin Perwira Shidqi1,3*, Gilbert J. Price2, Agus T. Hascaryo3, Sebastian F.M. Breitenbach4, Mathieu Duval1,5, Yan Rizal3, Aswan3, Mika R. Puspaningrum3, Jananda Indriyanto3, and Julien Louys1

The Padang Highlands host numerous Pleistocene fossiliferous cave sites that have contributed substantially to palaeoecological studies in Sumatra and the broader Southeast Asian region. Among these, Sibrambang is one of the most productive, yielding over 3,400 fossil specimens since its discovery by Eugène Dubois in 1890. Despite its major contribution to palaeoenvironmental and palaeobiogeographic research, the precise location of the original site has remained unknown. Here, we report a previously undocumented cave site, Ngalau Sirantai, located in the Sibrambang area of the Padang Highlands, and present new sedimentological and geochronological data to reconstruct its speleological history and associated clastic and fossil deposits. Ngalau Sirantai also presents an opportunity to test the hypothesis that it corresponds to Dubois’ historic Sibrambang site. Our data suggest that deposits were emplaced through combined gravitational and water-mediated processes, resulting in multiple episodes of breccia formation and fossil-rich cave floor sediment accumulation. Uranium-series dating suggests breccia deposition occurred during Marine Isotope Stages 5 to 3, providing minimum age constraints. Sediment scars observed along the chamber cave walls strongly indicate previous sediment removal activities. Based on its location, speleological characteristics, sedimentology, stratigraphy, palaeontology, and age constraints, when compared with historical records and recent geochronological studies, strongly support the interpretation of Ngalau Sirantai corresponds to the lost Sibrambang.