The marine fossils and paleoecological significance of the Southern edge of South Sumatra Basin in Linggapura Lampung, Indonesia

Abstract

The South Sumatra Basin is identified as a Paleogene-Neogene sedimentary basin with Mesozoic basements. It is located in the eastern Barisan Mountains, covering Jambi, South Sumatra, and Linggapura (Lampung), Indonesia. Linggapura represents the southernmost part of the South Sumatra Basin. The basin consists of two well-known rock formations, namely the Talangakar and Baturaja Formations. In this study, we investigated these formations through fossil records and paleoecological interpretations. Our investigation was based on measured stratigraphy and fossil observations along the Way Penandingan River in Linggapura, Lampung. We discovered that the bottom of this area consists of Cretaceous granitoid, which forms a nonconformity with the sedimentary rocks in this area. The Talangakar Formation in this region comprises quartzy-grained sandstone and conglomerates containing fossilized remains of terrestrial plants/vegetation. These plant fossils have undergone coalification, with some being silicified. The Batujara Formation in Linggapura is dominated by bioclasts, primarily consisting of Miocene shoreface-lagoonal larger benthic foraminifera, along with other marine and ichnofossils. Based on our findings, we suggest that the paleoecological condition of this area is associated with shoreline transgression during the Oligo-Miocene period. The hotter Miocene climate contributed to a rise in sea levels, resulting in shoreline transgression. Gradually, the area transformed from a terrestrial environment to a highly bioproductive marine environment, at least from the Late Oligocene to the Early Miocene. This study represents an important milestone in better understanding the paleoenvironmental conditions at the edge of the South Sumatra Basin throughout its geological history.