Paleoweathering and Detrital Provenance of Balangbaru Shale, in South Sulawesi

Abstract

Sulawesi Island, known for its geological complexity, offers a unique opportunity for researchers to investigate further into sedimentary basins particularly in South Sulawesi area. The Cretaceous Balangbaru Shale is one of the rocks that has an extensive distribution in South Sulawesi especially in the western part. Due to limitation of geological information related to this formation we performed the paleodepositional investigation to elucidate the paleoweathering, geochemistry characterization, and detrital provenance of the Balangbaru Shale. Indeed, previous studies have demonstrated that fine-grained sedimentary rocks can serve as valuable archives of geochemical information, enabling the reconstruction of paleoclimate evolution during the deposition period. Employing XRF quantitative analysis, we examine the dispersion of major elements within eight distinct layers of the Shale. Additionally, comprehensive whole-rock analyses enable us to ascertain the abundance of major elements and subsequently deduce detrital SiO2 and biogenic SiO2 content, thereby comprehending the inorganic geochemical composition of the Balangbaru Shale. The present study seeks to address the limited understanding of the geochemical properties of the Balangbaru Shale, specifically pertaining to paleoweathering intensity and detrital provenance. Acknowledging the scarcity of recent data available on the subject matter, this research aims to bridge the limitation data gap by conducting an in-depth investigation into the geochemical characteristics of the Balangbaru Shale by employing major oxides concentrations (SiO2, Al2O3, Fe2O3, K2O, P2O5, MgO, CaO, Na2O, MnO, TiO2, Cr2O3) and trace elements (Sr, Cu, Ba, Th, Ni, V, Th, U) into the equations such as C-value, chemical index alteration (CIA), plagioclase index of alteration (PIA), weathering index of parker (WIP) and ratio of Rb/Sr, U/Th, Sr/Cu, Sr/Ba. Furthermore, the major oxides ratio of Al2O3/TiO2 and TiO2/Zr were performed to specify the sediment provenance and the source-area rock compositions of the Balangbaru Shale. The obtained data reveals a moderate to high degree of weathering intensity in the detrital source environment of the Balangbaru Shale, suggesting warm to humid climate conditions in the source region. Additionally, the analysis of the detrital fraction indicates the possible origin of the Balangbaru Shale from felsic rocks. Overall, these findings contribute significantly to the understanding of paleoenvironmental conditions associated with the Balangbaru Shale, shedding light on its geological history.