title: Taphonomy and site formation history of vertebrate-bearing breccia in the caves of Sumatra
Creators: name: Smith, Holly E
Publisher: name: Griffith University
Year: 2021
Subjects: subject: Taxonomy
subject: Taphonomy
subject: Cave
subject: Pleistocene
subject: Southeast Asia
subject: Hexaprotodon
subject: ESR and U-series dating

description: Breccia is a calcareous clastic deposit that has recently emerged as a source of taphonomic information in the caves of Southeast Asia. Fossil remains are often cemented in the deposits, preserving evidence of a rich and interesting palaeohistory in the region. Previous research notes that taphonomic reconstruction of fossil assemblages in dynamic settings like the tropical caves of Southeast Asia is crucial for the temporal reconstruction of palaeoenvironment and regional chronostratigraphies. Direct dating of incorporated fossil remains persists as the convention in determining the mechanisms of vertebrate accumulation. However, the complex infilling and depositional history of the fossiliferous breccia deposits make it difficult to ascertain the provenance of the faunal remains within and the taphonomic factors that influence them. A contextual approach is crucial to reconstructing the complex taphonomic history of Southeast Asian cave fossils, the depositional history of the breccia in which they are cemented and the diagenesis of the sediments in which they are held. In this thesis, a multimethod model is employed for establishing the dominant factors responsible for the accumulation and preservation of the vertebrate remains in karstic breccia from Sumatran caves. To achieve this, a digital imaging survey is combined with a micro-contextual study to reveal the internal composition of consolidated breccia deposits without the need for destructive preparation. The geological context of the breccia deposits and spatial distribution data of the remains within are analysed. A novel holistic approach is developed for reconstructing the taphonomic history of Southeast Asian cave fossil assemblages in future data collection studies. Through the course of this research, it is demonstrated that i) the mechanisms of vertebrate-bearing breccia deposition in Sumatran caves are significantly understudied ii) breccia deposits have potential for establishing the dominant factors responsible for the accumulation and preservation of Sumatran cave vertebrate remains iii) a wealth of unexploited taphonomic data can reveal the agents that shape the regions cave fossil assemblages and add new taxa to the Sumatran fossil record iv) the post- depositional taphonomic agents that shape Southeast Asian cave fossil assemblages are directly linked to the various processes of formation during cave infilling and so the sedimentary context of the fossil-bearing breccia must be considered during analysis. This thesis reveals the internal composition of fossiliferous cave deposits in Southeast Asia and the taphonomic events that transpired at each cave site. A literature review demonstrates there is limited research addressing the taphonomic and depositional histories of faunal skeletal assemblages in tropical Southeast Asia. The study also indicates that conventional direct dating methods are susceptible to significant risk of time- or habitat-averaging due to natural ‘mixing’ processes of remains in complex tropical cave environments (Chapter 2). Therefore, the first taxonomic and taphonomic description of vertebrate fossils from Ngalau Gupin cave in the Padang Highlands of Sumatra, Indonesia is undertaken. This is a newly discovered site that provides us with a unique opportunity to examine the taphonomic pathways fossils can take in a tropical cave setting. This survey not only assesses the taphonomic agents that shaped the Ngalau Gupin faunal assemblage but explores the limitations of dating vertebrate remains in this complex cave environment (Chapter 3). These studies propose that future research may benefit from three-dimensional analyses of spatial distribution data to assess the spatial location and temporal sequence of sediment layers, and inclusions within the breccia laid down during formation. A digital survey proves this hypothesis to be correct as thermal neutron imaging of the breccia reveals the primary agents in the formation and concentration of incorporated vertebrate remains in the caves of Southeast Asia (Chapter 4). The potential in using a multi-scale multi-method approach is proven as micromorphological analysis reveals further evidence of a complex suite of taphonomic agents, post-depositional alterations and diagenetic trends that have modified the fossil assemblages in the caves of Sumatra, including carnivore occupation, water action and calcite precipitation (Chapter 5). This research lays the groundwork for even greater development in the future. Further expansion of the techniques developed in this thesis, ones that include analyses of spatial distribution data and micro-context, would facilitate research into reconstructing infilling and sedimentary histories of breccia deposits. Thus, future research has the potential to build on the studies presented here to resolve mechanisms of site formation, depositional history, and faunal accumulation in tropical environments; evidence of value in establishing stratigraphic provenance and temporal positions of fossil-bearing deposits in complex depositional environments across Southeast Asia.