U-series dating and geochemical analysis of speleothems: Developing a robust chronological tool for cave deposits and assessing Late Holocene human-environment interactions in western Flores, Indonesia.

St Pierre, Emma J. (2011). U-series dating and geochemical analysis of speleothems: Developing a robust chronological tool for cave deposits and assessing Late Holocene human-environment interactions in western Flores, Indonesia. PhD Thesis, School of Earth Sciences, The University of Queensland.

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Author St Pierre, Emma J.
Thesis Title U-series dating and geochemical analysis of speleothems: Developing a robust chronological tool for cave deposits and assessing Late Holocene human-environment interactions in western Flores, Indonesia.
School, Centre or Institute School of Earth Sciences
Institution The University of Queensland
Publication date 2011-12
Thesis type PhD Thesis
Total pages 298
Total colour pages 80
Total black and white pages 218
Language eng
Subjects 210102 Archaeological Science
040605 Palaeoclimatology
040303 Geochronology
Abstract/Summary Due to the environmental challenges we currently face as a global community, understanding the trajectories of climate and environmental change is critical. There is an increasing emphasis in the literature on historic and prehistoric anthropogenic environmental impacts and the role climate change has played on the evolution, dispersal, adaptation and cultural development of hominin. However, the links between climate and environmental change and human response are frequently no more than speculative arguments and will remain so until fundamental problems in our methodologies are addressed. The most pressing of these problems is the need to establish reliable and robust chronologies for palaeoenvironmental and archaeological records. This thesis has two main objectives 1) develop a means of reliably and precisely dating archaeological and palaeontological deposits beyond the limits of the C14 dating method; and 2) Assess human-environment interactions during the Late Holocene through the integration of precisely dated archaeological, palaeontological and palaeoenvironmental records from limestone caves sites in western Flores, Indonesia. Limestone caves are excellent repositories for palaeoenvironmental and archaeological information. Speleothems (secondary cave carbonates such as stalagmites and stalactites) in particular can act as reliable archives of climate and vegetation change and can be precisely dated with high precision U/Th dating techniques. Here we develop a means of dating archaeological and palaeontological sites in limestone caves through the application of the U/Th dating method to an under-utilised sample type – soda straw stalactites (Chapters 2 and 3). We demonstrate that U/Th dating of soda straw stalactites from excavated deposits can be used to constrain a maximum age of deposits and may represent the actual age of deposition. As U/Th dating can date speleothem material back to 500 ka, the method can be used to refine chronologies for extremely old sites. U/Th dating of soda straw stalactites is applied to samples in excavated deposits from the sub-chamber of Liang Bua, Flores, Indonesia (Chapter 4). As the discovery site of a new species of hominin, Homo floresiensis, and with detailed evidence for modern human occupation, Liang Bua is one of the most important sites for our understanding of hominin evolution, dispersal and culture change in Island Southeast Asian (ISEA). The paper provides a chronological and geomorphological context for future excavations of the sub-chamber and demonstrates that the site was never used as an occupation area but acted as a sink for Pleistocene aged archaeological and faunal material from Liang Bua main chamber. Following the development and application of the soda straw stalactite dating technique, we go on to assess human-environment interactions in Flores, Indonesia. A high resolution record of climate change over the past 1800 years BP is developed through U/Th dating, C/O stable isotope and trace element analysis of a stalagmite from Liang Luar cave (<1km from Liang Bua) (Chapter 5). The climate record demonstrates little variability in precipitation and vegetation cover in the area during the penultimate millennium followed by large fluctuations in the last millennium, especially during the Medieval Warm Period (MWP, 1050-700 BP) and the Little Ice Age (LIA, 400-100 BP). Comparison of the Flores speleothem records with those from the East Asian Monsoon (EAM) regime in the Northern Hemisphere (NH) reveals a remarkable anti-phasing relationship between the EAM in the NH and the Australasian Monsoon in the Southern Hemisphere (SH), which appears to be related to the insolation-driven latitudinal migration of the Inter-tropical Convergence Zone (ITCZ). On the other hand, centennial trends and multi-decadal oscillations displayed in Flores δ18O record and reconstructed SST in the Makassar Strait prior to ca. 700-800 years BP also suggest that the Pacific Decadal Oscillation (PDO), the El Nino Southern Oscillation (ENSO) and the associated longitudinal Pacific Walker Circulation also played a significant role in modulating climate in the Western Pacific. The large latitudinal or cross-hemispheric variability in monsoonal strengths centring around the MWP and the LIA especially in the tropical and sub-tropical regions poses a serious challenge to the reliability of recent global mean temperature reconstructions and models for the last two millennia, which are strongly biased toward mid- to high-latitude NH. An assemblage of small vertebrates from owl pellet deposits excavated within the same cave system and dated to 2400 BP with charcoal 14C (Chapter 6), is also examined to reconstruct environmental change in the area. The faunal record reveals two main periods of impacts with the reduction in endemic forest species around 1200 BP and the introduction of exotic irrigated rice communities in recent times. The Late Holocene palaeoenvironmental records from Liang Luar provide a climatic setting for human occupation of the area and act as indicators of human induced impacts on the local environment through changing land use patterns. The development of precisely dated, high resolution palaeoenvironmental records, in close association with archaeological evidence in western Flores, Indonesia, provides a unique opportunity to understand human-environment interactions and changing land use patterns during the Late Holocene in this critical region for human dispersal and cultural development.
Keyword archaeology
Flores, Indonesia
human-environment interactions
limestone caves
Naracoorte, South Australia
U/Th dating
Additional Notes Colour pages: 19, 39, 43, 47, 49, 51-52, 60, 65, 69-70, 72, 75-77, 86, 90, 94, 110, 117-118, 125, 127, 134, 164, 170-171, 175, 178-179, 181, 192, 201-202, 210-246, 248, 251, 253, 254, 257-259, 268, 297-298 Landscape pages: 50, 67-68, 73-74, 90, 97-9100, 122, 125, 174-175, 178, 256, 290, 297

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