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Type: Thesis
Title: Tectonic evolution and palaeogeography of Thailand
Author: Dew, Romana Elysium Carthew
Issue Date: 2019
School/Discipline: School of Physical Sciences
Abstract: The tectonic evolution and palaeogeography of Thailand requires refinement, especially the origin and nature of the basement, the relative position of the three main Thai terranes from their genesis to their amalgamation, the location of the terrane boundaries and the exact timing of the amalgamation of Thailand. This thesis endeavours to better unravel the tectonic evolution and palaeogeography of the three major Thai terranes: Indochina, Sukhothai and Sibumasu. But, it aims to do this by coupling disparate geological disciplines from palaeontology and sedimentology of the SW margin of Indochina to igneous geochemistry and detrital geochronology; Thailand-wide. Magmatic zircon Lu–Hf and whole-rock Sm–Nd data and model ages illustrate that the Indochina Terrane is relatively juvenile and distinct from the Sibumasu Terrane. The latter is composed of considerable Archean–Paleoproterozoic material. The granitoids of the Sukhothai Terrane are syn-collisional and are isotopically intermediate between Indochina and Sibumasu. I interpret this to reflect juvenile magmatism that is contaminated by evolved crustal material, which is likely to be from the leading edge of the Sibumasu Terrane as it enters the subduction zone during the closure of the Palaeo-Tethys Ocean. Detrital zircon analysis from Neoproterozoic–Triassic sequences from the Sibumasu Terrane track the terrane’s evolution from the Australian margin of Gondwana to its collision with the terranes of present-day Asia. The detrital record in conjunction with other palaeontological and stratigraphic evidence, indicates that during the early Permian, Sibumasu was still connected with Australia. In contrast, analysis of the biostratigraphy of the Khao Khwang Platform demonstrates this region of the Indochina Terrane was part of a tropical shallow marine environment from the Yakhtashian–Midian (Tethyan equivalents to middle Cisuralian to late Guadalupian). This biostratigraphic analysis revealed the presence of several separate carbonate platforms dominated by four major middle Permian facies: peritidal, platform interior, algal reef and basin slope, which are dated using foraminifera and algae. The comparison of the detrital zircon population spectra from Permo-Triassic sandstones across Thailand provides further evidence for the shared and separate parts of their tectonic histories. Primarily, the ages found in the Sibumasu Terrane are typical of provenance within Gondwana and contain both juvenile and evolved Hf signatures. In contrast, in the Sukhothai Terrane, the predominant age peak is 296–207 Ma and contains εHf(t) values that correspond to the isotopic signatures of the synchronous Sukhothai granitoids. Detrital data from the Triassic Huai Hin Lat Formation of the Indochina Terrane contain zircon age populations and characteristics similar to those of the South China Terrane. These results have implications for research on the Tethys Oceans, not only within Thailand but also for research conducted on greater Southeast Asian tectonics. Additionally, this study unearths information on the origin of the Thai terranes and their potential positions within Gondwana during the Neoproterozoic to early Paleozoic. I, Romana Elysium Carthew Dew, certify that this work contains no material, which has been accepted for the award of any other degree or diploma in my name in any university or other tertiary institution and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made in the text. In addition, I certify that no part of this work will, in the future, be used in a submission in my name for any other degree or diploma in any university or other tertiary institution without the prior approval of the University of Adelaide and where applicable, any partner institution responsible for the joint award of this degree. The author acknowledges that copyright of published works contained within this thesis resides with the copyright holder(s) of those works. I give permission for the digital version of my thesis to be made available on the web, via the University’s digital research repository, the Library Search and also through web search engines, unless permission has been granted by the University to restrict access for a period of time. I acknowledge the support I have received for my research through the provision of an Australian Government Research Training Program Scholarship.
Advisor: Collins, Alan Stephen
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 2019
Keywords: geology
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