PhD Opportunities in Detrital Geochronology/Sedimentary Provenance and Clastic Sedimentology/Basin Analysis, Brisbane, Australia

 Project Descriptions (Further details can be found on the following link: http://www.earthworks-jobs.com/geoscience/qut13091.html) :

PhD Project 1: Detrital Geochronology and Sedimentary Provenance
Sediments are one of the main recorders of tectonic events and provide a sample of large regions of continental crust not easily accessible in outcrop or that have been removed by uplift and erosion in response to major mountain building events. While U/Pb dating of zircon has become an increasingly standard means of interpreting mountain building events and tracing sediment sources, ambiguity in interpreting source regions results when candidate source terranes have similar ages for a given radioisotopic system. Recent advances in multi-dating - applying different geochronologic and thermochronologic systems to mineral grains in sedimentary rocks, now allow for unprecedented levels of detail in provenance and tectonic studies of sediments. New insights on the location, age, and exhumation history of source terranes, and dynamics of orogenic processes can therefore be gained.
The Late Devonian to Early Carboniferous (~380-320 Ma) period in Australia was characterised by intraplate orogenic events in central Australia (Alice Springs Orogeny), from which a major sheet of cratonic-derived quartz-rich sand spread outwards, principally across central and western Australia. A missing link in our understanding and record of this enigmatic intraplate mountain building event has been the huge volumes of quartz sediment also shed eastwards at this time. For example, the Drummond Basin of northeastern Australia has stored >40,000 km^2 and up to 7 km thickness of quartz sandstone. However, the Drummond Basin was developing as a wide volcanic-rift basin in board of the active plate boundary.
This project is to test the hypothesis that craton-derived quartz sand sedimentation in eastern Australia was a far-field response to the final stages of the coeval central Australian Alice Springs Orogeny. It will involve the application of multiple dating techniques to enable source differentiation for these sandstones, revealing both the igneous and high-grade metamorphic history by focussing on U/Pb zircon and rutile ages by Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS) analysis. These new data will provide novel insights into the relationship and timing of sedimentation and deformation events on the distal margin of one of the world's best examples of an intracratonic orogen. Two expected outcomes of this study are that: 1) the distal sedimentary record will provide new constraints on the duration and nature of unroofing by intraplate deformation; and 2) the effects of intracratonic deformation via a high sediment flux on the tectonic development of the northeastern Australian margin will be emphasised, with implications for back-arc deformational style of continental margins.
Students will use stratigraphy, field mapping/drill core logging, sedimentary petrology, and geochronological techniques to address the research questions. A student with recent research experience in detrital geochronology and/or provenance analysis will be preferred. All research costs for this PhD Project will be supported by an Australian Research Council Discovery grant.
Project Supervisors: Dr Scott Bryan & Dr Charlotte Allen.


PhD Project 2: Clastic Sedimentology and Basin Analysis
Sediments are one of the main recorders of tectonic events and provide a sample of large regions of continental crust not easily accessible in outcrop or that have been removed by uplift and erosion in response to major mountain building events. One important consequence of recent zircon dating provenance studies is the recognition of large, continent-wide sediment dispersal systems operating in response to major mountain-building events. These systems delivered large volumes of sediment to geographically remote continental margins and basins with no connection to the source region undergoing tectonism. The orogenic forcing, paleogeographic dynamics and type of sediment transport systems operating remain poorly understood. Furthermore, recent studies are implicating that sediment fluxes, often thought of as a consequence of tectonic deformation, may act to amplify or dampen rifting. Consequently, the depositional and rift history of a sedimentary basin may be altered by high sediment fluxes introduced by transcontinental sediment dispersal systems carrying detritus from distant, rising mountain belts 1000's km away. Critically, such basin-fill histories can provide valuable temporal links between tectonic processes operating in different parts of a continent or supercontinent, giving greater insight into tectonic and crustal evolution, as well as continental-scale paleogeography.
The Late Devonian to Early Carboniferous (~380-320 Ma) period in Australia was characterised by intraplate orogenic events in central Australia (Alice Springs Orogeny), from which a major sheet of cratonic-derived quartz-rich sand spread outwards, principally across central and western Australia. A missing link in our understanding and record of this enigmatic intraplate mountain building event has been the huge volumes of quartz sediment also shed eastwards at this time. For example, the Drummond Basin of northeastern Australia has stored >40,000 km^2 and up to 7 km thickness of quartz sandstone. However, the Drummond Basin was developing as a wide volcanic-rift basin in board of an active plate boundary.
This project is to test the hypothesis that craton-derived quartz sand sedimentation in eastern Australia was a far-field response to the final stages of the coeval central Australian Alice Springs Orogeny. It will involve stratigraphic, sedimentologic and facies analysis of key basins to: 1) define vectors to sediment source regions (e.g., by lateral coarsening trends in conjunction with paleocurrent data), particularly for the Drummond Basin; 2) provide well-constrained stratigraphic controls on age dated samples in companion PhD projects; 3) reveal spatial and temporal variations of sediment provenance within the quartz sandstone formations based on stratal architecture; 4) provide new insights into the interaction of extrabasinal quartz sandstone with intrabasinal volcanism and volcanogenic sedimentation; and 5) identify likely sediment pathways that deliver quartz sand to the continental margin edge, from which new paleogeographic maps of the region can be constructed. Two expected outcomes of this study are that: 1) the distal sedimentary record will provide new constraints on the duration and nature of unroofing by intraplate deformation; and 2) the effects of intracratonic deformation via a high sediment flux on the tectonic development of the northeastern Australian margin will be emphasised, with implications for back-arc deformational style of continental margins.
Students will use stratigraphy, field mapping/drill core logging, sedimentology and basin analysis, sedimentary petrology, and geochronological techniques to address the research questions. A student with recent research experience in sedimentology and stratigraphy or basin analysis will be preferred. All research costs for this PhD Project will be supported by an Australian Research Council Discovery grant.
Project Supervisors: Dr Scott Bryan, Professor Chris Fielding & Dr Charlotte Allen