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Evolution and Deformation of the Onshore Eucla Basin During the Cenozoic

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Evolution and Deformation of the Onshore Eucla Basin During the Cenozoic Government of Western Australia Department of Mines and Petroleum RECORD 2016/10 EVOLUTION AND DEFORMATION OF THE ONSHORE EUCLA BASIN DURING THE CENOZOIC by LC Mounsher Record 2016/10 EVOLUTION AND DEFORMATION OF THE ONSHORE EUCLA BASIN DURING THE CENOZOIC by LC Mounsher Perth 2016 MINISTER FOR MINES AND PETROLEUM Hon. Sean K L’Estrange MLA DIRECTOR GENERAL, DEPARTMENT OF MINES AND PETROLEUM Richard Sellers EXECUTIVE DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIA Rick Rogerson REFERENCE The recommended reference for this publication is: Mounsher, LC 2016, Evolution and deformation of the onshore Eucla Basin during the Cenozoic: Geological Survey of Western Australia, Record 2016/10, 70p. National Library of Australia Card Number and ISBN PDF 978-1-74168-695-1 About this publication This Record is an Honours thesis researched, written and compiled as part of a collaborative project between the Geological Survey of Western Australia (GSWA) and Curtin University, Western Australia. Although GSWA has provided support for this project including access to core, the scientific content of the Record, and the drafting of figures, was the responsibility of the author. No editing has been undertaken by GSWA. Disclaimer This product was produced using information from various sources. The Department of Mines and Petroleum (DMP) and the State cannot guarantee the accuracy, currency or completeness of the information. DMP and the State accept no responsibility and disclaim all liability for any loss, damage or costs incurred as a result of any use of or reliance whether wholly or in part upon the information provided in this publication or incorporated into it by reference. Published 2016 by Geological Survey of Western Australia This Record is published in digital format (PDF) and is available online at <www.dmp.wa.gov.au/GSWApublications>. Further details of geological products and maps produced by the Geological Survey of Western Australia are available from: Information Centre Department of Mines and Petroleum 100 Plain Street EAST PERTH WESTERN AUSTRALIA 6004 Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444 www.dmp.wa.gov.au/GSWApublications Cover image: Elongate salt lake on the Yilgarn Craton — part of the Moore–Monger paleovalley — here viewed from the top of Wownaminya Hill, 20 km southeast of Yalgoo, Murchison Goldfields. Photograph taken by I Zibra for the Geological Survey of Western Australia Department of Applied Geology Honours Manuscript - 2013 Evolution and deformation of the onshore Eucla Basin during the Cenozoic Lewis Clark Mounsher Supervised and edited by Dr Milo Barham (Department of Applied Geology) and Dr Michael O’Leary (Department of Environment and Agriculture) A research project in partial fulfilment of the requirements of the unit ‘Geology Honours Dissertation 400’ for the degree Bachelor of Science (Honours) at Curtin University Affirmation of Research I hereby declare this to be a reflection of my own work. The following list details the work I took on personally in the course of completing this project: x Field work: my supervisors and I surveyed the elevations of subsurface carbonate horizons at 27 sites (predominately caves) across the Nullarbor and Roe Plains. This was done over a period of 10 days. x Acquisition of supplementary data: I supplemented the field data set with horizon elevations acquired from 63 drill holes. This data was sourced by sifting through 100+ online drillhole logs retained by the Geological Survey of South Australia. My supervisors and I also logged the depths of the carbonate horizons in an additional 12 Eucla Basin cores at the Carlisle Core Library. x I created and managed a database of the field and supplementary data, and interrogated the data within Esri ArcMap and Esri Arcscene to produce 2D and 3D models as required. x Fault analysis: I identified a number of faults on the Nullarbor and Roe Plains using a DEM and conducted various analyses on them (including the generation of displacement profiles and fault trace orientation analyses). Lewis Mounsher List of Contents 1.0 Introduction.....................................................................................................1 2.0 Regional Setting..............................................................................................1 2.1 Geological evolution of Australia’s southern margin .........................................2 2.2 Eucla Basin stratigraphy ...................................................................................2 2.2.1 Sedimentological descriptions of the Eucla Platform limestones............3 2.3 An overview of Cenozoic tectonics in the onshore Eucla Basin........................5 3.0 Materials and Methods ...................................................................................7 3.1 Acquisition of contact elevation data.................................................................7 3.1.1 Field data acquisition .............................................................................8 3.1.2 Supplementary data acquisition .............................................................8 3.1.3 Analysis and visualisation of contact elevation data...............................9 3.2 Fault analyses.................................................................................................10 3.2.1 Generation of displacement profiles.....................................................10 3.2.2 Analysis of fault orientations ................................................................11 3.2.3 Review of magnetic data......................................................................11 4.0 Data................................................................................................................11 4.1 Field data evidencing marine planation...........................................................11 4.2 Contact elevation data ....................................................................................12 4.3 Fault data........................................................................................................12 5.0 Data Interpretation........................................................................................13 5.1 Character of the basal Nullarbor Limestone horizon.......................................13 5.2 Interpretation of fault data ...............................................................................14 6.0 Discussion.....................................................................................................15 6.1 The basal Nullarbor Limestone horizon – constraints on tilting.......................15 6.2 Localised faulting and the stress field .............................................................16 i 6.2.1 The continent-scale neotectonic stress field ........................................16 6.2.2 The local neotectonic stress field .........................................................17 6.3 Fault kinematics, growth rates and growth models .........................................18 6.3.1 Kinematics............................................................................................18 6.3.2 Fault growth rates ................................................................................19 6.3.3 Fault growth models.............................................................................20 6.4 The Mundrabilla Fault and historic stress field partitioning .............................20 7.0 Conclusions ..................................................................................................21 8.0 Acknowledgements ......................................................................................22 9.0 References ....................................................................................................23 10.0 Figures...........................................................................................................26 11.0 Tables ............................................................................................................51 12.0 Appendices ...................................................................................................52 ii List of Figures Figure 1 A map depicting the location and extent of the Eucla Basin…….. ..........26 Figure 2 Stratigraphic chart of the Eucla Basin……..............................................27 Figure 3 The inferred position of the Lasseter Shear Zone…….. .........................28 Figure 4 Locations of the 27 field sites and 75 additional sites from which elevation data was obtained…….. ..........................................................29 Figure 5 Fault traces for the 46 Nullarbor and Roe Plains faults…….. .................30 Figure 6 The expression of the contact between the Abrakurrie Limestone and the Mullamullang Member of the Nullarbor Limestone at Kutawala Cave……................................................................................................31 Figure 7 The location of the Madura Quarry and the degree of horizontality of the underlying planation surface.……...........................................................32 Figure 8 A model depicting the character of the basal Nullarbor Limestone horizon.……............................................................................................33 Figure 9 Vertical displacement profiles for the 27 onshore faults deemed to be significant.…….. ............................................................................... 34-36 Figure 10 A rose diagram depicting the strike orientation of faults (and discretely-
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