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The Influence of Lithospheric Flexure Induced by Volcano Loading on Neogene Basin Evolution in Mcmurdo Sound, West Antarctica

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The Influence of Lithospheric Flexure Induced by Volcano Loading on Neogene Basin Evolution in McMurdo Sound, West Antarctica THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Jie Chen Graduate Program in Geological Sciences The Ohio State University 2015 Master's Examination Committee: Dr. Terry Wilson, Advisor Dr. Michael Bevis Dr. Derek Sawyer Copyright by Jie Chen 2015 Abstract The marine Erebus Basin surrounds the volcanic Ross Island in McMurdo Sound, Antarctica. This basin has evolved under the influence of flexure driven by loading by the three volcanoes that make up Ross Island. Seismic reflection data west of Ross Island are used to document the seismic stratigraphic framework of the flexural basin. Five seismic units are mapped within the sedimentary infill of the basin. Seismic facies are documented within each unit, ranging from chaotic facies interpreted as volcanic mass flows and ice-proximal glacial deposits, to laminated units interpreted as alternating pelagic, hemipelagic and glaciomarine deposits. The volcanogenic units form part of the aprons around the volcano slopes and the glaciomarine units fill the axial basin. Two seismic sequences are defined based on patterns of surface depth and unit thickness. Seismic Sequence 1 is bounded by the Rj and Rk seismic surfaces, showing thickening and deepening toward Mount Bird volcano. Seismic Sequence 2 includes units from the Rk seismic surface up to the seafloor, and thickens and deepens toward Mount Erebus volcano. Seismic mapping thus shows evidence of two discrete sub-basins formed by Mt. Bird loading since 3.8-4.6 Ma and Mt. Erebus loading since ~1.31 Ma. Both units also show thickening in a zone northwest of Ross Island where accommodation space was formed by Terror Rift faulting, indicating that Terror Rift was still active when the Ross Island volcano loading occurred. ii The Bird-Erebus flexural basin has an overall wedge-shaped fill that thickens toward the volcanoes of Ross Island, typical of the geometry of other basins formed by volcano loads in ocean basins. The Erebus Basin is underfilled, with only ~325 m of infill, compared with >2000 m of fill typically found in moats around ocean island volcanic chains. Like stratal sequences of other flexural basins, the Bird-Erebus flexural basin fill shows onlap geometries in cross-moat profiles. However, unlike stratal sequences of other flexural basins, no offlap pattern is observed in either cross-moat or along moat profiles. Gravity flows related to mass wasting of Ross Island volcanoes are a significant component of the Bird-Erebus basin fill but, unlike other basins formed by volcano loads, is not the dominant fill. Instead, seismic facies mapping and AND-1B core show that a significant component of glaciomarine deposits occurs in the flexural basin. Glacial erosion removed some of the flexural basin fill, particularly along the regional Rk seismic surface. A 3D thin elastic plate model was used to simulate flexural basin evolution induced by Ross Island volcano loading, and to evaluate regional lithospheric strength. Using the dip angle of seismically mapped reflector surfaces as the constraint, the best fit lithospheric strength is represented by effective elastic thickness of 4-5 km. This weak lithosphere in the Ross Island region can be explained by faulting, thin crust, and high heat flow in this rift tectonic setting. iii Dedication This document is dedicated to my family. iv Acknowledgments Firstly, I would like to express my sincere gratitude to my advisor, Dr. Terry Wilson, for her support and guidance of my Master study, for her patience, great vision, incredible motivation, as well as the opportunity to do field work in Antarctica. Besides my advisor, I would like to thank Dr. Michael Bevis and Dr. Derek Sawyer for their insightful input from varies perspectives. Also, I would like to thank Dr. Stuart Henrys for his help in seismic work. The primary marine geophysical data used in this research were acquired on NBP0401 geophysical cruise, funded by the National Science Foundation. Also, the support of GRA throughout my years at OSU is funded by the National Science Foundation. An Educational Grant from Schlumberger provided the software Petrel for seismic interpretation. I would also like to thank members of our research team: Stephanie Konfal, Dave Saddler, Joel Main, Cristina Millan, Jamey Stutz, Tricia Hall, and Will Blocher. We’ve enjoyed a lot of moments, from playing football at sun shine Antarctica to fighting the deadlines at the basement of Orton. Lastly, I would like to thank my wife and best friend, Xiaorui. She is always sitting next to me. v Vita 2003................................................................Huangyan High School 2007................................................................B.S. Earth Sciences, Zhejiang University 2012 to present ..............................................Graduate Research Associate, School of Earth Sciences, The Ohio State University Fields of Study Major Field: Geological Sciences vi Table of Contents Abstract ............................................................................................................................... ii Dedication .......................................................................................................................... iv Acknowledgments............................................................................................................... v Vita ..................................................................................................................................... vi List of Tables ..................................................................................................................... xi List of Figures ................................................................................................................... xii Chapter 1: Introduction ....................................................................................................... 1 Chapter 2: Literature Review .............................................................................................. 3 2.1 Geological Setting ..................................................................................................... 3 2.1.1 The West Antarctic Rift System ......................................................................... 3 2.1.2 The Victoria Land Basin and Terror Rift ........................................................... 4 2.1.3 Ross Island Volcanic Complex........................................................................... 4 2.1.4 Regional Lithospheric Strength .......................................................................... 5 2.2 Isostasy and Lithospheric Flexure Model ................................................................. 7 2.3 Previous Flexural Studies of Ross Island Loading ................................................... 8 Chapter 3: Data ................................................................................................................. 10 vii 3.1 Digital Elevation Model (DEM) ............................................................................. 10 3.1.1 Land Surface Elevation of Ross Island............................................................. 10 3.1.2 Bathymetric Data for the Seafloor Surrounding Ross Island ........................... 11 3.1.3 Integrated DEM ................................................................................................ 12 3.2 Seismic Reflection Data .......................................................................................... 13 3.2.1 Reflection Seismology ...................................................................................... 13 3.2.2 Seismic Data Sources ....................................................................................... 14 3.2.3 Mis-tie Analysis ................................................................................................ 15 Chapter 4: Methods ........................................................................................................... 16 4.1 Workflow for this Study .......................................................................................... 16 4.2 Seismic Interpretation ............................................................................................. 17 4.2.1 Seismic Stratigraphic Techniques .................................................................... 17 4.2.2 Artifacts in Seismic Data .................................................................................. 19 4.2.3 Seismic Interpretation in Petrel ........................................................................ 20 4.3 Modeling Method .................................................................................................... 21 Chapter 5: Results ............................................................................................................. 23 5.1 Seismic Framework ................................................................................................. 23 5.1.1 Seismic Facies .................................................................................................. 23 5.1.2 Description of Seismic Surfaces and Units ...................................................... 31 viii 5.1.3 Age Constraints for Seismic Surfaces and Units .............................................. 39 5.2 Modelling ...............................................................................................................
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