California State University, Northridge Holocene
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CALIFORNIA STATE UNIVERSITY, NORTHRIDGE HOLOCENE-PLEISTOCENE SAND PROVENANCE IN THE CANTERBURY BASIN, EASTERN SOUTH ISLAND, NEW ZEALAND A thesis submitted in partial fulfillment of the requirements For the degree of Master of Science in Geology By Carrie Bender-Whitaker May 2013 The thesis of Carrie Bender-Whitaker is approved: ____________________________________ ___________________ John M. Jaeger, Ph.D. Date ____________________________________ ___________________ Richard V. Heermance, Ph.D. Date ____________________________________ ___________________ Kathleen M. Marsaglia, Ph.D., Chair Date California State University, Northridge ii ACKNOWLEDGMENTS I would first like to thank my committee members, Dr. Kathleen Marsaglia, Dr. John Jaeger, and Dr. Richard Heermance, for their time and support during this very significant milestone in my life. Very special thanks go to: Dr. Kathleen Marsaglia and Greg Browne for introducing me to the exciting world of New Zealand geology; IODP- MI and Shipboard Scientists of Expedition 317 for their contribution to this study; the faculty and staff of the CSUN geology department, for imparting me with the fundamental knowledge that has allowed me to achieve my goals; funding from NSF OCE 1060703 and BD-NSF HRD-0928852; my project members, Claire Bailey and Jasmyn Nolasco; and lastly my friends and family, who gave me the strength to never give up. iii TABLE OF CONTENTS SIGNATURE PAGE ii ACKNOWLEDGMENTS iii ABSTRACT vi INTRODUCTION 1 Background 1 New Zealand Tectonic Evolution 1 Geology of Southern Island New Zealand 2 Canterbury Basin Geology and Sequence Stratigraphy 4 Modern South Island Sediment Sources 6 Previous Petrologic Work 6 METHODS 8 RESULTS 11 Onshore River and Beach Samples 11 Offshore Core Samples 13 Sand texture 13 Overall Composition 14 Depth (Relative Age) Trends 15 DISCUSSION 18 Sand Provenance 18 Type 1 and Type 2 Facies Assemblage 20 Linking Sand Provenance to Depositional Environment 22 Origin(s) of the Mixed Provenance Samples 23 Feldspar Sources 24 CONCLUSIONS 25 REFERENCES 27 iv APPENDIX A: TABLES 33 APPENDIX B: FIGURE CAPTIONS 49 APPENDIX C: FIGURES 53 APPENDIX D: PLATE CAPTIONS 90 APPENDIX E: PLATES 92 v ABSTRACT HOLOCENE-PLESITOCENE SAND PROVENANCE IN THE CANTERBURY BASIN, EASTERN SOUTH ISLAND, NEW ZEALAND BY Carrie Bender-Whitaker Master of Science in Geology Integrated Ocean Drilling Program (IODP) Expedition 317 drilled four sites (U1351, U1352, U1353, and U1354) on a shelf-to-slope transit across the Canterbury Margin located off the east coast of the South Island, New Zealand. The purpose of this study was to petrographically analyze the Holocene-Pleistocene sandy intervals to determine how sand composition within the offshore Canterbury succession reflects the influence of both south-to-north (shore-parallel) and west-to-east (shore-perpendicular) sediment transport. Sand samples were obtained from both IODP drill core and onshore settings. Thirty-eight offshore core samples (10-20 cc) of Holocene-Pleistocene age and nine onshore samples (eight from rivers and one from a beach) were collected and air-dried. Offshore samples were sieved to separate the bulk sand-size fraction (2.0-0.0625 mm) and the onshore samples were sieved to separate medium, fine, and very-fine sand fractions. A total of 63 thin sections, 38 offshore and 25 onshore, were made and stained for feldspar recognition. Four hundred points (grains) were counted for each sample using the Gazzi-Dickinson method to estimate composition. Onshore samples range from quartzo-feldspathic (South) to lithic rich (Central/Northern). Mica and metamorphic lithic fragment proportions allow for further vi discrimination. Northern rivers draining mainly Torlesse lithologies are dominated by lower-grade metamorphic lithic fragments. Central rivers, draining the Torlesse to schist (semi-schist) transition, contain more high-grade metamorphic lithic fragments. The southern rivers are mica rich, having been derived from coarse schist. The differences observed in onshore samples allowed for the provenance classification of offshore samples as: 1) Northern (Torlesse Group), 2) Central (Torlesse-Schist Transition Group), 3) Southern (Schist Group), or 4) Mixed. The distribution of the sand composition in the shelf and slope sites reflects a complex interaction of different factors. Compositional trends indicate a dynamic system where shore-parallel and shore-perpendicular processes alternate on the shelf, and shore– perpendicular processes dominate on the slope. Mixing processes include: shelf currents, transgressive erosion, bioturbation, and earthquake liquefaction, plus potential drilling disturbances. vii Introduction Background The Integrated Ocean Drilling Program (IODP) selected the Canterbury Basin, located off of the east coast of South Island, New Zealand, as the focus site for Expedition 317 (Fig. 1). The objectives of this Expedition were to: 1) understand the late Miocene-Holocene history of global sea level change (esutasy), and its effect on the continental margin seismic sequences recognized by Lu and Fulthorpe (2004) in this region; 2) characterize sediment sources and uplift history on the Southern Alps, and 3) determine the interplay of along-strike and downslope sediment transport (Fulthorpe, et al., 2011). In post-cruise studies by shipboard scientists, the applications of various techniques are being used to study sequence formations within the Canterbury Basin. My study uses the sand provenance technique on Holocene to Pleistocene sand recovered in Expedition 317 cores. My main hypothesis is that sand composition in the offshore Canterbury succession reflects the influence of both south-to-north shore-parallel and west-to-east shore-perpendicular sediment transport. This can be tested by comparing the composition of offshore marine sands with sands from onshore source rivers directly east and further south of the Expedition 317 drill sites. Another hypothesis to be tested is that sand associated with sequence boundaries has distinct compositional signatures. New Zealand Tectonic Evolution The New Zealand islands are part of a continental fragment that formed as a result of subduction-accretion processes along the Pacific margin side of Gondwana during the Paleozoic and Mesozoic, known as the Rangitata Orogeny (Cox and Sutherland, 2007). In the late Early Cretaceous, the convergent tectonic regime was replaced by one of extension and crustal rifting that led to the separation of the New Zealand sub-continent 1 from Australia. Starting in the Eocene a complex transform-convergent plate boundary evolved (Cox and Sutherland, 2007). Today, New Zealand lies on the boundary that separates the Pacific and Australian tectonic plates known as the Alpine Fault (Fig. 1), a dextral strike-slip zone with 500 km displacement since the earliest Miocene (23Ma) (Kamp and Filzgerald, 1987). This fault connects two subduction zones: the Hikurangi Trough to the north and the Puysegeur Trench to the south. Geology of South Island New Zealand The South Island can be divided into two geological provinces separated by a long–lived (ca. 375-110 Ma) subduction-related Median Batholith (Cox and Sutherland, 2007). The western province basement is composed of Late Cambrian to Late Ordovician terranes that have undergone regional metamorphism, whereas the Eastern Province Brook Street, Murihiku, Matai, Caples, Bay of Islands (part of the former Waipapa), Rakaia (older Torlesse) and Pahau (younger Torlesse) terranes are most pertinent to this study. These are dominated by lithic and feldspathic metagreywackes, including volcanic, intrusive and ophiolitic rocks that were accreted to the Gondwana margin (Cox and Sutherland, 2007). The two major groups that make up the Eastern Province are the Torlesse terrane and its metamorphic equivalent, the Otago/Haast Schist (Fig. 2). Mortimer (2004) describes the Rakaia terranes (older Torlesse) as being dominated by a turbiditic submarine sandstone-mudstone association, exhibiting features that are consistent with deformation in an accretionary wedge, however it is unknown whether the depositional environment occurred at a passive or active margin. Fossils found within the Rakaia subterrane are of Permian, middle Triassic, and late Triassic age 2 (MacKinnon, 1983). The Torlesse terranes are dominated by quartzofeldspathic sandstone with minor amounts of argillite and conglomerate. Older Torlesse (Rakaia) terrane greywackes have a range of sand detrital modes (Q 24-40%, F 43-50%, and L17- 26%) with lithic fragments being dominantly silicic volcanic rocks; in contrast, most of the Caples terrane greywackes have a more lithic-dominated range of detrital modes (Q 10-35%, F15-20%, and L50-75%) with lithic clasts including mafic, intermediate and felsic volcanic rocks (Mortimer and Roser, 1992). During the Jurassic to Early Cretaceous, significant regional metamorphism overprinted areas within the Rakaia and Caples Terranes producing a major metamorphic belt, the Haast Schist (Cox and Sutherland, 2007) which includes the Rees, Kaimanawa, Marlborough, Alpine, Otago, and Chatham schists (Grindley et al., 1959; Hay et al., 1970). The Otago Schist has been described as a metamorphic welt, which overprints the Caples and Torlesses tectonostratigraphic terranes (Coombs et al., 1976). In the southern South Island, the Otago Schist forms a 150 km-wide north-west-trending structural anticlinorium (Cox and Sutherland, 2007). The Otago Schist is predominantly psammitic (medium size) and pelitic (fine