Longstanding goals of scientific ocean drilling include determining the timing and amplitudes of global sea-level change, as well as the role of eustacy in the generation and preservation of continental margin stratigraphy. However, continental margin sedimentation is a function of both allogenic and autogenic processes, and extracting a eustatic record requires an understanding of local sedimentary processes and their influence on strata formation. IODP Expedition 317 to Canterbury Basin, New Zealand provides an opportunity to identify the regional processes involved in the formation of sedimentary sequences where temporally evolving across-shelf and along-margin sediment sources potentially interact with both eustasy and tectonics to generate margin stratigraphy. This study defines sedimentary petrofacies using petrographic and X-ray diffraction techniques and combines them with lithofacies to characterize sedimentation within unconformity-bounded sequences. Differentiating the relative influence of each sediment source is made possible by the unique aspects of the onshore geology and sediment supplied by the rivers of South Island, New Zealand: in this system sediment composition is a proxy for transport mode/direction, with mica-rich schist detritus being brought in from the south, and graywacke Torlesse detritus from the west. Higher-resolution analyses will target specific seismic sequences from the Pliocene to Recent that represent changing climatic and eustatic conditions. A primary hypothesis tested is that recurring lithofacies motifs that likely formed during high-amplitude Pleistocene sea-level cycles can be linked to sediment provenance, and even where less lithologically distinct, a recognizable signal may remain in the detrital fraction. Another hypothesis is that the formation of Plio- Pleistocene sequences along the Canterbury Margin is strongly influenced by the relative sediment supply from alongshore/shelf (Clutha/Waitaki rivers) versus cross-margin (Rangitata-Ashburton-Rakaia braided system) transport, with the latter becoming more dominant in the later Pleistocene, potentially leading to an autogenic increase in accommodation space that lead to increased sequence preservation. A holistic approach is used to test these hypotheses, similar to that applied in the MARGINS Source-to-Sink focus site on North Island, New Zealand. This methodology links newly acquired data from onshore outcrops, stream and coastal deposits (collected in conjunction with New Zealand colleagues) to Expedition 317 results in order to evaluate potential basin-wide changes in sediment supply and distribution. Temporal changes in the relative timing and routing of sediment to the Canterbury margin are determined from comparisons between the cross-shelf (U1351, U1353, U1354) and the two Canterbury slope sites (ODP Site 1119 and U1352). Discrete mineralogical observations from this study eventually will be compared to and combined with high-resolution elemental and carbonate analyses proposed by Fulthorpe et al. to provide key petrologic and mineralogic constraints on core and seismic data interpretation for the margin, including distinguishing lithologic changes that might correspond to Milankovitch cyclicity. The history of global sea level change and the impact of future sea-level rise related to global warming are one of the foremost issues facing society. Drilling results from the Canterbury Margin represent a key global component of a comprehensive IODP program to extract sea-level information from continental margin stratigraphy. Our data and results will be made publically available through the IODP portal as part of the IODP Sample, Data, and Obligations Policy and through presentations at meetings and publications. This study will provide educational opportunities for a number of high school, undergraduate and graduate students at CSU Northridge and the University of Florida. One high school student from Florida will participate as part of the UF Student Science Training Program (UF-SSTP), a seven-week residential research program for junior and senior-level high schools students considering science careers. Two undergraduate and two graduate students will participate in this project from CSUN and UF, including students from underrepresented groups and it is expected this participation will form the basis for their theses (BS/MS) or dissertation. The project includes an educational outreach program at UF as part of the UF Geogator program that provides presentations to local K-12 programs about Earth and our environment. The program will make the research on global sea-level change accessible to the local Florida community, where rising sea level and the hazards associated with it are a growing societal concern.
Erosion from mountains and the transfer of this eroded sediment to the ocean is one of the primary means by which continents grow in size. Studying these sedimentary deposits has tremendous scientific and societal importance because continental margin sediments (e.g., those along shorelines, deltas, and continental shelves) provide most of the world’s population with energy and water. The purpose of this study was to examine how continental margins form using samples collected by drilling below the seafloor into these sediments. The east coast of the south Island of New Zealand was chosen because it has minimal disturbance from active geologic deformation (e.g., earthquakes, faulting), which allows us to study how changes in sea-level and sediment erosion in nearby mountains over geologic time (millions of years) influence how these deposits form. This information can be used to understand how sea-level change influences shorelines and how potential deposits of oil and gas may form along continental margins. These samples were collected during Integrated Ocean Drilling Program Expedition 317. In association with other post-expedition studies, our results provide information on how sediment delivery and dispersal in the ocean controls sedimentary deposit formation during known sea level cycles of the past 2.6 million years. Our results indicate that cycles in the types of sediments (sand versus mud) that comprise the sub-seafloor have a dominant sea-level control. However, climate-induced changes in ice-sheet volume on the South Island, New Zealand over the past one million years led to increased sediment supply from the southern Alps, leading to a compositional change in the sediments and an increased growth of the continental margin. Our work is the most complete characterization of the deposits in this study area and will add to the body of literature pertinent to energy exploration and production from such deposits. We have shared these results at national meetings of our respective scientific societies, and the summaries of these presentations are publicly available through the societies web pages. The impact of this work has also been shared through public presentations at annual open houses that the Department of Geological Sciences organizes through the Florida Museum of Natural History ("Can You Dig It?", held every March). Results are publicly available through a data report published through the Expedition Bibliography site (http://publications.iodp.org/proceedings/317/317bib.htm). We have used results from our study in the undergraduate course in Sedimentary Geology taught by Jaeger in the Department of Geological Sciences, University of Florida. We also trained graduate and undergraduate students in analytical techniques that are in demand within the environmental and energy industries.
