Collaborative Research: Expedition 317 Objective Research - Linking Sediment Provenance to Supply and Lithofacies Formation on the Canterbury Margin

科学海洋钻探的长期目标包括确定全球海平面变化的时间和幅度，以及在大陆边缘地层学的形成和保存过程中海平面上升的作用。然而，大陆边缘沉积是异体和自生过程的作用，提取浮沉记录需要了解当地的沉积过程及其对地层形成的影响。新西兰坎特伯雷盆地的IODP 317考察队提供了一个机会，以确定沉积序列形成过程中涉及的区域过程，在该过程中，跨大陆架和沿边缘的沉积物源在时间上演化，可能与尤斯达和构造相互作用，从而产生边缘地层学。本研究利用岩石学和x射线衍射技术定义了沉积岩相，并将其与岩相相结合，以表征不整合层序中的沉积特征。区分每种沉积物来源的相对影响是可能的，因为岸上地质和新西兰南岛河流提供的沉积物的独特方面：在这个系统中，沉积物组成是运输方式/方向的代表，富含云母的片岩碎屑从南部带入，而格雷瓦克Torlesse碎屑从西部带入。更高分辨率的分析将针对从上新世到近代的特定地震序列，这些序列代表着气候和上升条件的变化。一个初步的假设是，可能在更新世海平面高振幅旋回期间形成的反复出现的岩相基序可以与沉积物的来源联系起来，即使在岩性不太明显的地方，碎屑部分也可能保留一个可识别的信号。另一种假说认为，坎特伯雷边缘的上更新世-更新世层序的形成受到海岸/陆架（Clutha/Waitaki河）和跨边缘（Rangitata-Ashburton-Rakaia辫状系统）相对沉积物供应的强烈影响，后者在更新世后期变得更加占优势，可能导致自生空间的增加，从而增加了层序的保存。一个整体的方法被用来测试这些假设，类似于在新西兰北岛的边际源到汇的重点站点应用的方法。这种方法将新获得的来自陆上露头、溪流和海岸沉积物的数据（与新西兰同事一起收集）与远征317的结果联系起来，以评估沉积物供应和分布在整个流域的潜在变化。通过比较交叉陆架（U1351、U1353、U1354）和两个坎特伯雷斜坡站点（ODP站点1119和U1352），确定了沉积物相对时间和流向坎特伯雷边缘的时间变化。本研究的离散矿物学观测结果最终将与Fulthorpe等人提出的高分辨率元素和碳酸盐分析相比较并结合，为岩心和边缘地震数据解释提供关键的岩石学和矿物学约束，包括区分可能对应于米兰科维奇旋回的岩性变化。全球海平面变化的历史以及与全球变暖相关的未来海平面上升的影响是社会面临的首要问题之一。坎特伯雷边缘的钻探结果代表了从大陆边缘地层学中提取海平面信息的综合IODP计划的关键全球组成部分。我们的数据和结果将通过IODP门户网站作为IODP样本、数据和义务政策的一部分，并通过会议和出版物的介绍向公众提供。这项研究将为科罗拉多州立大学北岭分校和佛罗里达大学的一些高中生、本科生和研究生提供教育机会。来自佛罗里达州的一名高中生将参加佛罗里达大学学生科学培训计划（UF- sstp）的一部分，这是一个为期七周的住宿研究计划，面向考虑从事科学职业的初高中学生。两名本科生和两名研究生将参与该项目，包括来自代表性不足的群体的学生，预计这将成为他们毕业论文（学士/硕士）或学位论文的基础。该项目包括佛罗里达大学的教育推广计划，作为佛罗里达大学地理学家计划的一部分，该计划为当地K-12课程提供有关地球和环境的演讲。该项目将使佛罗里达当地社区能够进行全球海平面变化的研究，在那里，海平面上升及其相关的危害是一个日益受到社会关注的问题。

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.