Geomorphic Evolution and Heterogeneity of Holocene Carbonate Tidal Sand Shoals

堪萨斯大学全新世碳酸盐岩潮滩的地貌演化和非均质性吉恩·兰基地球表面变化的档案包含在它的地层记录中。尤其是卵圆形(球状同心层状颗粒)的沉积，为数十亿年来海洋中的物理和化学变异性提供了关键的见解。正在进行的研究已经阐明了不同的基岩形态、潮汐和波浪如何导致今天活跃的潮汐主导的橄榄沙洲中不同的几何形状(潮汐三角洲、潮汐沙脊、抛物线沙洲、S形沙洲)。这项研究将在这些洞察力的基础上扩展，探索这样一种假设，即这些变化过程为每个浅滩几何形状提供了独特的地层记录。为了解决这些问题并验证这一假设，这项研究将利用一套全新世巴哈马浅滩的高分辨率海底地球物理剖面图、取心和年龄测定，这些浅滩具有不同的过程和地貌特征。通过比较浅滩下面基岩的厚度、高程和浅滩内的沉积学趋势，这项研究的结果将有助于加深对这些橄榄体系以及潮汐沙洲总体演化的理解。此外，准确的测年将揭示地貌变化的速率，这是硅质碎屑体系中难以确定的信息。总的来说，这些数据将提供关键的见解，以更好地约束对地球历史的解释，以应对全球变化，预测地下(例如，水或碳氢化合物储集层中)蚝粒沉积岩的分布和变异性，并了解采砂可能的回收率。这项提议将资助巴哈马和国际学生在巴哈马埃留瑟拉岛上的岛屿学校为巴哈马和国际学生提供的几个学期的讲座、动手实验室和实地经验的综合发展。

Geomorphic Evolution and Heterogeneity of Holocene Carbonate Tidal Sand ShoalsGene Rankey, University of KansasThe archive of change on the Earth's surface is contained in its stratigraphic record. Deposits of ooids (spherical concentrically laminated grains) in particular have provided key insights into physical and chemical variability in the ocean over billions of years. On-going research has illustrated how variable bedrock configurations, tides and waves lead to different geometries (tidal deltas, tidal sand ridges, parabolic bars, sigmoidal bars) in tidally dominated oolitic sand shoals that are active today. This study will expand on those insights, exploring the hypothesis that these variable processes impart a distinct and unique stratigraphic record to each shoal geometry. To address these questions and test the hypothesis, this study will utilize high-resolution subbottom geophysical profiling, coring, and age dating from a suite of Holocene Bahamian shoals characterized by different processes and landforms. In comparing the thicknesses, the elevation of the bedrock beneath the shoals, and sedimentologic trends within the shoals, the results of this study will lead to enhanced understanding of evolution of these oolitic systems, and to tidal sand shoals in general. Furthermore, precise age dating of the oolitic sediments will reveal the rates of geomorphic change, information difficult to ascertain in siliciclastic systems. Collectively, these data will provide key insights to better constrain interpretation of the planet's history in response to global change, to predict the distribution and variability of oolitic sedimentary rocks in the subsurface (e.g., in water or hydrocarbon reservoirs), and to understand possible rates of recovery from sand mining. This proposal will fund development of mix of lecture, hands-on lab, and field experiences on ooid shoals for Bahamian and international students, offered by the PI and student for several semesters, at the Island School on Eleuthera Island in The Bahamas.