Deciphering the Record of Sediment Transfer and Deposition Across Continental Slopes and the Margins of Other Deep-Water Basins

点击翻译按钮获取中文摘要

The floors of the world's deepest oceans arguably represent the most poorly understood land-/sea-scape on the planet, owing primarily to their inaccessibility and associated extreme conditions (e.g., high pressure). As we seek information about other planets in our solar system such as Mars, our oceans remain a significantly understudied frontier on planet Earth. Large subaqueous avalanches, or gravity flows, are known to transport fluid and sediment through river-like channels across vast expanses of the seafloor on continental margins, in water depths of 1-3 km or more. Unfortunately, direct measurement of these events is often very difficult, and we are forced to draw insight about them from indirect means, including destruction of infrastructure on the seafloor such as communication cables and pipelines. Another means to better understand these high-energy events in the deep-sea is to study their deposits, which can be captured in drillcores, or in the case of ancient examples, uplifted into mountain belts by major tectonic events. The proposed research will focus on Cretaceous-aged deep-sea deposits that are exposed at the Earth's surface in outcrops of southern Chile and western British Columbia. Evidence for immense gravity flows that shaped the ancient seascapes are present, represented by deep erosion surfaces associated with scours and channels, distinctive units that were left behind as gravity flows passed over an area, and thick deposits that accumulated when gravity flows lost their energy and came to rest. The research entails mapping geological features and rock types exposed in outcrops in each field area, and then incorporating the information into three-dimensional computer models, which reveal the geometry of geomorphological features (e.g., channels) and the character of their component rock types. By studying these ancient deposits in Chile and British Columbia, we will gain insight into sediment transfer in arguably the last true Earthly frontier: our deep oceans. An important applied motivation for this study is to better constrain potential hydrocarbon-bearing deep-water rocks on the margins of Canada and other continental slopes around the globe.