Morphology and Stratigraphy of Continental Margins During Tertiary Global Change: From Carbonate Ramps to Clastic Progradation

在新生代，许多边缘发生了重大的形态变化，从碳酸盐斜坡演变为进阶碎屑陆架，而世界气候则从温室永久地转变为冰窖条件。早渐新世在NJ边缘发生了由碳酸盐斜坡到硅质陆架的转换。在安哥拉边缘始新世-渐新世边界时间证明了一次重大的侵蚀事件。中新世以来，两缘均以硅质沉积为主，并演化为现代陆架和陆架坡折的陆缘。这种模式在其他边缘也可以观察到，需要从渐新世到中新世的沉积物供应增加。到中渐新世，碳酸盐工厂在以前占主导地位的碳酸盐斜坡上关闭了。随着冰库条件的发展，由于大陆季节性和侵蚀的增强，海平面的长期下降和陆源沉积物供应的增加，硅-碎屑转移同时发生。该研究将重建非洲大陆边缘，从地震资料中了解大陆边缘形态和地层学的变化。将对边缘进行反剥或正演模拟，以确定近似的构造沉降。＊＊＊

9521336 Steckler In the Cenozoic many margins underwent major changes in morphology and evolved from carbonate ramp to prograding clastic shelves, while the world climate changed permanently from a hothouse to icehouse conditions. On NJ margin the switch from carbonate ramp to siliciclastic shelf occurred in the early Oligocene. On the Angola margin the Eocene-Oligocene boundary time evidenced a major erosional event. My Miocene both margins were dominated by siliciclastic progradation and margins evolved to the modern continental margins with flat shelves and shelf- slope breaks. This pattern is also observed at other margins and require an increase in sediment supply from Oligocene to Miocene. By mid-Oligocene the carbonate factory had shut down over the previously dominant carbonate ramps. The siliciclastic shift occurs at the same time as the development of the icehouse conditions, a long-term lowering of sea level and increase in terrigenous sediment supply due to enhanced continental seasonality and erosion. The study will reconstruct the African margin to understand the shift in continental margin morphology and stratigraphy from seismic data. Backstripping or forward modeling of the margin will be performed to determine the approximate tectonic subsidence. ***