REU: The Stratigraphy of Late Pleistocene Amazon Fan Sediments

亚马逊深海扇是典型的大型现代深海扇。过去的研究记录了扇的结构和表面形态，包括最近穿过扇的活跃通道的位置和特征。在这条水道附近收集的岩心样品是在冰川后海平面上升后活动停止之前由水道化的水流沉积的沉积物。在这里，我们建议(1)利用形态学和沉积学数据来确定河道化浊度流的可能特征，(2)发展一种地层学，使我们能够确定扇上沉积活动的年龄。地层学将以三角洲0-18曲线为基础，辅以AMS C-14日期。NCSU开发的新技术可以在含有少量有孔虫的样品上测量0-18，这在高沉积速率的岩心中具有优势。生物成因碳酸盐的AMS C-14测年和花粉分析有助于限制地层年龄。在下坡流最小的中下部扇区开发的基准同位素地层学将应用于下坡流更常见的最近活跃的水道/堤坝区域。这样的地层学将使我们能够确定与沉积事件有关的年龄，例如水流停止流向废弃的河道和主要泥石流的就位。然后，我们可以确定扇过程的速率，并将沉积模式与海平面联系起来。高分辨率的0-18地层学对于评估亚马孙河的冰期晚期/间冰期早期在确定古气候和古海洋变化方面的作用也很有价值。

The Amazon Deep-Sea Fan is a typical large modern deep-sea fan. Past studies have documented the structure and surface morphology of the fan, including the location and character of the most recently active channel which crosses the fan. Cores collected in the vicinity of this channel sample the sediments deposited by channelized flows before activity ceased following post-glacial sea level rise. We propose here (1) to use morphological and sedimentological data to determine the likely characteristics of channelized turbidity currents and (2) to develop a stratigraphy which will allow us to determine the age of sedimentary activity on the fan. The stratigraphy will be based on delta 0-18 curves supplemented with AMS C-14 dates. New techniques developed at NCSU can measure 0-18 on samples containing few foraminifera, an advantage in cores with high sedimentation rates. AMS C-14 dates on the biogenic carbonates and pollen analysis will help to constrain the stratigraphic dates. Benchmark isotope stratigraphies, developed in the middle and lower fan areas where downslope flows are minimal, will applied to the most recently active channel/levee areas where downslope flows are more common. Such a stratigraphy will allow us to determine the ages associated with depositional events such as the cessation of flow down abandoned channels and the emplacement of major debris flows. We can then determime rates for fan processes and tie depositional patterns to sea level. The high-resolution 0-18 stratigraphy will also be valuable for assessing the late glacial/early interglacial role of the amazon River in determining paleoclimate and paleoceanograhic changes.