Sedimentology of the Rio Grande Rise area

Surface sediment samples and three gravity cores from the eastern terrace of the Vema Channel, the western flank of the Rio Grande Rise, and the Brazilian continental slope were investigated for physical properties, grain size, and clay mineral composition. Discharge of the Rio Doce is responsible for kaolinite enrichments on the slope south of 20° and at intermediate depths of the Rio Grande Rise. The long-distance advection of kaolinite with North Atlantic Deep Water from lower latitudes is of minor importance as evidenced by low kaolinite/chlorite ratios on the Mid-Atlantic Ridge. Cyclic variations of kaolinite/chlorite ratios in all our cores, with maxima in interglacials, are attributed to low-and high-latitude forcing of paleoclimate on the Brazilian mainland and the related discharge of the Rio Doce. A long-term trend toward more arid and 'glacial' conditions from 1500 ka to present is superimposed on the glacial-interglacial cyclicity.

对来自维玛海峡东部阶地、里奥格兰德隆起西部斜坡以及巴西大陆坡的表层沉积物样品和三个重力柱状样品进行了物理性质、粒度和粘土矿物组成的调查。里约多斯河的排放是导致20°以南斜坡和里奥格兰德隆起中等深度的高岭石富集的原因。从较低纬度向北大西洋深层水的长距离输送的高岭石对大西洋中脊上低高岭石/绿泥石比值的形成影响较小。在我们所有柱状样品中，高岭石/绿泥石比值随冰期和间冰期的循环变化，以间冰期达到峰值，这归因于巴西大陆古气候的低纬度和高纬度驱动，以及里约多斯河的相关排放。从1500 ka至今，长期向更干旱和‘冰川’条件转变的趋势叠加在冰期-间冰期周期上。