Abstract

The Osborn Plateau is a large intraplate elevation in the eastern Indian Ocean, which has been poorly studied by geological and geophysical methods. On cruise SO258/1 aboard the R/V Sonne, new data were collected by Parasound seismic processing, multibeam survey, and, for the first time, dredging. Faults in the sedimentary cover, which extend to the seafloor surface, indicate high neotectonic activity in the area of the Osborn Plateau. It may have continued up to the present, as well as in the adjacent segment of the Ninetyeast Ridge, where strong earthquakes are recorded. Two reflectors A and C in the upper part of the sedimentary cover mark global regressive changes in the World Ocean level at the Pliocene–Pleistocene and Miocene–Pliocene and boundaries. Reflector B in sediments at the Lower–Upper Pliocene boundary is associated with a change in the regional hydrodynamic regime at the time in the eastern Indian Ocean. Reflector B at the Lower–Upper Pliocene boundary is associated with a change in the local hydrodynamic regime in the region of the plateau and was caused by uncompensated sedimentation. As a result of dredging, strongly altered vitroclastic tuffs were obtained, consisting of palagonized ash particles and lapilli. Analysis of geochemical data on the composition of palagonite made it possible to reconstruct the main geochemical features of the primary composition of glass in tuffs, in particular, high enrichment in incompatible elements (Nb, Zr, Ti, La, etc.). The results of studying the dredged rocks suggest that tuffs dredged on the Osborn Plateau were formed as a result of explosive volcanic eruptions of alkaline basalts under subaerial or relatively shallow conditions and represent the latest eruption products in the region.

中文翻译：

---

奥斯本高原（印度洋）火山凝灰岩的组成，新构造和上沉积层的结构

摘要

奥斯本高原是印度洋东部的一个较大的板块内高程，但对地质和地球物理方法的研究却很少。在R / V Sonne号上以SO258 / 1巡航，通过Parasound地震处理，多波束勘测以及首次疏ging收集了新数据。沉积覆盖层的断层延伸到海底表面，表明在奥斯本高原地区具有较高的新构造活动。它可能一直持续到现在，以及在九十里脊附近的那段记录有强烈地震的地方。沉积覆盖层上部的两个反射器A和C标记了上新世—更新世和中新世—上新世及其边界在世界海平面上的全球回归变化。印度洋东部-上新世边界下缘的沉积物中的反射器B与当时区域水动力状况的变化有关。在上新世下-上边界的反射器B与高原地区局部流体动力状态的变化有关，并且是由未补偿的沉积引起的。疏a的结果是，获得了由粉煤灰颗粒和青金石组成的玻璃体碎屑凝灰岩。通过分析有关方铅矿成分的地球化学数据，可以重建凝灰岩中玻璃主要成分的主要地球化学特征，特别是不相容元素（Nb，Zr，Ti，La等）的高度富集。对挖出的岩石进行研究的结果表明，在奥斯本高原上挖出的凝灰岩是在地下或相对较浅的条件下碱性玄武岩爆发性火山喷发而形成的，代表了该地区最新的喷发产物。