Bathymetry of Valdivia Bank, Walvis Ridge, South Atlantic Ocean: Implications for Structure and Geologic History of a Hot Spot Plateau
Bathymetry of Valdivia Bank, Walvis Ridge, South Atlantic Ocean: Implications for Structure and Geologic History of a Hot Spot Plateau
复制标题
DOI：
10.1029/2022gc010624
复制
发表时间：
2022-11-01
影响因子：
3.5
通讯作者：
Zhou, H.
中科院分区：
文献类型：
--
作者：
Contreras, E.;Garcia, P. Jimenez;Zhou, H.
瓦尔迪维亚浅滩（Valdivia Bank）是南大西洋的一个海洋高原，由晚白垩世期间中大西洋海岭的热点岩浆活动形成。它是沃尔维斯海岭的一部分，沃尔维斯海岭是一个海岭和海山链，被广泛认为是由特里斯坦-高夫地幔柱的年龄递增火山作用形成的。为了更好地了解这座建筑物的形成和历史，我们通过将现有的多波束回声测深仪数据集与主要基于卫星测高（SRTM 15+）的测深网格合并，绘制了瓦尔迪维亚银行的测深图。测深图显示了以前未解决的特征，包括广泛的裂谷地堑，火山土丘和小圆丘，以及大规模的沉积物运输系统。在瓦尔迪维亚浅滩被侵位并可能在海平面被侵蚀后，它经历了一段时期的裂谷作用，随后是一次次级岩浆脉冲，导致区域抬升至海平面，随后又沉降至目前的深度。深度约为1 000米的浅岸是火山地壳隆起的厚沉积物堆积的结果。几个较浅的土丘（类似于1，000 -520米）和一个盖奥特（类似于220米）可能是在新生代岩浆事件期间形成的一个或多个火山岩顶上珊瑚礁生长的结果。随着沉积物在浅台地上的积累，形成了沉积物搬运系统，因为冲沟、水道和物质搬运沉积物切割出山谷和槽，将沉积物排入高原底部的深海扇。新的测深图表明，大洋高原在最初就位后很长时间内仍处于地质活动状态。
Valdivia Bank is an oceanic plateau in the South Atlantic formed by hot spot magmatism at the Mid-Atlantic Ridge during the Late Cretaceous. It is part of the Walvis Ridge, an aseismic ridge and seamount chain widely considered to be formed by age-progressive volcanism from the Tristan-Gough plume. To better understand the formation and history of this edifice, we developed a bathymetric map of Valdivia Bank by merging available multibeam echosounder data sets with a bathymetry grid based mainly on satellite altimetry (SRTM15+). The bathymetric map reveals previously unresolved features including extensive rift grabens, volcanic mounds and knolls, and large-scale sediment transport systems. After Valdivia Bank was emplaced and probably eroded at sea level, it underwent a period of rifting, followed by a secondary magmatic pulse that caused regional uplift to sea-level, followed by subsidence to current depths. Shallow banks at depths of similar to 1,000 m are the result of a thick sediment pile atop uplifted volcanic crust. Several shallower mounds (similar to 1,000-520 m) and a guyot (similar to 220 m) likely resulted from coral reef growth atop one or more volcanic pedestals formed during the younger Cenozoic magmatic event. As sediments accumulated on the shallow platforms, sediment transport systems developed as gullies, channels and mass transport deposits carved valleys and troughs, shedding sediment into abyssal fans at the plateau base. The new bathymetric map demonstrates that oceanic plateaus are geologically active long after initial emplacement.