Seamount chains, fracture zones, and Oceanic megatrends

被引:0
作者
Smoot, N. Christian
机构
来源
BOLLETTINO DELLA SOCIETA GEOLOGICA ITALIANA | 2005年
关键词
Hot lines; megatrends; ocean basins; tectonics; geomorphology;
D O I
暂无
中图分类号
P5 [地质学];
学科分类号
0709 ; 081803 ;
摘要
Fracture zones and seamount chains are imprinted on the ocean floor ubiquitously, each having been formed by different tectonic processes according to the plate tectonic hypothesis. Relative motion of the lithosphere, or plate; that is, relative to the deep upper mantle, is shown by the spreading phenomena such as fracture zone azimuths and the perpendicularly-oriented ocean floor fabric, called tectonic spreading fabric. Absolute motion of the lithosphere; that is, relative to the surface, could be defined by the linear features, such as the seamount/island sequentially-aged hotspot trails. This means that two sets of lineations could co-exist on the same lithosphere, and that absolute motion could change randomly, such as the proposed 43 Ma event. On further investigation, the idea of sequentially-aged seamounts being produced by hotspot/mande diapir activity has been largely disproven, as very few sequentially aged seamount chains exist in nature. The use of multibeam sonar survey data has shown that fracture zones are not locked and strong. Rather, they are zones of weakness, subject to leakage as attested to by the large amount seamount overprinting in fracture zones. With the advent of the satellite altimetry data, longer trends are found to transverse all ocean floors. These trends encompass the fracture zones and seamount chains in a pattern that shows at least four azimuths, again on all ocean floors. The lineaments pass through rocks known lobe up to 1.5 Ga in age, rather than the proposed 180 Ma. Because of all the tectonic activity, the lineaments are felt to be underlain by "hot lines"; that is, linear magma chambers of some sort. The lineaments are called megatrends, and they belie the definition of seafloor spreading by their very existence. Additionally, the megatrends join with lineaments on land, pass through the continents, and continue in the adjacent ocean basins. Most of the megatrends show no offsets due to horizontal tectonism, having undergone vertical tectonism instead.
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页码:23 / 52
页数:30
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