Carbonate Bank Development and Vertical Tectonic History of the Marshall Islands, Western Pacific: Ocean Drilling Program Related Research

马绍尔群岛是西太平洋的主要地貌和地质特征。它们的起源被归因于中生代太平洋板块越过热点，或者是由于大范围的板块中部火山活动的发生。在比基尼环礁和埃尼韦塔克环礁上的钻探，在邻近海山和海山上的测量和疏浚，以及在DSDP-IPOD作业期间进行的海洋钻探表明，许多环礁和毗邻的目前被暗礁覆盖的海山是始新世和白垩纪(？)始新世至白垩纪(？)侏罗纪时期在下沉的太平洋板块顶部喷发的火山地基。环礁以下和暗礁盖内石灰岩剖面的形态、内部相几何和成岩历史受控于新生代冰川消长引起的海平面波动。迄今为止的研究表明，自白垩纪末期或始新世早期以来，马绍尔群岛地区已下沉约1500米。这种异常快速的下沉速度在早期(？)侏罗纪时代被归因于板块中段的热复兴和板块抬升。该奖项支持的研究的目标是对马绍尔群岛被暗礁覆盖的水下海山和小岛进行水深和地震测绘和取样。这些研究将提供数据，以确定这一异常区域的沉降史，并确定与海平面波动有关的水下海山和珊瑚礁停止生长的相几何、成岩历史和停止生长的时间。这些数据还将用于规划未来在该地区的钻探。

The Marshall Islands are a major morphologic and geologic feature of the western Pacific. Their origin has been ascribed to the passage of the Mesozoic Pacific plate over hotspots or, alternately, to the occurrence of widespread, mid-plate volcanism. Drilling on Bikini and Enewetak atolls, surveying and dredging on neighboring seamounts and guyots, and ocean drilling carried out during DSDP-IPOD operations, have shown that the numerous atolls and adjoining presently submerged reef-capped seamounts are the result of Eocene and Cretaceous(?) to Recent reef growth on Eocene and Cretaceous(?) volcanic foundations that were erupted atop the subsiding Pacific plate of Jurassic age. The morphology, internal facies geometry, and diagenetic history of the limestone sections below the atolls and within the submerged reef-caps have been controlled be sea-level fluctuations induced by the waxing and waning of glaciers during the Cenozoic era. Studies to date indicate that the Marshall Islands region has subsided ~1500m since latest Cretaceous or Early Eocene time. This anomalously fast rate of subsidence on a lithospheric plate of Early(?) Jurassic age has been ascribed to a mid-plate thermal rejuvenation and uplift of the plate. Research supported in this award has as its objectives the bathymetric and seismic mapping and sampling of submerged, reef- capped seamounts and guyouts in the Marshall Islands. These studies will provide data with which to determine the subsidence history of this anomalous region and to determine the facies geometry, diagenetic history, and timing of cessation of reef growth of the submerged seamounts and guyouts as these relate to sea-level fluctuations. The data will also be used in planning future drilling in this area.