维嘉海山沉积过程及其对西太平洋海山演化的意义

Sedimentary Processes of Weijia Guyot and Implications for Western Pacific Seamount Evolution

海山沉积过程与全球气候变化和古海洋演化有着紧密联系,维嘉海山保留了西太平洋晚中生代以来的完整沉积记录,是探索西太平洋海山构造演化的理想场所.基于浅地层剖面、大洋钻探和最新相关研究成果,通过研究海山的沉积特征、火山活动和沉降速率等,探索西太平洋维嘉海山晚中生代以来的沉积过程.结果显示维嘉海山顶部发育3个沉积单元,并发现了始新世第二次火山活动的可能证据,推算出维嘉海山中中新世(~11.6 Ma)以来的沉积速率约为6.03 mm/ka.首次建立了维嘉海山的演化模型,认为维嘉海山演化主要经历了7个阶段,在渐新世之前处于缓慢沉降状态,其顶部水深一直保持在数百米之间,之后出现拐点,早中新世(~20 Ma)之后开始加速沉降,可能与该时期太平洋板块运动方向的迅速转换有关.

Sedimentary processes of seamounts are closely related to global paleoclimate change and paleoceanography evolution.The Weijia Guyot retained the complete sedimentary records since the Late Mesozoic,which made Weijia Guyot an ideal area for tectonic evolution studies of seamounts in the western Pacific Ocean.Based on the results from sub-bottom profiling,ocean drilling,and the latest research,in this paper it explores the sedimentary process of Weijia Guyot since Late Mesozoic by studying the sedimentary characteristics,volcanic activity and subsidence rate of the seamount.There are three sedimentary units on the summit of Weijia Guyot.Direct evidence of rejuvenated volcanism during Eocene is found in this paper,and deposition rate of Weijia Guyot is determined as approximately 6.03 mm/ka since Middle Miocene(~11.6 Ma).The evolution model of Weijia Guyot is established for the first time,which is being divided into seven main phases.New perspective about the subsidence rate of Weijia Guyot is revealed:the subsidence rate was low before Oligocene,and the water depth at the summit ranged within hundreds of meters;subsequently,the subsidence speeded up during Early Miocene(~20 Ma)after an inflection point,and it may be related to the rapid change of the direction of the Pacific plate movement during this period.