东海陆架盆地南部剥蚀厚度恢复及构造演化特征

针对钻井少、勘探程度低的东海陆架盆地南部，利用丰富的地震资料，综合地层趋势对比法、泥岩声波时差法及沉积波动分析法，对其关键不整合面剥蚀厚度进行了计算，并在区域构造背景分析及平衡剖面恢复的基础上，探讨了盆地充填结构及构造演化过程，结果显示：古新世末-早始新世时期剥蚀作用强，形成T₄⁰不整合面，椒江-丽水凹陷斜坡带和凸起带剥蚀量最高，达800~1000 m，福州凹陷较小，主要在200~400 m，而钓北凹陷则介于200~600 m；渐新世末—早中新世形成的T₂⁰不整合面剥蚀趋势变化较为平缓，钓北凹陷西斜坡、福州凹陷北部、雁荡低凸起以及椒江-丽水凹陷西斜坡南段剥蚀量较大，在500~600 m，其它区域分布较均匀；古新世，裂陷首先在西部坳陷带发育，形成“东断西超”的箕状结构。始新世，裂陷中心跃迁至东部坳陷带，钓北凹陷形成“双断结构”，西带则开始进入拗陷-反转阶段，随后的渐新世东带也进入拗陷-反转期，但反转作用均并不明显，钓北凹陷逐渐变为西向超覆的箕状盆地。中新世之后，东海陆架盆地自西向东逐步进入区域沉降阶段。

Erosion thickness recovery and tectonic evolution characterization of southern East China Sea Shelf Basin

Considering the fact that only a few exploratory wells in southern East China Sea Basin were drilled,we resorted to sufficient seismic data here to restore the critical unconformity erosion thickness and study the basin infilling and tectonic evolution by employing approaches including stratigraphic trends contrast,acoustic travel time,and sedimentary fluctuation analyses.The results show that the denudation of the basin was the most intensive during the Late Paleocene and Early Eocene,leading to the formation of the T₄⁰ unconformity with the largest erosion thickness of 800-1 000 m in the slope and uplift zones of Jiaojiang-Lishui Sag,and the least erosion thickness of 200-400 m in Fuzhou Sag as well as the medium erosion thickness of 200~600 m in Diaobei Sag.During the Late Oligocene and Early Miocene when the denudation was less intensive,the unconformity T₂⁰ was formed with mostly 500 to 600 m erosion thickness in the western slope of Diaobei Sag,the northern part of Fuzhou Sag,Yandang Low Bulge,and southern segment of the western slope of Jiaojiang-Lishui Sag.In the Paleocene,rifting and faulting activities initiated in the western depression,forming a dustpan-shaped “eastern faulted and western overlapping” structure;then shifted to east depression (leaving the west part to enter the stage of depression-inversion in the Eocene),forming a “bidirectional faulted” structure in Diaobei Sag.The Oligocene saw the east part also entered the depression-inversion stage but less intensive with the depression gradually turning into the westward overlapping dustpan structure.After the Miocene,the East China Sea Shelf Basin slowly entered the regional subsiding stage from west to east.