琼东南盆地北礁凹陷梅山组顶部丘形反射特征及成因分析

发布时间：2018-05-05 09:39

  本文选题：北礁凹陷 + 梅山组　； 参考：《海洋学报》2017年05期

【摘要】：南海琼东南盆地北礁凹陷中中新统梅山组顶部丘形反射目前引起广泛关注,前人推测为生物礁、重力蠕动与底流叠加成因、等深积丘等。本文通过钻井资料、二维、三维地震资料精细刻画丘形反射(残丘)和丘间水道特征及其成因。残丘及水道在北礁凸起不发育,在边缘斜坡中部和高地较发育,且有向高地两边规模减小趋势,不具对称性,残丘和水道呈平行-亚平行近E-W向展布,局部有合并分叉现象,与北礁凸起走向呈一小角度;丘宽562~1 223m,丘高29~87m,丘长10km左右,存在丘翼削蚀,水道底蚀现象。地震属性分析表明三维工区西南部残丘间水道由砂泥岩互层充填,形成长条形强振幅,而残丘为中-低振幅;地震、钻井资料分析表明丘形反射(残丘)由钙质泥岩和泥岩组成,属于半深海沉积,且残丘内部波阻抗为5.0×10~6~6.5×10~6 kg/m~3·m/s,低于火山岩、灰岩波阻抗,属于砂泥岩地层范畴;根据梅山组下段水道由西向东强振幅变弱、分叉、前积反射和海山附近底流(等深流)沉积剥蚀特征综合判定底流古流向自西向东,根据海山两翼地震反射特征推测底流可追溯至晚中新世早期(11.6Ma BP),综合分析认为,研究区中中新统梅山组丘形反射是晚中新世早期底流切割梅山组地层形成的残丘。
[Abstract]:The mound reflection at the top of Miocene Meishan formation in Beijiao depression, Qiongdongnan Basin, South China Sea, has attracted wide attention. Through drilling data, 2D and 3D seismic data, the characteristics and origin of mound reflection (residual mound) and interdune waterway are described in detail in this paper. The residual hills and waterways are not developed in the uplift of the northern reef, and are relatively developed in the middle of the marginal slope and in the highlands. The scale of the residual hills and waterways decreases towards both sides of the highlands without symmetry. The residual hills and waterways are distributed in a parallel sub-parallel near E-W direction, and there is a phenomenon of amalgamation and bifurcation in some areas. At a small angle to the strike of the North Reef uplift, the width of the mound is 562 ~ 1223m, the height of the mound is 29 ~ 87m, the length of the mound is about 10km, and there exists the phenomenon of clipping of the hill and erosion of the bottom of the waterway. The seismic attribute analysis shows that the channel between the residual hills in the southwest of the three dimensional working area is filled with sand and mudstone interbedded, forming long stripe strong amplitude, while the residual hill is medium to low amplitude. The analysis of drilling data shows that the mound reflection (residual mound) is composed of calcareous mudstone and mudstone, and belongs to semi-deep sea sediment, and the internal wave impedance of residual mound is 5.0 脳 10 ~ (6) ~ (6) 脳 10 ~ (-6) kg/m~3 路m ~ (-1), which is lower than that of volcanic rock and limestone wave impedance, which belongs to the category of sand and mudstone strata. According to the characteristics of weak amplitude from west to east, bifurcation, forward product reflection and denudation of the bottom flow (isodeep current) near the seamounts in the lower reach of Meishan formation, the paleo-flow direction from west to east is determined. Based on the seismic reflection characteristics of the two wings of the seamounts, it is inferred that the bottom flow can be traced back to the late Miocene early Miocene (11.6 Ma) BPU. The comprehensive analysis shows that the mound reflection of the Miocene Meishan formation is the residual mound formed by the late Miocene undercurrent cutting the Meishan formation.
【作者单位】： 西北大学大陆动力学国家重点实验室;
【基金】：国家科技重大专项(2011ZX05025-006-02) 国家自然科学基金(41390451)
【分类号】：P736.1;P618.13
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本文编号：1847187