珠江口盆地番禺低隆起PY24断层断裂特征及其对沉积作用的影响

通过对PY24断层附近的钻测井及二、三维地震资料研究,运用断层活动速率法发现PY24同沉积断层在珠江组上段、韩江组和粤海地层沉积时期活动强,在珠江组下段地层沉积时期活动弱,整体上断层活动表现出"阵发性"。断层的"阵发性"活动对沉积作用的影响类似于阀门对流体的控制,当断层活动弱时,"阀门"开启,沉积物不断向凹陷沉积,断层上下盘地层厚度差异小,沉积相带连续并延伸远;当断层活动强时,"阀门"关闭,沉积物大部分沉积在下降盘产生的可容纳空间内,断层上下盘地层厚度差异大,沉积相带变化明显,断层的活动对沉积的阻挡作用显著。目前大多数的研究停留在同向同沉积断层对沉积作用的影响上,而缺少对反向同沉积断层的探讨。本文为研究反向同沉积断层对沉积作用的影响提供了一个良好的例证。

PY24 FAULT THROUGH PANYU LOW-UPLIFT OF PEARL RIVER MOUTH BASIN: CHARACTERISTICS AND IMPACT ON SEDIMENTATION

The activity ratio of PY24 fault was studied with logging data and 2D and 3D seismic data.It was found that the PY24 fault was very active during the depositional periods of upper Zhujiang Formation,Hanjiang Formation and Yuehai Formation,but silent during the depositional period of lower Zhujiang Formation.In general,the activity of the PY24 fault was intermittent.Its way to affect deposition was similar to the valve for fluid control.When the fault was weak in activity,like an opening valve,deposition continued in the sag,the thickness difference between hanging wall and footwall was small,and the distribution of facies belts was continuous and extensive.By contrast,when the fault was strong in activity,like a closed valve,most of sediments deposited in the accommodation space produced by the moving of footwall,the thickness difference between hanging wall and footwall was large,and facies change was drastic.The fault activity obviously blocked the progradation of coarse-grained sediments.So far most of studies have been focused on the affection of syndepositional concordant normal fault on sedimentation,but lack of the studies on synsedimentary antithetic normal fault.This study provided a case for syndepositional antithetic normal fault and its affect on sedimentation.