珠江口盆地恩平13-14洼文昌期构造转换及其对沉积充填的控制作用

Tectonic transformation in Wenchang period of Enping 13-14 sub sag,Pearl River Mouth Basin and its controlling effect on sedimentary filling

恩平13-14洼为珠三坳陷最东部的小洼陷,靠近阳江—一统走滑断裂,文昌期构造转换对沉积充填控制作用明显。在对钻井和地震资料分析的基础上,认为文昌组发育扇三角洲、辫状河三角洲、湖泊相的滨浅湖和半深湖-深湖亚相,沉积过程以轴向物源为主。区域伸展方向的旋转和阳江—一统走滑断裂带的活动,导致了恩平13-14洼从早文昌到晚文昌沉积时期,断裂体系、沉降中心沿控盆断裂向NE向迁移,整体上从恩平13洼迁移到恩平14洼,沉积体系从东部为主转换为西部为主。两洼陷对向叠覆的中心部位可能存在恩平期岩浆活动,识别发现岩浆活动影响范围较小,仅影响井旁地震相的识别。

Enping 13-14 sub sag is the easternmost small sub sag in the ZhuⅢdepression,which is close to the Yangjiang-Yitong strike-slip fault.The tectonic transformation in the Wenchang period has an obvious controlling effect on sedimentary filling.Based on the analysis of drilling and seismic data,it is considered that fan delta,braided river delta,shallow lake,and semi-deep lake-deep lake subfacies are developed in the Wenchang Formation.The sedimentary process is dominated by axial provenance.The rotation of the extension direction of the region and the activity of the Yangjiang-Yitong strike-slip fault zone led to the migration of the fault system and the subsidence center in the Enping 13-14 sub sag along the strike of the basin-controlling fault to the northeast from the early Wenchang to late Wenchang sedimentary period.Overall,the migration was from Enping 13 sub sag to Enping 14 sub sag,and the sedimentary system changed from the east to the west.There may be magmatic activities during the Enping period in the central part of the two sub sags.It is found that the influence range of magmatic activities is small,which only affects the identification of seismic facies near the well.