珠海组—珠江组时期东沙隆起物源提供能力探讨

Capability of Dongsha Massif as Provenance during Zhuhai-Zhujiang Formations

通过对东沙隆起周边晚渐新世—早中新世早期(珠海组—珠江组下段,32~18.5 Ma)时期与早中新世晚期(珠江组上段,18.5~16.5 Ma)地震前积特征、砂岩碎屑组分、重矿物特征、砂体平面展布的研究与对比,认为在晚渐新世—早中新世早期,东沙隆起继承性发育,暴露于水面之上,发育独立的古水流体系,这些水流方向以东沙隆起为中心向西北和西南方发散。同时随着海水的入侵,东沙隆起范围不断缩小,物源提供能力逐渐减弱,到21 Ma时期东沙隆起碎屑物源提供能力丧失;21~18.5 Ma时期,东沙隆起逐渐过渡为碎屑岩与碳酸盐混积,并最终发育碳酸盐,18.5~16.5 Ma时期为东沙隆起区碳酸盐的发育高峰期,可以认为此期仍有碳酸盐物源提供能力;16.5 Ma之后,东沙隆起的生物礁也因淹没死亡,同时古珠江三角洲进积到此,东沙隆起沦为古珠江三角洲的前三角洲—陆棚沉积,彻底丧失物源能力。

Comparing the seismic profiles,detrital material combinations and maturity,heavy mineral characteristics and sand ratio map from up and below the 18.5 Ma,which is the time line between the early and late stage of early Miocene,and stratigraphic boundary of the lower and upper Member of the Zhujiang Formation meaning while,in Dongsha massif,east of the Pearl River Mouth Basin,we can draw the conclusion that before 18.5 Ma,the Dongsha massif was still above the sea level and developed multiple flows radiated from the massif; as the sea-level rising,the massif lowed gradually,detrital materials from the Dongsha massif decreased while carbonate sources occupied,so reef appeared,and it peaked during 18.5 Ma to 16.5 Ma. After 16.5 Ma,the massif immersed as the prodelta of the Paleo-Zhujiang delta which sourced from northwest and prograded to the place,so the Dongsha massif lost the sources capability eventually.