Sequence architecture and depositional evolution in Lufeng Depression, Pearl River Mouth Basin, South China Sea Part B: The shore deposits of Zhuhai Formation

Abstract

The Zhuhai Formation in Lufeng Depression is mainly deposited during a depression stage. In this paper, we employ cores, wireline logs, and seismic reflections to reveal sequence architecture and depositional evolution in target intervals. The results indicated that one second‐order sequence and two third‐order sequences were identified and sequence stratigraphic framework was established. The second‐order sequence was developed in response to base‐level falling, while third‐order sequences were mainly formed during base‐level rising. In addition, each third‐order sequence did not change too much in thickness. Then the shore deposits (shoreface and foreshore) were delineated, and the depositional characteristics were described within the framework with the help of related data. The shoreface and foreshore deposits within the sequence stratigraphic framework varied significantly in stacking patterns of wireline logs and cores. Based on comprehensive analysis, it can be concluded that base‐level changes played an important role in controlling sequence architecture. And lacustrine fluctuations derived from accommodation space changes exerted an essential effect on depositional evolution. This study provides significant insights into revealing the sequence architecture and depositional evolution and discussing hydrocarbon potential in the transition stage in the Zhuhai Formation.

Sequence architecture and depositional evolution of the late Palaeogene in southwestern slope of Lufeng Depression, Pearl River Mouth Basin: Responses to tectonic processes and base‐level changes

“…Previous studies have demonstrated that there are several classification schemes for the late Palaeogene depositional sequences due to geological and geophysical datasets limitations (Ge, Zhu, Li, et al, ; Ge, Zhu, Zhang, et al, ; Jiao et al, ; Tao et al, ; Z. H. Wang et al, ;Xia, Dong, et al, ; Xia, Liu, et al, ). Among all these classification schemes, it can be generally summarized into two schemes.…”

“…Among all these classification schemes, it can be generally summarized into two schemes. The depositional sequence is conducted based on the differences in thin sections, cores, wireline logs, and seismic sections in some researches (Jiao et al, ; Tao et al, ; Z. H. Wang et al, ; Xia, Dong, et al, ; Xia, Liu, et al, ). In other researches, it is classified according to the variations in stratal architecture (unconformity and correlative conformity, fault throw, and strata thickness; Ge, Zhu, Li, et al, ; Ge, Zhu, Zhang, et al, ).…”

“…In other researches, it is classified according to the variations in stratal architecture (unconformity and correlative conformity, fault throw, and strata thickness; Ge, Zhu, Li, et al, ; Ge, Zhu, Zhang, et al, ). In this paper, it integrates 3D high‐resolution merging seismic data which covers the whole study area (Xia, Dong, et al, ; Xia, Liu, et al, ) and well‐tie correlations passing through wells which come across the key structural units, and cores which are limitedly distributed to propose a classification scheme for the late Palaeogene depositional sequence. The results indicate that the boundary of composite sequences can be traced and correlated through the whole study area while sequences can mainly be traced in the deep depression and upper strata (Figures and ).…”

“…The ascending and descending cycles are consistent with base‐level rising and falling to some extent. Especially, the majority of sequence boundaries including composite sequences and sequences turn out to be base level‐falling (Figure , Xia, Dong, et al, ; Xia, Liu, et al, ) because the tectonic movements tend to be gentle from Enping Formation to Zhuhai Formation. It shares some similarities with other similar basins.…”

“…The Pearl River Mouth Basin (PRMB) is a Cenozoic rift basin that developed on the northern passive continental margin of the South China Sea (Figure a). The southwestern slope of Lufeng Depression (Figure b), where significant hydrocarbon discoveries have been found in the deep target interval (the Palaeogene) proves to be the most potential oil and gas reserves for the coming future in the Pearl River Mouth Basin (Luo et al, , ; Z. H. Wang, Guo, Liu, Jiao, & Yu, ; Xia, Dong, et al, ; Xia, Liu, et al, ; K. P. Yu & Ding, ; Q. Zhang, Lv, et al, ; X. T. Zhang, Wang, et al, ). During the past few decades, researches on the fault modelling and depositional characteristics of various geological times in the study area have been carried out and fruitful results have been achieved (Ge, Zhu, Li, et al, ; Ge, Zhu, Zhang, et al, ; Jiao et al, ; Wan et al, ; F. S. Yu, Koyi, & Zhang, ).…”