HIGH-PRECISION SEQUENCE STRATIGRAPHY IN QIONGDONGNAN BASIN
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摘要: 运用当代层序地层学的原理和方法, 综合分析了地震、测井、岩心等资料, 发现琼东南盆地经历了早期裂陷和晚期坳陷两大发育历程, 相应划分出TejasA和TejasB两个超层序组; 与盆地非海相、海相过渡相、生长断层、缓坡和被动大陆边缘背景演化阶段相匹配, 形成了5个超层序.以不整合及其与之可以对比的整合为三级层序边界, 识别出19个层序, 含5 7个体系域、5 4个以上准层序组、196个以上准层序.在盆地的不同演化阶段, 沉积层序的不同点主要在于低水位体系域包含的沉积体系不同.在恢复古地理环境的基础上, 提炼出有关沉积层序模式.根据可容纳空间分析, 编制了本区海平面升降曲线, 发现陵水中期、梅山早期和莺歌海早期三次大的海泛与全球变化完全合拍.在纵向上, 海进体系域至密集段生烃潜力最强, 空间上以外陆架-大陆坡最好, 其次为滨沼或海陆过渡相.指出了陆架坡折附近的低水位楔和斜坡扇是值得注意的隐蔽圈闭勘探目标.Abstract: The principle of and method for the contemporary sequence stratigraphy are both employed to analyze comprehensively the references on seismology, logging, and cores. This comprehensive analysis shows that the Qiongdongnan basin may have experienced two major growth stages: the early rift stage and the late depression stage, corresponding to the two supersequence sets: Tejas A and Tejas B. In addition, five supersequences were formed that corresponded to the five evolutionary stages in the basin: nonmarine facies, marine transitional facies, growth fault, ramp, and passive continental setting. The unconformity and its counterpart, the conformity, both serving as the third-order sequence boundaries are employed to identify 19 sequences containing 57 systems tracts, over 54 parasequence sets and over 196 parasequences. The major differences between different evolutionary stages and between different sedimentary sequences in the basin are both attributed to the different sedimentary system contained in the lowstand systems tract. On the basis of the reconstruction of the paleo-environment settings, have been established the models of depositional sequences. The accomodation analysis is applied to the compilation of the sea-level change curve of the Qiongdongnan basin, resulting in the discovery of the perfect matching between the three major marine floods that occurred in the middle Lingshui, early Meishan and early Yinggehai stages, and the corresponding globe changes. The best potential hydrocarbon resources are located vertically in the section between the marine transgressive systems tract and the condensed section, but laterally between the outer-shelf to the continental slope. The next best potential hydrocarbon resources are located in the littoral-aquamarsh deposits or in the marine-continental transitional facies. This paper suggests that the lowstand wedge and the slope fan near the continental-shelf slope break should serve as the petroleum exploration target of the hidden traps worthy of attention.
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图 1 松涛半地堑式凹陷中部超层序分析
Fig. 1. Analysis on supersequences in the middle Songtao depression with half-graben texture
图 2 琼东南盆地第三纪相对海平面变化曲线及其与层序的对比
Fig. 2. Relative sea-level change curves and correlation with sequences of Tertiary in Qiongdongnan basin
图 3 宝岛凹陷中部三级层序地层分析
Fig. 3. Analysis of third-order sequences in the middle Baodao depression
图 4 松涛凹陷西部层序9下部边界处的下切谷和削截反射结构
Fig. 4. Incised valley and truncation on the sequence boundary 9 in the western Songtao depression
图 5 琼东南盆地裂陷作用阶段低水位盆底扇沉积模式
Fig. 5. Depositional model of lowstand basin-floor fan during rift-stage in Qiongdongnan basin
图 6 琼东南盆地裂陷作用阶段低水位斜坡扇沉积模式
Fig. 6. Depositional model of lowstand slope fan during rift-stage in Qiongdongnan basin
图 7 琼东南盆地裂陷作用阶段低水位前积楔沉积模式
Fig. 7. Depositional model of lowstand prograding wedge during rift-stage in Qiongdongnan basin
图 8 琼东南盆地裂陷作用阶段海进体系域沉积模式
Fig. 8. Depositional model of transgressive systems tract during rift-stage in Qiongdongnan basin
图 9 琼东南盆地裂陷作用阶段高水位体系域沉积模式
Fig. 9. Depositional model of highstand systems tract during rift-stage in Qiongdongnan basin
图 10 琼东南盆地裂陷作用阶段低水位盆底扇的地震反射特征
Fig. 10. Seismic reflectors of lowstand fan formed in post-rift stage in Qiongdongnan basin
图 11 琼东南盆地裂陷作用阶段低水位斜坡扇的地震反射特征
Fig. 11. Seismic reflectors of lowstand slope fan formed in post-rift in Qiongdongnan basin
图 12 琼东南盆地裂陷作用阶段低水位前积楔的地震反射特征
Fig. 12. Seismic reflectors of lowstand prograding wedge formed in post-rift in Qiongdongnan basin
图 13 琼东南盆地裂陷作用阶段低水位期海底峡谷的地震反射特征
Fig. 13. Seismic reflectors of lowstand submarine canyon formed in post-rift in Qiongdongnan basin
表 1 琼东南盆地层序地层系统
Table 1. Sequence stratigraphic systems of Qiongdongnan basin
表 2 琼东南盆地地震层序界面识别标志
Table 2. Identifying characteristics of seismic sequence boundaries in Qiongdongnan basin
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