多幕裂陷盆地构造-沉积响应及陆丰凹陷实例分析

doi:10.13745/j.esf.sf.2020.5.9

摘要/Abstract

摘要：

裂陷盆地常常经历了多层次、多周期的幕式沉降过程。若盆地的演化包括了两幕或以上的裂陷旋回,则称之为多幕裂陷盆地。多幕裂陷盆地构造演化特别是复杂的断裂发育特征及其活动方式引起国际地质学家广泛的关注。多幕次裂陷作用下断裂活动方式的转型,必然会导致物源水系、沉积物入口位置及砂体分散方式的系统性差异。前人研究表明,在第一幕裂陷或者单幕裂陷盆地中断裂经常会发生分段联接。在盆地演化的早期各个洼陷较为分散和孤立,主要以陡坡带和缓坡带水系供源为主,而在断裂发生连锁之后,轴向水系供源体系则开始占据主导。相比较第一幕裂陷,第二幕裂陷作用下盆内断裂活动方式多变化,其沉积响应十分复杂。珠江口盆地陆丰凹陷始新世发育两幕裂陷(Ⅰ幕和Ⅱ幕),区域构造应力场方向偏转可能诱导了主干断层的差异活动,致使裂陷中心从南向北发生迁移。研究表明陆丰凹陷两幕次裂陷旋回的构造-沉积响应差异明显:(1)裂陷Ⅰ幕初始断陷阶段断层位移量相对较小,湖盆表现为“浅盆”特征,而裂陷Ⅱ幕早期阶段快速形成规模大、活动性强的边界断层,湖盆则快速进入深湖环境;(2)裂陷Ⅰ幕初始断陷阶段厚度中心小且较为分散,而裂陷Ⅱ幕早期阶段厚度中心规模大,较为统一;(3)裂陷Ⅰ幕初始-强烈断陷阶段以陡坡带、转换带和缓坡带侧向水系供源为主,而裂陷Ⅱ幕早期轴向水系占据主导。在伸展应力方向偏转的多幕裂谷盆地,晚期裂陷幕往往以特定的边界断层迅速生长和复活为特征。近似垂直于新的应力场方向的先存断层则优先活动,在该地区的位移量快速达到最大,这促进了大型轴向供源体系的形成;而未复活断层控制的地区构造沉降弱,继承了早期裂陷结束时长轴水系供源的格局,具有整体“富砂”的沉积特征。以上认识对珠江口盆地及其他多幕裂陷盆地演化分析及砂体预测具有重要的理论价值。

关键词: 多幕裂陷, 断层活动, 沉积物分散, 始新统, 陆丰凹陷, 珠江口盆地

Abstract:

Numerous rift basins worldwide were shown to experience two or more distinct extensional phases, and are referred to as multiphase rift basins. Natural observations and physical results revealed distinctive fault behaviors between the first (RP1) and second (RP2) rift phase in multiphase rifts. The transition between fault growth and reactivation in separate rift phases would inevitably lead to changes in drainage catchments, sediment entrance and sandstones dispersal pathways. The evolution of multiphase rift basins, especially the fault array evolution and displacement patterns, have attracted the attentions from numerous geologists worldwide. Typically, RP1 or single rift cycle involves progressive evolution, featuring isolated faults, fault interaction and linkage, and through-going faulting during the climax stages, followed by a final fault-death stage. In proposed genetic models, the basin is mostly relatively scatted and isolated in the early stage dominated by transverse-sourced systems, then axially-source system becomes facilitated in the fault linkage stage and towards the end of the rifting process. Compared to RP1, the rift-related faulting and basin-infill patterns during RP2 are unclear and currently an international hot topic. Our case study was in the Lufeng Depression located in the northern Pearl River Mouth basin of the South China Sea. The Lufeng Depression is a two-phase rift basin. The directional rotation of the regional tectonic stress field might have induced the differential activities of rift-related faults, resulted in northward migration of the subsidence center. The depositional responses to the tectonic activities during RP2 were in marked contrast to those during RP1. Firstly, the initial stage of RP1 was commonly low-displacement with a shallow lake setting, while the rapidly reactivation of selected master faults resulted in a high tectonic subsidence rate associated with a dominant deep lake setting during the early stage of RP2. Secondly, the initial basins of RP1 were usually small-sized with isolated depocenters, but the depocenters were generally large and uniform during the early stage of RP2. Thirdly, the initial and climax rift stages of RP1 were dominated by transverse drainages, whereas the rapid reactivation of selected faults tended to establish the large axially-sourced drainage catchments during RP2. Consequently, a tectono-sedimentary motif for the multiphase rift basin is proposed. It suggests that those pre-existing faults that are nearly perpendicular to the new extensional direction are highly susceptible to immediate reactivation and can propagate rapidly to their full displacements. The RP2 basins therefore can be considered as 1) sustained axially-sourced depositional systems in the inactive fault controlled areas, or 2) facilitating newly captured axially-dominated systems in the rapidly reactivating fault areas. This study may have significant implications for fault depositional evaluation and sandstone prediction in the Pearl River Mouth basin or other multiphase rifts worldwide.

Key words: multiphase rifting, fault activity, sediment dispersal pattern, Eocene, Lufeng Depression, Pearl River Mouth Basin

中图分类号:

葛家旺, 朱筱敏, 雷永昌, 于福生. 多幕裂陷盆地构造-沉积响应及陆丰凹陷实例分析[J]. 地学前缘, 2021, 28(1): 77-89.

GE Jiawang, ZHU Xiaomin, LEI Yongchang, YU Fusheng. Tectono-sedimentary development of multiphase rift basins: An example of the Lufeng Depression[J]. Earth Science Frontiers, 2021, 28(1): 77-89.

图/表 10

图2 裂陷盆地三种断层生长方式与盆地演化模式(引自文献[17])

Fig.2 Conceptional models of the three fault growth styles and basin geometric evolution in rift basins. Adapted from [17].

图1 裂谷盆地断层分段生长连接与位移变化(引自文献[20])

Fig.1 Conceptional models of fault growth, linkage and displacement during different evlutionary stages in rift basins. Adapted from [20].

图3 塔木察格盆地塔南凹陷断裂早期联接及沉积分散方式响应(引自文献[23]) a—初始的孤立断层阶段:断裂规模小位移量低,以孤立、分割的小断陷群为特征;由于高低起伏的先存火山岩基底,缺失先存成熟的水系,盆地以短程水系供给为主,形成数量众多且规模小的冲积扇/扇三角洲沉积体系。b—断裂早期快速联接阶段:断裂快速拓展交互联接,形成规模较大的低坡降走向斜坡且缓坡带得到建设延长,发育大套包括转换带水系(②)和缓坡带水系(③)供给的长距离搬运富砂沉积体系;陡坡带(①)及轴向物源体系(④)相对较少。

Fig.3 Early leakage of the fault arrays and sedimentary dispersal response in the Tanan Depression, Tamtsag Basin. Adapted from [23].

图4 两幕裂陷旋回中断裂生长演化及相互作用模式图(引自文献[12])

Fig.4 Fault growth patterns and linkage models for two-phase rift basins. Adapted from [12].

图5 珠江口盆地陆丰凹陷始新世构造地层特征

Fig.5 The Eocene tectono-stratigraphy of the Lufeng Depression in the Pearl River Mouth Basin. The study interval includes the Wenchang and Enping Formations.

图6 珠江口盆地陆丰凹陷主干断层活动性统计断层编号参见图8。

Fig.6 Fault displacement of six basin boundary faults in the Lufeng Depression

图7 珠江口盆地陆丰凹陷6个洼陷沉降速率与沉降曲线图(洼陷位置见图5b)

Fig.7 Subsidence rates and curves of six sags in the Lufeng Depression (See Fig.5b for sag locations)

图8 陆丰凹陷始新世盆地裂陷Ⅰ幕(a)、裂陷Ⅱ幕(b)伸展方向及厚度分布

Fig.8 Extensional stress field and depocenter distribution variations during RP1 (a) and RP2 (b) in the Lufeng Depression

图9 珠江口盆地陆丰凹陷裂陷Ⅰ幕构造-沉积演化模式图(引自文献[30]) a—初始断陷期(WSQ1-2);b—强烈断陷期(WSQ3-4);c—弱断陷期(WSQ5)。

Fig.9 Tectono-sedimentary evolution motifs during RP1 in the Lufeng Depression, Pearl River Mouth Basin. Adapted from [30].

图10 珠江口盆地陆丰凹陷裂陷Ⅱ幕构造-沉积演化模式图

Fig.10 Tectono-sedimentary evolution motifs during RP2 in the Lufeng Depression, Pearl River Mouth Basin

参考文献 35

[1]	RAVNAS R, STEEL R J. Architecture of marine rift basin successions[J]. AAPG Bulletin, 1998, 82:110-146.
[2]	HENSTRA G A, ROTEVATN A, GAWTHORPE R L, et al. Evolution of a major segmented normal fault during multiphase rifting: the origin of plan-view zigzag geometry[J]. Journal of Structural Geology, 2015, 74:45-63. DOI URL
[3]	MORLEY C K, HARANYA C, PHOOSONGSEE W, et al. Activation of rift oblique and rift parallel pre-existing fabrics during extension and their effect on deformation style: examples from the rifts of Thailand[J]. Journal of Structural Geology, 2004, 26:1803-1829. DOI URL
[4]	DENG C, FOSSEN H, GAWTHORPE R L, et al. Influence of fault reactivation during multiphase rifting: the Oseberg area, northern North Sea rift[J]. Marine and Petroleum Geology, 2017, 86:1252-1272. DOI URL
[5]	焦养泉, 周海民, 刘少峰, 等. 断陷盆地多层次幕式裂陷作用与沉积响应: 以南堡老第三纪断陷盆地为例[J]. 地球科学: 中国地质大学学报, 1996, 21(6):633-636.
[6]	林畅松. 盆地沉积动力学: 研究现状及未来发展趋势[J]. 石油与天然气地质, 2019, 40(2):685-700.
[7]	王维, 叶加仁, 杨香华, 等. 珠江口盆地惠州凹陷古近纪多幕裂陷旋回的沉积物源响应[J]. 地球科学: 中国地质大学学报, 2015, 40(6):1061-1071.
[8]	解习农, 程守田, 陆永潮. 陆相盆地幕式构造旋回与层序构成[J]. 地球科学: 中国地质大学学报, 1996, 21(1):27-33.
[9]	严德天, 王华, 王清晨. 中国东部第三系典型断陷盆地幕式构造旋回及层序地层特征[J]. 石油学报, 2008, 29(2):185-190.
[10]	林畅松, 刘景彦, 张英志, 等. 构造活动盆地的层序地层与构造地层分析: 以中国中、新生代构造活动湖盆分析为例[J]. 地学前缘, 2005, 12(4):365-374.
[11]	HENZA A A, WITHJACK M O, SCHLISCHE R W. How do the properties of a pre-existing normal-fault population influence fault development during a subsequent phase of extension?[J]. Journal of Structural Geology, 2011, 33:1312-1324. DOI URL
[12]	WHIPP P S, JACKSON C A L, GAWTHORPE R L, et al. Normal fault array evolution above a reactivated rift fabric: a subsurface example from the northern Horda Platform, Norwegian North Sea[J]. Basin Research, 2014, 26:523-549. DOI URL
[13]	HENSTRA G A, GAWTHORPE R L, HELLAND-HANSEN W, et al. Depositional systems in multiphase rifts: seismic case study from the Lofoten margin, Norway[J]. Basin Research, 2017, 29:447-469. DOI URL
[14]	BELL R E, JACKSON C AL, WHIPP P S, et al. Strain migration during multiphase extension: observations from the northern North Sea[J]. Tectonics, 2014, 33:1936-1963. DOI URL
[15]	DUFFY O B, BELL R E, JACKSON C A L, et al. Fault growth and interactions in a multiphase rift fault network: Horda Platform, Norwegian North Sea[J]. Journal of Structural Geology, 2015, 80:99-119. DOI URL
[16]	NOLL C A, HALL M. Normal fault growth and its function on the control of sedimentation during basin formation: a case study from field exposures of the Upper Cambrian Owen Conglomerate, West Coast Range, western Tasmania, Australia[J]. AAPG Bulletin, 2006, 90:1609-1630. DOI URL
[17]	MORLEY C K. Evolution of large normal faults: evidence from seismic reflection data[J]. AAPG Bulletin, 2002, 86:961-978.
[18]	MCLEOD A E, UNDERHILL J R, DAVIES S J, et al. The influence of fault array evolution on synrift sedimentation patterns: controls on deposition in the Strathspey-Brent-Statfjord half graben, northern North Sea[J]. AAPG Bulletin, 2002, 86:1061-1093.
[19]	DAWERS N H, ANDERS M H. Displacement-length scaling and fault linkage[J]. Journal of Structural Geology, 1995, 17:607-614. DOI URL
[20]	GAWTHORPE R L, LEEDER M R. Tectono-sedimentary evolution of active extensional basins[J]. Basin Research, 2000, 12:195-218. DOI URL
[21]	SCHLISCHE R W, ANDERS M H. Stratigraphic effects and tectonic implications of the growth of normal faults and extensional basins[M]//BERATAN K K, Reconstructing the structural history of basin and range extension using sedimentology and stratigraphy. Boulder: GSA, 1996: 183-203.
[22]	PROSSER S. Rift-related depositional systems and their seismic expression[M]//WILLIAMS G D, DOBB A. Tectonics and seismic sequence stratigraphy. London: Geological Society, 1993: 35-66.
[23]	GE J W, ZHU X M, WANG R, et al. Tectono-sedimentary evolution and hydrocarbon reservoirs in the Early Cretaceous Tanan Depression, Tamtsag Basin, Mongolia[J]. Marine and Petroleum Geology, 2018, 94:43-64. DOI URL
[24]	GUPTA S, UNDERHILL J R, SHARP I R, et al. Role of fault interactions in controlling synrift sediment dispersal patterns: Miocene, Abu Alaqa Group, Suez Rift, Sinai, Egypt[J]. Basin Research, 1999, 11:167-189. DOI URL
[25]	DAVIES S J, DAWERS N H, MCLEOD A E, et al. The structural and sedimentological evolution of early synrift successions: the Middle Jurassic Tarbert Formation, North Sea[J]. Basin Research, 2000, 12:343-365. DOI URL
[26]	胡阳, 吴智平, 钟志洪, 等. 珠江口盆地珠一坳陷始新世中-晚期构造变革特征及成因[J]. 石油与天然气地质, 2016, 37(5):779-785.
[27]	邓棚. 南海北部陆缘古近纪多幕裂陷作用属性及转换: 以珠江口盆地珠一坳陷为例[D]. 武汉:中国地质大学(武汉), 2018: 17-38.
[28]	吴冬, 朱筱敏, 李志, 等. 苏丹Muglad盆地Fula凹陷白垩纪断陷期沉积模式[J]. 石油勘探与开发, 2015, 42(3):319-327.
[29]	ZHOU D, RU K, CHEN H Z. Kinematics of Cenozoic extension on the South China Sea continental margin and its implications for the tectonic evolution of the region[J]. Tectonophysics, 1995, 251:161-177. DOI URL
[30]	葛家旺, 朱筱敏, 张向涛, 等. 珠江口盆地陆丰凹陷文昌组构造-沉积演化模式[J]. 中国矿业大学学报, 2018, 47(2):308-322.
[31]	葛家旺, 朱筱敏, 吴陈冰洁, 等. 辫状河三角洲沉积特征及成因差异: 以珠江口盆地陆丰凹陷恩平组为例[J]. 石油学报, 2019, 40(增刊1):139-152.
[32]	米立军, 张向涛, 汪旭东, 等. 陆丰凹陷古近系构造-沉积差异性及其对油气成藏的控制[J]. 中国海上油气, 2018, 30(5):1-9.
[33]	GE J W, ZHU X M, ZHANG X T, et al. Tectono-stratigraphic evolution and hydrocarbon exploration in the Eocene Southern Lufeng Depression, Pearl River Mouth Basin, South China Sea[J]. Australian Journal of Earth Science, 2017, 64:931-956. DOI URL
[34]	RU K, PIGOTT J D. Episodic rifting and subsidence in the South China Sea[J]. AAPG Bulletin, 1986, 70:1136-1155.
[35]	PIGOTT J D, RU K. Basin superposition on the northern margin of the South China Sea[J]. Tectonophysics, 1994, 235:27-50. DOI URL