百色盆地古近系高分辨率层序地层学

【作者】 麻建明；

【导师】 王成善； 陈洪德； 施泽进；

【作者基本信息】 成都理工大学 ， 构造地质学， 2005， 博士

【摘要】 本文应用沉积学、构造地质学、盆地分析和高分辨率层序地层学理论,以大量的钻井、露头剖面、测井及地震资料为基础,对百色盆地古近系开展了系统深入的高分辨层序地层研究,取得了如下创新成果和认识: (1) 以中、长期基准面旋回分析为基础,结合界面和部分层序的年龄资料,对百色盆地古近系的地层划分和对比进行了清理,在前人研究的基础上,提出更符合层序划分和沉积充填演化规律的地层划分方案,各组地层的时代归属依次为:六忸组为古新世,洞均组为早始新世,那读组为中—晚始新世,百岗组为渐新世,百岗组之上为伏平组和建都岭组。 (2) 首次以高分辨率层序地层学理论及其技术方法,以沉积相分析为基础,详细研究了古近系的层序地层学特征,主要进展为:①识别出超长期(SLSC旋回)、长期(LSC旋回)、中期(MSC旋回)和短期(SSC旋回)4个级次的基准面旋回层序,确定了中、长期和超长期旋回层序界面、湖泛面在盆地内的等时对比关系、意义和标志;②将百色盆地古近系划分为与地层组相当的4个超长期旋回层序,建立了超长期旋回层序与各期构造活动的关系,认为由构造应力场转换形成的区域性不整合界面,是控制超长期旋回层序发育的关键,因而超长期旋回层序界面可代表不同构造演化阶段的应力场转换面,层序是不同构造演化阶段的产物;③将六忸组划分为3个长期旋回层序(LSC1-LSC3),洞均组划分为1个长期旋回层序(LSC4),那读组划分为3个长期旋回层序(LSC5-LSC7),百岗组划分为3个长期旋回层序(LSC8-LSC10)。确定了长期旋回层序与较大规模湖进—湖退旋回的关系,认为长期旋回层序发育的因素,主要与同一构造应力场周期性构造沉降活动的强弱变化有关,因而长期旋回层序界面可代表同一构造演化阶段中周期性出现的构造变动面;④进一步在六忸组中划分出3个中期旋回层序(MSC1-MSC3),洞均组中划分出2个中期旋回层序(MSC4-MSC5),那读组中划分出12个中期旋回层序(MSC6-MSS17),百岗组中最多划分出7个中期旋回层序(MSC18-MSC24)。中期基准面旋回层序的发育与次一级的湖进—湖退作用和物源供给量、气候变化有关:⑤在收集众多年龄数据的基础上,结合不同级次的基准面旋回沉积演化特征,对超长期、长期、中期和短期旋回层序的时限进行了界定,认为超长期旋回层序的时限为10～13Ma。长期旋回层序的时限为3～5Ma。中期旋回层序的时限为0.8～2.5Ma。短期旋回层序相当于准层序或最小成因地层单元,时限为数万年级。上述不同级次的基准面旋回时限界定,为提高等时地层单元的时间对比精度和分辨率奠定了基础。 (3) 剖析了短期基准面旋回层序的结构类型,识别出向上“变深”的非对称型(A)、向上变浅的非对称型(B)和向上变深后复变浅的对称型(C)3种主要结构类型,以及分别发育于低可容纳空间和高可容纳空间中的7种亚类型:低可容纳空间向上“变深”的非更多还原

【Abstract】 Sedimentolgy, tectonics, basin analyses and high-resolution sequence stratigraphy are applied in this paper. On basis of many data of drillings, outcrops, observation well and seism,we study paleogene sequence by the high- resolution sequence stratigraphy in the Bai Se basin. Some new opinions and results obtained as follow:(1) Basing on the mid-term and long-term datum level analysis and linking data of the interface and the age of some squences, Paleogene sequence delimiting and contrast is verified in the Bai Se basin. On basis of predecessor study, stratigraphic delimiting which accord with sequence division and evolution rule of sedimentary filling is put forward. Each formation age assignment in turn: Liu Niu formation belonging to Paleocene, Dong Jun formation belonging to early Eocene, Na Du formation belonging to mid-late Eocene, Bai Gang formation belonging to Oligocene, Fu Ping and Jian Dou Ling formation overlaying Bai Gang formation.(2) On basis of sedimentary facies analysis, Paleogene sequence stratigraphic feature is particularly studied by theories and methods of high-resolution sequence stratigraphy which is used firstly. Main evolvations: ①identified four grades datum level cycle sequence, such as super-long term (SLSC cycle), long term(LSC cycle), mid-term(MSC cycle) and short term (SSC cycle). Mid-term, long term and super-long term cycle sequence interface and isochronic correlation,significance and sign of flooding surface in the basin are made certain. ② Paleogene is divided 4 super-long term cycle sequences which correspond stratigraphic formations in the Bai Se basin. Establishing relation between super-long term cycle sequence and every phase tectonic activity, unconformable contactformed by tectonic stress field transition is key which control super-long term cycle sequence growth. So super-long term cycle interface denotes stress field transition of different tectonic evolution phase. Namely equence is result of different tectonic evolution phase;③Liu Niu formation is divided into 3 long term cycle sequences(LSCl-LSC3). Dong Jun formation dividing 1 long term cycle sequences(LSC4), Na Du formation dividing 3 long term cycle sequences(LSC5-LSC7), Bai Gang formation dividing 3 long term cycle sequences(LSC8-LSC10). Relation between long term cycle and lacustrine transgressive regressive cycle is confirmed. Factors of long term cycle growth is connected with variety of the periodical tectonic subsidence activity in the same stress field. Thus long term cycle interface denotes tectonic change surface of periodical tectonic surface in the same tectonic evolution phase; ④Liu Niu formation is farther divided into 3 mid-term cycle(MSCl), 2 mid-term cycle Dong Jun formation (MSC4-MSC5), 12 mid-term cycle in Na Du(MSC6-MSC17), 7 mid-term cycle in Na Du(MSC18-MSC24). Secondary lacustrine transgressive regressive action of mid-term datum level cycle bears on provenance supply and climate change; ⑤On basis of many age data and sedimentary evolution feature of different grade datum level cycle, the age of super-long term, mid-term and short term cycle areconfirmed. Super-long term age is 10-13Ma; long term cycle age is 3-5Ma; mid-term cycle age is 0.8-2.5Ma; short term cycle which correspond parasequence or least stratigraphic unit is tens thousand. Age confirmation of different grades datum level cycle is basis for age contrast precision and resolution of isochronic stratigraphic unit.(3) Analyzing structure type of short term datum level cycle, the authors identified three main types which are up-deeping asymmetry(A), up-shallowing asymmetry(B) and symmetry from up-deeping to up-shallowing(C). Further in the light of the high or low accommodation, seven subtypes of structure are distinguished and they are up-deeping asymmetry of low accommodation (Type Al) or high accommodation (Type A2), up-shallowing asymmetry of low accommodation (Type Bl) or high accommodation (Type B2), complete-nearly complete symmetry (Type Cl), incomplete symmetry with majority of uprising semi-cycle (Type C2) or subsiding semi-cycle (Type C3). It is mainly discussed that sedimentary kinetic feature during every type short term cycle stratigraphy and stacking patterns of mid-short term datum level cycle during mid-term cycle.(4) According to above research, in 2 secondary pull-apart basin, Nadu and Baigang formation of I and II grade tectonic units makes regional correlation by means of super-long term cycle as frame, long term cycle as grain and mid-term cycle as isochronic stratigraphyic unit. The author establish high-resolution sequence stratigraphy of the I grade tectonic unit and discuss datum level cycle structure type, stacking patterns, distribution rule of the different tectonic unit in stratigraphic frame.(5) Applying research achievement of high-resolution sequence stratigraphy, basing on the choice sequence interface SB5,SB6,SB7,SB8 as isochronic contrast sign, the same sequence thickness and facies interpretation of hundreds drilling well as control point(facies type of control point decided by optimum method), LSC5 uprising semi-cycle, LSC6 uprising semi-cycle, LSC7 subsiding semi-cycle (Nayi up subsegment), LSC8 uprising semi-cycle (low Bai three segment) as mapping unit, we selectively make four sequence lithofacies-paleographic map which objectively reflect paleogene lithofacies-paleogeographic frame, development and evolution in the Baise basin.(6) On basis of the study of the sedimentary system, sequence stratigraphy and lithofacies-paleogeography, linking paleogene feature of tectonic stress field and tectonic type in the Baise basin, Baise basin is defined small strike-slip pull-apart basin which develops on the young craton folded basement in the Hercynian-Indosinian. Form, development and evolution history of Basin divide 3 periods and 7 phases: (Drelief basin period of the LSC1-LSC3 period(Liuniu sedimentary period); (2)LSC4(Dongjun formation period) early rift-subsidence phase, LSC5-LSC6(Nadu early-middle period—E2n3-E2n2) strong rift-subsidence phase, and LSC7(Nadu late period—E2n’) stable rift-subsidence phase; (3)LSC8(Baigang early period— E3b3) early depression phase, LSC9(Baigang middle—E3b2) strong depression phase and更多还原