Neotectonics of the Eastern Margin of the Tibetan Plateau: New Geological Evidence for the Change from Early Pleistocene Transpression to Late Pleistocene-Holocene Strike-slip Faulting

We present in this paper some new evidence for the change during the Quaternary in kinematics of faults cutting the eastern margin of the Tibetan Plateau. It shows that significant shortening deformation occurred during the Early Pleistocene, evidenced by eastward thrusting of Mesozoic carbonates on the Pliocene lacustrine deposits along the Minjiang upstream fault zone and by development of the transpressional ridges of basement rocks along the Anninghe river valley. The Middle Pleistocene seems to be a relaxant stage with local development of the intra-mountain basins particularly prominent along the Minjiang Upstream and along the southern segment of the Anninghe River Valley. This relaxation may have been duo to a local collapse of the thickened crust attained during the late Neogene to early Pleistocene across this marginal zone. Fault kinematics has been changed since the late Pleistocene, and was predominated by reverse sinistral strike-slip along the Minshan Uplift, reverse dextral strike-slip on the Longmenshan fault zone and pure sinistral strike-slip on the Anninghe fault. This change in fault kinematics during the Quaternary allows a better understanding of the mechanism by which the marginal ranges of the plateau has been built through episodic activities.

New Discovery of Holocene Activity along the Weixi-Qiaohou Fault in Southeastern Margin of the Tibetan Plateau and its Neotectonic Significance

Objective The lateral extrusion eastward of the Tibetan Plateau leads to the formation of the Sichuan–Yunnan block, which is the most representative active block in the southeastern margin of the Tibetan Plateau, characterized by strong and frequent seismicity(Li Ping et al., 1975; Zhang Peizhen et al., 2003; Li Yong et al., 2017). Its eastern boundary is composed of sinistral faults including the Xianshuihe, Xiaojiang faults, etc., and the western

A quantitative research for present-time crustal motion in Fujian Province, China and its marginal sea── Synthetical analysis of GPS measurement, fault deformation survey, leveling and focal mechanism solution

Based on the Chinese mainland GPS network (1994~1996), Fujian GPS network (1995~1997), cross fault deformation network (1982-1998), precise leveling network (1973~1980) and focal mechanism solutions of the recent several tens years, we synthetically and quantitatively studied the present-time crustal motion of the southeast coast of Chinese mainland-Fujian and its marginal sea. We find that this area with its mainland together moves toward SE with a rather constant velocity of 11 .2±3.0 mm/a. At the same time, there is a motion from the Quanzhou bay pointing to hinterland, with a major orientation of NW, extending toward two sides, and with an average velocity of 3.0±2.6 mm/a. The faults orienting NE show compressing motions, and the ones orienting NW show extending motions. The present-time strain field derived from crustal deformation is consistent with seismic stress field derived from the focal mechanism solutions and the tectonic stress field derived from geology data. The principal stress of compression orients NW (NWW) - SE (SEE). Demarcated by the NW orienting faults of the Quanzhou bay and Jinjiang-Yongan, the crustal motions show regional characteristics f the southwest of Fujian and the boundary of Fujian and Guangdong are areas of rising, the northeast of Fujian are areas of sinking. The horizontal strain rate and the fault motion of the former are both greater than the later. The side-transferring motion of Hymalaya collision zone and the compression of the west pacific subduction zone affect the motion of the research area. The amount of motion affected by the former is larger than the later, but the former is homogeneous and the later is not, which indicates that the events of strong earthquakes in this region relate more directly with western pacific subduction zone.

Fault activity characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake

Fault deformation characteristics in the northern margin of the Tibetan Plateau before the Menyuan Ms6.4 earthquake are investigated through time-series and structural geological analysis based on cross-fault observation data from the Qilian Mountain-Haiyuan Fault belt and the West Qinling Fault belt. The results indicate： 1） Group short-term abnormal variations appeared in the Qilian Mountain-Haiyuan Fault belt and the West Qinling Fault belt before the Menyuan Ms6.4 earthquake. 2） More medium and short-term anomalies appear in the middle-eastern segment of the Qilian Mountain Fault belt and the West Qinling Fault belt, suggesting that the faults＇ activities are strong in these areas. The faults＇ activities in the middle-eastern segment of the Qilian Fault belt result from extensional stress, as before the earthquake, whereas those in the West Qinling Fault belt are mainly compressional. 3） In recent years, moderate-strong earthquakes occurred in both the Kunlun Mountain and the Qilian Mountain Fault belts, and some energy was released. It is possible that the seismicity moved eastward under this regime. Therefore, we should pay attention to the West Qinling Mountain area where an Ms6-7 earthquake could occur in future.

Tectonic Phase Separation Applied to the Sudetic Marginal Fault Zone(NE part of the Czech Republic)

This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif(the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed:(1) the Gauss inverse method,(2) the Visualization of Gauss object Function, and(3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion usingT-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE(43), NNE-SSW(18), ENE-WSW(76) and the compressional one by σ1 trending W-E(26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.

Terraces and Tectonic Uplifts at Yandantu and Changcaogou on the Northern Margin Fault of Altun

The formation of strath and strath terrace is closely related to tectonic uplift in the drainage basin. Based on the investigation of straths at Yandantu and Changcaogou on the eastern segment of the northern margin fault of Altun, and in combination with the paleoclimatic data, the tectonic uplift since late Epipleistocene as revealed by stream terraces at the two places is discussed. At Yandantu, three levels of stream terraces(T 1, T 2 and T 3)have developed since 16ka BP, where T 1, T 3 and T 2 are fill terraces and the buried major straths are exposed. The ages of three treads are dated to be about 16.1ka BP, 12.8ka BP and 6.2ka BP, respectively. The three terraces reflect three tectonic uplift events, while the ages of the treads represent the occurrence time of these events. The stream is still beveling the bedrock and widening the channel at present, and the modern strath is being generated. The uplift rate is 4.8～4.5mm/a since 16.1 ka BP in this area. From 12.8ka B.P to 6.2ka BP, The uplift rate was 6.4mm/a. The uplift rate is 3.1mm/a since 6.2ka BP. At Changcaogou, four levels of stream terraces(T 1, T 2, T 3 and T 1′)have developed since 7ka BP. All of them are fill terraces. There are buried straths under the deposits. The buried major strath is exposed on T 3 and T 2 and the minor strath on T 1′and T 1. The ages of treads of the three terraces (T 3, T 2 and T 1′) are 7 ka BP, 3 ka BP and 2.5 ka BP, respectively. The four terraces reflect two uplift events induced by tectonic activities. One occurred in about 7 ka BP, and the other in 3ka BP. The uplift rate is 5.9mm/a since 7.0 ka BP at Changcaogou. From 7ka BP to 3ka BP, the uplift rate was 7.0mm/a, and since 3ka BP till now, the uplift rate is 4.7 mm/a.

The Research of the Activity of the Piedmont Fault on the Tangshankou Segment of the Yuguang Basin Southern Marginal Fault

The Yuguang basin is a half-graben basin in the basin-range tectonic zone in northwest Beijing,located at the northern end of the Shanxi graben system,and the Yuguang basin southern marginal fault( YBSMF) controls the formation of this basin. A linear fault escarpment has formed in the proluvial fan on the piedmont fault zone of the Tangshankou segment of YBSMF. A trench across this escarpment reveals three paleo-earthquake events on two active faults. One fault ruptured at about 9 ka for the first time,and then faulted again at about 7. 3 ka,causing the formation and synchronous activity of another fault.Finally,they faulted for the third time,but we cannot determine the faulting time due to the lack of relevant surface deposition. The accumulative vertical displacement of these three events is about 8. 1 m. We estimate that the average recurrence period of the piedmont fault is about 1. 7 ka,and the average slip rate of the piedmont fault is about1. 6 mm/a. We also estimate the reference magnitude of each event according to the empirical formula.

Present-day Block Movement and Fault Activity on the Eastern Margin of the Tibetan Plateau

The geology and tectonics in the eastern margin of Tibetan Plateau are complex. The main tectonic framework is composed of blocks and faults. Using discontinuous global positioning system survey data for 2008–2014, the velocity field for the Eurasia reference framework was obtained. Based on the velocity field, the present-day velocities of the blocks and boundary faults were estimated. The results reveal that the movement rates of the Chuan-Qing, South China, Chuan-Dian and Indo-China blocks are（17.02±0.60） mm/a,（8.77±1.51） mm/a,（13.85±1.31） mm/a and（6.84 ± 0.74） mm/a, respectively, and their movement directions are 99.5°, 120.3°, 142.9° and 153.3°, respectively. All blocks exhibit clockwise rotation. The displacement rates of the Xianshuihe, Longmenshan, Anninghe, Zemuhe, Xiaojiang and Red River faults are（7.30±1.25–8.30±1.26） mm/a,（10.07±0.97–11.79±0.89） mm/a,（0.96±0.74–2.98±1.73） mm/a,（2.03±0.49–3.20±0.73） mm/a,（3.45±0.40–6.02±0.50） mm/a and（6.23±0.56） mm/a, respectively. The Xianshuihe, Anninghe, Zemuhe and Xiaojiang faults show leftlateral strike-slip movement, while the Longmenshan and Red River faults show right-lateral strikeslip. These characteristics of the blocks and faults are related to the particular tectonic location and dynamic mechanism.

2023年12月18日积石山6.2级地震的深浅变形构造分析

2023年12月18日甘肃积石山6.2级地震震源区及邻区绝对板块运动方向与岩石圈方位各向异性有很好的一致性,区域浅地表变形与上地壳各向异性反映的变形特征都出现明显的空间扰动,上地壳的局部不均匀变形和物性差异是积石山地震的深部发震构造背景。地震发生在积石山东缘断裂,该断裂长约30~40 km,短期内不具备发生相当震级或更大地震的深部蕴震构造条件。

柴达木盆地北缘断裂锡铁山-阿木尼克山段第四纪晚期古地震活动性

柴达木盆地北缘断裂带是青藏高原北部的一条区域性活动断裂带,构成了柴达木盆地北部和祁连山的边界断裂,研究其第四纪晚期古地震活动对于理解柴达木盆地北缘断裂带地震复发周期、地震危险性等具有重要意义。通过地质考察、遥感解译、探槽开挖及OSL地质测年、古地震期次分析等,对柴达木盆地北缘断裂(锡铁山-阿木尼克山段)古地震事件进行了研究。研究表明:探槽剖面共揭露了5次比较可靠的古地震事件,发震时间分别为:事件E1距今约60 a;事件E23.1±0.3~3.4±0.3 ka;事件E37.5±0.3~8.1±0.3 ka;事件E410.1±0.4~11.4±0.4 ka;事件E512.1±0.4~12.8±0.4 ka。利用古地震逐次限定法认为柴达木盆地北缘断裂(锡铁山-阿木尼克山段)地震复发周期为2.6~3.4 ka。阿木尼克山段最新离逝时间为60年前,锡铁山段最新离逝时间为3.1±0.3 ka,分析认为柴达木盆地北缘断裂锡铁山段未来遭遇破坏性地震的可能性大于阿木尼克山段。该结果可以更好地了解柴达木盆地北缘断裂的古地震期次、复发间隔等,对地震预报预测及评价该断裂未来地震危险性具有一定的指导意义。

忻定盆地金山凸起东缘断裂展布及晚第四纪最新活动特征

通过野外地质地貌调查结合无人机航拍测量、地质雷达勘探及浅层地震勘探综合分析认为,金山凸起东缘断裂整体呈NE向展布,走向40°,北起忻口村一带,向SW经金山铺村西、前淤泥村西延伸至部落村以北,进而向SWS转折进入盆地区。经探槽开挖和年龄测试,该断裂段最新断错晚更新世早期地层。

基于GNSS的西秦岭北缘断裂带现今活动特征研究

基于1999~2007年、2009~2013年、2013~2017年和2017~2021年共4期GNSS地壳运动速度场构建GNSS速度剖面,分析西秦岭北缘断裂带各次级断裂现今地壳差异运动特征,并进一步建立负位错模型反演获取各次级断裂现今闭锁程度与滑动亏损速率。结果表明:1)西秦岭北缘断裂带现今整体呈现出以左旋走滑为主、兼逆冲挤压的活动特征。2)1999~2007年,锅麻滩段和天水-宝鸡段整体处于强闭锁状态,漳县段和鸳凤段仅部分区段闭锁且闭锁程度较低,闭锁深度也较浅;2009~2013年,西秦岭北缘断裂带中段闭锁程度有所减弱,鸳凤段东部与天水-宝鸡段东部由较强闭锁转变为蠕滑状态,锅麻滩段和天水-宝鸡段中西部依然呈强闭锁状态;2013~2017年,西秦岭北缘断裂带整体处于较强闭锁状态,仅天水-宝鸡段东部呈蠕滑状态;2017~2021年,锅麻滩段中西部、漳县段、鸳凤段东部和天水-宝鸡段中部处于较强闭锁状态,鸳凤段中西部与天水-宝鸡段西部则呈蠕滑状态。3)各次级断裂滑动亏损速率整体分布特征与断裂闭锁程度基本一致。西秦岭北缘断裂带锅麻滩段和天水-宝鸡段中部现今处于较强闭锁状态,具有较强的应变能累积背景。

2023年甘肃积石山6.2级地震发震构造浅析

2023年12月18日23时59分,甘肃临夏州积石山县发生6.2级地震,造成人员伤亡和财产损失。本次地震发生在青藏高原东北缘地区,受青藏高原向NE向扩展挤压作用的影响,区域发育两组较为典型的断裂构造:NWW向大型左旋走滑断裂带是活动块体运动边界,另一组NNW向右旋走滑断裂则发育在块体内部构成次级块体边界。此次积石山6.2级地震就发生在NWW向西秦岭北缘左旋走滑断裂带和NNW向日月山右旋走滑断裂带之间的大型挤压阶区内,初步判定其发震构造为以逆冲作用为主的拉脊山断裂带东南段的积石山东缘断裂。余震展布范围严格限制在黄河以南的积石山东麓大河家第三系盆地内,根据黄河以北拉脊山和以南的积石山山脊线及坡折带存在较大不连续性,且沿黄河南岸发育较明显的断层三角面等构造地貌特征,推测沿黄河发育有一条调节区内挤压变形差异的横向断裂。断裂切断拉脊山北缘断裂带东南段,使积石山东缘断裂成为一个长度不足40 km的独立活动段,判定原震区近期发生更大地震的可能性不大。

塔里木盆地塔东地区油气地质条件与有利地质体资源潜力

大庆油田塔东探区主体位于塔里木盆地台盆过渡区满西台缘带,勘探程度低,资源潜力大。勘探主要集中在古城地区,未获规模突破。近年来通过老井复查、构造-岩相古地理研究,明确了台缘带油气基础地质条件,落实了成藏有利区带,拓展了塔里木盆地寒武系勘探新类型。结果表明:塔东探区发育玉满裂陷、玉都裂陷槽盆相,斜坡陆棚相等多套烃源岩;寒武系—中下奥陶统台缘带高能礁滩继承发育,多组走滑断裂控储、控藏、控富集;“黑被子”泥岩、“白被子”膏岩2套区域盖层分布广泛,源、储、盖紧密配置,具备规模成藏条件;纵向上,油气受走滑断裂及区域盖层控制,主要分布在中下奥陶统碳酸盐岩地层;横向上,以玉满、玉都裂陷槽为中心,油气规模富集;玉满奥陶系鹰山组上段断溶体、鹰山组下段礁滩-断溶复合体成藏条件优越,发育凝析气藏,是塔东最现实的效益勘探领域;寒武系盐下礁滩体、断控丘滩带源、储、盖配置好,资源潜力大,可作为增储上产的接替领域。塔东探区多领域均展现出万亿立方米的气资源规模,有望快速建成大庆油田稳油增气的重要基地。

2023年甘肃积石山M_(S)6.2地震:一次逆冲为主的浅源强震

基于区域数字地震台网波形数据,在三维空间内利用波形拟合反演方法获得2023年12月18日甘肃积石山M_(S)6.2地震最佳震源机制解,结果表明:节面Ⅰ走向305°,倾角56°,滑动角61°;节面Ⅱ为走向169°,倾角43°,滑动角125°;矩震级M_(W)6.02。最佳拟合的空间精细位置为102.377°E,35.968°N,深度9 km。结果显示,地震破裂沿NW方向扩展。初步推断此次地震的发震断层面为节面Ⅱ,发震断层是拉脊山北缘断裂(积石山东缘断裂),是一次逆冲为主,兼少量走滑分量的浅源强震事件。

新疆克拉玛依乌尔禾张扭性走滑断裂特征及其控藏作用研究

乌尔禾沥青矿断裂带位于准噶尔盆地西北缘乌夏断裂带乌尔禾鼻隆之上,是一个小型左旋走滑断裂带。断裂带形成后未发生强烈改造,断裂带内发育沥青矿脉,露头地质条件好,且有三维地震覆盖,是研究走滑断裂特征和控藏作用的天然实验室。本文采用无人机三维立体建模技术,结合野外剖面实测,对乌尔禾沥青矿走滑断裂带野外剖面露头进行定量分析和解剖。结果表明,沥青矿断裂带共发育17条断层,主断层西北侧断层呈雁列状分布,东南侧断层呈马尾状,断裂带纵向呈负花状。研究表明,断层形成于燕山期左旋剪切应力场,受拉张应力影响,整体处于张扭环境,形成张扭性走滑断裂带。断层发育空腔和诱导裂缝,尤其主动盘裂缝更为发育,空腔的开度与油气侵染宽度呈正相关。结合塔里木盆地张扭性走滑断裂与油气藏关系分析,本文认为张扭性走滑断裂是良好的垂向油气运移通道,主动盘具有侧向输导作用,被动盘具有封堵作用,走滑断裂主动盘一侧圈闭是良好的油气聚集区域。

柴北缘骆驼泉剖面新生代地层磁组构特征及其构造意义

青藏高原东北部新生代构造演化对理解高原隆升和变形模式具有重要意义,而目前对于该地区挤压应力方向转变过程仍存在很大争议.本文对柴北缘逆冲带北西部骆驼泉剖面新生代地层开展系统磁组构(本文特指磁化率各项异性)研究,以揭示该地区挤压应力方向的转变特征.系统岩石磁学结果表明,骆驼泉剖面新生代样品中主要磁性矿物是顺磁性组分和赤铁矿以及少量磁铁矿.通过对磁组构特征分析及其与古水流方向对比表明,骆驼泉剖面新生代地层磁组构主要为初始变形磁组构,可用于指示沉积成岩时期的挤压应力方向.磁组构结果揭示,骆驼泉地区挤压应力方向在上干柴沟组下部沉积时期为NNE-SSW向,而上干柴沟组上部和油砂山组沉积时期转变为NE-SW向.结合柴北缘逆冲带已有磁组构结果指出,该地区早期N-S向或NNE-SSW向挤压应力可能与印度—欧亚板块早新生代以来近N-S向碰撞挤压过程有关,指示印度—欧亚碰撞的挤压应力自下干柴沟组下部沉积时期就已传播至高原东北部地区;而后期NE-SW向挤压应力方向与该地区现今GPS揭示的上地壳运动方向一致,可能与该时段高原东北部巨型走滑断裂构造体系(尤其是阿尔金断裂)有关.此外,柴北缘逆冲带新生代挤压应力方向转变在其北西部起始于上干柴沟组下部沉积时期,而南东部起始于上油砂山组下部沉积时期,与地震反射剖面揭示的断裂活动等地质证据共同揭示柴北缘逆冲带新生代的构造活动自靠近阿尔金断裂的北西部向南东部传播和扩展.综合分析青藏高原东北部地区挤压应力方向转变和其他地质证据发现,挤压应力方向转变显示出自柴北缘逆冲带北西部向东、西和南向扩展特征,与阿尔金断裂在上干柴沟组下部-上油砂山组下部沉积时期剪切应力集中于断裂本身,而上油砂山组下部沉积以来开始散布于高原东北部内部地区的两阶段走滑活动相关.

2023年12月18日甘肃省积石山6.2级地震的控震构造及特征

2023年12月18日23时59分在甘肃省临夏州积石山县发生6.2级地震,造成了严重人员伤亡,及时了解此次地震的发震构造及其特征,对于分析区域未来强震危险性具有重要意义。综合区域地震构造、地质、震源机制、地震烈度和余震重定位等资料,对此次地震的控震构造及特征进行综合分析后认为,此次强震是发生在西宁—兰州断块内部的一次北北西向逆冲断层作用事件,距震中最近的拉脊山逆冲断裂带构成了此次地震的控震构造。该断裂带处于北西向日月山右旋走滑断层与北西西向西秦岭北缘左旋走滑断层交汇部位,整体呈北西至北北西向弧形展布,包含了南缘与北缘两条倾向相反的分支断裂带。震中位置、余震及烈度分布等数据指示此次地震的具体发震断层为拉脊山北缘逆冲断裂带南段的东支断层带,余震分布和极震区范围等符合逆断层型地震的上盘效应特征,但是否引起同震地表变形,还需进一步的现场调查确定。综合研究认为,此次积石山地震是在印度与欧亚板块持续陆陆碰撞作用下,青藏高原东北缘的西宁—兰州断块沿海原左旋走滑断裂向东侧向滑移过程中,在北东向挤压构造应力场下,引发日月山断层与西秦岭北缘断层构成的区域共扼走滑断裂系交汇挤压部位发生逆断层活动的结果。此次强震进一步指示青藏高原东缘的向东挤出构造体系仍是近年来我国陆内强震活动的主要控震构造,并警示应重视活断层相对发育的断块内部城镇密集区的强震灾害风险。

新疆准噶尔盆地西北缘克拉玛依-乌尔禾断裂带推覆体上盘构造样式及影响因素

准噶尔盆地西北缘克拉玛依-乌尔禾断裂带(克-乌断裂带)及其周缘发现了大量的油气藏,尤其是推覆体上盘伴随着勘探程度及地质认识不断深化,已呈现出“百里油区”的态势。然而,受多期构造活动及断裂带内部复杂的岩性组合影响,石炭系内幕地层构造样式展现出多种类型及复杂的空间展布样式,因此需要对构造样式及成因进一步探讨。综合地震和钻井资料,结合区域构造格局,梳理了准噶尔盆地西北缘克-乌断裂带上盘构造变形特征与影响因素;根据构造样式与推覆体内的岩性组合类型,将克-乌断裂带推覆体上盘划分出南段、中段和北段3个变形单元;明确了上盘石炭系5期主要构造阶段,分段恢复了推覆体上盘构造演化期次及样式。综合上述研究,认为克-乌断裂带上、下盘原始岩性组合关系是造成上盘石炭系内幕地层原始形变差异的主要因素,上盘石炭系内幕地层岩性组合差异是造成原生构造保存的主要因素。上述因素共同造成了圈闭条件沿克-乌断裂带自南向北变化。该研究为克-乌断裂带上盘油气勘探提供指导,同时也为类似条件地区的油气勘探提供借鉴。

桑托斯盆地盐下孤立碳酸盐台地沉积建造与深水大油田

针对桑托斯被动陆缘盆地深水盐下碳酸盐岩储层分布特征及大油田成藏规律不清的难题,综合利用地质、地震及岩心等数据资料,通过早白垩世原型盆地与岩相古地理恢复重建,提出盐下碳酸盐岩沉积建造受控于坳间断隆型和坳中断凸型两类孤立台地。坳间断隆型孤立台地分布于现今盐下坳间隆起带上,建造于早期陆内和陆间裂谷两个原型阶段继承性发育的单断式和双断式垒式断块上,早白垩世陆内裂谷晚期沉积的ITP组介壳灰岩和陆间裂谷早期沉积的BVE组微生物灰岩为连续建造;坳中断凸型孤立台地分布于现今盐下坳陷带中,建造于早期陆内裂谷原型阶段火山岩建隆所形成的凸起带上,发育BVE组微生物灰岩。两类孤立台地灰岩所形成礁滩体均具有储层厚度大、物性好的特点。结合盐下已发现大油田解剖,发现两类台地均可形成大型构造-岩性复合圈闭,周缘为优质湖相和潟湖相烃源岩环绕,上覆为巨厚的优质蒸发盐岩盖层高效封堵,形成了“下生中储上盖”式最佳生储盖组合关系,油气富集程度高。已发现大油田均为具有统一压力系统的底水块状油田,且均处于充满状态。未来勘探重点目标是西部隆起带和东部隆起带南段上的坳间断隆型孤立台地及中央坳陷带中的坳中断凸型孤立台地。该项研究成果为在桑托斯被动陆缘盆地超前选区选带、新项目评价及中标区块探区勘探部署提供了重要依据,也为今后在全球被动大陆边缘盆地深水勘探战略选区提供借鉴。