Geometry and 3D seismic characterisation of post-rift normal faults in the Pearl River Mouth Basin,northern South China Sea

Based on high-resolution 3D seismic data acquired in the Pearl(Zhujiang)River Mouth Basin of the northern South China Sea,this study investigated the geometry,spatial extension,and throw distribution of the post-rift normal fault through detailed seismic interpretation and fault modeling.A total of 289 post-rift normal faults were identified in the study area and can be classified into four types:(1)isolated normal faults above the carbonate platform;(2)isolated normal faults cutting through the carbonate platform;(3)conjugate normal faults,and(4)connecting normal faults.Throw distribution analysis on the fault planes show that the vertical throw profiles of most normal fault exhibit flat-topped profiles.Isolated normal faults above the carbonate platform exhibit roughly concentric ellipses with maximum throw zones in the central section whereas the normal faults cutting through the carbonate platform miss the lowermost section due to the chaotic seismic reflections in the interior of the carbonate platform.The vertical throws of conjugate normal faults anomalously decrease toward their intersection region on the fault plane whereas the connecting normal faults present two maximum throw zones in the central section of the fault plane.According to the symmetric elliptical distribution model of fault throw,an estimation was made indicating that normal faults cutting through the carbonate platform extended downward between-1308 s and-1780 s(two-way travel time)in depth and may not penetrate the entire Liuhua carbonate platform.Moreover,it is observed that the distribution of karst caves on the top of the carbonate platform disaccord with those of hydrocarbon reservoirs and the post-rift normal faults cutting through the carbonate platform in the study area.We propose that these karst caves formed most probably by corrosive fluids derived from magmatic activities during the Dongsha event,rather than pore waters or hydrocarbons.

Characteristics of transfer zones under the influence of preexisting faults and regional stress transformation:Wenchang A subsag,Zhujiang River Mouth Basin,northern South China Sea

A transfer zone in rift basins preserves important information on regional tectonic evolution and plays significant roles in hydrocarbon accumulation.Based on the systematic analysis of 3D seismic data and hydrocarbon accumulation conditions,the geometry,kinematics,and reservoir control of a large synthetic overlapping transfer zone in the south of the Wenchang A subsag in the Zhujiang(Pearl)River Mouth basin were investigated.Results indicate that the development and evolution of the transfer zone was controlled by the interaction between pre-existing faults and regional stress transformation.The intense rifting of the main faults of the transfer zone controlled the development of source rocks and faultcontrolled slope break paleogeomorphology.The strike-slip overprint since the Oligocene is conducive to the formation of a large-scale fault-anticline trap,and the secondary faults in the transfer zone contribute to the hydrocarbon transportation.The conjugate intersection area of the NE-and NW-trending faults offers more opportunity for hydrocarbon migration and accumulation.

An integrated north–south paleo-Dadu-Anning River: New insights from bulk major and trace element analyses of the Xigeda Formation

The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.

Offshore Fault Geometrics in the Pearl River Estuary,Southeastern China:Evidence from Seismic Reflection Data

The Pearl River Estuary(PRE) is located at the onshore-offshore transition zone between South China and South China Sea Basin, and it is of great significant value in discussing tectonic relationships between South China block and South China Sea block and seismic activities along the offshore active faults in PRE. However, the researches on geometric characteristics of offshore faults in this area are extremely lacking. To investigate the offshore fault distribution and their geometric features in the PRE in greater detail, we acquired thirteen seismic reflection profiles in 2015. Combining the analysis of the seismic reflection and free-air gravity anomaly data, this paper revealed the location, continuity, and geometry of the littoral fault zone and other offshore faults in PRE. The littoral fault zone is composed of the major Dangan Islands fault and several parallel, high-angle, normal faults, which mainly trend northeast to northeast-to-east and dip to the southeast with large displacements. The fault zone is divided into three different segments by the northwest-trending faults. Moreover, the basement depth around Dangan Islands is very shallow, while it suddenly increases along the islands westward and southward. These has resulted in the islands and neighboring areas becoming the places where the stress accumulates easily. The seismogenic pattern of this area is closely related to the comprehensive effect of intersecting faults together with the low velocity layer.

The Cenozoic activities of Yangjiang-Yitongdong Fault: insights from analysis of the tectonic characteristics and evolution processes in western Zhujiang(Pearl) River Mouth Basin

The Yangjiang-Yitongdong Fault (YJF) is an important NW-trending regional fault, which divides the Zhujiang (Pearl) River Mouth Basin (ZRMB) into western and eastern segments. In Cenozoic, the northern continental margin of the South China Sea (SCS) underwent continental rifting, breakup, seafloor spreading and thermal subsidence processes, and the Cenozoic activities of YJF is one part of this series of complex processes. Two long NW-trending multichannel seismic profiles located on both sides of the YJF extending from the continental shelf to Continent-Ocean Boundary (COB) were used to study the tectonic and sedimentary characteristics of western ZRMB. Using the 2D-Move software and back-stripping method, we constructed the balance cross-section model and calculated the fault activity rate. Through the comprehensive consideration of tectonic position, tectonic evolution history, featured structure, and stress analysis, we deduced the activity history of the YJF in Cenozoic. The results showed that the YJF can be divided into two segments by the central uplift belt. From 65 Ma to 32 Ma, the YJF was in sinistral motion as a whole, inherited the preexisting sinistral motion of Mesozoic YJF, in which, the southern part of YJF was mainly in extension activity, controlling the formation and evolution of Yunkai Low Uplift, coupled with slight sinistral motion. From 32 Ma to 23.8 Ma, the sinistral motion in northern part of YJF continued, while the sinistral motion in southern part began to stop or shifted to a slightly dextral motion. After 23.8 Ma, the dextral motion in southern part of YJF continued, while the sinistral motion in northern part of YJF gradually stopped, or shifted to the slightly dextral motion. The shift of the YJF strike-slip direction may be related to the magmatic underplating in continent-ocean transition, southeastern ZRMB. According to the analysis of tectonic activity intensity and rift sedimentary structure, the activities of YJF in Cenozoic played a regulating role in the rift extension process of ZRMB.

K-Ar Dating of Fault Gouges from the Red River Fault Zone of Vietnam

Constraining the timing of fault zone formation is fundamentally important in terms of geotectonics to understand structural evolution and brittle fault processes.This paper presents the first authigenic illite K-Ar age data from fault gouge samples collected from the Red River Shear Zone at Lao Cai province,Vietnam.The fault gouge samples were separated into three grain-size fractions（〈0.1 μm,0.1-0.4 μm and 0.4-1.0 μm）.The results show that the K-Ar age values decrease from coarser to finer grain fractions（24.1 to 19.2 Ma）,suggesting enrichment in finer fraction of morerecently grown authigenic illites.The timing of the fault movement are the lower intercept ages at 0%detrital illite（19.2 ± 0.92 Ma and 19.4 ± 0.49 Ma）.In combination with previous geochronological data,this result indicates that the metamorphism of the Day Nui Con Voi（DNCV） metamorphic complex took place before ca.26.8 Ma.At about 26.8 Ma-25 Ma,the fault strongly acted to cause the rapid exhumation of the rocks along the Red River-Ailoa Shan Fault Zone（RR-ASFZ）.During brittle deformation,the DNCV slowly uplifted,implying weak movement of the fault.This brittle deformation might have lasted for ca.5 Ma.

Main active faults and seismic activity along the Yangtze River Economic Belt:Based on remote sensing geological survey

The Yangtze River Economic Belt(YREB)spans three terrain steps in China and features diverse topography that is characterized by significant differences in geological structure and presentday crustal deformation.Active faults and seismic activity are important geological factors for the planning and development of the YREB.In this paper,the spatial distribution and activity of 165 active faults that exist along the YREB have been compiled from previous findings,using both remote-sensing data and geological survey results.The crustal stability of seven particularly noteworthy typical active fault zones and their potential effects on the crustal stability of the urban agglomerations are analyzed.The main active fault zones in the western YREB,together with the neighboring regional active faults,make up an arc fault block region comprising primarily of Sichuan-Yunnan and a“Sichuan-Yunnan arc rotational-shear active tectonic system”strong deformation region that features rotation,shear and extensional deformation.The active faults in the central-eastern YREB,with seven NE-NNE and seven NW-NWW active faults(the“7-longitudinal,7-horizontal”pattern),macroscopically make up a“chessboard tectonic system”medium-weak deformation region in the geomechanical tectonic system.They are also the main geological constraints for the crustal stability of the YREB.

Dynamic Analysis of Deformational Structures of the Xianniishan Fault Zone in the Three Gorges of the Yangtze River

Field investigation and laboratory work reveal that inhomogeneity of the deformation of the Xiannushan fault is mainly characterized by lateral zonation, longitudinal segmentation and downward stratification. Based on these results, a 3-D deformational structure model of the fault was established and its geometrical and kinematic characteristics in two main deformational stages i.e. the main Yanshanian and Himalayan were discussed. The directions of principal and the differential stresses in these two stages were determined by using conjugate joints, striations of fault planes and microstructures of the fault zone. The direction of σI is N-S in direction with differential stresses of 150-250 MPa in the Yanshanian, and N70E with a differential stress ranging from 80-120 MPa in the Himalayan.

The neotectonic deformation and earthquake activity in Zhuanglang river active fault zone of Lanzhou

Lanzhou Institute of Seismology, China Seismological Bureau, Lanzhou 730000, China 2) Institute of Geology, China Seismological Bureau, Beijing 100029, China

The Holocene Activity Evidence of the Yema River-Daxue Mountain Fault in Western Qilian Mountain

Altyn Tagh fault controls the deformation characteristics of the northern margin of the Qinghai-Tibet Plateau.The sinistral slip rate of the eastern segment of the fault reduces gradually where the reduction transforms into the deformation within Qilian Mountain,forming a series of thrust faults and strike-slip faults.Among them,the Yema River-Daxue Mountain fault is one of the important structural transform faults in the study area.Based on the differences of the geometrical characteristics and activities,the fault is divided into four segments,the Yema River segment,the Shibandun segment,the Liushapo segment and the Baishitougou segment,among which the former three are Holocene active faults,and the Baishitougou segment belongs to late Pleistocene fault.The excavated trenches imply a total of 6 paleoearthquake events,and at least 4 events have occurred during Holocene,whose occurrence times are 8300±700 yr BP,6605±140 yr BP,4540±350 yr BP,2098±47 yr BP,respectively.The recurrence interval is 2600±600 yr BP that is close to the lapsed time of the last one,2098±47 yr BP,which suggests that the Yema River-Daxue Mountain fault is in a high risk of major earthquakes in the future.The vertical coseismic displacements of the four Holocene paleoearthquake events are 100 cm,42 cm,40 cm and 50 cm,respectively,the horizontal coseismic displacements are 5 m,4.5-5.5 m,5-8 m and 4-5.5 m,separately,and then the reference magnitude of the paleoearthquake events is conjectured to be M7.6±0.1.

EARTHQUAKE FOCAL MECHANISM AND ITS TECTONIC SIGNIFICANCE ALONG THE TWO SIDES OF THE RED RIVER FAULT ZONE

The Red River Fault Zone is a gigantic slide-slip fault zone extending up to 1000km from Tibet to SouthChina Sea. It has been divided into the north, central and south segments according to the difference of thegeometry, kinetics, and seismicity on the land, but according to the contacted relationship between the old pre-Cenozoic block in Indochina Peninsula and the South China block, the Red River Fault Zone was divided into two parts extending from land to ocean, the north and south segments. Since the Tertiary, the Red River Fault Zone suffered first the sinistral movement and then the dextral movement. The activities of the north and the south segments were different. Based on the analysis of earthquakes and focal mechanism solutions,earthquakes with the focus depths of 0-33km are distributed over the whole region and more deep earthquakes are distributed on the northeastern sides of the Red River fault. Types of faulting activities are the thrust in the northwest, the normal in the north and the strike-slip in the south, with the odd type, viz. the transition type, in the other region. These show the Red River Fault Zone and its adjacent region suffered the extruding force in NNW direction and the normal stress in NEE direction and it makes the fault in the region extrude-thrust,horizontal strike-slip and extensional normal movement.

Slip Rate of Yema River–Daxue Mountain Fault since the Late Pleistocene and Its Implications on the Deformation of the Northeastern Margin of the Tibetan Plateau

The slip rate of Yema River-Daxue Mountain fault in the western segment of Qilian Mountains was determined by the dated offset of river risers or gullies. Results indicate that the left-lateral fault slip rate is 2.82± 0.20 mm/a at Dazangdele site, 2.00 ± 0.24 mm/a at Shibandun site, and 0.50± 0.36 and 2.80±0.33 mm/a at two sites in Zhazihu. The ideal average slip rate of the whole fault is 2.81 ± 0.32 mm/a. The lower slip rate confirms part of the displacement of Altyn Tagh fault was transformed into an uplifting of the strap mountains in the western segment of Qilian Mountains, whereas another part transformed into sinistral displacement of Haiyuan fault. This study illustrates that the slip of large strike-slip faults in the northeastern margin of the plateau transforms into crust thickening at the tip of the fault without large-scale propagation to the outer parts of the plateau.

The characteristics of Quaternary activity of faults in the sea area near the Yangtze River mouth

By shallow seismic prospecting, it is showed that the faults in the sea area near the Yangtze River mouth are mainly the NE and NW-trending faults. The main activity time of fault is Pliocene to Early Pleistocene, and the latest activity is up to Middle Pleistocene. The maximum of fault is generally several tens meters with the throw decreased upward. The dislocation near the bottom of Middle Pleistocene is 12~13 m. The average vertical dis-placement rate is on a level of 10-3 mm/a.

Large-Scale Dextral Strike-Slip Movement and Associated Tectonic Deformation Along the Red-River Fault Zone

Field investigation has revealed that the large-scale dextral strike-slip movement and the associated tectonic deformation along the Red River fault zone have the following features: geometrically, the Red River fault zone can be divided into three deformation regions, namely, the north, central and south regions. The north region lies on the eastern side of the Northwest Yunnan extensional taphrogenic belt, which is characterized by the 3 sets of rift-depression basins striking NNW, NNE and near N-S since the Pliocene time, and on its western side is the Lanping-Yunlong compressive deformation belt of the Paleogene to Neogene; the deformation in the central region is characterized by dextral strike-slip or shearing. The east Yunnan Miocene compressive deformation belt lies on the eastern side of the fault in the south, and the Tengtiaohe tensile fault depression belt is located on its west. In terms of tectonic geomorphology, the aforementioned deformation is represented by basin-range tectonics in the north, linear faulted valley-basins in the central part and compressive (or tensional) basins in the south. Among them, the great variance in elevation of the planation surfaces on both sides of the Cangshan-Erhai fault suggests prominent normal faulting along the Red River fault since the Pliocene. From the viewpoint of spatial-temporal evolution, the main active portion of the fault was the southern segment in the Paleogene-Miocene-Pliocene, which is represented by “tearing” from south to north. The main active portion of the fault has migrated to the northern segment since the Pliocene, especially in the late Quaternary, which is characterized by extensional slip from north to southeast. The size of the deformation region and the magnitude of deformation show that the eastern plate of the Red River fault has been an active plate of the relative movement of blocks.

Preliminary Study on Cenozoic Group and Fault Activity in the Sea Area Near the Yangtze River Mouth

By shallow seismic prospecting, the Cenozoic Group in the sea area near the Yangtze River Mouth can be divided into five seismic sequences. They correspond to the Quaternary, Pliocene, Upper Miocene, Lower Miocene and Eocene respectively. The Quaternary System covers all the detecting area. The Tertiary System overlaps and thins out from NE to SW. The sedimentary basement mainly consists of volcanic rock (J 3) and acidic rock (r 3 5). Paleogene or Late Cretaceous basins are not found there. The faults that have been detected are all normal faults. They can be divided into three groups (NE, NW, near EW) by their trend. The NE and NW trending faults are predominant, and agree with aeromagnetic anomaly. Their length and displacement are larger than that of the EW trending faults. The activity of the NE trending faults is different in different segments. The SW segment is a Quaternary fault, the middle segment is a Neogene fault, The NE is Paleogene. But the segment of the NW trending fault is not obvious. The average vertical displacement rate is about 0 015mm/a.

引江补汉工程千米级深孔地应力测试及近场断裂稳定性分析

引江补汉工程是南水北调后续工程的首个开工建设项目,其引水隧洞穿越了蠕滑型活动断裂-通城河断裂,研究活动断裂近场地应力特征对工程稳定性具有重要意义。选择较为复杂的通城河活动断裂近场区内开展了原位地应力测试及断裂构造稳定性分析,揭示断裂构造内现今地应力状态及断裂构造滑动失稳临界条件。通过在通城河活动断裂近场2个千米级深孔进行原位水压致裂法地应力测试。最后,基于实测地应力资料,结合库伦摩擦滑动准则及Byerlee定律对活动断裂稳定性进行了分析。结果表明:测试范围内存在应力分区,并推测以潜在转换深度900±20 m为界,空间主应力状态呈现由复合型(逆断型与走滑型)或逆断型向正断型的转换,表明近场地应力受交汇构造影响;实测最大水平主应力方向随孔深增加由NW向转为NWW向,与活动断裂运动力学特性、交汇断裂的左旋运动机制以及震源机制解基本一致;通城河活动断裂近场应力积累水平较低,尚未到失稳滑动水平,地壳是相对稳定的。研究结果为引江补汉工程穿通城河活动断裂工程区稳定性评价提供基础地质力学资料,为跨活动断裂的工程设计提供参考依据。

雅鲁藏布江断裂带东段现今地应力测量与断层活动性分析

为获取位于雅鲁藏布江断裂带东段加查县新建水电站工程场区的地应力状态,探讨雅鲁藏布江断裂带东段活动性,采用自主研发的新一代水压致裂地应力测试技术,实测获取了工程场区的地应力状态,并在收集雅鲁藏布江断裂带沿线地应力数据基础上,结合摩尔-库仑破裂准则,对其断层活动性进行了探讨。结果表明:(1)在工程厂区内122.75~418.75 m深度,实测最大水平主应力SH介于6.07~37.62MPa之间,最小水平主应力Sh介于3.13~20.33MPa之间,最大水平主应力优势方向为北北东向;(2)主应力关系总体表现为SH>Sh>Sv(Sv为垂向主应力),应力结构有利于逆断层的孕育和活动;(3)实测及收集的大部分数据应力莫尔圆与摩擦系数为0.6的破坏临界线相交,表明整体上雅鲁藏布江断裂带东段发生滑动失稳的风险较高,其中西侧贡嘎至朗县一带风险高于东侧林芝地区。

塔里木盆地塔河油田逆冲背斜区奥陶系古暗河系统发育特征

塔里木盆地塔河油田古暗河系统研究尚处于初始阶段,主要从暗河的深浅分布、结构样式等特征开展暗河洞穴的划分,较少从构造、断裂、古地貌、地下水位等地质方面综合分析复杂暗河系统的空间发育规律,致使暗河的主次从属关系、空间叠置样式、原始连通关系难以厘清,从而制约了塔河油田开发后期的综合治理研究。为了明确塔河油田主体区逆冲背斜区奥陶系古暗河系统发育特征,利用构造断裂解析、古地貌恢复、地震属性刻画、纵断剖面解读等方法进行了S67井区古暗河的类型识别、系统划分和地质成因研究,尤其首次识别并剖析了潜流回流暗河。结果表明,S67井区处于塔河主体区岩溶台原南缘的低地势区,发育幅差较小的峰丛洼地、溶丘洼地,地表水系下切深度较浅;逆冲背斜为低角度逆冲推覆构造样式,逆冲背斜之上的网格状断裂为多层状暗河系统提供有利溶蚀通道。研究区奥陶系发育相对独立的、树枝状结构的地下水位暗河系统和潜流带暗河系统,地下水位型暗河可分为主干型、支流型和废弃型,潜流回流暗河可分为上升型、对称型。控制逆冲背斜区古暗河发育的主要因素有古地貌、地下水位、逆冲背斜构造和次级断裂网络等。

海拉尔盆地中部断陷带下白垩统南屯组致密储层特征及有利区预测

综合运用岩心分析、铸体薄片、高压压汞等资料,对海拉尔盆地中部断陷带下白垩统南屯组储层特征及其主控因素开展了详细研究,并对有利区进行了定量综合评价。研究结果表明:(1)海拉尔盆地中部断陷带南屯组岩石类型主要为岩屑砂岩和长石岩屑砂岩,储层孔隙度小于12%的样品数占总样品数的70.2%,渗透率小于1 mD的样品数占总样品数的66.3%,属于致密砂岩储层,储层储集空间主要为少量原生孔隙和大量次生溶蚀孔隙。(2)沉积相控制了研究区储层物性在空间上的总体分布规律,南屯组最有利的沉积相带是辫状河三角洲前缘和扇三角洲前缘亚相;压实作用对储层具有减孔效应,溶蚀作用普遍发育,形成了大量粒间和粒内溶孔,对储集性具有一定改善作用。(3)盆地中部断陷带发育缓坡断阶构造带、陡坡断阶构造带和洼槽带3种构造带,其中缓坡断阶构造带和陡坡断阶构造带为主要的油气聚集区带,其断裂的大量发育均早于或同期于烃源岩大量排烃阶段,为油气运移提供了通道。(4)将“沉积相-孔隙度-储层厚度-砂地比-埋藏深度”五要素进行叠合,定量评价有利储层发育区,其中Ⅰ类、Ⅱ类优质储层主要分布在盆地中部断陷带的缓坡断阶构造带和陡坡断阶构造带。

塔里木盆地塔河北部“过溶蚀残留型”断溶体发育特征及其成因

为了研究塔里木盆地塔河北部强剥蚀区海西早期古岩溶洞穴发育特征,用古地貌恢复、岩溶水系统分析、测井-岩心洞穴识别和地震属性刻画等方法进行了YQ5井区的洞穴类型样式识别、缝洞结构刻画和洞穴成因演化研究。研究结果表明:YQ5井区在塔河油田Ⅱ号和Ⅲ号古岩溶台地北部的地势平缓区,总体为多期次岩溶叠加改造后的残留地貌,主要发育幅差较小的溶峰洼地、溶丘洼地和溶丘平原,南部发育NE向展布的峰丛垄脊沟谷。与塔河油田主体区及斜坡区不同,YQ5井区地下和地表水系的流向与地貌趋势不一致,岩溶水系统遭受构造作用破坏,导致补给、径流和排泄的岩溶水循环过程不完整。YQ5井区主要发育暗河型洞穴和“过溶蚀残留型”断溶体。暗河型洞穴充填较为严重,洞穴的有效储集空间受到破坏,影响油气开发效果。岩溶台地的构造抬升造成区域侵蚀基准面的下降,顺走滑断裂的垂向侵蚀作用有利于“过溶蚀残留型”断溶体的持续发育和保存,油气开发效果好。“过溶蚀残留型”断溶体的发育主控因素为走滑断裂、地层剥蚀强度和负向地貌。与塔河古岩溶台地演化过程一致,YQ5井区的岩溶演化经历深切曲流期、岩溶改造期和下渗断溶期3个阶段。暗河型洞穴被持续改造破坏,断溶体则持续建造。