Structural relationship between the Sea of Marmara Basin and the North Anatolian Fault Zone

The North Anatolian Fault (NAF) zone is 1500 km long, extending almost up to the Greek mainland in the west. It is a seismically active right-lateral strike-slip fault that accommodates the relative motion between the Turkish block and Black Sea plate. The Sea of Marmara lies along the western part of the NAF and shows evidence of subsidence. In this area pure strike-slip motion of the fault zone changes into extensional strike-slip movement that is responsible for the creation of the Sea of Marmara and the North Aegean basins. The northern half of the Sea of Marmara is interpreted as a large pull-apart basin. This basin is subdivided into three smaller basins separated by strike-slip fault segments of uplifted blocks NE-SW. Basinal areas are covered by horizontally layered sedimentary sequences. Uplifted blocks have undergone compressional stress. All the blocks are subsiding and are undergoing vertical motions and rotations relative to one another. The uplifted blocks exhibit positive Bouguer gravity anomalies. According to gravity interpretation, there is relative crustal thinning under the Sea of Marmara. The northern side of the Sea of Marmara is marked by a distinctive deep-rooted magnetic anomaly, which is dissected and shifted southward by strike-slip faulting. The southern shelf areas of the Sea of Marmara are dominated by short-wavelength magnetic anomalies of shallow origin.     

Stress modeling to determine the through-going active fault geometry of the Western North Anatolian Fault,Turkey

The North Anatolian Fault (NAF) is a 1200 km long dextral strike-slip fault which is part of an east-west trending dextral shear zone (NAF system) between the Anatolian and Eurasian plates. The North Anatolian shear zone widens to the west, complicating potential earthquake rupture paths and highlighting the importance of understanding the geometry of active fault systems. In the central portion of the NAF system, just west of the town of Bolu, the NAF bifurcates into the northern and southern strands, which converge, then diverge to border the Marmara Sea. At their convergence east of the Marmara Sea, these two faults are linked through the Mudurnu Valley. The westward continuation of these two fault traces is marked by further complexities in potential active fault geometry, particularly in the Marmara Sea for the northern strand, and towards the Biga Peninsula for the southern strand. Potential active fault geometries for both strands of the NAF are evaluated by comparing stress models of various fault geometries in these regions to a record of focal mechanisms and inferred paleostress from a lineament analysis. For the Marmara region, the best-fit active fault geometry consists of the northern and southern bounding faults of the Marmara basin, as the model representing this geometry better replicated primary stress orientations seen in focal mechanism data and stress field interpretations. In the Biga Peninsula region, the active geometry of the southern strand has the southern fault merging with the northern fault through a linking fault in a narrow topographic valley. This geometry was selected over the other two as it best replicated the maximum horizontal stresses determined from focal mechanism data and a lineament analysis.     

The rodent fauna from the Adapazarı pull-apart basin (NW Anatolia): its bearings on the age of the North Anatolian fault

To the east of the Sea of Marmara, the North Anatolian fault (NAF) branches into two strands, namely the northern and the southern strands. The Adapazarı pull-apart basin is located in the overlapping zone of the Dokurcun and the İzmit–Adapazarı segments of the northern strand. The combined temporal ranges of the arvicolids from the Karapürçek formation (the first unit of the basin fill), deposited in the primary morphology of the Adapazarı pull-apart basin, cover the latest Villanyian (latest Pliocene) and the Biharian (Early Pleistocene) time interval. The Değirmendere fauna collected from the lowermost sediments of this formation suggests that the Adapazarı pull-apart basin started to form in the latest Pliocene. This, in turn, suggests that the dextral movement along the northern strand of the NAF commenced during the latest Pliocene. A new species, Tibericola sakaryaensis is also described.     

Structural interpretation of the Marmara region, NW Turkey, from aeromagnetic, seismic and gravity data

The seismically active Marmara region, located in NW Turkey, lies on the westward end of the North Anatolian Fault (NAF). The NAF is well defined on land. Previous investigations of its extension in the Marmara Sea include marine bathymetry, seismological activity and seismic profiles. In this study, faults and their configurations identified inland are extended into the Marmara Sea by means of aeromagnetic anomalies, as well as seismic and gravity profiles. The deep structure was resolved by constructing a map of the Tertiary bottom. Shallow Curie isotherm was determined by spectral analysis, indicating a thinner crust in the northern Marmara depression area with respect to the continental crust. A combination of the geophysical data allows us to propose the existence of subsidence and isostatic equilibrium in the northern Marmara Sea. A less-active zone identified in the central high zone dividing the Marmara Sea into two parts may also be deduced from the seismic data. This structural arrangement may play a key role in earthquakes that will affect the surrounding regions.     

Late Cenozoic tectonics and stratigraphy of northwestern Anatolia: the effects of the North Anatolian Fault to the region

In northwest Anatolia, there is a mosaic of different morpho-tectonic fragments within the western part of the right-lateral strike-slip North Anatolian Fault (NAF) Zone. These were developed from compressional and extensional tectonic regimes during the paleo- and neo-tectonic periods of Turkish orogenic history. A NE-SW-trending left-lateral strike-slip fault system (Adapazari-Karasu Fault) extends through the northern part of the Sakarya River Valley and began to develop within a N–S compressional tectonic regime which involved all of northern Anatolia during Middle Eocene to early Middle Miocene times. Since the end of Middle Miocene times, this fault system forms a border between a compressional tectonic regime in the eastern area eastwards from the northern part of the Sakarya River Valley, and an extensional tectonic regime in the Marmara region to the west. The extension caused the development of basins and ridges, and the incursions of the Mediterranean Sea into the site of the future Sea of Marmara since Late Miocene times. Following the initiation in late Middle Miocene times and the eastward propagation of extension along the western part of the NAF, a block (North Anatolian Block) began to form in the northern Anatolia region since the end of Pliocene times. The Adapazari-Karasu Fault constitutes the western boundary of this block which is bounded by the NAF in the south, the Northeast Anatolian Fault in the east, and the South Black Sea Thrust Fault in the north. The northeastward movement of the North Anatolian Block caused the formation of a marine connection between the Black Sea and the Aegean/Mediterranean Sea during the Pleistocene.     

The rodent fauna from the Adapazarı pull-apart basin (NW Anatolia): its bearings on the age of the North Anatolian fault

Abstract

To the east of the Sea of Marmara, the North Anatolian fault (NAF) branches into two strands, namely the northern and the southern strands. The Adapazan pull-apart basin is located in the overlapping zone of the Dokurcun and the ?zmit-Adapazan segments of the northern strand. The combined temporal ranges of the arvicolids from the Karapürçek formation (the first unit of the basin fill), deposited in the primary morphology of the Adapazan pull-apart basin, cover the latest Villanyian (latest Pliocene) and the Biharian (Early Pleistocene) time interval. The De?irmendere fauna collected from the lowermost sediments of this formation suggests that the Adapazan pull-apart basin started to form in the latest Pliocene. This, in turn, suggests that the dextral movement along the northern strand of the NAF commenced during the latest Pliocene. A new species, Tibericola sakaryaensis is also described. © 2001 Éditions scientifiques et médicales Elsevier SAS     

Middle Pleistocene bivalves of the İznik lake basin (Eastern Marmara, NW Turkey) and a new paleobiogeographical approach

?znik Lake is a tectonically originated basin mainly controlled by the E–W trending middle strand of the North Anatolian Fault (NAF) system. Pleistocene sediments occurring in front of the faults are well exposed both in the northern and in the southern shorelines of the basin. In this study, two endemic brackish water bivalve species, Didacna subpyramidata Pravoslavkev 1939 and Didacna nov. sp. were found in the oldest terrace of the northern Pleistocene sequence. Having characterized morphology, these species serve as stratigraphic indicators in the regional Pleistocene stratigraphy of the Ponto-Caspian region, and thus are well correlated to the assemblages of the early Khazarian subhorizon (Middle Pleistocene). Hence, these data demonstrate that the early Khazarian brackish water sea covered the study area. Additionally, a model for the formation of the basin is proposed: the ?znik lake basin was a gulf of the former Marmara Sea in the early Khazarian, connecting the Marmara to the Black Sea and the Caspian Sea. The subsequent regional prograding uplifts, main dextral strike-slip fault and many normal faults of the NAF Zone cut off the marine connections to the basin, leading to its present location and topographic level.     

太行山中段羊角玄武岩形态特征及其地质意义

太行山中段左权羊角镇发育新生代玄武岩, 记录了太行山新生代以来的构造隆升事件。在详细的野外调查和研究的基础上, 通过与玄武岩发育相关的地貌面及其上的地层特征分析, 初步确定该玄武岩是上新世末期到早更新世初期的喷发产物, 初步揭示了太行山中段区域上晚上新世以来地貌发育历史, 主要存在6次构造隆升与剥蚀期: 在唐县期宽谷面形成的基础上, 于上新世晚期存在一次隆升和一次稳定侵蚀期, 并侵蚀形成“U”形谷; 早更新世初, 玄武岩开始间歇性喷发, 同时发生以西武家坪为中心的地区上拱, “U”形谷为玄武岩充填, 之后经剥蚀堆积形成第四级阶地面; 早更新世末, 该区再次发生隆升, 并形成第四级阶地; 中更新世末, 该区发生隆升, 形成第三级阶地; 晚更新世以来, 太行山中段又连续发生两次抬升, 从而在玄武岩体上形成了4级阶地, 形成太行山现今地貌。研究同时表明, 太行山中段上新世晚期以来的隆升主要发生于上新世末到早更新世时期。这一认识为探讨太行山中段晚上新世以来的构造隆升提供了具体证据。     

Asymmetric slip partitioning in the Sea of Marmara pull‐apart: a clue to propagation processes of the North Anatolian Fault?

Between 1939 and 1999 the North Anatolian fault (NAF) experienced a westward progression of eight large earthquakes over 800 km of its morphological trace. The 2000-km-long North Anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale (∼10 Myr). The Sea of Marmara is a large pull-apart that appears to have been a geometrical/mechanical obstacle encountered by the NAF during its propagation. The present paper focuses on new high-resolution data on the submarine fault system that forms a smaller pull-apart beneath the Northern Sea of Marmara, between two well-known strike-slip faults on land (Izmit and Ganos faults). The outstandingly clear submarine morphology reveals a segmented fault system including pull-apart features at a range of scales, which indicate a dominant transtensional tectonic regime. There is no evidence for a single, continuous, purely strike-slip fault. This result is critical to understanding of the seismic behaviour of this region of the NAF, close to Istanbul. Additionally, morphological and geological evidence is found for a stable kinematics consistent both with the long-term displacement field determined for the past 5 Myr and with present-day Anatolia/Eurasia motion determined with GPS. However, within the Sea of Marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull-apart. The loading associated with the westward propagation process of the NAF may have provided a favourable initial geometry for such a slip separation.     

南海北部陆坡高速堆积体的构造成因

南海北部陆坡是南海海域沉积活动最为活跃的地区之一,发育着迄今为止所发现的南海最高沉积速率堆积体。构成该堆积体的沉积物究竟来自何方,仍是南海沉积学研究中未解决的问题之一。通过对南海北部多道地震剖面的解释和海底底流观测资料的分析,指出南海北部中新统披覆层是南海北部断陷阶段结束后开始沉积的一套地层,直到上新世开始前,该地层在很大一个区域内是保持水平的;上新世后,由于构造抬升,中新统披覆层随之隆起,并在东沙隆起的部位遭受很大程度的剥蚀,其剥蚀量和南海北部珠江、韩江以及台湾西南部高屏溪和曾文溪向南海的输沙量相当,为南海北部一个非常重要的沉积物来源。研究分析指出,如果珠江和韩江所携带的沉积物全部沉积到南海北部陆坡区,则可获得的沉积速率为12 cm/ka,这一数值远低于该高速堆积体上的沉积速率值。从南海北部现今的沉积动力条件和地形上看,来自珠江和韩江的沉积物几乎不可能经过平坦的陆架区,再绕过东沙岛,优先沉积到该高速堆积体上。本研究中的高速堆积体的沉积物也不可能主要来自台湾西南的高屏溪和曾文溪,因为台西南河流所携带的沉积物被特殊的洋流体系圈闭于台湾周边一个较小的范围内沉积下来。观测数据表明,南海北部东沙隆起区有足够强的水动力环境能够剥蚀海底隆起的沉积地层,并将剥蚀下来的沉积物向南经陆架输运到陆坡区;该高速堆积体紧邻东沙隆起剥蚀区,其沉积物来源应该主要来自东沙隆起剥蚀区。     

Active faults in the Sea of Marmara, western Turkey, imaged by seismic reflection profiles

Turkey is moving westward relative to Eurasia, thereby accommodating the collision between Arabia and Eurasia. This motion is mostly taken up by strike-slip deformation along the North and East Anatolian Faults. The Sea of Marmara lies over the direct westward continuation of the North Anatolian Fault zone. Just east of the Sea of Marmara, the North Anatolian Fault splits into three strands, two of which continue into the sea. While the locations of the faults are well constrained on land, it has not yet been determined how the deformation is transferred across the Sea of Marmara, onto the faults on the west coast of Turkey. We present results from a seismic reflection survey undertaken to map the faults as they continue through the three deep Marmara Sea basins of Çlnarclk, Central Marmara and Tekirdag, in order to determine how the deformation is distributed across the Sea of Marmara, and how it is taken up on the western side of the sea. The data show active dipping faults with associated tilting of sedimentary layers, connecting the North Anatolian Fault to strike-slip faults that cut the Biga and Gallipoli Peninsulas.     

洮河水系流域地貌特征及其构造指示意义

通过数字高程模型(DEM)的空间分析技术,系统提取研究区洮河水系流域盆地典型的河流地貌参数,并利用活动造山带地区发育的基岩河道纵向剖面形态等典型参数,分析洮河水系流域盆地地貌发育不对称性特征及洮河在岷县流向的急剧转变成因。研究表明洮河上游南岸水系较北岸水系形状指数高、流域面积大、水系发育更成熟,下游东岸河流河长较短、流域面积小、形状指数低于西岸,西岸水系更发育,且上游流域要比下游河道平缓,水系的相对落差更低,发育更成熟,表明上游河道形成时间早于下游河道。临潭—宕昌断裂带的逆冲隆升作用是造成洮河上、下游水系形态差异的主要原因。岷县东侧山脉的快速隆起致使古洮河被截断,之后被东北侧河流溯源侵蚀,切穿西秦岭北缘构造带,进行河流袭夺,从而形成了现今的洮河。最后探讨了对青藏高原东北端晚新生代以来的构造响应。     

东海陆架盆地伸展率和压缩率及构造跃迁

东海陆架盆地位于欧亚板块的东南缘和西太平洋活动大陆边缘,本文选取了东海陆架盆地主要凹陷的17条地震剖面,采用平衡剖面技术,计算了主要凹陷新生代不同演化阶段的伸展率和压缩率。分析表明,东海陆架盆地构造演化总体由西向东跃迁。晚白垩世至晚古新世东海陆架盆地裂陷中心在西部坳陷带,始新世东迁至东部坳陷带,上新世东迁至东海陆架盆地东侧的冲绳海槽盆地。古新世中后期东海陆架盆地西部坳陷带北侧昆山凹陷反转;中新世东部坳陷带的西湖凹陷反转。东海陆架盆地西部坳陷带与东部坳陷带构造演化不同,证明了东海陆架盆地的东西分带。西部坳陷带北部的长江坳陷和南部的台北坳陷构造演化不同,东部坳陷带北部的西湖凹陷和南部的钓北凹陷构造演化不同,证明了东海陆架盆地的南北分块。     

Structural evolution of the '41st parallel zone': Tyrrhenian Sea

The present study is based on the interpretation of more than 1300 km of 16 kJ sparker seismic profiles recorded in July 1990, during the Cruise T-41 of the Geological Institute of Urbino. The investigated area extends along the 41st parallel in the central Tyrrhenian Sea between the northern Sardinian margin to the west and the Latium–Campanian margin to the east. This zone, situated on continental crust, marks the boundary between the northern Tyrrhenian and the southern Tyrrhenian domains. A kinematic reconstruction is presented, based on the age-dating of the recognized structures (i.e. normal faults, reverse faults, anticline and flower structures). The evolution of the ‘41st parallel zone’ can be described in terms of polyphase tectonics characterized by different orientations of the stress field during time. The direction of the normal fault-trends, turned clockwise, striking NE–SW in the late Tortonian–Messinian, E–W in the early Pliocene, NNW–SSE in the late Pliocene and N–S during the Quaternary. The concurrence of compressional and strike-slip deformations suggests oblique shear motions across the 41st parallel. The occurrence of late Pliocene–Quaternary tectonic activity in the northern Tyrrhenian Sea, locally characterized by inversion tectonics, suggests active mechanisms (intraplate compression?) superimposed on the post-rift subsidence.     

The Neogene and Lower Pleistocene crags of Upper Normandy: Biostratigraphic revision and paleogeographic implications

The biostratigraphic revision of the benthic foraminifera present in the coastal Cenozoic quartzose and shelly sands (crags) at Fécamp and Valmont (Seine-Maritime) reveals Early Pliocene (Fécamp) and Early Pleistocene (Valmont) ages. The Tortonian-Messinian thanatocœnosis contained in the Fécamp Crag shows the presence of a former bryozoan-rich platform on the floor of the Channel that was reworked during the Lower Pliocene transgression. Tortonian-Messinian and Lower Pliocene deposits have been found in Belgium, England, Brittany, and at Fécamp, but are absent in Cotentin (North-West Normandy), which was uplifted at this period. The Lower Pleistocene tidal sands and crags described in Cotentin, Upper Normandy and the southern North Sea Basin indicate a marine passage between the Channel and the North Sea.     

北黄海盆地东部坳陷中新生代构造演化

在最新二维地震资料解释的基础上,对北黄海盆地东部坳陷的重要不整合面进行了研究,共识别出了4个重要不整合面;利用声波时差法和构造横剖面法,恢复了两期重要不整合面的剥蚀厚度;同时根据重磁资料及精细地震解释,对北黄海盆地东部坳陷的断裂特征作出了初步的研究,分析了主要断裂的形成期次及活动时间。最终,结合地层的分布特征及钻井资料,将北黄海盆地东部坳陷的构造演化史分为5个阶段。     

Evolution and strike variability of early post-rift deep-marine depositional systems: Lower to Mid-Cretaceous, North Viking Graben, Norwegian North Sea

The controls and development of early-post-rift, deep-water depositional systems are poorly understood due to their commonly deeply-buried nature. As a consequence, in the subsurface there is usually a lack of well penetrations and/or weak seismic imaging. At outcrop, early post-rift strata have commonly been deformed beyond reasonable recognition by later inversion tectonics. In contrast to these systems, the North Viking Graben shows a well-imaged Cretaceous early post-rift package with good well control and little effect from inversion. Therefore, this paper examines the early post-rift, deep-water depositional systems of the North Viking Graben to determine the controls on their stratigraphic position, geometry and evolution, and thus provide an analogue for comparable systems. Greater understanding of such systems will allow for the enhanced prediction of reservoir units in the subsurface and development of new play models since post-rift intervals are generally under-explored.The basin configuration inherited by the Cretaceous early post-rift in the northern North Sea was set up by Permo-Triassic and Late Jurassic rifting. In the North Viking Graben this established considerable along-strike variability, resulting in a northern basin segment surrounded by steep slopes and faulted-bounded structural highs and a southern basin segment margined by slopes with noticeably gentler gradients. Associated with the Cretaceous post-rift is an overall transgressional trend, which drowned local source areas, resulting in prevalent carbonate and hemipelagic mudstone deposition in the basins. In the North Viking Graben, the uplifted Oseberg fault-block provided the sub-aerial clastic source area until it was submerged in the early Upper Cretaceous.The early post-rift infill of the North Viking Graben was divided into four key seismic stratigraphic units (K1, K2, K3 and K4) using an integration of seismic and well data. Inside this stratigraphic framework, the depositional systems within each K-unit were resolved from characteristic seismic facies, amplitude anomalies, relationship with adjacent reflections, and geomorphologies. In the northern basin segment, the early post-rift stratigraphy contains basin-floor fans, a channel complex and a shoreline-like geometry, whereas the southern basin segment is solely characterised by hemipelagic and carbonate deposition. This spatial variability indicates that one of the dominant controls on the development of the early post-rift depositional systems in the North Viking Graben was the inherited syn-rift fault-controlled topography. The steep slopes bounding the northern basin segment aided the delivery of sediment from the sub-aerial Oseberg source area to the graben whereas the submerged, gentle slopes in the southern basin segment were relatively sediment-starved.Long- and short-term changes in relative sea-level also heavily influenced the evolution of the early post-rift basin stratigraphy. Short-term relative sea-level fall allowed basin-floor fan emplacement whereas short-term relative sea-level stand-still favoured deposition of a channel complex. Deposition of the shoreface-like geometry is associated with a short-term relative sea-level rise. This temporal difference in the style and scale of the depositional systems is also interpreted to reflect the gradual denudation and drowning of the Oseberg source area. Regional short-term trangressive and anoxic events in the northern North Sea further influenced the early post-rift strata, resulting in the deposition of stratigraphic units that can be correlated across the North Sea.     

Morphological and structural relations in the Galilee extensional domain, northern Israel

The Lower Galilee and the Yizre'el Valley, northern Israel, are an extensional domain that has been developing since the Miocene, prior and contemporaneously to the development of the Dead Sea Fault (DSF). It is a fan-shaped region bounded in the east by the N–S trending main trace of the DSF, in the north by the Bet-Kerem Fault system, and in the south by the NW–SE trending Carmel Fault. The study area is characterized by high relief topography that follows fault-bounded blocks and flexures at a wavelength of tens of km. A synthesis of the morphologic–structural relations across the entire Galilee region suggests the following characteristics: (1) Blocks within the Lower Galilee tilt toward both the southern and northern boundaries, forming two asymmetrical half-graben structures, opposite facing, and oblique to one another. (2) The Lower Galilee's neighboring blocks, which are the Upper Galilee in the north and the Carmel block in the southwest, are topographically and structurally uplifted and tilted away from the Lower Galilee. (3) The southern half-graben, along the Carmel Fault, is topographically and structurally lower than the northern one. Combining structural and geological data with topographic analysis enables us to distinguish several stages of structural and morphological development in the region. Using a semi-quantitative evolutionary model, we explain the morpho-structural evolution of the region. Our results indicate that the Galilee developed as a set of two isostatically supported opposite facing half-grabens under varying stress fields. The southern one had started developing as early as the early Miocene prior to the formation of the DSF. The northern and younger one has been developing since the middle Pliocene as part of the extension process in the Galilee. Elevation differences between the two half-grabens and their bounding blocks are explained by differences in isostatic subsidence due to sedimentary loading and uplift of the northern half-graben due to differential influences of the regional folding.     

The geology and morphology of the Antakya Graben between the Amik Triple Junction and the Cyprus Arc

In southeastern Turkey, the NE-trending Antakya Graben forms an asymmetric depression filled by Pliocene marine siliciclastic sediment, Pleistocene to Recent fluvial terrace sediment, and alluvium. Along the Mediterranean coast of the graben, marine terrace deposits sit at different elevations ranging from 2 to 180 m above present sea level, with ages ranging from MIS 2 to 11. A multisegmented, dominantly sinistral fault lying along the graben may connect the Cyprus Arc in the west to the Amik Triple Junction on the Dead Sea Fault (DSF) in the east. Normal faults, which are younger than the sinistral ones, bound the graben’s southeastern margin. The westward escape of the continental ?skenderun Block, delimited by sinistral fault segments belonging to the DSF in the east and the Eastern Anatolian Fault in the north caused the development of a sinistral transtensional tectonic regime, which has opened the Antakya Graben since the Pliocene. In the later stages of this opening, normal faults developed along the southeastern margin that caused the graben to tilt to the southwest, leading to differential uplift of Mediterranean coastal terraces. Most of these normal faults remain active. In addition to these tectonic movements, Pleistocene sea level changes in the Mediterranean affected the geomorphological evolution of the area.     

古岩溶流域内地表河与地下河成因联系与储层特征——以塔河油田奥陶系岩溶为例

在岩溶缝洞储层精细描述过程中,利用钻井校正地震的方法恢复岩溶末期的岩溶地貌,发现塔河油田奥陶系岩溶区内东西两侧发育由走滑断裂形成的地貌高带（分水岭）,其间为一向南开口的喇叭口状洼地,南接岩溶盆地;利用钻井、测井与地震综合解释方法,发现洼地北部较陡（坡度为2.9°左右）、南部较缓（坡度为1.5°）,发育由众多支流汇聚的2条岩溶水系,西侧一条在北部以地表河为主,在南部转入地下河,东面一条地表河与地下河交替发育,由3段地表河和2段地下河组成。由于强烈的侵蚀与溶蚀作用,形成了不同规模及充填物的5种地表河,但多数地表河内没有发现河流砂岩充填,只有岩溶湖泥灰岩沉积;而地下河溶洞内充填了大量的砂岩和泥岩,成为重要的油气储层。地表河原本是有砂泥沉积的,当下游发育地下河时,洪水把原有的砂泥岩冲入地下河,形成了溶洞砂泥岩沉积,除少数下游地表河残留砂泥岩外,塔河地区奥陶系岩溶地表河基本不存在砂质储层。