The role of basement tectonic reactivation on the structural evolution of Campos Basin,offshore Brazil: Evidence from 3D seismic analysis and section restoration

The structural analysis of regional 3D seismic data shows evidence of long-term tectonic inheritance in Campos Basin, offshore Brazil. Main Lower Cretaceous rift structures controlled themselves by strike-slip deformation belts related to Proterozoic orogenic events, have been episodically reactivated during the divergent margin phase of Campos Basin, from the Albian to the Miocene. Balanced cross-sections of major salt structures indicate that such tectonic reactivations have been controlling thin-skinned salt tectonics, triggering pulses of gravitational gliding above the Aptian salt detachment. Additionally, major basin features like the Neogene progradation front and the salt tectonic domains are constrained by the main Proterozoic orogenic trends of the Ribeira Belt (NE–SW) and the Vitória-Colatina Belt (NNW–SSE). As the basement involved structures observed in Campos Basin can be attributed to general geodynamic processes, it is suggested that basement tectonic reactivation can be as relevant as isostatic adjustment and detached thin-skinned tectonics on the structural evolution of divergent margin settings.     

Miocene-to-recent structure and basinal architecture along the Central Range strike-slip fault zone, eastern offshore Trinidad

Previous GPS-based geodetic studies and onland paleoseismologic studies in Trinidad have shown that the 50-km-long, linear, onland segment of the Central Range fault zone (CRFZ) accommodates at least 60% of the total rate of right-lateral displacement (∼20 mm/yr) between the Caribbean and South American plates. 2D and 3D seismic reflection data from a 60-km-long and 30-km-wide swath of the eastern shelf of Trinidad (block 2AB) were used to map the eastern offshore extension of this potentially seismogenic and hazardous fault system and to document its deeper structure and tectonic controls on middle Miocene to recent clastic stratigraphy. Two unconformity surfaces and seafloor were mapped using 3D seismic data to generate isochron maps and to illustrate the close control of the CRFZ and associated secondary faults on small, clastic basins formed along its anastomosing strands and the east-west-striking North Darien Ridge fault zone (NDRFZ) that exhibits a down-to-the-north normal throw. Mapped surfaces include: 1) the middle Miocene angular unconformity, a prominent, regional unconformity surface separating underlying thrust-deformed rocks from a much less deformed overlying section; this regional unconformity is well studied from onland outcrops in Trinidad and in other offshore areas around Trinidad; 2) a Late Neogene angular unconformity developed locally within block 2AB that is not recognized in Trinidad; and 3) the seafloor of the eastern Trinidad shelf which exhibits linear scarps for both the CRFZ and the east-west-striking North Darien Ridge fault zone. Clastic sedimentary fill patterns identified on these isochron maps indicate a combined effect of strike-slip and reverse faulting (i.e., tectonic transpression) produced by active right-lateral shear on the CRFZ, which is consistent with the obliquity of the strike of the fault to the interplate slip vector known from GPS studies in onland Trinidad. The NDRFZ and a sub-parallel and linear family of east-west-striking faults with normal and possibly transtensional motions also contributed to the creation of accommodation space within localized, post-middle Miocene clastic depocenters south of the CRFZ.     

莱州湾凹陷东部新生代走滑构造特征及油气勘探意义

莱州湾凹陷位于渤海南部海域,为中生界基底之上发育的新生代半地堑.郯庐断裂带分东西两支穿过莱州湾凹陷东部,在新生代盖层中表现出渤海最复杂最典型的为NNE向的右旋走滑断裂特征.其中东支断裂在渐新世以后活动强烈,发育多条NNE向走滑断层及NE向伴生断层组成的复杂断裂带.走滑断裂带内断层展布符合右旋单剪作用下的脆性走滑剪切模式,地震方差切片存在右旋运动拖拽断裂证据.通过对主断裂活动期次分析表明,研究区主要有三期大的构造活动,同时形成了三期构造反转.应力分布的局域性导致了形变特征的差异性,产生了褶皱、挤压反转、掀斜断块、花状构造等典型的构造类型.研究区首次利用三维地震资料对本区构造特征进行了分析,研究认为走滑活动形成了良好的构造背景、优越的油源及运移等成藏条件,具有较大的油气勘探潜力.     

Structural evolution of the Kopeh Dagh fold-and-thrust belt (NE Iran) and interactions with the South Caspian Sea Basin and Amu Darya Basin

We present a detailed stratigraphic and structural study of the Kopeh Dagh fold-and-thrust belt in NE Iran, which is an investigation of the complex polyphased tectonic history of this belt and its links with the adjacent South Caspian Sea and Amu Darya basins. Based on numerous field surveys, a large amount of 2D and 3D seismic data, borehole data and more than 150 new biostratigaphic datings, a new detailed biostratigraphic chart and 4 main regional cross-sections illustrate the importance of lateral facies variations and structural inheritance in the present-day structure of the belt.After the Cimmerian orogeny corresponding to the closure of the Paleotethys Ocean in Late Triassic/Early Jurassic times, a Middle Jurassic post-collisional rifting event was associated with the deposition of one of the main source rocks of the Kopeh Dagh and the Amu Darya Basin (Kashafrud Formation). Following this rifting event, over 7 km of sediments were accumulated until the Tertiary above a regional post-Triassic unconformity. The occurrence of local uplifts during the Late Cretaceous-Early Paleocene is interpreted as a consequence of regional-scale modification of plate-slab coupling in the Neotethys subduction zone. The main inversion of the Kopeh Dagh occurred at Late Eocene times, when the far-field deformation developed in Eurasia as a consequence of the locking of the Neo-Tethys subduction. This folding phase is sealed in the western part of the belt by a major Eocene-Oligocene unconformity at the base of the thick sedimentary series belonging to the South Caspian Sea Basin. The bulk of sedimentary infill in the South Caspian Sea Basin is Oligocene and younger, and it is probably related to syn-compressional downward flexure of the resistant basement basin at the onset of the Alpine phase. In the eastern part of the Kopeh Dagh, this deformation is characterized by Middle Jurassic graben inversion with evidence of forced folding, short-cuts and as well by larger scale basement uplifts. In contrast, the northwestern part of the belt shows thrust faults involving basement and fault-propagation folds within the sedimentary sequence. The Kopeh Dagh presents tectonic structures that are parallel to the Paleotethys suture zone, which emphasizes the importance of the structural inheritance and inversion processes during the structural evolution of the belt. Finally, a change from a mostly dip-slip to a mostly strike-slip tectonics occurred during the Pliocene within the Kopeh Dagh as a consequence of a major tectonic reorganization in North-East Iran.     

Recent structures in the Alboran Ridge and Yusuf fault zones based on swath bathymetry and sub-bottom profiling: evidence of active tectonics

The seafloor of the Alboran Sea in the western Mediterranean is disrupted by deformations resulting from convergence between the African and Eurasian plates. Based on a compilation of existing and new multibeam bathymetry data and high-resolution seismic profiles, our main objective was to characterize the most recent structures in the central sector, which depicts an abrupt morphology and was chosen to investigate how active tectonic processes are shaping the seafloor. The Alboran Ridge is the most prominent feature in the Alboran Sea (>130 km in length), and a key element in the Gibraltar Arc System. Recent uplift and deformation in this ridge have been caused by sub-vertical, strike-slip and reverse faults with associated folding in the most recent sediments, their trend shifting progressively from SW–NE to WNW–ESE towards the Yusuf Lineament. Present-day transtensive deformation induces faulting and subsidence in the Yusuf pull-apart basin. The Alboran Ridge and Yusuf fault zones are connected, and both constitute a wide zone of deformation reaching tens of kilometres in width and showing a complex geometry, including different active fault segments and in-relay folds. These findings demonstrate that Recent deformation is more heterogeneously distributed than commonly considered. A narrow SSW–NNE zone with folding and reverse faulting cuts across the western end of the Alboran Ridge and concentrates most of the upper crustal seismicity in the region. This zone of deformation defines a seismogenic, left-lateral fault zone connected to the south with the Al Hoceima seismic swarm, and representing a potential seismic hazard. Newly detected buried and active submarine slides along the Alboran Ridge and the Yusuf Lineament are clear signs of submarine slope instability in this seismically active region.     

Interaction between trench retreat and Anatolian escape as recorded by neogene basins in the northern Aegean Sea

The evolution of the North Aegean Sea is studied through the development of three deep basins: the North Aegean Trough, the North Skyros Basin and the Ikaria Basin. Bathymetric data, a 2D seismic dataset and the well-investigated stratigraphic records of the onshore deep basins of northern Greece and Western Turkey were used to make structural and seismic stratigraphic interpretations. The study area shows two sharp unconformities that correspond to the Eocene-Oligocene transition and the Miocene-Pliocene shift. These discontinuities were used as marker horizons for a more detailed structural and seismic stratigraphic interpretation resulting in the identification of several seismic units. A general seismic signature chart was established using onshore basin stratigraphy and well data, which was then used to constrain the ages of the different seismic units. The main features observed in the basins are interpreted as: 1) trans-tensional growth patterns in Pliocene and Quaternary sediments that combine NE–SW trending and steeply dipping fault zones that likely correspond to strike-slip corridors and E-W/WNW-ESE trending normal faults, 2) regional erosional truncations of Miocene sediments, likely related to the Messinian Salinity Crisis (MSC), 3) thick delta-turbidite deposits of Neogene age. Only the North Aegean Trough shows evidence of earlier development and polyphase deformation through inversion structures, and additional seismic units. Extension processes in the Aegean region have been driven by the Hellenic slab rollback since the middle Eocene. The widespread development of Neogene basins at the whole Aegean scale attests to a major tectonic change due to an acceleration of the trench retreat in the middle Miocene. The present study shows that the Neogene basins of the North Aegean Sea developed in dextral transtension with the northward migration of the associated NE-SW trending strike-slip faults. At regional scale, this tectonic pattern indicates that the westward escape of Anatolia started to interact with the trench retreat in the middle Miocene, around 10 Myr before the arrival of the North Anatolian Fault in the North Aegean Sea.     

南海琼东南盆地新生代构造层序研究

基于南海琼东南盆地到目前为止还没有一个统一的构造层序划分方案的问题,在前人研究工作基础上,通过大量的二维地震构造层序闭合解释,从地震不整合面和构造发育特征识别出发,对新生代主要构造层序进行详细解剖。进一步结合对南海北部琼东南盆地新生代二维地震数据的精细综合分析,重新厘定了其新生代构造层序,并进行了构造层序的识别和划分。结果表明：按古构造运动面可将盆地充填序列划分为上、中、下三个构造层序,分别对应于盆地演化的三个阶段性。着重论述了三个构造层序的结构特征、叠加构造样式、构造层序发育特征、层序分布特征、沉积体系类型和盆地断裂演化序列之间的关系等,以期为今后的研究奠定基础。     

南海裂陷盆地中斜向伸展及其油气勘探意义

利用海上钻井、地震等资料,重新认识南海珠江口盆地文昌B凹陷控凹边界南断裂构造变形史及动力学机制,探讨油气勘探意义。研究表明,渐新世—中新世,南断裂具有斜向伸展性质,在倾向剖面,断裂带发育挤压褶皱和破碎主位移带的构造样式;在走向剖面,相关地层呈"厚薄相间"分布。平面上,发育雁列式背斜与洼地共生、"马尾状"断裂体系和右阶斜列阶步断裂体系。斜向伸展动力学机制受控于区域伸展构造应力场与先存南断裂走向。南断裂渐新世—中新世斜向伸展变形,控制和影响了油气成藏要素、流体相态。     

南海北部琼东南盆地中央峡谷成因新认识

通过对区域构造断裂体系和逐渐连片的高分辨率三维地震资料的精细解析,认识到琼东南盆地中央峡谷的形成机制除了与晚中新世区域构造变动、大规模海平面下降、充足物源供给以及凹槽型古地形特征等因素相关之外,还存在另外一个非常重要因素:峡谷底部早期隐伏断裂带的存在。研究表明:琼东南盆地中央坳陷带发育平行于陆架坡折的大规模深水峡谷,峡谷底部发育大型走滑断层以及走滑断层派生出一系列次级断层形成的地层破碎带,认识到峡谷的形成、规模以及展布方向均受断裂带影响;相应地峡谷的充填及演化亦是受物源、海平面变化、重力流作用等多种因素共同作用和相互叠加的过程。从而为研究经历了裂陷期和坳陷期盆地演化过程形成的大型峡谷提供了科学依据。     

Tracing the middle strand of the North Anatolian Fault Zone through the southern Sea of Marmara based on seismic reflection studies

We studied the active deformation zone of the middle strand of the North Anatolian Fault Zone through the southern part of the Sea of Marmara by means of high-resolution as well as deep seismic reflection data. Our main objective was to investigate the active deformation within the uppermost sedimentary layers at high resolution as well as deeper sedimentary layers, focusing on the tectonic and stratigraphic setting between Gemlik and Bandırma. The middle strand of the North Anatolian Fault reaching the Gulf of Gemlik is a main fault which has a lazy-S shape in the Gulf of Gemlik, and extends westwards to Bandırma as a main fault which is an E–W-trending single right-lateral fault controlling the zone along the Gemlik and Bandırma sub-basins. Small-scale faults, consistent with a dextral shear regime, are present in the vicinity of the main fault. Several oblique fault groups parallel to the main fault were detected. The deformation in the Gulf of Gemlik is characterized by a series of synthetic and antithetic faults emanating from the main fault. The boundary faults in the Gulf of Gemlik have a compressive component, which indicates the sill areas of the gulfs of Gemlik and Bandırma to be push-up structures. Four seismic stratigraphic units were identified in the sediments of the gulfs of Gemlik and Bandırma, providing evidence of tectonic influence. The present tectonic structure between Gemlik and Bandırma is not a pull-apart structure. The microseismic study in this area has shown that fault planes are either strike-slip or compressional, and that the stress tensor is compatible with pure strike-slip in the E–W fault system.     

Investigation of Fethiye-Marmaris Bay (SW Anatolia): seismic and morphologic evidences from the missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone

New (2009) multi-beam bathymetric and previously published seismic reflection data from the NE-SW-oriented Fethiye Bay and the neighboring N-S-oriented Marmaris Bay off SW Anatolia were evaluated in order to interpret the seafloor morphology in terms of the currently still active regional tectonic setting. This area lies between the Pliny Trench, which constitutes the eastern sector of the subduction zone between the African and Eurasian plates in the Eastern Mediterranean, and the Fethiye-Burdur Fault Zone of the Anatolian Plate. The bathymetric data document the very narrow shelf of the Anatolian coast, a submarine plain between the island of Rhodes and Marmaris Bay, and a large canyon connecting the abyssal floor of the Rhodes Basin with Fethiye Bay. The latter are here referred to as the Marmaris Plain and Fethiye Canyon, respectively. Several active and inactive faults have been identified. Inactive faults (faults f1) delineate a buried basin beneath the Marmaris Plain, here referred to as the Marmaris Basin. Other faults that affect all stratigraphic units are interpreted as being active. Of these, the NE-SW-oriented Marmaris Fault Zone located on the Marmaris Plain is interpreted as a transtensional fault zone in the seismic and bathymetric data. The transtensional character of this fault zone and associated normal faults (faults f3) on the Marmaris Plain correlates well with the Fethiye-Burdur Fault Zone on land. Another important fault zone (f4) occurs along the Fethiye Canyon, forming the northeastern extension of the Pliny Trench. The transpressional character of faults f4 inferred from the seismic data is well correlated with the compressional structures along the Pliny Trench in the Rhodes Basin and its vicinity. These observations suggest that the Marmaris Fault Zone and faults f3 have evolved independently of faults f4. The evidence for this missing link between the Pliny Trench and the Fethiye-Burdur Fault Zone implies possible kinematic problems in this tectonic zone that deserve further detailed studies. Notably, several active channels and submarine landslides interpreted as having been triggered by ongoing faulting attest to substantial present-day sediment transport from the coast into the Rhodes Basin.     

南黄海盆地中部隆起海相上构造层分布及断裂系统特征

南黄海盆地中部隆起区发育2套海相构造层,以下志留统高家边组泥岩滑脱带为界可划分为海相上构造层和海相下构造层。海相上构造层构造相对较复杂,以冲断结构为主,褶皱及叠瓦状逆冲断裂发育。对南黄海盆地中部隆起区多道地震资料进行处理解释表明,中部隆起区广泛发育海相上构造层,平面上总体表现为自西向东厚度呈厚—薄—厚的沉积格局。断裂系统发育,以近EW向断裂最为发育,其次为NE向断裂,NW向断裂则较为零星。构造应力以挤压和走滑为主,主要发育挤压、压扭和张扭3种构造样式。     

Sequence stratigraphy and importance of syndepositional structural slope-break for architecture of Paleogene syn-rift lacustrine strata,Bohai Bay Basin,E. China

Sequence stratigraphy and syndepositional structural slope-break zones define the architecture of the Paleogene syn-rift, lacustrine succession in eastern China's Bohai Bay Basin. Jiyang, Huanghua and Liaohe subbasins are of particular interest and were our primary research objectives. Interpretation of 3D seismic data, well logs and cores reveals: One first-order sequence, 4 second-order sequences, and ten to thirteen third-order sequences were identified on the basis of the tectonic evolution, lithologic assemblage and unconformities in the subbasins of Bohai Bay Basin. Three types of syndepositional paleo-structure styles are recognized in this basin. They are identified as fault controlled, slope-break zone; flexure controlled, slope-break zone; and gentle slope.The three active structural styles affect the sequence stratigraphy. Distinct third-order sequences, within second-order sequences, have variable systems tract architecture due to structuring effects during tectonic episodes. Second-order sequences 1 and 2 were formed during rifting episodes 1 and 2. The development of the third-order sequences within these 2 second-order sequences was controlled by the active NW and NE oriented fault controlled, slope-break zones. Second-order sequence 3 formed during rifting episode 3, the most intense extensional faulting of the basin. Two types of distinctive lacustrine depositional sequence were formed during rifting episode 3: one was developed in an active fault controlled, slope-break zone, the other in an active flexure controlled, slope-break zone. Second-order sequence 4 was formed during the fourth episode of rifting. Syndepositional, fault- and flexure-controlled slope-break zones developed in the subsidence center (shore to offshore areas) of the basin and controlled the architecture of third-order sequences in a way similar to that in second-order sequence 3. Sequences in the gentle slope and syndepositional, flexure controlled slope-break zones were developed in subaerial region.Distribution of lowstand sandbodies was controlled primarily by active structuring on the slope-break zones, and these sandbodies were deposited downdip of the slope-break zones. Sand bodies within lowstand systems tracts have good reservoir quality, and are usually sealed by the shale sediments of the subsequent transgressive systems tract. They are favorable plays for stratigraphic trap exploration.     

Seismic imaging of a fractured gas hydrate system in the Krishna–Godavari Basin offshore India

Gas hydrate was discovered in the Krishna–Godavari (KG) Basin during the India National Gas Hydrate Program (NGHP) Expedition 1 at Site NGHP-01-10 within a fractured clay-dominated sedimentary system. Logging-while-drilling (LWD), coring, and wire-line logging confirmed gas hydrate dominantly in fractures at four borehole sites spanning a 500 m transect. Three-dimensional (3D) seismic data were subsequently used to image the fractured system and explain the occurrence of gas hydrate associated with the fractures. A system of two fault-sets was identified, part of a typical passive margin tectonic setting. The LWD-derived fracture network at Hole NGHP-01-10A is to some extent seen in the seismic data and was mapped using seismic coherency attributes. The fractured system around Site NGHP-01-10 extends over a triangular-shaped area of ∼2.5 km² defined using seismic attributes of the seafloor reflection, as well as “seismic sweetness” at the base of the gas hydrate occurrence zone. The triangular shaped area is also showing a polygonal (nearly hexagonal) fault pattern, distinct from other more rectangular fault patterns observed in the study area. The occurrence of gas hydrate at Site NGHP-01-10 is the result of a specific combination of tectonic fault orientations and the abundance of free gas migration from a deeper gas source. The triangular-shaped area of enriched gas hydrate occurrence is bound by two faults acting as migration conduits. Additionally, the fault-associated sediment deformation provides a possible migration pathway for the free gas from the deeper gas source into the gas hydrate stability zone. It is proposed that there are additional locations in the KG Basin with possible gas hydrate accumulation of similar tectonic conditions, and one such location was identified from the 3D seismic data ˜6 km NW of Site NGHP-01-10.     

Reef exploration in the East Sengkang Basin,Sulawesi, Indonesia

Reconnaissance seismic shot in 1971/72 showed a number of well defined seismic anomalies within the East Sengkang Basin which were interpreted as buried reefs. Subsequent fieldwork revealed that Upper Miocene reefs outcropped along the southern margin of the basin. A drilling programme in 1975 and 1976 proved the presence of shallow, gas-bearing, Upper Miocene reefs in the northern part of the basin. Seismic acquisition and drilling during 1981 confirmed the economic significance of these discoveries, with four separate accumulations containing about 750 × 10⁹ cubic feet of dry gas in place at an average depth of 700 m. Kampung Baru is the largest field and contains over half the total, both reservoir quality and gas deliverability are excellent. Deposition in the East Sengkang Basin probably started during the Early Miocene. A sequence of Lower Miocene mudstones and limestones unconformably overlies acoustic basement which consists of Eocene volcanics. During the tectonically active Middle Miocene, deposition was interrupted by two periods of deformation and erosion. Carbonate deposition became established in the Late Miocene with widespread development of platform limestones throughout the East Sengkang Basin. Thick pinnacle reef complexes developed in the areas where reef growth could keep pace with the relative rise in sea level. Most reef growth ceased at the end of the Miocene and subsequent renewed clastic sedimentation covered the irregular limestone surface. Late Pliocene regression culminated in the Holocene with erosion. The Walanae fault zone, part of a major regional sinistral strike-slip system, separates the East and West Sengkang Basins. Both normal and reverse faulting are inferred from seismic data and post Late Pliocene reverse faulting is seen in outcrop.     

Garzón Massif basement tectonics: Structural control on evolution of petroleum systems in upper Magdalena and Putumayo basins,Colombia

The Garzón Massif, is an active Laramide style basement uplift flanked by the Upper Magdalena Valley (UMV) and the Putumayo Basin. In this paper we use new gravity, magnetic, well and seismic data for the first geophysical interpretation of the Garzón Massif. The Garzón/Algeciras fault has been previously interpreted as a right-lateral strike-slip fault. The new seismic, well, and gravity data demonstrates that the Garzón fault is also a low-angle (12–17°) Andean age fault thrusting PreCambrian basement 10–17 km northwestward over Miocene sediments of the UMV in a prospective footwall anticline.The new geophysical data as well as previous field mapping were used to produce the first gravity and magnetic maps and retrodeformable structural cross section of the northern Garzón Massif. The new model distinguishes for the first time distinct episodes of “thin-skinned” and “thick-skinned” deformation in the Garzón Massif. The model indicates approximately 43 km of Early to Middle Miocene shortening by “thin-skinned” imbricate thrusting contemporaneous with the uplift of the nearby southern Central Cordillera (∼9–16 Ma) and the main hydrocarbon expulsion event for the UMV and Putumayo Basin. This was followed by at least 22 km of Late Miocene (3–6 Ma) “thick-skinned” Andean shortening and 7 km of uplift on the symmetrical Garzón thrust and a SE-verging basement thrust fault zone. The Andean uplift interrupted and exposed the hydrocarbon migration pathways to the Putumayo Basin.3-D volume fracture analysis was used for the first time in this paper together with the first seismic and well data published for the Topoyaco and Miraflor structures to test closure models for the Topoyaco foothills. Intense fracturing is observed in the Topoyaco basement monocline from the near-surface to depths of over 3.5 km. The high level of fracturing permitted freshwater flushing and oil biodegradation and hydrocarbon escape. In contrast, the Miraflor-1 well, located just southwest of the Topoyaco block, tested light gravity oil and is sealed from groundwater flushing and biodegradation by a backthrust.     

Structural patterns of the Lake Erçek Basin,eastern Anatolia (Turkey): evidence from single-channel seismic interpretation

This study presents an analysis of the single-channel high-resolution shallow seismic reflection data from Lake Erçek, eastern Anatolia, to provide key information on the deformational elements, on the fault patterns and on the overall tectonic structure of the Lake Erçek Basin. High-resolution seismic data reveal major structural and deformational features, including N–S trending normal faults and W–E trending reverse faults bounding the Lake Erçek Basin, basement highs and folded structures along the marginal sections of the lake. The N–S trending normal faults asymmetrically control the steep western margin and the gentle eastern deltaic section, while the W–E trending reverse faults appear at the northern and southern margins. The N–S trending normal faults, half-graben structure, and the gradual thickening of sediments in the Erçek Basin toward the fault scarps strongly suggest an extensional tectonic regime resulting from an N–S compression. The Erçek Basin is an extension-controlled depocenter; it is a relatively undeformed and flat-lying deep Basin, forming a typical example of the half-graben structure. The N–S trending normal faults appear to be currently active and control the lake center and the E-delta section, resulting in subsidence in the lake floor. In the N- and S-margins of the lake, there is evidence of folding, faulting and accompanying block uplifting, suggesting a significant N–S compressional regime that results in the reverse faulting and basement highs along the marginal sections. The folding and faulting caused strong uplift of the basement blocks in the N- and S- margins, subsequently exposing the shelf and slope areas. The exposed areas are evident in the erosional unconformity of the surface of the basement highs and thinned sediments. The tilted basement strata and subsequent erosion over the basement block highs suggest prominent structural inversion, probably long before the formation of the lake. New high-resolution seismic data reveal the fault patterns and structural lineaments of the Lake Erçek and provide strong evidence for an ongoing extension and subsidence. The present study provides new structural insights that will support future tectonic and sedimentary studies and the development of strategies related to active earthquake faults and major seismic events in the region of Lake Erçek.     

Overview of the subsurface structural pattern of the Paris Basin (France): Insights from the reprocessing and interpretation of regional seismic lines

The study presents the methodology used by the French Geological Survey (BRGM) for the building, reprocessing and interpretation of selected regional seismic lines in the Paris intracratonic basin (France): the 14 constructed E-W and N-S regional transects represent a total of 2,516 km length, and are based on the merge of 240 seismic single profiles recorded by petroleum operators between 1971 and 1995. The regional lines have been selected to cross the main oil fields of the Paris Basin, as well as high potential areas for oil exploration. A first difficulty was to recover the raw data necessary to build-up the regional transects. The signal reprocessing, harmonization and merge of the single seismic lines, constituent of the regional transects, are then described; these operations represent the cornerstone of the study. We put the emphasis on the primary static corrections, as the targeted structures are commonly spatially associated with large seismic velocity variations in the upper Cretaceous chalk and Tertiary sedimentary cover.The interpreted regional transects definitely give complementary information to the existing studies, which generally lack seismic (and therefore structural) data: we give an overview of the main structural and geometrical features of the Paris Basin: inversion structures, major unconformities, as well as Permo-Carboniferous basins. We also describe the structural pattern, and show the close relationships between the faults geometry, the faults density, and the geological evolution of the Paris Basin: we distinguish (1) few large-scale polyphase faults, with a Variscan origin, representing the first order structural frame of the Paris Basin; (2) monophase normal faults, with strike-slip features, representing the subsurface prolongation of Cenozoic grabens cropping out in the neighbourhood; (3) deep normal faults, sealed by the base Calcareous Dogger sequence, related to the Permo-Liassic extensional tectonic regime. This large-scale view of the Paris Basin has highlighted several potential exploration targets.     

南黄海盆地古潜山分类及构造特征

南黄海是下扬子的主体,奠基于晋宁期变质基底之上,构造演化历经南华纪—早、中三叠世海相地层发育期、晚白垩世—古近纪箕状断陷发育期和新近纪—第四纪坳陷发育期,为一典型地台-断陷-坳陷多层结构的复合盆地。盆地历经多次构造运动改造,古潜山发育,类型多样。在总结前人对古潜山研究的基础上,结合南黄海新近采集的二维地震剖面,对该地区古潜山类型进行了系统划分,并对典型古潜山的构造特征及生储盖匹配关系进行了初步描述。根据成因划分为剥蚀型潜山、拉张型潜山、挤压型潜山和复合型潜山四大类,每一类又可根据形态划分出剥蚀残丘型潜山、拉张翘倾断块型潜山、拉张断阶型潜山、拉张断垒型潜山、挤压褶皱型潜山、拱张褶皱型潜山和褶皱—断块复合型潜山等类型。南黄海盆地古潜山的发育具有分带性,按盆地中潜山的构造位置,分为凸起潜山带、陡坡潜山带、洼陷潜山带和缓坡潜山带,每一构造带发育了不同类型潜山。研究表明南黄海古生界和中生界古潜山数量众多,规模较大,是南黄海地区实现油气突破的一种重要油气藏类型。     

莱州湾地区郯庐断裂带的构造特征及其新生代演化

郯庐断裂带中段分东西两支从莱州湾进入渤海,在莱州湾地区的构造特征与演化历史一直鲜为人知。通过对横穿研究区的两条地震测线的解释和分析,揭示了该区郯庐断裂带中段在研究区的构造差异,研究表明郯庐断裂带东西两支在该研究区表现出不同的断裂性质,西支断裂表现为正断层,东支断裂表现为走滑断层。郯庐断裂是本研究区的主控断裂,通过对本地区地层形态及其组合、断层的剖面形态和空间展布规律的深入研究,揭示了郯庐断裂带在莱州湾地区新生代以来的构造演化历史:古新世—始新世的伸展阶段、渐新世—中新世早期的挤压和右行走滑阶段、中新世中晚期至今的稳定发展阶段,这几个不同时期的演化阶段主要受太平洋板块运动的方向和速度变化的控制。