南亚地区含油气盆地类型及资源潜力分析

南亚地区经历冈瓦纳陆内裂谷、冈瓦纳裂解与板块漂移及印度板块与欧亚板块的陆-陆碰撞复杂的构造演化,最终形成了以被动大陆边缘盆地为主的,包括克拉通盆地和俯冲-碰撞带盆地在内的3类沉积盆地,其中被动大陆边缘盆地分布广泛,形成了南亚地区的一个主要盆地群。本文通过对南亚盆地生、储、盖等石油地质条件分析,研究不同盆地类型的油气成藏特征。根据盆地的剩余可采储量和远景资源量对南亚地区的资源潜力进行分析,认为被动大陆边缘盆地油气资源潜力最大,并优选出奎师那-哥达瓦里盆地、孟买盆地和科弗里盆地3个有利盆地。     

Heat flow and thermal evolution of the lithosphere of the Black Sea basin

In most of the studies devoted to the analysis of the thermal regime of the Black Sea basins, the high sedimentation rate is regarded to be the principal reason for the low values of the surface heat flow as compared to the deep flow. We used the basin modeling technique for a more detailed assessment of this issue with regard to the new geological and geophysical data on the age and structure of the sedimentary cover and basement of the Black Sea basins. The use of enhanced seismic data, together with a more accurate estimation of the age limits of the sedimentary sequences in the region, allowed us to refine the results of the previous studies. Based on the calculations performed for an actual cross section with actual properties of the sedimentary rocks under compaction and the basement rocks, it is shown that any version of the sedimentation and evolution of the basin compatible with the geological and geophysical data available lead to heat flow values that are significantly greater than those actually observed. Our analysis proves that the sedimentation alone, as was implied in the previous studies, cannot explain the decrease in the deep heat flow at the floor surface down to values of about 34 mW/m². It is shown that the temperature influence of the invasion of dense though heated waters of the Mediterranean Sea that occurred about 7000 years ago helps one to explain the low present-day heat flow values in the deep-water parts of the Western and Eastern basins of the Black Sea. The application of the basin modeling technique allowed us to pose a version of the thermal evolution of the lithosphere in the Western basin of the Black Sea compatible with the high heat flow at the end of the Cretaceous, with three stages of subsidence of the sea floor down to its present-day depths, and with the low heat flow values measured in the basin. According to the geophysical data, this version implies a relatively high-temperature present-day thermal regime in the basin’s lithosphere with a lithosphere thickness of about 60 km.     

南海海域新生代沉积盆地的油气资源

南海新生代经历过大陆张裂与分离、海底扩张和地块碰撞等构造演化历史,南海北部为被动大陆边缘,南部是碰撞挤压边缘,东部为俯冲聚敛边缘,西部是走滑边缘。在这种构造体制下,形成了许多沉积盆地。北部和西部边缘上发育着张性沉积盆地和走滑拉张盆地;在南部边缘上,其北部发育着张性盆地,南部为挤压环境下形成的盆地,如前陆盆地、前孤盆地;东部边缘上发育着前孤盆地。目前油气勘探实践证明,南海南部的油气资源比北部丰富。究其原因,南海北部为被动大陆边缘,张性沉积盆地的烃源岩体积较小,而南部挤压环境下形成的沉积盆地的烃源岩体积大;北部的地热流较南部小,因此地温梯度也较小,故南部边缘烃源岩的成熟度比北部高;由于南部边缘处于挤压构造环境,在沉积盆地中形成了许多挤压构造,而北部边缘一直处于张性构造环境,形成的构造较少且较小;同时,南部边缘沉积盆地中,烃源岩生烃与构造形成在时间上搭配较好。因此,在南海南部边缘沉积盆地中形成了许多大型油气田,而南海北部边缘沉积盆地中,大型油气田较少,中小型油气田较多。     

Seismic stratigraphy and structure of the Northland Plateau and the development of the Vening Meinesz transform margin,SW Pacific Ocean

The Northland Plateau and the Vening Meinesz “Fracture” Zone (VMFZ), separating southwest Pacific backarc basins from New Zealand Mesozoic crust, are investigated with new data. The 12–16 km thick Plateau comprises a volcanic outer plateau and an inner plateau sedimentary basin. The outer plateau has a positive magnetic anomaly like that of the Three Kings Ridge. A rift margin was found between the Three Kings Ridge and the South Fiji Basin. Beneath the inner plateau basin, is a thin body interpreted as allochthon and parautochthon, which probably includes basalt. The basin appears to have been created by Early Miocene mainly transtensive faulting, which closely followed obduction of the allochthon and was coeval with arc volcanism. VMFZ faulting was eventually concentrated along the edge of the continental shelf and upper slope. Consequently arc volcanoes in a chain dividing the inner and outer plateau are undeformed whereas volcanoes, in various stages of burial, within the basin and along the base of the upper slope are generally faulted. Deformed and flat-lying Lower Miocene volcanogenic sedimentary rocks are intimately associated with the volcanoes and the top of the allochthon; Middle Miocene to Recent units are, respectively, mildly deformed to flat-lying, calcareous and turbiditic. Many parts of the inner plateau basin were at or above sea level in the Early Miocene, apparently as isolated highs that later subsided differentially to 500–2,000 m below sea level. A mild, Middle Miocene compressive phase might correlate with events of the Reinga and Wanganella ridges to the west. Our results agree with both arc collision and arc unzipping regional kinematic models. We present a continental margin model that begins at the end of the obduction phase. Eastward rifting of the Norfolk Basin, orthogonal to the strike of the Norfolk and Three Kings ridges, caused the Northland Plateau to tear obliquely from the Reinga Ridge portion of the margin, initiating the inner plateau basin and the Cavalli core complex. Subsequent N115° extension and spreading parallel with the Cook Fracture Zone completed the southeastward translation of the Three Kings Ridge and Northland Plateau and further opened the inner plateau basin, leaving a complex dextral transform volcanic margin.     

Interaction between diapirism and sediment loading at the shelf-slope boundary,northwest Gulf of Mexico

During the last low stand of sea level, rivers and streams drained across the present northwestern Gulf of Mexico continental shelf depositing sediments in several shallow-water deltas near the present shelf-slope boundary. The weight of these wedges of prograded sediments triggered or augmented both subsidence of local depositional basins and upward movement of diapiric material around the basin edges. A depositional basin off the southwestern Louisiana coast records migration of the basinal axis during late Pleistocene and Holocene time indicating relative growth of diapirs along the basin margin throughout the most recent geological record.     

A Mid-Miocene erosional unconformity from the Durban Basin,SE African margin: A combination of global eustatic sea level change,epeirogenic uplift,and ocean current initiation

Erosional unconformity surfaces are key indicators for the variations in eustatic sea level, ocean dynamics and climatic conditions which significantly affect depositional environments of sedimentary successions. Using a dense grid of 2D seismic data, we present new evidence from a frontier basin, the offshore Durban Basin, of a mid-Miocene age erosional unconformity that can be correlated with analogous horizons around the entire southern African continental margin.In the Durban Basin, this unconformity is typified by the incision of a mixed carbonate-siliciclastic wedge and ramp margin by a series of submarine canyons. Epeirogenic uplift of southern Africa characterised this period, with erosion and sediment bypass offshore concomitant with increases in offshore sedimentation rates. Although epeirogenic uplift appears to be the dominant mechanism affecting formation of the identified sequence boundary, it is postulated that an interplay between global eustatic sea-level fall, expansion of the east Antarctic ice sheets, and changes in deep oceanic current circulation patterns may have substantially contributed to erosion during this period.     

西非海岸盆地群油气勘探成果及勘探潜力分析

西非海岸盆地群包括塔尔法亚、塞内加尔、尼日尔三角洲、杜阿拉、里奥姆尼、加蓬、下刚果、宽扎、奥兰治、科特迪瓦、贝宁等11个主要沉积盆地,它们是冈瓦纳大陆裂解和中大西洋、南大西洋及赤道大西洋张开和漂移的结果,包括被动大陆边缘盆地和转换边缘盆地两种类型沉积盆地。通过利用IHS数据库资料,在系统总结西非海岸盆地群油气勘探成果基础上,划分其为早期勘探（1953年前）、储量快速增长（1954～1973年）、储量缓慢增长（1974～1994年）和深水勘探（1995年至今）四个油气勘探阶段,认为研究区油气发现主要与盆地勘探程度、油气勘探技术进步、资源国政治形势和全球经济有关;尼日尔三角洲和下刚果等重点盆地大油气田的发现直接推动了西非海岸盆地群油气储量和产量的增长;深水区是西非海岸盆地群今后寻找大发现的潜力区,而大陆架和陆上则是重点挖潜地区。     

末次冰期以来南海东北部陆源有机碳埋藏通量演变:海平面和季风驱动

大陆边缘盆地是大陆风化剥蚀产物的主要沉积汇,其中有机碳的埋藏通量及其控制机制的研究对于理解全球碳循环具有重要科学意义。本研究基于南海东北部台西南盆地TWS-1岩芯的AMS14C测年、总有机碳、总氮含量和稳定碳同位素组成的分析,探讨了末次盛冰期23ka BP以来南海东北部陆源有机碳的来源、历史和影响机制。与潜在物源端元对比表明,台湾是研究站位沉积物陆源有机碳的主要物源,相对海源其贡献比例约为58%,陆源物质可能主要通过海底峡谷水道和低海平面时期陆架河流输入。重建的陆源有机碳通量在末次冰消期早期(19—13kaBP)和中全新世(7—4ka BP)期间有两个峰值,分别约0.16g/(cm2·ka)和0.09g/(cm2·ka)。综合分析表明,二者分别受控于冰期低海平面时期增强的陆架风化剥蚀和全新世季风强盛期降水驱动的古台湾岛剥蚀。我们的工作表明冰期-间冰期循环中海平面和季风分别驱动的大陆边缘有机碳埋藏可能对全球碳循环和大气CO2浓度演变有重要影响。     

东海新生代沉积盆地的类型和成盆期

东海新生代沉积厚度最大可达10km。分为三个发展时期。第一阶段从晚白垩世至中始新世,由于中国大陆向东濡散和掀斜断块作用,在大陆边缘由陆缘裂谷盆地转化为浅海沉积盆地。第二阶段从晚始新世至中中新世,由于喜马拉雅陆缘造山带的形成和中国大陆边缘的隆升联合作用结果,在大陆边缘由环绕大陆分布的带状地堑转化为前陆盆地。第三阶段从晚中新世至第四纪,由于太平洋板块向西俯冲,形成弧后断陷及弧前坳陷。从横向上看,不同性质和时代的沉积,由西向东,由老到新,依次排列。从盆地性质上看,由老到新,张性盆地和压性盆地交替形成,叠置在一起。因此不同时代和性质的盆地,具有不同的石油地质条件和油气成藏规律。     

西太平洋边缘海盆的形成与演化

从地球深部地幔流动引起的地质作用出发，结合裂谷的发展演化规律，认为地幔向东（或南东）的蠕散和流动促使亚洲大陆边缘地壳拉伸、变薄以致破裂，由大陆裂谷发展至弧后裂谷，形成西太平洋边缘海盆。最后提出边缘海盆发展演化的4个阶段，即：新生阶段（郯庐裂谷系）、幼年阶段（冲绳海槽）、青壮年阶段（日本海）和成熟阶段（南海）。     

Subsidence and evolution of Nigeria's continental margin: implications of data from Afowo-1 well

The Afowo-1 well is situated west of Lagos on the onshore part of the Dahomey basin. Biostratigraphic data from this exploratory well have been used to determine the subsidence history of the western part of the Nigerian continental margin. The formation of the Dahomey basin is associated with rifting and break-up of the African and South American plates. Lithospheric cooling and contraction probably produced post break-up subsidence of the basin. This concept of a thermally controlled isostatic subsidence is supported by reconstructed subsidence curves. After the component of subsidence due to sediment loading has been removed, it is found that the tectonic subsidence y_t varies directly as √t, where t is the time since subsidence began.The time/temperature/depth relations for sediments in this part of the Nigerian continental margin have been reconstructed from the subsidence and palaeotemperature data. The results clearly indicate that most post-Turonian sediments have hardly been subjected to temperatures higher than 75°C at any time. Insight into the level of maturation of the organic matter contained in the sediments has been provided by the extent of ‘cooking’ to which these sediments have been subjected. The hydrocarbon prospects of this part of the Nigerian continental margin are poor.     

Phanerozoic paleogeography,paleoenvironment and lithofacies maps of the circum-Atlantic margins

A series of maps was constructed, depicting the plate tectonic configuration, paleogeography, paleoenvironment and lithofacies for Phanerozoic time intervals from Cambrian through the Neogene. These are world maps comprising 300 continental plates and terranes, but are reprojected here to illustrate the circum-Atlantic margins. The relative position of the continents through time was largely derived from PLATES and PALEOMAP software.These maps illustrate the Phanerozoic geodynamic evolution of the Earth. They show the relationship of the continental configuration, lithofacies, tectonics, and climate, from the time of the disassembly of Rodinia to the assembly and break-up of Pangea. From a regional perspective, the facies in basins along the circum-Atlantic margin reflect various stages of rifting and passive margin development. Inversion caused by ridge push played an important role in the basin evolution and has influenced the distribution of lithofacies at various times. The power of the maps is realized in their application as an aid to the visualization of the relationship of regional basin development, sedimentation and erosion to the deposition of potential source-rock, reservoir and seals.The individual maps illustrate the conditions present during the maximum marine transgressions of sea-level within the Sauk, Tippecanoe, Kaskaskia, Absaroka, Zuni, and Tejas megasequences of Sloss. Relative sea level cyclicity, chronostratigraphy, and regional unconformities provide the basis for partitioning these higher frequency depositional cycles into 32 subdivisions (supersequences) ranging in duration from 11 to 39 my. In this report 14 of these time slices are used to illustrate the environments and lithologies resulting from changes in the geographic position of the terranes which constitute the present Atlantic margins. The text attempts to fill in details of the progressive change between mapped intervals. Data for the maps were derived from geologic reports, maps and stratigraphic columns and other paleogeographic interpretations regarding tectonics, basin formation, and deposition. The lithofacies are depicted by 21 patterns.     

Cenozoic giant coal-bearing basin belt discovered in China’s sea area

Sea area is an important area of oil and gas exploration in China. It has been found that China’s sea area mainly consists of coal type oil and gas, and the exploration of coal-bearing series source rocks has become an important part of oil and gas exploration there. Through years of comprehensive geological research in China’s sea area, it has been revealed that it has undergone multiple occurrences of tectonic opening and closing movements in varying degrees in the Paleogene, forming 26 Cenozoic sedimentary basins of various types, such as active continental margin, passive continental margin, transitional continental margin and drift rift basins. In the present study, it is observed for the first time that coal type source rocks are mainly developed in 14 continental margin basins in China’s sea area, revealing that a very large C-shaped coal-bearing basin group developed there in the Cenozoic. Next, based on the coupling analysis of paleoclimate, paleobotany, paleogeography and paleostructure, it is observed that there are five coal-forming periods in China’s sea area, namely the Paleocene, Eocene, early Oligocene, late Oligocene and Miocene-Pliocene, and the coal-forming age is gradually new from north to south. It is also found that the coal seams in the sea area are mainly developed in three coal-forming environments in Cenozoic, namely delta, fan delta and tidal flat-lagoon. The coal seams developed in different environments are characterized by thin thickness, many layers and poor stability. However, the coal-bearing series source rocks in China’s sea area have a wide distribution range, very high thickness and large amount, thus forming a material basis for the formation of rich coal type oil and gas.     

Structure and evolution of a passive margin in a compressive environment: Example of the south-western Alps-Ligurian basin junction during the Cenozoic

We focus on the northern Ligurian margin, at the geological junction of the subalpine domain and the Ligurian oceanic basin, in order (1) to identify the location of the southern limit of the Alpine compressive domain during the Cenozoic, and (2) to study the influence of a compressive environment on the tectonic and sedimentary evolution of a passive margin.Based on published onshore and offshore data, we first propose a chronology of the main extensional and compressional regional tectonic events.High-resolution seismic data image the margin structure down to ∼3 km below seafloor. These data support that past rifting processes control the present-day margin structure, and that 2800-4000 m of synrift sediment was deposited on this segment of the margin in two steps. First, sub-parallel reflectors indicate sediment deposition within a subsident basin showing a low amount of extension. Then, a fan-shaped sequence indicates block tilting and a higher amount of extension. We do not show any influence of the Miocene Alpine compression on the present-day margin structure at our scale of investigation, despite the southern subalpine relief formed in the close hinterland at that time. The southern front of the Miocene Alps was thus located upslope from the continental margin.Finally, a comparison with the Gulf of Lions margin suggests that the tectonic influence of the Alpine compression on the rifting processes is restrited to an increase of the subsidence related to flexure ahead of the Alpine front, explaining abnormally high synrift thicknesses in the study area. The Alpine environment, however, has probably controlled the sedimentary evolution of the margin since the rifting. Indeed, sediment supply and distribution would be mainly controlled by the permanent building of relief in the hinterland and by the steep basin morphology, rather than by sea-level fluctuations, even during the Messinian sea-level low-stand.     

Global and continental-scale glaciations on the Precambrian earth

Earth’s climate during the Proterozoic Eon was marked by major glacial events with evidence for large continental ice sheets on many cratons, and with sedimentological data indicating that glaciers had extended to sea-level. This paper emphasizes the sedimentological and sequence stratigraphic responses to glaciations and evaluates the major driving forces of glaciations during the Precambrian. First- and second-order sequences are recognized related to continental-scale fragmentation and formation of marine rift basins wherein sedimentary rocks indicate glacial influences and pronounced tectonic-climatic linkages. Coarse syn-rift deposits are typically characterized by mass flow diamictites and conglomerates. It is important to undertake sedimentological facies and sequence stratigraphic analysis of these syn-rift and capping passive margin sequences, as well as of slope turbidite deposits which formed if enhanced subsidence of the basins was occurring. More generally, latitude and syn-rift tectonic uplift can cause formation of glacial ice and enhance distinctive glacial influences on extensional basin sedimentation, thus supporting a causal relationship between thermal subsidence and the formation of glacier ice on inland areas. During the Precambrian, however, it is suggested that long-lived marine-terminated glaciers also situated at low paleolatitudes, were related to an extensional tectonic setting. In such settings, glacial deposits associated with sedimentary sequences of distinctively different origin, e.g. carbonate and chemically mature siliciclastic sequences, can well be used to detect the prominent sequence boundaries to verify depositional systems tracts. Internal sediment stacking patterns in sequences are indicative of dynamic processes along glaciated continental margins and without always having the need for global synchroneity. In glacially influenced rift basins and continental margins it is important to recognize the sequence boundaries of significant subaerial unconformities and their correlative conformities. A sequence boundary is a chronostratigraphically significant surface always produced as a consequence of a change in relative sea-level. These can then be well related to initiation and decay of glaciations, however on-land glacial deposits in a very few cases are prevented from later erosion. Attenuation of continental crust during rifting and breakup of the continent raises relative sea-level and also many of the shallow intra-cratonic basins subsided below sea-level, in favourable conditions being affected by major continental glaciations.Paleoproterozoic and Neoproterozoic glacial deposits are known in North and South America, South Africa, India, Western Australia and Fennoscandia. Against this background, continental-scale to global glaciations in the Precambrian appear to be possible, however views on the causes and timing of these glaciations, as well as on planetary extent of ice cover are still contradictory. There is a need to continue detailed sedimentological studies of pre-glacial and post-glacial deposits as well as to interpret syn-glacial lithofacies for their inferred transportation and depositional processes. Pre-glacial deposits, especially, should provide a new target to help us understand the processes that initiated these Precambrian glaciations. The sequence stratigraphic approach with understanding of the stacking pattern of depositional systems could prevent oversimplification and use of just single events to explain the complexity of evolution of glacially influenced Precambrian continental margin sediments.     

南沙海域礼乐盆地中生界油气资源潜力

位于南沙东部海域的礼乐盆地是一大型的中、新生代叠置盆地,其特有的地质背景及巨厚的中生代地层显示了其与南沙海域其他新生代沉积盆地的差异。盆地内发育的厚度超过4 000 m的中生代海相地层,主要包括了上侏罗统—下白垩统的滨—浅海相含煤碎屑岩或半深海相页岩、上三叠统—下侏罗统三角洲—浅海相砂泥岩和中三叠统深海硅质页岩等3套地层,展示出盆地具有良好的油气生成潜力。而早期位于华南陆缘、现今位于南沙东部海域的礼乐盆地中生界,完全具备了形成油气藏的基本石油地质条件,具有较为良好的油气资源潜力,其中生界油气资源勘探具有非常重要的意义,将成为我国海域油气勘探的一个重要新领域。     

大洋钻探与冲绳海槽地质

本文简要回顾大洋钻探计划实施十余年来所取得的成果，评述了西太平洋边缘海盆的研究概况，提出东海大陆边缘的重大地质问题是陆缘的构造演化历史和动力学过程，弧后扩张中心的热液成矿作用以及海洋沉积层序记录的古气候和古海洋环境变化，指出矿物－地球化学在大洋钻探研究中的重要性。     

Thermal evolution of the lithosphere of buried structures of the deep-water basin of the Black Sea

The GALO system for basin modeling is applied for numerical reconstruction of the thermal history of the lithosphere of the Western Basin and the Shatsky and Andrusov rises in the Black Sea. The modeling showed that the variant of the thermal evolution of the lithosphere of the region that was used by us for the Eastern Basin in our previous study is also applicable to the thermal evolution of the lithosphere of various tectonically different structures of the deep-water part of the Black Sea. These structures include both the Western and Eastern basins of the sea characterized by a granite-free crust formed in the course of the back-arc spreading and the Shatsky and Andrusov rises with the continental type of crust. The proposed version of the lithosphere evolution in the deep-water part of the Black Sea implies the initial stage of quasi-rift heating in the Upper Cretaceous and the three-staged thermal activation of the plate in the Cenozoic accompanied by three successive stages of crustal thinning. The latter resulted in the gradual deepening of the sea down to the present-day depth of 2.2 km.     

Late Pliocene Mega Debris Flow Deposit and Related Fluid Escapes Identified on the Antarctic Peninsula Continental Margin by Seismic Reflection Data Analysis

We have obtained improved images of a debris flow deposit through the reprocessing of multichannel seismic reflection data between Drifts 6 and 7 of the continental rise of the Pacific margin of the Antarctic Peninsula. The reprocessing, primarily aimed at the reduction of noise, relative to amplitude preservation, deconvolution, also included accurate velocity analyses. The deposit is dated as upper Pliocene (nearly 3.0 Ma) via correlation to Sites 1095 and 1096 of the Ocean Drilling Program (ODP) Leg 178. The estimated volume is about 1800 km³ and the inferred provenance from the continental slope implies a run out distance exceeding 250 km. The dramatic mass-wasting event that produced this deposit, unique in the sedimentary history of this margin, is related to widespread late Pliocene margin erosion. This was associated with a catastrophic continental margin collapse, following the Antarctic ice sheet expansion in response to global cooling. The seismic data analysis also allowed us to identify diffractions and amplitude anomalies interpreted as expressions of sedimentary mounds at the seafloor overlying narrow high-velocity zones that we interpret as conduits of fluid expulsion hosting either methane hydrates or authigenic carbonates. Fluid expulsion was triggered by loading of underlying sediments by the debris flow deposits and may have continued until today by input of fluids from sediment compaction following the deep diagenesis of biogenic silica.     

Salt tectonics at passive margins: Geology versus models

Salt tectonics at passive margins is currently interpreted as a gravity-driven process but according to two different types of models: i) pure spreading only driven by differential sedimentary loading and ii) dominant gliding primarily due to margin tilt (slope instability). A comparative analysis of pure spreading and pure spreading is made using simple mechanics as well as available laboratory experiments and numerical models that consider salt tectonic processes at the whole basin scale. To be effective, pure spreading driven by sedimentary loading requires large differential overburden thicknesses and therefore significant water depths, high sediment density, low frictional angles of the sediments (high fluid pore pressure) and a seaward free boundary of the salt basin (salt not covered by sediments). Dominant gliding does not require any specific condition to be effective apart from the dip on the upper surface of the salt. It can occur for margin tilt angles lower than 1° for basin widths in the range of 200-600 km and initial sedimentary cover thickness up to 1 km, even in the absence of abnormal fluid pressure. In pure spreading, salt resists and sediments drive whereas in dominant gliding both salt and sediments drive. In pure spreading, extension is located inside the prograding sedimentary wedge and contraction at the tip. Both extension and contraction migrate seaward with the sedimentary progradation. Migration of the deformation can create an extensional inversion of previously contractional structures. In pure spreading, extension is located updip and contraction downdip. Extension migrates downdip and contraction updip. Migration of the deformation leads to a contractional inversion of previously extensional structures (e.g. squeezed diapirs). Mechanical analysis and modelling, either analogue or numerical, and comparison with margin-scale examples, such as the south Atlantic margins or northern Gulf of Mexico, indicate that salt tectonics at passive margins is dominated by dominant gliding down the margin dip. On the contrary, salt tectonics driven only by differential sedimentary loading is a process difficult to reconcile with geological evidence.