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1.
前人对皖南-浙西地区古生代至早中生代盖层中发育的褶皱变形期次、特征和构造样式的认识尚存在较多分歧。本文通过区内盖层褶皱变形调查与解析,除印支早期褶皱和燕山期构造外,新识别出加里东期和印支晚期褶皱。加里东期褶皱样式主要表现为大型中常至开阔褶皱,且均为复式褶皱;次为小型紧闭褶皱,二者可能为从属性质。其构造线均呈近东西向或北东东向。印支早期褶皱样式主要为中常线形褶皱,其轴迹呈北东向;晚期表现为中常至开阔褶皱样式,轴迹呈北北西或近南北向。燕山期构造主要为盆地和断裂构造。早白垩世早期,表现为同沉积宽缓向斜,构造线呈近东西向;早白垩世之后,主要表现为断陷盆地和断裂构造,构造线呈北东或北北东向。各期褶皱叠加明显,形成"L"或"厂"字型组合特征,或形成构造穹窿-盆地组合。深入研究构造特征及演化规律,对区域构造格架建立具有重要意义。  相似文献   

2.
合肥盆地中生代地层时代与源区的碎屑锆石证据   总被引：3，自引：0，他引：3  
王薇  朱光  张帅  刘程  顾承串 《地质论评》2017,63(4):955-977
合肥盆地位于大别造山带北侧、郯庐断裂带西侧,其发育过程与这两大构造带演化密切相关。本次工作对合肥盆地南部与东部出露的中生代砂岩与火山岩进行了锆石年代学研究,从而限定了各组地层的沉积时代,确定了火山岩喷发时间,指示了沉积物的源区。这些年代学数据表明,合肥盆地南部的中生代碎屑岩自下而上分别为下侏罗统防虎山组、中侏罗统圆筒山组或三尖铺组、下白垩统凤凰台组与周公山组(或黑石渡组)与上白垩统戚家桥组,其间缺失上侏罗统。盆地东部白垩系自下而上为下白垩统朱巷组与响导铺组和上白垩统张桥组。该盆地出露的毛坦厂组或白大畈组火山岩喷发时代皆为早白垩世(130～120 Ma)。盆地南部的下——中侏罗统及白垩系源区皆为大别造山带,分别对应该造山带的后造山隆升与造山后伸展隆升。而盆地东部白垩系的源区始终为东侧的张八岭隆起带,后者属于郯庐断裂带伸展活动中的上升盘。  相似文献   

3.
The Bilelyeri Group comprises complexly deformed Mesozoic sedimentary rocks of continental-margin affinities (Kumluca Zone). These are structurally intercalated between a coeval carbonate platform to the west (Bey Daǧlari Zone) and late Triassic ophiolitic rocks and sediments, interpreted as emplaced marginal oceanic crust, to the east (Gödene Zone). Four formations erected in the Bilelyeri Group record the later stages of continental rifting and the progressive development of part of a Mesozoic passive continental margin. The two late Triassic formations, the Telekta? Tepe and the Hatipalani Formations, are dominated by terrigenous clastic and calcareous clastic sediments, including large detached blocks of reef limestone. These rocks were laid down by mostly mass-flow and turbidity-flow into steep-sided rift depressions. Organic reefs were constructed in bordering shallow seas while terrigenous clastic sediment was shed from exposed basement horsts. Thick sequences of mafic lavas were extruded (Norian) in axial parts of the rift zones, followed by a regional change to deposition of pelagic Halobia-bearing limestone. This culminated in a major hiatus involving large-scale sliding of shallow-water limestones into deeper water. The Jurassic to early Cretaceous Dereköy Formation mostly consists of siltstones, radiolarian cherts and mudstones, intercalated with redeposited limestones and black shales. During this time parts of the margin were bordered by major offshore carbonate complexes constructed partly on basement fragments previously rifted off the parent continental areas. Black shales and reduced hemipelagic sediments were deposited in an elongate trough between the main platform and an offshore complex to the east. Some degree of margin reactivation in the early Cretaceous is indicated by renewed deposition of turbiditic sandstone and chloritic clays in some distal sequences. Strong relative enrichment of manganese in some horizons is attributed to offshore volcanic exhalations. Subsequent regional subsidence in the mid-to late Cretaceous is suggested by a switch to predominantly calcareous, pelagic sedimentation on the adjacent platform and the offshore massifs as well as on the Bilelyeri margin. Tectonic disruption of the platform edge during the late Cretaceous is implied by major redeposition of shallow-water shelf limestones in proximal Bilelyeri sequences. The Bilelyeri margin and the adjacent Gödene Zone were tectonically deformed in latest Cretaceous to early Tertiary time and were thrust over the adjacent Bey Daǧlari platform in the early Miocene. Viewed in an East Mediterranean perspective, the Bilelyeri sequences were part of a locally north-south trending segment of a regionally east-west margin to a substantial oceanic area further south. This segment apparently suffered significant strike-slip deformation both during its construction and its later emplacement. Instructive comparisons can be made with other areas of the East Mediterranean, especially south-west Cyprus.  相似文献   

4.
沂沭断裂带纵贯山东省中部,属郯庐断裂带中段。在沂沭断裂带及其近区新元古代—新生代的沉积地层中,到目前,已识别出25个地震事件层位。这些地震事件层位的名称取自不同年代或年龄的含地震记录的岩石地层。大多数地震记录是震积岩,少部分为震火山岩,它们的时空分布支持该断裂带生成—活动与发展历史分2个阶段: 古郯庐断裂带阶段(新元古代—古生代)和中—新生代阶段。新元古代初鲁中至苏皖北部NNE向韧性剪切带的形成,沟通了秦岭大别与苏鲁洋间的NEE走向的转换断层,可能是沂沭断裂带或古郯庐断裂带的成因机制。在纵向上,古郯庐断裂带阶段形成了8个地震事件层位,其中5个地震事件层位较密集地分布于南华系至中下寒武统;中—新生代阶段形成了17个地震事件层位,其中12个层位较密集的分布于白垩系—古近系。因此,南华纪—早中寒武世、白垩纪—古近纪分别为2个发展阶段的强地震事件频繁发生时段。在这2个发展阶段,该断裂带地震活动的动力来源不同: 古郯庐断裂带阶段主要源于华北与华南板块的相向运动与碰撞;中—新生代阶段主要源于太平洋板块向欧亚大陆板块下俯冲。在横向上,有15个(占60%)地震事件层位分布在此断裂带内或由该断裂带内向两侧延伸,这体现了沂沭断裂带一直是研究区内发震构造的主体。所有地震事件地层分布于该断裂带纵中轴线两侧150~180,km以内的同沉积盆地,这证明该深大断裂带的两侧近区是强构造地震活动区。作者关于地震事件层位的时空分布的论述和图解,展示了该断裂带自形成以来的地震作用的过程与历史,清晰地勾绘出了这条长期活动地震带的影响范围,这不仅对分析此类深大活动断裂带及其附近由地震引发的软沉积物变形与地震作用具有重要意义,而且对评价此类地震带对地表和建筑物的地震破坏效应也具有重要意义。  相似文献   

5.
The low‐temperature thermal history of the Holy Cross Mountains (HCM) is investigated by apatite fission track and apatite and zircon (U–Th)/He thermochronology. Our results provide constraints on the deformation history of Palaeozoic basement rocks in the transition area from Precambrian to Palaeozoic Europe that are exposed from beneath Permian–Mesozoic sediments within the HCM. Late to post‐Variscan cooling of the Palaeozoic strata from maximum temperatures is shown to be a major feature of the HCM. This cooling likely followed a heating event related to burial and/or hot fluid circulation along the Holy Cross Fault in the late Carboniferous. The central part of the HCM shows a rapid cooling event caused by tectonic inversion, which started in the Late Cretaceous. However, this event was less pronounced in the western margin of the HCM, where slow cooling continued throughout the Mesozoic with only minor acceleration of the cooling rate since the latest Cretaceous.  相似文献   

6.
应用钻井、测井及古生物资料,对下扬子苏北盐阜地区中、古生界地层进行研究,同时综合了重、磁、电、二维地震、MT二维剖面等资料,探讨盐阜地区中生界残留地层展布规律。研究结果表明,中生界白垩系浦口组在研究区广泛分布,厚度较大,且分布稳定,而赤山组、葛村组及侏罗系、三叠系局部零星分布;上古生界地层残存在滨海隆起—建湖隆起引水沟凸起一带,下古生界地层残存在淮阴凹陷—盐城凹陷地区。  相似文献   

7.
The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas. Sedimentary successions of Neoproterozoic and Palaeozoic age dominate the bedrock geology. Together with Northern Tajmyr, Severnaya Zemlya constitutes the main land areas of the North Kara Terrane (NKT), which is inferred here to have been a part of the Timanide margin of Baltica, i.e. an integral part of Baltica at least since the Vendian. Vendian turbidites derived from the Timanide Orogen are inferred to have been deposited on Neoproterozoic greenschist facies, granite-intruded basement. Shallow-water siliclastic deposition in the Early to Mid-Cambrian was followed by highly organic-rich shales in the Late Cambrian and influx of more turbidites. An episode of folding, the Kan’on River deformation, separates these formations from the overlying Tremadocian conglomerates and sandstones. In the Early Ordovician, rift-related magmatic rocks accompanied the deposition of variegated marls, sandstones, carbonates and evaporites. Dark shales and gypsiferous limestones characterise the Mid-Ordovician. Late Ordovician quartz-sandstones mark a hiatus, followed by carbonate rocks that extend up into and through most of the Silurian. The latter give way upwards into Old Red Sandstones, which are inferred to have been deposited in a Caledonian foreland basin. Deformation, reaching the area in the latest Devonian or earliest Carboniferous and referred to as the Severnaya Zemlya episode, is thought to be Caledonian-related. The dominating E-vergent structure was controlled by décollement zones in Ordovician evaporite-bearing strata; detachment folds and thrusts developed in the west and were apparently impeded by a barrier of Ordovician igneous rocks in the east. Below the décollement zones, the Neoproterozoic to Early Ordovician succession was deformed into open to close folds. The exposed strata in the lower structural level have been juxtaposed with those in the upper structural level along the major N-trending Fiordovoe Lake Fault Zone, which involved several kilometres of dextral strike-slip movement and downthrow to the west. A major Early Carboniferous unconformity separates the folded Mid-Palaeozoic and older rocks from overlying Carboniferous formations, as on Franz Joseph Land and Svalbard. Subsequent latest Palaeozoic to Early Mesozoic orogeny, as on Taimyr, apparently had little influence on the Severnaya Zemlya successions.  相似文献   

8.
This paper attempts to investigate the tectonics of the southern Rif Cordillera. Hydrogeological and oil well data, together with interpretation of seismic reflection lines help to characterize the architecture of the Rharb–Mamora Basin located in the frontal region of the Gibraltar Arc. The facies map constructed from the drilling data exhibits four main types of Pliocene facies: (i) conglomerates; (ii) limestones; (iii) sandstones and sands more or less rich with shelly remains; (iv) clays. The lateral variation of deposits is accompanied by thickening, which can reach a few tens of metres. Thickening of layers and lithofacies variation indicate synsedimentary faulting processes. Two major fault zones have been identified: Kenitra–Sidi Slimane Fault Zone (K2SFZ) and Rabat–Kenitra Fault Zone (RKFZ). In the western coastal area, the geometrical configuration suggests a partition into horsts and grabens in the southern part, and a system of three geological units in the northern part. The analysis and interpretation of the gravity data reveal an important gravity anomaly, referred to as the Kenitra Gravity Anomaly. It corresponds to the Hercynian faults deduced by the seismic reflection line interpretation: K2SFZ and RKFZ. From Larache to El Jadida cities, the Kenitra area represents the hinge between the positive and negative gravity values, with a major negative anomaly in the eastern part of Kenitra. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

9.
Nyankanga is the largest gold deposit in the Geita Greenstone Belt of the northern Tanzania Craton. The deposit is hosted within an Archean volcano-sedimentary package dominated by ironstones and intruded by a large diorite complex, the Nyankanga Intrusive Complex. The supracrustal package is now included within the intrusive complex as roof pendants. The ironstone fragments contain evidence of multiple folding events that occurred prior to intrusion. The supracrustal package and Nyankanga Intrusive Complex are cut by a series of NE–SW trending, moderately NW dipping fault zones with a dominant reverse component of movement but showing multiple reactivation events with both oblique and normal movement components. The deposit is cut by a series of NW trending strike slip faults and ~ E–W trending late normal faults. The Nyankanga Fault Zone is a major NW dipping deformation zone developed mainly along the ironstone–diorite contacts that is mineralised over its entire length. The gold mineralization is hosted within the damage zone associated with Nyankanga Fault Zone by both diorite and ironstone with higher grades typically occurring in ironstone. Ore shoots dip more steeply than the Nyankanga Fault Zone. The mineralization is associated with sulfidation fronts and replacement textures in ironstones and is mostly contained as disseminated sulphides in diorite. The close spatial relationship between gold mineralization and the ironstone/diorite contact suggests that the reaction between the mineralising fluid and iron rich lithotypes played an important role in precipitating gold. Intense brecciation and veining, mainly in the footwall of Nyankanga Fault Zone, indicates that the fault zone increased permeability and allowed the access of mineralising fluids. The steeper dip of the ore shoots is consistent with mineralization during normal reactivation of the Nyankanga Fault Zone.  相似文献   

10.
The SW Baltic Sea occupies an area where crustal-scale regional tectonic zones of different age merge and overlap, creating a complex tectonic pattern. This pattern influenced the evolution of the Mesozoic sedimentary basin in this area. We present an interpretation of new high-resolution seismic data from the SW Baltic Sea which provided new information both on modes of the Late Cretaceous inversion of this part of the Danish–Polish Mesozoic basin system as well as on relationship between tectonic processes and syn-tectonic depositional systems. Within the Bornholm–Dar owo Fault Zone, located between the Koszalin Fault and Christiansø Block, both strike-slip and reverse faulting took place during the inversion-related activity. The faulting was related to reactivation of extensional pre-Permian fault system. Syn-tectonic sedimentary features include a prominent, generally S- and SE-directed, progradational depositional system with the major source area provided by uplifted basement blocks, in particular by the Bornholm Block. Sediment progradation was enhanced by downfaulting along a strike-slip fault zone and related expansion of accommodation space. Closer to the Christiansø Block, some syn-tectonic deposition also took place and resulted in subtle thickness changes within the hinge zones of inversion-related growth folds. Lack of significant sediment supply from the inverted and uplifted offshore part of the Mid-Polish Trough suggests that in this area NW–SE-located marginal trough parallel to the inversion axis of the Mid-Polish Trough did not form, and that uplifted Bornholm Block played by far more prominent role for development of syn-inversion depositional successions.  相似文献   

11.
The Congo Basin in central Africa is one of the largest intracratonic sedimentary basins in the world. The geological knowledge of Congo Basin is mainly based on studies from the central part of the basin (“Cuvette Centrale”). We present the results of sedimentary provenance investigations of the Jurassic–Cretaceous strata from the southwestern part of the basin, called the Kasai region. This study combines sandstone petrography with U-Pb and Lu-Hf analyses of detrital zircons to assess the stratigraphy, sedimentary provenance and drainage history of the Upper Jurassic-Cretaceous strata in the Kasai region. The stratigraphy is subdivided into a single Upper Jurassic unit (J1) and four Cretaceous units (C1–C4). Petrographically, sandstones from all units except the conglomeratic C3 are texturally and compositionally mature, dominated by quartzarenite and subarkosic compositions. These characteristics can be attributed to considerable recycling of older sedimentary strata and crustal sources, along with long distance fluvial and aeolian processes. The analyses of fifteen detrital zircon samples from the Upper Jurassic–Cretaceous strata yielded mainly Archean and Proterozoic zircons. This result suggests that sandstones are likely sourced from the underlying Archean-Paleoproterozoic Congo–Kasai Craton and from nearby Proterozoic mobile belts, particularly the Irumide and Lufilian Belts to the south of the basin. The dominance of Archean and Proterozoic detrital zircons in Upper Jurassic–Cretaceous strata suggests that the Kasai portion of the Congo Basin experienced exhumation and erosion, which is possibly associated with far-field reactivation of Archean and Proterozoic structures during and following Gondwana rifting in the late Mesozoic. A large fluvial drainage network sourced from the south of the basin, is interpreted to have developed across central Africa during the Late Jurassic–Cretaceous. This fluvial system is believed to have flowed northward across the Congo Basin and ultimately drained into a wrench fault system called the Central African Shear Zone, which extends in an ENE direction from the Gulf of Guinea through Cameroon into Sudan and Kenya.  相似文献   

12.
The WNW–ESE trending Toulourenc Fault Zone (TFZ) is the western segment of the major Ventoux–Lure Fault Zone, which separates the Provençal platform from the Baronnies Vocontian Basin. The TFZ was subject to polyphased Mid-Cretaceous movements, during the Early Aptian and Middle–Late Albian times. The latter faulting episode generated conglomerates and olistoliths resulting from dismantled faultscarps cutting Barremian–Bedoulian limestones. The deformation is related to compressional wrench faulting (NE–SW sinistral faults; dextral component for the TFZ). It induced the uplift of the northwestern corner of the platform, as indicated by a mid-Cretaceous hiatus (Early Aptian pro parte to Early Albian) narrowly delimited in space. The opening of submeridian grabens within the platform favoured the northward transit of channelised coarse-grained Albian sands originating from a southern area. To cite this article: C. Montenat et al., C. R. Geoscience 336 (2004).  相似文献   

13.
The Blue Nile Basin, situated in the Northwestern Ethiopian Plateau, contains ∼1400 m thick Mesozoic sedimentary section underlain by Neoproterozoic basement rocks and overlain by Early–Late Oligocene and Quaternary volcanic rocks. This study outlines the stratigraphic and structural evolution of the Blue Nile Basin based on field and remote sensing studies along the Gorge of the Nile. The Blue Nile Basin has evolved in three main phases: (1) pre‐sedimentation phase, include pre‐rift peneplanation of the Neoproterozoic basement rocks, possibly during Palaeozoic time; (2) sedimentation phase from Triassic to Early Cretaceous, including: (a) Triassic–Early Jurassic fluvial sedimentation (Lower Sandstone, ∼300 m thick); (b) Early Jurassic marine transgression (glauconitic sandy mudstone, ∼30 m thick); (c) Early–Middle Jurassic deepening of the basin (Lower Limestone, ∼450 m thick); (d) desiccation of the basin and deposition of Early–Middle Jurassic gypsum; (e) Middle–Late Jurassic marine transgression (Upper Limestone, ∼400 m thick); (f) Late Jurassic–Early Cretaceous basin‐uplift and marine regression (alluvial/fluvial Upper Sandstone, ∼280 m thick); (3) the post‐sedimentation phase, including Early–Late Oligocene eruption of 500–2000 m thick Lower volcanic rocks, related to the Afar Mantle Plume and emplacement of ∼300 m thick Quaternary Upper volcanic rocks. The Mesozoic to Cenozoic units were deposited during extension attributed to Triassic–Cretaceous NE–SW‐directed extension related to the Mesozoic rifting of Gondwana. The Blue Nile Basin was formed as a NW‐trending rift, within which much of the Mesozoic clastic and marine sediments were deposited. This was followed by Late Miocene NW–SE‐directed extension related to the Main Ethiopian Rift that formed NE‐trending faults, affecting Lower volcanic rocks and the upper part of the Mesozoic section. The region was subsequently affected by Quaternary E–W and NNE–SSW‐directed extensions related to oblique opening of the Main Ethiopian Rift and development of E‐trending transverse faults, as well as NE–SW‐directed extension in southern Afar (related to northeastward separation of the Arabian Plate from the African Plate) and E–W‐directed extensions in western Afar (related to the stepping of the Red Sea axis into Afar). These Quaternary stress regimes resulted in the development of N‐, ESE‐ and NW‐trending extensional structures within the Blue Nile Basin. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

14.
The discovery of Permian, Mesozoic and Palaeocene palynomorphs from the Nindam forearc basin, exposed along the Indus Suture Zone in Ladakh, is reported. The palynomorphs are from volcanogenic sandstones and are poorly preserved, distorted and show the effects of abrasion (striation marks). The frequent occurrence of Proxapertites indicates the assemblage is at least Palaeocene in age. The Palaeocene palynomorphs and sediments were transported to the Nindam trough from nearby elevated landward regions (islands). These Palaeocene provenance areas were characterized by an estuarine, nearshore, tropical, warm‐humid environment and were situated at equatorial palaeolatitudes. However, the occurrence of Permian and Mesozoic palynomorphs in the assemblage indicates that the Late Palaeozoic and Mesozoic Tethyan sedimentary rocks exposed along the northern margin of the Indian plate were redeposited into the tectonically active Cretaceous–Palaeocene trench–subduction complex that existed between the Indian and the Asian plates until the collision took place at ～50–60 Ma.  相似文献   

15.
This paper describes the updated stratigraphy, structural framework and evolution, and hydrocarbon prospectivity of the Paleozoic, Mesozoic and Cenozoic basins of Yemen, depicted also on regional stratigraphic charts. The Paleozoic basins include (1) the Rub’ Al-Khali basin (southern flanks), bounded to the south by the Hadramawt arch (oriented approximately W–E) towards which the Paleozoic and Mesozoic sediments pinch out; (2) the San’a basin, encompassing Paleozoic through Upper Jurassic sediments; and (3) the southern offshore Suqatra (island) basin filled with Permo-Triassic sediments correlatable with that of the Karoo rift in Africa. The Mesozoic rift basins formed due to the breakup of Gondwana and separation of India/Madagascar from Africa–Arabia during the Late Jurassic/Early Cretaceous. The five Mesozoic sedimentary rift basins reflect in their orientation an inheritance from deep-seated, reactivated NW–SE trending Infracambrian Najd fault system. These basins formed sequentially from west to east–southeast, sub-parallel with rift orientations—NNW–SSE for the Siham-Ad-Dali’ basin in the west, NW–SE for the Sab’atayn and Balhaf basins and WNW–ESE for the Say’un-Masilah basin in the centre, and almost E–W for the Jiza’–Qamar basin located in the east of Yemen. The Sab’atayn and Say’un–Masilah basins are the only ones producing oil and gas so far. Petroleum reservoirs in both basins have been charged from Upper Jurassic Madbi shale. The main reservoirs in the Sab’atayn basin include sandstone units in the Sab’atayn Formation (Tithonian), the turbiditic sandstones of the Lam Member (Tithonian) and the Proterozoic fractured basement (upthrown fault block), while the main reservoirs in the Say’un–Masilah basin are sandstones of the Qishn Clastics Member (Hauterivian/Barremian) and the Ghayl Member (Berriasian/Valanginian), and Proterozoic fractured basement. The Cenozoic rift basins are related to the separation of Arabia from Africa by the opening of the Red Sea to the west and the Gulf of Aden to the south of Yemen during the Oligocene-Recent. These basins are filled with up to 3,000 m of sediments showing both lateral and vertical facies changes. The Cenozoic rift basins along the Gulf of Aden include the Mukalla–Sayhut, the Hawrah–Ahwar and the Aden–Abyan basins (all trending ENE–WSW), and have both offshore and onshore sectors as extensional faulting and regional subsidence affected the southern margin of Yemen episodically. Seafloor spreading in the Gulf of Aden dates back to the Early Miocene. Many of the offshore wells drilled in the Mukalla–Sayhut basin have encountered oil shows in the Cretaceous through Neogene layers. Sub-commercial discovery was identified in Sharmah-1 well in the fractured Middle Eocene limestone of the Habshiyah Formation. The Tihamah basin along the NNW–SSE trending Red Sea commenced in Late Oligocene, with oceanic crust formation in the earliest Pliocene. The Late Miocene stratigraphy of the Red Sea offshore Yemen is dominated by salt deformation. Oil and gas seeps are found in the Tihamah basin including the As-Salif peninsula and the onshore Tihamah plain; and oil and gas shows encountered in several onshore and offshore wells indicate the presence of proven source rocks in this basin.  相似文献   

16.
The multichannel seismic reflection data (MCS data) obtained in the Arktika-2014 expedition revealed the essential fact that must be taken into account by the tectonic model of the Central Arctic region. The Brookian, Lower Cretaceous, and Upper Jurassic unconformities are continuously traced from the North Chukchi offshore trough into the Podvodnikov Basin, indicating that the depocenter in the latter accumulated both Cretaceous sedimentary sequences and Early–Middle Mesozoic ones.  相似文献   

17.
From the Kruja Zone of Albania, shallow-water carbonates assigned to the lower Campanian are described and grouped into six microfacies types of shallow subtidal to intertidal depositional settings. The limestones display internal layering suggestive of microbial fabrics with abundance of nubeculariid foraminifera, incertae sedis Thaumatoporella Pia, and subordinate calcimicrobes of possible cyanobacterial origin: Gahkumella Zaninetti, Girvanella sp., and Decastronema kotori (Radoičić). The nubeculariid morphotypes with ornamented tests and microbial coatings reveal some kind of mutualistic relationship comparable to Late Palaeozoic–Mesozoic Tubiphytes Maslov and Crescentiella Senowbari-Daryan et al. The present study expands our knowledge on the micropalaeontological characteristics of the Late Cretaceous “Decastronema–Thaumatoporella association” widespread in carbonate platforms of the peri-Mediterranean region. Our findings indicate that nubeculariids may have played an important binding role in Late Cretaceous peritidal laminated limestones.  相似文献   

18.
Eastern Marmara region consists of three different morphotectonic units: Thrace–Kocaeli Peneplain (TKP) and Çamdağ–Akçakoca Highland (ÇAH) in the north, and Armutlu–Almacık Highland in the south of the North Anatolian Fault Zone (NAFZ). The geologic‐morphologic data and seismic profiles from the Sakarya River offshore indicate that the boundary between the TKP in the west and ÇAH in the east is a previously unrecognized major NNE–SSW‐trending strike‐slip fault zone with reverse component. The fault zone is a distinct morphotectonic corridor herein named the Adapazarı–Karasu corridor (AKC) that runs along the Sakarya River Valley and extends to its submarine canyon along the southern margin of the Black Sea in the north. It formed as a transfer fault zone between the TKP and ÇAH during the Late Miocene; the former has been experiencing extensional forces and the latter compressional forces since then. East–West‐trending segments of the NAFZ cuts the NE–SW‐trending AKC and their activity has resulted in the formation of a distinct fault‐bounded morphology, which is characterized by alternating E–W highlands and lowlands in the AKC. Furthermore, this activity has resulted in the downward motion of an ancient delta and submarine canyon of the Sakarya River in the northern block of the NAFZ below sea level so that the waters of the Black Sea invaded them. The NE–SW‐trending faults in the AKC were reactivated with the development of the NAFZ in the Late Pliocene, which then caused block motions and microseismic activities throughout the AKC. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

19.
湖南锡田锡钨多金属矿床成矿构造特征及其找矿意义   总被引：4，自引：0，他引：4  
锡田矿床内发育近SN向花岗岩穹窿伸展构造、NE向复式褶皱和NE或NEE向走滑伸展构造系统。穹窿构造主要由印支期和燕山期侵入的花岗岩和古生代地层及不连续的环形滑脱断层组成,控制燕山期花岗岩与围岩接触带矽卡岩型矿体的分布;复式褶皱为古生代地层组成的NE向复式向斜,在矿区中部被锡田复式花岗岩体切割。严塘复式向斜与小田复式向斜中的背斜核部,尤其断层叠加的部位常控制一些构造破碎带型钨锡富矿体的分布。NE向或NEE向走滑伸展构造系统包括NE向右行(伸展)走滑断层、NE向或近EW向右行次级的走滑伸展断层、近SN向左行走滑断层和NW向伸展断层,控制了锡田矿区内的不同方向构造蚀变岩型、石英脉型和云英岩脉型锡钨多金属矿床的分布。花岗岩锆石U-Pb、白云母40Ar-39Ar和辉钼矿Re-Os同位素测年表明锡田地区燕山期构造活动、岩浆作用与成矿响应时间非常接近,介于150～160Ma。岩体与地层(灰岩)接触带、岩体中的NEE向断裂带以及被NE向断裂叠加的背斜轴部是重要的成矿区域,可作为下一步矿产勘查工作重要靶区。  相似文献   

20.
《China Geology》2019,2(2):133-141
Source rocks are the material basis of oil and gas generation and determine the potential resources of exploration blocks and have important research value. This paper studies the lithology, thickness, and geochemistry of Mesozoic source rocks in the southeastern East China Sea continental shelf. The results show that the Mesozoic source rocks are mainly dark mudstone and coal-bearing strata. The total thickness of Lower–Middle Jurassic source rocks ranges from 100 m to 700 m, and that of Lower Cretaceous source rocks ranges from 50 m to 350 m. The overall thickness of Mesozoic source rocks is distributed in the NE direction and their thickness center is located in the Jilong Depression. The Lower–Middle Jurassic source rocks are mainly developed shallow marine dark mudstone and transitional coal measure strata. Those of the Lower Cretaceous are mainly mudstone of a fan delta front. Lower–Middle Jurassic and Lower Cretaceous hydrocarbon source rocks are dominated by type III kerogen, with Lower–Middle Jurassic hydrocarbon source rocks having high organic matter abundance and being medium–good hydrocarbon source rocks, while Lower Cretaceous hydrocarbon source rocks have relatively poor quality. From northwest to southeast, the vitrinite reflectance Ro of Mesozoic source rocks increases gradually. Source rocks in the study area are divided into three types. The first hydrocarbon-generating area is mainly located in the southeastern region of the study area, and the Jilong Depression is the hydrocarbon-generating center. The results of this study can provide a basis for exploration of Mesozoic oil and gas resources in the southeastern East China Sea continental shelf.© 2019 China Geology Editorial Office.  相似文献   

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