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1.
柴达木盆地西北缘始新世晚期古隆起与阿尔金断裂的形成 总被引：3，自引：0，他引：3
研究阿尔金断裂的演化是理解青藏高原隆升过程的重要环节.本文以柴达木盆地西北缘的地震剖面、残余厚度图、沉积相图等资料进行沉积、构造的综合研究,揭示了柴达木盆地西北缘在始新世晚期开始抬升,因此导致柴达木盆地西北缘生长地层的发育.这种抬升作用在平面上则表现为与阿尔金断裂呈～30°相交的NWW-SEE走向古隆起,以及与之相关的如冲积扇等边缘沉积相.本文分析认为阿尔金断裂在始新世晚期开始孕育,在深部形成左旋性质的韧性剪切带,在地表则通过形成左阶雁列式褶皱(即古隆起)来调节深部的位移量. 相似文献
2.
Provenance and tectonic history of the late Eocene‐early Oligocene submarine fans and shelf deposits on Lemnos Island, NE Greece, were studied using sandstone framework composition, sedimentological data and sandstone and mudstone geochemistry. The resulting tectonic–sedimentological model is based on the late Eocene–early Oligocene Lemnos Island being in a forearc basin with the outer arc ridge as a major sediment source. Modal petrographic analysis of the studied sandstones shows that the source area comprises sedimentary, metamorphic and plutonic igneous rocks deposited in the studied area in a recycled orogenic environment. Moreover, within the above sediments, the minor occurrence of volcanic fragments suggests little or no influence of a volcanic source. Provenance results, based on major, trace and rare earth element (REE) data, suggest an active continental margin/continental island arc signature. All the samples are LREE, enriched relative to HREE, with a flat HREE pattern and positive Eu anomalies, suggesting that the processes of intracrustal differentiation (involving plagioclase fractionation) were not of great importance. Results derived from the multi‐element diagrams also suggest an active margin character, and a mafic/ultramafic source rock composition, while the positive anomaly of Zr that can be attributed to a passive continental margin source, is most likely associated with reworking and sorting during sediment transfer. Palaeocurrents, with a NE–NNE direction, indicate a northeast flow, towards the location of the late Eocene–early Oligocene magmatic belt in the north‐east Aegean region. Conglomerates are composed of chert, gneiss and igneous fragments, such as basalts and gabbros, suggesting this outer arc ridge as a likely source area. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
盐源盆地始新世丽江组沉积时期发育了一套具大型高角度交错层理的红色砂岩,其确切成因对于厘定青藏高原东缘古近纪古地理格局、恢复东亚新生代干旱带与古气候演化过程具有重要意义。文中通过对盐源盆地始新统丽江组红色砂岩的沉积特征进行系统分析,证明该套砂岩的岩性、粒度分布、石英颗粒表面特征与沉积构造等明显不同于水成沉积,而与典型风成沙丘相应特征完全一致,表明其为风成沙丘沉积。结合古近纪研究区的古气候条件、大气环流样式与大地构造背景,笔者进一步推断盐源盆地始新世风成沙丘可能沉积于中国古近纪干旱带内的沙漠环境。根据目前相关研究资料,确认青藏高原东缘存在一个厚度稳定的古近纪风成沙丘富集带。 相似文献
4.
滇西新生代兰坪盆地和剑川盆地分别位于哀牢山–红河断裂带两侧,青藏高原东构造结内,其沉积过程和构造变形对青藏高原东南缘的构造演化有重要的启示意义。通过对这两个盆地古近纪沉积和构造过程的研究,我们发现兰坪盆地和剑川盆地及邻区的构造变形分为三期:始新世早期的强烈挤压变形、始新世中晚期的伸展变形、渐新世的走滑变形。始新世早期的挤压变形主要表现为兰坪地区的褶皱–冲断系统、哀牢山-红河断裂的逆冲活动和剑川盆地的宽缓褶皱。沉积方面,古新统勐野井组(E_1m)较为稳定的细粒滨湖相沉积转变为始新统宝相寺组(E_2b)较粗的具有前陆盆地性质的河流相沉积,特别是宝相寺组底部发育的一套快速堆积的磨拉石建造,可能是对始新世强烈挤压环境下的沉积响应。始新世中晚期伸展变形体现在盆地的构造环境由早期的挤压环境变为伸展环境和该时期大量富钾岩体和岩脉的侵入,沉积学上,下始新统宝相寺组的河流相转变为中始新统金丝厂组(E_2j)具有快速堆积磨拉石特征的曲流河沉积,极可能是对构造体制变革的沉积响应。渐新世的走滑变形则体现在渐新统的缺失和哀牢山–红河断裂的早期左行走滑。因此,我们认为剑川–兰坪地区在始新世中期和渐新世均发生了显著的运动学转换,这一认识也得到了始新世中期兰坪和剑川盆地物源明显变化的支持。结合青藏高原东南部始新世中晚期岩浆的活动,渐新世大型剪切带(崇山剪切带、高黎贡剪切带)的强烈走滑和保山块体的旋转,我们推测青藏高原东南缘古近纪的构造演化为古新世-始新世早期的挤压、始新世中晚期的伸展、渐新世的转换压缩。 相似文献
5.
Abstract— The composite nappe of the Spongtang ophiolite is thrust over Mesozoic and Cenozoic sediments of the North-Indian margin and shelf. The ophiolitic peridotiles tectonic-ally overlie a sedimentary melange, the detailed stratigraphy of which reveals the evolution of the South-Tethyan margin from its opening to its closure. The matrix of the melange is dated as Upper Campanian to Lower Eocene. Volcano-sedimentary olistoliths indicate carbonate platform sedimentation associated with alkaline lavas in the Permian, followed by more pelagic sedimentation of Upper Triassic and mid- Cretaceous age. They derived from external platforms near to the Indian shelf, but separated from it. Composite olistoliths of mid to late Cretaceous age, containing Permian elements, are found in the upper Cretaceous to lower Eocene wildflysch. Primary contacts of melange upon serpentinites indicates that the deeply eroded oceanic crust served partly as a substratum for the melange. 相似文献
6.
Luca Basilone 《Central European Journal of Geosciences》2009,1(3):251-273
Sequence stratigraphic studies of the Triassic through Paleogene carbonate successions of platform, slope and basin in western Sicily (Palermo and Termini Imerese Mountains) have identified a sedimentary cyclicity mostly caused by relative oscillations of sea level. The stratigraphic successions of the Imerese and Panormide palaeogeographic domains of the southern Tethyan continental margin were studied with physical-stratigraphy and facies analysis to reconstruct the sedimentary evolution of this platform-to-basin system. The Imerese Basin is characterized by a carbonate and siliceous-calcareous succession, 1200–1400m thick, Late Triassic to Eocene in age. The strata display a typical example of a carbonate platform margin, characterized by resedimented facies with progradational stacking patterns. The Panormide Carbonate Platform is characterized by a carbonate succession, 1000–1200 m thick, Late Triassic to Late Eocene, mostly consisting of shallow-water facies with periodic subaerial exposure. The cyclic arrangement has been obtained by the study of the stratigraphic signatures (unconformities, facies sequences, erosional surfaces and stratal geometries) found in the slope successions. The recognized pattern has been compared with coeval facies of the shelf. This correlation provided evidence of sedimentary evolution, influenced by progradation and backstepping of the shelf deposits. The stratigraphic architecture of the platform-to-basin system is characterized by four major transgressive/regressive cycles during the late Triassic to late Eocene. These cycles, framed in a chronostratigraphic chart, allows the correlation of the investigated shelf-to-basin system with the geological evolution of the African continental margin during the Mesozoic, showing tectono-eustatic cycles. The first cycle, encompassing the late Triassic to early Jurassic, appears to be related to the late syn-rift stage of the continental margin evolution. The following three cycles, spanning from the Jurassic to Eocene, can be related to the post-rift evolution and to thermal subsidence changes. 相似文献
7.
Stratigraphy of the upper cretaceous and lower tertiary strata in the Tethyan Himalayas of Tibet (Tingri area,China) 总被引：26，自引：0，他引：26
H. Willems Z. Zhou B. Zhang K. -U. Gräfe 《International Journal of Earth Sciences》1996,85(4):723-754
The 1500-m-thick marine strata of the Tethys Himalaya of the Zhepure Mountain (Tingri, Tibet) comprise the Upper Albian to Eocene and represent the sedimentary development of the passive northern continental margin of the Indian plate. Investigations of foraminifera have led to a detailed biozonation which is compared with the west Tethyan record. Five stratigraphic units can be distinguished: The Gamba group (Upper Albian - Lower Santonian) represents the development from a basin and slope to an outer-shelf environment. In the following Zhepure Shanbei formation (Lower Santonian - Middle Maastrichtian), outer-shelf deposits continue. Pebbles in the top layers point to beginning redeposition on a continental slope. Intensified redeposition continues within the Zhepure Shanpo formation (Middle Maastrichtian - Lower Paleocene). The series is capped by sandstones of the Jidula formation (Danian) deposited from a seaward prograding delta plain. The overall succession of these units represents a sea-level high at the Cenomanian/Turonian boundary followed, from the Turonian to Danian, by an overall shallowing-upward megasequence. This is followed by a final transgression — regression cycle during the Paleocene and Eocene, documented in the Zhepure Shan formation (?Upper Danian - Lutetian) and by Upper Eocene continental deposits. The section represents the narrowing and closure of the Tethys as a result of the convergence between northward-drifting India and Eurasia. The plate collision started in the Lower Maastrichtian and caused rapid changes in sedimentation patterns affected by tectonic subsidence and uplift. Stronger subsidence and deposition took place from the Middle Maastrichtian to the Lower Paleocene. The final closure of remnant Tethys in the Tingri area took place in the Lutetian. 相似文献
8.
东海西湖凹陷始新统沉积环境及含油气性 总被引：1，自引：0，他引：1
东海西湖凹陷始新统平湖组为半封闭海湾沉积环境,海水由南往北侵入,平湖组下段为海湾浅水—滨岸—滨岸冲积平原相沉积;平湖组中段为潮坪—三角洲相沉积;平湖组上段为三角洲相沉积。业已证明,始新统平湖组不但具有极好的生油气条件,而且发育良好的储集层。油气分布除了受构造因素控制外,与沉积相有极为密切的关系。 相似文献
9.
Abstract— Stratigraphic and petrographic analysis of the Cretaceous to Eocene Tibetan sedimentary succession has allowed us to reinterpret in detail the sequence of events which led to closure of Neotethys and continental collision in the NW Himalaya.During the Early Cretaceous, the Indian passive margin recorded basaltic magmaüc activity. Albian volcanic arenites, probably related to a major extensional tectonic event, are unconformably overlain by an Upper Cretaceous to Paleocene carbonate sequence, with a major quartzarenite episode triggered by the global eustatic sea-level fall at the Cretaceous/Tertiary boundary. At the same time, Neotethyan oceanic crust was being subducted beneath Asia, as testified by calc-alkalic volcanism and forearc basin sedimentation in the Transhimalayan belt.Onset of collision and obduction of the Asian accretionary wedge onto the Indian continental rise was recorded by shoaling of the outer shelf at the Paleocene/Eocene boundary, related to flexural uplift of the passive margin. A few My later, foreland basin volcanic arenites derived from the uplifted Asian subduction complex onlapped onto the Indian continental terrace. All along the Himalaya, marine facies were rapidly replaced by continental redbeds in collisional basins on both sides of the ophiolitic suture. Next, foreland basin sedimentation was interrupted by fold-thrust deformation and final ophiolite emplacement.The observed sequence of events compares favourably with theoretical models of rifted margin to overthrust belt transition and shows that initial phases of continental collision and obduction were completed within 10 to 15 My, with formation of a proto-Himalayan chain by the end of the middle Eocene. 相似文献
10.
Alastair Robertson Osman Parlak Timur Ustaömer Kemal Taslı Nurdan İnan Paulian Dumitrica 《Geodinamica Acta》2013,26(3-4):230-293
This paper presents several types of new information including U–Pb radiometric dating of ophiolitic rocks and an intrusive granite, micropalaeontological dating of siliceous and calcareous sedimentary rocks, together with sedimentological, petrographic and structural data. The new information is synthesised with existing results from the study area and adjacent regions (Central Pontides and Lesser Caucasus) to produce a new tectonic model for the Mesozoic–Cenozoic tectonic development of this key Tethyan suture zone.The Tethyan suture zone in NE Turkey (Ankara–Erzincan–Kars suture zone) exemplifies stages in the subduction, suturing and post-collisional deformation of a Mesozoic ocean basin that existed between the Eurasian (Pontide) and Gondwanan (Tauride) continents. Ophiolitic rocks, both as intact and as dismembered sequences, together with an intrusive granite (tonalite), formed during the Early Jurassic in a supra-subduction zone (SSZ) setting within the ?zmir–Ankara–Erzincan ocean. Basalts also occur as blocks and dismembered thrust sheets within Cretaceous accretionary melange. During the Early Jurassic, these basalts erupted in both a SSZ-type setting and in an intra-plate (seamount-type) setting. The volcanic-sedimentary melange accreted in an open-ocean setting in response to Cretaceous northward subduction beneath a backstop made up of Early Jurassic forearc ophiolitic crust. The Early Jurassic SSZ basalts in the melange were later detached from the overriding Early Jurassic ophiolitic crust.Sedimentary melange (debris-flow deposits) locally includes ophiolitic extrusive rocks of boninitic composition that were metamorphosed under high-pressure low-temperature conditions. Slices of mainly Cretaceous clastic sedimentary rocks within the suture zone are interpreted as a deformed forearc basin that bordered the Eurasian active margin. The basin received a copious supply of sediments derived from Late Cretaceous arc volcanism together with input of ophiolitic detritus from accreted oceanic crust.Accretionary melange was emplaced southwards onto the leading edge of the Tauride continent (Munzur Massif) during latest Cretaceous time. Accretionary melange was also emplaced northwards over the collapsed southern edge of the Eurasian continental margin (continental backstop) during the latest Cretaceous. Sedimentation persisted into the Early Eocene in more northerly areas of the Eurasian margin.Collision of the Tauride and Eurasian continents took place progressively during latest Late Palaeocene–Early Eocene. The Jurassic SSZ ophiolites and the Cretaceous accretionary melange finally docked with the Eurasian margin. Coarse clastic sediments were shed from the uplifted Eurasian margin and infilled a narrow peripheral basin. Gravity flows accumulated in thrust-top piggyback basins above accretionary melange and dismembered ophiolites and also in a post-collisional peripheral basin above Eurasian crust. Thickening of the accretionary wedge triggered large-scale out-of-sequence thrusting and re-thrusting of continental margin and ophiolitic units. Collision culminated in detachment and northward thrusting on a regional scale.Collisional deformation of the suture zone ended prior to the Mid-Eocene (~45?Ma) when the Eurasian margin was transgressed by non-marine and/or shallow-marine sediments. The foreland became volcanically active and subsided strongly during Mid-Eocene, possibly related to post-collisional slab rollback and/or delamination. The present structure and morphology of the suture zone was strongly influenced by several phases of mostly S-directed suture zone tightening (Late Eocene; pre-Pliocene), possible slab break-off and right-lateral strike-slip along the North Anatolian Transform Fault.In the wider regional context, a double subduction zone model is preferred, in which northward subduction was active during the Jurassic and Cretaceous, both within the Tethyan ocean and bordering the Eurasian continental margin. 相似文献
11.
Early Eocene Radiolarian Fauna from the Sangdanlin, Southern Tibet:
Constraints on the Timing of Initial India-Asia Collision 总被引：2，自引：1，他引：1
This is a new report on the early Eocene radiolarian fauna from the Sangdanlin section in the Gyirong region, along the southern margin of the Yarlung Zangbo Suture Zone. The Sangdanlin section measured in this study is divided into three lithostratigraphic units from bottom to top: the Zongzhuo, Sangdanlin, and Zheya formations. Abundant radiolarian fossils were obtained from the Sangdanlin section and 54 species of 30 genera were identified and assigned as follows: Cryptamphorella conara-C. macropora the late Cretaceous Zone and Amphisphaera coronate, Buryella tetradica-Bekoma campechensis, and B.bidartensis-B. divaricata the Paleocene-early Eocene Interval Zones. The Paleocene–early Eocene radiolarian zones are comparable to the radiolarian zones RP4-RP8 in New Zealand. Based on the data of radiolaria and lithofacies, it is suggested that the Zongzhuo Formation should be deposited along the base of the north-facing, continental slope of the Greater Indian continental margin, and the Sangdanlin Formation should be a deep marine, sedimentary sequence located in a foreland basin. The early Eocene radiolarian fauna in the Sangdanlin Formation constrains the initial age of the India-Asia collision to no later than 53.6 Ma. 相似文献
12.
The provenance of Eocene–Oligocene turbidites from the Pindos Foreland Basin, SW Greece, has been constrained using petrographical and geochemical techniques. Modal petrographic analysis of the studied sandstones shows that the source area comprises sedimentary, metamorphic, and plutonic igneous rocks deposited in a recycled orogenic environment and in magmatic arc province. The relative proportions of the detrital components indicate that the Late Eocene–Early Oligocene sandstones of West Peloponnesus are quartz-rich and were primarily derived from granitic and metamorphic basement rocks typically of a tectonically active area. Major, trace, and rare earth element (REE) concentrations in both sandstones and mudstones complement the petrographical data indicating an active continental margin/continental island arc signature. All the samples are light REE, enriched relative to heavy REE (HREE), with flat HREE pattern and positive Eu anomalies, suggesting that the processes of intra-crustal differentiation (involving plagioclase fractionation) were not of great importance. The results derived from the multi-element diagrams also suggest an active margin character and a mafic/ultramafic source rock composition. 相似文献
13.
柴达木盆地西南缘与之毗邻的阿达滩盆地对周边造山带构造应力场的变化响应敏感,并有较多的地质记录。中新生代以后,其与阿尔金断裂带同处于统一左行走滑剪切应力场作用之下,构造形迹保存较好。通过对盆地内沉积建造、断裂系性质及区域构造特征的识别分析,推断柴达木盆地西南缘在始新世时构造活动处于南北向挤压环境,而渐新世后则转换为左行平移构造应力之下。推测柴达木西南缘在三维空间上应当存在着来自塔里木地块斜向上的推挤力。通过盆地沉积及构造序列分析,初步建立了该区晚古近纪构造运动阶段性演化模式。 相似文献
14.
The published data on the sedimentation conditions, structure, and tectonic evolution of the Anadyr Basin in the Mesozoic
and Cenozoic are reviewed. These data are re-examined in the context of modern tectonic concepts concerning the evolution
of the northwestern Circum-Pacific Belt. The re-examination allows us not only to specify the regional geology and tectonic
history, but also to forecast of the petroleum resource potential of the sedimentary cover based on a new concept. The sedimentary
cover formation in the Anadyr Basin is inseparably linked with the regional tectonic evolution. The considered portion of
the Chukchi Peninsula developed in the Late Mesozoic at the junction of the ocean-type South Anyui Basin, the Asian continental
margin, and convergent zones of various ages extending along the Asia-Pacific interface. Strike-slip faulting and pulses of
extension dominated in the Cenozoic largely in connection with oroclinal bending of structural elements pertaining to northeastern
Eurasia and northwestern North America against the background of accretion of terranes along the zone of convergence with
the Pacific oceanic plates. Three main stages are recognized in the formation of the sedimentary cover in the Anadyr Basin.
(1) The lower portion of the cover was formed in the Late Cretaceous-Early Eocene under conditions of alternating settings
of passive and active continental margins. The Cenomanian-lower Eocene transitional sedimentary complex is located largely
in the southern Anadyr Basin (Main River and Lagoonal troughs). (2) In the middle Eocene and Oligocene, sedimentation proceeded
against the background of extension and rifting in the northern part of the paleobasin and compression in its southern part.
The compression was caused by northward migration of the foredeep in front of the accretionary Koryak Orogen. The maximum
thickness of the Eocene-Oligocene sedimentary complex is noted mainly in the southern part of the basin and in the Central
and East Anadyr troughs. (3) The middle Miocene resumption of sedimentation was largely related to strike-slip faulting and
rifting. In the Miocene to Quaternary, sedimentation was the most intense in the central and northern parts of the Anadyr
Basin, as well as in local strike-slip fault-line depressions of the Central Trough. Geological and geophysical data corroborate
thrusting in the southern Anadyr Basin. The amplitude of thrusting over the Main River Trough reaches a few tens of kilometers.
The vertical thickness of the tectonically screened Paleogene and Neogene rocks in the southern Main River Trough exceeds
10 km. The quantitative forecast of hydrocarbon emigration from Cretaceous and Paleogene source rocks testifies to the disbalance
between hydrocarbons emigrated and accumulated in traps of petroleum fields discovered in the Anadyr Basin. The southern portion
of the Anadyr Basin is the most promising for the discovery of new petroleum fields in the Upper Cretaceous, Eocene, and Upper
Oligocene-Miocene porous and fracture-porous reservoir rocks in subthrust structural and lithological traps. 相似文献
15.
西宁和贵德盆地新生代沉积物重矿物变化对构造活动的响应 总被引：1，自引：0，他引：1
位于青藏高原东北缘的西宁、贵德盆地的新生代沉积序列较完整的记录了盆地周围物源区构造变形过程。重矿物是碎屑物质的重要组成部分,是最直观、有效揭示源区母岩、构造-沉积过程的重要手段。通过重矿物的系统分析,结合沉积-构造变形,揭示出始新世-上新世末西宁-贵得盆地及其源区经历了几个构造活动阶段:古新世-始新世早期的隆升阶段、始新世中期-渐新世晚期的构造稳定阶段、渐新世末-中新世初的构造隆升阶段、中中新世构造稳定阶段和晚中新世以来的强烈隆升阶段。并结合特征矿物（绿泥石）及古水流分析,推断古近纪西宁-贵德盆地是东昆仑山前一个统一盆地。中新世早期青藏高原的扩张导致了拉脊山开始隆起,使原型盆地解体;约8.5 Ma以来拉脊山强烈隆升,两侧盆地逐渐转变为山间盆地。这为正确理解青藏高原东北缘盆山格局的形成和演化提供了重要依据。 相似文献
16.
南海北部珠江口—琼东南盆地白垩系—下渐新统记录了华南大陆边缘从主动陆缘向被动陆缘的转换过程。基于盆地构造-地层、单井相、地震相等特征的综合分析,结合南海中南部的沉积环境和区域构造演化,探讨南海北部白垩纪—渐新世早期的沉积环境演变及构造控制背景。研究发现: (1)南海北部白垩系广泛分布,古新统分布极为有限; 始新世早-中期,琼东南盆地只在部分凹陷深部发育了小规模的滨浅湖相和扇三角洲相沉积,珠江口盆地白云凹陷以大规模发育的湖泊相为特征; 始新世晚期—渐新世早期,琼东南盆地和珠江口盆地白云凹陷都受到海侵作用的影响,以海岸平原相和滨浅海相为主。 (2)构造演变包括5期:包括白垩纪安第斯型大陆边缘的“弧—盆”体系发育期,古新世区域隆升剥蚀山间盆地发育期,始新世早-中期裂陷发育,始新世晚期—渐新世早期陆缘破裂期,渐新世晚期东部海盆稳定扩张期。最后,探讨了南海盆地中生代末/新生代初的动力学转换过程及特征。 相似文献
17.
《Geodinamica Acta》2013,26(1-2):71-97
Most of the tectonic units cropping out in Western Tuscany are fragments of the Jurassic oceanic crust, ophiolitic successions, overlaid diachronously by Upper Cretaceous-middle Eocene carbonate and siliciclastic flysch successions with their Cenomanian-lower Eocene shalycalcareous basal complexes. These units, so called Ligurian, have been emplaced during the closure of the Ligurian-Piedmont Ocean. Ophiolite bearing debris flows are common in the flysch basins and their relationship with ophiolitic tectonic slices points to a strong relation between tectonics and sedimentation from the early compressive events of the Late Cretaceous. The tectonic activity reflects in a rough morphology of the ocean floor. It progressively influences the distribution and sedimentology of the turbidites. During middle Eocene this relationship begun very important and a paleogeographic reconstruction with prominent linear ophiolitic reliefs that bounded some turbiditic basins can be done. In our reconstruction the sedimentary and structural evolution can be framed in the context of strain partitioning, developed during the ocean closure, between subduction processes and ancient weakness zones crosscutting both the ocean and the Adria continental margin and reactivated in compressive regime. These weakness zones can be interpreted as transform faults of the Ligurian-Piedmont Ocean with prolongations in the Adria passive margin. The weakness zones crosscut the oceanic lithosphere and the Adria continental margin and interfered with the subduction processes. The activity of the weakness zones is reflected in the Ligurian Units architecture where two main structural strike trends of thrusts and folds axial planes occur. The first trend is WSW-ENE oriented and it is connected with the reactivation of the weaknesses zones. This first orientation developed progressively from Late Cretaceous to Pliocene, from oceanic to ensialic convergence (D1, D2, and D4 deformation phases). The second trend is NNE-SSW oriented and is related to the late Eocene continental collision and the subsequent translation to the NE of the oceanic units onto the Adria continental margin (D3 deformation phase). 相似文献
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19.
《Journal of Asian Earth Sciences》1999,17(1-2):157-181
The Kutai Basin occupies an area of extensive accommodation generated by Tertiary extension of an economic basement of mixed continental/oceanic affinity. The underlying crust to the basin is proposed here to be Jurassic and Cretaceous in age and is composed of ophiolitic units overlain by a younger Cretaceous turbidite fan, sourced from Indochina. A near complete Tertiary sedimentary section from Eocene to Recent is present within the Kutai Basin; much of it is exposed at the surface as a result of the Miocene and younger tectonic processes. Integration of geological and geophysical surface and subsurface data-sets has resulted in re-interpretation of the original facies distributions, relationships and arrangement of Tertiary sediments in the Kutai Basin. Although much lithostratigraphic terminology exists for the area, existing formation names can be reconciled with a simple model explaining the progressive tectonic evolution of the basin and illustrating the resulting depositional environments and their arrangements within the basin. The basin was initiated in the Middle Eocene in conjunction with rifting and likely sea floor spreading in the Makassar Straits. This produced a series of discrete fault-bounded depocentres in some parts of the basin, followed by sag phase sedimentation in response to thermal relaxation. Discrete Eocene depocentres have highly variable sedimentary fills depending upon position with respect to sediment source and palaeo water depths and geometries of the half-graben. This contrasts strongly with the more regionally uniform sedimentary styles that followed in the latter part of the Eocene and the Oligocene. Tectonic uplift documented along the southern and northern basin margins and related subsidence of the Lower Kutai Basin occurred during the Late Oligocene. This subsidence is associated with significant volumes of high-level andesitic–dacitic intrusive and associated volcanic rocks. Volcanism and uplift of the basin margins resulted in the supply of considerable volumes of material eastwards. During the Miocene, basin fill continued, with an overall regressive style of sedimentation, interrupted by periods of tectonic inversion throughout the Miocene to Pliocene. 相似文献
20.
Crete consists of a nappe pile that formed during Alpine subduction and collision. The lower nappes belong to the External Hellenides, whereas the uppermost nappe is ascribed to the Pelagonian Zone of the Internal Hellenides. The Uppermost Unit consists of several subunits including the Asterousia Crystalline Complex (ACC), which comprises metasedimentary rocks, (meta)granitoids and serpentinite, the protolith age and the tectonometamorphic evolution of which are largely unknown. In the present study, we present new structural, microfabric and geochronological data from the Uppermost Unit in the Melambes area (central Crete). 206Pb/238U zircon ages (LA-ICP-MS and ID-TIMS) indicate granitic and dioritic intrusions between 71.9 ± 0.6 and 76.9 ± 0.3 Ma. Identical ages have previously been obtained from comparable intrusions in eastern Crete and on Anafi. The composition and geochemical signature suggest an extended magmatic arc along the southern active margin of the Pelagonian-Lycian Block. Post-intrusive shearing transformed granite into orthogneiss, whereas diorite remained free from foliation, because of the lower amount of mechanically weak phases. Deformation microfabrics suggest top-to-the SE shearing under amphibolite facies conditions of the ACC and at greenschist facies conditions of rocks at the base of the ACC referred to as Akoumianos Greenschist. The Akoumianos Greenschist is considered as the northern part of the Pindos realm that was subducted underneath the Pelagonian-Lycian active margin. Based on our new and on published data, the following orogenic stages are suggested to have contributed to the evolution of the Hellenides during the Late Cretaceous to Eocene: (1) pre-middle Campanian collision and subduction of the Pindos lithosphere underneath the southern margin of the Pelagonian-Lycian terrane led to obduction and offscraping of serpentinized ocean floor and stacking of the ACC during amphibolite facies top-to-the SE thrusting, (2) formation of a Campanian magmatic arc along the Pelagonian-Lycian active margin; (3) Maastrichtian collision and stacking of the magmatic arc during top-to-the SE mylonitic shearing; (4) Palaeocene top-to-the SE greenschist-facies shearing of the ACC on top of the Akoumianos Greenschist; (5) Late Eocene thrusting of the Uppermost Unit on top of the Arvi and Pindos units. Thus, top-to the SE was the dominant shear sense in the southern Aegean from at least the mid-Late Cretaceous until the Eocene. 相似文献