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1.
西藏改则物玛地区发现了约33属47种及未定种的晚侏罗世珊瑚化石。珊瑚化石指示其所在的地层并非是原来认为的早二叠世下拉组,而是晚侏罗世牛津期—基末里期的吐卡日组。基于对改则物玛北剖面的研究,在吐卡日组之下新建了晚侏罗世萨波直不勒组。进而将班公湖-怒江地层区西段的上侏罗统自下而上划分为萨波直不勒组、吐卡日组和沙木罗组。改则县物玛乡北部吐卡日组的发现证明吐卡日组在班公湖-怒江地层区西部有着更广泛的分布。将“下拉组”修订为吐卡日组也表明班公湖-怒江地层区改则地区物玛段并不存在二叠系灰岩与侏罗系木嘎岗日岩群碎屑岩的构造混杂现象。吐卡日组以浅海碳酸盐台地相的生物礁亚相、鲕粒滩亚相为特征,厚度也十分可观,指示其具有良好的生油和储油潜力,班公湖-怒江地层区西段及南北两侧的碳酸盐岩相上侏罗统的油气前景评价工作应予以重视。 相似文献
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在班公湖—怒江缝合带西段铁杂—日雍构造混杂岩带物玛地区,原划为上石炭统拉嘎组地层中新发现了中生代孢粉化石14种及未定种,这些化石的发现为将该地层修订为下白垩统多尼组提供了古生物学依据。上石炭统拉嘎组被修订后,研究区班公湖—怒江缝合带不再存在拉嘎组混杂在中生代地层中的现象。同时本次研究在铁杂—日雍构造混杂岩带以南的冈底斯—腾冲地层区物玛分区原划为上石炭统拉嘎组中,发现中生代孢粉化石10种及未定种,并在其灰岩夹层中发现晚侏罗世珊瑚化石6种及未定种,同时在原划分为中二叠统下拉组中也发现晚侏罗世珊瑚化石。根据化石时代和区域地层对比,拉嘎组和下拉组分别被修定为上侏罗统萨波直不勒组和吐卡日组。至此,物玛分区的上侏罗统以萨波直不勒组和吐卡日组为代表,与其北侧的班公湖—怒江地层区上侏罗统可进行对比。本文以班公湖—怒江缝合带西段铁杂—日雍构造混杂岩带为例,证实在混杂岩带开展古生物学研究非常必要。 相似文献
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在班公湖—怒江缝合带西段铁杂—日雍构造混杂岩带物玛地区,原划为上石炭统拉嘎组地层中新发现了中生代孢粉化石14种及未定种,这些化石的发现为将该地层修订为下白垩统多尼组提供了古生物学依据。上石炭统拉嘎组被修订后,研究区班公湖—怒江缝合带不再存在拉嘎组混杂在中生代地层中的现象。同时本次研究在铁杂—日雍构造混杂岩带以南的冈底斯—腾冲地层区物玛分区原划为上石炭统拉嘎组中,发现中生代孢粉化石10种及未定种,并在其灰岩夹层中发现晚侏罗世珊瑚化石6种及未定种,同时在原划分为中二叠统下拉组中也发现晚侏罗世珊瑚化石。根据化石时代和区域地层对比,拉嘎组和下拉组分别被修定为上侏罗统萨波直不勒组和吐卡日组。至此,物玛分区的上侏罗统以萨波直不勒组和吐卡日组为代表,与其北侧的班公湖—怒江地层区上侏罗统可进行对比。本文以班公湖—怒江缝合带西段铁杂—日雍构造混杂岩带为例,证实在混杂岩带开展古生物学研究非常必要。 相似文献
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措勤盆地东部班戈县保吉乡各昌茶玉地区发现晚侏罗世珊瑚化石约10属15种及未定种,分别为Actinaraea?sp.,Allocoenia?sp.,A.matheyi(Koby),Clausastraea?sp.,Hydnophora?sp.,Latiastraea minima(Koby),Latiastraea?sp.,Meandraraea?sp.,Stylosmilia crassitheca Liao et al Li,S.corallina Koby,Thamnasteria?sp.,T.concinna(Goldfuss),Thecosmilia.baojiensis sp.nov.,Thecosmilia?sp.,Trocharaea cf.patelliformis Gregory等。化石指示各昌茶玉剖面第1—41层地层时代为晚侏罗世牛津期—基默里奇期。珊瑚化石产出的层位原来被认为是混杂在中侏罗世蛇绿岩中的中二叠统下拉组,本文根据剖面中化石及岩性组合特点将其修订为上侏罗统萨波直不勒组,并得出了该地区不存在原来所认为的中二叠统下拉组与中侏罗统蛇绿岩构造混杂现象的认识。本次萨波直不勒组与改则县物玛乡抢古村建组剖面相对比,其岩性更细、灰岩夹层更多,珊瑚化石更为丰富,代表了更远离陆源碎屑源区的沉积环境,进一步证明晚侏罗世冈底斯地区地势是从北向南逐渐加深的,措勤盆地在晚侏罗世处于活动型深海-半深海相和上斜坡相的沉积环境中。保吉地区萨波直不勒组顶部存在上斜坡相68 m厚黑色泥页岩,TOC(总有机碳)平均值为0.83%,属于中等-好烃源岩,剖面第20层12 m厚黑色泥岩TOC值为0.65%,属于中等烃源岩。萨波直不勒组顶部为上斜坡相沉积,分布范围应该比上覆的吐卡日组更广泛。经计算,措勤盆地内萨波直不勒组烃源岩的生烃量约为44.373亿吨。萨波直不勒组的泥页岩为措勤盆地提供了充足的油源保障,同时其中的碳酸盐岩夹层也可能是油气有利储层,建议对上侏罗统萨波直不勒组开展钻探取样工作,获取更为翔实丰富的有机地球化学参数。 相似文献
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西藏班戈县保吉地区各昌茶玉剖面发现晚侏罗世珊瑚化石约12属16种,分别为Calamophylliopsis?sp.,Clausastraea?sp.,Epistreptophyllum cylindratum Milaschevitsch,Epistreptophyllum sp.,Heliocoenia aff.etalloni Koby,Kobyastraea?sp.,Montlivaltia tenuilamellats Roniewicz,Montlivaltia?sp.,Myriophyllia?sp.,Pseudocoenia hexaphyllia(d’Orbigny),Pseudocoenia?sp.,Rhipidogyra?sp.,Stephanastraea?sp.,Stylina?sp.,Stylina cf.subramosa de Fromentel,Thecosmilia?sp.等。化石指示各昌茶玉剖面上部第42—80层时代为晚侏罗世牛津期—基默里奇期,表明各昌茶玉剖面地层并不属于原划的中二叠统下拉组。本文依据化石及岩性特点将其修订为上侏罗统吐卡日组。根据保吉地区的吐卡日组与上下地层的接触关系及其岩性变化可划分为上下两段地层,各昌茶玉剖面代表吐卡日组下段地层,主要为厚层碳酸盐岩夹少量泥页岩及多层礁灰岩。久朗仓剖面代表吐卡日组上段地层,为一套碳酸盐岩夹大量粗碎屑岩地层。吐卡日组下段在措勤盆地内部、班公湖—怒江缝合带内广泛分布,指示晚侏罗世措勤盆地发育大面积广阔稳定的碳酸盐岩台地,其中生物礁表明晚侏罗世碳酸盐岩台地具有优越的油气生成和储集条件。 相似文献
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实测西藏改则县甲不拉东剖面过程中,在前人原划分为二叠系下拉组中采集到属于晚侏罗世时代的生物化石(Microso lena sp.Meandronhyllia、Thecosmilia sp.Burgundia sp.Buneia sp.),根据岩石组合及生物化石面貌等区域地层对比,将该套地层确定为上侏罗统吐卡日组。该套地层的确定,为班公湖-怒江结合带侏罗纪珊瑚动物群的研究、洋盆的萎缩、消亡及洋-陆转化提供新的基础地质资料。 相似文献
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西藏班戈县扎穷地区古生界混杂岩块中发现中生代化石 总被引：1，自引：0，他引：1
西藏班戈县新吉乡扎穷地区新发现了晚侏罗世珊瑚化石10属11种:Stylina?sp.、Goniocora annulata Roniewicz,Epistreptophyllum cf.cornutiformis(Gregory),Solenocoenia?sp.,Calamophylliopsis moreauana(Michelin),Thamnasteria?sp.,Clausastraea?sp.、Isastraea?sp.,Montlivaltia?sp.,Montlivaltia tenuilamellata Roniewicz,Thecosmilia?sp.,早白垩世珊瑚化石3属3种:Eohydnophora tosaensis YabeEquchi、Clausastraea tabulate Morycowa、Stylosmilia baojiensis sp.nov.,早白垩世腹足类化石5属8种:Mesoglauconia neumayri(Nagao),Rhabdocolpus asiaticum Djalilov,Pseudomesalia bangoinensis Yu,Mesoglauconia bicarinata(Hamlin),Mesoglauconia arkelli Mennessier,Nerinea domaensis Yu,Mesoglauconia cf.arkelli Mennessier,Microschizacf.inflata Orbigny。根据上述化石,原中二叠统下拉组被修订为上侏罗统吐卡日组和下白垩统朗山组,原下石炭统永珠组被修订为下白垩统多尼组。上述地层时代修订的意义如下:(1)上侏罗统吐卡日组的分布范围向南可以到达扎穷地区,进一步否定了冈底斯南部在晚侏罗世是古陆的认识。(2)朗山组和多尼组的发现指示早白垩世海相地层分布范围向南可以扩展到扎穷地区,这对冈底斯南部在早白垩世是古陆或岛弧的认识提出了质疑。(3)扎穷地区不存在古生界岩块与中侏罗统蛇绿岩构造混杂的现象。本区的构造活动强度并不强烈,没有造成古生界岩块大规模出露并混杂堆积的现象。(4)因为吐卡日组、多尼组和朗山组分布范围的扩大、措勤盆地中部构造破坏并不强烈,所以措勤盆地的油气前景进一步变好。 相似文献
9.
西藏保吉地区晚侏罗世珊瑚动物群的发现及其意义 总被引：1，自引：0，他引：1
西藏班戈县纳木错西岸的保吉地区新发现了晚侏罗世牛津期-基默里奇期珊瑚化石14属21种及未定种。它们分别是:Goniocoracf.annulata Roniewicz,Calamophylliopsis cf.moreauna(Michelin),Thecosmilia?sp.,Calamophylliopsis?sp.,Micrabacia?sp.,Stylosmilia michelini M.-Edwards et Haime,Cladophyllia turbinata(Gregory),Cladophyllia?sp.,Thamnasteria?sp.,Ovalastraea?sp.,Montlivaltia?sp.,Latiastraea goldfussi(Koby),Donacosmilia cf.silinensis Liao,Thecosmilia baingoinensis sp.nov.,Placophyllia cf.rugosa Becker,Cladophyllia rollieri Koby,Thecosmilia cf.costata Fromentel,Goniocora?sp.,Pleurocora crassa(Reuss),Calamophylliopsis moreauna(Michelin),Trocharaea?sp.等。这些珊瑚表明其所在地层的时代不是中二叠世,因此不能划为中二叠统下拉组。通过与已有上侏罗统岩石地层单位的对比分析,该套地层应属于吐卡日组。本研究吐卡日组的发现证明了保吉地区的上侏罗统并非缺失,而是礁滩相碳酸盐岩地层。这一发现进一步表明了措勤盆地上侏罗统并非缺失,也不仅仅是接奴群或者是拉贡塘组为代表的碎屑岩沉积,而且也有上侏罗统礁滩相碳酸盐岩地层。这一发现为开展措勤盆地礁滩相上侏罗统的油气勘探工作提供了地层古生物学证据,因此,笔者建议将上侏罗统吐卡日组作为措勤盆地新的油气勘探目标层系。 相似文献
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拉萨和羌塘地块拼合形成了青藏高原的核心,但迄今对两者的具体拼合时间仍存在激烈的争论。为进一步寻找约束两者碰撞时限的地质证据,对拉萨地块晚侏罗世—早白垩世地层的磁组构特征进行研究。结果显示:晚侏罗世地层磁组构特征显示其遭遇过较强的构造应力,吐卡日组地层磁化率主轴k_1方位与地层面斜交,但经地层校正后,k_1方位与区域褶皱方向一致,表明应力方位为北北东—南南西向;萨波直不勒组地层k_1方位在地层校正前平行于层面,指示了垂直于主压应力的方向,推断晚侏罗世地层磁组构记录了同一期应力,应力方向均为北北东—南南西向。早白垩世多尼组地层磁组构显示其后期遭受的构造应力场强度弱,且与晚侏罗世应力并非同一期。因此,通过对比晚侏罗世与早白垩世地层的磁组构特征,认为保吉地区晚侏罗世地层磁组构记录了北北东—南南西向较强的构造应力,推断该期应力来源于拉萨-羌塘地块的碰撞拼合事件,而多尼组地层并未受该期应力场的影响,仅记录了区域褶皱隆起时的应力场。 相似文献
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在拉萨北部堆龙德庆县马乡设兴村设兴组命名剖面顶部灰黑色泥岩夹层中的SX31样品中发现了Osmundacidites sp．，Deltoidospora sp．，Leiotriletes sp．，Purwtatisporites sp．，Ilexpollenites sp．，Quercoidites sp．，Caryapollenites sp．，Betulaceoipol—lenites sp．，Sporopollis?sp．，Ulmipollenites sp．，Compositoipollenites sp．，Tricolporollenites sp．等孢粉化石，主要为被子植物和蕨类植物花粉，未发现裸子植物花粉。这些孢粉指示的地层时代接近于始新世——渐新世。在剖面下部的4件样品中零星发现了Tricolpites sp．，Shizaeoisporites sp．，Compositoipollenites?sp．，Leiotriletes sp．，Cyathidites sp.，Neoraistrackia sp．，Converrucosisporrites sp．，Cycadopites sp．，PinuspoUenites sp．，Retitricolpites sp．等孢粉化石，指示的地层时代可能略早。从而说明设兴组与上覆林子宗群之间的角度不整合所代表的构造运动发生在始新世——渐新世或其后。 相似文献
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对若尔盖地块震旦系—志留系中黏土矿物进行了X衍射分析。结果表明,震旦系至志留系中伊利石结晶度0.25相似文献
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A fossil assemblage collected around 3.5 m amsl from Ezeiza, Buenos Aires province, have AMS 14C ages of ca. 33,000 to ca. 40,000 yr BP, whereas in the literature is a report of a conventional 14C age of >43,000 yr BP. An OSL age from the overlying deposit corresponds to ca. 22,000 yr. The samples contain marine fossils: mollusks, balanids and corals (Astrangia). La Coronilla (Uruguay, attributed to MIS 5e) is the locality most related to Ezeiza faunistically, despite is not the nearest one. In consequence, the relationship should be addressed to a more similar age and environment than others. The fauna indicates a higher water temperature than today. In Ezeiza exclusively cold water taxa are absent, and we found seven warm taxa with their southern distribution limit displaced northwards today, plus other six at their southern distribution limit. Around 60% of all the species and more than 70% of the individuals are of warm-temperate waters. In sum, although prima facie the numerical ages would locate the deposit in MIS3, faunistic, temperature, and height evidences show that the Ezeiza mollusk assemblage belong to MIS5e. A stronger than presently Brazil warm current, reaching Southern latitudes, may explain the changes in geographical ranges. 相似文献
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众所周知,藏北高原高寒、年降水量少,岩石多呈物理风化。近年来通过1∶25万措麦区幅地质调查,在工作区发现多个喀斯特灰岩溶洞,显然它们不是目前该地区气候条件所能形成的,而应该是(亚)热带气候喀斯特的产物。在所发现的数个岩溶洞穴中,以昂仁县阿木龙溶洞规模较大、洞穴堆积层最发育。1阿木龙溶洞基本特征阿木龙溶洞位于昂仁县阿木龙,地理坐标为N30°36'、E86°00'。洞口朝向北东35～40°。洞口海拔5000m,并高于附近侵蚀基准面约16m。溶洞总体为穴状(地下厅),洞口形态呈拱形。主体洞深约20m,高度、深度由洞口往里均变小,分别为5.1～2.2m和… 相似文献
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《Quaternary Science Reviews》2007,26(17-18):2090-2112
The geomorphology and morphostratigraphy of numerous worldwide sites reveal the relative movements of sea level during the peak of the Last Interglaciation (Marine Isotope Stage (MIS) 5e, assumed average duration between 130±2 and 119±2 ka). Because sea level was higher than present, deposits are emergent, exposed, and widespread on many stable coastlines. Correlation with MIS 5e is facilitated by similar morphostratigraphic relationships, a low degree of diagenesis, uranium–thorium (U/Th) ages, and a global set of amino-acid racemization (AAR) data. This study integrates information from a large number of sites from tectonically stable areas including Bermuda, Bahamas, and Western Australia, and some that have experienced minor uplift (∼2.5 m/100 ka), including selected sites from the Mediterranean and Hawaii. Significant fluctuations during the highstand are evident at many MIS 5e sites, revealed from morphological, stratigraphic, and sedimentological evidence. Rounded and flat-topped curves derived only from reef tracts are incomplete and not representative of the entire interglacial story. Despite predictions of much different sea-level histories in Bermuda, the Bahamas, and Western Australia due to glacio- and hydro-isostatic effects, the rocks from these sites reveal a nearly identical record during the Last Interglaciation.The Last Interglacial highstand is characterized by several defined sea-level intervals (SLIs) that include: (SLI#1) post-glacial (MIS 6/5e Termination II) rise to above present before 130 ka; (SLI#2) stability at +2 to +3 m for the initial several thousand years (∼130 to ∼125 ka) during which fringing reefs were established and terrace morphology was imprinted along the coastlines; (SLI#3) a brief fall to near or below present around 125 ka; (SLI#4) a secondary rise to and through ∼+3–4 m (∼124 to ∼122 ka); followed by (SLI#5) a brief period of instability (∼120 ka) characterized by a rapid rise to between +6 to +9 m during which multiple notches and benches were developed; and (SLI#6) an apparently rapid descent of sea level into MIS 5d after 119 ka. U/Th ages are used to confirm the Last Interglacial age of the deposits, but unfortunately, in only two cases was it possible to corroborate the highstand subdivisions using radiometric ages.Sea levels above or at present were relatively stable during much of early MIS 5e and the last 6–7 ka of MIS 1, encouraging a comparison between them. The geological evidence suggests that significant oceanographic and climatic changes occurred thereafter, midway through, and continuing through the end of MIS 5e. Fluctuating sea levels and a catastrophic termination of MIS 5e are linked to the instability of grounded and marine-based ice sheets, with the Greenland (GIS) and West Antarctic (WAIS) ice sheets being the most likely contributors. Late MIS 5e ice volume changes were accompanied by oceanographic reorganization and global ecological shifts, and provide one ominous scenario for a greenhouse world. 相似文献
17.
西藏措勤-申扎地层分区新建中--上侏罗统仁多组 总被引：1，自引：0，他引：1
在西藏措勤西部昂拉仁错南部新发现一套侏罗纪地层，其岩性和古生物组合特征均不同于邻区侏罗系。通过详细的层型剖面测制和对比研究，将其新建为组级岩石地层单位——仁多组。指定并详细描述了正层型剖面，讨论了仁多组的岩石组合特征、地层接触关系、基本层序和沉积环境。根据仁多组的生物化石组合及其地层分布建立了2个生物组合带，并确定仁多组下段与中-上段分属为中、上侏罗统。仁多组的建立为认识区域地层系统及地质演化提供了新资料。 相似文献
18.
19.
西藏念青唐古拉山闪长质片麻岩锆石U-Pb年龄 总被引：7，自引：1，他引：7
采用高精度离子探针(SHRIMP)测年方法对西藏念青唐古拉山英云闪长质和石英闪长质正片麻岩中锆石的成因和形成时代进行了研究.在阴极发光图像中,片麻岩中的锆石具有较好的晶形,并显示出清晰的岩浆锆石韵律环带结构.离子探针分析表明,片麻岩中的锆石具有高的Th/U比值.对2颗片麻岩中的锆石进行了离子探针U-Pb测年,测得英云闪长质和石英闪长质片麻岩中的锆石206Pb/238U结晶年龄分别为58.5Ma±0.7Ma和63.5Ma±0.8Ma.这一结果意味着念青唐古拉山正片麻岩形成于安第斯型的冈底斯岩浆作用期间. 相似文献
20.
A. M. Korotkii T. A. Grebennikova L. P. Karaulova N. I. Belyanina 《Russian Journal of Pacific Geology》2007,1(4):352-365
In the Ussuri-Khanka depression of Primorye, the Quaternary alluvial-lacustrine and lacustrine sedimentogenesis progressed under conditions of transgressive accumulation in response to the depression tectonic subsidence and recurrent climatic fluctuations. The alluvial dams and irregular accumulation are proved to have been the leading factors of lakes’ formation within the depression. As is shown, fluctuations of the water level in limnic reservoirs depended on the climatic changes. New data considered in this work confirm the lacustrine genesis of a greater part of the Middle Pleistocene-Holocene sedimentary succession in the Khanka depression. Two transgressive phases, when the water level in the lakes rose by 1.5–2.0 m above the present one, are established for the Subboreal. The general conclusion is that the mesorhythmic structure of the sedimentary succession in the Ussuri-Khanka depression reflects the influence of climatic fluctuations in the Late Cenozoic. 相似文献