共查询到20条相似文献，搜索用时 264 毫秒
1.
This paper presents histological data on the shell bones of different size (age) individuals of the basal pan-carettochelyid Kizylkumemys schultzi from the Upper Cretaceous (Cenomanian) of Usbekistan. Ontogenetic changes in the shell bone histology of Kizylkumemys schultzi correspond to those characteristic of other turtles. Comparison of the shell bone histology of Kizylkumemys schultzi with those of other pan-carettochelyids show similar histological structures, suggesting that this group is very conservative in the shell bone histology, which did not change significantly since the Cretaceous. Kizylkumemys schultzi and other pan-carettochelyids share prominent shell sculpture with all other pan-trionychians; shell sculpture of large pits and grooves and network of vertical and subvertical canals in the external cortex, with nanhsiungchelyids and pan-trionychids; reduced or absent scute sulci and lost or loose contact between peripherals and costals, with pan-trionychids; and loss of rib thickenings of costals, with adocids. According to new data, Kappachelys okurai from the Hauterivian-Barremian of Japan, previously considered as a pan-trionychid or pan-carettochelyid, could be either a pan-trionychian (sister taxon to Trionychia) or a pan-carettochelyid. 相似文献
2.
Dental histology of periodontal tissues (cementum, periodontal ligament and alveolar bone) has been studied in mammals, crocodylians and some basal tetrapods, but these structures have never been studied in titanosaur sauropods. The goal of this work was to study the structures of dental insertion in Titanosaurs. Like many physiological processes, histological analysis of titanosaur teeth shows hard tissue formation, characterized by a circadian rhythm. From thin sections it was possible to observe microstructures such as incremental lines of von Ebner, dentinal tubules and cross striations, all key to the understanding of developmental tooth dynamics. The structural and histological analyses carried out here on teeth of Late Cretaceous titanosaurs reveals the presence of acellular and cellular cementum, periodontal ligament, and alveolar bone, all structures necessary for a truly thecodont dentition. This is the first time documented for a dinosaur via histological tissue, and is an important finding that will help elucidate aspects of dinosaurian dentition, tooth replacement rate, feeding strategy, metabolism, and general biology. 相似文献
3.
松辽盆地是我国白垩系分布最广、厚度最大、发育最全的陆相沉积盆地。孢粉分析发现桫椤孢在松辽盆地白垩系中比较常见。但由于桫椤孢与桫椤科或者蚌壳蕨科具有亲缘关系。桫椤孢在地层中的发现不能明确表明桫椤科植物的存在。这种状况影响了我们对松辽盆地古环境和古气候的精确分析。白垩纪桫椤科矿化茎干化石在黑龙江省齐齐哈尔市克山县的发现为解决桫椤科植物在松辽盆地存在与否的难题提供了重要证据。该化石为桫椤科树蕨植物的茎干片段,包括髓、网状中柱、皮层。分体中柱的横截面呈U、W或S形,外围具有厚壁组织鞘,分体中柱末端朝向髓部或者皮层。髓和皮层由薄壁组织组成,其中分布有许多维管束和根。创伤组织在髓中常见。当前化石是我国第一个桫椤科茎干化石记录。它的发现表明白垩纪时期松辽盆地北部曾经分布着现今多生长于热带、亚热带的桫椤科树蕨祖先类群。结合与其伴生的一些登普斯基树蕨、本内苏铁茎干等化石证据,可能指示当时气候为热带或者亚热带。 相似文献
4.
5.
重庆綦江地质公园地质遗迹特征及其地质意义 总被引：1，自引：0，他引：1
綦江地质公园发育木化石、恐龙足迹、恐龙骨骼化石、鱼化石、沉积构造、丹霞地貌等地质遗迹景观,木化石和恐龙足迹为园区的导向型景观。木化石分布在侏罗系中统沙溪庙组(J2s)上部砂岩层中,砂岩层含钙质结核,在约300×200m2的砂岩层内共埋藏有60多根木化石,其中一半木化石为钙化作用形成。恐龙足迹集中分布在白垩系上统夹关组(K2j)砂泥岩层中,岩层发育交错层理、波痕和泥裂。在夹关组的3个层位中共发现329个恐龙足迹,其分别属于甲龙类、鸟脚类和兽脚类。园区地质遗迹分布在一套河湖相沉积层中,其形成于内陆河湖网形成之时(如木化石),并随着四川盆地周围的湖泊系统解体而发展(如恐龙足迹),最终随着河流由堆积作用为主的阶段转变为以侵蚀作用为主的阶段而减弱(如丹霞地貌)。白垩纪上统夹关组的恐龙足迹群形成于干热的环境,多类型的恐龙足迹集中分布反映了白垩纪晚期(夹关期)恐龙种群的丰富,恐龙足迹的发现为区域内寻找白垩系地层的恐龙骨骼化石提供了依据。 相似文献
6.
中国东部中新生代火山作用的pTtc模型与岩石圈演化 总被引：8，自引：0，他引：8
中国东北和华北地区中新生代火山岩的岩石化学研究表明 ,中新生代火山作用的深部过程均为逆时针的pTt轨迹 ,表现为岩浆源区从逐渐上升到下降的过程。中新生代火山作用的深部过程揭示的岩石圈演化历史为 :早侏罗世至早白垩世早期 ,岩石圈演化主要表现为逐渐减薄的过程 ,直至出现软流圈与地壳直接接触。从早白垩世晚期至中生代末 ,岩石圈演化为一增生过程。第三纪岩石圈演化为减薄过程 ,而到第四纪为岩石圈增生过程。中国东部现代岩石圈地幔是由中生代晚期 (K1末—K3)和第四纪两次增生事件形成的 相似文献
7.
The panchelid turtle Linderochelys rinconensis de la Fuente, Calvo and González Riga, 2007 was described on the basis of several postcranial elements from the Rio Neuquén Subgroup of Loma del Lindero site, near Rincon de los Sauces (Neuquén, Argentina). New preparation of the type material revealed new parts of the animal, including cervical vertebrae, parts of the carapace and a right tibia. The study of the newly recovered material herein improves our knowledge of the macroanatomy of this taxon. The first costal shows an axillary buttress similar to Australasian chelids and the cervical vertebrae morphology suggests a short-necked chelid condition. The re-examination of the type material of Linderochelys and the discovery of new material allowed new studies on microanatomy, osteohistology and diagenesis. Osteohistology suggests some similarities with Patagonian Cretaceous and Palaeocene Yaminuechelys, based on the presence of parallel-fibred bone in the external cortex and a much thinner internal cortex. Paleoecological studies on the proportions of forelimbs and microanatomy point towards aquatic or semi-aquatic habits, closely related to the condition seen in some extant South American chelids, such as Phrynops hilarii, Phrynops geoffroanus, and Mesoclemmys gibba. The fossil-diagenetic processes inferred substitution, fracturing, plastic deformation and permineralization events. Combined analyses through scanning electron microscopy with energy-dispersive X-ray spectrometry and petrographic studies revealed the substitution of hydroxyapatite by francolite. Permineralization stages include infilling of vascular canals, trabeculae and fractures with iron oxides and carbonate minerals during their burial history. 相似文献
8.
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
9.
A first report of discovery of spherules, glassy balls, highly magnetic fine dust and microbracciated matrix in the Fatehgarh Formation of Barmer Basin, Rajasthan, India is being presented in this paper. The Fatehgarh Formation is a mixed siliciclastic, carbonate and phosphorite formation of Cretaceous age in the Barmer Basin that comprises sediments of Middle Jurassic to Lower Eocene age. The phosphorite zone in the Fatehgarh Formation is 8 metre-thick zone that comprises phosphatic sandstone, bone bed, bedded phosphorite and phosphatic and non phosphatic gastropod beds. The spherules occur in a thin phosphatic-clay mud and silt band of bone bed, which also yielded a very rich and diverse microvertebrate assemblage with a dominant Late Cretaceous (Maastrichtian) form of Igdabatis along with forms comprising of Semionodontid, Lapisosteum and Enchodontid. The end Cretaceous is marked for a mass extinction of numerous species including dinosaurs. An extraterrestrial impact is interpreted as the reason for this mass extinction. Whether these spherules are related to the volcanic source or K/T Boundary impact ejecta found at Caribbean and Gulf of Mexico region needs detailed chemical and age characterization for which study is in progress. 相似文献
10.
Well-preserved Cretaceous trunk fragments of Cycadeoidea (Cycadeoidaceae) were recently found in Keshan County, Heilongjiang Province, Northeast China. These fossils represent important evidence of the distribution of this group of plants in East Asia. In these trunk fragments, the stem cortices and leaf bases with cones are preserved. The leaf bases are rhombic with cones infrequently distributed among leaf bases. The cortex is broad and consists of fundamental parenchyma cells, numerous secretory ducts and C-shaped leaf traces with adaxial secondary xylem and abaxial secondary phloem. The genus Cycadeoidea, which is widely distributed in the Cretaceous deposits of East Asia, North America and Western Europe, was an important component of Cretaceous floras. Bennettitalean trunk fossils with well-preserved anatomical structures are rarely known from China. These fossils are important for studies of the evolution of genus Cycadeoidea and for stratigraphic correlation. 相似文献
11.
《International Geology Review》2012,54(3):416-426
The area is divided into two parts: 1) elevated Precambrian basement with platform-type structures, and 2) an area of subsidence occupied by the Pricaspian depression; these structural subdivisions are separated by an escarpment. The Cretaceous stratigraphic section is subdivided into groups, based on lithological (geoelectrical) and faunal properties, correlated between the uplifted and down-warped areas. Eleven and twelve groups have been defined in the Lower and Upper Cretaceous, respectively. Variations in lithologles of the groups were controlled by the Voronezh massif and the Pricaspian depression. There was a gradual transgression of the Cretaceous sea from basin to elevated areas, on which some groups were bevelled by erosion. Deep downwarping of the salt dome area took place in the Valanginian and Hauterivian. The area near the Voronezh massif also subsided in the Hauterivian. Sedimentation took place on a geotectonically levelled surface during the greater part of the Barremian, Aptian, Touronian-Coniacian, Santonian and, partially, in the Cenomanian and Campanian stages. Intense warping of the Pricaspian depression occurred in the Albian and Maestrichtian and is marked by a sudden increase in the thickness of deposits of these ages and the appearance of Danian rocks. Thinning occurs on the Uzen-Ichinsk uplift and in the Upper Cretaceous, in the region of the marginal escarpment. — J.D. Haun 相似文献
12.
自从20世纪60年代初在山东诸城发现第一具恐龙骨架“巨型山东龙”以来,一系列具有代表性的恐龙骨骼化石在诸城白垩纪地层中被发现,特别是埋藏于诸城晚白垩世地层中恐龙骨骼化石群,最为引人注目。目前研究发现了包括鸭嘴龙类、角龙类、暴龙类等在内的多种恐龙类型,为丰富我国东部白垩纪恐龙动物群的研究提供了新的宝贵材料。该文系统总结和归纳了近些年来在诸城晚白垩世地层中发现的恐龙骨骼化石及其所代表的恐龙动物群类型的研究成果,同时又提出了目前依然存在的一些亟待解决的关键问题和研究意义,有助于下一步更好的深入研究诸城晚白垩世恐龙动物群。 相似文献
13.
华南构造演化的基本特征 总被引：95，自引：11，他引：84
华南至少经历了4期区域规模的大陆动力学过程,除新元古代和晚中生代具有活动陆缘背景外,均在板块内部发生并完成。华夏块体是一个以新元古代岩石为主体构成的前南华纪基底,不是稳定的克拉通古陆,经历了聚合-裂解-再聚合的复杂构造演化。志留纪发生的板内碰撞-拼合事件使华夏块体与扬子块体再次缝合,形成真正统一的中国南方大陆。在震旦纪—早侏罗世期间,整个华南基本处于陆内滨海-浅海-斜坡环境,内部没有切穿岩石圈的断层,没有大规模幔源岩浆和火山喷发的记录,多次构造变形与岩浆活动均在统一的华南岩石圈之上进行。经过早—中侏罗世的构造体制转换,才演化成为晚中生代西太平洋活动大陆边缘的一部分。从早到晚,华南岩石圈经历了多期、幕式的生长,以侧向增生为主(块体拼合),垂向生长为辅(岩浆上侵)。到晚中生代,在古太平洋板块俯冲和陆内伸展的背景下,形成了独特的华南盆岭构造。长期的板内构造演化和多期的花岗岩浆活动使华南具有很好的成矿条件,成为各种矿产与资源的富集区。新元古代南华纪和晚中生代晚侏罗世—早白垩世是华南最有利的成矿期,尤以后者矿种最多、储量最大。 相似文献
14.
大兴安岭东南部太平山地区断裂控矿作用及控矿应力场 总被引：1，自引：0，他引：1
根据控矿断裂构造的分期配套及其交切关系研究 ,发现大兴安岭东南部太平山地区内生金属矿床的形成与中生代多次转换的区域构造应力场及其所形成的断裂直接相关。太平山地区在中生代经历了 4期具不同区域构造应力场的控矿构造运动 :①晚侏罗世晚期至早白垩世早期 ,形成NEE走向的矿化隐爆角砾熔岩带 ;②早白垩世晚期 ,造成了大量近EW (或NWW )和NW (或NNW )走向的共轭张_张扭性断裂 ,该期为主成矿期 ;③晚白垩世 ,形成并复活了近SN向 (或NNE向 )和NE65°的两组共轭张扭性断裂 ,沿断裂充填了中酸性脉岩和铁矿 ;④晚白垩世之后 ,发育NNW向挤压的区域构造应力场 相似文献
15.
西藏南部岗巴地区白垩纪化石碳酸盐岩微相与沉积环境研究 总被引：2，自引：2，他引：0
西藏南部岗巴地区发育着我国最完整的海相白垩纪地层,对该时期海相沉积演化特征的研究,能够较好地反映该地区在印度板块和欧亚板块碰撞前的演化信息。对白垩纪岗巴地区的化石碳酸盐岩微相进行了较为详细和系统的分析与研究。初步识别出12种微相和7种生物相类型,在此基础上对西藏特提斯白垩纪沉积环境的演变进行了初步的探讨。西藏特提斯在白垩纪的海水进退规程总体上表现为：Berriasian-Aptian期发生海侵,Albian早期发生海退,Albian晚期-Cenomanian期水体有进一步加深的趋势,Turonian期再次发生大规模海侵,Santonian-Coniacian期海侵持续进行,Maastrichtian期海水急剧变浅。 相似文献
16.
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
17.
《Gondwana Research》2006,9(4):579-584
A first report of discovery of spherules, glassy balls, highly magnetic fine dust and microbracciated matrix in the Fatehgarh Formation of Barmer Basin, Rajasthan, India is being presented in this paper. The Fatehgarh Formation is a mixed siliciclastic, carbonate and phosphorite formation of Cretaceous age in the Barmer Basin that comprises sediments of Middle Jurassic to Lower Eocene age. The phosphorite zone in the Fatehgarh Formation is ∼8 metre-thick zone that comprises phosphatic sandstone, bone bed, bedded phosphorite and phosphatic and non phosphatic gastropod beds. The spherules occur in a thin phosphatic-clay mud and silt band of bone bed, which also yielded a very rich and diverse microvertebrate assemblage with a dominant Late Cretaceous (Maastrichtian) form of Igdabatis along with forms comprising of Semionodontid, Lapisosteum and Enchodontid. The end Cretaceous is marked for a mass extinction of numerous species including dinosaurs. An extraterrestrial impact is interpreted as the reason for this mass extinction. Whether these spherules are related to the volcanic source or K/T Boundary impact ejecta found at Caribbean and Gulf of Mexico region needs detailed chemical and age characterization for which study is in progress. 相似文献
18.
We describe a traverse across the Cordillera Real and sub-Andean Zone of Ecuador, poorly known areas with very little detailed mapping and very little age control. The spine of the Cordillera comprises deeply eroded Triassic and Jurassic plutons, the roots of a major arc, emplaced into probable Palaeozoic pelites and metamorphosed volcanic rocks. The W flank comprises a Jurassic (?) submarine basaltic–andesitic volcanic sequence, which grades up into mixed Jurassic/Cretaceous volcanic and sedimentary rocks of the Inter-Andean Valley. The sub-Andean Zone, on the E flank of the Cordillera, comprises a newly recognized Cretaceous basin of cleaved mudrocks, quartz arenites and limestones. East of the syndepositional Cosanga Fault, the Cretaceous basin thins into a condensed sequence that is indistinguishable from the rocks of the adjacent hydrocarbon-bearing Oriente Basin. The principal penetrative deformation of the Cordillera Real was probably latest Cretaceous/Palaeocene. It telescoped the magmatic belts, but shortening was largely partitioned into the pelites between plutons. The plutons suffered inhomogenous deformation; some portions completely escaped tectonism. The pelites conserve two foliations. The earliest comprises slaty cleavage formed under low- or sub-greenschist conditions. The later is a strong schistosity defined by new mica growth. It largely transposed and obliterated the first. Both foliations may have developed during a single progressive deformation. We find inappropriate recent terrane models for the Cordillera Real and sub-Andean Zone of Ecuador. Instead we find remarkable similarities from one side of the Cordillera to the other, including a common structural history. In place of sutures, we find mostly intrusive contacts between major plutons and pelites. Triassic to Cretaceous events occurred on the autochthonous western edge of the Archaean Guyana Shield. The latest Cretaceous–Paleocene deformation is interpreted as the progressive collision of an oceanic terrane(s) with the South American continent. Young fault movements have subsequently juxtaposed different structural levels through the Cordillera Real orogen. 相似文献
19.
The scarcity of diagnostic skeletal elements in the latest Cretaceous theropod record of the Ibero-Armorican domain (southwestern Europe) prevents to perform accurate phylogenetic, paleobiogeographic, and diversity studies. In contrast, eggs and eggshells of theropod dinosaurs are relatively abundant and well known in this region from which several ootaxa have been described. Here, we describe the first Late Maastrichtian theropod ootaxon (Prismatoolithus trempii oosp. nov.) from SW Europe and demonstrate that oological record can be used as a proxy for assessing diversity of egg-producers and may help to complement their scarce bone record. The performed analyses indicate that the theropod taxa and ootaxa reach their diversity maxima during the Late Campanian and start to decrease near the Campanian–Maastrichtian boundary at both global and regional scales. The oological diversity of theropods in the Ibero-Armorican domain is consistent with the theropod diversity identified at high taxonomic level. Two distinct assemblages of theropod ootaxa can be recognized in the latest Cretaceous of the Ibero-Armorican domain. Their temporal transition can be correlated with other dinosaur faunal changes recorded in the region. This faunal turnover took place around the Early–Late Maastrichtian boundary, involving ornithopods, sauropods, ankylosaurs and, according to the present results, theropods as well. 相似文献
20.
Jiang Y.-H.Wang G.-C. 《矿物岩石地球化学通报》2016,(6):1073-1081
During late Mesozoic times, extensive magmatism took place in SE China, forming widespread granitoids. Recently, we identify a series of Early Jurassic mafic rocks and A-Type granites in southern Jiangxi and western Fujian provinces. The Early Jurassic A-Type granites occur as a NE-Trending belt. By integrated previously published data, we find that there are other three A-Type granite belts in SE China, i.e., the Lite Jurassic, Early Cretaceous, and Late Cretaceous A-Type granite belts, respectively, all of which are NE-Trending, parallel to the present coastline. The Lite Jurassic belt is located further inland, to the west of the Early Jurassic belt, whereas the Early Cretaceous belt almost overlaps the Early Jurassic belt and the Lite Cretaceous belt is located at the coastal area of SE China. Integrated these observations, we propose a repeated slab-Advance-retreat model for the late Mesozoic magmatie evolution of SE China. 相似文献