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1.
Two new genera and three new species of the Mesozoic family Aeotheogrammatidae are described from the Lower Cretaceous of Yixian Formation (Liaoning Province, China): Cyclicogramma rotundum gen. et sp. nov. and Aetheogramma bistriatum sp. nov. from Huangbanjigou, and Curtogramma ovatum gen. et sp. nov. from Dawangzhangzi. The hind wing of Cyclicogramma rotundum gen. et sp. nov. differs from that of other species by its smaller size, its overall shape, RP bearing only two oblique radial branches, and its configurations of CuP, AA1, and AA2. Aetheogramma bistriatum sp. nov. is closely related to A. speciosum Ren and Engel, 2008, but distinguished from the latter by its distinctive configuration of RP1, and the narrower and longer AA2 space in the hind wing. Curtogramma ovatum gen. et sp. nov. is distinguished from all other species of the family by the forewing with M forking very far from the wing base.  相似文献   

2.
Cratosmylus magnificus gen. et sp. nov., type genus and species of the new osmylid subfamily Cratosmylinae, is described from the Lower Cretaceous of the Crato Formation, Brazil. The relationships of this taxon remain uncertain within the Osmylidae, mainly due to the lack of phylogeny of the whole family. Nevertheless, it shares with the Mesozoic subfamily Saucrosmylinae the Rs curved and bent anteriorly distally, even in a more pronounced state, i.e. Rs touching R1 in its distal part.  相似文献   

3.
A new genus and species of cyathealean fern, Yavanna chimaerica gen. et sp. nov., is erected for several permineralized stems recovered from the Early Cretaceous (Aptian) Cerro Negro Formation, which crops out at the South Shetland Islands, Antarctica. The new species is characterized by solenostelic erect stems with medullary bundles traversing the pith, and surrounded by persistent petiole bases and adventitious roots. Proximal petiole bases present a one-parted modified omega-shaped trace, which becomes three-parted distally. The anatomy of the new fern show similarities with both Thyrsopteris elegans Kunze and with the Cyatheaceae s.s., suggesting that it is a representative of an extinct lineage among the Cyatheales.  相似文献   

4.
The Yamama Formation is the main Lower Cretaceous (late Berriasian–Valangenian) carbonate reservoir in southern Iraq. Petrographic study from thin-section examination shows that the skeletal grains included calcareous algae from both red and green algae. Red algae is concentrated in the upper part of the Formation, and the most important of this algae species is Permocalculus ssp. Green algae is less common, and its concentration is in the middle part of the Formation. The most species found in the Yamama Formation is dasycladeans, and both small and large species of benthonic foraminifera such as Nautiloculina, Textularia, Trocholina, Pseudocyclammina, and Everticyclammina are also present. The non-skeleton grains included oolites, pellets, and micrite. Six cyclic type microfacies have been recognized for Yamama Formation in Ratawi-3 (Rt-3) and Ratawi-4 (Rt-4) Wells, namely peloidal packstone–grainstone, algal wackestone–packstone, oolitic–peloidal grainstone, bioclastic wackestone–packstone, foraminiferal wackestone, and mudstone microfacies. The latter has been divided into two submicrofacies: argillaceous lime mudstone and fossiliferous lime mudstone. The lateral extension of these microfacies has been identified by integrating the thin-section data and well logs’ character variations with similar characteristic for microfacies. The Yamama Formation was affected by five diagenetic processes, which are micritization, cementation, recrystallization, silicification, and stylolites. The Yamama Formation was deposited during a regressive period within the outer ramp, shoal, and inner ramp setting.  相似文献   

5.
The Late Neoproterozoic Buah Formation (Nafun Group, Oman) is a carbonate unit outcropping in the Jabal Akhdar and Huqf areas. It is composed mostly of shallow‐water carbonates deposited on a distally steepened carbonate ramp. Correlation of two δ13C isotope shifts shows that in the Jabal Akhdar ramp differentiation into fast and slow subsiding areas was followed by lateral progradation. In the Huqf area, however, a uniform scenario of upward shallowing of the facies and lateral progradation is demonstrated by chemostratigraphic timelines cross‐cutting the facies belts. The chemostratigraphic profiles show that the Buah Formation was deposited during sea‐level highstand conditions and that ramp differentiation was due to synsedimentary tectonics. High‐resolution correlation of δ13C profiles from the same lithostratigraphic unit (whether Precambrian or Phanerozoic in age) lacking biostratigraphic data can shed light on carbonate systems dynamics, tectonic vs. eustatic controls on depositional sequences and basin subsidence.  相似文献   

6.
The fossil clam shrimp genus Cratostracus was first described from the Turonian–Coniacian (Upper Cretaceous) Qingshankou Formation in the Jilin and Heilongjiang provinces of China, and it has been found to range down into the Aptian Guantou Formation in Zhejiang Province of southeastern China. Recently, species tentatively attributable to it (Cratostracus? cheni) has been recorded in the well-known Jehol Biota bearing Barremian–lower Aptian (Lower Cretaceous) Yixian Formation in western Liaoning Province of northeastern China. The species described in this paper as Cratostracus? tunisiaensis sp. nov. was recovered from the Sidi Aïch Formation in the Chotts area of southern Tunisia. Although only tentatively attributed to Cratostracus, its occurrence is consistent with a Barremian (Early Cretaceous) age for the formation. This first direct dating of the Sidi Aïch Formation gives a valuable insight for the stratigraphy of the region and will make it possible to more precisely correlate the different outcrops of the Sidi Aïch Formation. Moreover, the new fossil discovery allows a reconstruction of the paralic ecosystem that characterized the study area during the Barremian.  相似文献   

7.
Late Albian ammonite faunas from the Aitamir Formation of the Koppeh Dagh Basin in northeast Iran are described and illustrated. These comprise 14 taxa, several of which are recorded from Iran for the first time, namely Anahoplites planus (formerly recorded from central Iran in open nomenclature only), Semenoviceras solidus, Epihoplites (Metaclavites) iphitus, Hysteroceras orbignyi and Pseudhelicoceras robertianum. New records of Placenticeras grossouvrei extend the stratigraphic range of this species downwards into the Late Albian; previously it was known from the Early and Middle Cenomanian only. The record of the rare E. (M.) iphitus fills a palaeobiogeographic gap between Crimea and Tajikistan, and the holotype of Spath is re-illustrated here. Additionally, Epihoplites trapezoidalis, from the Late Albian of Tajikistan, is relegated into the synonymy of Spath's species. A large number of taxa typical of the Late Albian (upper part of the Gault Clay Formation) of northwest Europe indicate close palaeobiogeographic affinities with the Koppeh Dagh Basin and faunal exchange across the Russian Platform and Transcaspia. The stratigraphic succession of the ammonite faunas is used for a biostratigraphic subdivision of the upper Aitamir Formation.  相似文献   

8.
The Khami group within the petroliferous Zagros Basin of Iran includes the Surmeh, Hith, Fahliyan, Gadvan and Dariyan formations. The Dariyan Formation, previously known as Orbitolina limestone is very signif-icant as a reservoir rock in the Zagros Basin. In this study, the age of the Dariyan Formation is examined based on biostratigraphic and paleontological investigations. 236 m of Dariyan Formation sediments in the sections at Kuh-e Rahmat （north） and Nour-Abad （west） of Iran were selected to study its biostratigraphy. According to the lithostratigraphic investigations, the Dariyan Formation in these sections is subdivided into three： lower, middle and upper, which include thin-bedded to medium-bedded and massive lime-stone. Micropaleontologic study of the Dariyan Formation has led to the recognition of two biozones in the Nour-Abad area and one biozone in the Kuh-e Rahmat stratigraphic column. Diagnostic foraminifera in these sections are as follows： Globigerinel oides algerianus Cushman and Ten Dam, Globigerinelloides fer-reolensis Moullade, Globigerinelloides maridalensis （Bolli）, Globigerinelloides paragottisi Verga and Permoli Silva, Hedbergel a aptiana Bartenstein, Hedbergel a excelsa Longoria, Hedbergel a luterbacheri Longoria, Hedbergella occulta Longoria, Hedbergella ruka （Banner et al.）, Hedbergella similis Longoria, Hedbergella trocoidea （Gandolfi）, Muricohedbergella delrioensis （Carsey）, Pseudoplanomalina cheniourensis Sigal, Con-icorbitolina conica d＇Archiac, Iraqia sp., Mesorbitolina parva Douglass, Mesorbitolina pervia Douglass, Meso-rbitolina ovalis Gorog and Arnaud-Vanneau, Mesorbitolina subconcava Leymerie, Mesorbitolina texana （Roemer）, Mesorbitolina ovalis-pervia Cherchi and Schroeder, Debarina hahounerensis Fourcade et al., Marssonel a trochus （d＇Orbigny）, Nezzazata sp., Orbitolina sp., Textularia sp.  相似文献   

9.
滇西三江地区澜沧江南带广泛发育三叠纪火山岩。在北部云县一带,中晚三叠世火山岩出露齐全,自下而上可划分为中三叠统忙怀组(T2m),上三叠统小定西组(T3x)和上三叠统芒汇河组(T3mh)。忙怀组以酸性火山岩为主,为一套流纹岩夹火山碎屑岩组合;小定西组发育为中基性火山熔岩夹火山碎屑岩;芒汇河组具有流纹质火山碎屑岩与玄武岩共存的"双峰式"火山岩特征。地球化学特征表明,南澜沧江带三叠纪火山岩具有弧火山岩与大陆板内火山岩的双重属性,推测其形成环境为过渡型的大陆边缘造山带环境。对南澜沧江带南部景洪附近采集到的石英安山岩样品进行Ar-Ar年龄测试,得到的坪年龄为236.7±2.2Ma,为中三叠世。结合火山岩年代学结果,推测澜沧江洋主碰撞期为早三叠世,中三叠世与晚三叠世早期分别为碰撞后的应力松弛阶段与洋盆继续俯冲期,到晚三叠世末期,俯冲作用结束,澜沧江洋关闭。  相似文献   

10.
Sedimentary deposits of the Lower Cretaceous Xiagou Formation form the most significant potential hydrocarbon reservoirs in the Qingxi Sag, Jiuquan Basin(NW China). Zircon U-Pb ages of the dated basalts at the top of the Xiagou Formation give an isochron age of 115.6 Ma, and the sedimentation interval of the Xiagou Formation was speculated to range from about 125/124 Ma to 115 Ma based on paleontological research and stratigraphic correlation analysis. Here we use GR logging data as a palaeoenvironmental and palaeoclimatic proxy to conduct a detailed cyclostratigraphic study of five selected wells. Power spectra, evolutionary fast Fourier transformation and wavelet analysis all reveal significant sedimentary cycles in the Xiagou Formation. The ratios of cycle wavelengths in these stratigraphic units are 33.82 m : 7.91 m : 3.06 m : 1.79 m, which is similar to the ratio of orbital targets of 20 : 5 : 2 : 1. The ratio of 20 : 5 : 2 : 1 is interpreted as Milankovitch cycles of 405 kyr long eccentricity,100 kyr short eccentricity, 37 kyr obliquity, and 22 kyr precession cycles respectively. A high-resolution astronomical time scale is constructed by tuning the stratigraphy into target curves of orbital cycles respectively. Based on the astronomical time scale, the absolute ages of 55 samples were estimated,which are used for subsequent stable carbon and oxygen isotope stratigraphy analysis. The analysis results of the five studied wells in the Qingxi Sag indicate:(1) a negative trend of δ~(13)C values upwards in the Xiagou Formation, and(2) negative δ~(18)O values with a positive trend upwards. Both relatively heavy values and pronounced covariances of δ~(13)C values and δ~(18)O values indicate an arid-evaporationcontrolled climate during the sedimentary period of the Lower Cretaceous Xiagou Formation, Qingxi Sag, Jiuquan Basin. Moreover, positive covariances of SQK_1g_(2+3) indicate extremely high temperature, and negative covariances of SQK_1g_1 indicate a relatively low temperature.  相似文献   

11.
《Gondwana Research》2014,25(3):999-1007
Abundant data have been acquired on the lower Cambrian small shelly fossils (SSFs) of the Yangtze platform during the last three decades, demonstrating that these fossils are an important piece of evidence for the Cambrian radiation and are useful biostratigraphic tools for correlating the lower Cambrian. Here we report SSF associations from the Yanjiahe Formation in the Three Gorges area, South China. The Yanjiahe Formation is well exposed near the Yanjiahe village, and its 40-m-thick sequence can be subdivided on the basis of lithology into five stratigraphic intervals (beds). Small shelly fossils occur mainly in Beds 2 and 5, but abundant SSFs were discovered in thin sections of siliceous–phosphatic nodules from Bed 3 for the first time. No skeletal fossils were discovered in the basal siliceous rock interval (Bed 1), but the negative δ13Ccarb excursion and the occurrence of the acritarch Micrhystridium regulare indicate that it belongs to the basal Cambrian. The SSF associations are somewhat similar to those of East Yunnan, and can be differentiated into three biozones (in ascending order): the Anabarites trisulcatus–Protohertzina anabarica assemblage zone (Bed 2), the Purella antiqua assemblage zone (Bed 3), and the Aldanella yanjiaheensis assemblage zone (Bed 5). The occurrence of A. yanjiaheensis in Bed 5 probably indicates that Bed 5 belongs to Cambrian Stage 2, but the Stage 2/Stage 1 boundary is uncertain since Bed 4 lacks fossils. SSF biostratigraphy indicates that the Yanjiahe Formation is pretrilobitic Meishucunian in age (equivalent to the Nemakit–Daldynian to Tommotian of Siberia, Terreneuvian). Five SSF genera occur in Bed 2, more than six genera in Bed 3, and twenty-three genera in Bed 5. The stepwise increase in generic diversity through the Yanjiahe Formation is comparable with the global diversity increase through the Nemakit–Daldynian to early Tommotian interval.  相似文献   

12.
The Bittacidae (hangingflies) were abundant and widespread during the Mesozoic, but much of their diversity falls within the Jurassic whereas in the Cretaceous they are less common. A new bittacid, Burmobittacus jarzembowskii gen. et. sp. nov., is described from mid-Cretaceous amber from northern Myanmar. This new find is the first bittacid from Burmese amber and also the first Mesozoic bittacid preserved in amber. The new genus is distinguished from all known bittacids in having a long and narrow wing with Rs arising from R and forking very early (in the basal one-fourth of the wing), resulting in the stem of Rs being very short (about 1/8th of the length of Rs1+2), and stems of the main branches of Rs (Rs1+2 and Rs3+4) being unusually long.  相似文献   

13.
The taxonomic composition of the palynological assemblage of the Dongning Formation is supplemented. The palynological assemblage corresponds to those from the Lipovtsy Formation (Aptian) in the Razdolnaya Basin of Primorye (Russia) and the Muling Formation (Aptian) in the Jixi Basin of eastern Heilongjiang (China). It is found that the age of the Dongning Formation is Aptian. The palynological assemblage is characterized by dominance of spores of Gleicheniaceae; they are accompanied by spores of Cyatheaceae. The most important feature of the palynological assemblage of the Dongning Formation is the presence of angiosperm pollen (Tricolpites sp., T. micromunus, T. vulgaris, Retitricolpites georgiensis, R. vulgaris, Clavatipollenites hughesii, Quercites sparsus, Fraxiniopollenites variabilis).  相似文献   

14.
Ventnor No. 2 Borehole, located near Ventnor, Isle of Wight, penetrated the basal part of the Chalk Group and the Selborne Group before terminating in the upper part of the Lower Greensand Group (Sandrock Formation). The borehole was examined for Foraminifera, and although they were not seen in the Sandrock Formation and Monks Bay Sandstone Formation, the remainder of the borehole yielded moderately low diversity assemblages dominated by agglutinated species. Foraminiferal zones 3-6 (H dentatus to M. fallax/M. rostratum macrofaunal zones) were identified in the Gault Formation and zones 6 (lower) to 6a (M. fallax/M. rostratum to A. briacensis macrofaunal zones) were identified in the Upper Greensand Formation. Assemblages from the overlying West Melbury Marly Chalk Formation were used to identify foraminiferal zones BGS1-BGS3 (M. mantelli and M. dixoni macrofaunal zones).  相似文献   

15.
The first biozone (Anabarites trisulcatus Assemblage Zone) in the Siberian hypostratotype of the Vendian (northwestern slope of the Olenek Uplift) is represented by the Turkut Formation of the Khorbusuonka Group and most of the Syhargalakh Formation of the Kessyusa Group. The lower part of the Kessyusa Group in some of the sections includes stratiform breccia coeval with the middle part of the Syhargalakh Formation. The breccia is shown to be the alteration product of tuff breccia, which is widely distributed in the region and occurs as diatremes. A U-Pb zircon date of 543.9 ± 0.24 Ma for tuff breccia provides the best constraint on the age of the boundary between the Anabarites trisulcatus and Purella antiqua Assemblage Zones. The first appearance of small skeletal fossils Cambrotubulus decurvatus (which define the base of the Anabarites trisulcatus Assemblage Zone) is 1.4 m above the lower boundary of the Turkut Formation. Ichnofabric in the underlying Khatyspyt Formation is globally distributed in the strata 553-551 million years old, always predating the first appearance of small skeletal fossils of the Anabarites trisulcatus Assemblage Zone. The base of the Anabarites trisulcatus Assemblage Zone is therefore younger than 553-551 Ma, whereas the duration of the assemblage zone does not exceed six million years.  相似文献   

16.
A reexamination of large caenagnathid material from the Upper Cretaceous (Campanian) Dinosaur Park Formation of Alberta, Canada, reveals undescribed material referable to Caenagnathus collinsi. A femur, two astragalocalcanei, two metatarsals, two unguals, and a caudal vertebra provide anatomical information on Caenagnathus collinsi. Estimates of femoral length based on the proportions of other oviraptorids suggest that the non-femoral material represents a taxon intermediate in size between Chirostenotes pergracilis from the Dinosaur Park Formation and Anzu wyliei from the Maastrichtian Hell Creek Formation. The femur is within the range of predictions, and confirms the body size estimates based on the other material. The large size of the material and a number of morphological characters distinguish the material from Chirostenotes pergracilis and suggest that it is referable to Caenagnathus collinsi. The relative diversity of caenagnathids in the Dinosaur Park Formation is likely underestimated.  相似文献   

17.
The coal-bearing sequences of Barakar and Raniganj formations exposed in Bina and Jhingurdah open-cast collieries, respectively, are analysed for their macro- and miofloral content. The sediment successions primarily comprise of sandstones, shales, claystones and coal seams. In addition to the diverse glossopterid assemblage, four palynoassemblage zones, namely Zones I and II in Bina Colliery and Zones III and IV in Jhingurdah Colliery, have also been recorded in the present study. The megafossil assemblage from the Barakar strata of Bina Colliery comprises of three genera, namely Gangamopteris, Glossopteris and cf. Noeggerathiopsis. Palynoassemblage-I is characterised by the dominance of non-striate bisaccate pollen genus Scheuringipollenites and subdominance of striate bisaccate Faunipollenites and infers these strata to be of Early Permian (Artinskian) age (Lower Barakar Formation). The palynoassemblage has also yielded a large number of naked fossil spore tetrads, which is the first record of spore tetrads from any Artinskian strata in the world and has a significant bearing on the climatic conditions. The palynoassemblage-II is characterised with the dominance of Faunipollenites over Scheuringipollenites and is indicative of Kungurian age (Upper Barakar Formation). The megafossil assemblage from the Raniganj Formation of Jhingurdah Colliery comprises of five genera with 26 species representing four orders, viz., Equisetales, Cordaitales, Cycadales and Glossopteridales. The order Glossopteridales is highly diversified with 23 taxa and the genus Glossopteris, with 22 species, dominates the flora. The mioflora of this colliery is represented by two distinct palynoassemblages. The palynoassemblage-III is correlatable with the palynoflora of Early Permian (Artinskian) Lower Barakar Formation. The assemblage suggests the continuity of older biozones into the younger ones. The palynoassemblage-IV equates the beds with composition V: Striatopodocarpites–Faunipollenites–Gondisporites assemblage zone of Tiwari and Tripathi (1992) of Late Permian (Lopingian) Raniganj Formation in Damodar Basin. The FAD’s of Alisporites, Klausipollenites, Falcisporites, Arcuatipollenites pellucidus and Playfordiaspora cancellosa palynotaxa in this assemblage enhance the end Permian level of the Jhingurdah Top seam, as these elements are the key species to mark the transition of Permian into the Lower Triassic.  相似文献   

18.
The present paper records for the first time the bryozoan fragments from 4 m core of the Godhra Formation (early Miocene) and from 4m core and 5 m core of the Chhasra Formation (early middle Miocene) of the Kachchh Offshore Basin, Western India. The Godhra Formation has presence of three bryozoans, viz., ?Crassimarginatella sp., Thalamoporella sp. and Vincularia sp. while the Chhasra Formation has presence of four bryozoans, namely, ?Margaretta sp., Steginoporella sp., ?Thalamoporella sp. and Vincularia sp.  相似文献   

19.
Upper Cretaceous sediments of the Kanguk Formation exposed in Eidsbotn and Viks Fiord grabens on Devon Island, Nunavut, Canadian High Arctic, yielded 91 fossil marine diatom species and varieties (including indeterminate taxa), representing 41 genera. Excellent preservation of the assemblages was aided by shallow burial, protection in downfaulted linear grabens, and the presence of abundant volcanic material. Planktonic species and resting spores comprise nearly 70% of the diatom assemblage, and provided abundant food resources for the Late Cretaceous Arctic ecosystem. Deposition of the approximately 225 m-thick stratigraphic sequence was predominantly in a shallow marine neritic setting, with an upward progression to interbedded terrestrial deposits of the Expedition Fiord Formation, reflecting a regression and eventual persistence of terrestrial facies into the Early Cenozoic. The Kanguk Formation is widespread across the Canadian Arctic, and diatom biostratigraphy indicates a Santonian–Campanian age for the sequences reported herein, based on the presence of Gladius antiquus in the lowermost strata and occurrence of Costopyxis antiqua throughout the succession. However, Amblypyrgus sp. A and Archepyrgus sp. aff. A. melosiroides, encountered in the lower part of the succession, are known exclusively from the Lower Cretaceous. This may suggest a slightly older age. New information on shallow shelf diatom assemblages from this study is compared to reports on two other Late Cretacous Arctic diatom assemblages. These three sites represent an environmental transect from shallow to distal shelf settings and into the oceanic realm.  相似文献   

20.
Abundant and well-preserved assemblages of plant macrofossils occur from the Hojedk Formation at Babhutk, Kerman, Iran. This new locality is the first in the Jurassic of Kerman where the plant material is shown preserved. Eight species of seven genera were identified representing five different gymnosperm groups: Nilssonia cf. undulata, Nilssonia cf. orientalis, Elatides sp., Podozamites sp., and Williamsonia asseretoii and two pteridophyt groups: Equisetites laterale and Coniopteris sp. The collected flora suggests subtropical conditions at the time of deposition of the Hojedk Formation. Based on stratigraphical distributions of the encountered macrofossils, Bajocian–Bathonian age is suggested for the lower and middle unit of the Hojedk Formation. These plant fossils help confirm conclusions from recent geological studies that place the Kerman Basin of Iran during the Jurassic.  相似文献   

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