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1.
Mariusz A. Salamon 《Swiss Journal of Geoscience》2009,102(1):77-88
Valanginian strata in central epicratonic Poland have recently yielded crinoids, not previously recorded from the area. The fauna comprises isocrinids (Balanocrinus subteres, B. gillieroni, “Isocrinus?” lissajouxi), millericrinids (Apiocrinites sp.) and comatulids (Comatulida indet.). For comparison, a few samples of isocrinids from Valanginian strata of Hungary (Tethyan province) were also analysed. The isocrinids, cyrtocrinids and roveacrinids (sensu Rasmussen 1978 inclusive of Saccocoma sp.) were already known from the Valanginian of the southernmost Tethyan regions of Poland (Pieniny Klippen Belt and Tatra Mountains). The current study demonstrates their occurrence in central epicratonic Poland, and suggests that many Jurassic to Cretaceous stalked crinoid taxa (mainly isocrinids) predominated in the shallow-water settings of this area. Thus, the hypothesis of migration (at least from mid-Cretaceous onwards) to deep-water areas, as a response to an increase of the number of predators during the Mesozoic marine revolution, seems not to be universally applicable. 相似文献
2.
腕足类新科Spinochonetidae(fam.nov.)建立在宜昌地区志留系兰多维列统罗惹坪组下段中部(上埃隆阶)的Spinochonetes Rong,Xu et Yang(1974)和Spinolella(gen.nov.)两个属,以及一个属、种未定的分类单元的基础上。新科成员仅有从腹壳喙部伸出一根直的腹喙刺,这与Chonetoidea超科内的Strophochonetidae科以及Chonestrophiidae科众成员的铰合缘刺都是从腹壳铰合缘上伸出来的有着本质差别。另外,本文还对Spinochonetes以及它的属型种S.notata Rong,Xu et Yang(1974)进行重要图解和补充描述。与此同时,对Spinolella(gen.nov),以及S.minuta(gen.et sp.nov.)进行系统描述和对比。据目前所知,新科成员只分布于我国鄂西、黔东北、陕南和川北等地,属于上扬子台地的土族居民。因为Spinochonetidae(fam.nov.)属于腕足类独特的一个类型,演化快,贝体极小,保存精美,因此具有分类学、地层对比,以及恢复古环境等方面的重要意义。 相似文献
3.
Two new genera from the Lower Cretaceous Yixian Formation of Beipiao City, Liaoning Province, northeastern China are described and illustrated. Paracretocateres gen. nov. (type species P. bellus, sp. nov.) and Yixianteres gen. nov. (type species Y. beipiaoensis sp. nov.) are assigned to the subfamily Lophocaterinae based on the state of the procoxae which are not projecting, the transverse procoxal cavities, and the exposed protochantins. The new taxa broaden the diversity of this family and provide further morphological characters for phylogenetic studies of Trogossitidae. They also provide evidence that lophocaterines well-diversified prior to the trogossitines and their biologies may have been similar to extant forms. 相似文献
4.
Walter G. Nelson 《Estuaries and Coasts》1979,2(4):213-217
The polychaete Janua (Dexiospira) brasiliensis (Grube) is shown to exhibit gregarious settling patterns on both natural (Zostera marina) and artificial (aquarium glass) substrates. J. (D.) brasiliensis tends to be found more often on older (=longer) Zostera blades and on the upper (=older) portions of the blades on which it is found, probably as a result of requiring a diatom mat before being able to settle on the Zostera surface. On both Zostera and the aquarium glass, J. (D.) brasiliensis forms small clumps (2 cm) with the animals within the clumps distributed at random. 相似文献
5.
AbstractBiostratigraphical data using larger foraminifera and planktonic foraminifera permitted us to establish the correlation between shallow platform sediments rich in larger foraminifera (Montsec and Serres Marginals thrust sheets) and deeper ones containing planktonic foraminifera (Boixols thrust sheet).Consequently, the Santa Fe limestones containing Ovalveolina-Praealveolinaassemblage represent the Cenomanian. Early Turonian ( ‘IT~ archaeocretacea and P. helvetica zones) exist in both, Montsec and Boixols thrust sheets and it is constituted by Pithonella limestones. Late Turonian (M. schneegansi zone) is only present in Boixols thrust sheet (Reguard Fm.), the Montsec thrust sheet having an erosive hiatus.Late Coniacian-Early Santonian (D. Concavata zone) is represented in the Montsec thrust sheet (Cova Limestones) and in the eastern part of the Boixols thrust sheet (St. Corneli Fm.) by two differents facies giving two different microfaunal assemblages; the firts one, characterized by Ophtalmidiidae s.l indicate a restricted lagoonal environment while the second one, characterized by diverses species of complex agglutinated, Fabulariidae, Meandropsinidae and Rotaliidae, represents an open shallow platform. In the Boixols thrust sheet (Anseroles Fm.) dominate the planktonic foraminifera and small benthic.In the late Santonian (D. asyrnetrica zone) the sea reached as far as Serres Marginales thrust sheet where sediments (Tragó de Noguera unit) are terrigenous and deposited in a very shallow platform. In the Montsec thrust sheet (Montsec marls) the larger foraminifera indicate a platform deeper than that of the Serres Marginals thrust sheet. In the Boixols thrust sheet the sediments are deposited in an outer platform (Herbasavina Fm.) or turbiditic basin (Mascarell Mb.).During Campanian times the transgresion reaches the maximum. In the Serres Marginals sediments are deposited in a restricted shallow environment rich in Meandropsinidae (Serres Limestones). In the Montsec thrust sheet they are deposited in a platform with patch reefs and shoals (Terradets limestones) and in the Boixols one in an outer platform, talus and/or basin.During Early Maastrichtian times (C. falsostuarti zone) terrigenous materials arrived in the basin, the rate of sedimentation increased outstripping the subsidence rate and the retreat of the sea to the north. Late Maastrichtian (C. gansseri zone) is only present in the Boixols thrust sheet. 相似文献
6.
7.
Lopatin A. V. Averianov A. O. Kuzmin I. T. Boitsova E. A. Saburov P. G. Ivantsov S. V. Skutschas P. P. 《Doklady Earth Sciences》2020,494(1):667-669
Doklady Earth Sciences - The first finding of the docodontan (a lower molar of Sibirotherium sp.) from the Bol’shoi Kemchug 3 locality (Ilek Formation, Lower Cretaceous) in Krasnoyarsk... 相似文献
8.
合肥盆地三尖铺组~(40)Ar-~(39)Ar同位素年代地层学研究 总被引：2，自引：0，他引：2
合肥盆地南缘中生代红层层序及时代 ,由于缺乏可靠的化石依据 ,曾几经变动人为因素很大。根据三尖铺组红层中泥岩在沉积或成岩作用条件下形成的伊利石之 40 Ar- 39Ar定年 ,其坪年龄为 15 7.7～ 15 9.5 Ma,等时线年龄为 15 7.2～ 15 9.9Ma,并用 K- Ar法测年进行对比和验证 ,其值为 15 1.8～ 15 5 .8Ma,故确定其时代下限应为中侏罗世晚期 (卡洛维期 ) ,上限可能达晚侏罗世早期 (牛津期 )。40 Ar- 39Ar坪年龄谱还记录了晚侏罗世—早白垩世岩浆活动热事件信息 ,以及三尖铺组红层中陆源碎屑之母岩 (云母片岩及片麻岩等 )形成的冷却史。 相似文献
9.
本文记述的掘足类（Scaphopods）系我国首次报道,化石产自西藏南部聂拉木县古错村北山下白垩统古错Ⅱ组中。计1属2种Dentalium jeffereysi Gardner,D.gucuoensis（sp.nov.）. 相似文献
10.
《International Geology Review》2012,54(9):1089-1101
The Lower Jurassic genus Kalitzkillina with two subgenera K. Kalitzkillina and K. Shirabella, from the Abshir river, Southeast Fergana and the Lower Cretaceous genus Vlakon7iia from the West Tumangan area are described. Regeneration of spines is discussed and illustrated for the first time The following species are described and illustrated: Kalizkillina (K.) sixtelae, K. (K.) repmmanae, K. (Shibirella) striata, K. (S.)tumida and Vlalcomia ustinovskii.--I.G.Sohn. 相似文献
11.
Wang Wenli Institute of Natural History Beijing Natural History Museum Yang Zunyi 《《地质学报》英文版》1993,67(3)
A new insect family Liaoximordellidae (fam. nov.) has been named for a well-preserved specimen which was collected from the Upper Jurassic outcropping west of Daxinfangzi Village, Lingyuan County, Liaoning Province. The specimen can not be put into Mordellidae or Praemordellidae because it possesses some original and intermediate characters in morphology. It serves the study of mordellid evolution. Besides, the fossil group associated with the insect is important for the stratigraphic division of the Mesozoic in western Liaoning. 相似文献
12.
《International Geology Review》2012,54(2):168-170
In the Minusinsk (Siberia) intermontane downwarp, the Devonian-Carboniferous boundary lies within the regional paleomagnetic horizon. This boundary's perfect correlation with the same boundary in the Russian platform (4000 km away) is taken as evidence of the widespread occurrence of the inversely magnetized Upper Fammenian zone, of a certain isochronism between the Devonian-Carboniferous boundaries in Minusinsk and in the northwest of the Russian platform (notwithstanding their tectonic differences, etc.) and of possibilities of such correlations on a worldwide scale.--V.P. Sokoloff. 相似文献
13.
A new species of cladid(?) crinoid, Segmentocolumnus (col.) clarksoni, based on distinctive, disarticulated stem material, is described from the Upper Llandovery Kilbride Formation. Hitherto, this unit has yielded two taxa based on single, nearly complete crinoids. In contrast, S. (col.) clarksoni is known from numerous specimens, including common long pentagonal, pentameric, heteromorphic pluricolumnals with symplectial articulations, broad pentagonal lumina and narrow claustra. A related morphospecies is known from the Ashgill (Upper Ordovician) of Ireland. The fossil echinoderms of the Llandovery (Lower Silurian) are poorly known globally. Where present in this interval, echinoderms are more commonly preserved as disarticulated ossicles and rarely as complete specimens. Complete crinoids have now been identified from nine horizons in the Llandovery of the British Isles, making this one of the better known pelmatozoan faunas from this time interval. However, only two of these occurrences have yielded as many as five or more identifiable taxa. Seven of the nine occurrences are Upper Llandovery (Telychian). Genera are typical of the Silurian or (Upper Ordovician + Silurian); the only remnant Ashgill taxon that did not survive the Llandovery was the morphogenus Segmentocolumnus (col.) Donovan, an ‘extinction’ that probably owes more to taxonomic method than any evolutionary pattern. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
14.
E. V. Bugdaeva V. S. Markevich E. B. Volynets 《Stratigraphy and Geological Correlation》2014,22(3):256-268
The plant remains and palynological assemblages are studied in detail in the section of the coal-bearing upper part of the Aptian Starosuchan Formation near the village of Molchanovka (Partizansk Basin, South Primorye region). On the basis of the light and electron microscopic study of the disperse cuticles, it was established that the coals are mostly composed of remains of taxodialean Elatides asiatica (Yok.) Krassil., subordinate Miroviaceae, rare ginkgoalean Pseudotorellia sp., and bennettite Nilssoniopteris rithidorachis (Krysht.) Krassil. The spores Gleicheniidites and pollen Taxodiaceaepollenites are dominant in the palynospectrum of the coal interlayer. It was found that dominant taxodialeans and gleicheniaceous ferns with less abundant Miroviaceae, ginkgoaleans, and rare bennettites occurred in the Aptian swamp communities of the Partizansk basin. Shoots and leaves of Elatides asiatica, fronds of Birisia onychioides (Vassil. et K.-M.) Samyl., are dominant in the burials of plants from the clastic rocks. The fragments of leaves of Nilssoniopteris, scale-leaved conifers, and Ginkgo ex gr. adiantoides are rare. The disperse cuticle of these layers mostly includes Pseudotorellia sp.; however, its remains in burials were not found. The spores Laevigatosporites are dominant in the palynospectra from the clastic interlayers. Ginkgocycadophytus and taxa close to Pinaceae are plentiful among the pollen of gymnosperms. 相似文献
15.
The mechanism of Au dispersion in sediments of mountainous desert environments has been studied in two different areas of the Chilean Andes. The San Pedro de Cachiyuyo placer (ca. 1800 m a.s.l.) consists of alluvial fans and ephemeral stream sediments deposited in a stable piedmont. The primary Au source is Cu–Au-bearing hydrothermal tourmaline breccia. The relief of this area is low (1850 m) and the average annual rainfall is ca. 20 mm. The La Coipa area (ca. 4000 m a.s.l.) is characterized by a rugged relief. The annual average rainfall is ca. 100 mm. The sedimentary deposits are less sorted than in San Pedro de Cachiyuyo and consist of ephemeral stream alluvium and slope deposits formed in a periglacial environment. The primary Au sources are two volcanic-hosted epithermal precious metal deposits. At San Pedro de Cachiyuyo, the halo is less than 1 km in length and the highest Au concentration are observed at the break in slope between the hillside and the piedmont. In the La Coipa area, Au was only detected by chemical analysis in the 125–63 μm and <63 μm fraction; however, the dispersion halo extends for over 10 km from the source. In both cases the geochemical signal of gold was strongest in the fraction <63 μm. 相似文献
16.
Summary Major, trace element and isotopic (Sr, Nd, Pb) data are reported for representative samples of interplinian (Protohistoric,
Ancient Historic and Medieval Formations) activity of Mt. Somma-Vesuvius volcano during the last 3500 years. Tephra and lavas
exhibit significant major, trace element and isotopic variations. Integration of these data with those obtained by previous
studies on the older Somma suites and on the latest activity, allows to better trace a complete petrological and geochemical
evolution of the Mt. Somma-Vesuvius magmatism. Three main groups of rocks are recognized. A first group is older than 12.000 yrs,
and includes effusive-explosive activity of Mt. Somma. The second group (8000–2700 yrs B.P.) includes the products emitted
by the Ottaviano (8000 yrs. B.P.) and Avellino (3550 yrs B.P.) plinian eruptions and the interplinian activity associated
with the Protohistoric Formation. Ancient Historic Formation (79–472 A.D.), Medieval Formation (472–1139 A.D.) and Recent
interplinian activity (1631–1944 A.D.) belong to the third group of activity (79–1944 A.D.). The three groups of rocks display
distinct positive trends of alkalis vs. silica, which become increasingly steeper with age. In the first group there is an
increase in silica and alkalis with time, whereas an opposite tendency is observed in the two younger groups.
Systematic variations are also evident among the incompatible (Pb, Zr, Hf, Ta, Th, U, Nb, Rb, Cs, Ba) and compatible elements
(Sr, Co, Cr). REE document variable degrees of fractionation, with recent activity displaying higher La/Yb ratios than Medieval
and Ancient Historic products with the same degree of evolution. N-MORB normalized multi-element diagrams for interplinian
rocks show enrichment in Rb, Th, Nb, Zr and Sm (> *10 N-MORB).
Sr isotope ratios are variable, with Protohistoric rocks displaying 87Sr/86Sr = 0.70711–0.70810, Ancient Historic 87Sr/86Sr = 0.70665–0.70729, and Medieval 87Sr/86Sr = 0.70685–0.70803. Neodymium isotopic compositions in the interplinian rocks show a tendency to become slightly more radiogenic
with age, from the Protohistoric (143Nd/144Nd = 0.51240–0.51247) to Ancient Historic (143Nd/144Nd = 0.51245–0.51251). Medieval interplinian activity (143Nd/144Nd: 0.51250–0.51241) lacks meaningful internal trends. All the interplinian rocks have virtually homogeneous compositions
of 207Pb/204Pb and 208Pb/204Pb in acid-leached residues (207Pb/204Pb ∼15.633 to 15.687, 208Pb/204Pb ∼38.947 to 39.181). Values of 206Pb/204Pb are very distinctive, however, and discriminate among the three interplinian cycles of activity (Protohistoric: 18.929–18.971,
Ancient Historic: 19.018–19.088, Medieval: 18.964–19.053).
Compositional trends of major, trace element and isotopic compositions clearly demonstrate strong temporal variations of the
magma types feeding the Somma-Vesuvius activity. These different trends are unlikely to be related only to low pressure evolutionary
processes, and reveal variations of parental melt composition.
Geochemical data suggest a three component mixing scheme for the interplinian activity. These involve HIMU-type and DMM-type
mantle and Calabrian-type lower crust. Interaction between these components has taken place in the source; however, additional
quantitative constraints must be acquired in order to better discriminate between magma characteristics inherited from the
sources and those acquired during shallow level evolution.
Received May 5, 2000; revised version accepted June 19, 2001 相似文献
17.
Multistage Growth of a Rare-Element, Volatile-Rich Microgranite at Argemela (Portugal) 总被引：4，自引：1，他引：4
The small Argemela microgranite body in central Portugal displaysmany of the mineralogical and chemical features characteristicof peraluminous, Li, P-rich, rare-element pegmatites. Its mineralogyconsists predominantly of quartz, albite, white mica (partlyreplaced by lepidolite) and a phosphate of the amblygonite series.K-feldspar is noticeably absent or scarce. Cassiterite, beryland columbite are the main accessories. The microgranite showsextreme enrichment in incompatible elements such as F, P, Rb,Cs, Li, Sn and Be, and extreme depletion in Sr, Ba, Zr and REE.It is highly sodic and strongly peraluminous. The micrograniteoverall is interpreted as a mixture of two components: a crystalmush injected from below (seen in narrow dykes intersected duringdrilling, composed of quartz, albite and phengite) and interpretedas ‘feeders’, overprinted by a second highly evolvedcomponent dominated by Li, F, P (Rb, Cs, Be, Sn, Nb, Ta, etc.)considered as a ‘lubricant’ medium for the ascendingmush and occasionally quenched (quartz, albite, skeletal lepidoliteand amblygonite). This second component has the mineralogicaland chemical characteristics of rare-element pegmatites. Allthese petrological characteristics are magmatic. Only a fewnarrow cross-cutting veinlets with quartz, K-feld-spar and F-pooramblygonite are considered as fluid derived. A model of crystallizationin successive steps is proposed where concentration in fluxingagents (F, Li, P, etc.) is progressively enhanced up to saturationwith the crystallization of magmatic lepidolite and amblygonite. KEY WORDS: petrogenesis; microgranite; pegmatite; volatiles; Portugal
*Corresponding author. 相似文献
18.
Geochemical and carbonate petrographical methods were coordinated in facies investigations and environmental reevaluations, related to the Hauptdolomit (Hd.) = main doimite formation (±Norian) of the Northern Calcareous Alps.It is practical to distinguish eight, environmentally controlled, facies units (1–8) and three geochemical groups (I–III). Superimposed upon the environment pattern (tidal complex, lagoonal complex, barrier bar and shoal complex) is a predictable (geochemical) dolomitization and non-carbonate distribution.The vertical and lateral facies associations, their waxing and waning in the geologic columns, allow paleogeographic reconstructions. Especially important are clayey, ±bituminous facies, commonly known as “Seefeld facies”, which are interpreted to be of mainly intertidal to very shallow near-shore, rather than of deep-water, origin. Threefold stratigraphy can be substantiated and is found to be practicable for the Hd. formation in a large part of the Northern Calcareous Alps.In an attempt to explain some of the phenomena associated with dolomitization in the Hd. formation, a model of anaerobic dolomitization has been considered, outlining steps of early diagenetic dolomitization. 相似文献
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20.
Stephen K. Donovan David A. T. Harper Zhan Renbin Lars Stemmerik Liu Jianbo Svend Stouge 《Geological Journal》2012,47(6):653-660
A collection of numerous crinoid pluricolumnals from the uppermost Darriwilian (Middle Ordovician) of Tibet were derived from one biological species of crinoid. The specimens were collected from well‐lithified, bioclastic shelf limestones of the upper part of the Lower Chiatsun Group, Pygodus serra Biozone; coeval rocks of similar lithology outcrop at the summit of Everest. A new crinoid morphospecies, Segmentocolumnus (col.) hanshessi, is tentatively considered a ‘stem‐group cladid’, perhaps a dendrocrinid. The proxistele is broad and pentagonal in section with a broad, pentagonal axial canal; the mesistele of similar gross morphology is more slender with a regularly heteromorphic column and a similarly wide axial canal; the dististele is a terminal dendritic radice with a pentastellate axial canal. In the mesistele, the meric sutures correspond to the centres of the sides of the column, but in the dististele they occur in the angles. This range of morphologies would have led to their inclusion in at least two morphogenera if they had not been closely associated; as they belong to a single biological species, they have been ‘lumped’ together herein. This is a rare contribution to our knowledge of the early crinoids from a region outside Europe and North America. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献