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1.
An extensive study of the ammonoid fauna occurring in the lagoonal facies of a Middle Triassic isolated carbonate platform (Latemar platform, Dolomites, Italy) has been undertaken, and ammonoids from selected coeval successions (Punta Zonia, Marmolada, Rio Sacuz) have been illustrated. Ammonoids from Latemar have been collected in 20 distinct horizons (storm deposits) within the ca. 500 m thick lagoonal succession of the platform, thus providing a biostratigraphy of a series which is unusually expanded for this time interval, close to the Anisian-Ladinian boundary. Contrary to general opinion, some ammonoids of the Latemar and other coeval carbonate platforms of the Dolomites (Marmolada, Cernera), in particular Aplococeras avisianum, Lecanites misanii, Celtites spp., and Paranevadites sp., are also present in nearby basinal series. The same taxa have been found in North American localities deposited at the opposite margin of Panthalassa. The homotaxis of these ammonoids in North America and Latemar allow to establish a global scale correlation between the Southern Alps and North America with the highest resolution to date possible. In the context of this study, Aplococeras transiens n. sp. and Esinoceras nerinae n. sp are established. 相似文献
2.
EVELYN KUSTATSCHER MICHAEL WACHTLER JOHANNA H. A. VAN KONIJNENBURG‐VAN CITTERT 《Palaeontology》2010,53(3):595-626
Abstract: Generally, lycophytes are not well represented in Anisian floras. Nonetheless, four different genera, each with one species, have been distinguished in the Anisian flora from Kühwiesenkopf (Monte Prà della Vacca), Italy. They were well preserved and yielded leaf cuticles in all four taxa and in situ spores in two of them. Lycopia dezanchei gen. et sp. nov. is the most common form; it is characterized by a dichotomising creeping prostrate rhizome (representing the primary shoot axis) from which arise aerial axes, apically bifurcated and covered with bundles of long leaves. This taxon cannot be attributed to any of the lycophyte orders, but most resembles Lycopodiales. Two representatives of the Isoetales have been found, of which Isoetites brandneri sp. nov. is abundant. This species is characterized by a short stem, which is unusual for this genus. In situ immature microspores and megaspores were found in some specimens. Lepacyclotes bechstaedtii sp. nov. has a quadrilobe corm with fertile scales inserted in whorls or slightly helicoidally. Short sterile leaves arise distally from the corm in some specimens. Selaginellales are very rare in the flora; Selaginellites leonardii sp. nov. is represented by a strobilus that yielded both micro‐ and megaspores. Some sterile fragments have been found associated, but never in organic connection. 相似文献
3.
This paper gives an account of distribution of Dasycladales in ammonoid-bearing Middle Triassic carbonate platforms of the
Dolomites. A ca. 600-m-thick section was investigated within the Latemar platform interior and Dasycladales from correlated
ammonoid-bearing samples of the Marmolada platform were studied for comparison. At Latemar, the dense sampling allowed, with
some confidence, the identification of the first occurrences of Diplopora nodosa and Gyroporella ladinica, and the last occurrences of D. annulatissima and D. comelicana. Their stratigraphic range was found to be in agreement with literature. Other first or last occurrences could not be reconciled
with known distributions, and were considered as environmentally or palaeogeographically controlled. All four algal events
occur within a narrow interval of two Illyrian (Upper Anisian) ammonoid subzones (avisianum and crassus subzones). This study demonstrates the biostratigraphic potential of Dasycladales in platform settings, and highlights the
necessity of detailed stratigraphic studies to determine their distribution. 相似文献
4.
Prof. Dr. Franco Russo Dr. Adelaide Mastandrea Dr. Marco Stefani Prof. Dr. Claudio Neri 《Facies》2000,42(1):211-226
Summary This article deals with the discussion of the role of the syndepositional cementation for the growth of the Middle Triassic
pre-volcanic carbonate platforms of the Dolomites (Southern Alps, Northern Italy). The study is concentrated on the Marmolada
Buildup, which escaped the facies destroying dolomitization which affected many surrounding platforms. The investigations
took place within an almost isochronous uppermost Anisian palcogeographic transect, ranging from the platform-top to the margin
and the upper slope. Methods used include geological mapping, sedimentological and paleontological studies, evaluation of
the microfacies, as well as SEM and EDS epifluorescence analyses.
The well bedded platform-top succession consists of intra-bioclast calcarenites and calcirudites, interbedded with subordinate
boundstones, and organized in shallowing upward, meter scale depositional cycles, sometimes capped by subaerial surfaces.
The platform margin belt is rich in boundstones and lacks a primary framework formed by organisms; metazoan skeletons form
less then 5% of the rock volume. The outer margin and the uppermost slope are characterized by decimeter-scale boundstone
blocks, coated and linked to each other by huge amounts of radiaxial fibrous calcite cements, arranged in concentric crusts.
These cements (“evinospongiac”) represent the main component of the margin and upper slope facies.
Epifluorescence analyses suggest the existence of abundant organic residual matter associated not only with the bioclasts
and peloids, but also with the syndepositional cements. Organic matter likely played a significant role in carbonate cementation
and was a key factor for the early lithification of the platform as well as for the sediment production. Minor element microanalyses
reveal an uniform Mg content in different calcite types (2–4 Mole % MgCO3), independently from the primary nature of the components. Late diagenetic sparry calcites exhibit similar Mg values but
no iron. These data point to a homogenization of minor element distribution, probably associated with a slow but long-lasting
semi-closed fluid circulation, possibly related with the Neogene uplifting of the Dolomite Mountains. 相似文献
5.
Summary The Triassic platforms of the Dolomite Alps of northern Italy are famous for their well-preserved platform flanks. We report
on the discovery of extensive automicrite on these platform slopes. Automicrite stands for autochthonous micritic carbonate,
formed by in-situ precipitation that was mediated by organisms. The automicrite occurs on the 400 m high, 25°–35° dipping
slopes of the Sella platform that were pervasively dolomitized. Textures include peloidal aggregates (thrombolitic microfabric),
irregular spar-filled cavities as well as biodetritus and are in many samples clearly visible despite the dolomitization.
The peloids may occur as loose particles floating in lighter-colored cement or form a loosely connected framework. The preservation
of automicrite textures along with the nearly unaltered slope geometry of the platform lead to several conclusions on the
development of automicrite on such steep and high platform slopes.
相似文献
1) | Automicrite formed patches and layers from the platform top down to over 200 m on the flank and constitutes about 25% of the volume of slope sediment. |
2) | Automicrite alternates with layers of skeletal and lithoclastic rubble and sand. |
3) | Despite the extensive occurrence of automicrite, no mud mounds developed on the steep slopes. The autochthonous carbonate only forms layers and cushions that do not significantly alter the planar clinoforms. |
4) | On the slope, layers of automicrite slid, became fragmented and turned into breccias that dominate the lower slope. The undolomitized, distal ends of these breccias contain the Cipit boulders extensively described in the past. |
6.
Anisian (middle triassic) buildups of the Northern Dolomites (Italy): The recovery of reef communities after the permian/triassic crisis 总被引:1,自引:0,他引:1
Dr. Baba Senowbari-Daryan Dipl. Geol. Rainer Zühlke Prof. Dr. Thilo Bechstädt Prof. Dr. Erik Flügel 《Facies》1993,28(1):181-256
Summary After the end-Permian crisis and a global ‘reef gap’ in the early Triassic, reefs appeared again during the early Middle Triassic.
Records of Anisian reefs are rare in the Tethys as well as in non-Tethyan regions. Most Anisian reefs are known from the western
part of the Tethys but there are only very few studies focused on biota, facies types and the paleogeographical situation
of these reefs. From the eastern part of the Tethys, Anisian reefs, reefal buildups or potential reef-building organisms have
been reported from different regions of southern China. Most of the Anisian reefs known from western and central Europe as
well as from southern China seem to be of middle and late Pelsonian age.
The study area is situated in the northern Dolomites (South Tyrol, Italy) southeast of Bruneck (Brunico). It comprises the
area between Olang (Valdaora) and Prags (Braies). The study is based on detailed investigations of the regional geology, stratigraphy
and lithofacies (R. Zühlke, T. Bechst?dt) as well as on a comprehensive inventory of Anisian reef organisms (B. Senowbari-Daryan,
E. Flügel). These data are used in the discussion of the controls on the recovery of reefs during the early Middle Triassic.
Most late Anisian reef carbonates studied are represented by allochthonous talus reef blocks of cubicmeter size. Small biostromal
autochthonous mounds are extremely rare (Piz da Peres). The reef mounds as well as most of the reef blocks occur within the
middle to late Pelsonian Recoaro Formation. They were formed on the middle reaches of carbonate ramps in subtidal depths,
slightly above the storm wave base with only moderate water energy. Most lithotypes observed in the reef blocks correspond
to sponge and/or algal bafflestones. Low-growing sessile organisms (Olangocoelia (sponge, alga?), sphinctozoan sponges, bryozoans, soleno-poracean algae, corals) and encrusting epibionts (sponges, porostromate
algae, cyanophycean crusts, foraminifera, worms, microproblematica) created low cm-sized biogenic structures (bioconstructions)
which baffled and bound sediment. Organic framework was only of minor importance; it is restricted to theOlangocoelia lithotype. Framework porosity was small in these reef mounds. Submarine carbonate cements, therefore, are only of minor importance
s compared with Permian or Ladinian reefs. The relatively high number of lithotypes encountered in the reef blocks indicates
a high biofacies diversity.
Regarding the relative frequency, the diverse biota consist in descending order ofOlangocoelia, sponges (sphinctozoans, inozoans, siliceous sponges), bryozoans, porostromate algae and worm tubes. The sphinctozoans are
characterized by small, mostly incrusting forms. The numerical diversity (species richness) is low compared with late Permian
or Ladinian and late Triassic sphinctozoan faunas occurring within reefs.
Following the sponges, monospecific bryozoans (Reptonoditrypa cautica
Sch?fer & Fois) are the most common organisms in the reef limestones. Porostromate algae were restricted to areas within the bioconstructions
not inhabited by sponges. The low-diverse corals had no importance in the construction of an organic framework.
Surprisingly, microbial crusts are rare or even lacking in the investigated Anisian bioconstructions. This is in contrast
to late Permian and Ladinian as well as Carnian reefs which are characterized by the abundance of specific organic crusts.
The same comes true for‘Tubiphytes’ which is a common constituent in Permian, Ladinian and Carnian reef carbonates but is very rare in the Anisian of the Olang
Dolomites. Instead of‘Tubiphytes’ different kinds of worm tubes (spirorbid tubes, Mg-calcitic tubes and agglutinated tubes) were of importance as epifaunal
elements. Macrobial encrustations consisting of characteristic successions of sponges, bryozoans, algae, worm tubes and microproblematica
seem to be of greater quantitative importance than in Ladinian reefs.
Destruction of organic skeletons (predominantly of bryozoans) by macroborers (cirripedia?) is a common feature.
The Anisian reef organisms are distinctly different from late Permian and from most Ladinian reef-builders. No Permian Lazarus
taxa have been found.
New taxa: Sphinctozoan sponges—Celyphia? minima n.sp.,Thaumastocoelia dolomitica n. sp.,Deningeria tenuireticulata n. sp.,Deningeria crassireticulata n. sp.,Anisothalamia minima n.g. n.sp., Inozoan sponges-Meandrostia triassica n.sp. Microproblematica-Anisocellula fecunda n.g. n.sp., Porostromate alga-Brandneria dolomitica n.g. n.sp.
Most of our data are in agreement with the model described byFois & Gaetani (1984) for the recovery of reef-building communities during the Ansian but the biotic diversity seems to be considerably
higher than previously assumed.
Anisian deposition and the formation of the reef mounds within the Pelsonian Recoaro Formation of the Dolomites were controlled
by the combined effects of synsedimentary tectonics and eustatic changes in sea-level. During several time intervals, especially
the early Anisian (northern and western Dolomites: tectonic uplift), the early Pelsonian (eastern Dolomites: drowning) and
the late Illyrian (wide parts of the Dolomites: uplift and drowning), the sedimentation was predominantly controlled by regionally
different tectonic subsidence rates. The amount of terrigenous clastic input associated with synsedimentary tectonics (tectonic
uplift of hinterlands) had a major influence on carbonate deposition and reef development. The re-appearance of reef environments
in the Olang Dolomites was controlled by a combination of regional and global factors (paleogeographic situation: development
of carbonate ramps; decreasing subsidence of horst blocks; reduced terrigenous input; moderate rise in sea-level). 相似文献
7.
The Mesozoic sedimentary cover belonging to the Monte Carmo-Rialto unit of the Ligurian Briançonnais domain is composed of Scythian clastics and Anisian to Carnian carbonate rocks over 300 m thick. This paper focuses on the stratigraphy of this carbonate complex, its environmental significance, and its evolution in light of dynamic stratigraphy. Our facies analysis of limestones and dolomites of the Triassic complex allowed us to reconstruct an environmental model. Data support a distally steepened carbonate ramp of Anisian age evolving to a more diversified Ladinian platform with an oolitic sand-bar belt separating the lagoon from the slope. The Monte Carmo-Rialto slope facies are the only witnesses of deep sedimentation in the Triassic terrains of the Ligurian Briançonnais domain, otherwise represented by shallow-water carbonate deposits. On the basis of facies succession, we have identified nine medium-scale cycles (third-order sequences) in the study area, comparable to those evidenced in the Briançonnais s.s. domain by the French authors. Small-scale cycles analysis evidenced mainly shallowing-upward trends in the examined sequences; although a few evidences of transgression-related deposits (deepening upward cycles) have been found at the base three sequences, they have been mostly obliterated by dolomitization and masked by local tectonics. For this reason, we can undoubtedly distinguish only the part of each sequence belonging to HST, while the TST, though present, still remains a partition that cannot be precisely characterized. In the same way, LSTs are not present in the Monte Carmo-Rialto unit, due to the original relative landward position of the examined area. Sequence stratigraphy analysis indicates different long-term dynamics for the two evolutionary stages of the Triassic Ligurian platform: a general landward backstepping to moderate progradation during the Early Anisian and true progradation during the latest Anisian and Ladinian. In addition, a good fit with the sequences proposed by the SEPM chart has been found, indicating a correspondence for the third-order sequences of the Middle Triassic. 相似文献
8.
Patteera Ketmuangmoon Anisong Chitnarin Marie-Béatrice Forel Prachya Tepnarong 《Revue de Micropaléontologie》2018,61(1):3-22
The Pha Kan Formation that crops out at the Phra That Muang Kham section, south of Lampang city, was measured and sampled for ostracod analysis. We here report the occurrence of 29 species distributed among 14 genera. Four new species are described: Triassocypris phakanella Forel nov. sp., Leviella lampangensis Forel nov. sp., Bektasia yawella Forel nov. sp. and Hungarella poli Chitnarin nov. sp. The present data represent the first detailed report of Middle Triassic (Anisian) ostracods from the Sukhothai terrane and the first insight into diversity dynamics following the end-Permian extinction in this area. The ostracod assemblages of the Phra That Muang Kham section are discussed and document an important shift from siliciclastic to carbonate conditions, from a protected to an open marine environment, followed by a slight regressive trend up-section associated with repeated salinity fluctuations. This fauna illustrates the post-crisis recovery during the Middle Triassic and some hypothesis are issued on the distribution pathways of several taxa. 相似文献
9.
Summary Sedimentological, paleontological and sequence analyses of Cenomanian limestones in Sicily reveal the facies architecture
and dynamics of a Mid Cretaceous rudistdominated platform margin from Western Tethys. The studied deposits outcrop near Palermo,
as part of a large structural unit of the Sicilian Maghrebids. They belong to the Panormide carbonate platform, a Mesocenozoic
paleogeographic domain of the African margin.
The lateral continuity of the beds along three nearly parallel E-W outcrop sections allowed the recording of cm/dm thick lithological
and faunal variations. Nine main lithofacies associations have been recognised along about 200 m of subvertical strata. Their
vertical and lateral organisation points to a transition from highenergy shelf-margin rudist patches and shoals to more internal
lagoonal-tidal environments over a short distance.
The lithofacies evolution and stacking pattern along the three sections made it possible to define elementary cycles, composite
cycles and larger-scale sequences with a dominant shallowing-upward trend. Their hierarchical organisation implies that sea-level
fluctuations were an important factor in their formation.
The cycles are characterised by a great variation in facies as a result of transgressive-regressive events in different sectors
of the inferred Cenomanian shelf. Subtidal cycles typical of the shelf margin (4–10 m-thick) are particularly well identifiable.
They are made of large Caprinidae and Sauvagesiac rudstone-to-floatstone (about 2/3 of the total thickness), capped by rudist-conglomerates,
often organised into 3–5 fining-upward amalgamated beds and showing, in places, effects of surface-related diagenesis. In
more internal shelf areas the cycles consist of Caprinidae-Radiolitidae floastone grading up into amalgamated beds of angular
bioclastic rudstone/grainstone. Alternations of foraminifer/ostracod mudstone/wackestone and bioclastic grainstone/fine-rudstone,
capped by loferites and/or by other emersion-related overprintings, characterise the cycles formed in the peritidal zones.
these cycles are stacked into three incomplete depositional sequences. The sequence boundaries have been identified by the
abrupt interposition of peritidal cycles in subtidal rudist-rich cycles, with evidence of brief subaerial exposure. 相似文献
10.
Prof.Dr. Franco Russo Dr. Claudio Neri Dr. Adelaide Mastandrea Dr. Alberto Baracca 《Facies》1997,36(1):25-36
Summary The sedimentological features and the microbiofacies of the Cassian platforms (Late Ladinian-Carnian) of the Dolomites can
be studied only on the basis of the socalled “Cipit boulders”, that are platform-derived olistoliths and clasts fed to the
basin and escaped to the extensive dolomitization affecting the buildups.
Our paper deals with the Cipit boulders occurring in the Punta Grohmann section (Wengen and S. Cassiano formations, Late Ladinian,
Archelaus and Regoledanus Zones). The dominant microfacies are represented by boundstone, consisting of nearly 60% of micritic
limestone occurring both as peloidal or aphanitic micrite, mostly organized into stromatolitic laminites of thrombolites.
The skeletal organism (Tubiphytes, skeletal cyanobacteria, sphinctozoan sponges, etc.) represent only a minor component of the rock (usually less than 10%).
Early cements are widespread and consist both of fan-shaped calcite (replacing former aragonite), bladed isopachous magnesian
calcite and radial-fibrous calcite (neomorphic after Mg-calcite). The carbonate platforms from which the olistoliths derive
were made up mainly of carbonate mud that underwent early lithification, as witnessed by the considerable amount of early
cements: therefore they may be regarded to as mudmounds, and more precisely as microbial mud-mounds, due to the clearly accretionary,
organic-controlled nature of most micrites. The micrites, subdivided into auto- and allomicrite on the basis of micromorphological
and fabric characteristics, have been tested for epifluorescence. The results confirm the organic control on the deposition
of automicrite, also in the cases in which a microbial influence is not obvious (i.e. aphanitic micrite without internal organization). 相似文献
11.
Jobst Wendt 《Palaeontology》2018,61(4):575-595
The first tunicates with a calcareous exoskeleton are reported from Late Triassic buildup‐slope deposits of the Dolomites. Although examples of this group have been known since the early 1900s from the middle–upper Permian of eastern Asia and Sicily as Khmeria, they were erroneously attributed to rugose corals. These early representatives are small, double‐valved, conical skeletons, which evolved into multi‐plated capsules with up to 35 opercula. The latter are joined along zigzag margins, which in life could probably be opened for the atrial and branchial siphons. The construction and shape of these skeletons distinguish them from plants or other invertebrate phyla, while they share several similarities with living tunicates, specifically to sessile ascidians. Apart from a soft‐bodied genus from the lower Cambrian of China, ascidians are known only from isolated spicules, which occur sporadically from the Lower Jurassic onwards. The calcareous skeleton of these Late Triassic tunicates consists of aragonitic fibres, which form spherulitic or clinogonal microstructures. It seems that the stellate aragonitic spicules of Jurassic to Recent ascidians are a vestige of Permian–Triassic ancestors, which after the Carnian lost the ability to construct compound solid skeletons but partly still retain a soft double‐valved or multi‐operculate cellulose‐like tunic. The following taxa are described as new: Order Khmeriamorpha with the genera Khmeria Mansuy and Zardinisoma gen. nov., and the following species: Khmeria stolonifera (late Permian), Khmeria minima (Late Triassic), Zardinisoma japonicum (late Permian), Z. cassianum, Z. pyriforme, Z. polyplacophorum and Z. pauciplacophorum (all Late Triassic). 相似文献
12.
A new Middle Triassic ichnofauna recovered nearby the town of Tisens (Bozen) in the Adige Valley (Trentino, Northern Italy) is described. A relatively large ichnoassociation, in which various ichnogenera can be recognized, comes from the basal inter-supratidal layers of a mixed carbonate siliciclastic unit of Pelsonian (Middle Anisian) age. Most of the isolated footprints and trackways pertain to lizard-like reptiles referable to Rhyncosauroides and, subordinately, to archosaurian reptiles. In particular, the ichnogenera Rotodactylus, Synaptichnium and Chirotherium have been recognized. Many tracks are at present unidentified; among them a lizard-like morphotype (morphotype A). The site also yelded numerous fossil plant horizons and some scattered vertebrate remains referable to Placodontidae (cf. Placodus gigas). The site shows the continuity in the Pelsonian of the “chirothere ichnofauna” and the dominance of Rhynchosauroides in carbonate, tidal flat environments. 相似文献
13.
Summary East of Seefeld/Tyrol the Hauptdolomit facies (Triassic, Norian) is accompanied by an organic-rich intercalation, the Seefeld
facies. Three facies were distinguished, which developed within a separate basin within the Hauptdolomit carbonate platform.
These facies have been investigated in an environmental and palaeoecological context applying microfacies analysis, palynology,
organic petrology, organic geochemistry and stable isotope geochemistry. As the controlling factors of sedimentation, sea
level changes are suggested for large scale fluctuations, and climatic changes for variations on a smaller scale. Within the
basin facies a μm-scaled rhythm can be observed, which was obviously seasonally controlled. Amajor amount of organic material
of the deposit has been produced by microbial activity under anoxic conditions. Causes for the absence of pollen and spores
in many black shale deposits are discussed. 相似文献
14.
Summary In the castern Anti-Atlas (SE Morocco), a small sedimentary basin (Mader Basin) evolved during the late Palacozoic. The Middle
Devonian deposits consist of shales and limestones with a thickness up to 700 m in the depocentre. Sedimentary structures
and sole marks of Middle Devonian limestones indicate transport from the northwest and the south towards the basin centre,
located in the central Mader area. Lithostratigraphic, biostratigraphic, and dynamic stratigraphic approaches were applied
to correlate stratigraphic sections. Five correlatable large-scale base-level hemicycles were recognized in the Middle Devonian
succession. Thickness trends of Middle Devonian deposits, regional correlations, and facies-trends reveal the geometry of
a carbonate ramp. The carbonate ramp was slightly inclined (<1°) to the NE. A sedimentary wedge, consisting of limestones
and limestone/marl alternations, was deposited during the Eifelian and marks the transition from the ramp to the adjacent
basin. Middle Devonian water depths are estimated as close to and within the storm wave-base at the southern area of the ramp
and far below storm wave-base in the northeastern part of the ramp. Shallowest conditions (inner-ramp environment), close
or within the fairweather wave-base, existed during the early Givetian as documented by the abundance of recfal fauna (stromatoporoids,
corals) and calcimicrobes (lumps, micritic envelopes) in the eastern and southeastern area of the ramp. 相似文献
15.
Frank Stiller 《Palaeontology》2001,44(3):529-551
Echinoid remains from the Triassic of China are described for the first time. The Middle Triassic of Qingyan in Guizhou Province, south-western China, has yielded nine taxa of primary spines; seven of these come from the lower Upper Anisian. Because all of the spines are disarticulated, the material is treated only parataxonomically. 'Cidaris' lineola (Bather) and 'Cidaris' wissmanni (Desor) are species originally described from the alpine Triassic of Europe. 'Cidaris' bangtoupoensis sp. nov., 'Cidaris' wachangpoensis sp. nov., 'Cidaris' venustespinosa sp. nov., 'Cidaris' fangchui sp. nov., 'Cidaris' gu sp. nov., 'Cidaris' mafengpoensis sp. nov. and 'Cidaris' sp. A are so far known only from Qingyan. Palaeoautecological interpretations based on the shapes of the spines fit well with the fact that the echinoids from Qingyan are part of highly diverse fossil associations which represent the remains of communities that lived in a protected, shallow-marine, stable soft-bottom habitat. The rather high diversity of the echinoid spines in terms of the number of both taxa and general types of shape shows that the echinoids, after nearly becoming extinct at the end of the Palaeozoic, began a new phase of adaptive radiation in the Anisian at the latest. 相似文献
16.
FRANK STILLER 《Palaeontology》2011,54(6):1415-1433
Abstract: The isocrinid sea lily Tyrolecrinus wugangi sp. nov. from uppermost middle to lowermost upper Anisian (lower Middle Triassic) strata of Leidapo near Qingyan, Guizhou Province, south‐west China, provides new data on the early phylogeny of the order Isocrinida. The new species is the earliest unequivocal representative of the family Isocrinidae. It predates all other known species of the genus Tyrolecrinus that come from upper Ladinian to Rhaetian strata and also all other known taxa of the Isocrinidae. Nevertheless, its stem is of fully developed isocrinid type and is characteristic of the genus, with consistently synostosial, rarely cryptosymplectial, distal nodal articular facets. These findings indicate that the Isocrinidae evolved prior to the late middle Anisian in the far‐eastern part of the Palaeotethys ocean, perhaps in the region forming today’s south‐west China, and spread to various other regions later in the Middle and Late Triassic. The genus Tyrolecrinus is revised and the new genus Bakonycrinus gen. nov. is erected. 相似文献
17.
Assoc. Prof. Dr. Ioan I. Bucur Dr. Carol Strutinski Dipl. Geol. Dana Pop-Stratila 《Facies》1994,30(1):85-100
Summary The Sasca zone situated in the innermost part of the Getic Domain from the South Carpathians comprises mainly Triassic deposits
of Scythian-Anisian (?Ladinian) age that can be ascribed to four different members forming the Sasca Formation. Three of the
members consist of carbonate deposits. Their study permitted a brief characterization of the main microfacies types, and especially
in the Valea Susara Limestone Member the identification of a relatively rich association of foraminifers and calcareous algae.
The assemblage withMeandrospira dinarica, Pilammina densa, Oligoporella pilosa andPoncetella hexaster identified in these limestones indicates a Middle Anisian age (Pelsonian-Lowermost Illyrian). Difficulties arise in differentiating
between the forms belonging to theOligoporella-Physoporella group for which a taxonomic revision is necessary. The morphologic characteristics of the three varieties ofDiplopora subtilis allow a splitting into different species.Teutloporella peniculiformis
Ott, 1963 is regarded as anomen nudum. 相似文献
18.
粪化石是重要的遗迹化石,其内含物信息可为讨论生物行为、生理、相互关系、古环境等提供重要证据,进而对恢复和重建地质历史时期的生态系统等有重要意义。本文首次报道了贵州省兴义市泥麦古剖面中三叠世拉丁期兴义动物群化石层第35自然层的7种不同形态的粪化石。通过观察粪化石的内含物情况,发现其主要由贵州龙骨骼和鱼鳞组成,极少含有无脊椎动物碎片,表明粪化石来源于非壳食性的肉食性动物。依据粪化石的尺寸、缺少螺旋结构及相对较小的内含物碎片等信息,排除动物源是无脊椎动物、大型肉食性鱼类及大型鱼龙类的可能。结合兴义动物群下部化石组合海生爬行类实体化石的信息,进一步推断所研究粪化石的动物源应为非鱼龙的海生爬行动物,很可能是幻龙类、鸥龙类或海龙类。本文报道的7种形态的粪化石显示该下部化石层中的海生爬行动物之间至少存在1级营养等级的差异,这为恢复和重建中三叠世拉丁期海洋生态系统提供了重要依据。另外微生物的参与及泥质含量较高的厌氧环境使得该层的粪化石保存完好。 相似文献
19.
The rhodolithic slope deposits of a Burdigalian carbonate platform in Sardinia near Sedini were analyzed to reconstruct facies
and palaeobathymetry. There is a distinct red-algal growth zonation along the platform slope. The clinoform rollover area
consists of coralline-algal bindstones, which downslope change into a zone where rhodoliths are locally fused by progressive
encrustation. Mid-slope rhodoliths are moderately branched, and downslope rhodoliths have fruticose protuberances, resulting
in branching rhodolith growth patterns. There is a sharp change from the rhodolitic rudstones to the basinal, bivalve-dominated
rudstones at the clinoform bottomsets. Red-algal genera identified include Sporolithon, Lithophyllum, Spongites, Hydrolithon, Mesophyllum, Lithoporella, Neogoniolithon, and other mastophoroids and melobesioids. Genera and subfamilies show a zonation along the clinoforms, allowing palaeobathymetric
estimates. The clinoform rollovers formed at a water depth of around 40 m and the bottomsets around 60 m. Results from geometrical
reconstruction show that coral reefs in the inner platform formed at water depths of around 20 m. Therefore, the Sedini carbonate
platform is an example of a reef-bearing platform in which the edge or the platform-interior reefs do not build up to sea
level. 相似文献