共查询到20条相似文献,搜索用时 0 毫秒
1.
Petrography and biosedimentology of the Rosso Ammonitico Veronese (middle-upper Jurassic, north-eastern Italy) 总被引:1,自引:1,他引:0
Alain Préat Salvatore Morano Jean-Paul Loreau Christophe Durlet Bernard Mamet 《Facies》2006,52(2):265-278
A petrographic and biosedimentological study of the Rosso Ammonitico Veronese from the Trento Plateau (north-eastern Italy) shows that diagenetic (neomorphism, recrystallization) and biological processes (microbial content and pigmentation) influenced the formation and alteration of the carbonate matrix. The subject of this article is the interaction of early diagenetic processes and an attempt to explain the different colors of the matrix (red, pink, grey). Nearly 200 samples derived from 14 sections (Callovian to Tithonian) located in the Verona area have been studied by means of classical, cathodoluminescence and SEM microscopy. Calcite and ferruginous microfilaments of different shapes and sizes are present and tentatively attributed to fungi and iron bacteria. These micro-organisms precipitated iron oxy-hydroxides at poorly dysoxic-anoxic sediment–water interfaces. Further liberation of submicronic hydroxides (now hematite) was responsible for the red pigmentation of the carbonate matrices, originally composed of less than 1 μm-sized micrite. Controversial smaller nanograins (0.1–0.5 μm) attributed to nanobacteria or planktonic picoeukaryotes have been observed in the reddish samples. Recrystallization of the micrite leads to the formation of new micritic crystals, between 2 and 4 μm in size, then to microspar crystals. Micritic textures are linked to the different colours of the samples. The intensity of the red colour is correlated with the presence of hematite (former iron hydroxides) and the presence of planar subhedral micritic grains. In contrast, pink and greyish samples are linked to the increasingly coalescent structure of anhedral micritic and microsparitic crystals. 相似文献
2.
The fossil record of metriorhynchids and plesiosaurians from the Rosso Ammonitico Veronese Formation (RAVFm, Middle–Upper Jurassic, Italy) is represented by elements collected between the eighteenth and twentieth centuries. All the metriorhynchid material is referred to the genus Neptunidraco. The first RAVFm plesiosaurian material was collected in the nineteenth century and referred to Plesiosaurus: elements are here described and interpreted as a chimerical association of crocodylomorph and plesiosaurian bones, providing the first co-occurrence of these clades in the RAVFm. The second plesiosaurian is the associated skeleton that we refer to Anguanax zignoi gen. et sp. nov. Bayesian phylogenetic analysis confirms the basal geosaurine affinities of Neptunidraco resulted by parsimony analysis. Using both methods, Anguanax was recovered as a basal pliosaurid, sister group of the clade including Marmornectes and Thalassophonea. Bayesian inference methods indicate that both Italian lineages diverged from other known lineages between 176 and 171 Mya, also showing divergence rates significantly higher than any other representative of their respective clades. We suggest a phase of rapid evolutionary adaptation to deeper marine environments in the ancestors of the Rosso Ammonitico Veronese reptiles as a response to the latest Liassic regressive regime in Northern Tethys. 相似文献
3.
Jurassic neptunian dikes are common within Upper Triassic to Lower Jurassic platform limestone of the Julian Alps. At Mt Mangart,
the following geometries were observed: irregular dissolution cavities, thin penetrative fractures, larger fractures with
sharp sidewalls, and laterally confined breccia bodies. Inside a complex neptunian dike system two main generations of infillings
were differentiated. The first generation is heterogeneous and consists of bioclastic limestones, representing uniquely preserved
sediments subdivided into five different microfacies. The second generation is more common and typically consists of coarse-grained
breccias with host-rock clasts and marly limestone matrix containing echinoderms. Fracture formation and void filling of the
first generation of neptunian dikes is dated as Pliensbachian and is interpreted to be caused by the Julian carbonate platform
dissection due to widely recognized Lower Jurassic Tethyan rifting. The timing of formation for the second generation is only
broadly constrained, ranging from the Pliensbachian to the Late Cretaceous. 相似文献
4.
Summary An integrated study of the early Messinian reef complex cropping out along the eastern coast of the Salento Peninsula (southern
Italy), including stratigraphy, facies analysis and paleoecological aspects, is here presented. Fourteen facies types belonging
to three main facies associations (back reef and shelf, shelf-edge, slope) have been recognized. They document a wide spectrum
of depositional environments, reef building organisms and growth fabrics, in response to depth and other environmental factors
in different parts of the reef complex.
The biotic structure of the reef is also described and discussed in detail. It consists of different types of reef building
organisms and of their bioconstructions (mainlyPorites coral reefs,Halimeda bioherms and vermetidmicrobial “trottoirs”), that differ in composition and structure according to their position on the
shelf edge-toslope profile.
Results indicate that the reef complex of the Salento Peninsula has strong similarities with the typical early Messinian reefs
of the Mediterranean region. However, the recognition of some peculiar features, i.e. the remarkable occurrence ofHalimeda bioherms and of vermetid-microbial “trottoirs”, gives new insights for better understanding reef patterns and development
of the reef belt during the Late Miocene in the Mediterranean. 相似文献
5.
Summary The Bombaso Formation and basal Meledis Formation in the central Carnic Alps near Straniger Alm and Zollnersee (Austria/Italy)
unconformably overlie the folded Variscan basement and consist of shallow marine clastic and carbonate sediments which are
arranged to form two fining and deepening upward sequences. Particularly limestones and even breccias of the Bombaso Formation
yielded a rich fusulinid fauna composed of 34 species which are attributed to the following zones:Quasifusulinoides quasifusulinoides-Protriticites ovatus; Protriticites pseudomontiparus, andMontiparus montiparus.
Breccias of the Bombaso Formation west of Straniger Alm contain the oldest fusulinid fauna of the Carnic Alps, belonging to
theQuasifusulinoides quasifusulinoides —Protriticites ovatus zone. The fauna is composed ofQuasifusulinoides quasifusulinoides, Q. fallax, Q. intermedius, Protriticites cf.ovoides, andPr. ovatus. This assemblage is most similar to that of the Peskovskaya Formation of the Myachkovian Horizon in the Moscow Basin indicating
uppermost Moscovian age. Limestones from depositional sequence 1 at Zollnersee also contain fusulinids of the uppermost Moscovian
which are characterized by a more diverse assemblage:Schubertella donetzica, Fusiella lancetiformis, Beedeina ulitinensis, B. consobrina, B. nytvica, B. siviniensis, Quasifusulinoides
pakhrensis, Q. fallax, Q. kljasmicus, Q. quasifusulinoides, Fusulinella rara, andProtriticites ovatus. Limestones and calcareous sandstones-siltstones of the basal Meledis Formation of depositional sequence 2 near Zollnersee
and at Cima Val di Puartis are characterized by fusulinids of theProtriticites pseudomontiparus zone (Protriticites globulus, Pr. pseudomontiparus, Pr. sphaericus, Pr. rotundatus, Pr. ovoides, Pr. lamellosus, andPraeobsoletes burkemensis) and byMontiparus paramontiparus zone (Praeobsoletes pauper, P. burkemensis, Obsoletes timanicus, O. obsoletes, Montiparus paramontiparus, M. umbonoplicatus, M.
montiparus, M. likharevi, M. rhombiformis andM. priscus) indicating lower to middle Kasimovian age (Krevyakinskian and Khamovnicheskian Horizons of the Russian Platform).
In memoriam FranzKahler (1900–1995) 相似文献
6.
Summary The coastline of the Salento Peninsula (Apulia region, Southern Italy) is characterized by a rocky shore with spectacular
cliffs where the investigated fringing reef complex, the so called Castro Limestone, spectacularly outcrops for at least 40
km.
As reconstructed from several measured sections, the Castro Limestone, which is Middle Chattian in age from our own data,
disconformably mantles a tectonically deformed falaise of Cretaceous-Eocene rocks and is overlain by a remarkable erosional
surface characterized by a very peculiar rhodolite rudstone. The Castro Limestone unit can be considered as a classic unconformity
bounded depositional sequence representing, most probably, a shelf margin prograding complex, related to the major Middle
Oligocene sea level lowstand.
Stratigraphic and sedimentologic features, together with paleontological characters, allow recognition of a virtually complete
range of reef environments across the reef profile.
Several geomorphic zones and associated facies are described, from the most landward reef area (‘back reef’) across the reef
flat and reef from downward to the fore reef slope, contributing to a better knowledge of the evolution of Oligocene reefs
and reef communities in Italy and in the Mediterranean area. 相似文献
7.
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
8.
New paleontological data on Sestrosphaera liasina (Pia) based on material collected in the type-locality, Malga Mandrielle (Italian Southern Alps) are supplied. All the features of the alga are reexamined; the occurrence in the stalk region of an unusual primary lateral inner swelling is confirmed. The structure formed by the inner enlarged portion of the laterals is here indicated as inner pseudocortex. A new diagnosis of S. liasina is proposed and a lectotype is chosen from Pia's material. Finally, a paleontological reconstruction is supplied taking into account all the main biometrical values. 相似文献
9.
Summary The Sikhor Formation (new) is a predominantly siliciclastic sediment package intercalated between the marly-silty Baghamshah
Formation (below) and the calcareous Esfandiar Limestone and Qal'eh Dokhtar Limestone formations (above). All stratigraphic
evidence points to an Early Callovian age of the formation. The Sikhor Formation is restricted to the southern and central
Shotori Mountains and consists of two members: The Kuh-e-Neygu Member (new) is composed of fluvialdeltaic conglomerates, sandstones,
and siltstones grading into marly silt of the Baghamshah Formation. The overlying Majd Member (new) is characterised by mixed
siliciclastic-carbonate sediments that record the interfingering of carbonate ramp sediments with fluvialdeltaic sands and
silts. Evidence of erosional truncation of the underlying Baghamshah Formation and confinement of the siliciclastic sediment
to a comparatively narrow, NNW-SSE elongated strip suggest that the formation had its origin in the asymmetric uplift of a
westdipping tilted fault block in the southern Shotori Mountains that shed its sediment predominantly in a northern and eastern
direction. After erosional levelling, the former uplifted areas were overgrown by the highly productive Esfandiar Carbonate
Platform. The Sikhor Formation thus is evidence of an extensional tectonic pulse in the early Callovian and underlines that
this area of the Tabas Block was a tectonically highly unstable area during most of the Jurassic. 相似文献
10.
Dr. Davide Bassi 《Facies》1998,39(1):179-201
Summary The Calcare di Nago is a carbonate unit of Middle-Late Eocene (Bartonian and Priabonian) age which is well exposed at the
north-eastern end of Lake Garda, on the western margin of the Lessini Shelf (Southern Alps). This unit is highly fossiliferous
as far as the coralline red algae and large foraminifera are concerned. Corals, bryozoans, echinoderms, and molluscs are also
present. The present study deals with the relationships among the coralline taxa, the coralline growth-forms, and their facies
development in the Priabonian part of the type section of the Calcare di Nago. The taxonomic investigation led to the identification
of 15 coralline red algal species belonging to 7 non-geniculate and 2 geniculate genera. One species of Peyssonneliacean (red
alga) and one of Halimedacean (green alga) were also recognized. The quantitative and qualitative analyses based on coralline
red algae and large foraminifera enabled five facies to be distinguished: Algal crust-branch rudstone, Algal/Discocyclina packstone, Coralalgal boundstone, Rhodolith mound wacke/packstone, and Rhodolith pavement. According to the coralline assemblages,
coralline growth-forms, and large foraminiferal associations, the five facies reflect solid and soft substrate types. Some
of these facies are dominated byin situ rhodoliths, others by reworked algal debris. In the architecture of an interpreted prograding carbonate ramp, shallow water
facies are dominated by members of the subfamily Mastophoroideae, while deeper water facies are dominated by those of the
subfamily Melobesioideae and family Sporolithaceae. There is a significant increase both in size and in constructional voids
of the rhodoliths with depth. A concomitant decrease in algal species diversity with depth has been also recognized. LargeDiscocyclina assemblages are localized across the inner and mid ramp boundary.Pellatispira andBiplanispira are present only in the uppermost mid-ramp.Nummulites, Assilina, andSpiroclypeus are dominant together with small orthophragminids both in the mid- and uppermost outer ramp facies. 相似文献
11.
Quaternary carbonate-lithic talus slope successions of the Eastern Alps record an overall correlation between prevalent sedimentary
facies, depositional geometry, and geomorphic maturity of the slope. After exposure of high cliffs by deglaciation or rocksliding,
a low-dipping immature talus dominated by unsorted rockfalls initially accumulates. With progressive talus buildup, slope
segments of different dips develop. Concomitantly, prevalent depositional processes change to grain flows and sorted rockfalls
in the proximal, steep-dipping (35°–30°) slope segment, while deposits of cohesive debris-flows, ephemeral fluid flows and
larger rockfalls prevail in the distal, lower-dipping slope segment. In mature talus deposystems, the proximal slope succession
overlies the lower-dipping package of the distal slope along a thin ‘downlap interval’. Immediately after cliff exposure by
deglaciation or rocksliding, talus may aggrade at rates of up to a few tens of meters per 1,000 years, but the accumulation
rate slows strongly with progressive maturity of slopes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
12.
Summary The fusulinacean faunal content of the Bombaso Fm. and lower part of the Auernig Group (Carnic Alps, Austria/Italy) is reviewed
and completed by data on conodonts and algae. Four different faunal associations can be distinguished within this stratigraphic
interval.
The beginning of the postvariscan sedimentation in the investigated sections is diachronous, shifting in age from early Kasimovian
(Krevyakinian) at Zollner Lake and Mt. Auernig, early to middle Kasimovian at Cima Val di Puartis to late Kasimovian (Dorogomilovian)
at Mt. Ro?kofel.
The sections analyzed consist of shallow-marine sediments, which differ in microfacies of limestones and partly in biotic
assemblages. They are geographically isolated and could not be traced laterally for lithologic correlation in the field.
The biostratigraphic correlation with the faunas of the stratotype sections in the Moscow Basin is hindered by the searceness
of fusulinaceans in the critical levels, especially in the lowermost Kasimovian, and differences in the species composition.
A biostratigraphic correlation of the Bombaso Fm. and basal part of the Auernig Group with the Peski Fm. (Myachkovian) of
the Moscow Basin, as suggested byDavydov & Krainer (1999), is not confirmed by our results. Due to our taxonomic reinterpretation of the oldest fauna (Protriticites aff.permirus with distinct mural pores and largeBeedeina (Pseudotriticites) asiaticus) a lowermost Kasimovian (Lower Krevyakinian) age is more probable. This correlation is supported by the co-occurring conodont
fauna, which is suggested to belong to the zone of “Streptognathodus subexcelsus”. This biozone reaches from the topmost Peski Fm. to the Suvorovo Fm. (Lower Krevyakinian) in the Moscow Basin, and may be
correlated with the uppermost Desmoinesian of the Midcontinent North America.
Fusulinaceans and conodonts of the overlying strata at Zollner Lake and from the sections at Cima Val di Puartis and Mt. Auernig
most probably correspond to the upper Krevyakinian/lowermost Khamovnikian of the Russian platform (Lower Missourian of the
Midcontinent North America). The algal associations (Dvinella, Beresella, Herakella) from these lowermost strata are unique for the Carnic Alps. Their stratigraphic range points to Moscovian-Kasimovian as
well, and fits with the fusulinacean and conodont data.
Sediments of the N?lbling Group (=“untere kalkreiche Schichtgruppe”) have their correlative levels in the upper Khamovnikian,
but reach higher into the Dorogomilovian. More reliable correlations are possible with the fusulinacean faunas of the Cantabrian
Mts. and Central Asia, based on the coincidence of several species. A revised biostratigraphic correlation with the different
remote basins of the Paleotethyan realm and the Russian Platform is given, based on own data and recent results by the members
of the SCCS Working group to define a GSSP close to the Moscovian/Kasimovian boundary.
The sequence-stratigraphic scheme, the systematics, and the biostratigraphic correlation ofDavydov & Krainer (1999) are discussed. 相似文献
13.
《Geobios》2020
Bouleiceras is a very rare genus among the rich assemblages of ammonoids from the lower Toarcian of the Iberian Range. So far, only two dozen specimens have been recorded in numerous field campaigns carried out since 1965 by different authors. The interest of this taxon lies in its peculiar paleogeographical distribution in comparison with most other ammonoids of the same age. A review of these specimens is carried out, including those obtained in previous works and others recently collected in selected localities. Based mainly on the differences in the shape of the ventral section and the suture line, seven species have been identified; two of which are new: Bouleiceras ibericum nov. sp. and Bouleiceras? betetensis nov. sp. All the reviewed specimens are recorded in the Semicelatum Subzone of the Tenuicostatum Zone and the Elegantulum Subzone of the Serpentinum Zone from the Central Sector and the Levantine Sector of the Iberian Range. The global distribution of the genus is summarized from the known data, and its possible dispersal routes are analyzed, as well as the factors that could have conditioned them. 相似文献
14.
Dr. Thomas C. Brachert 《Facies》1992,27(1):191-216
Summary The Late Jurassic epicontinental sea of South Germany protruded far to the North forming a wide bay which was rimmed by shallow-water
platforms (Swiss and French Jura). This wide shelf is characterized by extensive downslope mud accumulations including siliceous
sponge buildups. The bioherms are aligned along the more pericontinental parts of this shelf, which graded to the South into
the Helvetic Basin of the Tethys Ocean.
Five sedimentary cycles of Oxfordian to Middle Kimmeridgian age (ox. 2–ox. 3, ki.1.–ki.1.2, ki.3, ki.1.3–ki.2.1, ki. 2.1–ki.
2.2) were used for interregional correlation. Each cycle is characterized by a vertical suite from marl to pure limestone.
The bases of the marls are characterized by abundant open-marine fossils, glauconite and phosphate (fish teeth and pellets)
and interpreted as condensed sections. Deepening is indicated by bioherms changing their growth form before demise from large
structures into small isolated buildups, which commonly occur within deeper water.
Sequence boundaries, are present at the transition from marl into limestone. Two phases (middle ki. 1.3 and ki. 1/2) of debris-flow
deposition, one accompanied by the sudden spreadout of biostromes and basinward shift of bioherms, are interpreted as lowstand
phases associated with sequence boundaries. The remaining sedimentary cycles described here lack such lowstand deposits. Instead,
corresponding positions in the cycles are characterized by omission features. This problem is still unresolved. It may either
be due to sediment trapping on the ramp or to a changing origin of the cycles compared. It is proposed here that highstand
sediments, having higher contents of fine-grained siliciclastics than lowstand deposits, formed during a humid and warm climate
with high rates of continued runoff and sediment transport. Lowstand deposits consist of pure offbank carbonates, because
the associated drier climate reduced fluvial input of terrigenous material. Corresponding patterns of climatic change are
also seen in platform sediments from the Swiss Jura Range; however, climatic cycles correlate with eustatic sea level fluctuations
in only about 50% of the cases. This misfit may partially result from problems with biostratigraphic correlation (boreal—
Tethyan). Small-scale sedimentary cycles with an average duration of 66’000 years (Mutabilis chron, ki. 2) to 95’000 years (Planula chron, ox. 3) provide a tool for detailed stratigraphic correlation in biostromes, small scale lenticular bioherms (1–2 m
thickness) and large bedded bioherms (many tens of metres thickness). Interruptions of bioherm growth are due to temporal
oxygen deficiency related to plankton blooms. The bathymetrically deepest bioherms-small and lenticular in shape—therefore
suffered the highest number of ecological break-downs, whereas massive bioherms continuously remained above the critical level. 相似文献
15.
Dr. Jacek Matyszkiewicz 《Facies》1996,34(1):23-40
Summary In the top section of the Upper Jurassic profile in the S part of the Cracow-Wielun upland there occur deposits with numerous
fragments of the plantonic crinoidsSaccocoma. Sedimentary structures indicate that these deposits are calciturbidites with domination of the redeposited pelagic material.
TheSaccocoma-calciturbidites rest on the slope beds of Oxfordian cyanobacterial-sponge carbonate buildups formed in the Polish epicontinental
basin, bordering the Tethys ocean in the north. The occurrence of the planktonicSaccocoma seems to be connected with a short deepening the S part of the Polish epicontinental basin in the Late Jurassic. This deepening
caused the change within biocoenoses thriving in carbonate buildups and was mainly expressed in reducingTubiphytes. ‘Tubiphytes-reefs’, representing the last stage in the development of the carbonate buildups in the S part of the Cracow-Wielun upland,
marked the most shallow sedimentation environment. With deepending of the basin,Tubiphytes and other benthonic forms disappeared, and, simultaneously, the dominant fauna became planktonic. The abundance of planktonic
crinoidsSaccocoma (=Lombardia), as well as the presence of planktonic foraminifers, nannoplankton cf.Schizosphaerella, coccoliths and radiolarians indicates a pelagic, open-sea depositional environment.
TheSaccocoma-dominated sediments, which had been primarily deposited from a suspension on a sea floor with a distinct relief, became subsequently
transported by turbidity currents. A limited extent and thickness of theSaccocoma-calciturbidites was caused by a relatively small amount of the primary material which could be transferred by the turbidity
currents because the period of pelagic sedimentation was short. TheSaccocoma-calciturbidites indicate a distinct shift in conditions of sedimentation resulting from over-regional changes and, despite
the lack of index fossils, seem to represent a local lithostratigraphic horizon. These sediments probably mark a sedimentation
event which caused a minor levelling of the sea floor relief. Then, after a sedimentation break, wide-spread destruction of
the tops of carbonate buildups and formation of debris flows in the shallowing Late Jurassic sea took place.
TheSaccocoma-calciturbidites in the S part of the Cracow-Wielun upland can be found near edges of horsts. This suggests that the foundations
of these horsts are probably of sedimentary origin, dating back at least to the Late Jurassic. TheSaccocoma-calciturbidites in the S part of the Polish epicontinental basin seem to result from local, synsedimentary tectonic movements,
which probably reflect over-regional events on the one hand, and oscillations of the sea level-on the other. 相似文献
16.
Summary The marine Paleogene of the Tremp Basin in the Central Southern Pyrenees corresponds to four depositional sequences which
are related to global eustatic third order cycles (Tejas A 2.3–2.6). Associated transgressive and downlap surfaces coincide
with boundaries of biozones. Lowstand systems tracts consist of estuarine and braid delta systems. Transgressive and highstand
systems tracts are composed of carbonate banks and reefs.
Slow thrust-induced changes of the basin topography conditioned the basic type and the areal distribution of carbonate highstand
and clastic lowstand systems. Rapid relative sea level changes controlled the activity and internal dynamic of the depositional
systems. E-W directed blind thrust anticlines are covered during highstand periods by carbonate fringing banks withNummulites bars. N-S orientation of thrust anticlines leads to the evolution of reef-dominated barrier banks and shelf lagoonal homoclinal
ramps. On-bank transport of carbonate sands dominates during transgressions, off-bank transport during highstand periods.
Continuous thrusting during the Ilerdian caused angular unconformities only in combination with relative sea level fall. Sequence-internal
onlap configurations result from contemporaneous tectonic tilting. Fourth order carbonate bank margin cycles contain well
developed lowstand tracts due to increased subsidence rates. Fourth order flooding surfaces are marked by paleosoil horizons
at their landward continuation. 相似文献
17.
Microencrusters and microtaphonomic features of the Oxfordian spongiolithic limestones of the External Prebetic were studied
using thin-section analysis. The spongiolithic limestone is a bioclastic-rich packstone with common echinoderm, mollusc and
brachiopod remains. The bioclasts show a high fragmentation index and frequent microborings. The encrustation index (E
i) is higher for fragments of serpulids, ammonoids and bivalves, and increases with the initial grain-size of bioclasts. The
main microencrusters consist of benthic microbial communities (BMC) and nubeculariids, as well as subordinate calcareous and
siliceous agglutinated foraminifera, serpulids and bryozoans. BMC are usually the first colonizers, and encrusting foraminifera
mainly appear on bioclasts larger than 2 mm. BMC dominate in well-developed encrustations on upward facing surfaces of larger
bioclasts that are also colonized by foraminifera (nubeculariids and Subdelloidina). Bullopora, serpulids and bryozoans are more common on lower surfaces. The fact that the values of encrustation index, encrustation
thickness and diversity of the microencrusters increase with the size of bioclasts is related to a higher stability and exposure
time of the available bioclastic substrate. The microencruster distribution on upper and lower surfaces of large bioclasts
may be related to photic control, space competition and/or predation avoidance. 相似文献
18.
Dasycladales from the Upper Maastrichtian of Salento Peninsula (Puglia, southern Italy) 总被引:1,自引:0,他引:1
Dr. Mariano Parente 《Facies》1997,36(1):91-122
Summary A rich dasycladalean assemblage, mainly consisting of new taxa, has been discovered in upper Maastrichtian coarse bioclastic
limestones of shelf margin facies cropping out along the southeastern coast of Salento peninsula (Puglia, Southern Italy).
It consists of 8 species grouped into 6 genera:Cymopolia decastroi
Parente 1994;C. barattoloi
Parente, 1994;Zittelina fluegeli n.sp;Jodotella koradae (Dieni, Massari & Radoicic, 1983) nov. comb.;Barattoloporella salentina n. gen. n. sp.;Morelletpora dienii n. sp.;Neomeris spp. (two different species).
Zittelina fluegeli n. sp. is characterized by an ovoid thallus with calcification made by a calcareous wall enveloping only the proximal part
of the branches (except in basal whorls) and by closely packed, and partly coalescent, calcified ampullae arranged all around
the median and distal portion of branches.
The transferral ofNeomeris (Larvaria) koradae
Dieni, Massari & Radoicic, 1983 into the genusJodotella, with the new combinationJodotella koradae, is proposed on the basis of new observations on the number and arrangement of fertile ampullae.
The new genusBarattoloporella, type-speciesBarattoloporella salentina n. gen. n. sp., is erected for dasycladalean algae characterized by a segmented thallus. Each segment consists of: a) basal
and apical sterile whorls made by primary branches only, b) central fertile whorls made by primary branches bearing in terminal
position one fertile ampulla and one or two secondary branches.
morelletpora dienii n. sp. is characterized by a segmented thallus with barrel shaped to pear shaped repetitive elements, consisting of simple
whorls of first order branches only. Shape of the branches varies from regularly phloiophorous to more or less differentiated
in a stalk and a swollen portion, with or without a subterminal constriction.
This is by far the most diverse dasycladalean assemblage ever found in the Maastrichtian. Its diversity supports the conclusion
that, within the Late Cretaceous, the Maastrichtian represents a maximum in dasycladalean diversity. Its taxonomic composition
strenghtens the hypothesis that dasycladaleans were hardly affected by K/T mass extinction. 相似文献
19.
In Late Jurassic times, the Swiss Jura carbonate platform occupied the transition between the Paris Basin and the Tethys and
thus connects the Boreal and Tethyan realm. Up to now, the lack of index fossils in the Reuchenette Formation prevented a
reliable correlation between both areas (its sediments are characterised by a prominent sparseness of index fossils). Now,
seven recently in situ collected species of ammonites helped to establish a new sequence-stratigraphical frame for the platform
sediments of the Reuchenette Formation in NW Switzerland. Based on biostratigraphical data, five third-order sedimentary sequences
were assigned to the Late Oxfordian to Late Kimmeridgian. The upper three third-order sequences correspond to the Boreal sequences
Kim3–5 of Hardenbol et al. (1998). The deduced large-scale sea-level fluctuations match those from other European regions (Spain, Russia). This biostratigraphically
based sequence-stratigraphical frame is a prerequisite to refine correlations within a wider area covering the Swiss Jura
and parts of adjacent France and Germany.
Electronic Supplementary Material Supplementary material is available for this article at 相似文献
20.
A characteristic microfacies of the Late Jurassic to Early Cretaceous allodapic Barmstein Limestone of the Northern Calcareous
Alps are clasts of wackestones with numerous fragments of calcareous algae (“algal debris-facies”). According to dasycladale
palaeocoenoses, several subtypes comprising different associations can be distinguished. One association is characterized
by the debris of an unknown large dasycladalean alga reported as dasycladalean alga indet. sp. 1 from different localities
in the Northern Calcareous Alps, typically forming a monospecific assemblage. Another microfacies type contains star-like
calcitic bodies tentatively referred to the morphospecies Coptocampylodon pantici Ljubović-Obradović and Radoičić, originally described as being from the Turonian of NW-Serbia. Other Coptocampylodon-like bodies represent the calcified tufts of the laterals of Selliporella neocomiensis (Radoičić). The occurrence of Coptocampylodon pantici-like microfossils in the Late Tithonian to Early Berriasian, shows that obviously different species of dasycladaleans display
identical to similar shaped tufts of laterals in transverse sections when becoming fragmented. Coptocampylodon pantici Ljubović-Obradović and Radoičić was observed only from different occurrences of Barmstein Limestone, but not from the autochthonous
platform carbonates of the Plassen carbonate platform. The Coptocampylodon algal debris-facies is also reported from the Late Jurassic of Albania, Mirdita zone. Occurrences of different types of algal
debris-facies in components of mass-flow deposits can be used as a tool to reconstruct eroded carbonate platforms and tectonics,
as demonstrated in the Northern Calcareous Alps and the Albanides. Finally, the general occurrences of algal debris-facies
in both settings—intra-Tethyan mostly isolated platforms (Alps, Albanides) vs. extended epeiric platforms (Middle East)—are
compared and discussed. 相似文献