155,252 research outputs found
Orthophragminid and operculinid events at the Middle-Upper Eocene boundary in Europe.
No full textIn some Middle Lutetian (Gibret, Nousse and Angoumé, France), Upper Lutetian (Ajka and Padragkút in Hungary) and Lower Bartonian (Dudar in Hungary, San Pancrazio in Italy and Biarritz, Rocher de Peyreblanque in France) localities (see Less, 1998) the richest orthophragminid assemblages ever seen can be found. The members of nineteen evolutionary lineages are represented in them. By comparing the orthophragminid content of the Middle and Upper Priabonian localities (Priabona, Sorgente, Valle Granella and the Middle-Upper Priabonian of Mossano in Italy and Kisgyör, Remete-kút in Hungary) with them, we find that eleven of the nineteen lineages had been lost and only five new (and rare) species appeared. The eight lineages that are coming from the Middle Eocene and surviving until the end of the Eocene are: Discocyclina dispansa, D. augustae, D. radians, D. trabayensis, Orbitoclypeus varians, O. furcatus, Asterocyclina stellata and A. stella.The orthophragminid events in the Late Bartonian and Early Priabonian can be followed in correlating them with three other successive larger foraminiferal events, such as (from top to bottom):- Event 3: The appearance of Spiroclypeus that has never been found in the Middle Eocene and with large Nummulites.- Event 2: The extinction of large Nummulites that have never been found with Spiroclypeus. Their supposed occurrence (especially of N. ex gr. millecaput) in the Upper Eocene of Slovakia and Armenia has to be carefully studied. Papazzoni & Sirotti (1995) recognized a considerable gap between Events 2 and 3 in N Italy whose duration however, has to be analysed in other regions, too. Papazzoni (this volume) stressed the possible bias of local paleoecological conditions on the biostratigraphical distribution of some species.- Event 1: The appearance of involute Heterostegina (former Grzybowskia) that can be found with the last large Nummulites in some sections of N Italy (Papazzoni & Sirotti, 1993 and 1995), Poland (Bieda, 1963), Armenia (Nemkov, 1967) and Urhida in Hungary (our new data).Recently Event 3 seems to be the most adequate for placing the lower boundary of the Priabonian as it has been found by Papazzoni & Sirotti (1995) because it appears exactly at the base of the Priabonian in the Mossano section. At the same time, the rapid nepionic acceleration of Heterostegina reticulata manifested in the strong reduction of non-subdivided, operculinid chambers (parameter X shows their number in the spire of the A-forms, including the proloculus) can be considered the most reliable evolutionary clock in order to calibrate the events listed above. By using the Papazzoni & Sirotti (1993) data from the Mossano section and our new data from Urhida and Noszvaj, Hungary the evolution of parameter X can be sketched as follows:- X (mean) reduces from at least 15-16 to 7-9 between Events 1 and 2 (sample Mossano 2 of Papazzoni & Sirotti, 1993 and two new samples from Urhida, Hungary).- No statistical data from between Events 2 and 3.- X (mean) is about 5 just after Event 3 (sample Mossano 10 of Papazzoni & Sirotti, 1993).- It reduces until 3 in the following part of the Priabonian (sample Mossano 16 in Papazzoni & Sirotti, 1993 and a new sample from Noszvaj, Hungary).The lineage of Assilina schwageri-alpina also shows a rather rapid increase of the proloculus of the A-forms in the Bartonian-Priabonian interval as indicated by Papazzoni (1998) and confirmed by our data from Urhida, Noszvaj and Kisgyör, Remete-kút (Less, 1999), too. According to these, the inner cross diameter of the proloculus of A-forms is about 125-135 μm at the Middle-Upper Eocene boundary (Event 3). At the same time, it is difficult to follow the development of the Operculina roselli-gomezi lineage in the context of the events listed above, mostly because the boundary of the two successive species is not clearly defined. However, this lineage is very frequent in some samples listed below after Event 1, so it needs further studies.For characterizing the orthophragminid events around the Middle-Upper Eocene boundary several samples have been used: The Middle-Upper Lutetian (O.9-11 orthophragminid zones) and Lower Bartonian (O.12-13) ones listed at the beginning of this paper were formed before Event 1, while the Middle-Upper Priabonian (O.15-16) ones well after Event 3. The other samples (their orthophragminid fauna was seen and evaluated by the author: all they indicate the O.14 zone with a few exceptions shown in brackets) are:- Between Events 1 and 2: Gurb (O.13) in Spain (Papazzoni & Sirotti, 1995 using also Hottinger, 1977, fig. 38 and C. Ferrández's unpublished data), Siest in France (Less, 1998), samples from Mossano, Italy: MOSS 1 and 11 in Papazzoni & Sirotti (1995) (MOSS. 001 and 2 in Papazzoni & Sirotti, 1993), Mossano 31 (~MOSS 11) (Schweighauser, 1953, see also in Less, 1998), new samples from Hungary (see them in the Field-trip guide-book of IGCP 393 for 2000): Bajót, Domonkos Creek section, "millecaput" beds, Urhida "millecaput" beds.- Between Events 2 and 3: Samples Igualada 4-5 in Spain (Papazzoni & Sirotti, 1995, using also C. Ferrández's unpublished data) and MOSS 16 (former MOSS. 7) of Mossano, Italy (Papazzoni & Sirotti, 1995).- After Event 2 but in uncertain relationship with Event 3: New samples from Bajót, Hungary, "Discocyclina + Operculina" beds: Domonkos Creek section and the quarry W of the village (O.15).- Just after Event 3: Samples in Mossano, Italy: MOSS 20 (former MOSS. 10) in Papazzoni & Sirotti (1995), Mossano 44 (O.14/15) and 50 (O.15) (Schweighauser, 1953, see also in Less, 1998 as well as sample MOSSA), a new sample from Hungary: Urhida, "Discocyclina" beds.Therefore, two main orthophragminid extinction events could be distinguished at the Middle-Upper Eocene boundary, the first (Event α) occurring before or simultaneously with Event 1, while the second (Event β) after Event 3.- Event α: Five of the eleven lost lineages cannot be found after Event 1. These are: Discocyclina pulcra, D. spliti, Nemkovella katoae, Orbitoclypeus douvillei, and O. schopeni (the latter is extremely rare already in the Middle-Upper Lutetian and Lower Bartonian). These lineages became extinct very likely well before the end of the Bartonian, in the SBZ 17 zone of Serra-Kiel et al. (1998) (or in the case of D. spliti maybe even in SBZ 16). This event roughly coincides with the extinction of some nummulitid lineages such as Assilina exponens and probably also Nummulites brongniarti and N. puschi.- Event β: Four of the six lineages having survived the first orthophragminid extinction event, Nemkovella strophiolata, Asterocyclina alticostata, A. kecskemetii and Discocyclina pratti can still be found with the first Spiroclypeus (the first two in Mossano, the last three in Urhida), thus they surely survived Event 3. The fifth lineage, D. discus also survived at least Event 2 as it can be found in the Bajót, Domonkos Creek section. Since Event 3 could not be detected so far in this region, this extinction is joined with that of the previous four lineages. Finally, the sixth lineage, Orbitoclypeus daguini (with last occurrence in Gurb) is so rare (altogether 10 specimens from 6 localities are known) that its extinction can be tentatively placed together with that of the other five lineages.As it is mentioned earlier, five new orthophragminid species appeared in the Priabonian. They are so rare that here only their first occurrences are listed without any further conclusions: Discocyclina nandori in sample MOSSA (O.14 zone), between Events 3 and 4; D. euaensis in the quarry W of Bajót (O.15), between Events 2 an 4; D. samantai (the ribbed variant of D. pratti minor, the last member of that lineage) in the "Discocyclina" beds of Priabona (O.14), after Event 3 and in the Lábatlan, Raibl-patak quarry (Less, 1987) (O.15), before Event 4; D. ruppi (see Rasser et al., 2000) in the "Discocyclina + Operculina" beds of the Bajót, Domonkos Creek section (O.14), after Event 2; Asterocyclina priabonensis in sample Mossano 44 (O.14/15), between Events 3 and 4.As it is clear from the list of orthophragminid samples representing the Bartonian-Priabonian transition, Event 1 can very probably be placed into the uppermost part of O.13 zone, Events 2 and 3 into the O.14 zone while Event 4 into the lower part of O.15 zone, thus almost the whole interval between Events 1 and 4 belongs to the O.14 zone within which the development of orthophragminid lineages is hardly detectable. By using our new data from Urhida and Bajót, Domonkos Creek, the only change is that Discocyclina pratti pratti is succeeded by D. pratti minor (their limit based on the population mean of the outer cross diameter of the deuteroconch is 700 μm) that could happen between Events 1 and 2.This research is a contribution to IGCP 393 and was supported by the National Scientific Fund of Hungary (OTKA, grants 23880, 32370), and by the Italian MURST 60% fund (responsible Prof. A. Sirotti, Italy)
What, If Anything, Is A Nummulite Bank?
No full textSince the introduction of the concept of a “nummulite bank” more than 50 years ago, the significance of these peculiar sed- imentary structures has been debated, especially whether they are of autochthonous or allochthonous origin. At first consid- ered as substantially autochthonous, an alternative interpreta- tion as allochthonous deposits was suggested in the mid-1980s to explain the observation of sedimentary features indicating displacement of the nummulite tests. In more recent litera- ture, we found examples of non-uniform use of the nummulite bank concept; sometimes the ‘banks’ are vaguely described as nummulite-rich beds, and illustrations may not allow recog- nition of the features characteristic of the real banks. In an attempt to achieve a scientifically robust model explaining the genesis of the nummulite banks, our objective was to test the original definition, based upon the most fundamental and use- ful characteristics that can be observed in the field, even in non- optimal outcrop conditions: the A/B ratio and the percentage composition (dominance) of the fossil assemblage. Both can be quantified using simple techniques on samples collected for this purpose.
In an extensive survey of nummulite banks and non-banks from Italy, Spain, Romania, and Germany, we determined A/B ratios and taxonomic composition of the nummulite as- semblages. Recognized nummulite banks are characterized by A/B ratios 75% of the larger foraminiferal assemblage
La Pietra di Vicenza nel Duomo di Modena e nella Torre Ghirlandina: analisi micropaleontologica e identificazione delle località di estrazione.
No full textL’analisi micropaleontologica della Pietra di Vicenza rinvenuta nei paramenti lapidei del Duomo di Modena e della Torre Ghirlandina, monu- menti facenti parte del Sito Unesco della città, ha permesso di riconoscere 4 facies con caratteristiche di tessitura e di contenuto fossilifero che ne permettono la distinzione. La comparazione con materiali archeologici provenienti dai resti della città romana ha permesso di individuare le pietre reimpiegate in epoca medievale per la costruzione dei monumenti sopra citati.
Una estesa campagna di campionamento nell’area lessineo-berica ha poi consentito di individuare con discreta precisione le località di estrazione dei materiali usati a Modena in diverse epoche, mediante il confronto tra le caratteristiche micropaleontologiche dei campioni di provenienza nota e le medesime caratteristiche osservate nei materiali lapidei usati per gli edifici modenesi.The micropaleontological analysis of the “Pietra di Vicenza” (Vicenza stone) slabs covering the outer walls of the Modena Cathedral and the Ghirlandina Tower, monuments that are part of the UNESCO Site of this city, allowed to recognize 4 facies with characteristics textures and fossil contents allowing their distinction. The comparison with some archaeological materials from the remains of the ancient Roman city allowed to identify the stones reused in medieval times for the construction of these monuments.
An extensive sampling campaign in the Lessini-Berici area (Veneto region) allowed to identify with reasonable precision the locations of extraction of the materials used in Modena in different periods, by comparing the micropaleontological characteristics of the samples of known origin with the same characteristics observed in the stone materials used for buildings in Modena
I reperti fossili conservati presso i magazzini di Palazzo Ducale: una eccezionale documentazione di storia naturale e umana.
No full text453 reperti fossili conservati presso i magazzini del Palazzo Ducale di Mantova sono stati preliminarmente riordinati e studiati per ricostruirne la storia e il significato. Di questi una piccola parte è stata utilizzata per un percorso espositivo all'interno del medesimo Palazzo Ducale. La ricognizione ha permesso di correggere alcune determinazioni errate e ha sollevato alcuni interrogativi relativi alla provenienza dei fossili
Stima della diversità specifica del genere Nummulites durante la crisi biologica al passaggio Eocene medio/superiore
No full textL'obiettivo di questo lavoro è di stimare l'incidenza delle estinzioni sulle specie del genere Nummulites durante il periodo di massima crisi del genere stesso, ovvero tra la fine dell'Eocene medio e l'inizio dell'Eocene superiore.Tra la sterminata bibliografia esistente sul genere Nummulites, si è scelto, per semplicità, di utilizzare le sintesi monografiche più importanti degli ultimi decenni, ovvero Blondeau (1972, pp. 84-85) e Schaub (1981, figg. 24-25). Per confronto, all'elaborazione di questi database (considerati acriticamente) è stata affiancata quella dei dati da me raccolti per la tesi di dottorato (Papazzoni, 1993). Infine, si è tentata una elaborazione critica di tutti i dati dei tre database per verificare eventuali somiglianze o differenze rilevanti (Tab. 1).Sono state distinte tre modalità di estinzione:1) estinzioni terminali (et; vere estinzioni sul limite);2) estinzioni terminali anticipate (eta; vere estinzioni, che però avvengono ad un livello leggermente inferiore rispetto al limite);3) estinzioni filetiche (ef; pseudoestinzioni).Dall'elaborazione dei database esistenti si possono trarre alcune considerazioni conclusive:1) la crisi dell'Eocene medio/superiore non è improvvisa; in essa si possono riconoscere almeno due fasi successive, corrispondenti ai limiti di biozona indicati con (a) e (b) in Tab. 1, con tassi di estinzione paragonabili;2) l'IE calcolato è sempre più elevato nel caso del limite (b); se confermato, ciò indicherebbe che esso è il miglior candidato a rappresentare il limite Eocene medio/superiore, anche se non coincide con la scomparsa dei grandi nummuliti (avvenuta in (a));3) i patterns di estinzione registrati non si accordano con cause improvvise o catastrofiche; le ipotesi legate ad un cambiamento climatico sembrano più coerenti con i dati disponibili; del resto, in questo intervallo temporale sono state registrate indicazioni di abbassamento eustatico del livello marino (Haq et al., 1987), cambiamenti nella circolazione oceanica (Kennett & von der Borch, 1986), inizio della stratificazione psicrosfera-termosfera (Benson, 1975), e significativo raffreddamento globale (Keller, 1983)
Palaeoecological significance of coral-encrusting foraminifera associations. A case study from the late Eocene of the Nago Limestone (Northern Italy)
No full textEncrusting foraminiferans, although representing an important component of the so-called cryptic assemblages in both modern and ancient reef environments, are in general poorly described and little is known as regards their association with corals. In this paper, we describe coral-encrusting foraminiferan associations in the different facies that characterize the shallowing upward parasequences of the Nago Limestone (Upper Eocene, Trentino, northern Italy). From a relatively deep reef slope up to the shallow shelf-edge, corals have been recognized to be encrusted by different types of foraminiferan assemblages that differ on the basis of relative abundance of species, growth form and type of encrusted coral surface. The succession of encrusting foraminiferan assemblages is interpreted as controlled mainly by light, competition with coralline algae, hydrodynamic energy, and coral growth fabric
Studio micropaleontologico dei fanghi delle Salse di Nirano
No full textI fanghi estrusi dalle Salse di Nirano sono stati per la prima volta esaminati allo scopo di determi- narne il contenuto in microfossili. L’analisi di 14 campioni prelevati da coni, polle e colate, più uno di confronto prelevato nella stessa area ma al di fuori della zona di attività lutivoma, ha permesso di isolare una fauna a foraminiferi (bentonici e planctonici) piuttosto ricca e diversi cata, comprenden- te 97 specie e 50 generi diversi. Le associazioni fossili sono piuttosto omogenee e tutte compatibili con l’età plio-pleistocenica della Formazione delle Argille Azzurre che af ora al margine appennini- co. I dati di questa prima analisi sembrano suggerire che la produzione dei fanghi avvenga entro un serbatoio relativamente super ciale.Preliminary micropalaeontological study of the muds of the Nirano mud volcanoes. A micropalaeontological analysis of the muds of the Nirano mud volcanoes was carried out in order to determine their microfossil content. Fourteen samples were taken from cones, level-pool mud vents and mud ows, whereas a fteenth sample was collected for comparison outside the mud volcano area. Overall, they revealed a rich and diversi ed foraminiferal fauna (both benthic and planktonic), with 97 species and 50 different genera. The fossil assemblages are fairly homogeneous and all consistent with the Plio-Pleistocene age of the “Argille Azzurre” Formation cropping out at Pede-Apennines. Therefore, these data suggest that mud production takes place within a relatively super cial reservoir
Paleoecology and biostratigraphy in the Mossano section: effects of the paleoecological bias on the biostratigraphical resolution
No full textThe larger foraminiferal assemblages from the Mossano section (Berici Mts., Vicenza province, Northern Italy) were re-examined, mainly based on the data reported by Papazzoni & Sirotti (1995).An attempt was made to assign to each species (or species-group) a paleoenvironment (inner, middle, or outer platform) by comparing the percentages of co-occurrence with eight selected species (or species-groups). They are, respectively: Orbitolites sp., Calcarina sp., Alveolinidae, and Miliolidae for the inner platform (IP), Orbitoclypeus spp. for the middle platform (MP), Asterocyclina spp., Discocyclina spp., and Nemkovella spp. for the outer platform (OP) (Tab. 1). Attributing to each paleoenvironment a score (IP=100; MP=200; OP=300) lead to recognize six sets of species (or species-groups) belonging to different parts of the platform, plus a set of ubiquitous (UBIQ) species (or species-groups). Making the arithmetical mean of the individual scores of each species recognized in a sample (excluding the ubiquitous ones) allowed assigning a score (and therefore a paleoenvironment) to every sample considered (Tab. 2).The numeric results were plotted into a diagram showing a quite detailed "signal" of the shifting paleoenvironments. We can use this diagram to test the biostratigraphical data, i.e. to determine if the appearance and disappearance of the species could be or not linked to the shifting paleoenvironments.The succession of the paleoenvironments shows, into the limestones, a more or less gradual transition from an outer platform environment, roughly corresponding to the Nummulites lyelli Zone, to a middle platform (N. biedai Zone), and an inner platform (N. variolarius/incrassatus Zone). The lithological change from the limestones to the marls corresponds to a sudden change in the assemblages (with a "jump" from the score 158 of the sample MOSS 18 to the 253 of MOSS 19), marking a shift from the inner to the outer platform. This is consistent with the interpretation made by Papazzoni (1994).It does appear clearly that some of the key species to establish the biozonation are facies-dependant. This is the case of Nummulites lyelli and N. cf. dufrenoyi (=N. maximus of Serra-Kiel et al., 1998) both attributed here to the middle/outer platform (M/OP), and of Spiroclypeus carpaticus (=S. granulosus auct.), indicating the outer platform. It seems that the species of the middle and inner platform are less tightly linked to the facies (see e.g. N. beaumonti/discorbinus, attributed to the inner platform, but widespread in nearly all the limestones).The new proposal of biozonation of Serra-Kiel et al. (1998) raises some problems if applied to the Mossano section. The main incongruity is the simultaneous presence of N. lyelli and N. biedai. According to Serra-Kiel et al. (1998, fig. 3) these species belong to different SB Zones (17 and 18 respectively) and their range never overlap. This could be the usual situation, but the species belong to different paleoenvironment, so it is difficult to ascertain if the disappearance of N. lyelli is real or due to a facies change. At least in Mossano (and in Pradipaldo; see Papazzoni & Sirotti, 1995, tab. 2) the stratigraphical range of the two species do overlap.A similar problem is the disappearance of N. biedai. In Mossano this event corresponds to a facies change from the middle to the inner platform, but N. biedai results characteristic of the middle platform, therefore the considerations exposed above could be repeated. The uncertainties in recognizing the disappearance of N. biedai complicate also the definition of the N. variolarius/incrassatus Zone (=N. aff. fabianii Zone).Nevertheless, I think the effects of the widespread sea level lowering near the end of the Middle Eocene forced most of the carbonate platforms to regression. Therefore, the succession of the paleoenvironment is nearly the same in several different localities, leading to about the same succession of events. This should be the reason why, even in presence of some paleoenvironmental bias, the biozonation still works.ReferencesPapazzoni C.A. (1994) - Macroforaminifera and paleoenvironments near the Middle-Upper Eocene boundary in the Mossano section (Berici Mts., Vicenza, northern Italy). In Matteucci, R., Carbone, M.G. & Pignatti, J.S. (eds), Studies on Ecology and Paleoecology of Benthic Communities. Boll. Soc. Paleont. Ital., Spec. Vol. 2: 203-212.Papazzoni C.A. & Sirotti A. (1995) - Nummulite biostratigraphy at the Middle/Upper Eocene boundary in the northern Mediterranean area. Riv. Ital. Paleont. Strat., v. 101, n. 1: 63-80.Serra-Kiel J., Hottinger L., Caus E., Drobne K., Ferràndez C., Jauhri A.K., Less G., Pavlovec R., Pignatti J., Samsó, J.M., Schaub H., Sirel E., Strougo A., Tambareau Y., Tosquella J. & Zakrevskaya E. (1998) - Larger foraminiferal biostratigraphy of the Tethyan Paleocene and Eocene. Bull. Soc. géol. France, 169(2): 281-299
Paradigm changes in Paleogene larger foraminiferal biozonation
No full textA. Oppel’s seminal work in the 19th century contributed to the rise and development of biostratigraphy by means of what have now become known as the Oppel zones. This powerful and flexible tool, first used for Jurassic-Cretaceous ammonoids, was later employed for establishing biozonal schemes by using different fossil groups.
The historical development of Paleogene larger foraminiferal biozonations is a striking example of change of zonation paradigms in time. A historical overview of these changes and their rationale, starting from the 1850’s, shows the changing role of early biozonations, Oppel zones, phylozones, chronozones, and datums.
A rigorous definition of Paleocene-Eocene Oppel zones based on alveolinids and nummulitids for the western Neo-Tethyan domain was mainly due to the influential work of L. Hottinger and H. Schaub in the 1960’s. In their taxonomic approach, species and subspecies were typologically defined. Their Oppel zones are based on stratigraphically ordered key localities and their assemblages; the resulting zonation is discontinuous, being separated by intervals of unknown extent and not by sharp boundaries, as in continuous zonations. The choice of these key localities from the Mediterranean Neo-Tethyan domain was influenced firstly by the presence of larger foraminiferal assemblages and their historical significance, inasmuch many are type localities for species group taxa. Secondly, their vertical ordination reflected basic criteria of geological superposition and correlation with calcareous planktonic and nannofossil zonations. Thirdly, the sedimentary settings of these key localities were mainly neritic (in part, also deeper flysch deposits with their allochthonous assemblages were included) and thus their fossil record was intrinsically discontinuous, i.e. linked to unconformity- bounded units.
A different biometrical tradition in larger foraminiferal studies, which originated in the 1930’s especially in radial (orbitoidiform) larger foraminifera and Oligo-Miocene nummulitids, led to the construction of zonal schemes based on phylozones based by chrono(sub)species represented by arbitrary segments of evolutionary lineages. In contrast to Oppel zones, phylozones based on this approach produce continuous zonations. This research program achieved its most complete formulation with C.W. Drooger and coworkers, and later studies in orthophragmines by G. Less.
A change in paradigm took place in the late 1990’s, when Serra-Kiel and coworkers attempted to reconcile in a modern research program Paleogene larger foraminiferal Oppel zones and phylozones and supersede the previous approach with chronozones, mainly based on the calibration of larger foraminiferal zones with magnetostratigraphy from the Iberian peninsula. The refinement of this research program is still ongoing, also drawing upon new correlations with the plankton stratigraphy, magnetostratigraphy, and isotopic data
Il contributo dell’indagine geologica per stabilire la provenienza della stele di Cattolica
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