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1.
A new stratigraphic unit (named LM unit) located at the base of the Pliocene marine succession in the eastern sector of the Malaga Basin has been distinguished. This unit is composed of two fining-upward sequences bounded by a discontinuity related to synsedimentary tectonic activity. Both sequences are made up of basal alluvial deposits overlain by subaquatic deposits. The lower sequence contains rich mollusc faunas characterized by bivalves Lymnocardiinae and Dreissenidae of Paratethyan origin, and non-marine gastropods, typical of oligo-low mesohaline shallow waters, and low diversified ostracod faunas of Paratethyan origin (Loxocorniculina djafarovi, Tyrrhenocythere pontica, Euxinocythere (Maeotocythere) praebaquana and Amnicythere propinqua) typical of low mesohaline waters. Alternances of monospecific ostracod assemblages made of Cyprideis agrigentina or oligotypic assemblages made of C. agrigentina and Loxoconcha spp. and richer assemblages made of L. djafarovi accompanied by several Amnicythere spp. and Camptocypria sp.1 characterize the upper sequence, pointing to more unstable environment affected by salinity and depth changes. Some samples collected from this upper sequence yielded rare, planktonic and benthic foraminifera, which could suggest the sporadic establishment of quasi-normal marine conditions in the westernmost Mediterranean during the deposition of this sequence. The palaeontological data and the palaeomagnetic results obtained in both the LM unit and the overlying Pliocene marine sediments restrict the age of the former to the post-evaporitic late Messinian. The age and the environmental conditions correlate these deposits with the Lago-Mare event occurring throughout the Mediterranean before the quick and widespread marine flooding of the Mediterranean at the beginning of the Pliocene.  相似文献   

2.
Late Miocene Lago-Mare macrofossiliferous sediments were recovered in the northeastern Tyrrhenian Sea by dredging the continental slope off Gorgona Island, Tuscan Archipelago, at 300-470 m depth. The fossil assemblage consists of a rich lymnocardiid bivalve fauna dominated by Pontalmyra ex gr. P. incerta (Deshayes), associated with Dreissena ex gr. D. rostriformis (Deshayes), Pontalmyra cf. partschi (Mayer), “Limnocardium” sp., the gastropods Melanopsis narzolina (D’Archiac), Melanopsis sp. and cf. Saccoia sp. All bivalve taxa recognized at species level are of Paratethyan (Pontian) affinity and widespread in the Late Miocene of the Mediterranean Basin while M. narzolina has so far only recorded from the Mediterranean Basin. This finding represents the most diverse Lago-Mare macrofauna reported thus far from any submerged location in the Mediterranean Basin and documents that the post-evaporitic Cusercoli Formation contributes to the syn-rift neoautochthonous units of this sector of the Northern Tyrrhenian Sea.  相似文献   

3.
Two possible alternative interpretations of the claimed Zanclean age (Popescu et al., 2007) of two historical lithostratigraphic units of the Northern Apennines, usually referred to as Late Messinian in age and recording the so called Lagomare final event of the Messinian salinity crisis (MSC), are here discussed. The wrong age attribution of the Colombacci and “tetto” Fms. is ruled out based on data from the Maccarone and other sections showing that the Colombacci-Argille Azzurre Fm. boundary is basin wide synchronous and coincident with the Miocene-Pliocene boundary as far as it has been formally defined in the Eraclea Minoa GSSP. Alternatively, the opportunity of emending the Zanclean GSSP to a stratigraphically lower horizon recording the first evidence of marine influences in the Mediterranean following the MSC peak, seems not suitable, as (1) the marine signature of uppermost Messinian deposits is weak and still controversial and (2) no significant bio- and magnetostratigraphic events, well chronologically defined and recognizable at a global scale appear to be available to such a purpose.  相似文献   

4.
The study of otolith assemblages from the pre-evaporitic Messinian deposits allows the reconstruction of a fauna of 79 taxa of which 35 could be identified at the specific level. Three of these are new: Diaphus rubus, Myctophum coppa, and Uranoscopus ciabatta. The assemblages reflect mainly a neritic environment influenced by the oceanic realm. Analysis of the global present-day geographic distribution of 42 of the recognised Messinian genera indicates that 88% of these are still living in the Mediterranean, 98% in the Atlantic and 78% in the Indo-Pacific realm. These results are in good agreement with the evolutionary trends documented for the Oligocene and Miocene teleost fauna, specifically an increase in percentage of genera inhabiting the modern Mediterranean, a very high percentage of Atlantic and Indo-Pacific genera, and a slight fall of the importance of present-day Indo-Pacific genera from the Rupelian up to the Late Miocene. Analysing the composition of the Early Messinian fauna at the level of nominal species indicates that about 53% of the species represented in the assemblages are still living in the Recent Mediterranean, and that a significant number of these were already present in the Tortonian. It is interesting that these species are mainly neritic. This seems to confirm that the close affinity of the fossil assemblage with the present-day Mediterranean neritic fauna, which was already recorded at the genus level for the Rupelian fauna, persists during the Neogene and continues until the Pleistocene.  相似文献   

5.
A better understanding of Mediterranean-Paratethys water-exchange during the Messinian Salinity Crisis has since long been hampered by the absence of a reliable time frame for the Paratethys. High-resolution magnetostratigraphic studies on the sedimentary sequences of the eastern and southern Carpathian foredeep recently resulted in an accurate chronology for the Mio-Pliocene deposits of the Dacic Basin of Romania. This allowed a straightforward correlation of the Pontian and Dacian stages to the geological time scale, which revived earlier discussions on Mediterranean-Paratethys connectivity. Here, we present Pontian and Dacian mollusc assemblages of the Getic Depression (Topolog-Arge? area, southern Carpathians) of Romania, which are incorporated in a magnetostratigraphic time frame. They indicate that a hiatus - comprising the Early Pontian - is present in the stratigraphic successions, which could be related to a base level drop of the Paratethys water column or to more local tectonic processes. The mollusc assemblages furthermore show a gradual transition at the Pontian/Dacian boundary, which is magnetostratigraphically dated at ∼4.9 Ma. This is significantly later (by more than 400 kyrs) than the Mio-Pliocene boundary in the Mediterranean sequences.  相似文献   

6.
A stratigraphical chart of marine ostracoda from Lower Miocene to Recent is established. Selected species (approximatively 220) are those morphologicaly well characterized and known from different parts of the Mediterranean area. It appears that: • lower Miocene ostracodes are still poorly known; • specific diversity is high during the Tortonian and the Lower Messinian before the complete disappearance of marine Mediterranean species during the Upper Messinian évaporitic episodes; • during the early Pliocene, about half of the Upper Miocene marine species are reintroduced with the Atlantic waters; other species migrate for the first time in the Mediterranean Sea by the same way; • at the end of the Pliocene or at the beginning of the Pleistocene several species known in Mediterranean since the Middle Miocene or before, such as Cytherella sp. gr. transversa and Ruggieria tetraptera, as well some “nordic guests” such as Hemicythere villosa and Cythere lutea, appear. This work is an opportunity to confirme a Late Miocene age for the Neogene of Skyros (Aegean Sea), to assign the “Upper Pliocene” of Terquem to the Lower Pleistocene and to refute the existence of a pliocene psychrosphere.  相似文献   

7.
In this paper the ostracod assemblages recovered from several brackish Late Miocene Italian deposits have been analysed from a palaeobiogeographical perspective. During late Tortonian-early Messinian it is possible to recognize in Italy rich ostracod assemblages characterized by a wide contingent of taxa with central European or Mediterranean affinity, while only few brackish and freshwater ostracods show Paratethyan affinity. The recognized composition of the ostracod assemblages matches the palaeogeographic setting of the palaeo-Mediterranean/Paratethys at that moment. In fact during late Tortonian-early Messinian the palaeo-Mediterranean and Paratethysian domains were divided and, even if the connection via the present Marmara Sea-Strimon Basin was still open, the different salinity between them represented an ecological barrier, preventing faunal exchanges. Since normal aquatic migration was impossible, it must be assumed that the Paratethyan-like taxa entered the palaeo-Mediterranean area via passive dispersal by aquatic birds. On the contrary, the ostracod assemblages from the Italian Lago-Mare deposits show the absolute predominance of Paratethyan taxa, which, according to the known palaeogeographic setting during the late Messinian Lago-Mare event, could actively migrate from the Paratethys domain, colonizing the palaeo-Mediterranean, whose endemic fauna was severely impoverished by the Messinian salinity crisis and the following water dilution.  相似文献   

8.
The desiccation of the Mediterranean Basin at the end of the Miocene was a milestone in the evolution of the Mediterranean sandfly fauna. This severe environmental change should have notably influenced their paleobiogeography as well as paleoecology and might have triggered the rapid speciation of the ancestors of the extant European sandfly species. The aim of this study was to explore how the Messinian Salinity Crisis could influence the distribution and migration routes of the ancient Mediterranean sandfly species. The unknown ecological requirements of this ancient species were replaced by the distribution-limiting climatic values of three species of extant European phlebotomine sandflies which represent the three ecological types of European sandfly fauna. The former potential occurrence patterns were determined by Climate Envelope Modelling Method. As a climate model for the Messinian Period in the Mediterranean Basin, the modified mid-Pliocene warm period model was used. The thermal surplus of the desiccated seafloor was reconstructed based on the atmospheric lapse rate. It was found that the extraordinary hot climate of the Mediterranean abyssal plain did not allow the direct cross-migration of the ancient sandfly species anywhere between Europe and North Africa neither through Gibraltar nor the Strait of Sicily. While Phlebotomus neglectus and Phlebotomus papatasi could colonize the Adriatic Plain, Phlebotomus ariasi could not. The results indicate that the Messinian played an important role in the speciation rather than migration of the ancestors of present-day Mediterranean sandflies.  相似文献   

9.
The biological impact of the Messinian Salinity Crisis (MSC) and its bearing on the Pliocene Mediterranean marine molluscan fauna has been analyzed on the basis of the biogeographic and stratigraphic distributions of the taxa of 16 early Messinian outcrops. The extinction of the last paleoendemic Proto-Mediterranean taxa is historically significant but it appears to be numerically less important than the extinction of the Tortonian and Messinian neoendemic taxa. The available data suggest that the MSC caused a regional mass disappearance but only a limited number of extinctions. It is also emphasized that the Late Pliocene (Monegatti et al., 2002) extinctions were far heavier than those caused by the MSC. We suggest that the greatest Messinian extinctions were triggered, during the salinity crisis, in the Atlantic “sanctuary” by the Messinian glacial events TG22, TG20, TG14, and TG12, of Shackleton et al. (1994), dated between 5.79 and 5.55 Ma by Krijgsman et al. (2004). A comparison between the Mediterranean Messinian and the Redonian molluscan faunas was also carried out. Finally, the possible latitudinal stability of the climatic thresholds, despite the shifting of the climatic zones throughout the Neogene along the European coast, is pointed out.  相似文献   

10.
Early ontogenetic shells of 25 species of brackish water and freshwater molluscs from the Ottnangian (Lower Miocene) Oncophora Beds (Lower Bavaria, South Germany) and Kirchberg Formation (Upper Bavaria, South Germany) are described for the first time. Taxonomic implications are discussed. The investigated bivalves (Cardiidae and Dreissenidae) were characterised by an indirect development with inclusion of a planktonic veliger stage. Among the gastropods only three species of the genus CtyrokiaSchlickum, 1965 were characterised by veliger larvae, all the other gastropod species were direct developers, which hatched as crawling young. The species Agapilia schlickumi nov. sp. (Neritidae), Nematurella pseudozilchi nov. sp. and Nematurella strauchi nov. sp. (Hydrobiidae) are introduced. Our study revealed the co-occurrence of 10 molluscan species in the Oncophora Basin of Lower Bavaria and the Kirchberg Basin of Upper Bavaria and thus indicates similar oligohaline to mesohaline coastal swamp milieus for both depositional environments. The presence of planktonic larval development in gastropods indicates a connection to the open sea.  相似文献   

11.
An articulated series of centra from latest Miocene deposits of Ukraine is described and identified as a species of Lates. The specimen comes from a locality with an estimated age of 6.04–4.7 Ma, representing the northernmost reach of the Paratethys during the Pontian. The specimen almost certainly represents a distinct species, but because it is incomplete we do not formally name it. The specimen can be differentiated from other species of Lates by features of the centra, including the relative size of the primary lateral fossa of the second centrum, the broadened neural spine of the third centrum, and the relative position of the upper and primary lateral pits on both the fifth and sixth centra. The Ukrainian specimen documents the presence of Lates in the northern Paratethys in the latest Miocene. After this time, species of Lates persisted in freshwaters in the Mediterranean area (Israel and Africa), but are no longer found in the marine waters of the region. We suggest that latines were extirpated from the Mediterranean and Paratethys by the rapidity of the changes in salinity that occurred in the Tethys Mediterranean basin and Paratethys as a result of the Messinian Salinity Crisis.  相似文献   

12.
Abstract: Eleven randomly chosen outcrops in the Miocene Pakhna Formation of Cyprus were sampled for holoplanktonic Mollusca. Four species of Heteropoda were found, and 24 of Pteropoda, a substantial increase from the two species recorded until now from the Miocene of Cyprus. One pteropod species, Peracle charlotteae sp. nov. (Gastropoda, Pseudothecosomata), is introduced. Age assignments based on holoplanktonic molluscs for the 11 localities are as follows: Langhian (Alassa 1–4), (Serravallian?) Tortonian to Messinian (Episkopi 1), Tortonian (Agios Tychon, Tokhni and the Maroni Marlstone of Khirokitia 1–2) and Tortonian to Early Messinian (Episkopi 2). These age determinations in some cases are at odds with those from previous publications based on calcareous nannofossils and Foraminifera. The sediments underlying the Amathus Channel outcrop yielded insufficient fauna for definitive dating, but we suggest are younger than Late Serravallian. At some localities, particularly in the Alassa area, pteropod assemblages are strongly variable on a bed‐by‐bed basis, and this offers possibilities for future refined biostratigraphical interpretations. This is the first substantial holoplanktonic mollusc fauna described from the eastern Mediterranean basin and allows correlation with assemblages in the central Mediterranean and elsewhere.  相似文献   

13.
The occurrence of planktonic foraminifers in the latest Messinian deposits (uppermost Di Tetto Formation and Colombacci Formation) of the Marche Province (Apennine foredeep, Italy) has stimulated a debate since the 1970s. An earlier palynological study of the entire Maccarone section revealed a pronounced, and a sudden increasing frequency of saccate pollen grains which indicates more distal conditions, and thus a transgression. At first attributed to tectonic activity, this transgression is now interpreted as representing the Zanclean marine transgression after the discovery of Ceratolithusacutus, the calcareous nannofossil marker of the earliest Zanclean in the Mediterranean Sea. Evidence from marine dinoflagellate cysts and planktonic foraminifers supports this result. The Colombacci Formation and uppermost part of the Di Tetto Formation (i.e. the entire p-ev2 stratigraphic unit) belong to the earliest Zanclean. The so-called Lago Mare no longer has a regional chronostratigraphic sense, and should be understood as the invasion of Paratethyan organisms via surface waters owing to a connection at high sea-level between the Aegean Sea and the Eastern Paratethys (Dacic Basin). A new robust environmental reconstruction of the northern Apennine foredeep is proposed, which respectively considers the effects of tectonics and Mediterranean eustasy.  相似文献   

14.
Marly sediments of the early Messinian Abad Member of the Turre Formation from the northeastern sector of the Carboneras-Nijar Basin (southern Spain) have yielded a rich fossil assemblage, of which 60 taxa are documented herein. Besides nannoflora and microfauna, this assemblage includes the first autochthonous macrofauna described from the Abad Member. Based on the calcareous nannofossil assemblage, in particular the occurrence of the zonal index taxon Amaurolithus primus, the sediments are assigned to the Mediterranean calcareous nannofossil zone CNM17, corresponding to the latest Tortonian to earliest Messinian interval. This matches the age range generally reported for the Abad Member. Palaeoecological evidence from calcareous nannofossils (20 autochthonous taxa), planktic and benthic foraminifera (12 taxa), Porifera (3 taxa), Octocorallia (Keratoisis), Serpulidae (4 taxa), Bivalvia (5 taxa), Gastropoda (2 taxa), Brachiopoda (7 taxa), Cirripedia (Faxelepas) and Vertebrata (5 taxa) indicates an upper bathyal environment with an influx of neritic elements for the Abad Member near Carboneras. Additionally, several faunal components may represent allochthonous/parautochthonous elements from adjacent habitats, which were transported into the deep marine setting by turbiditic mass flows. Although similarities exist, the fossil assemblage from the marls is compositionally significantly different from the biota previously documented from a nearby exposed olistostrome, the ‘red breccia’. Similar fossil assemblages from the Mediterranean have so far mainly been reported from the Pliocene-Pleistocene of southern Italy and Greece. The Carboneras fauna thus adds to our knowledge of the development of these habitats and their biota prior to the Messinian salinity crisis. Beyond the novel palaeoenvironmental data, the range of the dyscoliid brachiopod Ceramisia meneghiniana, previously known only from the Pliocene of Italy, is extended to the Miocene of Spain. The cirripede crustacean Pycnolepas paronai De Alessandri, 1895 is transferred to the hitherto monospecific genus Faxelepas Gale, 2015, whereby the range of the latter (previously Maastrichtian to Danian) is extended to the late Miocene.  相似文献   

15.
Integrated data of calcareous nannofossils, as well as planktonic and benthic foraminifera from the Pissouri Motorway section on Cyprus allow the reconstruction of surface- and bottom-water paleoenvironments of the eastern Mediterranean during the interval preceding the Messinian salinity crisis (MSC). Contrary to deeper-water locations, where benthic foraminifera faunas are suppressed or absent just after the Tortonian–Messinian boundary, sediments deposited at intermediate water depths do contain benthic assemblages. From the earliest Messinian onwards, a development towards increasingly unfavourable paleoenvironments is reflected in the planktonic and benthic microfossil records of the Pissouri section and proceeds with rather discrete time steps that can be correlated to sequences throughout the Mediterranean. Shortly after the Tortonian–Messinian boundary a transition is recorded in the sedimentology and the open marine, deeper-water taxa disappear from the benthic foraminifera assemblages; subsequently, the diversity of all fauna groups diminishes. The changes recorded at species level in both surface-water and sea-floor dwelling taxa suggest decreasing circulation of the bottom waters, associated with changes in the surface waters, most likely due to increasing stratification. From ∼6.73 Ma onwards, our data indicate a prominent change to more restricted conditions and increasing salinity at the sea floor together with intermittently rising surface water salinity. The dominance of oligotypic and monospecific assemblages and the frequent shifts in assemblage compositions of all microfossil groups indicate severely stressed environments after ∼6.4 Ma, probably related to increased salinity. The major changes in paleoenvironmental conditions, including oxygen deprivation due to stagnation and hypersalinity, can be explained by hydrographical changes in the Mediterranean basin, which are probably caused by tectonic movements in the Rif Corridor acting in concert with astronomical cyclicity. Evaluation of the paleodepth proxies indicates that the depth of the Pissouri Basin remained rather constant at ∼300–500 m, with a minimum of 200 m, until deposition of the “barre jaune”, the transitional interval towards the evaporites and that early shallowing to neritic depths, as was proposed before, is highly unlikely.  相似文献   

16.
The fossiliferous levels of Caune de l'Arago supply a useful tool to investigate the relationships between faunal renewals and climate changes in a restricted area during the Middle Pleistocene. On the other hand the Italian fossil assemblages of the middle Galerian testified changes of palaeoenvironmental conditions. A biochronologic and palaeoecologic comparison among large mammalian faunas of these quite different Mediterranean regions have been performed in the aim to value possible vicariance of taxa and differences of faunal renewal dynamic during the Middle Pleistocene. After the results of our analysis we can correlate the faunal assemblages from the “Complexe moyen, ensemble stratigraphique I”, “Complexe moyen, ensembles stratigraphiques II and III”, “Complexe supérieur, sols A and B” of Caune de L'Arago sedimentary succession with the Italian Isernia (middle Galerian), Fontana Ranuccio (late Galerian) and Torre in Pietra (early Aurelian) faunal units (FUs) respectively. The French faunal assemblages were characterised by the absence of browsers and, conversely, by the presence of boreal taxa, mainly grazers, that were rare or never occurred in Italy. Accordingly, at no one Italian faunal complex, as expected, we can find any indication of continental cold climatic condition as showed by the faunal complexes of the Caune de l'Arago. Nevertheless, the major climate changes characterising the Middle Pleistocene can be detected in both regions. During the span time of Isernia FU, the temperature was at its lowest and arid conditions prevailed, whereas during the following Fontana Ranuccio FU humidity and temperature increased, as is more evident in central Italy local faunas. Moreover, after the similarity analysis, the Visogliano local fauna (North-Eastern Italy) was more related to the French than to the Italian ones. During the late Middle Pleistocene (Torre in Pietra FU) a moderate faunal reconstruction can be detected in both regions. The renewal was linked to climatic modifications taking place in the Mediterranean area approximately around OIS 11/OIS 10 transition, when interstadials became progressively milder and average humidity increased.  相似文献   

17.
The Messinian pre-evaporitic sedimentary succession of Gavdos Island (Metochia section) is a nearly uninterrupted succession of marine sediments, dominated by finely laminated diatomaceous marls, which are cyclically alternating with clayey diatomites and white diatomites. The qualitative and quantitative analysis of the planktonic foraminiferal fauna allowed the recognition of nine bioevents, which have been astronomically dated for the Mediterranean. The base of the diatomitic succession in Gavdos Island is dated at 6.722 Ma and the top at 6.015 Ma. The studied section contains benthic foraminiferal genera characteristic of an outer shelf to slope environment. The qualitative and quantitative analysis of this microfauna revealed three benthic foraminiferal fossil assemblages and the occurrence of allochthonous species transported into the bathyal environment by current activity. The cyclical pattern of the benthic foraminifera assemblages indicates that the studied sediments have been affected by repeated episodes of basin restriction characterized by low diversity benthic foraminifera populations, and a limited planktonic foraminifer association typified by shallow, surface-dwelling forms. This restriction was partly due to Antarctic cooling, which produced palaeo-Mediterranean sea-level oscillations during the Early Messinian, as a prelude to closure of the Atlantic connections. The relative impact of climatic versus tectonic control on sedimentation patterns within this basin is discussed.  相似文献   

18.
A palynological study was carried out on four Italian Miocene‐Pliocene sections ranging in age from uppermost Tortonian to Zanclean located on the Adriatic side of the North‐Central Apennines. The study documents the Mediterranean isolation, the salinity crisis (s.s), the “lago‐mare”; event and the re‐establishment of open‐marine conditions in the Mediterranean at the beginning of the Pliocene. From a climatic point of view, a transition from subtropical/warm‐temperate conditions during the Messinian to warm‐temperate/temperate conditions during the Zanclean is recorded. The presence of a lower thermic level, with respect to the Messinian, the re‐establishment of open‐marine conditions and the uplift of the Apennines were major factors controlling paleoenvironmental variations during the Zanclean. The latter is also characterized by cyclic temperature oscillations. Correlations with coeval sections in the Mediterranean area confirm the existence of latitudinal climatic gradients within the studied area.  相似文献   

19.
An incomplete mandible of a fossil sperm whale (Odontoceti; Physeteridae) is described. It is a portion of elongated and narrow symphysis with cylindrical and slightly curved teeth without enamel. The specimen, collected from the Miocene “Pietra leccese” sediments of South Italy, appears to represent a species of Orycterocetus, and is the first such record from the Mediterranean. Considering the wide diffusion of Orycterocetus in the North Atlantic, we believe its rare presence in the Mediterranean as occasional and due to a certain degree of interchange between the Mediterranean and the North Atlantic cetacean fauna during the Miocene.  相似文献   

20.
The study of the Late Eocene (Priabonian) otolith associations from Possagno, North-East Italy, and from the Synclinal d’Allons in Haute Provence, South-East France, allows for the reconstruction of a teleost fauna of 55 taxa, which is the most diversified assemblage presently known from the Upper Eocene Paleo-Mediterranean basin. Thirty-six taxa are identified at the species level, and five of those are new: “genus Alepocephalidarum” astrictus, “genus Lophiiformorum” canovae, “genus Agonidarum” sudans, “genus Uranoscopidarum” cochlearis and Aseraggodes laganum. In the Synclinal d’Allons, the otolith associations reflect a tropical to subtropical neritic environment with a few mesopelagic fishes. At Possagno, the associations indicate an environment that changed from one that was deep and exposed to the pelagic realm and then evolved to a more shallow sea with a well-diversified benthic life and less mesopelagic fishes. A paleobiogeographical analysis of all known data on Priabonian otoliths, worldwide, shows clearly a western Atlantic (Louisiana) and an eastern Atlantic-Paleomediterranean association. In the eastern Atlantic-Paleomediterranean association, the Aquitaine association not only differs from the Possagno-Allons association in function of its more distant geographical position, but also by its stronger oceanic character in the southern part of the basin, and by the occurrence in the north, of a very shallow water facies (Saint-Estephe Formation) that contains some taxa which are known nowhere else in the Priabonian. The Ukraine fauna is characterized by a high number of species, which have an Oligocene record in other European sites. The northern geographic location of Ukraine, combined with the good connections to both the North Sea Basin and the Turgai street can provide the explanation. Many Oligocene species (or their close relatives) probably already existed at Eocene times in more northern regions, but could penetrate only in more southern European seas since the strong cooling at the beginning of the Oligocene.  相似文献   

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