Calcareous nannofossil biostratigraphy of the Paleocene sediments of the Odessa Gas Field (NW Black Sea)

Calcareous nannofossils from Paleocene sediments of two boreholes (Odeska-6 and 20) from the north-western shelf of the Black Sea are examined. Five nannofossil Zones are identified according to the standard zonations of Martini (1971) and Quillévéré et al. (2002): the Chiasmolithus danicus Zone (NP3), the upper part of Ellipsolithus Macellus Zone (NP4b), the Fasciculithus tympaniformis Zone (NP5), the Heliolithus kleinpelli Zone (NP6) and the Heliolithus riedelii Zone (NP8). This biostratigraphical work allows us to correlate the Bilokamian and Kachian regional stages of the Stratigraphic Scheme of Southern Ukraine (Zernetskiy et al., 1993) to the standard nannofossil zonations and, therefore, to the International Chronostratigraphic scheme. The presence of an unconformity between the Bilokamian and Kachian regional stages in the borehole section of Odeska-6 is suggested by Linear Sedimentary Rates estimated for the two boreholes. This unconformity corresponds to the upper part of the Chiasmolithus danicus nannofossil Zone (NP3) and the lower part of Ellipsolithus Macellus (NP4a), and is estimated to last nearly 1.94 Ma.     

Reproducibility and reliability of the Pliensbachian calcareous nannofossil biohorizons from the Basque-Cantabrian Basin (Northern Spain)

Based on calcareous nannofossil assemblages identified in four expanded and well-dated sections from the Basque-Cantabrian Basin, the main objective of this paper is to improve the knowledge of the Pliensbachian calcareous nannofossil events, and to calibrate these events to the ammonite zones established for this area. The semiquantitative analysis of more than 140 smear slides from the Tudanca and Santotis sections, and the re-analysis of more than 200 smear slides from the Camino and San Andrés sections, have been carried out in order to describe the succession of calcareous nannofossil assemblages. Related to their composition changes, we have recognized and calibrated to the ammonite zones two main events: the first occurrences (FOs) of Similiscutum cruciulus and Lotharingius hauffii, and six secondary events: the FOs of Biscutum novum, Biscutum grande, Biscutum finchii, Lotharingius barozii and the FCOs (first common occurrences) of Calcivascularis jansae and L. hauffii. In the Camino and San Andrés sections, we also identify the FOs of Biscutum dubium, Bussonius prinsii and Lotharingius sigillatus. The obtained data allow us to assess the degree of reproducibility of the Pliensbachian calcareous nannofossil events in the studied area. The biohorizon succession recognized in the Basque-Cantabrian Basin are compared to those proposed for NW Europe, Lusitanian Basin, Italy and Southern France.     

Calcareous nannofossil biostratigraphy (Upper Bajocian-Lower Bathonian) of the Ravin du Bès section (Bas Auran, Subalpine Basin, SE France): Evolutionary trends of Watznaueria barnesiae and new findings of “Rucinolithus” morphotypes

A biostratigraphic study based on calcareous nannofossils was performed on the Ravin du Bès section (Bas Auran area, SE France). Semi-quantitative estimates of total nannofossil and single species abundances showed that calcareous nannofloras are rare to common and their preservation is poor to moderate. The following biohorizons were identified and calibrated to ammonite biozonation: the first occurrence (FO) of Watznaueria aff. W. communis, the FO of Pseudoconus enigma; the FO of “Rucinolithus”; the last occurrence (LO) of Carinolithus magharensis; the FO of Stephanolithion speciosum octum and the FO of Watznaueria barnesiae. These results confirm that calcareous nannofossils are good biostratigraphic markers for the Bajocian/Bathonian boundary interval. Moreover, the occurrence of P. enigma allows a direct calibration between Tethyan and Boreal nannofossil events and biozones. Morphometric analyses were performed on the W. communis-W. barnesiae group in order to quantify changes between the two taxa. The intermediate form W. aff. W. communis has been identified; it comprises coccoliths very similar to W. communis, but with central area length ≤ 0.9 μm. This study allowed the detailed reconstruction of the evolutionary trends from W. communis to W. barnesiae: the intermediate taxon W. aff. W. communis appears abruptly in the latest Bajocian and persists after the FO of W. barnesiae in the earliest Bathonian. Our results support the model of punctuated equilibrium rather than a phyletic gradualism. The finding of “Rucinolithus” morphotypes, very similar to the Cretaceous taxa R. terebrodentarius and R. terebrodentarius youngii, is intriguing. They might represent nannoliths strongly affected by a recurrent “Lazarus effect” or be diagenetic artifacts or of bacterial bioprecipitation.     

Refinements of calcareous nannofossil biostratigraphy at the Miocene/Pliocene Boundary in the Mediterranean region

The high-resolution quantitative study of the calcareous nannofossil assemblages in two Mediterranean deep-sea successions (ODP Sites 969B and 975B) encompassing the Miocene/Pliocene boundary allows the recognition of a set of reliable bioevents useful to detecting the base of the Zanclean stage. The results have been successfully compared with two on-land sections (Cava Serredi, Tuscany, and Montepetra borehole, Marche Region, Central Italy). This study confirms that Ceratolithus acutus and Triquetrorhabdulus rugosus, the markers traditionally used for identifying the Miocene/Pliocene Boundary are very rare in the Mediterranean area and cannot be used for biostratigraphic correlation. Conversely, the absence interval (paracme) of Reticulofenestra pseudoumbilicus and the distribution range of a new species belonging to the Reticulofenestra genus (Reticulofenestra zancleana nov. sp.) show high biostratigraphical potential. The position of the new biohorizons has been compared to those of the planktonic foraminifers events, and correlated to the CaCO₃ cycles reconstructed for the two sections. On the basis of these new nannofossil bioevents, Rio et al.’s (1990) MNN12 biozone is subdivided into three subzones, thus improving the biostratigraphic resolution of the Early Pliocene.     

Integrated quantitative biostratigraphy of the latest Tortonian-early Messinian Pissouri section (Cyprus): An evaluation of calcareous plankton bioevents

A quantitative study was performed on planktonic foraminifera and calcareous nannofossils of the astronomically dated Late Miocene Pissouri section (Cyprus). Our results confirm the reliability of well-known planktonic foraminiferal events as Catapsydraxparvulus LO (Last Occurrence), sinistral coiling change of Globorotaliascitula, Globorotaliamiotumida group FRO (First Regular Occurrence), Globorotalianicolae FO (First occurrence) and LO, sinistral coiling change of Neogloboquadrinaacostaensis and also of several important calcareous nannofossil events (Amaurolithusprimus FO, Amaurolithusdelicatus FO, Reticulofenestrarotaria FO and FCO). Integrated planktonic foraminifera and calcareous nannoplankton data contribute to an enhanced time resolution of the Tortonian - early Messinian interval in the Levantine basin, and contribute to detailed correlations throughout the Eastern Mediterranean. In addition, we compare methodologies commonly used in calcareous plankton biostratigraphy, and shortly outline sources of bias that can influence the results of stratigraphic studies.     

Depositional sequences in the Kimmeridgian of the Vocontian Basin (France) controlled by carbonate export from shallow-water platforms

Detailed sedimentological analyses and sequential and cyclostratigraphic interpretations in the Kimmeridgian of the Swiss Jura and the Vocontian Basin lead to a high-resolution correlation from the platform to the basin where the biostratigraphy is well established. Several orders of depositional sequences are defined. Their duration is estimated from the time frame given in the sequence-chronostratigraphic chart of Hardenbol et al. (1998). It is suggested that an elementary sequence formed in tune with the 20 ky precession cycle. Small-scale and medium-scale sequences correspond to the 100 and 400 ky eccentricity cycles, respectively. The platform-to-basin correlation shows that the composition of the hemipelagic and pelagic deposits depends to a large part on cyclical variations of carbonate production in shallow-marine environments and subsequent export to the basin. The distribution of thick versus thin marl-limestone alternations and carbonate-dominated versus marl-dominated intervals observed in the basinal sections is explained by the superposition of high- and low-frequency sea-level changes that controlled the carbonate productivity on the platform and the export potential of carbonate mud to the basin.     

The Radiolarian biotic response during OAE2. A high-resolution study across the Bonarelli level at Bottaccione (Gubbio, Italy)

In order to improve our understanding of the radiolarian biotic response and the palaeoceanographic changes associated with the Late Cenomanian oceanic anoxic event (OAE2), a high-resolution radiolarian study was carried out across the Bonarelli level at its typical locality (Bottaccione section, central Italy). Our results confirm that a drastic radiolarian faunal change took place during the OAE2. The radiolarian turnover took place within the median part of the Bonarelli level, associated with an interval of high organic matter preservation, but relatively low values of silica. Therefore, this part constitutes a critical period in the evolutionary history of Radiolaria. A synthesis of all data available in the Umbria-Marche basin suggests that the lower part of the Bonarelli level (and underlying limestones) records mainly radiolarian extinctions (ca. 41%), while its upper part (and overlying limestones) records mainly first occurrences (ca. 35%). Our results improve understanding of the paleoecology of the family Saturnalidae, which would seem to prefer oligotrophic environments.     

The regional record of Albian oceanic anoxic events at the Apulian Platform Margin (Gargano Promontory, southern Italy)

The Gargano Promontory, located on the eastern margin of the Apulia Platform, represents a distinctive Tethyan area where the transition from carbonate platform to adjacent basin is exposed on land. The Albian stratigraphic record, represented by shallow-water, slope and deep-water deposits, provides a good opportunity to investigate the regional response to oceanic anoxic events (OAEs) in different depositional settings by using an integrated, high-resolution micropalaeontological (planktonic foraminifers and calcareous nannofossils) approach. Results show that organic matter preservation is confined to the more distal areas (Marne a Fucoidi Formation), and consists of black shale intervals from the middle and late Albian (Ticinella primula/Prediscosphaera columnata Zones; upper Ticinella praeticinensis Subzone/R. achlyostaurion Zone, respectively). Integrated biostratigraphic data correlate the intervals of black shale deposition to the Urbino and Amadeus levels, previously identified and named in the Umbria-Marche Basin. These black shales record the effects of OAEs 1b and 1c. The biotic changes in the pelagic Albian succession of the Apulian Platform Margin provide evidence for episodes of eutrophication that correlate to the deposition of these black shales. Genetic models for the two episodes of organic matter preservation are proposed, taking into account both global and local controlling factors.     

Bioturbational redistribution of Danian calcareous nannofossils in the uppermost Maastrichtian across the K-Pg boundary at Bidart, SW France

In this paper we present the effects of different tracemakers on the redistribution of calcareous nannofossils throughout the K-Pg boundary at the Bidart section (SW France), along with their consequences for our knowledge of the K-Pg boundary event. Danian calcareous nannofossil assemblages are present in Maastrichtian samples due to infiltration into dark trace fossil infillings proceeding from the earliest Paleogene. This is evidenced by the appearance of abundant paleogene calcareous nannofossils just below the K-Pg boundary, showing the relevance of the trace fossil infillings in the context of the K-Pg boundary event.     

Calcareous nannofossils and foraminifers herald the Messinian Salinity Crisis: The Pollenzo section (Alba, Cuneo; NW Italy)

During the Messinian, the Mediterranean area experienced fast and prominent paleoenvironmental changes, culminating in the so-called Messinian Salinity Crisis, with the deposition of the evaporitic series. This work investigates the micropaleontological assemblages in the pre-evaporitic sediments of the Sant’Agata Fossili Marls (SAF) of the Pollenzo section (Cuneo area, North Western Italy). A semiquantitative analysis is carried out on the upper part of the marly and pelitic sediments of the SAF underlying the first gypsum bed, ascribed to the Vena del Gesso Fm. (VDF). The studied interval belongs to the planktonic foraminifer Globorotalia conomiozea Zone and “non distinctive Zone” of Iaccarino and to the calcareous nannofossil MNN11b/c Zone of Raffi et al. (1998, 2003) ( [Raffi et al., 1998] and [Raffi et al., 2003]). Decrease of diversity and abundance of the foraminifer and calcareous nannofossil assemblages is recorded 12 m below the VDG and clearly reflects environmental stress. From bottom to top, six paleoecological events are recorded: (1) the first peak abundance of “small” Reticulofenestra and the last recovery (LR) of planktonic foraminifers; (2) the peak abundance of Pontosphaera japonica and the last recovery of warm water taxa Discoaster spp.; (3) the last recovery of benthic foraminifers; (4) the co-occurring peak abundances of Helicosphaera carteri and Sphenolithus abies, and the last recovery of warm water taxa Amaurolithus spp.; (5) the second peak of “small” Reticulofenestra; (6) the definitive disappearance of calcareous nannofossils. These paleoecological events describe a progressive isolation of the basin from the world ocean and increasingly stressed environment (LR planktonic foraminifers; LR Discoaster spp.), increasing dysoxic to anoxic conditions at the sea floor (LR benthic foraminifers), shallowing of the water column (peak of H. carteri), increasing salinity in surface waters (peak of S. abies), and enhanced nutrient concentration in surface waters (peak of “small” Reticulofenestra); these are related to paleoenvironmental changes predating gypsum deposition at Pollenzo and affecting the whole Mediterranean basin.     

Palaeoceanographic differences of early Late Aptian black shale events in the Vocontian Basin (SE France)

A high-resolution study focussing on the distribution of calcareous nannofossils and carbon isotopes was carried out to improve the understanding of mid-Cretaceous black shale formation. The studied interval of the early Late Aptian is characterized by two major black shale couplets, the Niveau Noire 4 (NN4) and Niveau Noire Calcaire 2 (NNC2), of the Serre Chaitieu section in the Vocontian Basin (SE France; Bréhéret, 1997). This interval occurs within a long-term negative carbon isotope excursion of > 1.5‰ following the Early Aptian Oceanic Anoxic Event 1a (OAE1a). In contrast to the local NN4 black shales, the black shales of NNC2 are of regional significance and occur at the end of the major negative carbon isotope excursion of the early Late Aptian. Time equivalent black shales are suggested to be coeval with black shales found in the Western Tethys and Atlantic Ocean (Herrle et al., 2004). Calcareous nannofossil analyses and carbon isotopes indicate higher surface water productivity (mesotrophic), warmer surface water, and higher sea-level during the formation of the NN4 black shales. In contrast, the formation of the NNC2 black shales took place during a cooler phase, lower surface water productivity, and lower sea-level. A sea-level fall may cause a restriction of water mass exchange between the open-marine Western Tethys and the Vocontian Basin. This resulted in a longer residence time of the bottom water, decreased ventilation and less mixing of surface waters and thus enhanced preservation of organic matter at the sea floor. Our results indicate that the black shale formation of NN4 and NNC2 was caused by different processes such as increased surface water productivity and enhanced preservation of organic matter at the sea floor. Thus, we emphasize the role of different forcing factors which control the formation of local and regional black shales. The most important factors are sea-level fluctuations, increasing productivity, and changes in precipitation and evaporation rates.     

Coral-rudist bioconstructions in the Upper Cretaceous Haidach section (Gosau Group; Northern Calcareous Alps, Austria)

Summary In the area of Haidach (Northern Calcareous Alps, Austria), coral-rudist mounds, rudist biostromes, and bioclastic limestones and marls constitute an Upper Cretaceous shelf succession approximately 100 meters thick. The succession is part of the mixed siliciclasticcarbonate Gosau Group that was deposited at the northern margin of the Austroalpine microplate. In its lower part, the carbonate succession at Haidach comprises two stratal packages that each consists, from bottom to top, of a coral-rudist mound capped by a rudist biostrome which, in turn, is overlain by bioclastic limestones and, locally, marls. The coral-rudist mounds consist mainly of floatstones. The coral assemblage is dominated by Fungiina, Astreoina, Heterocoeniina andAgathelia asperella (stylinina). From the rudists, elevators (Vaccinites spp., radiolitids) and recumbents (Plagioptychus) are present. Calcareous sponges, sclerosponges, and octocorals are subordinate. The elevator rudists commonly are small; they settled on branched corals, coral heads, on rudists, and on biolastic debris. The rudists, in turn, provided settlement sites for corals. Predominantly plocoid and thamnasteroid coral growth forms indicate soft substrata and high sedimentation rates. The mounds were episodically smothered by carbonate mud. Many corals and rudists are coated by thick and diverse encrustations that indicate high nutrient level and/or turbid waters. The coral-rudist mounds are capped byVaccinites biostromes up to 5 m thick. The establishment of these biostromes may result from unfavourable environmental conditions for corals, coupled with the potential of the elevator rudists for effective substrate colonization. TheVaccinites biostromes are locally topped by a thin radiolitid biostrome. The biostromes, in turn, are overlain by bioclastic limestones; these are arranged in stratal packages that were deposited from carbonate sand bodies. Approximately midsection, an interval of marls with abundantPhelopteria is present. These marls were deposited in a quiet lagoonal area where meadows of sea grass or algae, coupled with an elevated nutrient level, triggered the mass occurrence ofPhelopteria. The upper part of the Haidach section consists of stratal packages that each is composed of a rudist biostrome overlain by bioclastic wackestones to packstones with diverse smaller benthic foraminifera and calcareous green algae. The biostromes are either built by radiolitids,Vaccinites, andPleurocora, or consist exclusively of radiolitids (mainlyRadiolites). Both the biostromes and the bioclastic limestones were deposited in a low-energy lagoonal environment that was punctuated by high-energy events.In situ-rudist fabrics typically have a matrix of mudstone to rudistclastic wackestone; other biogens (incl. smaller benthic foraminifera) are absent or very rare. The matrix of rudist fabrics that indicate episodic destruction by high-energy events contain a fossil assemblage similar to the vertically associated bioclastic limestones. Substrata colonized by rudists thus were unfavourable at least for smaller benthic foraminifera. The described succession was deposited on a gently inclined shelf segment, where coral-rudist mounds and hippuritid biostromes were separated by a belt of bioclastic sand bodies from a lagoon with radiolitid biostromes. The mounds document that corals and Late Cretaceous elevator rudists may co-occur in close association. On the scale of the entire succession, however, mainly as a result of the wide ecologic range of the rudists relative to corals, the coral-dominated mounds and the rudist biostromes are vertically separated.     

Biostratigraphical precisions on the Early Serpukhovian (Late Mississippian), by means of a carbonate algal microflora (cyanobacteria, algae and pseudo-algae) from La Serre (Montagne Noire, France)

The microbial-dominated part of a Late Mississippian (Early Carboniferous) carbonate olistolite at La Serre (Montagne Noire, southern France) yielded interesting algae and pseudo-algae. The constituents are well known cyanobacteria (not described) and different representatives of poorly known or new species: cyanobacteria: Aphralysia capriorae, Hedstroemia (?) serrana n. sp., Dasycladales: Paraepimastopora sp., Nanopora sp., Cabrieropora pokornyi and E. occitanica, Anatoliporaceae: Richella incrustata, Caulerpales: Poncetellina (?) sp., questionable Archaeolithophyllaceae: Hortonella sp., Archaeolithophyllaceae: Neoprincipia with Neopricipia fluegeli, Neoprincipia petschoriaeformis n. sp., Neoprincipia claviformis n. sp. and Archaeolithophyllum ex gr. lamellosum; pseudo-algae Aoujgaliida: Stacheoidella spissa, Ungdarella uralica, and Fasciellidae: Fasciella and Praedonezella, with both polymorph species: Fasciella kizilia, and Praedonezella ex gr. cespeformis. This carbonate microflora is dated as Early Serpukhovian (Pendleian) by its association with the foraminifera Janichewskina, “Biseriella” and “Warnantella”. This dating is confirmed by the little more advanced algal assemblage, compared to the Latest Visean (Brigantian) assemblages from Montagne Noire (e.g. Japhet, Castelsec), and more primitive than the Late Serpukhovian (Arnsbergian) of Ardengost (Pyrenees). The importance of the calcifoliid pseudo-algae—Fasciella, Praedonezella, and Calcifolium (although this latter is locally lacking)—is suggested for the biozonation of the Visean/Serpukhovian boundary.     

Sedimentary response to basin inversion: Mid cretaceous-early tertiary pre- to syndeformational deposition at the Areif El Naqa anticline (Sinai, Egypt)

Summary The Areif El Naqa domal anticline in northeastern Sinai is part of the ‘Syrian Arc’ which represents an intraplate orogen that has been formed since the late Cretaceous by inversion of an older half-gaben system as a consequence of the collision of the African and Eurasian plates. The here studied pre- and syn-deformational Upper Albian to Lower Eocene sedimentary succession in the anticline was formed under shallow marine to hemipelagic conditions resulting in predominantly carbonate lithologies with only subordinate siliciclastic intercalations. The depositional history at Areif El Naqa has been reconstructed in terms of sequence stratigraphy on the basis of detailed sedimentological, biostratigraphical, and paleoecological investigations of ten sections including comparisons with age-equivalent successions further north and south as well as published data. Following a late Triassic-early Cretaceous extensional period, tectonically rather quiet conditions prevailed during deposition of the Albian-Turonian successions. Inversion started around the Coniacian. Three main phases of uplift have been determined for the Areif El Naqa anticline on the basis of evidence from lateral facies and thickness changes, local development of pronounced hiatuses, and in comparison to the sequence stratigraphic development in the tectonically quiet region of central east Sinai. The first major compressional phase is interpreted to have taken place in Coniacian-early Santonian times. It is characterized by pronounced facies and thickness changes which were documented in an earlier study byBartov et al. (1980). Nevertheless, inter-regional sea level changes still controlled deposition at Areif El Naqa during this period. The second pulse of tectonic uplift is indicated for the late Campanian-early Maastrichtian. This is based on siliciclastic deposits which are interpreted as having been reworked from older siliciclastic rocks uplifted in the anticlinal core. The third compressional pulse is inferred to be of middle Paleocene to early Eocene age as evidenced by a major hiatus in sections on the northern anticlinal flank. The uplift history at Areif El Naqa has been compared with the tectonic development in other parts of the Syrian Arc and in general seems to reflect major movements which occurred throughout the anticlines of the fold belt.     

An early cretaceous section in the Kircaova area (Berdiga Limestone,NE-Turkey) and its correlation with platform carbonates in W-Slovenia

Summary In the Kale (Gümüshane) area in the North Eastern Turkey, platform carbonates of the Berdiga Limestone were deposited during Late Jurassic-Early Cretaceous time in environments varying from intertidal to fore reef. The sequence shows extensive lateral and vertical alterations and interfingering of different facies types. In the upper part of the Berdiga Limestone in the Kircaova area a bituminous thin-bedded to platy limestone and shale 5 to 6 m thick occurs at the Early/Late Aptian boundary. It is underlain by limestones rich in silica nodules of up to 10 cm size. A facies analysis of a section about 70 m thick including the bituminous interval was carried out in 1994/95 at the SW border of the Kircaova area close to the road from L?rikas to Kale. The limestones consist mainly of packstones and grainstones locally rich in calcareaous algae and forminifera. Fragments of molluscs and echinoids as well as some ostracods and calcispheres occur. Some sponges, corals, and beds rich in molluscs occur in minor amounts in the middle part of the section which is characterized by intertidal to shallow subtidal facies. Algae and foraminifera indicate a Barremian-Early Aptian age of the lower part and Late Aptian age of the upper part of the section (e.g.Salpingoporellamuehlbergii, Salpingoporella aff.melitae, Clypeina solkani, Novalesia producta), divided by the bituminous limestones. In West Slovenia (close to the Italian border) a complete Cretaceous section occurs at Sabotin mountain containing Aptian beds with comparable faunal composition. In contrast to the Berdiga Limestone, in Slovenia at the rim of the dinaric platform a patch reef about 50 m in thickness is developed which is also covered by a bituminous limestones (black shale) marking the Early/Late Aptian boundary. Faunal elements in Slovenia arePalorbitolina lenticularis, Cuneolina laurentii, Orbitolina (Mesorbitolina) texana andSalpingopoprella dinarica. The bituminous limestone appears to be a marker horizon. At both locations it is locally rich in characeans probably indicating a regressive maximum before another transgression began in the Late Aptian/Albian as world-wide drowning event. Possibly the occurrence of the bituminous limestone (black shale) is associated with volcanic activity during the Aptian. If so it could be used as a chronostratigraphic marker horizon in both areas analyzed.     

Coral-microbialite reefs in pure carbonate versus mixed carbonate-siliciclastic depositional environments: the example of the Pagny-sur-Meuse section (Upper Jurassic,northeastern France)

Middle to Upper Oxfordian reefs of a shallow marine carbonate platform located in northeastern France show important facies changes in conjunction with terrigeneous contents. The Pagny-sur-Meuse section shows coral-microbialite reefs that developed both in pure carbonate limestones and in mixed carbonate-siliciclastic deposits. Phototrophic coral associations dominated in pure carbonate environments, whereas a mixed phototrophic/heterotrophic coral fauna occurred in more siliciclastic settings. Microbialites occur in pure carbonate facies but are more abundant in mixed carbonate-siliciclastic settings. Reefs seem to have lived through periods favourable for intense coral growth that was contemporaneous with a first microbialitic layer and periods more favourable for large microbialitic development (second microbialitic layer). The first microbialitic crust probably developed within the reef body and thus appears to be controlled by autogenic factors. The second generation of microbialites tended to develop over the entire reef surface and was probably mainly controlled by allogenic factors. Variations in terrigeneous input and nutrient content, rather related to climatic conditions than to water depth and accumulation rate, were major factors controlling development of reefs and their taxonomic composition.     

Biostratigraphy and sedimentary evolution of Late Miocene and Pliocene continental deposits of the Granada Basin (southern Spain)

The Late Miocene and Pliocene continental sediments in the Granada Basin (southern Spain) have yielded large amounts of fossil small mammals in 37 localities from 11 sections. The aim of this paper is to integrate faunistic, stratigraphic, and sedimentary criteria to unravel the geological history of the continental infilling of the basin. The palaeontological study has led to a detailed biozonation on the basis of rodents, which helps to correlate in detail the different sedimentary units found in the basin, and to follow the changes of the different sedimentary systems and their palaeogeographical evolution through time. Combination of the proposed biostratigraphy and the reinterpretation of the magnetostratigraphic analyses of the Barranco del Purcal section allows us to assign an absolute age slightly older than 5.23 Ma to the Turolian–Ruscinian boundary (MN13‐MN14).     

The marine paleogene of the tremp region (NE Spain)-depositional sequences,facies history,biostratigraphy and controlling factors

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.     

Evolutionary patterns in the terebratulid genus Caryona Cooper (Brachiopoda,Jurassic of France)

The study of ontogenetic and morphological changes in different species of the brachiopod genus Caryona COOPER (Terebratulidae) from the Lower Callovian‐Lower Oxfordian of northern France shows a succession (and an interference) of processes which vary according to the characters studied. This is an example of “mosaic evolution”;. The ontogenetic changes result from heterochrony, especially acceleration and hypermorphism. The main phylogenetic tendency is peramorphosis in most characters. This evolutionary pattern agrees with phyletic gradualism.

Moreover, analysis of the internal characters demonstrates the limited value of these in discrimination of the various genera.     

Late Pleistocene small mammals from the Wannenköpfe volcanoes (Neuwied Basin, western Germany) with remarks on the stratigraphic range of Arvicola terrestris

Redeposited loess sediments from a Pleistocene crater filling in the Neuwied Basin (western Germany) yielded a small mammal fauna mainly composed of arvicoline rodents. The occurrence of rare faunal elements such as Sorex minutissimus, Sicista subtilis, and a species of Microtus (Terricola) is remarkable. Based on the evolutionary level of Arvicola terrestris, the biostratigraphic age of the fossiliferous horizon is transitional between late Eemian and early Weichselian. This conclusion is partly supported by the generalized ecological requirements of a few dominant rodent species. The fauna contributes to the knowledge of this time period, which is poorly documented in western Germany. A new character of the m1 is proposed for the discrimination of Sicista betulina and S. subtilis. To avoid further confusion in the specific assignment of transitional Arvicola specimens from the late Middle Pleistocene to early Late Pleistocene, we propose the formal taxonomic boundary between chronospecies A. mosbachensis and A. terrestris to be shifted from SDQ value 100 to SDQ value 120.