The Miocene vertebrate-bearing deposits of Scontrone (Abruzzo,Central Italy): Stratigraphic and paleoenvironmental analysis

The Miocene carbonate deposits of Scontrone (Abruzzo, Central Italy) are well known among palaeontologists because of their fossil vertebrate content that exhibits striking similarities to those of the remarkable “Terre Rosse” faunal complex of the Gargano region, defining the existence of the Miocene Central Mediterranean Apulia paleobioprovince. The main goal of this paper is to establish the age and environment of the Scontrone vertebrate bonebeds. The vertebrate remains are embedded in the basal portion of the Lithothamnion Limestone, a widespread carbonate-ramp lithosome representative of the Tortonian-early Messinian transgression over the entire Apulia Platform. The bonebeds belong to marginal-marine deposits (here called “Scontrone calcarenites”) preserved in a small area below transgressive ravinement surfaces. The rapid vertical and lateral facies variations displayed by the “Scontrone calcarenites”, together with paleoenvironmental considerations deriving from the vertebrate association, document a complex wave-dominated river-mouth depositional setting developed over a large, flat and semi-arid carbonate ramp. The “Scontrone calcarenites” have been split herein into five facies associations representing the stratigraphic response to a discontinuous or punctuated transgression within an overall rise of the relative sea level. Because of the absence of age-diagnostic fossils, the age of the “Scontrone calcarenites” cannot be directly defined through their paleontological content. However, a regional stratigraphic correlation between the Lithothamnion Limestone of Scontrone and the Lithothamnion Limestone of northern Majella, which is biostratigraphically well constrained, allows the attribution of the “Scontrone calcarenites” to the Tortonian.     

Biostratigraphie d’après les foraminifères et paléoenvironnements des séries post-Éocène du sondage ASHTART 28, golfe de Gabès (Tunisie)

The Cenozoic sequence of Ashtart 28 well drilled in the Gulf of Gabes (Tunisia) is the subject of a biostratigraphical study. The samples recovered in cuttings from 390 m and downwards allowed to recognize, above the Late Eocene sediments, a sedimentary series, lithologically diversified, nearly 1600 m thick. Marine Pliocene deposits, generally attesting a low bathymetry, lie unconformably above the Messinian (Oued Bel Khedim formation), which shows the usual features of the Mediterranean confinement. The underlying Messinian pre-evaporitic platform series (Melqart formation), that is over 250 m thick, is typical of a perireefal environment. The sediments assigned to the Tortonian (Somâa Sands formation) are continental and occur unconformably above the approximately 500-metres-thick Middle Miocene strata (Saouaf, Mahmoud, Aïn Grab and Salammbô pars formations). The marine Lower Miocene and Oligocene sediments (Salammbô pars and Ketatna formations), that are more than 300 m thick, lie in continuity under the Middle Miocene. The infralittoral Chattian sequence has especially supplied a diversified assemblage of larger foraminifera recovered in other west-mediterranean basins. Datings were obtained based on planktonic and larger benthic foraminifera (Miogypsinidae, Nummulitidae, Lepidocyclinidae) and by correlations obtained by means of well loggings and lithostratigraphy. Benthic foraminifera, mainly listed for the Miocene and Oligocene, are studied from a systematic, stratigraphic and paleogeographic point of view. The paleoenvironments of deposits are defined for each considered stratigraphic interval. Comparisons are sketched with other drillings of the Gulf of Gabes. Thanks to the numerous data obtained by this detailed study, the Ashtart drilling can serve as a reference for the Tertiary sequence of this part of the Mediterranean domain.     

Foraminifères benthiques complexes du Bathonien supérieur au Kimméridgien inférieur de la marge atlantique marocaine (« Bassin » d’Agadir) : stratigraphie et paléobiogéographie

The carbonate sediments of the Agadir Basin (Morocco) deposited during the Upper Bathonian-Lower Kimmeridgian p.p. interval are rich in agglutinated complex benthic foraminifera. The detailed inventory of several field-sections allows to identify and to describe these benthonic foraminifera, some of them being recorded for the first time in Morocco. They belong to the main genera Archaeosepta, Andersenolina, Praekurnubia, Pseudocyclammina, Everticyclammina, Alveosepta, Kurnubia, Parurgonina, Neokilianina, Labyrinthina and Rectocyclammina. The stratigraphic and paleobiogeographic distribution of these foraminifera seem to be related to the geodynamic events occurring on the Moroccan Atlantic margin during this time-interval. The stratigraphic distribution of the principal species is generally controlled by the occurrence of ammonites, brachiopods and of some foraminifera which are considered as good stratigraphic markers.     

Le site de Longgupo dans son environnement géologique et géomorphologique

On a regional scale, Longgupo is found within a karstic landscape of fenglin-ouvala developed in the Triassic limestones of the Yangtze platform. After several seasons, it is now possible to define and propose a scenario for the formation of the site. During one of the intense karstification phases during the Cretaceous or early Tertiary, karstic conduits were created deep in the substratum. In concert with these deep flows and by karstic collapse, a cave was created. With the start of Himalayan uplift during the Oligocene and Miocene, the beginning of fluvial cutting was reflected by the partial erosion of the upper sandstone formations and the creation of the Miaoyu Valley. This action opened the cave, which would later be occupied by the hominid groups that interest us here. Probably at the end of the Tertiary, the cave, open at the bottom of the valley slope and facing upstream, began to be filled with alluvial deposits from the valley. The basal deposits (C III 10 of the current stratigraphic sequence, levels 20-13 of the first sequence) begin with black clays; at the Plio-Pleistocene transition, deposits become clearly alluvial, increasingly marked by reworking of surface and karstic clays and by systematically coarser contributions. During the deposition period of archaeological complexes III/III’ (previously levels 12-6), karstic collapse appears to have still been active. During the Lower Pleistocene sensu lato, the coarse nature of the deposits becomes accentuated. The material of complex II (previously levels 5-2) is a deposit that is clearly heterometric and coarse, composed at the end mainly of gravels, pebbles and more or less rounded blocks in a clayey matrix. At the conclusion of this new stage, the cave was entirely filled and, purely and simply, disappeared from the landscape. As the valley deepened during the Middle and Upper Pleistocene, the Longgupo slope underwent profound changes, the last of the limestone blocks disappeared from the slope limit and the archaeological site was protected by the coarse breccias that carpeted the slope. The main cause for the sedimentation processes at the site of Longgupo is the hydrosystem of the Miaoyu he, although injections of karstic type sensu stricto cannot be excluded. All of the arguments effectively support alluvial deposition: pebbles, an alternation of coarse and clayey beds, systematic and repeated granulometric decrease. But the stratigraphic disposition was disturbed by deformations due to gravity and karstic origins; the alluvial sediments, rendered plastic by the high proportion of clayey beds, were deformed by gravity (deformation of beds, faults, slopes) following the direction of the slope and by karstic collapse along the two limestone walls north and south of the sites (in sub-parallel faults to the south and by circular aspiration to the north). To this is added a calcitic consolidation of the upper levels that made it difficult to excavate complex C II. The stratigraphic disposition of the archaeological levels at Longgupo is now well understood. It has thus been possible to collect samples for absolute dating, to be published soon.     

Proposition d’un référentiel taphonomique fossile de faunes issues d’avens-pièges

Pitfalls are formations characterized by a vertical opening that connects the karstic system to the outside. The presence of faunas trapped without the intervention of man or carnivores, offers the opportunity to establish a fossil referential of modifications generated by identified taphonomic agents. Three natural deposits containing large faunal accumulations feed this work. Their characteristics differ. The Igue des Rameaux, to Saint-Antonin-Noble-Val in Tarn-et-Garonne, is a pitfall which contains two accumulations of fauna independent from the Middle Pleistocene. Scavenging by man and carnivores (hyenas and wolves) are observed. The Igue du Gral, to Sauliac-sur-Célé in Lot, is a second pitfall. His principal phase of filling took place 14,000 years ago. Man did not exploit this assemblage. The activity of wolves is locally important, some animals are scavenged. The Grotte de l’Escale, in Bouches-du-Rhône, contains a very important filling of lower and middle Pleistocene. For the levels presented here, only a very weak presence of carnivores is attested. The thar (Hemitragus bonali) is the majority specie. We describe here the main forms of climato-edaphic modifications: fragmentation, dissolution, weathering and deposits observed on the osseous material. A differential analysis enables us to evaluate the variability of the situations according to the stratigraphic units and the different species. In a second time, we estimate the impact of the taphonomic agents on the differential conservation of bones and skeletal representations. Many phenomena are producing a significant correlation between anatomical representations and osseous densities. However, we find for all the species a certain homogeneity in the skeletal profiles where no precise element dominates. In a last part, we give two examples of the use of the taphonomic phenomena in the individualization of filling episodes within sometimes disrupted stratigraphies.     

From biologically to hydrodynamically controlled carbonate production by tectonically induced paleogeographic rearrangement (Middle Miocene,Pannonian Basin)

The Leitha Mountains in Austria are a chain of hills separating the southern Vienna Basin and the Danube Basin. The Lower East Alpine basement of the Leitha Mts. is covered by Middle Miocene sediments of the Badenian and Sarmatian regional stages. Close to the northeastern margin of these hills, upper Badenian successions are exposed, which are part of a coralline algal-dominated carbonate platform with hydrodynamically influenced sediments. Six sections have been logged and subjected to detailed investigation and sampling. They are characterized by inclined beds (foresets), which have been formed by unidirectional transport of sediments. Large-scale asymmetrical ripples indicate strong currents affecting shallow topset deposits. Generally, this hydrodynamically controlled sedimentation, documented by seven facies types, is reflected in a strongly reduced diversity of facies and biota, contrary to the older facies-rich middle Badenian sediments. This change from biologically to hydrodynamically controlled sedimentation led to a reduction in diversity of facies and biota. Sediment transport, however, caused secondary mass occurrences of echinoids or foraminifers derived from seagrass meadows. This study unravels the distribution and differences of middle and upper Badenian deposits of the Leitha Mountains and the influence of tectonic activity. Changes in hydrodynamics on the Leitha Platform are linked to the formation of the Danube Basin starting in the middle Badenian when a new seaway to the southeast has started to form.     

From ramp to platform: building a 3D model of depositional geometries and facies architectures in transitional carbonates in the Miocene, northern Sardinia

The depositional geometry and facies distribution of an Early Miocene (Burdigalian) carbonate system in the Perfugas Basin (NW Sardinia) comprise a well-exposed example of a transition from a ramp to a steep-flanked platform. The carbonate succession (Sedini Limestone Unit) is composed of two depositional sequences separated by a major erosional unconformity. The lower (sequence 1) records a ramp dominated by heterozoan producers and the upper (sequence 2) is dominated by photozoan producers and displays a gradual steepening of the depositional profile into a steep-flanked platform. This paper shows the process of creating a digital outcrop model including a facies model. This process consists of combining field data sets, including 17 sedimentary logs, and a spatial dataset consisting of differential global positioning system data points measured along key stratigraphic surfaces and sedimentary logs, with the goal of locking traditional field observations into a 3D spatial model. Establishing a precise geometrical framework and visualizing the overall change in the platform geometry and the related vertical and lateral facies variations of the Sedini carbonate platform, allows us to better understand the sedimentary processes leading to the geometrical turn-over of the platform. Furthermore, a detailed facies modeling helps us to gain insight into the detailed depositional dynamics. The final model reproduces faithfully the depositional geometries observed in the outcrops and helps in understanding the relationships between facies and architectural framework at the basin scale. Moreover, it provides the basis to characterize semiquantitatively regional sedimentological features and to make further reservoir and subsurface analogue studies.     

Mise en place des dépôts de pente du site moustérien de La Rouquette à Puycelci (Tarn) : étude sédimentologique et implications paléoclimatiques

La Rouquette (Puycelci, Tarn) Mousterian site sedimentological study allowed to define three large stratigraphic complexes into the Mousterian scree infilling. The granulometry, petrography, morphoscopy and clays mineralogy studies show variations that can be correlated with climatic variations, results corrobored by fauna and microfauna studies. Those sedimentary record variations are related to different sources which allow paleoclimatic interpretations and give a chronostratigraphic frame for this site.     

Variations morphologiques des Toxaster (Echinoida : Spatangoida) en regard des fluctuations spatiales (Arc de Castellane, SE France) et temporelles (Valanginien-Hauterivien) du milieu sédimentaire : expression d'un potentiel adaptatif restreint

The impact of sedimentary conditions on the settlement, growth, and morphology of primitive spatangoid sea urchins of the genus Toxaster from the Lower Cretaceous (Valanginian and Hauterivian of the Provencal platform) is analyzed. The analyses concern spatial and temporal patterns of variation. The spatial approach is based on six isochronous populations of Toxaster granosus kiliani (424 specimens in total) dated from the Verrucosum biozone, and distributed along a proximo-distal gradient. The temporal approach concerns a reference section (Carajuan) ranging from the Lower Valanginian to the Upper Hauterivian, and involving the species T. granosus kiliani and T. gibbus. Sedimentary environments have been characterized by a factorial analysis of five characteristics of facies. Sea urchin morphology has been described with seven measures allowing the computation of two angles (α and β), and of six shape indices analyzed through a principal components analyses. The spatial approach shows that the adult mean size (> 20 mm) increases distally, and that morphology changes significantly across localities. However, only variations in α and β are sequentially organized along the proximo-distal gradient (they correspond to a forward migration of the peristome and to an expansion of the plastronal area). The stratigraphic survey of facies variation along the 369 beds analyzed in Carajuan shows a clear change in sedimentary conditions: from unstable with bioclastic events (Valanginian), to homogeneous with a low content in bioclasts (Hauterivian). Most Toxaster specimens are concentrated in three stratigraphic units (Campylotoxus and Verrucosum biozones for T. granosus kiliani; Sayni biozone for T. gibbus), their abundance being related to the macrofaunal presence and diversity and to burrowing activity. The adult mean size is only significantly related to facies variation, for the T. granosus kiliani from the Verrucosum biozone, increasing with textural gradient and bioclastic content. Shape - facies relationships have been identified for T. granosus kiliani in both Campylotoxus and Verrucosum intervals. However, the morphological variables and facies characteristics involved differ between the two biozones. The synthesis of all significant relationships between size or shape and facies characteristics demonstrates that the response of Toxaster to environmental changes was limited, and varied in space as well as for the different periods of time considered. The only recurring impact of sedimentary changes involved sea urchin abundance, that is, their ability to settle. The low adaptive potential of Toxaster is discussed in the context of the early radiation of the Spatangoida.     

Late Miocene continental biota in Northeastern Patagonia (Península Valdés, Chubut, Argentina)

A new vertebrate faunal assemblage was recently discovered from the uppermost part of the late Miocene Puerto Madryn Formation. These deposits crop out along the southwestern coast of the Península Valdés area near Punta Delgada (Chubut Province, Argentina). The exhumed vertebrate fauna includes a range of fish, bird and mammal taxa, of which the latter are most varied and abundant. The new findings represent the first record of continental fossil vertebrates in the Puerto Madryn Formation and this is the first assemblage of late Miocene continental vertebrates recorded to the south of Río Negro Province. It also includes the southernmost record of Hydrochoeridae rodents, Dendrocygninae birds and Loricariidae fishes. The mammals suggest that the fossil-bearing sediments are Huayquerian in age. The climate during the accumulation of late Miocene deposits in this region is inferred to have been warmer and seasonally drier than that of today.     

Les ostracodes du Néogène supérieur du littoral nord-ouest marocain entre Tanger et Asilah

Ostracodes populations have been studied in 19 samples from the upper Neogene of the Atlantic coast of NW of Morocco, between Tangier and Asilah. One hundred and two species belonging to 53 genera have been indentified. Analysis of the species assemblages allowed to reconstruct the palaeoenvironmental evolution of these deposits. This begins with the transgression of the upper Tortonian which corresponds to a relatively deep circalittoral environment. The series continues by deposits showing a general regressive character, punctuated by few transgressives pulses. Shallowing starts at the end of the upper Tortonian with the deposition of calcarenites in massive banks, in an infralittoral exposed environment. This facies pass towards the top to a detrital facies, assigned to the Messinian and deposited under high energy conditions in a shallow-marine environment. The lower Pliocene transgression shows a more generalized character. The maximum deepening corresponds to the grey clay facies deposited in the external infralittoral environment, relatively protected and rich in phytal biotopes. The more recent deposits are shallower, from coastal environments, and show a more limited extension.     

Development of rudist lithosomes in the Coniacian–Lower Campanian carbonate shelves of central-southern Italy: high-energy vs low-energy settings

The Late Cretaceous shallow-water depositional areas of southern Tethys were complexes of unprotected shelves occupied by foramol assemblages that produced loose, diagenetically stable bioclastic debris not involved in significant in situ cementation processes. Both storm- and wind-induced currents and waves exercised a strong control on the distribution of the shifting biogenic sediments which covered the open sea-floor, constituting large coalescing sheets of winnowed fine to coarse skeletal sands. Rudists spread over all shelf sectors, from more open and external areas to more internal ones, occupying different substrata and furnishing the bulk of the skeletal component by means of bioerosion processes. They colonised mobile sediments giving rise to complex bodies with peculiar characteristics related to environmental parameters of the different sectors of the shelf. On the basis of detailed sedimentological, taphonomic and palaeontological data, we recognised two main rudist-rich depositional settings (‘end members’) in the southern Italy Senonian rudist-bearing successions. In successions pertaining to hypothesised marginal shelf sectors, characterised by high-energy regime deposits, rudist lithosomes are metric in thickness and lateral extent and lens-like in morphology, rich in bioerosion-derived skeletal sand and silt. Rudists are highly diversified. Large elongated cylindro-conical hippuritids (mostly pertaining to the genera Hippurites and Vaccinites), thick-shelled radiolitids and plagioptychids largely dominate. Rudists clustered in life position are subordinate; they often form small bouquets. More commonly these organisms appear fallen but only barely reworked. The rudist-rich bodies laterally pass into clean bioclastic grainstone in which sedimentary structures, related to current and/or storm erosional action, are common. No evidence of significant original relief of the rudist bodies in respect of the neighbouring sediment can be recognised. The submarine erosion and/or the high-energy processes operating presumably inhibited the aggradation of the tidal sediments above the marginal ones. As a consequence the vertical facies organisation shows widespread subtidal cycles, as commonly recognised in open shelves with ramp-like morphologies. In successions pertaining to more internal and/or low-energy sectors, rudist-rich beds rhythmically alternate with finer-grained foraminiferal limestones. Small elevator radiolitids with oligospecific diversity are dominant, mostly concentrated in clumps. Rudists in growth position are abundant, although a large quantity of shells appear toppled with little reworking. They may form laterally continuous biostromal shell beds. Sedimentary structures such as cross-lamination and gradation are only occasionally present. The resulting facies are commonly arranged in peritidal/shallow subtidal cycles in which evidence of subaerial (up to pedogenic modifications on a large and small scale) and, less frequently, submarine exposure is common. Intermediate successions have been recognised, characterised by deposits of silty-sand plains, which present intercalations of graded, bioclastic, storm-related beds. Sedimentological characteristics seem to document more open conditions in which submarine erosion was intermittently prevalent. In these successions rudist species that are commonly found both in high-energy and low-energy assemblages coexist.     

Evolution of an isolated carbonate bank during Oligocene,Miocene and Pliocene times,Cayman Brac,British west Indies

Summary Modern carbonate sedimentation in the Caribbean Sea commonly occurs on banks that are surrounded and isolated by deep oceanic water. This depositional regime also occurred during the Tertiary, and many islands, such as Cayman Brac, have sequences that evolved in such settings. Cayman Brac is a small (about 39 km²) island, located on the Cayman Ridge, that has an exposed Oligocene to Pliocene succession which encompasses three unconformity-bounded formations. The upper Lower Oligocene Brac Formation is formed ofLepidocyclina limestones and sucrosis dolostones that locally contain numerous bivalves and gastropods. The overlying Lower to Middle Miocene Cayman Formation is formed of pervasively dolomitized mudstones to grainstones that contain an abundant, diverse biota of corals, gastropods, bivalves, foraminifera, and algae. Rhodolites are locally common. The Pliocene Pedro Castle Formation is formed of limestones, dolostones, and dolomitic limestones that contain a biota which is similar to that in the Cayman Formation. The unconformities between the formations represent substantial periods of time during which the previously deposited carbonates were lithified and eroded to produce karst terrains. All facies in the Brac, Cayman, and Pedro Castle formations on Cayman Brac developed on a bank that was no more than 20 km long and 3 km wide. There is no evidence of reef development other than isolated thickets ofStylophora and/orPorites and no systematic stratigraphic or geographic changes in the facies patterns of the formations. Comparison with modern Caribbean banks shows that the depositional regime was primarily controlled by water depth and energy levels. Limestones of the Brac Formation probably accumulated in low-energy conditions in water less than 10 m deep. The overlying Cayman Formation contains facies that formed in water 15 to 30 m deep with good cross-bank circulation. The Pedro Castle Formation formed in slightly shallower water (5–25 m) and lower energy conditions. The disconformities between the packages correlate with world wide eustatic drops in sea level.     

Mesozoic tectono-sedimentary evolution of Rocca Busambra in western Sicily

The Rocca Busambra ridge in western Sicily is a shallow to pelagic Meso-Cenozoic carbonate structural unit of the Sicilian Chain with a variety of tectono-sedimentary features. Palaeofaults, unconformities (buttress unconformity, onlap, downlap), a network of neptunian dykes with several infilling generations, several large hiatuses, different facies and lateral facies changes, and erosional submarine and subaerial surfaces are observed. Detailed fieldwork and structural analyses have indicated the occurrence of fault planes with different orientations. These data, combined with facies studies and physical-stratigraphy analyses, allow for the distinction of different depositional regions. A lateral change from an open-marine carbonate platform with a stepped fault margin (located in the westernmost sector) to a deeper basinal depositional setting in the east, in the context of an upper slope scalloped margin and base-of-slope systems with talus breccias, is envisaged here. Extensional to transtensional tectonic pulses punctuated the sedimentary evolution during Early Toarcian, Late Jurassic, Early Cretaceous, Late Cretaceous, and Early Miocene times. The collected data show that most fault planes have preserved their original orientations throughout the reactivation processes. The reconstructed Meso-Cenozoic tectono-sedimentary evolution is closely related to the late syn-rift and post-rift tectonic evolution of the Tethyan continental margin.     

Lacustrine sedimentation in the diapir-controlled Miocene Bicorb Basin, eastern Spain

The Miocene Bicorb Basin is a small elongated basin developed by normal faulting of a thick Jurassic–Cretaceous carbonate succession and subsequent diapirism of Upper Triassic mudstones and evaporites. The basin fill comprises a sequence over 650 m thick formed by two units. The lower, alluvial unit consists of a complex alternation of conglomerates, sandstones, mudstones, and minor lacustrine limestones. The upper unit comprises marginal alluvial and lacustrine deposits in which seven lacustrine facies associations have been distinguished. The inner lacustrine deposits comprise mudstones and carbonates with minor evaporitic deposits. At the northeast and southwest basin edges, alluvial inputs led to the development of delta and fan-delta environments where sandstone and conglomerate deposits dominate. The latter stages of the lake evolution are represented by an expansive thick limestone sequence which close to the NW fault-bounded margin pass laterally to breccias. The hierarchical arrangement of the upper unit shows five different orders of sequences. The first-order sequence defines a major vertical trend of lake expansion whereas three second-order sequences are linked to major flooding-expansion episodes. All these sequences are related to the tectonic evolution of the diapir. Metre-scale, third- and fourth-order sequences and fifth-order sequences, which consist of finely laminated rhythmite deposits probably record climatically forced processes. The diapir–graben system evolution and the climatic variations have exerted major controls on the sequential arrangement and evolution of the lacustrine system. Both factors have also strongly influenced the changes in the gastropod assemblages.     

Groupe de Candona clivosa, nouveau groupe de Candoninae (Crustacea, Ostracoda) et sa diversification dans le Bassin de Turiec (Slovaquie) au Miocène supérieur

The Candona clivosa-group, a new group of Candoninae - is erected on the base of the folded inner lamella observed on the postero-ventral border of the female valve. The elongated sub-triangular and rectangular valves of this group are described from the Miocene and Quaternary deposits of Europe. A folded inner lamella is also observed in 11 species of Candona from the Upper Miocene of the Turiec Basin of which 8 are new - Candona fatrica nov. sp., C. tatrica nov. sp., C. lacustris nov. sp., C. palustris nov. sp., C. stagnosa nov. sp., C. laterisimilis nov. sp., C. jiriceki nov. sp. and C. incurva nov. sp. They show a higher variability of the outline, calcification of the valves and width of the zone of concrescence. The extrinsic and intrinsic aspects of this morphological diversification in the Turiec Basin are discussed.     

An Upper Miocene siliciclastic-carbonate ramp: depositional architecture, facies distribution, and diagenetic history (Capo Vaticano area, southern Italy)

During the Late Miocene, the marginal areas of the Mediterranean Basin were characterized by the development of mixed siliciclastic-carbonate ramps. This paper deals with a temperate siliciclastic-carbonate ramp (late Tortonian–early Messinian in age) which crops out in the Capo Vaticano area, Southern Apennines (Italy). Carbonate components are mainly represented by calcitic skeletal fragments of coralline red algae, bryozoans, bivalves, and larger foraminifera, whereas corals, brachiopods, echinoderms, and planktonic foraminifera are subordinate. In the studied ramp, the depositional geometries of the main unit, the ‘Sabbie gialle ad Heterostegina’, show a gradual steepening from low/middle (dip about 2–5°) to steep slope settings (up to 25°). The microfacies observations, the quantitative analyses of the main biogenic components as well as the rhodolith shapes and growth forms allowed the differentiation between the middle and the outer ramp depositional setting and the refining of the stratigraphic framework. The middle ramp is characterized by coralline red algal debris packstone facies often associated with larger foraminiferal floatstone/packstone facies, while the outer ramp is characterized by rhodolith floatstone/rudstone facies. These facies pass basinward into typical open-marine deposits (planktonic foraminiferal facies). The taxonomic composition of the coralline red algal assemblage points to a temperate paleoclimate and emphasizes the Miocene Mediterranean phytogeographic patterns. The absence of non-skeletal grains (ooids and green algae), the paucity of Porites patch reefs, the rare occurrence of primary marine cementation, all confirm that the studied ramp was poorly lithified within a warm–temperate setting. The flat depositional profile of the ramp can be related to the absence or paucity of primary marine carbonate cements.     

First Record of Graphoglyptids in Cyprus: Indicative Presence of Turbidite Deposits at the Pakhna Formation

Abstract

Ichnological analysis at the Pakhna Formation (Miocene, Cyprus) reveals, for the first time, the presence of graphoglyptid structures. The Pakhna Formation is dominated by pelagic/hemipelagic sediments, together with contourite, reworked turbidite and turbidite facies. Thus, a complex interaction between pelagic, bottom-current and gravitational sedimentation is envisaged. The discernment of facies is sometimes difficult, based principally on stratigraphic and microfacies features. The record of Helminthorhaphe as a component of the graphoglytid group supports the presence of turbidites, facilitating their differentiation from the other facies. Nereites ichnofacies, punctuating a dominant/background Zoophycos ichnofacies, would reflect changes in paleoenvironmental conditions. This record offers significant perspectives to advance in the study of bottom-current and gravitational processes through outcrop examples.     

Stratigraphic significance of siliceous microfossils collected during dives (off Peru, 5 °–6°S)

The geological evolution of the northern Peru convergent margin can be traced using samples collected during deep-sea dives of the submersible Nautile. In the Paita area (5°–6°S), the sedimentary sequence was intensively sampled along the main scarp of the middle slope area. It consists of Upper Miocene (7–9 Ma) to Pleistocene siltstone, sandstone and rare dolostone. The age distribution of these samples is the basis for a new geologic interpretation of the multichannel seismic line CDP3.Siliceous microfossils (both diatoms and radiolarians) show influence of both cold and temperature waters (local species mixed with upwelling ones). Diatom assemblages studied from the NP1-13 and NP1-15 dives bear a strong resemblance to assemblages from the Pisco Formation of southern Peru.Micropaleontological data from siliceous microfossils, provide evidence for two main unconformities, one is at the base of the Quaternary sequence and the other corresponds to a hiatus of 1 Myr, separating the Upper Miocene (7–8 Ma) sediments from uppermost Miocene (5–6 Ma) sediments.During the past 400 kyr, a wide rollover fold developed in the middle slope area associated with a major seaward dipping detachment fault. A catastrophic debris a valanche occurred as the results of an oversteepening of the landward flank of the rollover fold. The gravity failure of the slope, recognized by SeaBEAM and hydrosweep mapping, displaced enough material to produce a destructive tsunami which occurred 13.8 ± 2.7 kyr ago.