The Legnagnone section (North-eastern Apennines) represents one of the few shallow water records of the onset of the Messinian salinity crisis. Here we present a detailed description of a ~200kyr time interval encompassing the pre-/syn-evaporitic transition based on a multidisciplinary approach, integrating sedimentological, bio-magnetostratigraphical, palaeontological and stable isotope data. Such a shallow water setting is potentially more sensitive to the palaeoenvironmental change leading to the MSC than the more often studied deeper Mediterranean basin. The aquatic palaeoenvironmental reconstruction proposed here is based on the study of foraminifer, ostracod and mollusc assemblages. It depicts a change from infralittoral (20–50m) to inner circalittoral environment (60–100m) that, since 6.12Ma, was progressively affected by a reduction of oxygen at the sea floor punctuated by short-lived anoxic events. At least three cooling events have been recognized on the basis of relative abundance data in mid to high altitude pollen, which, before 6.03Ma, are in phase with abundance peaks of Turborotalia spp., a taxon indicating eutrophic and cool surface waters. The absence of stress-tolerant benthic foraminifers during these peaks points to strong ventilation episodes triggered by a generally cooler climate. The proximity of a deltaic system and the consequent riverine input probably caused a salinity decrease of the surface waters, hindering the proliferation of planktonic foraminifers in the water column, which prevalently occur in short influxes and disappear at ca. 6Ma. Our results suggest that the onset of the crisis occurred during a phase of relative sea level high stand, whereas no evidences of sea level drop can be envisaged. The palaeoclimatic reconstruction based on palynological data indicates the dominance of a “subtropical humid forest” vegetation type, where fresh water swamps are well represented. From 6.03Ma onward, the transition to the salinity crisis is marked by more pronounced cyclical expansions of the temperate broad-leaved deciduous forest, along with herbaceous taxa. The establishment of the strongly evaporative condition at the crisis onset is not associated with major vegetational changes towards drier conditions, but linked to a sudden increase of δ18O and the disappearance of benthic foraminifers just prior to the deposition of the 1st laminated carbonate, which represents the base of the Primary Lower Gypsum unit.

This paper deals with the regional stratigraphy around the Alps-Apennines junction during late Eocene-Miocene. The basin-fill architecture and its relation to changes in structural style were deciphered through the integration of subsurface and outcrop data on the basis of seismic- and sequence-stratigraphy principles, respectively. During late Eocene-Oligocene, the study area hosted a mosaic of partially interconnected sub-basins, and the Torino Hill area marked the junction towards the western apex of the Southern Alps foredeep (Gonfolite Basin). Since the latest Oligocene, the uplift of the north-verging Monferrato arc provided the separation from the adjacent Gonfolite Basin and the Tertiary Piedmont Basin behaved as a larger and more regularly subsiding thrust-top basin. The upper Eocene-Miocene successions record a long-term, major transgressive-regressive cycle, consisting of seven large-scale unconformity-bounded stratigraphic units, whose stacking pattern was controlled by changes in the rate of tectonic subsidence and whose boundaries were generated by basin-modification phases. During the Oligocene-lower Miocene deepening-upward sequence set, the marginal marine systems show a marked diachronism associated with the SW-ward change of coastal onlap, punctuated by drowning-platform unconformities generated in relation to basinward tilting and high-angle synsedimentary faults. The maximum transgression coincides with the late Burdigalian tectonic space creation phase, when a basinwide, highly efficient turbidite system was deposited. The middle-upper Miocene progradation, punctuated by forced regression pulses, was driven by the inversion and uplift of the southern basin margin, so that a northward shift and progressive narrowing of the turbidite depocentre occurred.

A possible deep-water non-evaporitic unit equivalent of the Messinian Lower Evaporites has been recognised in the Northern Apennine foredeep. This unit, whose existence is implicitly admitted in the two-step model of the Mediterranean Messinian salinity crisis is documented here for the first time; it occurs throughout the Apennine foredeep basin below a thick horizon of resedimented gypsum deposits, usually ascribed to the Lower Evaporites. Actually, the Lower Evaporites of the Apennine foredeep basin include both shallow-water, in situ precipitated facies and deep-water, resedimented facies deposited in distinct depocenters. The usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a) physical-stratigraphic considerations about the downbasin correlation of the Messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b) the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre-evaporitic successions underlying the in situ precipitated evaporites. In this work a multidisciplinary study has been carried out on a 140 m-thick composite section (Fanantello section) to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits. The topmost part of the section comprises a 60 m-thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a) the complete disappearance of Foraminifera, b) the occurrence of high salinity tolerant thecosomatous pteropods (Creseis sp.) c) the abundance peaks of the calcareous nannofossil Sphenolithus abies (interpreted as related to highly stressed likely hyperhaline conditions), d) the appearance of hyperhaline and/or stratified water molecular indicators (gammacerane, < 0.2 pristane/phytane ratio, < 1 n-alkanes odd-even predominance).Based on a multidisciplinary integrated stratigraphic approach this barren interval, is here proposed to be a deeper-water time equivalent of the in situ primary Lower Evaporites, thus allowing to assess the events connected to the onset and the first phase of the Messinian salinity crisis from a basinal perspective.

The dinoflagellate cyst, palynofacies and foraminiferal records from the Early Eocene Figols Group of the Spanish Pyrenees exhibit major changes associated with relative sea-level fluctuations and variations in efficiency of the fluvial systems. The mixed siliciclastic-carbonate marine succession exposed in the Merli-Esdolomada area was deposited on the shelf in a tectonically active basin, under oxic conditions, in shallow to moderately deep marine waters (close to the lower boundary of the photic zone) influenced by river discharge from adjacent emerged lands. Sedimentary cycles are mainly recorded by fine-grained deposits. The paleoenvironmental interpretation of palynological and calcareous microfaunal records allows the definition of depositional sequences and enables to trace basinward surfaces identified in more proximal settings by means of sedimentological facies analysis. At the same time, the solid regional stratigraphic framework already available for the Figols Group allows new insights on the paleoecology of extinct taxa.The Merli-Esdolomada section (ME) spans two 3rd order sequences. The upper sequence reflects more marginal marine conditions than the lower one, thus pointing to an overall shallowing trend with time. In the lower sequence the maximum flooding interval is characterised by a rich and diverse microfauna, highest relative abundances of marine phytoplankton and typically neritic dinoflagellate cyst (dinocyst) assemblages dominated by Spiniferites and Cordosphaeridium. The final phase of the highstand systems tract, in proximity of the main sequence boundary, is characterised by a decrease in abundance and diversity of dinocysts, with the dominance of the lagoonal genus Polysphaeridium, and by decreased microfaunal diversity (discorbids, miliolids, larger foraminifers).Palynological records permit the reconstruction of activation and deactivation phases of the fluvial systems, variations in runoff from the hinterland, nutrient delivery to the sea and productivity in surface waters of the Tremp-Graus Basin. The overall abundance of Spiniferites and the scarcity of peridinioid cysts, Lingulodinium, Pediastrum and Botryococcus algae are interpreted to indicate oligotrophic conditions during the deposition of the investigated succession. Recurrent intervals where the temporary disappearance of Spiniferites corresponds to highest relative abundances of Operculodinium and herbaceous debris are the main evidence for river plumes and denote periods of enhanced fluvial discharge reflecting a Milankovitch-type cyclicity. The Rotalia group, which shows abundance peaks of Cuvillierina spp. in the shallower intervals, is often associated with these episodes, thus suggesting for this taxon more tolerance to turbidity than larger foraminifera. Within the maximum flooding zone, a Thalassiphora patula acme corresponding to the local disappearance of Homotryblium is deemed to record the distal expression of a fluvial activation which triggered water salinity stratification. Despite broad morphological similarities, Homotriblium exhibits more cosmopolitan preferences than Polysphaeridium, which is instead confirmed as a lagoonal euryhaline taxon. The increase of Spinizonocolpites pollen toward the top of the Figols Group records the northwestward migration of Nypa mangrove-palms from southern Europe during the mid Early Eocene. (c) 2005 Elsevier B.V. All rights reserved.

Eight dinoflagellate cyst zones based on the Massignano and Monte Cagnero sections in central Italy provide high-resolution control for the Eocene/Oligocene (E/O) transition. Most of these zones have been recognized in the time-equivalent Contessa Highway section and are calibrated against previously established magneto- and biostratigraphies. The invasion of the Mediterranean area by several higher-latitude dinoflagellate taxa marks the E/O boundary as characterized by the last occurrence of the hantkeninids (planktic foraminifers), calibrated against a horizon just above the youngest normal polarity event within Chron C1 3R. Quantitative and qualitative dinoflagellate events across the E/O boundary allow the recognition of warmer and cooler successive intervals of sea surface temperature, in addition to apparent sea-level fluctuations. Our data indicate that latest Eocene warm conditions and a sea-level highstand were rapidly replaced by short-term cooler conditions and a lowstand across the E/O boundary horizon. Following a shortterm warmer interval and a highstand during the earliest Oligocene, a second cool and lowstand episode occurred. This cool interval was of greater magnitude and duration than the one at the E/O boundary horizon and may correspond to the globally recognized cooling event reported from the basal part of Chron C1 3N.

An abundant and diverse assemblage of Oligocene peridinioid dinoflagellate cysts has been recovered from 15 boreholes in the Niger Delta. Seven new species belonging to Lejeunecysta, two new species of Phelodinium and one new species of Selenopemphix are proposed. Four new species, tentatively assigned to Lejeunecysta, are described and left in open nomenclature, due to uncertainty as to generic rank. Lejeunecysta fallax is emended. INTRODUCTION In the course of oil exploration, palynological analyses were carried out on fifteen boreholes of subsurface Tertiary sediments in the Niger Delta (text-fig. 1). The Oligocene samples studied yielded rich dinoflagellate cyst assemblages. Specimens of Lejeunecysta (Gerlach) Artzner and Dbrh6fer, 1978, Phelodinium Stover and Evitt, 1978, and Selenopemphix Benedek, 1972 emend. Bujak, 1980 are particularly abundant. The present paper formally describes seven new species of Lejeunecysta, two new species of Phelodinium and one new species of Selenopemphix. Lejeunecysta fallax (Morgenroth) Artzner and D6rh6fer, 1978 is emended, and four new species, tentatively assigned to Lejeunecysta, are described and left in open nomenclature, owing to the uncertainty at generic rank. Many problems confront one when trying to describe and speciate an abundant and morphologically intergrading group such as the Oligocene peridinialean dinoflagellate cysts. In fact, the species of Lejeunecysta (as Lejeunia Gerlach, 1961) have hitherto been for the most part poorly defined. We here make an attempt to define certain morphological criteria for speciating the Lejeunecysta cysts, in order to identify potentially useful stratigraphical markers. Harland (personal communication, 1981) believes that the archeopyle shape and position, a continuous or discontinuous paracingulum, compression (as it reflects the natural three-dimensional shape of the cyst), and overall size are important criteria for speciating these cysts. Additionally, we believe that the ornamentation features of the autophragm, the shape and length of the antapical horns, the occurrence of an apical horn, its shape and length, and the length/breadth cyst ratio have also to be considered as criteria for speciation. These criteria are, above all, particularly important for the laevigate cysts, which up to now have been generally placed in either Lejeunecysta hyalina (Gerlach) Artzner and D6rh6fer, 1978 or Lejeunecysta fallax. The type material of this study is stored at AGIP S.p.A., SGEL Service (Geological Studies and Laboratories), Palynology Unit, S. Donato Milanese, Milan, Italy. The specimen coordinates are from the Leitz Orthoplan microscope, and all microphotographs were made with an Orthomat camera. GEOLOGIC SETTING AND STRATIGRAPHY The Eocene-Pliocene sediments of the Niger Basin are essentially deltaic sands and shales, which reflect the different environments of demicropaleontology, vol. 29, no. 2, pp. 126-145, pls. 1-7, 1983 126 This content downloaded from 157.55.39.195 on Thu, 14 Apr 2016 06:27:24 UTC All use subject to http://about.jstor.org/terms Micropaleontology, vol. 29, no. 2, 1983 TEXT-FIGURE 1 Location map showing Niger Delta region and studied areas. OML 60 and 61 are the Nigerian AGIP Oil Company permits in which studied wells are situated. position. In the Niger Basin three main lithostratigraphic units are known: 1) Benin Formation: sands with a few shale intercalations: sometimes lignite occurs in thin streaks. The sands are considered to represent deposits of a continental upper delta plain, while the shales may be interpreted as backswamp deposits. 2) Agbada Formation: alternate sandstones and sand bodies, typical of a lower tidal coastal plain-littoral environment, with marine shale layers. 3) Akata Formation: prodelta-open marine shales. The age of these formations ranges from Eocene to Recent, owing to progradation of the Niger Delta (Short and Stauble, 1967; AGIP-NAOC, internal reports). In this paper, we consider only the Oligocene sedi-