Magnetostratigraphy-based astronomical tuning of the early Pliocene lacustrine sediments of Ptolemais (NW Greece) and bed-to-bed correlation with the marine record

Continental deposits from the early Pliocene lacustrine Ptolemais basin in NW Greece display rhythmical alternations of lignite and marl beds. Three parallel sections from this area are studied using magnetostratigraphy and cyclostratigraphy. The presence of the greater part of the Gilbert Chron enables the recognition of astronomical periodicities in the succession. Especially the precessional influence is evident, as it determines the lithological cycles. The continental Ptolemais composite section is correlated to the most recent astronomical time scale and thus to the marine reference section: the Rossello composite from Sicily [C.G. Langereis, F.J. Hilgen, The Rossello composite: a Mediterranean and global reference section for the Early to early Late Pliocene, Earth Planet. Sci. Lett. 104 (1991) 211-225] on a bed-to-bed scale. It is concluded that lignite corresponds to an insolation minimum (beige layer in the Rossello composite), and marl to an insolation maximum (grey layer in the Rossello composite). This implies a precipitation increase during insolation maxima in early Pliocene continental Greece. Ó 1998 Elsevier Science B.V. All rights reserved

A Late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean arc

Palaeomagnetic measurements have been carried out on Eocene to Pleistocene sediments on the Ionian island of Zakynthos, NW Greece. Magnetostratigraphic constraints, biostratigraphic analyses of planktonic foraminifera and calcareous nannofossils provide a reliable time frame for these deposits. The results show that no significant rotation occurred between 8.11 and 0.77 Ma, but that Zakynthos underwent a 21.6º 7.4º clockwise rotation between 0.77 Ma and Recent. Thus, our data indicate a rapid rotational event, in contrast to continuous rotation since 5 Ma as previously postulated [Laj et al., Tectonophysics 86 (1982) 45 67]. We speculate this late Pleistocene tectonic rotation phase to be linked to rapid uplift in the Greek region which results from rebound processes caused by (African) slab detachment underneath the Ionian islands. Ó 1999 Elsevier Science B.V. All rights reserved

Comment on: 'A late Pleistocene clockwise rotation phase of Zakynthos (Greece) and implications for the evolution of the western Aegean Arc'

In a recent paper, Duermeijer et al. [1] report new palaeomagnetic results from the island of Zakynthos (Greece). In many cases, these authors have re-sampled the original sites of Laj et al. [2] and the results are virtually identical to those of the earlier study except for much more precise biostratigraphic age control. Three middle Pleistocene sites (Bochali, Zakynthos town and Porto Roma) which were not sampled by Laj et al. document signi¢cant clockwise rotations. From the results obtained from these three new sites, the authors conclude that the 25° clockwise rotation of Zakynthos described by Laj et al. as affecting the entire western Hellenic margin more or less progressively over the last 5 Myr is much more recent (early Pleistocene)

Reconstruction of marine paleoenvironments : selection of papers presented at the meeting in Utrecht, March 21-25, 1983

The international meeting on "Reconstruction of marine paleoenvironments; principles and methods" was held in Utrecht, the Netherlands, from March 21-25, 1983. It was organized by J. E. Meulenkamp with the assistance of other staff members of the Department of Stratigraphy and Micropaleontology of the State University of Utrecht. The meeting was sponsored by the Regional Committee on Mediterranean Neogene Stratigraphy of the I.U.G.S., by the International Nannoplankton Association and by the I.U.G.S. Working Group on the Paleogene/Neogene boundary. The larger part of the programme consisted of talks by invited speakers from various disciplines of the earth sciences. Most of the invited speakers agreed to publish their contribution; the present U.M.B. volume includes 75% of the papers read during the plenary morning sessions. The editing task was carried out with the assistance of G. J. van der Zwaan, W. J. Zachariasse, A. J. T. Romein and C. W. Drooger. Most of the figures were drawn or re-drawn by A. van Doorn, J. T. van Hinte and P. Hoonhout. Proof reading was carried out in Utrecht by a large group of department members

Stratigraphy of Neogene deposits in the Rethymnon Province, Crete, with special reference to the phylogeny of uniserial Uvigerina from the Mediterranean region

Stratigraphical and micropaleontological investigations were performed on Neogene deposits of the Rethymnon Province, Western Crete. The Neogene succession includes marine as well as brackish and fresh-water sediments. Eight formations are recognized, several of which have to be regarded as lateral equivalents. From the sediment types and their distribution along the north coast it is concluded that to-day's topography still reflects the paleogeographic conditions existing during the Neogene. The micropaleontological part of the paper deals with the phylogeny of two groups of Uvigerinids, the U. melitensis group and the U. cretensis group, both showing a main trend to uniserial chamber arrangement. Apart from our Cretan material samples are studied from localities elsewhere in the Mediterranean region. These samples are derived from Italy, Spain, France and Malta, and are partly taken from the stratotypes of the Late Neogene stages. The representatives of the U. melitensis and the U. cretensis groups can be distinguished by external characters such as the presence or absence of a distinct, regular, biserial stage in between the triserial and uniserial parts of the test, the more or less recurved character of the sutures, and the regular or irregular arrangement of the early uniserial chambers. The U. cretensis group corresponds to the U. gaudryinoides group in the literature, whose phylogeny was first emphasized by PAPP(1963). Representatives of this group are common in younger Neogene deposits throughout the Mediterranean region. So far the U. melitensis group is restricted to the Maltese Neogene and to the basal part of the Cretan Neogene succession. The evolutionary trend is the same in both lineages and comprises among other things an increase in the average number of uniserial chambers, an increase in the relative length of the uniserial part of the test, and the development toward an arrangement of the uniserial chambers in more regular series. Besides, a general trend is observed to relatively more slender tests. No development is found in the length or in the breadth of the test. The striate ornamentation appears to be strongly environment controlled; specimens from deposits close to evaporites show an aberrant ornamentation. Since a typological approach of the observed features proves to give unsatisfactory results, counts and measurements are made on a number of parameters. The latter are based on the number of uniseral chambers, the character of the uniserial chambers, the length of the uniserial part of the test, and the length and the breadth of the test. The uniserial chambers can be divided into primitive uniserial chambers and fully developed ones, depending on the angle between the upper and lower sutural planes. In fully developed uniserial chambers these planes are more or less parallel, whereas they form an angle of 20° and more in primitive uniserial chambers. In ontogeny, the fully developed uniserial chambers are the younger ones. In the course of time the relative number of primitive uniserial chambers decreases, i.e., the uniserial chambers become arranged in more regular series. By comparing the number of primitive unserial chambers present at the same growth stage - for instance in all individuals with two uniserial chambers, or in those with three, or with four - parameters become available that are independent of the final ontogenetic stage the specimens reached. Apparently these parameters show the most constant development, evidently not influenced by external circumstances. In the course of phylogeny, most of the parameters and their means become more strongly correlated. In the higher part of the phylogenetic sequences random fluctuations in test size thus cause significant set-backs of the means in all other parameters, except in those based on the number of primitive uniserial chambers in specimens at the same ontogenetic stage. Both lineages are not synchronous. The melitensis lineage starts approximately at the Orbulina surface (base Serravallian?). Uvigerina (Hopkinsina) bononiensis compressa is considered to be the forerunner. The last representatives of the lineage are found in deposits of Early-Middle Tortonian Age. The cretensis lineage probably starts in the Early Tortonian, and it ranges up into the Pleistocene. Its ancestor is as yet unknown. By statistical methods four morphologically adjoining species, successive in time, could be distinguished within each lineage. Seven of our eight species are new, because no meaningful contents could be given in terms of our biometrical analysis to the existing species names. Biostratigraphic correlations of our Cretan marine formations with the Late Neogene stratotypes indicate that marine sedimentation in the Rethymnon region started in the Early-Middle Tortonian and that it persisted up into the Pliocene without interruption. An interval of less than one Uvigerina Range zone, if any, seems to be present between the uppermost part of the type Tortonian (sensu GIANOTTI 1953, not CITA et aI1965) and the base of the Tabianian stratotype. If we accept GIANOTTI'S definition of the upper limit of the Tortonian stratotype, there seems to be no need of a separate stage between the Tortonian and the Pliocene. The Andalusian stratotype is younger than the type Tortonian; actually it can be correlated with the Tabianian and Piacenzian stratotypes, which correlation points to its Pliocene Age. The Maltese Blue Clay and Greensand are considered older than the Cretan Neogene; the Upper Coralline Limestone may be contemporaneous with the basal marine deposits of Crete

Extraction of Morphotectonic Features from DEMs: Development and Applications for Study Areas in Hungary and NW Greece

A procedure for the consistent application of digital terrain analysis methods to identify tectonic phenomena from geomorphology is developed and presented through two case studies. Based on the study of landforms related to faults, geomorphological characteristics are translated into mathematical and numerical algorithms. Topographic features represented by digital elevation models of the test areas were extracted, described and interpreted in terms of structural geology and geomorphology. Digital terrain modelling was carried out by means of the combined use of: (1) numerical differential geometry methods, (2) digital drainage network analysis, (3) digital geomorphometry, (4) digital image processing, (5) lineament extraction and analysis, (6) spatial and statistical analysis and (7) digital elevation model-specific digital methods, such as shaded relief models, digital cross-sections and 3D surface modelling. A sequential modelling scheme was developed and implemented to analyse two selected study sites, in Hungary andNWGreece on local and regional scales. Structural information from other sources, such as geological and geophysical maps, remotely sensed images and field observations were analysed with geographic information system techniques. Digital terrain analysis methods applied in the proposed way in this study could extract morphotectonic features from DEMs along known faults and they contributed to the tectonic interpretation of the study areas.JRC.H.5-Rural, water and ecosystem resource

Late Miocene to Early Pliocene depositional history of the intramontane Florina-Ptolemais-Servia Basin, NW Greece: Interplay between orbital forcing and tectonics

Upper Miocene and Lower Pliocene shallow lacustrine deposits from the Florina-Ptolemais-Servia Basin in northwest Greece show a distinct m-scale sedimentary cyclicity of alternating marls and lignites or clays, which were shown to be primarily related to precession-induced climate variations ([van Vugt, N., Steenbrink, J., Langereis, C.G., Hilgen, F.J., Meulenkamp, J.E., 1998. Magnetostratigraphy-based astronomical tuning of the early Pliocene lacustrine sediments of Ptolemais (NW Greece) and bed-to-bed correlation with the marine record. Earth Planet. Sci. Lett. 164 (3-4) 535-551; Steenbrink, J., Van Vugt, N., Hilgen, F.J., Wijbrans, J.R., Meulenkamp, J.E., 1999. Sedimentary cycles and volcanic ash beds in the lower Pliocene lacustrine succession of Ptolemais (NW Greece): Discrepancy betwee