summary of italian marine stages

Eight marine stages for the Quaternary have been defined in Italy starting from 1872 (Sicilian of Doderlein) to 1979 (Selinuntian of Ruggieri and Sprovieri). The definition of all these stages was based essentially on invertebrate paleontology, initially from the study of pelecypods and gastropods, but also of corals, ostracods, benthic foraminifers and, more recently, on planktonic foraminifers and calcareous nannofossils. The 1948 International Geological Congress held in London decided to search for a locality in Italy to define the Neogene/Quaternary boundary in correspondence with the first appearance of the "northern guests" in the Mediterranean. The Vrica section of Calabria was selected for defining the GSSP of the Pleistocene in 1984. Meanwhile, starting from 1970 the deep-sea record of the western, central and eastern Mediterranean was explored by five Legs of the Deep Sea Drilling Program and Ocean Drilling Program. As a result of integrated, high resolution multidisciplinary investigations of the deep-sea record and of continuous sections exposed on land, a robust chronostratigraphic framework could be constructed. The combination of biochronology, magnetostratigraphy, isotopic stratigraphy, astrocyclostratigraphy, and tephrostratigraphy assures the worldwide correlation potential of the Mediterranean record

Formal ratification of the GSSP for the base of the Calabrian Stage (second stage of the Pleistocene Series, Quaternary System)

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DOLOMITIC SEDIMENTS IN CORE BAN 89-22 GC FROM THE DEEP-SEATED BRINES OF BANNOCK BASIN, EASTERN MEDITERRANEAN

Core Ban 89-22 GC has been recovered in the Bannock Basin (Eastern Mediterranean) on the large sill separaring Borea and Maestro sub-basins in an area covered by high density brines. The interest of this core consists in its dolomitic composition, for this reason the core has been studied in its sedimentological and micropaleontological characters with great detail. The use of particular analyses (C.A.T. Computerized axial tomography, carbonate percentage, smear-slides observations of all samples for the identification of nannofossil Zones and for the mineralogic composition of the sediments, EDAX) allows to explain the dolomitic composition as secondary diagenization due to the upward molecular diffusion or advection of Mg++ ions from the dissolution of primary dolomite of Messinian age, recovered in the core-catcher thus in contact with the Pleistocene-Holocene core sediments

CLIMATICALLY MODULATED ANOXIC EPISODES AND PRODUCTIVITY IN THE MIDDLE PLEISTOCENE (CROTONIAN) OF THE EASTERN MEDITERRANEAN

A portion of a deep-sea core that contains a purely pelagic low- sedimentation-rate succession, extends in time from approximately 260,000 to 160,000 y BP, includes the Gephyrocapsa oceanica/Emiliania huxleyi zonal boundary, and the four sapropels S-9 through S-6, was investigated in detail. Carbonate content, org C content, grain-size analysis, composition of the sand-size sediment fraction, isotopic composition of O and C were measured with an observation point every approximately 300Oy. Cyclicity represented by the sapropels is fairly regular and is of the order of 20,000 y (Milankovitch precession cycles). The grain-size increases consistently in the sapropels, whereas the carbonate content usually decreases, with the exception of S-6. Biogenic components are always dominant, whereas organic matter abounds in sapropels, especially in S-7 which records 9% org C. The number of planktonic foraminifers ranges around a few thousands per gram of sediment; increases of one order of magnitude are noticed in sapropels S-6 and S-8, thus supporting increased productivity, as suggested by the dominance of Neogloboquadrina dutertrei. The consistent decrease in the number of pteropod fragments in all sapropel layers is attributed to dissolution of the easily dissolvable aragonitic tests in the deep-sea acidic environment

Chronostratigraphy and geochronology: a proposed realignment

We propose a realignment of the terms geochronology and chronostratigraphy that brings them broadly into line with current use, while simultaneously resolving the debate over whether the Geological Time Scale should have a “single” or “dual” hierarchy of units: Both parallel sets of units are retained, although there remains the option to adopt either a single (i.e., geochronological) or a dual hierarchy in particular studies, as considered appropri-ate. Thus, geochronology expresses the timing or age of events (depositional, diagenetic, biotic, climatic, tectonic, magmatic) in Earth’s history (e.g., Hirnantian glaciation, Famennian-Frasnian mass extinction). Geochronology can also qualify rock bodies, stratified or unstratified, with respect to the time interval(s) in which they formed (e.g., Early Ordovician Ibex Group). In addition, geochronology refers to all methods of numerical dating. Chronostratigraphy would include all methods (e.g., biostrati-graphy, magnetostratigraphy, chemostratigraphy, cyclostrati-graphy, sequence stratigraphy) for (1) establishing the relative time relationships of stratigraphic successions regionally and worldwide; and (2) formally naming bodies of stratified rock that were deposited contemporaneously with units formally defined at their base, ideally by a GSSP (Global Boundary Stratotype Section and Point = “golden spike”) that represents a specific point in time. Geochronologic units may be defined and applied generally by either GSSPs or—as currently in most of the Precambrian—by Global Standard Stratigraphic Ages (GSSAs). Geochronologic units would continue as the time units eons/eras/periods/epochs/ages, and chronostratigraphic units as the time-rock units eonothems/erathems/systems/series/stages. Both hierarchies would remain available for use, as recommended by a formal vote of the International Commission on Stratigraphy in 2010. Geological context helps determine the appropriate usage of the component units

Global stages, regional stages or no stages in the Plio/Pleistocene?

Over recent decades, with extended exploration of all the oceans, with the study of ice cores from Greenland and Antarctica, with all the high resolution methodologies now available for integrated stratigraphy, there has been a tendency in several milieux to abandon the use of stages for the Plio/Pleistocene. We do not agree with this approach and consider the use of standard stages in the Plio/Pleistocene as appropriate as for older parts of the Phanerozoic. In the hierarchy of chronostratigraphic units (erathem-system-series-stage), stage is the unit of lowest rank, and of widest and longest usage. Moreover, stage is the only chronostratigraphic unit defined on the basis of a typological criterion: units of higher rank are usually defined on the basis of the hierarchical principle. In the Plio/Pleistocene there are three formalized stages: Zanclean, Piacenzian and Gelasian (oldest to youngest), all defined in the Mediterranean area, a small geodynamically active ocean basin, where uplift of coastal areas has exposed continuous successions of deep marine Plio/Pleistocene strata. The Zanclean GSSP is an example of event stratigraphy: the Pliocene transgression marking the sudden invasion by Atlantic water masses of the desiccated Mediterranean, terminating the Messinian salinity crisis. The other two Plio/Pliocene GSSPs are defined using multiple criteria, but mainly by reversals of the magnetic field polarity. Following the recent IUGS ratification of the formerly Pliocene Gelasian Stage as the oldest stage of the Pleistocene, formalization of younger Pleistocene stages is in progress, starting from the Calabrian. With just one name of precise and well controlled time significance and multiple criteria for global correlation, one can identify a defined time interval in both terrestrial and marine realms, independent of latitude, bioprovincialism and historical evolution

Maximum and mean diameter record of Orbulina universa from DSDP Hole 47-397 of Cape Bojador, eastern North Atlantic

Measurements of the diameter of O. universa carried out on 30 specimens from 39 samples covering a sediment thickness of 78 m and going back in time to approximately 750 000 y resulted in the construction of a curve of the mean diameter and a curve of the maximum diameter. Both curves, as well as those calculated with the running-averages technique, display cyclic fluctuations with durations of the order of 100 000 y and downwards decreasing amplitudes. These curves are compared with a carbonate curve (on bulk sediment) and an isotopic curve (on benthic foraminifers) obtained from the same set of samples. Correlations are fair to good, but a timelag is noticed between the isotopic curve and the faunal (O. universa mean diameter) curve, with the isotopic signal coming first, in the middle part of the Brunhes Epoch. Biostratigraphic calibration to the paleomagnetic record is provided by four datum planes (two based on calcareous nannofossils, two on diatoms) identified in the succession. Changes recorded in test porosity seem to be less meaningful than changes in test size