Sequence stratigraphy in the context of rapid regional uplift and high‐amplitude glacio‐eustatic changes: the Pleistocene Cutro Terrace (Calabria,southern Italy)

The Cutro Terrace is a mixed marine to continental terrace, where deposits up to 15 m thick discontinuously crop out in an area extending for ca 360 km² near Crotone (southern Italy). The terrace represents the oldest and highest terrace of the Crotone area, and it has been ascribed to marine isotope stage 7 (ca 200 kyr bp ). Detailed facies and sequence‐stratigraphic analyses of the terrace deposits allow the recognition of a suite of depositional environments ranging from middle shelf to fluvial, and of two stacked transgressive–regressive cycles (Cutro 1 and Cutro 2) bounded by ravinement surfaces and by surfaces of sub‐aerial exposure. In particular, carbonate sedimentation, consisting of algal build‐ups and biocalcarenites, characterizes the Cutro 1 cycle in the southern sector of the terrace, and passes into shoreface and foreshore sandstones and calcarenites towards the north‐west. The Cutro 2 cycle is mostly siliciclastic and consists of shoreface, lagoon‐estuarine, fluvial channel fill, floodplain and lacustrine deposits. The Cutro 1 cycle is characterized by very thin transgressive marine strata, represented by lags and shell beds upon a ravinement surface, and thicker regressive deposits. Moreover, the cycle appears foreshortened basinwards, which suggests that the accumulation of its distal and upper part occurred during forced regressive conditions. The Cutro 2 cycle displays a marked aggradational component of transgressive to highstand paralic and continental deposits, in places strongly influenced by local physiography, whereas forced regressive sediments are absent and probably accumulated further basinwards. The maximum flooding shoreline of the second cycle is translated ca 15 km basinward with respect to that of the first cycle, and this reflects a long‐term regressive trend mostly driven by regional uplift. The stratigraphic architecture of the Cutro Terrace deposits is the result of the interplay between regional uplift and high amplitude, Late Quaternary glacio‐eustatic changes. In particular, rapid transgressions, linked to glacio‐eustatic rises that outpaced regional uplift, favoured the accumulation of thin transgressive marine strata at the base of the two cycles. In contrast, the combined effect of glacio‐eustatic falls and regional uplift led to high‐magnitude forced regressions. The superposition of the two cycles was favoured by a relatively flat topography, which allowed relatively complete preservation of stratal geometries that record large shoreline displacements during transgression and regression. The absence of a palaeo‐coastal cliff at the inner margin of the terrace supports this interpretation. The Cutro Terrace provides a case study of sequence architecture developed in uplifting settings and controlled by high‐amplitude glacio‐eustatic changes. This case study also demonstrates how the interplay of relative sea‐level change, sediment supply and physiography may determine either the superposition of cycles forming a single terrace or the formation of a staircase of terraces each recording an individual eustatic pulse.     

Crystallization Driven by Decompression and Water Loss at Stromboli Volcano (Aeolian Islands, Italy)

Stromboli, in the Aeolian Archipelago, is famous for its persistentvolcanic activity. The ‘normal’ activity, consistingof rhythmic explosions ejecting crystal-rich scoriae, is periodicallyinterspersed with more energetic explosions during which, inaddition to crystal-rich scoriae, crystal-poor pumices are alsoemitted. The scoriae contain     

Automicrite in a ‘nummulite bank’ from the Monte Saraceno (Southern Italy): evidence for synsedimentary cementation

Following introduction of the term ‘nummulite bank’, there has been debate regarding interpretation of these types of deposits as autochthonous (automicrite) or allochthonous (detrital micrite). These banks are made up of large foraminifera and ill‐defined fine‐grained components. The fine‐grained components consist mainly of micrites. The recognition of automicrite has deep implications for the synsedimentary cementation and stabilization of the bank. In order to distinguish between automicrite and detrital micrite, the nanomorphology, geochemistry and organic matter remains in the microfacies of a nummulite bank in the Middle Eocene of Monte Saraceno (Gargano, Southern Italy) were analysed. Optical and scanning electron microscope investigations showed that the micrites have been recrystallized to aggrading microsparite. Epifluorescence observations on selected micrite/microsparite areas with peloidal texture revealed the presence of organic matter. Scanning electron microscope analyses on epifluorescent micrites showed that the microbial peloids have smaller crystal sizes than those in organic matter‐depleted areas. The geochemical characterization of extracted organic matter, performed through the functional group analyses by Fourier transform‐infrared spectroscopy, shows strong prevalence of the aromatic fraction over the aliphatic and carboxylic ones. These characteristics of organic compounds indicate both their thermal maturation and their likely derivation from degradation of bacterial communities. The local presence of peloidal anti‐gravity textures, bright epifluorescence and organic molecules in clotted peloidal areas suggest that the metabolic activity of microbial communities could have induced precipitation of these micrites and, consequently, the syndepositional cementation of the nummulite bank. This type of cementation can rapidly stabilize sediments and promote the depositional bank geometry.     

Subaqueous density flow processes and deposits of an island volcano landslide (Stromboli Island, Italy)

Stromboli is a 3000 m high island volcano, rising to 900 m above sea-level. It is the most active volcano of the Aeolian Archipelago in the Tyrrhenian Sea (Italy). Major, large volume (1 km³) sector collapses, four occurring in the last 13 kyr, have played an important role in shaping the north-western flank (Sciara del Fuoco) of the volcano, potentially generating a high-risk tsunami hazard for the Aeolian Islands and the Italian coast. However, smaller volume, partial collapses of the Sciara del Fuoco have been shown to be more frequent tsunami-generating events. One such event occurred on 30 December 2002, when a partial collapse of the north-western flank of the island took place. The resulting landslide generated 10 m high tsunami waves that impacted the island. Multibeam bathymetry, side-scan sonar imaging and visual observations reveal that the landslide deposited 25 to 30 × 10⁶ m³ of sediment on the submerged slope offshore from the Sciara del Fuoco. Two contiguous main deposit facies are recognized: (i) a chaotic, coarse-grained (metre-sized to centimetre-sized clasts) deposit; and (ii) a sand deposit containing a lower, cross-bedded sand layer and an upper structureless pebbly sand bed capped by sea floor ripple bedforms. The sand facies develops adjacent to and partially overlying the coarse deposits. Characteristics of the deposits suggest that they were derived from cohesionless, sandy matrix density flows. Flow rheology and dynamics led to the segregation of the density flow into sand-rich and clast-rich regions. A range of density flow transitions, both in space and in time, caused principally by particle concentration and grain-size partitioning within cohesionless parent flows was identified in the deposits of this relatively small-scale submarine landslide event.     

Use of satellite communication of hydrometric data for the whole of Brazil

Abstract

The difficulties of exploiting the huge Brazilian hydrometeorological network led hydrologists of the Departamento Nacional de Águas e Energie Elétrica (DNAEE—Brazilian Department of Water and Electric Power) to use real time satellite telecommunications to improve network management. Data-gathering satellites, which are perfectly adapted to this network, were first used in 1975 and have interested DNAEE since 1980. Collaboration with ORSTOM permitted an initial evaluation of the technique in 1982. In 1984 DNAEE, together with ORSTOM, was able to set up a 20-station network in the Amazon. The results have been so encouraging that a scheme for 200 stations equipped with telecommunications facilities which use the Brazilian Satélite de Colecta de Dados number 1 (SCD1) satellite is in the final stages. This network will cover the entire country.     

Relationships between high‐magnitude relative sea‐level changes and filling of a coarse‐grained submarine canyon (Pleistocene,Ionian Calabria,Southern Italy)

A middle Pleistocene coarse‐grained canyon fill succession (the Serra Mulara Formation) crops out in the northern sector of the Crotone Basin, a forearc basin located on the Ionian side of the Calabrian Arc and active from the Serravallian to middle Pleistocene. This succession is an example of coarse‐grained submarine canyon fill, which consists of a north‐west to south‐east elongated body (4·25 km long and up to 1·5 km wide) laterally confined by a deep‐water clayey and silty succession and located behind the modern Neto delta (north of Crotone). The thickness of the unit reaches 178 m. The lower part of the canyon fill is dominated by gravelly to sandy density‐flow deposits containing abundant bivalve and gastropod fragments, passing upward into a succession composed of metre‐scale to decimetre‐scale density‐flow deposits forming sandstone–mudstone couplets. Sandstone deposits are mostly structureless and planar‐laminated, whereas the clayey layers record hemipelagic deposition during quieter phases. This succession is overlain by another composed of thicker structureless sandstones alternating with layers of interlaminated mudstones and sandstones, which contain leaf remnants and fresh water ostracods, and are linked directly to river floods. The canyon fill is overlain by gravelly to sandy continental deposits recording a later stage of emergence. Facies analysis, together with micropalaeontological data from the hemipelagic units, suggests that the studied canyon fill records, firstly, a progressive gravel material cut‐off during deposition due to an overall relative sea‐level rise, leading to a progressive increase in the entrapment of sediment in fluvial to shallow‐marine systems, and secondly, a generalized relative sea‐level lowering. This trend probably reflects high‐magnitude glacio‐eustatic changes combined with the regional uplift of the region, ultimately leading to emergence.     

LAKE-ICE BLISTERS, TERRA NOVA BAY AREA, NORTHERN VICTORIA LAND, ANTARCTICA

Ice blisters, typically 0.2–0.8 m high and 5–20 m long, develop annually on perennially frozen lakes in Northern Victoria Land. They are believed to be caused by hydrostatic pressures generated through progressive freezing of solute-rich water beneath the lake-ice cover during winter. Lake-ice blisters in the study area differfrom icing blisters described from the northern hemisphere. The latter are caused by hydraulic pressures and are found at locations such as river beds or spring sites on sloping terrain. The Antarctic lake-ice blisters reflect the occurrence of dry-based perennially frozen lakes with high salt contents in an extremely cold and arid environment.