Geology and sedimentary facies of the Pliocene succession of the Baronia Mountains (Ariano Basin, southern Italy)

An up to 1500 m-thick clastic succession, the late Zanclean Baronia Synthem, has been analysed in detail in the Ariano wedge-top Basin (southern Apennine, Italy). In the Baronia Mountains the studied sediments are well exposed and laterally mappable due to young uplift and exhumation and rest unconformably on a complexly deformed pre-Pliocene substratum formed by Triassic to Miocene allochthonous units. The Baronia Synthem has been resolved into seven facies associations that are representative of distinct fluvial, deltaic, nearshore and offshore depositional environments and can be grouped into lowstand, transgressive, and highstand systems tracts. Using an integrated approach comprising original geological field mapping at 1:10,000 scale, conventional sedimentary facies analysis and a sequence stratigraphic approach, this paper provides a detailed description and interpretation of facies associations and new insights on the stratigraphic architecture and the geological history of this portion of the basin fill

Superficial and deep-seated gravity-driven deformation horizons within basinal succession: the case study of Maiolica Formation, Gargano Promontory, Southern Italy

Gravitational phenomena on the paleoslope of continental margins play a significant role both in redistribution of sediment and formation of new structural features within sedimentary basins worldwide. Mass-transport deposits (MTDs) represent important heterogeneities within the succession and occur on various scales (tens of centimetres to hundreds of metres). Small- to medium-scale MTDs (up to tens of meters) act as layers of different petrophysical properties, whereas large-scale MTDs (tens to hundreds of meters) form both stratigraphic and structural discontinuities (faults, thrusts, erosional surfaces, dykes or injections) within the succession. The Maiolica Formation, Early Cretaceous deep basinal succession cropping out in Gargano Promontory of Southeast Italy is represented by undisturbed intervals of flat-lying thin-bedded, cherty micritic limestone interstratified with intervals of lithologically similar, but structurally distorted beds. For this reason, the studied outcrops provide a good opportunity to characterize the geometry and the internal deformation of small- and medium-scale carbonate MTDs. At the outcrop scale, small- to medium-sized MTDs can be simply identified as sheets of deformed strata alternated with packages of undeformed beds. However, several observed features such as folded stylolites with radially oriented peaks within some of these deformed packages and the presence of large vertical clastic-dyke-like bodies in the succession suggest that some of these deformed packages represent deep-seated basal gliding horizons of large-scale MTDs. In this study, we present MTDs on two different scales that have a crucial influence on the evolution of slope to basinal successions. Moreover, we define the features that distinguish superficial MTDs from the deep-seated gravity-driven deformation horizons within basinal carbonates

Evolution of the Gelasian (Pleistocene) slope turbidite systems of southern Marche (Peri-Adriatic basin, central Italy)

Examples of slope channels and canyons being diverted by structurally related sea-floor topography are commonly found both on the modern seabed and in the subsurface, in deep-water fold and thrust belts but their depositional histories have rarely been documented using examples from outcrop. The synthesis of outcrop (original geological field mapping at 1:10,000 scale) and subsurface data sets from the early Pleistocene stratigraphic succession of the Peri-Adriatic basin provides a window into the overall evolutionary pattern of large intraslope turbidite systems that, during the Gelasian (2.58–1.80 Ma), shed Apennine-derived clastic sediments into the adjacent deep-water basin. Trends from mapping and paleocurrent indicators converge to indicate that the sea-floor bathymetric expression of a thrust-related anticline, the north-trending Jesi-Nereto-Zaccheo structure, likely influenced the downslope transport direction of gravity flows and sediment dispersal pattern. During early and middle Gelasian time, coarse-grained turbidite deposition occurred on the western flank of the intraslope anticline by westerly sourced, northward-flowing turbidity currents, indicating that the opposing sea-floor topography was sufficient to cause the diversion of turbidite systems, forcing them to travel near parallel to the east-facing regional paleoslope for significant distances. By very late Gelasian time, the intraslope accommodation space on the western flank of the anticline had filled and turbidites were dispersed through dip-oriented conduits incising across the crest of the underlying structure

Submarine slope degradation and aggradation and the stratigraphic evolution of channel-levee systems

Two seismic-scale submarine channel–levee systems exposed in the Karoo Basin, South Africa provide insights into slope conduit evolution. Component channel fills in a levee-confined channel system (Unit C) and an entrenched channel system (Unit D) follow common stacking patterns; initial horizontal stacking (lateral migration) is followed by vertical stacking (aggradation). This architecture is a response to an equilibrium profile shift from low accommodation (slope degradation, composite erosion surface formation, external levee development, sediment bypass) through at-grade conditions (horizontal stacking and widening) to high accommodation (slope aggradation, vertical stacking, internal levee development). This architecture is likely common to other channel–levee systems

Inside baleen: Exceptional microstructure preservation in a late Miocene whale skeleton from Peru

Exceptionally preserved delicate baleen microstructures have been found in association with the skeleton of a late Miocene balaenopteroid whale in a dolomite concretion of the Pisco Formation, Peru. Microanalytical data (scanning electron microscopy, electron probe microanalysis, X-ray diffraction) on fossil baleen are provided and the results are discussed in terms of their taphonomic and paleoecological implications. Baleen fossilization modes at this site include molding of plates and tubules, and phosphatization. A rapid formation of the concretion was fundamental for fossilization. We suggest that the whale foundered in a soft sediment chemically favorable to rapid dolomite precipitation, allowing the preservation of delicate structures. Morphometric considerations on the baleen plates and bristles coupled with the reconstructed calcification of the latter permit speculation on the trophic preferences of this balaenopteroid whale: the densely spaced plates and the fine and calcified bristles provide evidence for feeding on small-sized plankton, as does the modern sei whale

Stratigraphic framework of the late Miocene Pisco Formation at Cerro Los Quesos (Ica Desert, Peru)

The enormous concentration of marine vertebrates documented within the Pisco Formation is unique for Peru and South America and places this unit among the prime fossil Lagerstätten for Miocene to Pliocene marine mammals worldwide. In order to provide a robust stratigraphic framework for the fossil-bearing locality of Cerro Los Quesos, this study presents a 1:10,000 scale geological map covering an area of about 21 km2, a detailed measured section spanning 290 m of strata, and a refined chronostratigraphy for the studied succession well constrained by diatom biostratigraphy and high-resolution 40Ar/39Ar isotopic dating of three interbedded ash layers. Within the apparently monotonous, diatomite-dominated sedimentary section, the Pisco Formation has been subdivided into six local members, with stratigraphic control over the different outcrops facilitated by the establishment of a detailed marker bed stratigraphy based on fifteen readily distinguishable sediment layers of different nature

ToSCAN -Turbidity currents in Submarine CANyons

Turbidity currents at continental margins are subaqueous density flows, in which the suspension of sediments in seawater produces a water-sediment mixture that is denser than the ambient seawater and hence flows downslope due to gravity along the seafloor. These currents carve submarine canyons in the continental slopes and deliver sediments to the abyssal plains. Deposits from turbidity currents are notably known for being significant hydrocarbon-rich and other minerals reservoirs. Turbidity currents also represent a natural hazard for the growing offshore industry as even small currents can damage the oil and gas pipelines and undersea telecommunications cables scattered on the seafloor (see the review of Meiburg and Kneller, 2010). Understanding the dynamics of such gravity currents is thus crucially needed. Until now the different scenarios that have been envisaged to explain the geological and geophysical observations on turbidity currents rely on qualitative models. There is no physical model for turbidity currents flowing down complex and erodible topographies. We know that particulate gravity currents flowing horizontally in a fixed V-shaped valley are progressively thinner and deposit predominantly in the centre of the valley compared to its flanks (Monaghan, Mériaux and others, 2009a & 2009b). However we do not know what is the influence of slopes on the deposition, and under which conditions erosion competes with deposition in a V-shaped valley. We know that any current consisting of multiple particles of the same density results in deposits that are vertically stratified with the coarser particles more frequent at the base, and whose grain size thins with distance from the source (Garcia, 1994), but we still do not really understand the particle-particle interactions within those currents (Mériaux and Kurz-Besson, 2012). Furthermore, few turbidity currents in the ocean have provided evidence of their capacity to damage structures laid on the seafloor but there has been no quantification of the forces exerted onto fixed or movable bodies by particulate gravity currents flowing along complex geometries such as a sloping V-shaped valley. Such questions require to be tested by physical and numerical models. ToSCAN will develop laboratory and numerical models of turbidity currents. In particular we will perform experiments in sloping V-shaped valleys, evaluate the forces on fixed/movable objects exerted by the impact of turbidity currents, and assess the erosional power of currents on pre-existent deposits. The laboratory experiments will be run in parallel with three-dimensional numerical simulations based on the Smooth Particle Hydrodynamics (SPH) method. The experiments and simulations, which we propose to carry out in this application, are all original and innovative. The findings will be compared with modern and ancient natural analogues including canyons of the Portuguese Margin (São Vicente, Lagos, Portimão), and the ancient outcropping turbidity deposits of the Southwest Iberia (e.g. Costa Vicentina, Portugal). Our analogue and numerical modelling will provide a framework to advance our understanding of 1) the characteristics of the deposits produced by turbidity currents flowing down an inclined V-shaped valley, 2) the conditions for erosion and deposition during a turbidity current event in a V-shaped canyon, and 3) the extent to which turbidity currents can damage or move any solid objects within their path. This study will be a key to the understanding of the complex geomorphology of the Portuguese canyon system as well as ancient turbidity deposits as our results will provide tools to interpret deposits resulting from turbidity currents. This study will also be beneficial to the offshore industry as we provide a reliable evaluation of the risks for pipelines and telecommunications cables when run over by turbidity currents. The research team has been framed to meet the challenges set for this project with a unique group of Portuguese and international experts in analogue and numerical modelling, and in geology and marine geology disciplines

Off-shelf sedimentary record of recurring global sea-level changes during the Plio-Pleistocene: evidence from the cyclic fills of exhumed slope systems in central Italy

The markedly cyclic sedimentary successions of four late Pliocene to early Pleistocene slope turbidite systems exposed in eastern central Italy have been resolved into 31 high-frequency sequences. Chronological constraints from biostratigraphy and magnetostratigraphy indicate that these successions form a composite, partially overlapping stratigraphic record and sequence-bounding surfaces can be convincingly correlated with glacial oxygen isotope stages G2–60 (c. 2.65–1.7 Ma) inclusive. The studied successions, therefore, preserve an extraordinary and legible record of recurring, orbitally dictated glacio-eustatic sea-level fluctuations and provide an unprecedented opportunity to examine the deep-water sedimentary response to such high-frequency changes from an outcrop perspective