11 research outputs found
Linking shelfal 'turbidites' to their feeding system: the Monastero Fm. (eastern Tertiary Piedmont Basin)
No full textThough underappreciated in the sedimentary record, there is growing evidence that water- sediment mixtures generated at river mouths consequently to high-discharge events can transfer significant sediment volumes to deep-water via a range of flow types, referred to as hypo-homo-hyperpycnal flows. Identification of these deposits is difficult due to their resemblance to some classical turbidite facies, thus requiring accurate facies analysis.This work focuses on the facies analysis of a ca. 1100 m-thick pile of turbidites belonging to the Monastero Fm. (MF), which were deposited adjacent to coeval Gilbert-type fan-delta conglomerates (Savignone Conglomerates Fm.; SCF) as a part of the Rupelian-early Chattian fill of the eastern Tertiary Piedmont Basin (TPB; Northwest Italy).The MF consists of an apparently monotonous succession of thin-bedded sandstone-mudstone couplets with a sand/mud ratio >1 intercalated by erosive-based amalgamated beds-sets of sandstones and conglomerates a few-tens of metres-thick. The thin-bedded component of MF is dominant, representing about 70% of the total thickness of the studied section, and show a range of features which hardly fit into a turbidite depositional model. The majority of sandstone beds show erosional wavy bases and begins with either coarser basal lags or a thin inversely graded division, passing upward to two or more inversely-normally graded lamina sets separated each other by mud-drapes containing abundant phytoclasts. Typically, the top of these sandstone beds shows a variety of sedimentary structures (cross, trough-cross and hummocky lamination) and is capped by cm-thick heterolithics characterized by a range of flaser to lenticular bedding. In the lower part of MF, presence of symmetric ripple-marks ornamenting sandstone bed tops and articulated lamellibranch valves suggests deposition above the wave base level and short sediment routing.On the other hand, the thicker-bedded component of MF consists of amalgamated coarse-grained sandstones in which mud-draped scours, traction carpets, mud-chips and conglomeratic lags are suggestive of deposition from a range of hyper-concentrated to high-density flows transferring most of their load down-dip.The stratigraphic and lateral relationships of these two contrasting facies associations, along with their characters, suggest that the MF can be interpreted to reflect deposition in the pro-delta of the adjacent SCF system. In this view, the thin-bedded component of MF would represent the product of ‘background’ deposition by a range of hypo-homo-hyperpycnal flows generated at river mouths, whereas the coarser amalgamated counterpart likely represents pro-delta lobes
Facies architecture of alluvial fan systems: insights from the Early Permian Orobic Basin (North Italy)
No full textThe Lower Permian continental succession of central Southern Alps (Italy) comprises a number of volcaniclastic facies, ranging from alluvial fans to playa-lake sediments, deposited in a narrow, fault-controlled basin (Orobic Basin, OB) under hot, semi-arid climate conditions. Such deposits are formally known as Pizzo del Diavolo Formation (PDV). Although most sectors of the OB have been the subject of a number of recent studies, depositional and evolutionary models have been proposed for its central part only. This work presents new data from the marginal areas and proposes a more detailed and integrated view of the articulated depositional setting of this 50 km long graben.In the north-western sector of the OB (Pizzo dei Tre Signori massif), wedge-shaped units of crudely bedded conglomerates (100’s of metres thick) grade downstream (south-eastwards and eastwards) into pebbly sandstones and interfinger with heterolithic deposits and dark mudstones. The eastern sector of the OB (Lago di Barbellino area), on the contrary, is characterised by thick coarsening-upward successions of dark mudstones, heterolithics and well-bedded coarse sandstones interfingering south-eastwards with massive conglomerates and amalgamated pebbly sandstones hosting isolated gravel-filled channels. In both areas, conglomerates are either massive, planar or cross-bedded and may be interpreted as mass-flows, poorly confined flows, or rarer high-energy channel deposits in a high-discharge, likely seasonal alluvial fan system. Amalgamated sandstones and thin-bedded heterolithic facies are characterised by the preservation of climbing, current and wave ripples, water-escape structures, mud-cracks, mud-chip lags, rare raindrop prints, burrows and vertebrate traces. These features suggest rapid vertical aggradation driven by sheet-flood events and the post- flood reworking in a floodplain environment and/or at the margins of shallow ephemeral lakes. Mudstone-dominated successions locally host continental carbonates (stromatolites, oncoids, groundwater calcretes), likely recording the recurring temporary development of relatively long-lasting palustrine conditions.The new data (geological maps, stratigraphic logs, thin sections) have been integrated in the existing OB’s central sector model providing additional information about the distribution, geometry and facies architecture of its fringing conglomerate wedges, as a whole. Compositions of conglomerates and coarse sandstones clearly indicate different source areas for the alluvial fan systems of the two sectors. Conglomerates dominated by volcanic lithics (Val Sanguigno Conglomerates) typically occur at the southern margin, constituting a fairly continuous, mainly alluvial fan belt connected to extensive sandflats. At the northern and north-western margin, conglomerates are generally thicker and richer in quartz and metamorphic lithics (Ponteranica, Monte Aga and Val Vedello Conglomerates). There, compositional differences among individual fan systems may be evident, indicating the presence of heterogeneous sediment source areas with similar, but different, outcrops. In addition, in the northern conglomerate belt, debris flow deposits are common, which may indicate steeper gradients or greater margin instability. Finally, the northern conglomerates interfinger with finer grained floodplain or palustrine deposits not only towards the basin centre but also laterally (in some instances), suggesting they formed a set of locally non-coalescent fans
Complexity of geothermal systems in wedge-top basins: Insights from a 3D geological model of the Tertiary Piedmont Basin, NW Italy
No full textForeland and wedge-top basins host geothermal systems, in which the nature and architecture of reservoir units, heat sources, and fluid circulation result from a complex tectonic evolution. However, the relationship between tectonics and local geological processes (e.g., sediment dispersal and fracturing), is often not obvious in wedge-top basins, hindering the exploration of their geothermal resources. To investigate the multiscale tectonic-geothermal relationship, we focus our study on the Tertiary Piedmont Basin (TPB), a wedge-top basin formed on the Alps-Apennines junction (northwest Italy). The geometry and thermal structure of the region arise from the interaction between the Alps and Apennines, including processes such as slab break-off, mantle upwelling, and orogenic collapse. The basin fill is up to 6 km-thick and characterized by several unconformity-bounded clastic units, encompassing shelf to deep-water depositional
settings. Their spatial arrangement reflect major depocenter shifts and structural regime transitions. The presence of several thermal springs, local high geothermal gradients (>80 °C/Km), and moderately high surface heat flux suggest a deep groundwater circulation,
most likely within the highly fractured Alpine basement rocks. We present a conceptual basin-scale 3D model of the reservoir and overlying sealing sedimentary cover, implemented through the analyses and integration of different geological/geophysical data (e.g., seismic reflection lines, structural and petrophysical data), along with a synthesis of the main tectonic events that affected the basin. This model helps unravel possible heating mechanisms and circulation of the geothermal waters in the TPB and the applied workflow can be used on analogue basins to estimate their geothermal potentia
Unexpected thermal history of a syn-collisional basin revealed by geo- and thermochronology: the case of the Tertiary Piedmont Basin (Western Alps, Italy)
No full textBasin topography and depositional styles controlled by collisional tectonics in the Alps-Apennines junction (Tertiary Piedmont Basin, NW Italy)
No full textThe field trip illustrates the changes in the late Eocene-Miocene depositional systems filling the Tertiary Piedmont Basin in response to major palaeogeographic reorganizations linked to the evolution of the Alpine-Apennine tectonic junction. During days 1st-2nd-3rd the field trip aims to show some key outcrops of the southwestern part of the basin, where Tertiary sedimentary units unconformably cover the basement of the Ligurian Alps. During days 4th-5th the most significant outcrops of the upper Eocene-Lower Miocene sequence are shown covering the Ligurian Units of Northern Apennines in the Alps-Apennines tectonic knot. Several depositional systems are here examined, including alluvial, marginal marine, shelf, intra-slope, and basin-plain turbidites. Outcrop observations are integrated with photogrammetric models and seismic images from the time-equivalent buried systems within the study area. Topics covered in the guide include: 1) relationships between morphostructural elements and origin of sequence boundaries driven by relative sea level falls vs. hinged-margin drowning unconformities driven by hinged accommodation on oversteepened shelf margins; 2) morphologies of deep-water erosion; 3) controls of the basin morphology on the development of turbidite facies and architecture; 4) turbidite petrography and its implication on origin and source of mud-grade sediments; 5) implications for characterisation of analogue hydrocarbon plays and reservoirs
Geothermal potential of the Tertiary Piedmont Basin: structural and lithological controls
No full textThe role of mantle upwelling on the thermal history of the Tertiary‐Piedmont Basin at the Alps‐Apennines tectonic boundary
No full textThe Tertiary Piedmont Basin (NW Italy) is an episutural basin that developed from the late Eocene on the Alps–Apennines tectonic junction. Several coeval geodynamic processes, including the loading and exhumation of the Western Alps, the outward migration of the Apennine accretionary wedge and the opening of the Liguro-Provençal rift basin, controlled the basin evolution. We integrate fluid-inclusion microthermometry, low-temperature thermochronology and burial history with numerical modelling to constrain the paleo-geothermal gradients required and evaluate the mechanisms that governed the basin thermal history. Apatite fission-track and (U-Th-Sm)/He
analyses of the basal late Eocene turbidites show reset ages of ~25 Ma and ~20 Ma, respectively which require temperatures to have been > 120 °C. Homogenization temperatures up to ~130 °C from fluid inclusion analyses from authigenic minerals confirm the thermochronometric data, supporting a significant post-depositional heating in the lower sequence of the basin. Stratigraphic reconstructions and decompaction of the basin fill indicate that the maximum burial experienced by the basal strata at 25 Ma is 2.3 ± 0.1 km, which is not sufficient to reset the AFT thermochronometric system when applying a typical geothermal gradient (~20-30 °C/km). An elevated geothermal
gradient of 45 ± 5 °C/km is thus necessary to explain the thermochronometric dates and the elevated thermal signature at shallow depths. 2D numerical simulations indicate that such an elevated paleogeothermal gradient can be best explained by mantle upwelling, consistent with crustal thinning caused by the inception of the Liguro-Provençal rift basin and related outward migration of the Alpine and Apennine fronts during the Oligocene
Geological characterization of the Tertiary Piedmont Basin geothermal system: new insights from structural and stratigraphic analyses
No full textThe Tertiary Piedmont Basin (TPB) in northwest Italy is a wedge-top basin developed during Eocene—Pliocene times in the Alps-Apennines tectonic junction. It accommodates, on average, 3 km of clastic sedimentary units with significant lateral facies variations, and several basin-scale unconformities tectonically-controlled. The basin experienced deformation under markedly different tectonic regimes, developing long-lived kilometric structures that affected both the sedimentary successions, and the underlying metamorphic rocks of the Ligurian Alps. The presence of several thermal springs, relatively high surface heat-flow, and locally high geothermal gradient in the TPB, suggests a deep groundwater circulation and heating most likely in a reservoir hosted within the Alpine metamorphic rocks, i.e., the basement.
The geothermal system of the basin is not fully understood, since it still lacks a comprehensive and detailed geological/geophysical model of the basin-basement present-day structure. Aiming to fulfill this gap, this study shows structural analyses performed in the TPB and its Alpine basement at different scales through field-based characterizations, Digital Outcrop Model-based fracture mapping, and seismic interpretation. The integration of these structural results coupled with the spatial distribution of the basement and overlying sedimentary cover, enables a preliminary evaluation of potential reservoir or seal units in the geothermal system. These outcomes provide an adequate conceptual model to better understand the geothermal systems of the TPB, and other systems in analogue settings, having geodynamic peculiarities like slab switches or brake-off
Channel belt planform (low vs. high sinuosity) and behaviour (aggradational vs. laterally migrating) of turbidite channel-levee deposits: insights from the spectacularly exposed Tachrift Turbidite System (Taza-Guercif Basin, Late Tortonian, NE Morocco)
No full textAbschlussbericht zum Modellprojekt des BMA "Beschäftigungs-/Integrationsprojekte (-firmen, -betriebe, -abteilungen)": A. Zusammenfassungen und Empfehlungen; B. Abschlußbericht
No full text"Beschäftigungs-/Integrationsprojekte (-firmen, -betriebe, -abteilungen) zur Eingliederung schwerbehinderter Menschen in das Arbeitsleben." Abschlussbericht der wissenschaftlichen Begleitung zur Arbeit der Modellprojekte im Auftrag des Bundesministeriums für Arbeit und Sozialordnung; Teil A: Zusammenfassungen und Empfehlungen, Teil B: Abschlussbericht (Begleitforschung)
