1,721,150 research outputs found
Carbonate channel network in the Miocene syn-rift Sardinia basins
No full textMurru M., Simone Lucia, Vigorito M. Carbonate channel network in the Miocene syn-rift Sardinia basins. In: Géologie Méditerranéenne. Tome 28, numéro 1-2, 2001. Anatomy of Carbonate Bodies / Anatomie des corps carbonates. International Meeting / Colloque international. Marseille, 9-12 mai 2001, France, sous la direction de Marc Floquet, Jérôme Hennuy et Jean-Pierre Masse. pp. 133-137
Displaced/re-worked rhodolith deposits infilling parts of a complex Miocene multistorey submarine channel: a case history from the Sassari area (Sardinia, Italy)
No full textIn the Sassari area (north-western Sardinia, Italy), the Miocene Porto Torres sub-basin sequences represent the complex multistorey mixed carbonate-siliciclastic submarine feature called the Sassari Channel. During the late Burdigalian–early Serravallian, repeated terrigenous supplies from uplifted Paleozoic crystalline substrata fed the Sassari Channel system by means of turbidity and locally hyper-concentrated turbidity flows. Shelfal areas were the source of terrigenous clasts, but open shelf rhodalgal/foramol carbonate areas were very productive and largely also contributed to the channel infilling. Re-worked sands and skeletal debris were discontinuously re-sedimented offshore as pure terrigenous, mixed and/or carbonate deposits. Major sediment supply was introduced between the latest Burdigalian and the start of the middle Langhian, during which a large amount of carbonate, mixed and siliciclastic sediments reached the Porto Torres Basin (Sassari Channel I). Contributions from shallow proximal source areas typify the lower intervals (Unit A) in marginal sectors of the channel. Upward, these evolve into autochthonous rhodolith deposits, winnowed by strong currents in relatively shallow well lit settings within a complex network of narrow tidally-controlled channels (Unit D) locally bearing coral assemblages. Conversely, re-sedimented rhodoliths from the Units B and C accumulated under conditions of higher turbidity. In deeper parts of the channel taxonomically diversified rhodoliths point to the mixing of re-deposited skeletal components from different relatively deep bathmetric settings. In the latest early Langhian, major re-sedimentation episodes, resulting in large prograding bodies (Unit D), triggered by repeated regression pulses in a frame of persistent still stand. During these episodes photophile assemblages dwelled in the elevated margin sectors of the channel. A significant latest early Langhian drop in relative sealevel resulted in impressivemass flows involving early cemented channel-margin and levee blocks and culminated in the formation of major erosional surface (ER-E). Such events seemingly correlatewith the long-termglobal cooling trend of the mid-Miocene climatic transition. Episodes of middle Langhian re-sedimentation concluded with the channel abandon phase afterwhich newerosive episodes followed. Overall, this led to a shift in the Sassari Channel II, with phases presumably started during the earlymost Serravallian, subsequent to the major sealevel drop at the Langhian–Serravallian boundary
Anatomy of a submarine channel system and related fan in a foramol/rhodalgal carbonate sedimentary setting: a case history from the Miocene syn-rift Sardinia Basin, Italy
No full textDuring Aquitanian-Burdigalian times, thick mixed carbonate-siliciclastic successions were deposited in basins located on the grabens and half–grabens along the Oligo-Miocene Sardinia Rift Basin. Locally active tectonics, sea level variations and ecological factors combined to control the development and distribution of foramol carbonate factories as well as the remobilisation and the redeposition of carbonate sediments into the adjacent deeper areas. In the Isili Basin, foramol\rhodalgal carbonate factories developed on submerged structural highs which resulted from pre- and syn-sedimentary tectonics. These carbonate factories were periodically shaved mainly during negative sea level oscillations and the sediments removed were funnelled towards the basin through a complex submarine channel network which included a tributary belt, one main channel (Isili Channel) and the related fan. The Isili Channel is up to 1 km wide, 60–100 m deep and includes two stacked channel complexes each built up by several minor order channel-units. Complex strata geometries characterise the Isili Channel and its related architectural elements (e.g., overbank, levee, margin and channel thalweg) which also include up to 15 m high bedforms. Individual channel complexes were temporally related to individual fan systems whose spatial distribution and internal geometry were strongly controlled by the type and rate of sediment accumulation and in turn by relative sea-level oscillations. Facies associations include sandy to cobble-sized gravity flow and bottom current deposits as well as megabreccias characterised by impressive displaced and tilted blocks which resulted from major channel margin collapses. Detailed analysis has led to the reconstruction of the internal geometry and depositional architecture of these carbonate bodies and to the determination of the main controlling factors. The dimension and distribution of channel and channel-related depositional bodies have been accurately determined. This information provides a useful tool to analyse less extensively exposed analogues and to model foramol shelf to basin transitions and related channel and fan systems
Architectural patterns in a multistorey mixed carbonate-siliciclastic submarine channel, Porto Torres Basin, Miocene, Sardinia, Italy".
No full textIn the Sassari-Muros area, the analysis of extensive exposures of the Porto Torres sub-basin fill sequences have enabled a detailed reconstruction of a complex mixed carbonate-siliciclastic channel system. The exposed sequences, dated as Burdigalian-Serravalian, comprise a few kilometres wide and up to 200m thick channel complexes fringed by marly sheet deposits. Channels are erosional or mixed erosional-depositional type and show multiple, stacked, partly nested channel-fill sequences which relate to different filling phases. Individual channel-fills include sand to coble sized gravity flow deposits which are locally capped by thin-bedded, intensely bioturbated, hemipelagic marls which are related with temporary abandon of the channel, possibly in relation with sea level rise. Architectural elements recognised at outcrop comprehend distinct mid-channel, margin-levee and overbank complexes as well as sheets and drapes of marly basinal deposits. Channel-margin which are locally characterised by very complex depositional architectures which include also up to 15-20 m high lateral bars. Mid-channel complexes are commonly parallel to concave up stratified and locally exhibit minor order nested channel bodies. These erode, overlap or lie alongside each other and suggest repeated channel thalweg digressions and avulsions. Channel-fill architectures are locally complicated by the presence of megabreccias which include up to a few tens of metres high and wide displaced and\or tilted blocks. Megabreccias are commonly associated to sand injections and\or minor faults and resulted from channel margin collapses boosted by tectonics and\or by pore water overpressures generated in horizons hydrologically confined between early-cemented bed packages. Channel fill sequences include both carbonate- and siliciclastic-dominated deposits. Carbonate deposits are made up of rhodalgal calcirudites to calcarenites and include 5-20m thick well sorted rhodolith-rich pebbly bed packages as well as sets of early hardened strata. Siliciclastic deposits ranges from quarts- rich coarse pebbly\sandy to silty turbidites. These are well bedded, laminated or massive, and display different degrees of cementation. Carbonate fractions can be locally significant but the passage between the siliciclastic- to the carbonate-dominated deposits are commonly abrupt and marked by sharp erosive surfaces
Earthquake occurrence models in the short and long term for the Italian seismicity
No full textThe ETES, ERS and LTST models have been submitted to the CSEP (Collaboratory
for the study of Earthquake Predictability) forecast testing for Italy (ETH-Zurich) and locked down
to test their validity on real data in a forward way starting from August 1, 2009.This work describes three earthquake occurrence models, two in the short-(24 hour) and one in
long-term (5- and 10 year), applied to the whole Italian territory in order to assess the occurrence
probability of future (M≥5.0) earthquakes. The first model for short-term forecasts is a purely
stochastic Epidemic Type Earthquake Sequence model (ETES). The second short-term epidemic
forecast is based on a model physically constrained by the application of Dieterich rate-state
constitutive law to the earthquake clustering (ERS). The third forecast is based on a Long Term
model that considers the perturbation of earthquake probability for interacting faults by static
Coulomb stress changes (LTST). These models have been submitted to the CSEP (Collaboratory
for the study of Earthquake Predictability) forecast testing for Italy (ETH-Zurich) and locked down
to test their validity on real data in a forward way starting from August 1, 2009.CSEP testing center for ItalySubmitted1-233.1. Fisica dei terremotiJCR Journalope
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