1,721,080 research outputs found
Sequence stratigraphy of a lowstand prograding complex, middle-upper Pliocene Ariano Unit, Potenza Basin (southern Apennines, Italy)
No full textThe depositional architecture and the sequence stratigraphy interpretation of middle-upper Pliocene coarse-grained deltas, forming the best-exposed part of the Potenza Basin succession (southern Italy), are discussed in this study. The data document that high-frequency glacio-eustatic sea-level changes and tectonic uplift were distinctive elements on the control of the sedimentary evolution of an Apenninic ‘satellite’ basin. The studied succession forms a lowstand prograding complex (LPC) representing the lowermost element of a 3rd-order depositional sequence, known as Ariano Unit, middle-late Pliocene in age. During the ensuing relative sea-level lowstand, vertical-stacked coarse-grained Gilbert-type braid deltas and coeval shoreface successions prograded several kilometers basinward forming the LPC.
The LPC succession consists of coarse-grained prevalent sediments, generally shoaling upwards from offshore mudstone containing pro-delta turbidites to conglomeratic delta foresets and topsets, with laterally coexisting sandstone-dominated shoreface facies. Along the vertical-stacked succession, a key surface of marine transgression, divides the succession into two 4th-order deltaic sequences (P1 and P2), whilst internal changes on the depositional architecture indicate lower-rank composing minor sequences or stratal units.
The overall stratigraphy of the 3rd-order Ariano depositional sequences suggests an initial relative sea-level lowstand and a successive rise that generated a major marine flooding surface. A relative sea-level fall followed, resulting in widespread exposure and incision.
The internal arrangement of the 4th-order sequences indicates the occurrence of minor relative oscillations (up to the 5th-order) producing distinct deltaic units. The 5th-order units are reciprocally arranged in ‘attached’ and ‘detached’ imbricate-stacked braid-deltas, recording a long stage of sea-level relative lowering, punctuated by short rises and alternated falls of different amplitudes.
The interpretation of the depositional architecture of the lowermost part of the Ariano Unit demonstrates that uplift persistently controlled the sedimentation during sequence P1, affecting differently the western margin of the Potenza Basin
The influence of substrate lithology in the depositional architectures of coarse-grained Gilbert-type deltas (Pliocene Potenza Basin, Southern Italy).
No full textA geological profile across the Pleistocene Catania Plain foredeep basin (eastern Sicily).
No full textSedimentary features of incipient beachrock deposits along the coast of Simeto River Delta (eastern Sicily, Italy).
No full textThe occurrence of beachrock outcrops along the coast of the Simeto River delta, the greater watercourse of Sicily, is described in this work. The delta is located into a microtidal context, where the wave energy action prevails on the coastal depositional processes as controlling factor. The deposits are constituted by discontinuous levels, 1-1,2 meters thick of very well cemented arenitic sediments of recent age.
The present human-induced changes of the precarious equilibrium regulating the sediment supply to the coast during last century, in the high part of the Simeto River drainage basin, caused strong erosion, with marked coastal land-loss examples. Because of that, the studied horizons have been quickly exposed from their original cover. As a consequence, they have been comprised into a vadose-freatic horizon, affected by percolation of meteoric and marine waters. Precipitation of calcite- and aragonite-rich solutions has determined their rapid cementation. For this reason, these discontinuous levels cropping out along the southern sector of Plaia di Catania beach are considered as recent incipient beachrocks sensu Kneale and Viles (2000).
Beachrock formation, principally due to strong erosional rates characterising the Catania coastal plain, is also attributed to the high tectonic uplift rate, which has affected the whole eastern margin of Sicily, at least since the Upper Pleistocene
Studio Stratigrafico e Sedimentologico del delta del Fiume Simeto e del settore centro-orientale della Piana di Catania (Sicilia orientale). Tesi di Dottorato
No full textTHE RECORD OF SHORT-TERM TIDAL CYCLES IN ANCIENT MIXED SILICI-/BIOCLASTIC DEPOSITS: EXAMPLES FROM PLIOCENE TO PLEISTOCENE MICRO-TIDAL BASINS OF SOUTHERN ITALY.
No full textA facies-based depositional model for ancient and modern, tectonically-confined tidal straits
Full text linkModern and ancient tidal straits are the least well understood of all tide-dominated depositional systems. In order to provide an increased understanding of these systems, a facies-based depositional model is assessed by comparing multibeam surveys of three present-day tidally-dominated seaways with a number of superbly exposed Neogene-to-Quaternary strait-fill successions of Calabria (south Italy).
The model points out the existence of four depositional zones, laterally-adjacent from the narrowest strait center to its terminations, distributed along symmetrical or asymmetrical seaways.
These zones, whose signature is recorded in four facies associations in the Calabrian tidal straits, are: (i) the strait-center zone, associated to the tidal current maxima and where sediments are scarce or absent; (ii) the dune-bedded zone, where sediments form dune complexes due to tidal flow expansion; (iii) the strait-end zone, where currents decelerate accumulating thinly-bedded, fine-grained deposits; (iv) the strait-margin zone, where sediment massflows descend tectonically-active, steep margins towards the strait axis.
In ancient, tectonically-confined, narrow seaways, these facies generate a distinctive deepening-upward vertical succession, where tidal currents are the dominant process in the sediment distribution
Reperimento e compatibilità di sedimenti prelevati in aree continentali ai fini di azioni di ripascimento costiero: l’esempio dell’entroterra ionico della Basilicata
No full textLa costa ionica della Basilicata è caratterizzata dalla presenza di una estesa spiaggia, costituita da un arenile formato da sedimenti sabbiosi e subordinatamente ghiaiosi, che derivano dalla ridistribuzione dei depositi riversati da diversi corsi d’acqua, da parte del moto ondoso e del drift litoraneo. Nelle ultime decine di anni, la modificazione di importanti equilibri ad opera sia di interventi antropici direttamente sulla costa ma anche nei settori medio-alti dei bacini di drenaggio fluviali che sottendono la costa, concomitanti alle recenti e repentine variazioni climatiche in corso, hanno determinato un forte stato di arretramento costiero del litorale ionico, con pesanti conseguenze sugli aspetti naturalistici e turistici che lo caratterizzano.
Le esperienze di interventi su litorali in arretramento che derivano dall’attività di salvaguardia sia in campo internazionale, ma soprattutto attuate nelle ultime decine di anni lungo le coste del territorio italiano, hanno dimostrato come l’intervento più efficace per ripristinare, anche se in parte, lo stato dei luoghi di un litorale in forte erosione, è quello del ripascimento costiero, il versamento, cioè, di volumi di sedimenti derivanti da un area sorgente, direttamente sull’arenile.
In questo articolo vengono discusse alcune problematiche relative i) al reperimento di volumi di sedimento sufficienti ad azioni di ripascimento nell’entroterra delle aree costiere di intervento, ii) a compatibilità sia granulometrica che mineralogica tra i sedimenti derivanti da un area sorgente e l’arenile di destinazione, iii) alle modalità di monitoraggio e mantenimento dei sedimenti riversati lungo una spiaggia in arretramento durante e dopo la messa in opera dell’azione di ripascimento costiero
Il delta del Fiume Simeto e la Piana di Catania: uno scrigno di storia geologica recente.
No full textShort-Term Assessment of Retreating vs. Advancing Microtidal Beaches Based on the Backshore/Foreshore Length Ratio: Examples from the Basilicata Coasts (Southern Italy)
Full text linkA straightforward conceptual method is proposed to quantitatively assess the seasonal-scale tendency of retreatment or advancement on microtidal beaches by using the backshore/foreshore length ratio. This method is based on measuring the cross-shore profile of a beach when it passes through the “transitional state” that separates the high-from the low-energy season, period during which the morphological characteristics of the beach tend to its equilibrium profile. In order to obtain real measurements of backshore (B) and foreshore (F), the definition of the limits bounding these two important components in subaerial beaches is reviewed and discussed. The approach based on the measurement of the B/F length ratio assumes that foreshore and backshore have equivalent lengths in beaches that approximate to their state of morphodynamic equilibrium (B/F ~ 1). A backshore length exceeding the foreshore length is indicative of a state of beach recession, with a B/F length ratio > 1. When the foreshore length is greater than the backshore length, the shoreline is advancing or, alternatively, it is developing in a state of morphological confinement, i.e. due to the presence of a sea cliff, with a B/F < 1. This practical method is then tested against 36 sand and gravel microtidal beach profiles measured along the coasts of Basilicata, in southern Italy. The various “beach states” are summarised into seven classes (I-VII), each identified from specific value intervals of the B/F length ratio
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