Donatella Mellere - Academia.edu (original) (raw)

Papers by Donatella Mellere

Marine and Petroleum Geology, Nov 1, 2017

Marine geology data show that canyon heads can be the site of depositional processes and furnish ... more Marine geology data show that canyon heads can be the site of depositional processes and furnish the details of the geometry of their geomorphic elements. Canyon heads are usually floored by sediment with a prevailing coarse-grained nature and their sampling is very difficult thus preventing the characterization of the facies of their infill. Lithological and facies information is however available through outcrop studies. In this paper, we integrate modern seafloor and outcrop data to characterize the architecture of depositional canyon heads in tectonically active continental margins with a narrow shelf. The modern examples are located along the northeastern Sicilian margin (Milazzo and Niceto canyonhead systems), whereas the ancient one, Pliocene in age, is located onshore, along the Ligurian coast (Ventimiglia canyon-head system). The modern Milazzo canyon head is located at the coastline and has a steep slope. The flanking deposits are equivalent to the oldest Gilbert delta foresets of the Ventimiglia canyon head as the delta progrades directly into the upper slope. A deeply entrenched channel and a large chute mark the mostly erosional area directly facing the mouths of the rivers that enter the Milazzo canyon head. Laterally, the upper part of the foresets slope is characterized by a bulge with swales and ridges topography. These geomorphic elements are interpreted to be formed by debris flows and turbidity currents as suggested by the upper part of the Ventimiglia foresets, where chaotic, massive or graded deposits are observed. The swales and ridges topography gradually disapper downslope; this area is dominated by turbulent processes due to flow expansion from a confined to a more unconfined setting. An high turbulent flow environment is also confirmed by the formation of plunge pools, due to hydraulic jump, at the foresets-toesets transition. Similar features in the outcrop are infilled by bedsets facies with grain-size coarser than the eroded surroundings. The modern Niceto canyon head is connected landwards to a delta system that stretches across a 1 km wide shelf. Channelized delta distributaries are similar to the topset strata of the youngest deltas of the Ventimiglia canyon head. Channels are up to 200 m wide and 50 m deep and show axial bedform trains confirming that large scale trough cross beds are an important facies of channel infill. Wave reworking in the upper part of the topsets is also suggested by both the modern and outcrop data. Our work shows how the nature of the infill and the depositional processes at the canyon heads are dependent on the shelf width and can give hints on the degree of evolution of the canyon itself. In addition, our work shows how the location and character of river entry points is important in dictating lateral facies variations within canyon heads.

Rift-related faults often display non-rectilinear geometries, which have been interpreted as (i) ... more Rift-related faults often display non-rectilinear geometries, which have been interpreted as (i) the result of linkage between different fault segments-developed during a single or more tectonic phases-, (ii) as curvilinear faults due to gravitational collapse, (iii) as inherited basement trends. Disentangling these processes is generally difficult, with multi-phase rifting and reactivation of preexisting structures being the most intuitive and commonly adopted explanations.

Geological Society, London, Special Publications, 2000

Basin Research, Mar 1, 2004

The complex development of the northern Crotone Basin, a forearc basin of the Calabrian Arc (Sout... more The complex development of the northern Crotone Basin, a forearc basin of the Calabrian Arc (Southern Italy), has been documented by sedimentological, stratigraphic and structural analyses.This Mediterranean-type fault bounded basin consists of small depocentres commonly characterized by a mix of facies that grades from continental to shallow marine.The lower Pliocene in¢ll of the Crotone Basin consists of o¡shore marls (Cavalieri Marl) that grade upwards into a shallow-marine to continental succession up to 850 m thick (Zinga Formation).The succession is subdivided into three main stratal units: Zinga 1, Zinga 2, Zinga 3 bounded by major unconformities.The Zinga1stratal unit grades from the Cavalieri Marl to deltaic and shoreface deposits, the latter organized into several stacked progradational wedges that show spectacular thickness changes and progressive unconformities related to salt-cored NE-trending growth folds and listric normal faults.The Zinga 2 stratal unit records a progressive and moderate deepening of the area, marked by £uvial sedimentation at the base, followed by lagoonal deposits and by a stacking of mixed bioclastic and siliciclastic shoreface units, organized into metre-scale high-frequency cycles. Deposition was controlled by NEtrending synsedimentary normal faults that dissected the basin into a series of half-grabens. Hangingwall stratigraphic expansion was compensated by footwall condensed sedimentation.The extensional tectonic regime continued during sedimentation of the Zinga 3 stratal unit. Deposition con¢ned within structural lows during a generalized transgressive phase led to local enhancement of tidal £ows and development of sand-wave trains.The tectonic setting testi¢es the generalized structural domain of a forearc region.The angular unconformity at the top of the Zinga 3 stratal unit is regional, and marks the activation of a large-scale tectonic phase linked to strike-slip movements.

Journal of Sedimentary Research, 1994

Blackwell Publishing Ltd eBooks, Apr 16, 2009

ABSTRACT La Pobla de Segur Conglomerates (Collegats Formation) represent a Late Eocene and Oligoc... more ABSTRACT La Pobla de Segur Conglomerates (Collegats Formation) represent a Late Eocene and Oligocene alluvial fan complex developed within an intermontane basin, in the south-central part of the Pyrenean Chain, to the south of the Axial Zone antiformal stack (Nogueres). The conglomerates onlap a previously deformed substratum of Mesozoic and Palaeozoic rocks. They are organized into a series of stacked wedge-shaped bodies reaching a cumulative thickness of about 3500 m. In a vertical succession, five main allogroups (Pessonada, Ermita, Pallaresa, Senterada and Antist), comprising more than 20 alluvial fan lobes have been recognized. The allogroups are distinguished on the basis of underlying major unconformity surfaces, clast composition and palaeocurrent patterns. The structural relationship between successive alluvial fan lobes and their substratum has allowed the establishment of a chronology of deformation in this thrust-controlled basin. Each of the five allogroups can be tied to a specific stage of structuring.The basal Pessonada allogroup is composed of small, local alluvial fans deposited at the southern active margin of the basin. Relationships between tectonic activity and the contemporaneous sedimentation have demonstrated a break-back thrusting sequence. The Ermita allogroup consists of units representing small fan-deltas which prograded into a shallow lake. The widespread fine-grained materials (floodbasin and lacustrine) suggest a period of initial subsidence linked to the onset of deep thrusting along the northern margin of the basin. The basinwards progradation of the polymict alluvial fan conglomerates of the Pallaresa allogroup define the third stage. Tectonic activity had shifted towards the northern margin of the basin and was characterized by the emergence of backthrusts related to the paroxysmal growth of the adjacent Nogueres structure. The imbricated system of backthrusts led to the development of a minor basin to the north, whose infill (Senterada allogroup) defines the fourth stage: alluvial units, bounded by tectonic structures, are deformed in progressive unconformities demonstrating their contemporaneous deposition with emplacement of the backthrusts. Only the youngest alluvial deposits of the Antist allogroup are not deformed and record the cessation of activity in the Nogueres Zone (fifth stage). The general north–south geometry of the Collegats Formation shows a stepwise, backfilling pattern of deposition for the allogroups. There was a northward migration of the sedimentary depocentres as a response to deep seated thrust emplacement along the northern margin. The Collegats Formation, rather than being merely post-tectonic infill, has been shown to be Late Eocene–Oligocene syntectonic deposits.

Sedimentology, Aug 1, 1999

The Campanian Cliff House Formation represents a series of individually progradational shoreface ... more The Campanian Cliff House Formation represents a series of individually progradational shoreface tongues preserved in an overall landward-stepping system. In the Mancos Canyon area, the formation consists of four, 50-to 55-mthick and 10-to 20-km-wide sandstone tongues, which pinch out landwards into lower coastal plain and lagoonal deposits of the Upper Menefee Formation and seawards into offshore shales of the Lewis Shale Formation. Photogrammetric mapping of lithofacies along the steep and well-exposed canyon walls was combined with sedimentary facies analysis and mapping of the detailed facies architecture. Two major facies associations have been identi®ed, one comprising the mostly muddy and organic-rich facies of lagoonal and lower coastal plain origin and one comprising the sandstone-dominated facies of shoreface origin. Key stratigraphic surfaces were identi®ed by combining the mapped geometry of the lithofacies units with the interpretation of depositional processes. The stratigraphic surfaces (master ravinement surface, shoreface/coastal plain contact, transgressive surface, maximum¯ooding surface and the sequence boundary) allow each major sandstone tongue to be divided into a simple sequence, consisting of a basal transgressive system tract (TST) overlain by a highstand system tract (HST). Within each sandstone tongue, a higher frequency cyclicity is evident. The high-frequency cycles show a complex stacking pattern development and are commonly truncated in the downdip direction by surfaces of regressive marine erosion. The complexities of the Cliff House sandstone tongues are believed to re¯ect changes in the rate of sea-level rise combined with the responses of the depositional system to these changes. Synsedimentary compaction, causing a thickness increase in the sandstone tongues above intervals of previously uncompacted lagoonal/coastal plain sediments, also played a role. This study of the facies architecture, geometry and sequence stratigraphy of the Cliff House Formation highlights the fact that there may be some problems in applying conventional sequence stratigraphical methods to landward-stepping systems in general. These dif®culties stem from the fact that no single stratigraphic surface can easily be identi®ed and followed from the non-marine to the fully marine realm (i.e. from the landward to the basinward pinch-out of the sandstone tongues). In addition, the effects of synsedimentary compaction and changes in the shoreface dynamics are not easily recognized in limited data sets such as from the subsurface.

GFF, Oct 1, 1996

The accuracy of the Content should not be relied upon and should be independently verified with p... more The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden.

Geological field trips, May 1, 2021

From marginal to axial tidal-strait facies in the Early Pleistocene Siderno Strait The Geological... more From marginal to axial tidal-strait facies in the Early Pleistocene Siderno Strait The Geological Survey of Italy, the Società Geologica Italiana and the Editorial group are not responsible for the ideas, opinions and contents of the guides published; the Authors of each paper are responsible for the ideas, opinions and contents published. Il Servizio Geologico d'Italia, la Società Geologica Italiana e il Gruppo editoriale non sono responsabili delle opinioni espresse e delle affermazioni pubblicate nella guida; l'Autore/i è/sono il/i solo/i responsabile/i.

Geological Society, London, Special Publications, Sep 21, 2016

Recent studies in the Middle Jurassic Bryne and Sandnes formations, primary reservoirs in several... more Recent studies in the Middle Jurassic Bryne and Sandnes formations, primary reservoirs in several fields across the Norwegian and Danish North Sea, show the widespread occurrence of tidal-influenced and tide-dominated deposits. Aalenian–Bajocian Bryne cores reflect deposition by a shoal water, tidally influenced delta onto a low wave energy tidal platform (both supratidal and intertidal) that probably occupied the majority of the Søgne Basin, a narrow rift system connected to the Central and Danish graben and transgressed from an open-marine basin, possibly located to the south. At the Bathonian–Callovian boundary, a new phase of rifting and progressive salt movements led to the deposition of the upper Bryne and Sandnes formations within an 80–100 km long composite estuarine valley. Basin tilting to the south and continued transgression resulted in tidal deltas that offlap the northern margin of the basin. The basin was fully transgressed by the end of the Callovian. From the Late Bathonian onwards, differential tectonic movements along the broadly interconnected Middle Jurassic rift basins led to a change in the transgression direction from south to north, with an open-marine basin located in the Central and Viking graben.

Sedimentology, Jun 7, 2021

Sand ridges, a common feature of modern open shelves, reflect persistent currents and sediment av... more Sand ridges, a common feature of modern open shelves, reflect persistent currents and sediment availability under recent transgressive conditions. They represent the largest bedforms in the oceans and, as such, can yield information on long-term oceanographic processes. However, there is a limited number of tidal sand ridges documented from the rock record, examples of regressive tidal sand ridges are scarce and studies describing ridges in straits are even more rare. This study analyses a Gelasian succession within a structurally controlled, tide-dominated strait in the Siderno Basin, southern Italy. The strait connected two wider basins, and accumulated sediments reworked by amplified tidal (bi-directional) currents. A series of tidal sand ridges with superimposed dunes developed close to the southeastern end of the strait, where bathymetry was deeper and flow expansion occurred. One of the best-exposed tidal sand ridges, 65 m thick, crops out along a ca 2 km long cliff. Large-scale, ESE-prograding, seaward-offlapping shingles contain sets of bioclastic-siliciclastic, coarse-grained, cross-stratified sandstones, erosionally overlying upper Pliocene shelf marls and fine-grained sandstones. Cross-strata show angular, tangential and sigmoidal foresets with compound architectures and a SSE migration, i.e. oblique to the main growth direction. Fossil content indicates open-marine conditions. The succession changes abruptly across an erosion surface to non-tidal, highly burrowed mixed siliciclastic-bioclastic fine-grained sandstones, less than 15 m thick. Documented features reflect stages of nucleation, active accretion and abandonment of an individual sand ridge, during a complete cycle of relative sea-level change. The ridge formed during a phase of normal regression, with accretion occurring during an initial highstand and the ensuing falling stage.