87 research outputs found
The tectonically confined Firenzuola turbidite system (Marnoso-arenacea Formation, northern Apennines, Italy)
No full textThe Firenzuola turbidite system formed during an important
phase of thrust propagation, involving the upper Serravallian deposits
of the Marnoso-arenacea Formation (MAF). During this phase the
coeval growth of two major tectonic structures, the M. Castellaccio
thrust and the Verghereto high, played a key role, causing a closure
of the inner basin and a coeval shift of the depocenter to the outer
basin. This work focuses on this phase of fragmentation of the MAF
basin; it is based on a new detailed high-resolution stratigraphic
framework, which was used to determine the timing of growth of the
involved structures and their direct influence on sediment dispersal,
as well as on lateral and vertical turbidite facies distribution. The
Firenzuola turbidite system stratigraphy is characterized by the
occurrence of MTCs (Mass Transport Complexes) and thick sandstone
accumulation in the depocentral area, which passes to finer
drape over the structural highs; the differentiation between these
two zones increases over time and ends with the deposition of marly
units over the structural highs and the emplacement of the Visignano
MTC. According to the stratigraphic pattern and turbidite
facies characteristics, the Firenzuola System (Unit V in the works by
Muzzi Magalhaes and Tinterri) has been split into two sub-units,
namely Firenzuola I (sub-Unit Va) and Firenzuola II (sub-Unit Vb):
the former is quite similar to the underlying deposits (Unit IV), the
latter shows the main fragmentation phase, testifying to the progressive
isolation of the inner basin and a coeval shift of the depocenter
to the outer basin
THE LOWER EOCENE RODA SANDSTONE (SOUTH-CENTRAL PYRENEES):AN EXAMPLE OF A FLOOD-DOMINATED RIVER-DELTA SYSTEMIN A TECTONICALLY CONTROLLED BASIN
No full textThe lower Eocene Roda Sandstone (Figols Group, south-central Pyrenees) mainly consists of mouth bars and delta-front sandstone lobes deposited in a flood-dominated river-delta system. The deposition of these bodies was strongly controlled by an interaction between flood-dominated gravity flows entering seawater, topographic confinement and tidal currents. The Roda Sandstone is made up of six depositional sequences of different hierarchical order each of which is characterized by a basal deltaic sandstone wedge (R1 to R6) that passes upward into a siltstone and mudstone interval. Each basal deltaic sandstone wedge is composed of three types of facies association and respective facies tract (sensu Mutti 1992) that, from proximal to distal zones, are indicated as T1, T2 and T3. These three facies tracts are created by the downcurrent evolution of different types of sediment-laden stream flows entering seawater and related hyperpycnal flows. Their deposits are constituted by three different types of coarse-grained mouth bars and corresponding fine-grained delta-front sandstone lobes. The tidal influence is present in facies tract T3 in the R5 and R6 sandstone units, where the passage between flood-dominated mouth bars and the delta-front sandstone lobes occurs through intermediate facies characterized by different types of sigmoidal-cross stratification whose meaning will be discussed. The basal deltaic sandstone wedges of Roda sandstone are characterized by a progressive forestepping culminating in the R6 unit that erodes the underlying R5 unit and by an overlying backstepping unit indicated as R7. The erosive surface at the base of R6 unit is interpreted as a sequence boundary that divides the Roda Sandstone into two parts: 1) an underlying highstand system tract (HST) and falling stage system tract (FSST) (units R1 to R5) and 2) an overlying low-stand delta (the R6 unit) that passes upward into highstand mudstone through a transgressive system tract represented by the R7 unit. Pd
Foredeep turbidites of the Miocene Marnoso-arenacea Formation (Northern Apennines)
No full textThe Marnoso-arenacea Formation (MAF, Langhian-Tortonian) was deposited in an elongate, NW-stretched
foredeep basin formed in front of the growing Northern Apennines orogenic wedge (Figs. 2, 3A). These types
of deposits have always had a fundamental role in the hystory of turbidites, because a great part of the models
and facies schemes proposed in the literature have often been developed on these types of deposits. Among
foredeep turbidites, the MAF is probably the most famous, the best exposed and less structurally deformed,
due to its relatively external position within the Apenninic orogen. These characteristics have often favoured
detailed physical stratigraphy studies, such as the pioneering ones by Ricci Lucchi and his co-workers (see for
example Ricci Lucchi & Valmori, 1980).
As indicated in figure 3, an idealized transect oriented perpendicularly to the main structural axes shows that
sedimentation of a foreland region takes place in three distinct and coeval basins including: a) wedge-top
basins, characterized by alluvial, deltaic and mixed depositional systems; b) a foredeep basin,
characteristically in-filled with deep-water basinal turbidites; c) an outer and shallower ramp developed on
the passive foreland plate. The progressive thrust propagation toward the outer margin of the basin produces
a vertical superimposition of three depositional systems that, from base to top, are: (1) highly efficient
basinal turbidite systems and associated hemipelagic deposits; (2) mixed depositional systems, in which
turbidite-like bodies are deposited by poorly efficient gravity flows in a structurally confined basin. They can
be associated to prodeltaic sediments, both vertically and laterally; (3) flood-dominated deltaic systems (see
Mutti et al., 2003).
The vertical stacking pattern of the MAF, illustrated in figures 4 and 33, is characterized by same vertical
stratigraphic evolution in which at least three main depositional systems can be recognized and are represented
by Langhian to Serravallian high-efficiency basinal turbidites, Tortonian low-efficiency mixed turbidites and
shallow water Messinian euxinic shales and evaporites (Ricci Lucchi, 1978, 1981, 1986; Mutti et al., 2002a;
Roveri et al., 2003; Tinterri & Muzzi Magalhaes, 2011). The MAF, therefore, consists of a shoaling-up
stratigraphic succession, which results from the progressive closure of the foredeep due to the north-eastward
propagation of the main thrust front of the MAF. Consequently, this eastward thrust propagation has produced
a progressive uplift of the inner portions of the foredeep and a subsequent shifting in the same direction of themain depocentres. For this reason, Ricci Lucchi (1986) introduced the concepts of inner stage or basin
(Langhian-Serravallian in age) and outer stage or basin (Tortonian in age). The first one is characterized by deep
water high efficiency basinal turbidites, while the second one consists of low-efficient mixed turbidites in a
shallower and more confined basin. The passage between inner and outer stages is recorded by an important
tectonic phase (upper Serravallian in age) characterising the basal part of Unit V by Muzzi Magalhaes & Tinterri
(2010), which is time equivalent to the Firenzuola and Paretaio systems (Figs. 4 and 33).
The MAF stratigraphic succession, therefore, can be described in three stages: 1) a Langhian-Serravallian
inner basin; 2) an Upper Serravallian phase that records the transition between inner and outer basins and
3) a Tortonian outer basin (see Fig. 33). These three stages or basins are characterized by three different
facies associations related to the progressive increase, over time, of the structural control and the associated
morphologic confinement. This fact, influencing especially the erosive degree and the deceleration rate of
the turbidity currents, induces the formation of different bed types. The MAF foredeep can be considered as
a complex foredeep (as meant by Ricci Lucchi, 1986) characterized by sin-sedimentary structural highs and
depocenters related to the main thrust fronts within the MAF foredeep, which significantly control the lateral
and vertical distribution of turbidite facies (see Muzzi Magalhaes & Tinterri, 2010; Tinterri & Muzzi
Magalhaes, 2011).
Therefore, after a short and general introduction to the geology and stratigraphy of the northern Apennines,
the main targets of this field trip will be the stratigraphy, facies and processes of foredeep turbidites of the
MAF outcropping in the north-eastern Apennines, focusing especially on two specific aspects of the MAF
sedimentation: 1) the synsedimentary structural control affecting the MAF turbidites deposited in an elongate,
NW-stretched complex foredeep basin formed in front of the growing Northern Apennines orogenic wedge and
2) the vertical facies changes of the MAF stratigraphic succession (more than 4000m thick) in relation to the
progressive closure, uplift and consequent fragmentation of the foredeep due to the north-eastward
propagation of the Apennine orogenic wedge (Fig. 33)
The relationship between flood hydrograph and facies sequences of delta-front sandstone lobes produced by hyperpycnal flows
No full textRelazione tra l'idrogramma di piena e le sequenze di facies di foce (barre) e di piattaforma (lobi)
No full textCombined flow sedimentary structures and the genetic link between sigmoidal- and hummocky-cross stratification
No full textThis work is based on the comparison between facies tracts of flood-dominated fluvio-deltaic systems and basin-
plain turbidites to the main combined flow experimental data available in literature; it discusses the possibility
of a genetic link between sigmoidal and hummocky structures and their significance in facies analysis. Sigmoidal
and hummocky-cross stratifications are large-scale sedimentary structures, usually considered indicative of tidal and
storm deposits, respectively. However, facies analysis of flood-dominated fluvio-deltaic systems in tectonically active
settings shows that these two types of structures are also typical of these depositional systems. In flood-dominated
river-delta systems, coarse-grained mouth bars, which can be characterized by different types of sigmoidal-cross stratifications
deposited by sediment-laden stream flows entering seawater, pass down-current into fine-grained delta-front
sandstone lobes. That is to say, sharp based normally graded beds with hummocky-cross stratifications, deposited by
flood-related hyperpycnal flows characterized by an oscillatory component, whose origin can be related to different
processes. At a small scale, biconvex and rounded ripples and megaripples with sigmoidal-cross laminae are related
to small- and medium-scale hummocky structures in basin plain turbidites, where ponding and rebound processes can
transform the turbidity currents into combined flows. These field observations suggest a genetic link, at different scales,
between these two types of structures, especially in terms of combined flows. This study, therefore, has prompted
a re-examination of the combined-flow sedimentary structures produced in laboratory experiments, and has led to the
proposal and discussion of some facies schemes (small- and large-scale) based not only on the ratio of Uu (unidirectional
velocity) to Uo (oscillatory velocity) but also upon grain sizes, rates of fallout and frequency of oscillatory
component (i.e. the period T)
Stratigraphy, facies and processes of Roda Sandstone: a river-delta system dominated by hyperpycnal flows (Lower Eocene, south-central Pyrenees)
No full textA NEW TURBIDITE FACIES TRACT SCHEME INCLUDING SUPERCRITICAL AND TRANSITIONAL SAND/MUD FLOWS: AN OUTCROP PERSPECTIVE FROM MEDITERRANEAN-TYPE FORELAND BASINS
No full textProposal for a classification scheme for combined flow sedimentary structures and the meaning of sigmoidal- and hummocky-cross stratification in facies analysis
No full textThe Miocene turbidite deposits of the Marnoso-arenacea Formation (northern Apennines, Italy)
No full textIn the northern Apennines, thick and laterally
extensive terrigenous turbidite successions were
deposited during the late Oligocene and Miocene, as
the fill of elongated, NW-stretched foredeeps formed
in front of the growing Apennine orogenic wedge.
These turbidites, which are the classic sandy flysch
formations (Macigno, Cervarola,Marnoso-arenacea)
upon which Migliorini (1943) elaborated his
fundamental concept of resedimentation, were
progressively incorporated into the frontal part of the
orogen during its propagation towards the NE (see
also Kuenen & Migliorini, 1950). Among these
turbidite units, the Marnoso-arenacea Formation
(Langhian to Tortonian in age) is the best exposed and
less structurally deformed due to its relatively external
position within the Apennine orogen.
Thanks to the early works by Ricci Lucchi (1969, 1975,
1978, 1981, 1986),Mutti & Ricci Lucchi (1972), Ricci
Lucchi & Pignone (1979) and Ricci Lucchi & Valmori
(1980), the Langhian to Tortonian Marnoso-arenacea
Formation (MAF) is probably the most famous among
the clastic units, which record the structural evolution
of the Apennine thrust belt. However, recent studies
have shown that the MAF’s stratigraphy and
depositional settings are more complex than
previously thought, due to the accompanying
structural deformation that exerted a control over
basin geometry, facies distribution patterns and
emplacement of mass-transport complexes (de Jager,
1979; Ricci Lucchi, 1986; Argnani & Ricci Lucchi,
2001; Mutti et al., 2002a, 2003; Roveri et al., 2002;
Lucente & Pini, 2002, 2003; Lucente, 2004; Bonini,
2006).As a result, the vertical stacking pattern of the
Marnoso-arenacea records a close interaction
between thrust propagation towards the NE and
deposition from turbidity currents flowing towards the
SE, i.e. parallel to the thrust fronts.
This view has prompted a re-examination of the
MAF’s stratigraphy and facies starting with the
Turbidite Workshop held in Parma in 2002 (Mutti et
al., 2002a). The main intent of this field trip is to
present the preliminary results of the continuation of
this study, illustrating the sedimentary characteristics
of the stratigraphic succession of MAF (about 4000m
thick) that records the progressive closure of the
foredeep due to the NE propagation of thrust fronts.
In particular, this guide will present a detailed
stratigraphic cross-section (with bed-by-bed
correlations) of the upper Langhian to Serravallian
stratigraphic succession of MAF outcropping in
Romagna Apennines (Muzzi Magalhaes, 2009; see also
Muzzi Magalhaes and Tinterri, 2009). This interval
covers a thickness of about 2,500m and a distance of
about 60km in a SE direction, i.e. parallel to the
paleocurrents. It has well-exposed outcrops with good
lateral continuity and numerous key beds - many of
which are mapped on the geological maps of the
Emilia-Romagna region (Cerrina Feroni et al., 2002;
Martelli et al., 1994).These characteristics have proved
fundamental for many MAF field studies attempting
high-resolution stratal correlations over significant
distances.The pioneering work in this sense was Ricci
Lucchi & Valmori (1980), which took into account a
stratigraphic interval of 200m around the Contessa
key bed, for a horizontal distance of 120km. More
recently, Amy et al. (2005), Amy and Talling (2006)
presented correlations of a high number of
stratigraphic logs covering an interval of about 25m
comprised between the Contessa and Colombina 1
key beds
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