Conference PaperPDF Available

Multi-scale characterization of the Pleistocene-Holocene Tiber delta deposits as a depositional analogue for hydrocarbon reservoirs

Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
Multi-scale characterization of the Pleistocene-Holocene Tiber delta deposits as
a depositional analogue for hydrocarbon reservoirs
Mattia Marini1, Salvatore Milli1, Massimo Rossi2, Vittorio De Tomasi2, Marco Meda2, Nicola Lisi2
1Dipartimento di Scienze della Terra, SAPIENZA Università di Roma, Roma, Italy
2Eni E&P Division, San Donato Milanese, Milano, Italy
The study of well exposed or shallow buried
depositional analogues of clastic coastal systems such as
estuaries and deltas is very attractive as it is cost-effective
and virtually provides any scale of detail. In the field,
stratigraphic-sedimentologic sections can be measured
and outcrop face surveyed using laser scanning
techniques that allow to reveal depositional geometries
and spatial distribution of facies with a resolution down to
few centimetres. Where these analogues are in the shallow
subsurface of urban or development areas, the availability
of a large number of well-spaced, public domain boreholes
and geophysical surveys, can allow a nearly three-
dimensional reconstruction of the depositional and
stratigraphic architecture at scales down to few tens of
metres. From these 3D volumes, significative cross-
sections can be obtained which permit to visualize
lithofacies distribution vs. depositional geometries and
understand large-scale permeability patterns.
Additionally, when the petrophysical properties are
available as input, two-dimensional seismic modeling can
be undertaken to obtain simulated seismic sections to be
used in order to image the most likely seismic features of
the internal reservoir geometry.
The paralic successions deposited under the influence
and supply of Tiber river during the Pleistocene and
Holocene, crop out extensively in the southwestern sector
of Rome thanks to the presence of many quarries or are
buried in the subsurface of the present-day Tiber delta
plain; they represent a suitable depositional analogue for
undertaking such an approach. The aim of the study
detailed here was to achieve a multi-scale characterization
of selected part of these paralic successions which may
serve as depositional analogues for hydrocarbon
To this purpose, we conducted: i) the integration of
unpublished data from Milli (2013) with novel outcrop
and borehole data with the aim of better defining the
depositional architecture of study objects; ii) the two-
dimensional seismic modeling of selected cross sections
using as input seismic velocities deduced integrating
geophysical, geotechnical and petrophysical data from the
subsurface of the Tiber delta and the literature; iii) the
modeling of geometries and facies architecture of a gravel
beach conditioned to 3D photo-textured models obtained
through LIDAR and ortho photogrammetry techniques.
The Pleistocene-Holocene deposits forming the subject
of this research represent part of the sedimentary fill of
the Roman Basin, which is located along the eastern
margin of the Tyrrhenian Basin, the youngest back-arc
basin of the Mediterranean area forming since the late
Miocene in response to back-arc extension in the
Apennines foreland basin system.
Along the Latium Tyrrhenian margin, the extensional
tectonics gave rise to NNW-SSE/NW-SE half-graben
basins, which were filled with syn- and post-rift clastic
sediments during the Plio-Pleistocene. Among these
extensional basins, the Roman Basin straddles the
present-day Tiber delta and extends for about 135 km in
a N-S direction. Its development started in the Late
Pliocene and was accompanied by tectonic uplift and
intense volcanic activity reaching their climax in the
Middle-Upper Pleistocene, when the Roman Magmatic
Province started up (Fig. 1).
Therefore, the stratigraphy of the Roman Basin resulted
from the close interaction of tectonic uplift, volcanic
activity and glacio-eustatic sea-level fluctuations driven
by the Quaternary climate changes (Milli, 1997). The
architecture of the basin is characterized by several units
forming high-frequency depositional sequences with
average duration spanning from 30,000 yr to 120,000 yr
(4th-order), stacked to form two composite 3rd-order
sequences, namely the Monte Mario Sequence (MMS;
Pleistocene) and the Ponte Galeria Sequence (PGS
hereafter; Late Lower Pleistocene-Holocene) Milli et al.,
2011, 2013). In the study area, the MMS is very poorly
exposed and its knowledge is mostly based on data from
relatively deep wells. Its deposits are represented by coastal
and transition-shelf depositional systems of the Late
Lowstand and Transgressive Systems Tracts. Oppositely,
the PGS is particularly well-exposed and shows a number
of adjacent depositional settings. It contains fluvial, fluvio-
lacustrine, barrier island-lagoon, and transition-shelf
Journal of Mediterranean Earth Sciences
MARINI_ARGENTI 30/07/13 14:08 Pagina 103
depositional systems organised to constitute the lowstand
(LST), transgressive (TST) and highstand (HST) systems
tracts. PGS sediments are also interfingered with the
volcaniclastics deposits of the Albani and Sabatini
volcanic complexes.
In the studied area, the PGS is 10 to 110 m thick and lies
above the shelfal mud sediments of the MMS through a
polygenic erosional surface which is related to the sea-
level fall occurred between the MIS 31 and 27. It
represents a composite sequence consisting of twelve 4th-
order sequences (with thickness ranging from 5 to 80 m)
whose boundaries are sharp erosional surfaces recording
basin and downward facies shifts, subaerial exposure and
paleosols in the interfluves. From the sequence
stratigraphic point of view the sequences from PG01 to
lower PG1 stack to form the late LST, which developed
during a period of stillstand and slow relative sea-level rise
that produced a series of prograding and aggrading
wedges-shaped units. Sequences from PG1 to lower PG8
are interpreted as part of the TST, while the PG9 sequence,
namely the Tiber Depositional Sequence (TDS hereafter)
developed entirely during the HST.
The architecture of the PGS is characterized by a seaward
stacking pattern of its component 4th-order sequences
that contrasts with the evidence of a glacio-eustatic sea-
level rise which alone would have produced landward
migration of the equilibrium point of progressively
younger sequences. This counter-intuitive internal
stacking pattern of PGS is thought to be controlled by
regional tectonic uplift which forced the erosion and
incision of inland areas and the seaward migration of the
fourth-order sequences.
Modeling the small-scale depositional architecture of
the PG2 gravel beaches
Following the acquisition of a large LIDAR dataset from
two quarries (ESI and Tiberi quarries, see figure 2)
excavated in the lower PGS, the best exposed quarry faces
were chosen as input dataset for modeling in 3D the
depositional architecture of the PG2 gravel beaches.
The object to be modelled is a few m-thick gravel beach
depositional body representing a forced-regressive
deposit, which is exposed along two orthogonal faces of
the Tiberi quarry over about 350 m along strike (i.e., along
the palaeo-shoreline, namely in a NS direction) and 100 m
along dip (perpendicular to the palaeo-shoreline, that is
along the dip direction of the beach face clinoforms). In
the package to be modelled, the beach body profile can be
followed from the foreshore down to the upper shoreface
passing through the beachface which clearly shows
clinoforms with average dip angle of approximately 10°.
The photorealistic model reconstructed though LIDAR
and ortho photogrammetric techniques was interpreted
using Geco (ENI proprietary software for 3D visualization
Mattia Marini et al.
104 Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
Fig. 1 - Geological sketch of the Tyrrhenian margin, central Italy. 1) Messinian to Holocene sedimentary deposits; 2) Plio-Pleistocene
lavas and volcaniclastic deposits; 3) Meso-Cenozoic sedimentary deposits; 4) main buried faults; 5) strike-slip faults; 6) normal faults;
7) major thrusts. The black square indicates the study area.
MARINI_ARGENTI 30/07/13 14:08 Pagina 104
Multi-scale characterization of the Pleistocene-Holocene Tiber... 105
Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
Fig. 2 - Correlation panel showing the stratigraphic relationship between the high-frequency sequences cropping out in the Tiberi and ESI quarries. The correlation was worked out with the aid of
logs measured in the field and boreholes (from Milli, 2013, unpublished data).
MARINI_ARGENTI 30/07/13 14:08 Pagina 105
and interpretation of outcrop data) picking first the main
bounding surfaces and then discretizing the outcrop face
into grain size classes (sensu Blott and Pye, 2012). A grain
size-approach was preferred in place of a facies approach
as gravel beaches are generally constituted by packages of
very thin beds of rather homogeneous texture which
represent the actual building block of the beach itself and
are indicative of precise hydrodynamic condition along
the depositional profile. Sandy silts are only present at the
top of the modelled depositional body where their
deposition marks the maximum flooding surface
separating the two superimposed beach sub-units
constituting the PG2 in this area.
Planar parallel laminated gravelly sands dipping
seaward at very low angle (0° to 5°) represent the main
texture in the foreshore which along dip passes to sandy
and gravelly clinoforms internally made of dm-thick beds.
Occasionally, coarser bodies of sandy gravel are found in
the lower beach face where they would testify a seaward
transport of coarse sediment related either to distributary
channel mouths or to rip currents. The upper shoreface is
characterized by dm-thick alternations of sands and
gravely sands where the latter would record episodic
gravitative events ignited by either wave of storm-induced
shocks on the beachface. Because of the highly dynamic
nature of both foreshore and beachface, individual beds
prevalently show erosional bases across which they are
welded to form composite depositional bodies with
homogenous grain-size and highly complex geometry. In
the studied example, these bodies are commonly
represented by m-thick welded clinoforms of sandy
gravels showing lateral continuity of few 10’s m along
either strike and dip (Fig. 3)
The overall architecture of the lower PGS beach bodies
has been unravelled correlating the two quarries with the
aid of stratigraphic logs and boreholes (Fig. 2). The
continuity of the individual beach packages in strike
section can be estimated to at least 10 km in a N-S
direction whilst along dip it would not exceed few
hundred m before the beach body fades into lower
Mattia Marini et al.
106 Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
Fig. 3 - Dip-section photo panel of the Tiberi quarry (a) exposing the PG1 and PG2 sequences and Geco interpretation window (b)
showing the distribution of grain-size classes and depositional environments.
MARINI_ARGENTI 30/07/13 14:08 Pagina 106
shoreface facies association. Nonetheless, size and internal
architecture of these packages may be highly complex as
their deposition is intimately related to the interplay of
high frequency relative sea level changes and other
allocyclic-autocyclic factors, such as longshore sediment
drifting and compensation of local topography. Individual
beach packages are likely to represent single sandy-
gravelly flow units with primary permeability in range of
10-4-10-3 m/s containing even more permeable pockets
of either coarser or better sorted sediments (Fig. 4). The
two beach packages of PG2 are separated by a m-thick bed
of silty sands, a seal (Fig. 3) which landward is likely to be
eroded by the upper beach package.
The bottom and top of the package to be modelled were
reconstructed through a step-wise process which required
to linearly interpolate picked horizons with isolines in
plan view and then model surfaces with the convergence
interpolation algorithm. The output from Geco, which
consisted of a cloud of points coded according to grain
size classes, was imported in Petrel 2011 by Schlumberger
and up-scaled to a grid conformable to clinoforms with
2.5 m ·2.5 m ·0.1 m (I ·J ·K) cells. Grain size classes
were than modelled in either as a continuous or discrete
property using a Sequential Gaussian Simulation or
Sequential Indicator Simulator, respectively. Further
models were run to account for interpretation bias and
trends in grains size possibly related to changes in beach
dynamics and sediment supply.
Seismic modeling
Geometrical representations of the TDS and the
uplifted Pleistocene deposits to be modeled were digitized
from stratigraphic cross-sections which in turn were
reconstructed correlating a large number of boreholes and
sparse outcrops. For each deposition unit, parameters
such as effective and total porosity, fluid content and
mineral components percentages (quartz, feldspar, calcite,
illite, smectite, etc.) were defined basing on results of
petrophysical analysis conducted on samples from the
well ‘Pesce Luna’ (Milli et al., 2013). Density and elastic
moduli of the mineral components were derived from the
literature (Ahrens, 1995; Morcote at al., 2010; Wang et al.,
2001) in order to estimate seismic velocities and density
for each unit applying rock-physics equations (Hashin-
Shtrickman bounds, critical porosity and friable sand
models, Gassmann’s law, Mavko et al., 2009). Predictions
for Vp, Vs and density were computed for each model at
different burial depth and gas saturation. The seismic
response at different resolution was then computed using
a convolutional model and a Ricker wavelet in order to
highlight the relationships between stratigraphy and
seismic imaging and describe the possibility to seismically
resolve various aspects of a complex stratigraphy under
different conditions. Three different wavelet frequencies
were used: 30, 60 and 100 Hz.
The starting geomodels define the lateral and vertical
distribution of “impedance facies” (Fig. 5), obtained
through the computation of impedance values for each
facies in the cross sections. Although buonding surfaces
are often supposed to represent impedance boundaries
generating laterally-persistent reflections, our results
demonstrate that in heterogeneous reservoirs impedance
and polarity changes may be common along the same
bounding surface. This is more true for subaerial
sequence boundaries or regressive surfaces of marine
erosion, while some marine flooding surfaces tend to
show more laterally continuos impedance boundaries.
These conditions also dramatically change in relation to
the thickness changes of the facies above and below each
bounding surface and therefore show very different
imaging when varying wavelet frequency.
This implies that under different resolution potential,
seismic imaging defines an hypotetical reservoir
architecture that is changing not merely in terms of
resolved thickness and of an higher or lower degree of
detail (that could be possibly corrected through standard
up-scaling or down-scaling procedures), but more
problematically generating different shape of the
identified geobodies.
Multi-scale characterization of the Pleistocene-Holocene Tiber... 107
Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
Fig. 4 - Block diagram showing the scale and geometry of depositional bodies making up the gravel beach of the PG2.
MARINI_ARGENTI 30/07/13 14:08 Pagina 107
Mattia Marini et al.
108 Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
Fig. 5 - Example of seismic modeling of the Tiber sequence incised valley fill showing, from top to bottom: a) stratigraphic cross-section of the Tiber Depositional Sequence;.b) strike impedance
facies model; c) strike synthetic seismic profile at 100 Hz bandwidth.
MARINI_ARGENTI 30/07/13 14:08 Pagina 108
The preliminary results of this research are useful for
hydrocarbon reservoir characterization from both the
exploration and production perspectives as they prove
i) the architecture of 4th-order sequences, despite a
relatively short duration (100 Kyr) and a small thickness
(10 to 70 m for the PG9) can be very complex internally
and result in a variety of possible connectivity scenarios,
which require closely and well distributed borehole data to
be explored and a detailed stratigraphic reconstruction.
From this standing point, the PG9 is a scholarly
depositional analogue comprising a number of peculiar
features of both estuary and deltaic systems;
ii) in shallow buried reservoirs, seismic can capture fine
scale architectural elements such as those described from
the PG9. Hence, the architecture of studied depositional
analogue detailed in this study represents a useful
reference model for interpreting seismic from reservoir
hosted in alike depositional sequences;
iii) in deeper conditions, imaging different “impedance
facies” becomes a crucial issue in heterogeneous
reservoirs. Although bounding surfaces are often
supposed to generate laterally-persistent reflectors, our
results demonstrate that impedance and polarity changes
may be common along the same bounding surface. This
implies that apparent changes in reservoir architecture are
not merely associated to the obvious decay in resolution
but may affect the correct identification of geobodies
shape and connectivity; 
iv) the complexity of gravel beaches require a multi-
scale characterization to capture both their overall 3D
shape and connectivity of reservoir facies;
v) a successful facies modeling of outcrop data can allow
reconstructing semi-quantitatively the fine-scale
permeability structure. Results obtained in this study
using Petrel 2011 by Schlumberger can be exported to
analogue reservoir contributing to formation evaluation
and implementation of production strategy.
ACKNOWLEDGEMENTS - The authors would to like to
thank ENI E&P Division for having financially supported the
research project and for allowing the publication of data and
ISPRA, The Geological Survey of Italy for the sampling of Pesce
Luna well.
Ahrens T.J. 1995. Rock Physics & Phase Relations - A Handbook
of Physicals Constants, American Geophysical Union, ISBN
Blott S.J., Pye K. 2012. Particle size scales and classification of
sediment types based on particle size distributions: Review
and recommended procedures. Sedimentology: 59, 2071-
2096. doi: 10.1111/j.1365-3091.2012.01335
Mavko G., Mukerji T., Dvorkin J. 2009. The Rock Physics
Handbook, Cambridge university Press, ISBN 978-0-521-
Milli S. 1997. Depositional setting and high-frequency sequence
stratigraphy of the Middle-Upper Pleistocene to Holocene
deposits of the Roman basin. Geologica Romana: 33, 99-136.
Milli S., Palombo M.R., Anzidei A.P. 2011. I depositi
pleistocenici di Ponte Galeria e la Polledrara di Cecanibbio.
Guida all’escursione post-congresso AIQUA 2011 “Il
quaternario Italiano - Conoscenze e prospettive, Roma 26
Febbraio 2011, p. 37.
Milli S., D’Ambrogi C., Bellotti P., Calderoni G., Carboni M.G.,
Celant A., Di Bella L., Di Rita F., Frezza V., Magri D.,
Pichezzi R.M., Ricci V. 2013. The transition from wave-
dominated estuary to wave-dominated delta: the Late
Quaternary stratigraphic architecture of Tiber deltaic
succession (Italy). Sedimentary Geology: 284-285, 159-180.
Morcote A., Mavko G., Prasad M. 2010. Dynamic elastic
properties of coal. Geophysics: 75,227-234.
Wang Z., Wang H., Cates M.E. 2001. Effective elastic properties
of solid clays. Geophysics: 66, 428-440.
Multi-scale characterization of the Pleistocene-Holocene Tiber... 109
Journal of Mediterranean Earth Sciences Special Issue (2013), 103-109
MARINI_ARGENTI 30/07/13 14:08 Pagina 109
... Recent advances in remote sensing, photogrammetry and unmanned aerial vehicle (UAV) technologies make today possible the acquisition of detailed digital outcrop models, which can be used by geologists to extract scalars associated with geological features such as, for example, bedding and fracture orientation and lithology and sedimentary facies proportions [26][27][28][29][30][31][32]. ...
Full-text available
Diagenesis is a key controlling factor on sandstone porosity and permeability. Understanding type, paragenetic sequence and spatial patterns of cements is thus important for assessing sandstone hydrocarbon reservoir properties. In this study Unmanned Aerial Vehicle (UAV) photogrammetry is used to evaluate the shape and spatial distribution of calcite concretions developed within the sand-prone fill of a turbidite channel. The studied channel-fill is entrenched into hemipelagic marlstones and include a lower conglomeratic sandstone loaded with marlstone rip-ups and an upper fill featuring a range of turbidite bed types, which, up-section and off the channel axis, are progressively finer grained and less amalgamated. Concretion shape analysis highlighted a continuum of equant to oblate shapes with flat-lying major axes and a cumulative volume fraction of ca. 22%. Equant to sub-equant concretions are ubiquitous and occur at different heights within beds, often developing around marlstone rip-ups. Conversely, elongated concretions are either strata-bound concretions or completely cemented beds which become volumetrically dominant up section and off the channel axis. The interparticle pore-space of concretions represents on average ca. 22% and is tightly filled by poikilotopic and blocky calcite cement precipitated near to maximum burial depth, whereas host sandstones lack calcite cements and show smectite clay cement and an average preserved porosity of ca. 15%. The oxygen and carbon isotopes of calcite cements point to the marlstone as the main source of carbonate ions, suggesting concretions developed during burial by either diffusion from rip-ups and mud caps or recrystallization of, matrix micrite. Results suggest that the process by which the carbonate-rich component was eroded from the substrate and trapped within the channel-fill is a key control on spatial distribution of calcite concretions, likely to reflect on spatial variability of reservoir properties.
... It originated when the river in flood directly discharged a sustained (Carruba et al., 2004;Felletti et al., 2009) and relatively denser turbulent mixture of fresh water and sediments (hyperpycnal flows; Bates, 1953) into the receiving standing body of water. This system extended for kilometers away from the river mouth and developed a predictable path of genetically related facies (Browne and Naish, 2003;Mancini et al., 2013;Marini et al., 2013;Milli et al., 2016;Bruno et al., 2017) during its travel basinward. ...
Full-text available
The Arda River marine succession (Italy) is an excellent site to apply an integrated approach to paleoenvironmental reconstructions, combining the results of sedimentology, body fossil paleontology, and ichnology to unravel the sedimentary evolution of a complex marine setting in the frame of early Pleistocene climate change and tectonic activity. The succession represents a subaqueous extension of a fluvial system, originated during phases of advance of fan deltas affected by high-density flows triggered by river floods, and overlain by continental conglomerates, indicating a relative sea level fall and the establishment of a continental environment. An overall regressive trend is observed through the section, from prodelta to delta front and intertidal settings. The hydrodynamic energy and the sedimentation rate are not constant through the section, but they are influenced by hyperpycnal flows, whose sediments were mainly supplied by an increase in Apennine uplift and erosion, especially after 1.80 Ma. The Arda section documents the same evolutionary history of coeval successions in the Paleo-Adriatic region, as well as the climatic changes of the early Pleistocene. The different approaches used complement quite well one another, giving strength and robustness to the obtained results.
... In addition, the several stratigraphic cross-sections may allow definition of three-dimensional (3D) volumes within which the lithofacies distribution, the depositional geometry and the small-scale to largescale permeability pattern can be reconstructed. Furthermore, when the petrophysical properties are available, 2D seismic modelling can be undertaken to obtain a simulated seismic section which can be used in order to image the most likely seismic features of the internal hydrocarbon or water reservoir geometry (Marini et al., 2013), and as a model for hydrostratigraphy and geohazard evaluation (subsidence, soil settlement and local seismic response). ...
The Late Pleistocene/Holocene Tiber delta succession represents the most recent and one of the best preserved, high-frequency/low-rank depositional sequences developed along the Latium continental margin of the Italian peninsula. Several previous studies have established a robust data set from which it has been possible to describe the stratigraphic architecture of the entire Tiber depositional sequence from the landward to seaward sectors and over a distance of 60 km. The Tiber depositional sequence shows many characteristics found in other Late Pleistocene to Holocene deltaic and coastal successions of the Mediterranean area. The stratigraphic architecture of the Tiber depositional sequence is controlled mainly by glacioeustasy, although factors such as tectonic uplift, volcanism and subsidence, exert an influence at a local scale. The resulting depositional model allowed discussion of some important points such as: (1) the genesis of the Tiber mixed bedrock-alluvial valley, extending from the coastal plain to the innermost portion of the shelf, recording (i) multiple episodes of incision during relative sea-level fall, and (ii) a downstream increase of depth and width of the valley during the base-level fall and the subsequent base-level rise; (2) the different physical expression of the Tiber depositional sequence boundary from landward to seaward, and its diachronous and composite character; (3) the maximum depth reached by the Tiber early lowstand delta at the end of the sea-level fall is estimated at ca 90 m below the present sea-level and not at 120 m as suggested by previous works; (4) the backward position of the Tiber late lowstand delta relative to the deposit of early lowstand; (5) the change of the channel pattern and of the stacking pattern of fluvial deposits within the Lowstand Systems Tract, Transgressive Systems Tract and High-stand Systems Tract. All of these features indicate that the Late Pleistocene/ Holocene Tiber delta succession, even if deposited in a short period of time from a geological point of view, represents the result of the close interaction among many autogenic and allogenic factors. However, global eustatic variations and sediment supply under the control of climatic changes can be considered the main factors responsible for the stratigraphic architecture of this sedimentary succession, which has been heavily modified by human activity only in the last 3000 years. 1
Full-text available
This paper presents a detailed description of the stratigraphic architecture of the Late Pleistocene/Holocene Tiber delta succession in order to document the passage from wave-dominated estuary to wave-dominated delta in the broader context of Late Quaternary sea level fluctuations. This succession constitutes a sequence-stratigraphic unit known as Tiber Depositional Sequence (TDS), which was deposited during the last glacial–interglacial cycle (last 120 ka). Our study is based on the examination of an enormous amount of data derived from the stratigraphy of about 300 wells, petrographical and paleon-tological data (foraminifera, ostracoda, pollen, and plant macrofossils), 14 C dating, and from the integration of geomorphological and geoarcheological data. Recently a 100 m deep core (Pesce Luna well) was studied through a multidisciplinary approach and a detailed description of sedimentary facies, foraminifer and ostra-cod assemblages, pollen and 14 C dating is presented in this paper. The new data allowed to produce three new correlation panels and to describe in more detail, with respect to previous interpretations, the stratigraphic-depositional architecture of the TDS, which internally shows the preservation of sediment de-posited during the early and late lowstand, the transgressive and the highstand systems tracts. Alluvial and coastal depositional systems characterize the early lowstand phase of the TDS, which developed during the eustatic sea-level fall between about 120 and 30–26 yr BP. During the late lowstand phase, which is charac-terized by stillstand and slow eustatic sea-level rise a prograding delta and an aggrading incised-valley fluvial fill developed. The Tiber incised valley was transformed into a wave-dominated estuary during the transgres-sive phase (TST), whereas a coastal-shelf sedimentation took place during the subsequent highstand phase (HST). This study confirms the lithofacies distribution resulting from transgression and infilling of the wave-dominated estuaries, but also shows how the transition to a wave-dominated delta, prograding at the time of sea-level highstand occurred. Changes in sediment input, climatic variations and, more recently, human activities played a major role in the development of the Tiber delta during the last 20,000 yr BP. In the last 3000 years a relationship between progradational phases of the delta and flood events of the Tiber river has been highlighted, suggesting also the formation and merging of barrier-spits to the mainland.
The results of a detailed facies and sequence stratigraphy analysis allowed us to subdivide the Roman Quaternary deposits into two third-order depositional sequences. The first (Monte Mario Sequence), dated between 1,795 and 0,87 Ma (Lower Pleistocene) is bounded below and above by a type 1 sequence boundary. The second (Ponte Galeria Sequence) dated from 0,87 Ma to present (Middle - Upper Pleistocene to Holocene) is an uncomplete depositional sequence, bounded below by a type 1 sequence boundary and above by the present sea level. Both sequences are thought to be composite sequences because they contain higher-frequency sequence (fifth and fourth order). As concerns the Monte Mario Sequence, only the outcropping deposits of the highstand systems tract are known. They are represented by two coeval clastic shore-zone and terrigenous shelf depositional systems. This paper focusses on the Ponte Galeria sequence, which consists of lowstand wedge, transgressive and highstand systems tracts with lacustrine, fluvial, coastal plain, coastal barrier-lagoon and terrigenous shelf deposits. In the Ponte Galeria Sequence, a series of erosional unconformities were recognized; it was thus possible to subdivide the entire succession into nine fourth-order depositional sequences. High-frequency sequences were interpreted as having formed in response to sea-level cycles of 100 ka. However, the results of this study showed that tectonic uplift and volcanism played an important role in the organization and evolutionary trend of the third- and fourth-order depositional sequences. In particular, the interaction between these factors determined the seaward migration of the fourth-order depositional sequence equilibrium points which would have migrated landwards if the evolution of this sedimentary succession had been controlled by eustasy alone.
This paper provides a review of different particle size scales, size class terminology and particle size distribution (‘textural’) classification schemes which are widely used in sedimentology, geomorphology, soil science, aquatic ecology and civil engineering. It is concluded that a revised system of size class nomenclature, based on the Udden (1898) and Wentworth (1922) schemes, provides the most logical and consistent framework for use with sediments and a wide range of other particulate materials. A refined scheme is proposed which has five first‐order size classes (boulder, gravel, sand, silt and clay), each of which has five second‐order subdivisions with limits defined at one phi intervals. The scheme is simple and intuitively easy to understand. The paper also provides a review of previous schemes that have been proposed to describe and classify sediments on the basis of the proportions of gravel, sand and mud, or sand, silt and clay using trigons (also termed ternary diagrams). Many of these schemes do not have a logical basis and provide limited or uneven resolution. New gravel, sand and mud and sand, silt and clay classification systems are proposed that are both more logical and provide greater discriminatory power than previous schemes; they are therefore more suitable for use in environmental and forensic investigations. A new Microsoft Excel® program, freely available to download from, allows rapid classification of sediments based on the proportions of gravel, sand and mud and sand, silt and clay proportions and graphical comparison of the data for different sample groups.
Laboratory ultrasonic velocity measurements of different types of coal demonstrate that their dynamic elastic properties depend on coal rank and applied effective pressure. In spite of the growing interest in coal beds as targets for methane production, the high abundance in sedimentary sequences and the strong influence that they have on seismic response, little data are available on the acoustic properties of coal. Velocities were measured in core plugs parallel and perpendicular to lamination surfaces as a function of confining pressure up to 40 MPa in loading and unloading cycles. P- and S-wave velocities and dry bulk and dry shear moduli increase as coal rank increases. Thus, bituminous coal and cannel show lower velocities and moduli than higher ranked coals such as semianthracite and anthracite. The V(P)-V(S) relationship for dry samples is linear and covers a relatively wide range of effective pressures and coal ranks. However, there is a pressure dependence on the elastic properties of coal for confining pressures below 5 MPa. This pressure sensitivity is related to the presence of microcracks. Finally, the data show that coal has an intrinsic anisotropy at confining pressures above 5 MPa, the closing pressure for most of the microcracks. This intrinsic anisotropy at high pressures might be due to fine lamination and preferred orientation of the macerals.
Clay minerals are perhaps the most abundant materials in the earth's upper crust. As such, their elastic properties are extremely important in seismic exploration, seismic reservoir characterization, and sonic-log interpretation. Because little exists in the literature on elastic properties of clays, we have designed a method of measuring effective elastic properties of solid clays (clays without pores). In this method, clay minerals are mixed with a material with known elastic properties to make composite samples. Elastic properties of these clay minerals are then inverted from the measured elastic properties of the composite samples using the weighted Hashin-Shtrikman average. Using this method, we have measured 66 samples of 16 types of clays. In this paper, we present a comprehensive data set of elastic properties of solid clays that commonly occur in, or are related to, petroleum reservoirs. Although uncertainties (up to 10%) exist, the data set reported here is by far the most comprehensive set of elastic properties in the literature. These data can be used potentially in modeling the seismic properties of clay-bearing rocks.
Rock Physics & Phase Relations -A Handbook of Physicals Constants
  • T J Ahrens
Ahrens T.J. 1995. Rock Physics & Phase Relations -A Handbook of Physicals Constants, American Geophysical Union, ISBN 1080-305X.
I depositi pleistocenici di Ponte Galeria e la Polledrara di Cecanibbio. Guida all' escursione post-congresso AIQUA 2011 "Il quaternario Italiano -Conoscenze e prospettive
  • Milli S Palombo
  • M R Anzidei
Milli S., Palombo M.R., Anzidei A.P. 2011. I depositi pleistocenici di Ponte Galeria e la Polledrara di Cecanibbio. Guida all' escursione post-congresso AIQUA 2011 "Il quaternario Italiano -Conoscenze e prospettive, Roma 26 Febbraio 2011, p. 37.