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Figure 4. Sand model showing the impact of oblique convergence on strain partitioning, geometry of fault networks
in the Island and escape tectonics occurring in the middle west and southwestern Taiwan
REFERENCES
Dahlen F.A., Suppe J. & Davis D.M.; 1984: Mechanics of fold and thrust belts and accretionary wedges: Cohesive
Coulomb theory. J. Geophys. Res., 89, 10087-10101.
Konstantinovskaia, E., and Malavieille, J.; 2005: Erosion and exhumation in accretionary orogens : Experimental
and geological approaches. Geochemistry, Geophysics, Geosystems, Vol. 6, Number 2, 25 pp.
Lohrmann, J., Kukowski, N., Adam, J. and Oncken, O.; 2003: The impact of analogue material properties on the
geometry, kinematics, and dynamics of convergent sand wedges. Journal of Structural Geology, 25(10): 1691-1711.
Lu, C.Y. and Malavieille, J.; 1994: Oblique Convergence, Indentation and Rotation Tectonics in the Taiwan
Mountain Belt - Insights from Experimental Modeling. Earth and Planetary Science Letters, 121(3-4): 477-494.
Platt J.P.; 1986: Dynamics of orogenic wedges and the uplift of high-pressure metamorphic rocks. Geol. Soc. Amer.
Bull., 97, 1037-1053.
Willett S.D. & Brandon M.T.; 2002: On steady states in mountain belts. Geology, 2, 175-178.
UPLIFT AND EROSION RATES FROM THE SOUTHERN APENNINES, ITALY
M. Schiattarella(1), P. Beneduce (1), D. Capolongo (2), P. Di Leo (3), S.I. Giano (1), D. Gioia (1), M. Lazzari (4),
C. Martino (1)
(1)
Dipartimento di Scienze Geologiche, Università della Basilicata, Potenza (Italy)
Dipartimento di Geologia e Geofisica, Università di Bari, Bari (Italy)
(3)
CNR-IMAA, Tito Scalo, Potenza (Italy)
(4)
CNR-IBAM, Tito Scalo, Potenza (Italy)
(2)
Summary
Past studies of tectonically active mountain ranges suggested strong coupling and feedbacks among
climate, tectonics and topography. Estimates of parameters useful for understanding evolutionary history
of orogenic chains, especially values of both uplift and/or erosional rates and tectonic/sedimentary
loading experienced by sedimentary successions, have gathered momentum during the last decade, and
nowadays represents a powerful tool in which geoscientists are strongly interested (Burbank & Anderson,
2001; Kirby & Whipple, 2001; Pazzaglia & Brandon, 2001; Willett & Brandon, 2002; Schiattarella et al.,
2003). Such parameters allowed in fact a better definition of exhumation age, timing and modality of the
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most ancient rocks in complex orogens as the southern Apennines (Schiattarella et al., 2003, 2006;
Aldega et al., 2005). Further, a more exact genesis ascription of structural features of mountain chains,
such as tectonic style, regional morphostructural setting, tectonic meaning and opening kinematics of
recent intermontane basins, is also an important target that can be achieved by using such an integrated
approach.
Although theoretical links between climate, erosion and uplift have often received much attention, few
studies regarding the southern Italian Apennines have shown convincing correlations between observable
indices and parameters of these processes on mountain-range scales. The records about erosion rates
exist, for example, from the hydrological practice of measuring sediment transport by rivers, but
infrequently will that record include the full range of floods that have shaped the landscape. First studies
dealing with uplift rates from the Italian Apennines appeared only recently. Many of these, referring to
different sectors of the chain (Westaway, 1993; Basili et al., 1999; Amato, 2000; Schiattarella et al.,
2003; Boenzi et al., 2004), were non representative of the entire orogenic system. Although stratigraphic
characteristics of Quaternary deposits of the intermontane basins are generally well defined, a more
precise assessment of the deposit ages is still needed to better date the morphological features (mainly
land surfaces and terraces) used to estimate uplift rates. Anyway, new data and models for the
comprehension of the regional morpho-structural settings of the northern, central, and southern
Apennines are now available in Bartolini et al. (2003) and in Schiattarella et al. (2006). With respect to
estimations of maximum palaeotemperatures (converted in sedimentary and/or tectonic loading)
experienced by sedimentary successions, new multidisciplinary data on the south-Apennines chain are at
present available in the literature (Schiattarella et al., 2003, 2006; Aldega et al., 2005). Integrating
different methodologies represent the most conservative approach in studying thermal history of
sedimentary successions involved in the formation of a chain. Such methodologies are based on clay
minerals and their transformation through the tectonic/sedimentary evolution (Di Leo, 2003, and
references therein) as well as on vitrinite reflectance, fluid inclusions, and apatite fission tracks (see Di
Leo et al., 2005, and Invernizzi et al., 2008, for recent examples from the ophiolite-bearing units of
southern Italy).
The comprehension of the morphotectonic evolution of southern Italy needs to be linked together with
uplift and erosion rate calculations, contribution of local tectonics to regional uplift, and with tectonic
loadings from the units outcropping in the same area. In addition, a new effort has to be put to develop a
more suitable methodological approach to understand the role of different paleoclimate scenarios
controlling the landscape evolution. Further, mapping and assessing landforms and erosion in mountain
environments is essential in order to understand landscape evolution and complex feedback mechanisms.
DEMs and remote sensing data can be used to assess the properties of the topography and to estimate
geomorphic indices mostly utilized in studies of tectonic geomorphology such as: hypsometric curve and
hypsometric integral, drainage basin asymmetry, drainage density, stream length-gradient index, ratio of
valley floor width to valley height (Keller & Pinter, 1996), and stream power. The role of remotely
sensed data is still in its early stages in this field, partly hampered by the lack of an adequate regional
modelling capability to assimilate and guide the data collection effort (Capolongo et al., 2002).
This study aims to compare uplift rates with erosional rates (specifically to define the steady-state
conditions of the orogenic wedge) as well as to compare uplift/erosion rates with the paleoclimate setting
in which erosion and uplift processes interacted. To get this objective, geological and geomorphological
makers (paleosols, alteration profiles, erosional surfaces, and paleolandslides, from chain and foredeep
areas) have been used, as well as information on the paleoclimatic evolution during late Quaternary times
has been obtained by the analysis of distribution of clay minerals in continental pelitic sediments,
paleosols, and weathered horizons developed in depositional and erosional surfaces of different age from
key-areas of the southern Apennines. In addition, absolute dating of geomorphological features and
weathered horizons has been produced by different methods.
The study areas are represented by seven Quaternary fault-controlled basins from southern Italy (Fig. 1):
1) the Tito-Picerno basin, with its main river flowing in an asymmetric valley of the axial zone of the
Lucanian Apennine, including the homonymous villages, not far from the town of Potenza; this stream is
a tributary of a network delivering to the Tyrrhenian Sea; the valley sides are characterized by four orders
of erosional polygenic and/or depositional land surfaces, at least (Schiattarella et al., 2004, 2006);
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2) the valley of Pergola and Melandro rivers, flanked by the Maddalena Mts carbonate range to the west
and by Lagonegro pelagic units to the east and filled by lower Pleistocene continental sediments
(Schiattarella et al., 2003; Giano & Martino, 2003; Martino & Schiattarella, 2006, 2008); similarly to the
Tito-Picerno basin, three orders of erosional land surfaces were also identified in the Pergola-Melandro
basin. From a morpho-chronological point of view, these gently dipping surfaces can be confidently
correlated to those from the basin previously described. The formation of the S1 land surface can be
ascribed to the late Pliocene - early Pleistocene, as inferred by the presence of lower-middle Pliocene
marine clastic deposits which were involved in the planation of the 1200 m a.s.l. palaeosurface (S1).
Adopting a counting-from-the-top criterion and regional-scale basin correlations, the S2 and S3 land
surfaces ages can be set up respectively at 1.2 and 0.8-0.7 Ma;
3) the high Agri Valley, located between the carbonate range of the Maddalena Mts and the SirinoVolturino massifs, made of Lagonegro-type pelagic successions, and filled by middle Pleistocene alluvial
deposits (Di Niro et al., 1992; Giano et al., 2000); morphotectonic patterns and uplift rates are detailed in
recent papers (Boenzi et al., 2004; Capolongo et al., 2005), showing a good fit with the other study areas,
although the peak values are higher than the rates calculated for the Tito-Picerno and Pergola-Melandro
basins;
4) the Auletta basin, located between the impressive carbonate ridges of the Alburni Mts to the south and
Mt. Marzano to the north and filled by Pliocene to Pleistocene marine and alluvial successions (Ascione
et al., 1992); the land surfaces setting is slightly different from the previously described basins, due to the
complex Pliocene to Quaternary stratigraphic pattern;
5) the Sinni River catchment basin (upper to middle valley) in southern Basilicata, a complex area
including very different geological units and contrasting geomorphological features; anyway, S2 and S3
erosional land surfaces are largely observable in the area; data about uplift rates are consistent with the
previously collected data-set from the whole southern Apennines, but some significant differences exist
between the erosion rates from the different study areas;
6) the Mercure basin, bordered to west and east respectively by the carbonate ridges of Lauria Mts and
Mt. Pollino and filled by middle Pleistocene deposits showing fluvial and lacustrine facies (Schiattarella
et al., 1994; Gioia & Schiattarella, 2006);
7) the Venosa basin, a mid-Pleistocene lacustrine depression located in the foredeep area (“Fossa
bradanica”), close to the thrust front of the chain and not far from the Mount Vulture, a Pleistocene
volcano which represents part of the source area of the sediments of the basin (Schiattarella et al., 2005;
Giannandrea et al., 2006, and references therein); this area would represent a test-site of the whole
foreland basin zone, for a comparison with the intra-chain basins.
Figure
1.
Location
of
study areas in
southern
Italy
(numerated as in
the table I) and
related values of
erosion rates.
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Figure 2. 3D image of uplift rates from southern
Italy, showing a non homogeneous pattern. The
highest peak is represented by data from Calabria
Coastal Chain.
Table 1.
Study areas from southern Italy
1) Fiumara di Tito-Picerno basin
2) Valley of Melandro River
3) Upper Valley of Agri River
4) Valley of Tanagro River (i.e. Auletta basin)
5) Upper Valley of Sinni River
6) Mercure River basin
7) Fiumara di Venosa basin
Erosion rates (mm/y)
0.20
0.23
0.35
0.25
0.17
0.11
0.17
In all the investigated valleys and surrounding mountains, uplift and erosion rates have been accurately
defined. On the grounds of correlations among land surfaces inside the basin and between these ones and
the nearby palaeosurfaces, uplift rates for the last 2 Ma have been estimated. On a regional scale, the
uplift rates vary from 0.2 mm/y to 1.3 mm/y, with average values of 0.6 mm/y in the Campania-Lucania
Apennine and about 1 mm/y at the Calabria-Lucania border (Schiattarella et al., 2006).
In order to relate the different erosion processes to tectonic mobility of the axial zone of the chain, a
geomorphic quantitative analysis has been carried out and the eroded volumes of rocks forming both the
Mesozoic-Cenozoic bedrock and the Pliocene to Quaternary clastic deposits have been calculated, using
cartographic methods and also converting the fluvial turbid transport data as evaluated by geomorphic
parameters. The annual average erosion rate is about 0.2 mm/y. A summary of the erosion rates
calculated for the single study areas is reported in Tab. I and geographically represented in Fig. 1.
The comparison between uplift and erosion rates suggests in a first analysis that the fluvial erosion did
not match the tectonic uplift of the axial zone of the southern Apennines, which therefore could result a
non-steady system, strongly perturbed by other erosion phenomena. In such a framework, mass
movements have to be necessarily activated to drop the disequilibrium triggered by rates differential.
Nevertheless, uplift rates related to a smaller time-span, and in particular referred to the late Pleistocene –
Holocene interval, revealed values of 0.2-0.3 mm/y, better fitting with the erosion rates calculated in the
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whole study area (indeed, a significant difference between uplift and erosion rates seems to persist during
recent times in the Sinni Valley). This could testify a steady-state of the chain, in which landslide activity
has been concentrated in particular periods of the recent geological past essentially because of climatic
factors and is triggered during historical times also by seismic induction. On the other hand, the erosion
rates calculated for the single catchment basins suggest that – if compared to the uplift rates from the
adjacent ranges (average value of 0.6-0.8 mm/y) – the south-Apennines chain did not yet reach a
condition of steady state, showing the features of a transient landscape. Such a conflicting hypothesis
may be taken into account if we are inclined to admit that not all the sectors of the chain – in a
fragmented tectonic patchwork like the southern Apennines – could stay in conditions of steady state
during the same time-span.
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Aldega L., Corrado S., Di Leo P., Giampaolo C., Invernizzi C., Martino C., Mazzoli S., Schiattarella M., Zattin M.
(2005) - The southern Apennines case history: thermal constraints and reconstruction of tectonic and sedimentary
burials. Atti Ticin. Sc. Terra, Serie Spec., 10, 45-53.
Amato A. (2000) - Estimating Pleistocene tectonic uplift rates in the Southeastern Apennines (Italy) from erosional
land surfaces and marine terraces. In: Slaymaker, O. (Ed.), Geomorphology, Human Activity and Global
Environmental Change. Wiley & Sons, New York, pp. 67-87.
Ascione A., Cinque A., Tozzi M. (1992) - La valle del Tanagro (Campania): una depressione strutturale ad
evoluzione complessa. Studi Geologici Camerti, vol. spec. 1992/1, 209-219.
Bartolini C., D’Agostino N., Dramis F. (2003) – Topography, exhumation, and drainage network evolution of the
Apennines. Episodes, 26, 212-216.
Basili R., Galadini F., Messina P. (1999) – The application of palaeolandsurface analysis to the study of recent
tectonics in central Italy. In: Smith B.J., Whalley W.B. & Warke P.A., Eds., Uplift, Erosion and Stability:
Perspectives on Long-term Landscape Development. Geological Society, London, Spec. Publ., 162, 109-117.
Boenzi F., Capolongo D., Cecaro G., D'Andrea E., Giano S.I., Lazzari M., Schiattarella M. (2004) - Evoluzione
geomorfologica polifasica e tassi di sollevamento del bordo sud-occidentale dell'alta Val d'Agri (Appennino
meridionale). Boll. Soc. Geol. It., 123, 357-372.
Burbank D.W. & Anderson R.S. (2001) – Tectonic Geomorphology. pp 274 Blackwell Science.
Capolongo D., Cecaro G., Giano S.I., Lazzari M., Schiattarella M. (2005) - Structural control on drainage network of
the south-western side of the Agri River upper valley (southern Apennines, Italy). Geogr. Fis. Dinam. Quat., 28, 169180.
Capolongo D., Refice A., Mankelow J. (2002) - Evaluating earthquake-triggered landslide hazards at basin scale. The
example of the upper Sele River valley. Survey in Geophysics, 23, 595-625.
Di Leo P. (2003) - Use of clay mineralogy in reconstructing geological processes: thermal constraints from clay
minerals: Atti Ticin. Sc. Terra, Serie Spec., 9, 55-68.
Di Leo P., Schiattarella M., Cuadros J., Cullers R. (2005) - Clay mineralogy, geochemistry and structural setting of
the ophiolite-bearing units from southern Italy: a multidisciplinary approach to assess tectonic history and
exhumation modalities. Atti Ticin. Sc. Terra, Serie Spec., 10, 87-93.
Di Niro, A., Giano, S.I., Santangelo, N. (1992) - Primi dati sull’evoluzione geomorfologia e sedimentaria del bacino
dell’alta Val d’Agri (Basilicata). Studi Geol. Camerti, vol. spec. 1992/1, 257-263.
Giannandrea P., La Volpe L., Principe C., Schiattarella M. (2006) - Unità stratigrafiche a limiti inconformi e storia
evolutiva del vulcano medio-pleistocenico di Monte Vulture (Appennino meridionale, Italia). Boll. Soc. Geol. It.,
125, 67-92 (con carta allegata in scala 1:25.000).
Giano S.I. & Martino C. (2003) - Assetto morfotettonico e morfostratigrafico di alcuni depositi continentali
pleistocenici del bacino del Pergola-Melandro (Appennino lucano). Il Quaternario, 16, 289-297.
Giano S.I., Maschio L., Alessio M., Ferranti L., Improta S., Schiattarella M. (2000) - Radiocarbon dating of active
faulting in the Agri high valley, southern Italy. Journal of Geodynamics, 29, 371-386.
Gioia D. & Schiattarella M. (2006) - Caratteri morfotettonici dell’area del Valico di Prestieri e dei Monti di Lauria
(Appennino meridionale). Il Quaternario, 19, 129-142
Invernizzi C., Bigazzi G., Corrado S., Di Leo P., Schiattarella M., Zattin M. (2008) - New thermobaric constraints on
the exhumation history of the Liguride accretionary wedge (southern Italy). Ofioliti, in stampa.
Keller, E.A., Pinter, N., (1996) - Active Tectonics: Earthquake, Uplift, and Landscape. Prentice Hall, Upper Saddle
River, NJ. pp. 338.
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Kirby E. & Whipple K. (2001) - Quantifying differential rock-uplift rates via stream profile analysis. Geology, 29,
415-418.
Martino C. & Schiattarella M. (2006) - Aspetti morfotettonici dell’evoluzione geomorfologica della valle del
Melandro (Appennino campano-lucano). Il Quaternario, 19, 119-128.
Martino C. & Schiattarella M. (2008) - Relationships among climate, uplift and palaeo-landslides generation in the
Melandro River basin, southern Apennines, Italy. Physics and Chemistry of the Earth, in stampa.
Pazzaglia F.J. & Brandon M.T. (2001) - A fluvial record of long-term steady-state uplift and erosion across the
Cascadia forearc high, Western Washington State. Am. Journ. of Sc., 301, 385-431.
Schiattarella M., Beneduce P., Di Leo P., Giano S.I., Giannandrea P., Principe C. (2005) - Assetto strutturale ed
evoluzione morfotettonica quaternaria del vulcano del Monte Vulture (Appennino Lucano). Boll. Soc. Geol. It., 124,
543-562.
Schiattarella M., Beneduce P., Pascale S. (2004) - Comparazione tra i tassi di erosione e sollevamento
dell’Appennino lucano: l’esempio della Fiumara di Tito e Picerno. Boll. A.I.C., 121-122, 367-385.
Schiattarella M., Di Leo P., Beneduce P., Giano S.I. (2003) – Quaternary uplift vs tectonic loading: a case-study from
the Lucanian Apennine, southern Italy. Quaternary International, 101-102, 239-251.
Schiattarella M., Di Leo P., Beneduce P., Giano S.I., Martino C. (2006) – Tectonically driven exhumation of a young
orogen: an example from southern Apennines, Italy. In: Willett, S.D., Hovius, N., Brandon, M.T., and Fisher, D.,
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bacino del Mercure (Confine Calabro-Lucano). Il Quaternario, 7, 613-626.
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DISCRETE ELEMENT SIMULATION OF ROCK-AND-SOIL AVALANCHES:
1. THEORY AND COMPUTATION
A. Taboada, N. Estrada
Montpellier - INSU - CNRS, cc. 60, Université Montpellier 2, Place E. Bataillon, 34095 Montpellier
(France) ([email protected])
Summary
We present a Contact Dynamics discrete element model for simulating initiation and propagation of rock
avalanches, integrating the hillslope geometry, the Mohr-Coulomb rock behavior, the pore pressure
before avalanche triggering, and the avalanche trigger. Avalanche propagation is modeled as a dense
granular flow of dry frictional particles. Based on granular physics and shear experiments, we review
some of the theories for the unexpectedly long runout of rock avalanches. Different causes are evoked,
according to the strength (strong or weak) of the slip surface relative to the bulk. The mechanical
fluidization and the acoustic fluidization theories state that agitation of rock particles reduces frictional
strength, increasing runout. Conversely, granular mechanics proves that, as shear strain rate increases,
granular material becomes more agitated, more dissipative, and more resistant. Another theory states that
dynamic fragmentation of clasts creates an isotropic pressure that dilates the rock mass, driving longer
runout. In contrast, granular mechanics suggests that fragmentation induces a stress drop, a contraction of
granular material, and energy dissipation through inelastic collisions. Long runout is enhanced for
column-like rock masses collapsing from steep hillslopes. Finally, long runout may also be linked to
thermal weakening mechanisms along the slip surface (e.g., thermal pressurization, shear melting, and
others), which may lower drastically the shear strength. The model is illustrated by a hypothetical
example of rainfall-triggered avalanche mobilizing shallow monoclinal layers. Several phases are
identified, including slope failure, avalanche triggering resulting from slip weakening, and avalanche
propagation in which rocks are folded and sheared.
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