Growth processes and melange formation in the southern Apennines accretionary wedge

Abstract The Southern Apennines owe their present geometry to the subduction of an Apulian continental lithospheric slab and are thus best interpreted as an accretionary wedge. Southward, the Apenninic thrust front branches on to the still active Ionian wedge, which is related to the present Calabro-Sicilian subduction. The interpretation of conventional seismic reflection profiles and exploration wells, combined with geologic field studies (biostratigraphy and structural geology), provide constraints for a geodynamic model for the post-Messinian growth of the Apenninic prism. Our model for the Apennines is a good analogy for submerged oceanic accretionary prisms; in both instances features such as out-of-sequence thrusts, underplating and duplexes are viewed as processes to explain the thickening of accretionary wedges. Syntectonic terrigenous deposits have accumulated in the synclines developed above the flats of Pliocene thrust faults. These depocenters represent piggy-back basins. Younger accretion at the eastern border of the accretionary wedge has led to a progressive uplifting and tilting of the already-emplaced thrust sheets, including a continous westward migration of the depocenters in the piggy-back basins during Pliocene and early Quaternary times. A contrary west-to-east migration of the depocenters locally occurred where preexisting flats of Pliocene thrust faults have been refolded rather than only being rotated. Dewatering processes and effects of overpressures on undercompacted sediment deformations can also be studied in the southern Apennines. Melanges and broken formations form an important component of the trench, apparently restricted to the base of tectonic nappes. Listric normal faults are a major structural element which preserves, in combination with the erosion of topographic highs and resedimentation in the piggy-back basins, a uniform geometric shape (critical taper) for the prism. The age and location of these distensive or gravitational effects are also discussed.

[1]  A. B. Hayward,et al.  Structural constraints on the Tertiary plate tectonic evolution of Italy , 1988 .

[2]  Jacques Malavieille.  Modelisation experimentale des chevauchements imbriques; application aux chaines de montagnes , 1984 .

[3]  I. Moretti,et al.  Late cenozoic subduction complex of Sicily , 1990 .

[4]  J. Burrus.  Review of geodynamic models for extensional basins; the paradox of stretching in the Gulf of Lions (Northwest Mediterranean) , 1989 .

[5]  J. Suppe,et al.  Mechanics of fold-and-thrust belts and accretionary wedges , 1983 .

[6]  J. Dewey.  Extensional collapse of orogens , 1988 .

[7]  Steven D. Knott,et al.  The Liguride Complex of Southern Italy —a Cretaceous to Paleogene accretionary wedge , 1987 .

[8]  R. Scarpa,et al.  Geometry of the neotectonic stress field in southern Italy: Geological and seismological evidence , 1982 .

[9]  G. Westbrook,et al.  Cross section of an accretionary wedge: Barbados Ridge complex , 1988 .

[10]  K. Kastens,et al.  ODP Leg 107 in the Tyrrhenian Sea: Insights into passive margin and back-arc basin evolution , 1988 .

[11]  T. Pescatore,et al.  Schema tettonico dell'Appennino campano-lucano , 1973 .

[12]  L. Royden,et al.  Deflection, gravity anomalies and tectonics of doubly subducted continental lithosphere: Adriatic and Ionian seas , 1988 .

[13]  Leigh H. Royden,et al.  Segmentation and configuration of subducted lithosphere in Italy: An important control on thrust-belt and foredeep-basin evolution , 1987 .

[14]  A. Deschamps,et al.  The Campania-Lucania (southern Italy) earthquake of 23 November 1980 , 1983 .

[15]  P. Scandone,et al.  Seismotectonics of the Calabrian arc , 1982 .

[16]  E. Silver,et al.  Comments on the growth of accretionary wedges , 1985 .

[17]  W. Ryan,et al.  Extension in the Tyrrhenian Sea and shortening in the Apennines as result of arc migration driven by sinking of the lithosphere , 1986 .

[18]  M. Boccaletti,et al.  The Calabrian Arc and the Ionian Sea in the dynamic evolution of the Central Mediterranean , 1984 .

[19]  P. Scandone,et al.  Structure and evolution of the Calabrian Arc , 1982 .

[20]  Colin F. Williams,et al.  Tectonics and hydrogeology of the northern Barbados Ridge: Results from Ocean Drilling Program Leg 110 , 1988 .

[21]  B. Biju-Duval,et al.  Growth of Accretionary Prisms: Tectonic Processes from Caribbean Examples , 1986 .

[22]  D. Karig.  Physical properties and mechanical state of accreted sediments in the Nankai Trough, Southwest Japan Arc , 1986 .

[23]  J. Platt.  Dynamics of orogenic wedges and the uplift of high-pressure metamorphic rocks , 1986 .

[24]  J. Mascle,et al.  The Tyrrhenian Sea before Leg 107 , 1987 .

[25]  I. Moretti,et al.  Forward modeling of the Southern Apennines , 1989 .