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| Titel |
Fault and fluid interaction in the Bradano Trough, southern Italy |
| VerfasserIn |
Rosa Sinisi, Angela Vita Petrullo, Fabrizio Agosta, Michele Paternoster, Claudia Belviso, Fausto Grassa |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101378
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| Publikation (Nr.) |
 EGU/EGU2015-505.pdf |
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| Zusammenfassung |
| We report the preliminary results of a multidisciplinary study directed toward a better
understanding of the fault and fluid interaction in the Bradano Trough, the foredeep
basin of the southern Apennines fold-and-thrust belt, Italy. The work focuses on
fresh tuff deposits located along high-angle faults, which crosscut the foredeep
basin infill and the Middle Pleistocene Vulture pyroclastic rocks. Two sites have
been studied in detail by mean of integrated field and laboratory analyses. The
field survey aimed at deciphering both fault architecture (nature, distribution, and
relative timing of formation of the various structural elements) and stratigraphy
of the fresh tuff deposits. Laboratory investigation of representative samples of
both fresh tuff deposits and mineralized fault-related structural elements (e.g, veins
and fluid pipe conduits) targeted their textural, mineralogical and stable isotope
compositions.
The fresh tuff deposits consist of a few m-thick, either well-layered or massive,
carbonates that include fossils and syn-depositional calcite veins. These deposits grew
primarily by lateral progradation. Optical microscopy analysis is consistent with seven main
fresh tuff lithofacies, which all show the following similarities: (i) cement-supported
textures; (ii) presence of peloids, phyto- and bio-clasts, imprints of gastropods,
bivalves, and plants; (iii) occurrence of shrinkage pores, micropores, and fenestrae
that are either partially or totally filled by secondary calcite. XRPD analysis of
representative powders showed that calcite is the sole mineral phase except for quartz and
feldspar, which are detected in trace in a few samples. Similarly, the mineralogical
composition of the fault-related structural elements also shows minor amounts of
quartz. Both nature and origin of the quartz mineral will be investigated in a future
work.
13C and 18O signatures of representative fresh tuff powders are consistent with a
pronounced different isotope composition between the study deposits. Deposits present along
NW-SE directed normal faults that crosscut both foredeep infill and the underlying Apulian
carbonates are characterized by δ13C (PDB) values comprised between +2.3‰ and +5.7%
and δ18O (SMOW) values between +21.6‰ and +23.7‰. Differently, the fresh tuff deposit
located on top of a NE-SW strike-slip fault, which is envisioned as a lateral ramp of a
shallow thrust fault departing from a decollement located within the foredeep infill, is
characterized by δ13C (PDB) values between -2.7‰ and +1.5o and δ18O (SMOW)
values from +23.8‰ to +25.3oȦt all locations, a lack of relationships between
isotopic composition and fresh tuff texture features were documented. Based on
the equation proposed by Panichi and Tongiorgi (1976), the original δ13C values
of CO2 were calculated. Results of such a work show a dissimilar origin of CO2
present in the fresh tuff deposits. In fact, those located along the NW-SE normal
faults shows a mantle-derived CO2, which was likely channeled in the fault zones
through the 6 km-thick Apulian carbonates and the overlying foredeep basin infill.
Differently, the fresh tuff topping the NE-SW strike-slip fault shows a mixed CO2 source,
which includes both mantle and organic components, and therefore suggest the
entrapment of shallow, intra-basinal, organic-rich fluids within the latter strike-slip fault. |
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