3 0° N A T I O N A L M E E T I N G G N G T S (GRUPPO NAZIONALE DI GEOFISICA DELLA TERRA SOLIDA)

Trieste, November 14-17 2011, Stazione Marittima Molo Bersaglieri Session 1.2: “Riconoscimento del quadro geodinamico/tettonico post-Pleistocene Medio nella catena appenninica” - Convenor: E. Mantovani (Univ., Siena), L. Piccardi (CNR, Florence)

PLEISTO-HOLOCENIC TRANSTENSIVE FAULTING IN THE CLOSURE SECTOR OF THE WESTERN TELESINA VALLEY (CAMPANIAN APENNINES )

S.SORECA(1), N. Rinaldo(2), A. Nisco(3)

(1) = Freelancer geologist, Ordine Geologi Campania, Member of PROIDRO Project (PROfessionisti del monitoraggio ambientale e la sicurezza IDROgeologica) at Università d. Studi della Basilicata, salvatore.soreca@gmail.com (2) = Biotechnologist and PhD in Scienze della Terra e della Vita, BIOGEM, nicolarinaldo@libero.it (3) = Freelancer geologist, annanisco@hotmail.it

Aim & previous works Area of interest

Materials & methods

References Satellitar photos Geological & structural overview Historical seismicity INGV Screening springs (Soreca&Rinaldo 2010) Informatic support Structural model

INPUT (DATA COLLECTION & PREVIOUS WORKS) IN SITU INSPECTION DATA ELABORATION OUTPUT

Choice of investigations

Comparison with the starting idea

Towards a global vision (theory)

Corrections Corrections

Data collection on the field

The area is localized in the W of the Telese semigraben. There are transtensive faults and a ENE-oriented thrust maybe evolved to lanf in the E of Montepugliano. Carbonates lie on NNE-oriented langhian thrust (Camposauro thrust) over Red Flysch and discordant Caiazzo Sandstones. Montepugliano (internal southern portion of the Matese thrust) is separated from those ones by a shear zone. In the Tortonian the compressive wave migrates to NE; an extensional NE-SW tensor accomodates conjugate normal faults of first generation striking NW-SE and NE-SW. The pliocenic anticlockwise rotor generates a second network and induces right transtension on apenninic axis and left on antiapenninic ones rearranged according to the new stress field. The left NE-SW superimposed transtensive faults, are transferfaults between the two thrusts. Pleistocenic reactivation is visible in breccias of first and second generation (same age at Colle Pizzuto and Montepugliano), slopes and fault planes. The two oldest alluvial terrace systems of Calore River are tilted with similar dip on the right and left riverbank, like also ignimbrites of Torrente Seneta. The hypermineralized springwater shows thermic and hydrochemical anomaly along the transtensive F.na Bolla-Rio Grassano fault and intersections; increase of 3-5°C with high values of fix residue, hardness and pH are typical for F.na Bolla, F.na Sala, F.na S. Antuono, F.na San Marco, Terme di Telese and Rio Grassano. F.na Bolla, F.na S. Antuono and Terme di Telese, connected to the deep “Calore Fault”, show sulphureous-ferrous-alkaliterrous water with H2S and CO2 and dissolved O2 at hypoxic levels; the other ones, at the junction with left transtensive faults, are bicarbonate-alkaliterrous, low in H2S and normal in dissolved O2.

NEOTECTONICS HYPERKARST GEOSTRUCTURAL SETTING

The ancient alluvial terraces, of pleistocenic age, show tilting in the W sector of the Telesina Valley; in particular way at F.na Sala the terraces dip 15° NW-wards at both sides of Calore River, due to an apenninic fault that borders Colle Pizzuto; also ignimbritic deposits of Tufo Grigio Campano (36 ka) are deformed in the valley of Torrente Seneta.

The presence of hyperkarstic subphosion is testified by fields of cover sinkholes lined up along several fault systems and hypermineralized hypothermal springs situated adjacent to those ones. The pleisto- holocenic reactivation has disconnected many uvalas and the subphosion actually migrates into the plain around the Lake of Telese (doline); triassic and messinian euxinic deposits contribute to make thermomineral water more aggressive.

Colle Pizzuto is bounded by a thick detrital belt made up of two orders of partially reactivated tectonic-sedimentary breccias. Large fault planes testify the recent reactivation of the slope. The same situation can be observed at Montepugliano. The fan bodies of Solopaca are dissected by fault scarps with superimposed hydrographic network. The reactivated detrital glacis reaches the Calore River in abrupt way, without gradual slope softening.

Conclusions

THE STUDIED AREA SHOWS A VERY COMPLEX RECENT TECTONIC ACTIVITY THAT CAN BE RELATED TO 4 SCCESSIVE STEPS THAT, SINCE THE END OF THE MIOCENE AND THE ACTUAL GENERATED A NETWORK OF 4 FAMILIES OF DIP-SLIP AND OBLIQUE FAULTS DUE TO PROGRESSIVE GENERATIONAL PHASES; WHILE THE CHAIN ROTATED ANTICLOCKWISE NEW FAULTS GOT ORIENTED NW-SE AND NE-SW PRODUCING DIP-SLIP KINEMATICS, WHILE THE PRE-EXISTING ONES FOLLOWED THE STRESS TENSOR THROUGH TRANSTENSIVE COMPONENTS. WE FOUND THAT RECENT TECTONIC ACTIVITY INVOLVES FAULTS OF VARIOUS GENERATION, THUS IT IS NOT POSSIBLE, ACTUALLY, TO EXCLUDE A PRIORI A POTENTIAL REACTIVATION OF ANY LOCAL TECTONIC AXIS, EVEN IF MAJOR SEISMICITY IS DUE TO NNW-SSE EXTENSIONAL FAULTS, OF NEW GENERATION. HISTORICAL EARTHQUAKES, ACTUAL SEISMICITY, STRATIGRAPHICAL SETTING OF PLEISTO-HOLOCENIC IGNIMBRITE PLATES AND ALLUVIAL TERRACES AND HYPERKARSTIC SUBPHOSION FROM HYPOTHERMAL SPRINGS AND FIELDS OF COVER-SINKHOLES ARE CLUES THAT, INTERRELATED EACH OTHER, ALLOW TO CONLUDE THAT THE LOCAL FAULTS SUBSTANCIALLY CONTRIBUTE TO THE STRUCTURAL MODELLING TODAY STILL IN PROGRESS, THROUGH EXTENSIONAL AND TRANSTENSIONAL ACCOMODATION ACCORDING TO THE KINEMATICS SUGGESTED IN THE PRESENT MODEL.

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FROM THE ELABORATION OF DATA TO THE BUILDING OF A SCIENTIFIC MODEL: NEOTECTONICS OF TELESINA VALLEY There are 4 orders of high dipping faults and a hypothetical buried thrust. The NE front of Montepugliano is tectonically overthrusting the Red Flysch; according to the model the structure is part of a unique internal thrust of serravallian age that spans to the NNE front of the Mounts Camposauro and Pentime; subsequently dissected by postmiocenic transfer faults. The high dipping faults show dip-slip, strike-slip and intermediate kynematics. The 4 preferential orientations show uniform strikes with low standard deviation, thus we believe that the accomodation of the structural network to the plio-pleistocenic anticlockwise rotation of this area may have occurred stepwise (4 successive well distinguishable phases) and not in a gradual way, lacking at all intermediate orientations that could suggest partial rebalancing of the stress field. The tectonic processes, the orientation of the stress tensor, the age of deformations and the hypotized average focal mechanisms (stress drops) are shown below. The analysis of the network individuates 4 different generation families, whose age of genesis is surely progressive, although nothing we can say about their actual state of activity. The only sure clues are the recent seismic sequences provided by INGV (site Iside): we computed 4 since 2005 until 2011 in the studied area and they may belong both to transtensive than extensive faults and they would tesify that actually seismic activity has intermediate magnitudo involving not only fault systems of last generation. As previously verified (Soreca & Rinaldo, 2010) recent juvenile activity involved the 6 springs localized along the transtensive intersections of the hypotized “Calore Fault” and induced hyperkarst in the fields of cover sinkholes. Those ones, localized along the main recent tectonic alignments as visible in the map, are no more active at higher altitudes than 15-20 m above the actual riverplain of Telese (75-80 m a.s.l.), because the reactivation of slopes definitively dissected the bottom of the dolines and uvalas from the vadose karstic network, rensponsible of subphosion. Actually new cover sinkholes are in formation along the alignments that cross the travertine plate and the pleisto-holocenic deposits on which the town of Telese Terme has been built.

The Telesina Valley is a large plio-quaternary W-E oriented semigraben made up of a bright internal apenninic plain, crossed by the River Calore Irpino, that separates the Matese Massif in the N from Camposauro in the S. This paper analyzes the western sector of the Valley, between the villages of Telese Terme, Solopaca and Castelvenere; in particular way a left transfer zone due to transtensive antiapenninic faults originated along the Pliocene and reactivated in many successive tectonic phases has been studied.

Geodynamics in the Telesina Valley have been reconstucted. Cover-sinkholes and fault- springs show a hyperkarstic halo. Supposing active subphosion, we completed the structural scheme along the left shear zone, modelling interactions between neotectonics, fluvial karst and hydrochemistry. A previous study (Soreca & Rinaldo, 2010) correlates hydrochemistry and neotectonics, so confirming hyperkarst by juvenile upwelling along The “Calore Fault” and the left transfer faults of the shear zone.

Fig.1 | Geological sketch of the Telesina Valley Fig.2 | Structural step by step evolution from Pliocene to actual (focal mechanism) Fig.3 | Fig.4 | Earthquakes that occurred since 2005 until 2011 in the area Fig.3 | Analysis of the network of plio-quaternary faults Tab.1 | Structural parameters of the main tectonic alignments

“Neotectonic model for the Telesina Valley” (Soreca & Rinaldo, 2010) vs the present work - Analogies & differences:

In a previous work (Soreca&Rinaldo 2010, GNGTS) we screened the hydrochemical behaviour of 6 springs aligned along the hypotized “Calore Fault”. The neotectonic model we arranged showed how tectonics in the western Telesina Valley affected the hydrogeological system producing thermomineralization of springwater and hyperkarstic subphosion. Those considerations have been confirmed during the present study. Actually we focused our researches on the whole structural network, trying to link the hypothermal activity and hyperkarst along the “Calore Fault” and intersections with the seismic parameters of the area. To do this we made a field recognition and we analyzed all data sets concerning recent seismicity. It results that local seismicity affects the intersections of the “Calore Fault” with transtensive alignments; recent earthquakes of low magnitude occurred along the last generated normal fault system, but also along older fault sets. Actually the extensional tensor produces NE-SW dilatation.

WITHIN THE IN SITU INSPECTION AIMED TO LOCALIZE AND DESCRIBE MORPHOSTRUCTURAL ELEMENTS NOT VISIBLE FROM AIR PHOTO, FOLLOWING ABBREVIATIONS HAVE BEEN ATTRIBUTED: TR (RIGHT TRANSTENSIONAL FAULT), TL (LEFT TRANSTENSIONAL FAULT), N (NORMAL FAULT), L (LANF), WITH PROGRESSIVE APEX; FAMILY IS INDICATED BY ROMAN NUMBER. WHERE POSSIBLE FAULT PLANE ORIENTATION HAS BEEN MEASURED. A GRADIENT OF THE DEFORMATIVE TENSOR SINCE LATE PLIOCENE UNTIL TODAY HAS BEEN RECONSTRUCTED. SEISMIC ACTIVITY HAS BEEN INFERRED BY HYPOCENTRAL LOCALIZATION OF RECENT LOCAL EVENTS (2005-2011).