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1.
Various tectonic features are present in the Meso-Cenozoic basin units of the Sabina region (Central Apennines, Italy): Mio-Pliocene northeasterly verging thrusts are followed by Plio-Pleistocene, N-S oriented right-lateral strike-slip faults. Stable isotope geochemistry and examination of meso- and microstructures show that strain conditions differed through the course of tectonic history. Carbon and oxygen isotope analyses of the calate-filled extensional fractures, the sigmoidal veins present between stylolitic cleavage surfaces, and fault plane surfaces with differing motion, demonstrate those different geneses.
The "C/'" C of the older calcite-filling fractures (present both in the thrust and the strike-slip systems) suggests a deposition from shallow, fresh water circulation. Furthermore, the calcite fill of en echelon systems, that occur in the southernmost Plio-Pleistocene units, is clearly the result of a more recent, right-lateral strike-slip movement, connected with shallow water circulation within Mesozoic limestones.
The sigmoidal vein fills are derived from solid-state pressure solution processes which were the result of strike-slip movement. The deformation pattern related to the older thrust system is similar, but less intense; this also demonstrates general recrystallization processes in a closed system.
This suggests that the total shortening of the deformed sections is lower than that obtained on the basis of solution on stylolitic planes, because a sigruficant volume of dissolved carbonates remained in the system.
Stable isotope analysis also confirms that the deformational history of strongly cleaved rocks in the Sabina region took place in two phases and that extensional fractures formed before stylolithic planes, as suggested by structural and field observations. 相似文献
The "C/'" C of the older calcite-filling fractures (present both in the thrust and the strike-slip systems) suggests a deposition from shallow, fresh water circulation. Furthermore, the calcite fill of en echelon systems, that occur in the southernmost Plio-Pleistocene units, is clearly the result of a more recent, right-lateral strike-slip movement, connected with shallow water circulation within Mesozoic limestones.
The sigmoidal vein fills are derived from solid-state pressure solution processes which were the result of strike-slip movement. The deformation pattern related to the older thrust system is similar, but less intense; this also demonstrates general recrystallization processes in a closed system.
This suggests that the total shortening of the deformed sections is lower than that obtained on the basis of solution on stylolitic planes, because a sigruficant volume of dissolved carbonates remained in the system.
Stable isotope analysis also confirms that the deformational history of strongly cleaved rocks in the Sabina region took place in two phases and that extensional fractures formed before stylolithic planes, as suggested by structural and field observations. 相似文献
2.
Approximately 56% of 60 known nested calderas are pairs of nonintersecting subcircular structures with similar eccentricities. The consistent configuration suggests an interdependence in the formation of the two annular structures. This possibility has been investigated using 11 analogue models with sand (crust analogue) overlying silicone (magma analogue). Silicone withdrawal induces collapse within the sand, forming two concentric depressions: the first-formed inner depression, bordered by outward-dipping reverse ring faults (mean dip of 75°), induces the collapse of the outer depression, bordered by inward dipping, normal ring faults (mean dip of 84°). An original linear relationship is determined among the ratios between the diameters of the two depressions and the depth of the ring faults. Selected pairs of natural nested calderas show similar proportions, highlighting a consistent architecture. This suggests that some pairs of nonintersecting nested calderas result from a single collapse event. 相似文献
3.
Salvi S. Quattrocchi F. Brunori C. A. Doumaz F. Angelone M. Billi A. Buongiorno F. Funiciello R. Guerra M. Mele G. Pizzino L. Salvini F. 《Natural Hazards》1999,20(2-3):255-278
A priority task for correct environmental planningis to evaluate Natural Hazards, especially inhighly populated areas. In particular, thoroughinvestigations based on different Earth Sciencetechniques must be addressed for the Seismic HazardAssessment (SHA) in tectonically active areas. Notonly the management but also the multidisciplinaryanalysis of all the SHA-related data sets is bestperformed using a Geographic Information System. In this paper we show how a research-oriented GIS isbuilt and used in a practical case. The GeochemicalGeographic Information System (G2IS) wasdeveloped and applied to the Gargano promontory(southern Italy) in the framework of an EC researchproject, the Geochemical Seismic Zonation (GSZ)Project. This multidisciplinary – multiscalingpowerful tool is described in its structure, updatingprocedures and manipulation techniques. Preliminaryresults are presented on the detection of geochemically active fault zones and theircorrelation with remote sensing data and otherevidences of seismogenic structures. 相似文献
4.
The volcanic island of Ischia is located on the Tyrrhenian margin of Central Italy, characterized by Plio-Quaternary NW–SE- and NE–SW-trending extensional fractures. Ischia displays a resurgent dome uplifted by at least 800 m in the last 33 ka. Remote sensing and field data have been collected to study the structural setting of the island, the deformation pattern associated with resurgence and the superimposition of the regional and the resurgence-induced stress fields. NW–SE and NE–SW extensional fracture systems predominate throughout the island and around the resurgent block, suggesting a relationship with the regional extensional structures. These systems were formed before resurgence and were partly reactivated during resurgence. The reactivation of pre-existing regional systems during resurgence confined the extent of the uplifted area. N–S- and E–W-trending systems have been found exclusively at the borders of the dome and are interpreted as being induced by resurgence. The topmost resurgent block shows an octagonal shape in map view and is tilted at an angle of 15° around a NE–SW-trending horizontal axis; the block is partly bordered by high-angle, inward-dipping regional faults. More than 90% in volume of the volcanic products coeval with resurgence on Ischia have been erupted outside the resurgent block area, suggesting that the resurgence process locally replaced volcanic activity in the last 33 ka. 相似文献
5.
A.A. De Benedetti R. Funiciello G. Giordano G. Diano E. Caprilli M. Paterne 《Journal of Volcanology and Geothermal Research》2008
The polygenetic Albano maar is the most recent centre of the Colli Albani volcano, located just few kilometres to the south-east of Roma. Presently the maar hosts a 167.5 m deep crater lake, the deepest in Europe. The maar is to be considered quiescent, as phreatic activity is documented throughout the Holocene. This paper illustrates the close relationships between the activity of the maar and the history of settlement in the Roman region as recorded in the geology, archaeology, history and legends of the area. Severe fluctuations of the groundwater table and catastrophic overflows of the Lake Albano from the maar rim had occurred prior to and after the early prehistoric settlements dated in the maar area at the Eneolithic times (ca. III millennium B.C.). Repeated lahars occurred along the northwestern slope of the maar filling in the paleodrainage network and forming a vast plain. Paleohydraulic analyses on fluvial and lahar deposits originated from the Holocene phreatic activity of the Albano maar indicate sediment–water flows in excess of hundreds of cubic metres per second. Absolute age determinations of the paleosoil underlying one of the most recent deposits of the lahar succession at 5800 ± 100 yr B.P. (14C CAL) are in perfect agreement with the age of the overlying Eneolithic age settlements. The last catastrophic overflow is described in the Roman literature as a consequence of the anger of Poseidon against the Romans in 398 B.C. for their war against the Etruscans. In 394 B.C. the Romans decided to prevent the repetition of such events by the excavation through the maar crater wall of a 1.5 km long drain tunnel, which is still operational, keeping the lake 70 m below the lowest point of the maar rim. This tunnel drain may be regarded as the first prevention device for volcanic hazard in history and shows an unprecedented development of the engineering technology under the pressure of hazard perception. The surprising and still largely unknown results of this study are very important to redefine the hazard of the Roman region. 相似文献
6.
CLAUDIO Faccenna RENATO Funiciello† ‡ ALESSANDRO Bruni MASSIMO Mattei† LEONARDO Sagnotti‡ 《Basin Research》1994,6(1):35-46
During the Messinian—Pleistocene, the Peninsular Tyrrhenian margin underwent a NE—SW orientated stretching regime, with the formation of a NW—SE normal fault system and basins which are linked by NE—SW transfer fault zones. These fault zones border narrow and deep asymmetric basins. This paper uses geological and geophysical analysis (structural and stratigraphical data, seismic lines and anisotropy of magnetic susceptibility (AMS) data) to look at the evolution of one of these transfer-related basins, located south of Rome (Ardea basin). Comparison with other similar features indicates that the common characteristics of these transfer structures are: (i) the slip vector along the transfer fault is mostly dip-slip, which means that the local extensional direction is orthogonal to the regional extensional direction; (ii) development of a narrow and deep half-graben basin. 相似文献
7.
In the Central Mediterranean two back-arc basins, the Liguro-Provençal (LPb) and the Tyrrhenian basin (Tb), opened progressively and consecutively from the late Eocene–Oligocene to the present. Evolution in space and time of rifting and drifting processes, along three different transects across these basins, shows differences in the style of extension: LPb opened with the formation of a narrow, single rift, while in the Tb deformation and magmatism is spread over a wide area. Moreover at the Northern end of the Tb the locus of extension progressively migrated towards the east whereas in the Southern Tb the locus of extension and magmatism migrated inside the basin, inducing continental break-up and drifting of the previously formed older conjugate basins. We propose that these different styles of back-arc extension depend upon internal conditions, such as prerift rheology linked with its geological heritage, and external conditions, e.g. the style of subduction. 相似文献
8.
M. Porreca M. Mattei C. MacNiocaill G. Giordano E. McClelland R. Funiciello 《Bulletin of Volcanology》2008,70(7):877-893
The Peperino Albano (approximately 19–36 ka old) is a phreatomagmatic pyroclastic flow deposit, cropping out along the slopes
of the associated Albano maar (Colli Albani volcano, Italy). The deposit exhibits lateral and vertical transitions from valley
pond to veneer facies, as well as intracrater facies. We present the results of a paleomagnetic study of thermal remanent
magnetization (TRM) of the lithic clasts of the Peperino Albano ignimbrite that provide quantitative estimates of the range
of emplacement temperatures across the different facies of the ignimbrite. Emplacement temperatures estimated for the Peperino
Albano ignimbrite range between 240° and 350°C, with the temperatures defined in the intracrater facies being generally lower
than in the valley pond and veneer facies. This is possibly due to the large size of the sampled clasts in the intracrater
facies which, when coupled with low temperature at the vent, were not completely heated throughout their volume during emplacement.
The emplacement temperatures derived from the paleomagnetic results are in good agreement with the presence of un-burnt plants
at the base of the ignimbrite, indicating that the temperature of the pyroclastic flow was lower than the temperature of ignition
of wood. Paleomagnetic results from the Peperino Albano confirm the reliability of the paleomagnetic approach in defining
the thermal history of pyroclastic flow deposits. 相似文献
9.
Summary Occurrence of (Fe, Mg)-carpholite-bearing parageneses in metapelites from Giglio and Gorgona islands (Tuscan Archipelago,
Northern Tyrrhenian Sea) attests a continuity of blueschist metamorphism from Alpine Corsica to the Tuscan region. Numerous
fluid inclusions have been trapped in quartz crystals associated with (Fe, Mg)-carpholite fibers from the two blueschist metamorphic
cores. Textures of fluid inclusions (annular, semi-annular, negative crystal shaped), microthermometry (constancy of values)
and SEM investigations (presence of primary Fe-rich fluid/s) confirm that re-equilibration occurred during a nearly isothermal
(T not in excess of 300 °C) exhumation path.
Received February 22, 2000; revised version accepted July 17, 2000 相似文献
Zusammenfassung. Reequilibrierungstexturen von Flüssigkeitseinschlüssen in exhumierten Hochdruckgesteinen: Ein Beispiel aus dem toskanischen Archipel (Nordthyrrhenisches Meer) Das Auftreten von (Fe-Mg)-Karpholith-führenden Paragensen in Metapeliten auf den Inseln Giglio und Gorgona (toskanischer Archipel, Nordthyrrhenisches Meer) best?tigt die Kontinuit?t einer blauschieferfaziellen Metamorphose vom alpinen Korsika bis in die Toskana. Zahlreiche Flüssigkeitseinschlüsse wurden in Quarz eingeschlossen, der gemeinsam mit (Fe-Mg)-Karpholithfasern in diesen beiden blauschieferfaziellen metamorphen Kernen vorkommt. Die Textur der Einschlüsse (annular, semi-annular, negative Kristallgestalt), die Mikrothermometrie (Konstanz der Werte) und die SEM Untersuchungen (Vorhandensein prim?rer Fe-reicher Fluide) best?tigen, dass die Reequilibrierung entlang eines beinahe isothermen Exhumationspfades (T nicht über 300 °C) erfolgte.
Received February 22, 2000; revised version accepted July 17, 2000 相似文献
10.
Domenico Cosentino Paola Cipollari Letizia Di Bella Alessandra Esposito Costanza Faranda Guido Giordano Elsa Gliozzi Massimo Mattei Ilaria Mazzini Massimiliano Porreca Renato Funiciello 《Quaternary Research》2009,72(1):143-155
The historical site of the Monte Mario lower Pleistocene succession (Rome, Italy) is an important marker of the Pliocene/Pleistocene boundary. Recently, the Monte Mario site was excavated and restudied. A spectacular angular unconformity characterizes the contact between the Monte Vaticano and the Monte Mario formations, which marks the Pliocene/Pleistocene boundary. Biostratigraphical analyses carried out on ostracod, foraminifer, and calcareous nannofossil assemblages indicate an Early Pliocene age (topmost Zanclean, 3.81–3.70 Ma) for the underlying Monte Vaticano Formation, whereas the Monte Mario Formation has been dated as early Pleistocene (Santernian, 1.66–1.59 Ma). Palaeomagnetic analyses point to C2Ar and C1r2r polarity chrons for the Monte Vaticano and the Monte Mario formations, respectively. The Monte Mario Formation consists of two obliquity-forced depositional sequences (MM1 and MM2) characterized by transgressive systems tracts of littoral marine environments at depths, respectively, of 40–80 m and 15–20 m. The data obtained from foraminifer and ostracod assemblages allow us to reconstruct early Pleistocene relative sea-level changes near Rome. At the Plio/Pleistocene transition, a relative sea-level drop of at least 260 m occurred, as a result of both tectonic uplift of the central Tyrrhenian margin and glacio-eustatic changes linked to early Pleistocene glaciation (Marine Isotope Stage 58). 相似文献