In this paper we illustrate the stratigraphic and structural features of the Sibillini Mountains on the basis of a 1:40.000 geological map. Following the “Foglio 132 Norcia” (Geological Map of Italy at 1:100.000 scale; SCARSELLA, 1941), this new geological map is the first cartographic document that covers the whole area of the Sibillini Mts. This area is key for understanding the geological evolution of the external zones of the Apennine orogen, mostly owing to the pronounced structural elevation of the Apennine ridge at the Sibillini Mts. area. This allowed us to: a) carry out stratigraphic and structural analyses for the Umbria-Marche sedimentary cover to the oldest units; b) analyze the paleo-tectonic setting of this sector of the Afro-Adriatic continental margin and the behavior of pre-existing structures during the subsequent deformation events; c) investigate in depth the major Apennine thrust front (“Sibillini Mountains Thrust”) exposed in several sites (Fiastrone, Ambro, Tenna and Tronto valley) and its relationship with the units of the adjacent Messinian foredeep

Waters from an extensive sulfide-rich aquifer emerge in the Frasassi cave system, where they mix with oxygen-rich percolating water and cave air over a large surface area. The actively forming cave complex hosts a microbial community, including conspicuous white biofilms coating surfaces in cave streams, that is isolated from surface sources of C and N. Two distinct biofilm morphologies were observed in the streams over a 4-year period. Bacterial 16S rDNA libraries were constructed from samples of each biofilm type collected from Grotta Sulfurea in 2002. ␤-, ␥-, ␦-, and -proteobacteria in sulfur-cycling clades accounted for >75% of clones in both biofilms. Sulfate-reducing and sulfur-disproportionating ␦-proteobacterial sequences in the clone libraries were abundant and diverse (34% of phylotypes). Biofilm samples of both types were later collected at the same location and at an additional sample site in Ramo Sulfureo and examined, using fluorescence in situ hybridization (FISH). The biomass of all six stream biofilms was dominated by filamentous ␥-proteobacteria with Beggiatoa-like and/or Thiothrix-like cells containing abundant sulfur inclusions. The biomass of -proteobacteria detected using FISH was consistently small, ranging from 0 to less than 15% of the total biomass. Our results suggest that S cycling within the stream biofilms is an important feature of the cave biogeochemistry. Such cycling represents positive biological feedback to sulfuric acid speleogenesis and related processes that create subsurface porosity in carbonate rocks.Sulfidic caves form in carbonate rocks where sulfide-rich waters interact with oxygen at the water table or at subterranean springs. The caves form as a result of sulfuric acid production (equation 1) from microbial or abiotic sulfur oxidation. The sulfuric acid reacts with carbonate host rock to form gypsum and carbonic acid (equation 2).(1)Some of the longest caves known are thought to have formed by this process, including Lechugilla Cave in New Mexico, with 184 km of passages (17). Actively forming sulfidic caves are uncommon but intensely valuable as natural laboratories to understand factors influencing cave formation and resulting biological, geochemical, and isotopic signatures. Active sulfidic caves can host biogeochemically isolated ecosystems based entirely on microbial lithoautotrophic primary productivity (16,38). These ecosystems are aphotic, terrestrial, subsurface environments comparable to sulfureta at hot springs and deep sea vents (10) and are of considerable interest as analogs for microbially dominated, early earth biotic communities such as those that might have developed after the initial rise of oxygen in the early Proterozoic era.Available information from culturing, fluorescence in situ hybridization (FISH), and 16S rDNA libraries suggests that ε-and ␥-proteobacteria are important biofilm-forming groups in the sulfidic cave waters studied to date. Microbial biofilms in Lower Kane Cave (Wyoming) springs and streams are dominated by filamentous ε-prot...

Abstract. Thrust propagation through previously faulted continental margins may result in fold and thrust belts whose structure is strongly controlled by the inherited basin architecture. A detailed geological study has been carried out in the external zone of the Umbria-Marche Apennines, from Monte San Vicino to the north, to Montagna dei Fiori to the south. Stratigraphic and structural data, together with the construction of a series of balanced and restored geological sections, point out the fundamental role played by the preorogenic basin architecture in controlling the geometry and evolution of the fold and thrust belt. Pre-thrusting structures include not only those inherited from the Mesozoic rifted continental margin, but also synsedimentary faults associated with Miocene extension which occurred ahead of the advancing thrust front. The latter structures produced important facies and thickness variations in the units deposited during the late Burdigalian-early Messinian, pre-evaporitic stages of foredeep development. In the southern sector (Montagna dei Fiori), high values of Messinian regional subsidence, bathymetry and sedimentation rate overcome the effects of synsedimentary extensional tectonics, which is best recorded in pre-Messinian sequences. On the other hand, Messinian regional subsidence was significantly less in the northern sector (Monte San Vicino). Here, several minor sub-basins developed within the foredeep, generally reaching evaporitic conditions during the middle Messinian (marked by the deposition of the Gessoso-solfifera Fm). In this area, a major control by pre-thrusting normal faults on sedimentation is recorded in the foredeep siliciclastic sequences. Late Burdigalian-early Messinian extension, possibly associated with flexure of the foreland lithosphere, peripheral bulge uplift and/or foreland tectonic activity, was followed by a late Messinian (post-evaporitic) contractional episode of regional extent. During shortening, inversion of preexisting MioceneCorrespondence to: S. Mazzoli (s.mazzoli@geo.uniurb.it) extensional structures was quite limited. Hanging wall basin fills were retained and pre-thrusting faults show very limited or no reversal of slip. However, these faults and their hanging wall basin fills are generally deformed by buttressing phenomena, and fault planes are often tilted and/or locally reactivated in strike-slip. The present-day structure is dominated by newly-formed thrusts that cut across the preexisting extensional architecture, which is in general quite well preserved within different thrust sheets.

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The oxidation of hydrogen sulfide (H 2 S) has led to the formation of some of the world's largest caves through a process known as sulfuric acid speleogenesis (SAS). Here we present a multi-year study of the large, sulfidic, and actively-forming Frasassi cave system, Italy. We show that despite the presence of abundant sulfide-oxidizing biofilms in Frasassi streams, H 2 S(g) degassing to the cave atmosphere was the major sink for dissolved sulfide. Degassing rates ranged from 0.9 to 80 μmol m −2 s −1 , whereas microbial oxidation rates were between 0.15 and 2.0 μmol m −2 s −1 . Furthermore, microsensor measurements showed that sulfuric acid is not a major end product of microbial sulfide oxidation in the streams. Our results suggest that subaerial SAS will be important for karstification, and more important than subaqueous SAS, wherever ground waters with high sulfide concentrations emerge as flowing streams in contact with cave air.