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Terra Nova, 00, 1–7, 2010 The C-isotope composition of a Miocene carbonate succession from the Latium-Abruzzi sector of the Central Apennines was studied to evaluate the influence of local vs . global factors in changing δ13C. We propose that the Oligo-Miocene igneous activity of the Western Mediterranean and the closure of the Indo-Pacific connection influenced climate change and Mediterranean sea-water circulation. The huge Aquitanian–Burdigalian volcanic activity during the formation of the Ligurian–Provençal Basin, with related increase in atmospheric CO2, may have accelerated weathering and hydrological cycling of nutrient inputs in coastal environments. The closure of the Indo-Pacific connection altered the circulation by changing and reversing the western exchange flow. The existence of warm and seasonally humid climate favoured the development of estuarine circulation, which was to lead to a dramatic increase in productivity in the euphotic zone. [ABSTRACT FROM AUTHOR]

Earth scientists have searched for signs of microscopic life in ancient samples of permafrost, ice, deep-sea sediments, amber, salt and chert. Until now, evidence of cyanobacteria has not been reported in any studies of ancient DNA older than a few thousand years. Here, we investigate morphologically, biochemically and genetically primary evaporites deposited in situ during the late Miocene (Messinian) Salinity Crisis from the north-eastern Apennines of Italy. The evaporites contain fossilized bacterial structures having identical morphological forms as modern microbes. We successfully extracted and amplified genetic material belonging to ancient cyanobacteria from gypsum crystals dating back to 5.910–5.816 Ma, when the Mediterranean became a giant hypersaline brine pool. This finding represents the oldest ancient cyanobacterial DNA to date. Our clone library and its phylogenetic comparison with present cyanobacterial populations point to a marine origin for the depositional basin. This investigation opens the possibility of including fossil cyanobacterial DNA into the palaeo-reconstruction of various environments and could also be used to quantify the ecological importance of cyanobacteria through geological time. These genetic markers serve as biosignatures providing important clues about ancient life and begin a new discussion concerning the debate on the origin of late Miocene evaporites in the Mediterranean. [ABSTRACT FROM AUTHOR]

Apatite fission-track analyses on samples from eastern Sardinia document a complex tectonic history, whose reconstruction is problematic because of the reactivation of faults and structures at different times from Jurassic to Miocene. The oldest ages (150–154 Ma) have been detected on the southern margin of the Gulf of Orosei and are related to the extensional tectonics that characterize the European passive margin during Early and Middle Jurassic times. Thermal modelling of these data allows reconstruction of the burial history of the Mesozoic basin and estimation of a sedimentary thickness of 2000 m. Part of these sediments was eroded during the following uplift, documented by mid-Cretaceous fission-track ages. A further exhumation episode of Eocene age has been revealed by fission-track data on granite samples, and has been inferred to be related to the Alpine orogenic phase. This tectonic episode caused the exhumation of crustal blocks bound by faults that were finally reactivated during the Late Oligocene–Early Miocene. [ABSTRACT FROM AUTHOR]

This paper reports the results of a study of more than 2400 specimens in the collection of fossil vertebrates from Fiume Santo in north-west Sardinia. This locality represents the westernmost documentation of the Tusco-Sardinian palaeobioprovince, which was in existence during the late Tortonian in the North Tyrrhenian area. During the Tortonian, the region that presently corresponds to southern Tuscany and the Sardinian Massif (Central Italy) was occupied by a complex of large islands characterised by endemic vertebrate populations. Morphological features, adaptations and trophic structure (e.g. low diversity and scarce carnivore taxa), mainly in the mammal faunas, attest to a long period of isolation from the continental palaeobioprovinces of the Mediterranean and Central Europe. The greatest numbers of fossil remains of the well-known endemic Oreopithecus fauna of the so called V0–V2 assemblages, are found at several sites in southern Tuscany (e.g. Montebamboli, Casteani, Baccinello). In Sardinia this endemic fauna occurs only at the Fiume Santo locality, from which 11 taxa have been recognized: Crocodylia indet., Chelonii indet., Oreopithecus bambolii, Mustelidae indet., Eumaiochoerus cf. E. etruscus, Umbrotherium azzarolii gen. et sp. nov., Tyrrhenotragus gracillimus, Bovidae gen. et sp. indet. (?Neotragini), Maremmia cf. M. lorenzi, Etruria viallii gen. et sp. nov., Turritragus casteanensis gen. et sp. nov. Analysis of these fossils and comparison with material from localities in Tuscany has led to a re-evaluation of the latter and to the description of three new endemic taxa among the ruminants. [ABSTRACT FROM AUTHOR]

Miocene volcanic rocks from northeast of Lopburi, Thailand, include a suite of highly potassic (<6.3% K2O) perlitic rhyolites that are similar chemically to rhyolites from Sardinia (which are also perlitic) and Vulcano. Electron microprobe analysis using a defocussed beam has shown that glass compositions contain up to 12.9% K2O (0.9% Na2O), and within the same samples spherulites are enriched in Na2O (<6.2%) and depleted in K2O (2.1%). The perlitic rhyolites contain up to 4% water of meteoric origin; from Fourier transform infra-red spectroscopy data, expansion on heating involves a reduction in both hydroxyl and molecular water contents. When expanded using a laboratory test furnace, specific gravities as low as 26 kg/m3 have been achieved for a 0.15–0.3-mm feed size fraction (reference perlite ores from Milos and Sardinia gave 47 and 33 kg/m3, respectively), and 10 kg/m3 for a 0.5–1-mm fraction separated after expansion. Expansion involves the loss of fluorine from the perlite, presumably as HF; unexpanded perlite contains 90–550 mg/kg F, which is reduced on expansion by 4–65%. Water-soluble fluorine after expansion is increased by a factor of 10 up to 3.3 mg/kg. Expansion also increases the availability of K to plants by a factor of up to 6, with a maximum available K content of 1245 mg K/kg perlite. This contrasts markedly with the chemically inert character of other, commercial, perlites, suggesting that the distinctive K-enrichment of the perlitic rhyolite has given a raw material capable of generating products with nutritional functionality for plant growers. [ABSTRACT FROM AUTHOR]

Metre-scale siliciclastic–carbonate cycles are the basic depositional motif of the lower Miocene Guadagnolo Formation outcropping in the central Apennines. The mechanisms which formed the mixed-lithology cycles are still a matter of debate. The mixed siliciclastic–carbonate system discussed in this paper provides a new case study to illustrate the role of orbital forcing in controlling the facies evolution and cyclic stacking of small-scale sequences deposited on the outer sector of a ramp. Two sections are discussed that display mixed siliciclastics and carbonates arranged in upward-shallowing cycles. Each cycle shows an upward decrease in the terrigenous input and a parallel increase in benthic fauna. Time-series analyses indicate the cyclic carbonate-terrigenous pattern to be largely controlled by orbital forcing in the Milankovitch frequency band. Coupling of climate change and sea-level fluctuations in tune with orbital cycles are proposed as driving mechanisms. [ABSTRACT FROM AUTHOR]

Foreland contraction and hinterland extension in the Southern Apennines orogen of Italy produced a complex spatial and temporal pattern of vertical and horizontal displacement. Remarkably, Late Miocene to mid-Pleistocene foreland migration of the contractional front at∼16 mm yr−1 was not accompanied by uplift and the frontal thrust belt remained at or below sea level. Only following a mid-Pleistocene reduction in horizontal displacement did the frontal thrust belt and foreland begin uplift at∼0.5 mm yr−1, a rate that increased to∼1 mm yr−1 after 125 ka. Although the extensional hinterland experienced net subsidence during formation of the Tyrrhenian basin, an extensional transition zone adjacent to the frontal thrust belt records sustained uplift at∼0.3 mm yr−1. The interaction of preexisting crustal structure and deep tectonic processes resulted in time-integrated displacement rates suggesting steady-state deformation for periods of 106 years. Displacement rate changes were abrupt and occurred over intervals of 105 years or less.Terra Nova, 00, 1–6, 2005 [ABSTRACT FROM AUTHOR]

ABSTRACT In the foothills of the Northern Apennines mud volcanoes are locally aligned along active normal faults, which allow surface leakage of fluids derived from deep sources (>3–6 km). The chemical and isotopic analysis of the fluids of a mud volcano, coupled with the reconstruction of its geological setting, allowed an investigation of the processes of migration and fluid flow. The fault system associated with the Regnano mud volcano drains a deep Miocene reservoir (foredeep marine deposits), which supplies formation water and thermogenic methane that has migrated from underlying Mesozoic carbonates. The muds from the volcano contain late Eocene microfossils and are extruded only during paroxysmal events. They have a shallower origin (about 1 km) from the base of Tertiary marine deposits deposited upon the upper tectonic nappe of the chain (Ligurian unit). This case study suggests that normal faults are very effective in controlling surface emissions. [ABSTRACT FROM AUTHOR]

Multiple intraformational discordances, recognized in the Tortonian (Upper Miocene) type area, occur at the top of a shelf sequence, directly overlain by slope sediments. The discordances display smooth, concave upward lower surfaces and are covered by sediments identical to the surrounding strata. Inferred lateral extent of single discordances is 500-700 m. Thickness of sediments overlying the discordances ranges from 5 to 25 m. The intraformational discordances are interpreted as scare formed by downslope sliding of whole packets of strata. The slumps may have been triggered by tectonic oversteepening of shelf sedimenls due to tilting of the sea floor. The slump scars appear comparable in position and size to some small scale modern examples recorded on margins near the shelf-break. [ABSTRACT FROM AUTHOR]

Ten samples from a Late Messinian section measured at Capo Rossello, a few hundred metres laterally from and stratigraphically, immediately below the Miocene Pliocene boundary stratotype, have been invesitigated by various techniques: carbonate content, grain-size analysis, loss on ignition, clay mineral composition, frequency of euryhaline ostracods, Two lithological sub-units, with different palaeoenvironmental implications, are recognized. Both sub-units were deposited after the termination of evaporitic conditions, and immediately after deposition of an ash fall tuff. The lower unit is the Congeria marl which yields the lago-mare' faunal assemblage, the autochthony of which is supported by biometrical analysis of Cyprides agrigentina, indicating brackish, shallow-water conditions with Paratethyan affinities, and the upper, the Arenazzolo, a thin sandy unit indicating a higher' energy environment whose duration is estimated at some thousand years. Marine faunas yielded by the Arenazzolo are interpreted as allochthonous, Sedimentary slructures suggest a littoral setting at the edge of the lake, or a delta lobe. The main environmental change occurs at the base of the immediately overlying Trubi Formation. where open marine condilions indicative of oceanic depths mark the termination of the Messinian salinity crisis. [ABSTRACT FROM AUTHOR]

Fission-track thermochronology applied to the nappe pile of the Calabrian Arc of southern Italy, particularly within the continental basement rocks, has provided important new constraints on the nature of some of the tectonic contacts. In southern Calabria an important phase of lower Miocene crustal extension is indicated. In northern Calabria no Oligocene or younger extension is seen. Here, the emplacement of continental basement rocks with Alpine metamorphism over ophiolitic rocks with little or no metamorphism is constrained as a thrust of lower to middle Miocene age related to collision of the Calabrian Arc with the Adria plate margin. It is proposed that reduction in the plate convergence velocity during collision of a retreating subduction zone with a continental margin is, at least partly, an explanation for the onset of extension in southern Calabria during the Miocene. [ABSTRACT FROM AUTHOR]