Search results for "Sedimentary"
showing 10 items of 455 documents
Environmental geology and geochemistry of lake sediments (Holzmaar, Eifwl, Germany)
2008
Quaternary sediments of the lake Holzmaar comprise a well laminated, undisturbed sequence of diatomaceous gyttja, silt, clay laminites and tuff layers. The annually deposited gyttja has been dated by varve chronology yielding a continuous high-resolution time sequence for the Holocene and early Pleistocene. These organic-rich sediments provide an unique paleolimnological record on climatic changes, forest fires, volcanic eruptions, and anthropogenic influences on the sediment composition. Volcanic activity produced thin tephra layers (Laacher See Tephra 11,200±120 radiocarbon yrs BP; Ulmener Maar Tephra 9435±70 radiocarbon yrs BP) in the sedimentary column which possess elevated Ba, Sr, Zr,…
Evaporite karst in Sicily
2007
Karst areas are distributed over most of Sicily. The most widespread karst rocks are carbonates, particularly limestones, but karst phenomena can also be seen in evaporites and particularly in salt mines. This report provides an overview of evaporite karst in Sicily, along with a “case history” that shows some of the evaporite karst risks to the environment. In the centre and south of Sicily, a thick sequence of Messinian evaporite rocks are subject to dissolution from meteoric and formation waters. In areas where potassium salts and rock salts are being mined, some geomorphologic changes result from the drilling of boreholes and the collapse of underground mines, thus lowering or collapsin…
Soil CO2 degassing along tectonic structures of Mount Etna (Sicily): the Pernicana fault
1997
Abstract Carbon dioxide emissions from the soil have been investigated along lines of equally spaced sampling points perpendicular to the Pernicana fault on Mt Etna. Anomalous values of soil CO2 have been found not only along the fault plane, but also along directions parallel to it, both to the N and to the S of the main fault. The acquired data seem to reveal a shallow step-like geometry of the Pernicana fault system with parallel faults being generally not deeper than the interface between Etna's volcanic cover and its sedimentary basement (a few hundred meters). The distribution of the anomalous CO2 emissions has also revealed that the Pernicana fault continues at least as far as the Io…
The gastropod fauna of the Epipalaeolithic shell midden in the Vestibulo chamber of Nerja Cave (Málaga, southern Spain)
2011
The sedimentary record of the Vestibulo, Mina and Torca chambers in the ancient entrance of Nerja Cave (Malaga, southern Spain) developed between around 30 and 3.6 ka cal BP. The long record of human occupation shows a dominance of terrestrial snails associated with the Gravettian, with a continuation of these types in the Solutrean when marine shells begin to be introduced. During the Magdalenian, marine bivalves are dominant. Marine molluscs reach a maximum during the Epipalaeolithic, giving rise to a shell midden formed primarily by Mytilus edulis and diverse species of Patella. The Epipalaeolithic shell midden occurs in Unit 4 and can be dated to the PleistoceneeHolocene boundary. This …
Fluid-pressure controlled soft-bed deformation sequence beneath the surging Breiðamerkurjökull (Iceland, Little Ice Age).
2009
16 pages; International audience; The general subject of this paper is subglacial deformation beneath Breiðamerkurjökull, a surging Icelandic glacier. More specifically it discusses the evolution and the role of fluid pressure on the behaviour of subglacial sediments during deformation. During Little Ice Age maximum, the two outcrops studied, North Jökulsarlon (N-Jk) and Brennhola-Alda (BA), were located at 2550 m and 550 m respectively from the front of the Breiðamerkurjökull. Sedimentological analysis at the forefield of the glacier shows thick, coarse glaciofluvial deposits interbedded with thin, fine-grained shallow lacustrine/swamp deposits, overlain by a deformed till unit at N-Jk. BA…
Deep controls on foreland basin system evolution along the Sicilian fold and thrust belt
2015
Abstract Neogene-Quaternary wedge-top-basins arose during the Sicilian fold and thrust belt (FTB) build-up. The infilling sedimentary successions are: i) middle-upper Miocene silicoclastics succession, accommodated on top of the accreted Sicilide and Numidian flysch nappes; ii) upper Miocene-lower Pliocene deepening-upwards sediments unconformably overlying the inner Meso-Cenozoic deep-water, Imerese and Sicanian thrust units; iii) Upper Pliocene-Quaternary coastal-open shelf deposits unconformably covering (in the outer sector of the FTB) a tectonic stack (Gela thrust system). These successions are characterized by a basal unconformity on the deformed substrate believed to be the depositio…
Zircon ages defining deposition of the Palaeoproterozoic Soutpansberg Group and further evidence for Eoarchaean crust in South Africa
2014
Abstract The precise age of the volcano-sedimentary Soutpansberg Group, which was deposited upon the Palala shear belt separating the Kaapvaal Craton from the Central Zone of the Limpopo Belt, has long been debated. The Soutpansberg Group is subdivided into a lower and upper succession, which are separated from each other by a prominent regional unconformity. Zircon grains from silicic pyroclastic rocks of both successions were investigated in order to constrain the timing of deposition of the Soutpansberg Group rocks. The zircon grains of the investigated samples from both successions yield a wide range of ages, spanning from 1831 to 3937 Ma. Most of the zircon grains have rounded shapes, …
Late-glacial to Holocene aeolian deposition in northeastern Europe - The timing of sedimentation at the Iisaku site (NE Estonia)
2015
Abstract The Late-glacial and Holocene aeolian inland dune complex at Iisaku (NE Estonia) has been investigated using an accurate and detailed compilation of the sedimentary properties and chronological framework. The quartz grains forming the dunes are very variable, reflecting aeolian, weathering, and periglacial conditions, both prior and after deposition. Although the morphological forms and the sedimentary record point to a dune-like environment, the transport record reflects either a short transport time or/and distance, and a contribution from neighbouring sedimentary environments. Dune development in the area was strongly controlled by the formation of the Baltic Ice Lake (BIL) in f…
Inner vs. outer wedge-top depozone “sequences” in the Late Miocene (late Tortonian–early Messinian) Sicilian Foreland Basin System; new data from the…
2012
Abstract The wedge-top depozone belongs to the innermost portion of a Foreland Basin System (FBS) ( DeCelles and Giles, 1996 ) and includes all sediments, typically coarse-grained proximal facies, that bury the active frontal part of a fold and thrust belt. The Terravecchia Formation ( Flores, 1959 , Schmidt Di Friedberg, 1962 , Schmidt Di Friedberg, 1964 , Catalano, 1979 ) is a composite lithostratigraphic unit widespread in Sicily (southern Italy) which has been recently considered ( Gugliotta, 2010 ) as a part of the stratigraphic record of the Late Miocene (late Tortonian to early Messinian) Sicilian wedge-top depozone and represent the main object of this paper. Two end-member wedge-to…
Major-ion bulk deposition around an active volcano (Mt. Etna, Italy)
2005
Bulk atmospheric deposition of major cations (Na, K, Ca, Mg) and anions (Cl, F, SO4) were measured at 15 sites around an active volcano, Mount Etna, from 2001 to 2003. Their composition indicates several natural sources, among which deposition of plume-derived volcanogenic gas compounds is prevalent for F, Cl and S. Plume-derived acidic compounds are also responsible for the prevailing acidic composition of the samples collected on the summit of the volcano (pH in the 2.45–5.57 range). Cation species have complex origin, including deposition of plume volcanogenic ash and aerosols and soil-dust wind re-suspension of either volcanic or carbonate sedimentary rocks. Variation of the deposition …