Search results for "Stratigraphy"

Comment on "Lethally hot temperatures during the Early Triassic greenhouse".

2013

Sun et al . (Reports, 19 October 2012, p. 366) reconstructed Permian to Middle Triassic equatorial seawater temperatures. After correct temporal positioning of their data points, their presumed trends of temperature changes, and hence their assumption of a one-to-one relationship between putative "lethally hot" seawater temperatures and a disputable equatorial "eclipse" of some organisms, are no longer supported by their data.

Formation of secondary carbonates and native sulphur in sulphate-rich Messinian strata, Sicily

2010

Abstract Microbially formed authigenic carbonates accompanied by native sulphur are present in the ‘Calcare Solfifero’ below a thick succession of gypsum deposited during the Messinian salinity crisis in Sicily. We sampled these carbonates and associated sulphur in five former sulphur mines to subject them to a detailed petrographic and geochemical study in order to explore their different modes of formation. Native sulphur formed in conjunction with microbial sulphate reduction, which is reflected in its depletion in 34S (δ34S values as low as − 2‰ vs. V-CDT) and an enrichment of 34S in the residual sulphate (δ34S values as high as + 61‰). The oxidation of organic matter by sulphate reduct…

Near surface seismostratigraphic modelling of the Bandita plain in Palermo town (Italy) from integra-ted analysis of HVSR and stratigraphic data

2016

The Horizontal to Vertical Spectral Ratio (HVSR) noise method (Nakamura, 1989) is nowadays widely used to estimate the resonance frequencies of geological structures (Bonnefoy-Claudet, 2006). However, often HVSR is also used to obtain information on the depth of the seismic bedrock and on thickness and seismic velocity of the process overburden deposits, using inversion techniques of the H/V curve (Fäh et al., 2003). This nevertheless produce results with large uncertainty intervals of parameters, and then must be necessarily constrained by detailed stratigraphic information. An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of…

Science on Stage: From Doctor Faustus to Copenhagen. By Kirsten Shepherd-Barr. Princeton and Oxford: Princeton University Press, 2006. Pp. viii + 271…

2007

Laminated carbonate deposits in Roman aqueducts: Origin, processes and implications

2013

Carbonate deposits in Roman aqueducts of Patara and Aspendos (southern Turkey) were studied to analyse the nature of their regular layering. Optical microscopy and electron-backscattered diffraction results show an alternation of dense, coarsely crystalline, translucent laminae composed of bundles and fans of elongate calcite crystals with their c-axes parallel to the long axis, and porous, fine-grained laminae with crystals at near-random orientation. The ?18O and ?13C data show a strong cyclicity and anti-correlation, whereby high and low ?18O values correspond to dense columnar and porous fine-grained laminae, respectively. Geochemical analyses show similar cyclic changes in carbonate co…

2020

Abstract. Fluid flow on different scales is of interest for several Earth science disciplines like petrophysics, hydrogeology and volcanology. To parameterize fluid flow in large-scale numerical simulations (e.g. groundwater and volcanic systems), flow properties on the microscale need to be considered. For this purpose experimental and numerical investigations of flow through porous media over a wide range of porosities are necessary. In the present study we sinter glass bead media with various porosities and measure the permeability experimentally. The microstructure, namely effective porosity and effective specific surface, is investigated using image processing. We determine flow proper…

Combined numerical and experimental study of microstructure and permeability in porous granular media

2020

<div> <div> <div> <p>Fluid flow on different scales is of interest for several Earth science disciplines like petrophysics, hydrogeology and volcanology. To parameterize fluid flow in large-scale numerical simulations (e.g. groundwater and volcanic systems), flow properties on the microscale need to be considered. For this purpose experimental and numerical investigations of flow through porous media over a wide range of porosities are necessary. In the present study we sinter glass bead media with various porosities, representing shallow depth crustal sediments. The microstructure, namely effective porosity …

Soil physical quality changes under different management systems after 10 years in the Argentine humid pampa

2015

Abstract. South American countries with the highest surface of land under no-tillage (NT) management are Brazil, Argentina and Chile. In Argentina, 78.5% of the agricultural land is cropped under NT management. Several experiments have confirmed the improvements in soil aggregation and infiltration achieved by NT management in dry-land farming areas associated with increases of bulk density (δb) under NT management. An increase in bulk density implies a reduction of the macro and mesoporosity that is in contradiction with the increased infiltration that occurs at macro and mesopores. We hypothesize that the increase of bulk density in NT management mainly affects the mesopores. We evaluated…

Late Pleistocene and Holocene landscape history of the central Palatinate forest (Pfälzerwald, south-western Germany)

2010

Abstract Field studies on the Late Pleistocene and Holocene landscape history were conducted in the central Palatinate Forest ( Pfalzerwald , Rhineland-Palatinate, Germany) near the village of Johanniskreuz. The structure and composition of periglacial cover beds, the young floodplain sediments of the Aschbach, Schwarzbach und Moosalbe valleys, and the sediment structure in some dry valleys, of alluvial fans and slope colluvia, were studied. The sandy cover beds are less than 10% aeolian, and in all cases only the main and basal layer are present, with no evidence of the intermediate layer. In general, the cover beds resemble those of other parts of the Central German Uplands ( Mittelgebirg…

Les Hypogées d'Arles-Fontvieille et leur environnement : nouvelles perceptions, nouvelles perspectives

2014

Due to their unique architecture and the exceptional dimensions of the largest monument in the group, the Arles-Fontvieille hypogea are among the most remarkable megalithic monuments in Europe and the western Mediterranean region. A collective research program was launched in 2013 to study these well-known monuments which have, paradoxically, been the subject of relatively few field studies since the 19th century. The research program consisted of an inventory and analysis of the grave goods and associated artefacts, as well as a number of field studies providing an improved archaeological context of a megalithic group too often thought of only in terms of funerary monuments. Various traces…