Search results for "ROCK"

Omphacite textures in eclogites of the Tauern Window: Implications for the exhumation of the Eclogite Zone, Eastern Alps

2008

Abstract We discuss the relationship of omphacite lattice preferred orientation (LPO) patterns in eclogite and kinematic indicators in the matrix surrounding the eclogite during the very rapid exhumation of the deeply buried Eclogite Zone in the Tauern Window of the Eastern Alps. LPO patterns are presented from profiles parallel to the eclogite stretching lineation across the Eclogite Zone. The omphacite textures show symmetric patterns across the entire Eclogite Zone; only in few cases slight asymmetries are observed. The patterns are characterized by an alignment of {110} with the foliation and a maximum of 〈001〉 close to the lineation and are indicative of deformation by intracrystalline…

2001

The roles of volume loss, coaxial versus noncoaxial flow, and blueschist exhumation in subduction-related accretionary wedges are still poorly understood. In our study at Leech Lake Mountain in the Eastern belt of the Franciscan subduction complex, we focus on these subjects. In the specific example of the Franciscan, the tectonic significance of the boundary between the Eastern and Central belts remains controversial. The Leech Lake Mountain area in northern California is situated immediately above this boundary and, therefore, appears to be of crucial importance for understanding aspects of the tectonic evolution of the Franciscan. The structural development at Leech Lake Mountain is char…

Origin of potassic postcollisional volcanic rocks in young, shallow, blueschist-rich lithosphere

2020

Unusually high Th/La in K-rich orogenic rocks may indicate shallow blueschist-rich sources in accretionary settings.

GEOLOGIA DE LAS MARGENES DE LA PLACA DEL CARIBE: GENERALIDADES EN GUATEMALA, COSTA RICA, LA ESPAÑOLA Y RESULTADOS PRELIMINARES DEL ANALISIS DE UNA TR…

2011

The Caribbean Plate margins are constituted by deformed belts built up since the Cretaceous in acompressional and strike-slip stress field, which allowed overthrusting of the Caribbean crust onto the Pacific,North and South American Plates.The Caribbean borders include Jurassic-Cretaceous ophiolitic units (Great Antilles, Venezuela, Costa Rica,Guatemala, etc.), composed by mantle peridotites, gabbros, volcanic and sedimentary covers, which have beendeformed in at least two ductile penetrative phases and were often metamorphosed in the prehnite-pumpelleyite,green and blue schist, amphibolite, and in places eclogite facies. These units may present part of a subductioncomplex or are an accreti…

Structural analysis of a complex nappe sequence and late-orogenic basins from the Aegean Island of Samos, Greece

1999

The island of Samos in the Aegean Sea exposes high-pressure metamorphic rocks of the Cycladic blueschist unit which are sandwiched between the mildly blueschist-facies Kerketas nappe below and the overlying non-metamorphic Kallithea nappe. Structural and metamorphic analysis shows that deformation can generally be divided into four main stages: (1) Eocene and earliest Oligocene 0ESE‐WNW-oriented nappe stacking (D1 and D2) associated with blueschist- and transitional blueschist‐ greenschist-facies metamorphism (M1 and M2). D2 caused emplacement of the blueschist unit onto the Kerketas nappe indicating that thrusting occurred during decompression. (2) A subsequent history of Oligocene and Mio…

Compte rendu de : Véronique Bergen, Patti Smith. Horses, Rouen, Éditions Densité, 2018, 93 p.

2019

International audience

Noise reduction in magnetic resonance images by Wavelet transforms: an application to the study of capillary water absorption in sedimentary rocks

2007

Magnetic resonance imaging (MRI) is a powerful technique to study capillary water absorption kinetics in sedimentary rocks. However, the noise in the images can limit the correct identification and the quantitative measurement of the average height reached by the wetting front inside the porous material where imbibition occurs. Therefore, denoising methods can be applied to improve the image quality for a more accurate analysis, without the disadvantages of longer acquisition times. This study attempts to improve the signal-to-noise ratio of the images acquired by MRI on a sedimentary rock (Pietra di Lecce) using a waveletbased thresholding technique. The idea is to average some slightly di…

Biogenic habitat shifts under long-term ocean acidification show nonlinear community responses and unbalanced functions of associated invertebrates

2019

Este artículo contiene 8 páginas, 4 figuras.

Microbial-mediated pre-salt carbonate deposition during the Messinian salinity crisis (Calcare di Base fm., Southern Italy)

2017

Abstract A multi-scale analysis of sedimentary carbonate facies and post-sedimentary diagenetic features of the Calcare di Base Formation, the precursor to evaporites in Upper Messinian successions of Northern Calabria and Central Sicily, has revealed their microbial bio-mediated origin. Massive to laminated microbial boundstones represent the most common sedimentary facies forming flat to low relief cm to m scale stromatolitic and thrombolitic bodies. The fabric of the micrite varies from peloidal to aphanitic, and almost always preserves filamentous bacteria which characterized the original microbial mat. The mat was dominated by sulphur-oxidizing bacteria belonging to the Thiotrichaceae,…

Sedimentology and isotope geochemistry of Carnian deep-water marl/limestone deposits from the Sicani Mountains, Sicily: Environmental implications an…

1995

Abstract The upper Triassic Halobia-bearing marl/limestone deposits from the Sicani Mountains (Sicily) record the sedimentary evolution of the Sicanian Basin through the middle and late Carnian time. Dark marls and interbedded grey calcilutites of Julian age are characterized by abundant pyrite, sparse bioturbation and negative carbonate carbon δ13C values. They accumulated in a basin with dominantly anoxic to dysaerobic bottom waters. Lower Tuvalian dark-grey pyritic marls and calcilutites, which contain carbonate minerals with relatively high Mn contents and widely fluctuating δ13C signatures, were deposited under dysaerobic conditions. Middle and upper Tuvalian cherty limestones show int…