1,721,126 research outputs found
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No full textIsotope records and biofacies from Albian Cenomanian platform limestones (central Italy): new insights into environmental conditions of the Mediterranean region.
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Deformation and fluid flow during orogeny at the Paleo-Pacific active margin of Gondwana: the Early Palaeozoic Robertson Bay accretionary complex (North Victoria Land, Antarctica)
No full textStructural investigations, integrated with X-ray diffraction, fluid inclusion microthermometry and oxygen-stable isotope analyses are used to reconstruct the deformation history and the palaeo-fluid circulation during formation of the low-grade, turbidite-dominated Early Palaeozoic Robertson Bay accretionary complex of north Victoria Land (Antarctica). Evidence for progressive deformation is elucidated by analysing the textural fabric of chronologically distinct, thrust-related quartz vein generations, incrementally developed during progressive shortening and thickening of the Robertson Bay accretionary complex. Our data attest that orogenic deformation was mainly controlled by
dissolution–precipitation creep, modulated by stress- and strain-rate-dependent fluid pressure cycling, associated with local and regional permeability variations induced by the distribution and evolution of the fracture network during regional thrusting. Fracture-related fluid pathways constituted efficient conduits for episodic fluid flow. The dominant migrating fluid was pre-to-syn-folding and associated with the migration of warm (160–200 °C) nitrogen- and carbonic (CO2 and CH4)-bearing fluids. Both
fluid advection and diffusive mass transfer are recognized as operative mechanisms for fluid–rock interaction and vein formation during continuous shortening. In particular, fluid–rock interaction was the consequence of dissolution–precipitation creep assisted by tectonically driven cooling fluids moving through the rock section as a result of seismic pumping. The most likely source of the migrating fluids would be the frontal part of the growing accretionary complex, where fluids from the deep levels in the hinterland are driven trough channelization operated by the thrust-related fracture (fault) systems
Fluid inclusions constraints on P-T conditions during accretionary complex formation: the case of the Robertson Bay Terrane (north Victoria Land, Antartica).
No full textThis paper describes the fluids circulating in the extensive thrust-related quartz-bearing vein systems developed within the low-grade turbidite-dominated Early Paleozoic Robertson Bay Terrane of north Victoria Land, Antarctica. It provides a well-preserved example of fossil accretionary complex, developed during the Paleozoic subdution-related accretionary process at the paleo-Pacifica margin of Gondwana. Fluid inclusions are analysed in quartz crystals hosted within distinct generations of veins, which are interpreted to record the incremental deformation history during shortening and accretionary complex formation. Our data provides clues to the tectono-thermal history associated with orogenic complex formation, also providing inferences on the fluid storage and recycling through time
Trophic control on the architecture of a Miocene carbonate ramp (central Italy): d13 C fluctuations and biofacies assemblages
No full textEarly to Middle Miocene D13C record in a carbonate platform succession from central Mediterranean:volcanism versus Monterey event
No full textCrop husbandry at Gabii during the Iron Age and Archaic Period. The archaeobotanical and stable isotope evidence
No full textIntensification of agricultural production to support demographic growth has been invoked as a necessary correlate to the important socio-economic changes involved in the urbanisation process of Western Central Italy at the beginning of the 1st millennium BCE. Yet, the agricultural economy of the early urban centres in the region remains poorly understood. Ongoing excavations at Gabii provide a new substantial archaeobotanical dataset that allows the investigation of crop production and farming practices during the transitional period between the eighth and the sixth century BCE. This study presents a multi-proxy approach that integrates archaeobotanical data with carbon and nitrogen stable isotope analyses on charred cereal grains to reconstruct Gabii’s crop husbandry regimes. Our results show an unexpected local combination of staples in which barley is the most common crop. No significant changes are visible throughout the period suggesting a remarkable consistency in crop selection and persistence of traditional practices. The stable nitrogen isotope analysis has revealed low values that we argue could be an indication of intercropping cereals and pulses. A drop in the water availability during the sixth century BCE could be related to a combination of environmental factors, human behaviours, and, possibly, production stress
P-T-deformation history and paleo-fluid conditions during orogenic construction in a low-grade terrane: the early Paleozoic Robertson Bay accretionary complex (North Victoria Land, Antarctica)
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