Search results for "Processes"

Experiments for testing soil texture effects on flow resistance in mobile bed rills

2018

Abstract In this paper a recently theoretically deduced rill flow resistance equation, based on a power-velocity profile, was tested experimentally on plots of varying slopes and soil texture in which mobile bed rills are incised. Measurements of flow velocity, water depth, cross section area, wetted perimeter and bed slope conducted in rill reaches incised on experimental plots, having different slope values (9, 14, 22, 24 and 26%) and soil texture (clay fraction ranging from 42 to 73%), and literature data were used to calibrate the flow resistance equation. In particular, the relationship between the velocity profile parameter Γ, the channel slope, the flow Froude number and texture frac…

A continuous high-resolution dust record for the reconstruction of wind systems in central Europe (Eifel, Western Germany) over the past 133 ka

2009

[1] The last glacial cycle in Central Europe is dominated by processes of aeolian dust transport and accumulation. These dust deposits are preserved in soils and lake sediments and provide detailed information about the climate variability during cold and dry periods. Especially the transitions from warm into cold periods are characterized by turbulent climate conditions. The main problems of terrestrial paleoclimate reconstructions are the completeness of the core material and a sampling resolution. To detect single dust storms we use a particle detection method, which allows high resolution, sub-annual analyses of sediment structures in undisturbed samples. The ELSA (Eifel Laminated Sedim…

Effect of the conversion of grassland to spring wheat field on the CO2 emission characteristics in Inner Mongolia, China

2007

Chinese grasslands have undergone great changes in land use in recent decades. Approximately 18.2% of the present arable land in China originated from the cultivation of grassland, but its impact on the carbon cycle has not been fully understood. This study wasconducted insitu for3yearstoassessthecomprehensive effects ofcultivationof temperatesteppe onsoilorganiccarbon(SOC) and soil respiration rates as well as ecosystem respiration. As compared with those in the Stipa baicalensis steppe, the SOC concentrations at depths of 0‐10 and 10‐20 cm in the spring wheat field were found to have decreased by 38.3 and 17.4% respectively from 29.5 and 21.9 g kg � 1 to 18.2 and 18.1 g kg � 1 after a cul…

2020

Abstract. New Zealand's Alpine Fault is a large, plate-bounding strike-slip fault, which ruptures in large (Mw>8) earthquakes. We conducted field and laboratory analyses of fault rocks to assess its fault zone architecture. Results reveal that the Alpine Fault Zone has a complex geometry, comprising an anastomosing network of multiple slip planes that have accommodated different amounts of displacement. This contrasts with the previous perception of the Alpine Fault Zone, which assumes a single principal slip zone accommodated all displacement. This interpretation is supported by results of drilling projects and geophysical investigations. Furthermore, observations presented here show th…

Numerical modelling of PT-paths related to rapid exhumation of high-pressure rocks from the crustal root in the Variscan Erzgebirge Dome (Saxony/Germ…

2002

Abstract The Bohemian Massif in the Central European Variscides contains many crustal slices with (ultra-)high-pressure rocks related to continent-continent collision. After closure of pre-existing oceans during the Devonian, excess crustal thickness was maintained for about 50 Ma until at around 340 Ma large volumes of high-pressure rocks from the crustal root were exhumed within a few million years. We relate this event to delamination and complete detachment of the lithospheric mantle, causing a crustal-scale isostatic instability. In the Erzgebirge dome, a model region in the northern part of the massif, an array of interrelated PTtd-paths with “decompression/cooling” and “decompression…

Active north-vergent thrusting in the northern Sicily continental margin in the frame of the quaternary evolution of the Sicilian collisional system

2021

Abstract A three-stage evolution has characterized the Sicilian Fold and Thrust Belt (SFTB) during the last 15 My: two main thin-skinned shortening events involving mainly Meso-Cenozoic carbonate units, followed by thick-skinned thrusting involving Plio-Pleistocene deposits in the frontal area as well as the crystalline basement in the inner and deeper sector of the chain. We investigated the northern Sicily continental margin, by using differently-penetrative seismic reflection data and new field surveys, which revealed, both offshore and onshore, north-vergent compressional structures that affected the tectonic edifice during Quaternary time. These structures, correlated with the kinemati…

Towards the identification of a new taphonomic agent: An analysis of bone accumulations obtained from modern Egyptian vulture (Neophron percnopterus)…

2014

This paper presents the results of a study of bones recovered in various current Egyptian vulture (Neophron percnopterus) nests in a Mediterranean region of the Iberian Peninsula. The Egyptian vulture, a diurnal, scavenging, rupicolous bird of prey, is one of four vulture species that currently inhabit the Iberian Peninsula. An analysis of the remains found in the nests confirms that it has a heterogeneous diet that includes remains from human activities (butchery and food production) and the carcasses of dead animals, although it is possible that they also prey on small-sized taxa. The taphonomic study determines these birds' capability of transporting, accumulating and altering bone remai…

Sedimentological and geoarchaeological evidence of multiple tsunamigenic imprint on the Bay of Palairos-Pogonia (Akarnania, NW Greece)

2010

Abstract This paper presents evidence of multiple tsunami impact on the Bay of Palairos-Pogonia, NW Greece, during the Holocene based on detailed geo-scientific studies. Altogether, 41 vibracores were drilled to detect high-energy influence in the stratigraphical record. Layers of coarse-grained allochthonous marine deposits were found intersecting autochthonous fine-grained back beach sediments in the Palairos coastal plain, on top of beach or marly bedrock units at Pogonia beach and along the Pogonia cliff section. High-energy deposits are associated with specific sedimentary structures such as fining upward sequences, rip up-clasts, basal erosional contact, bi- to multimodal grain size d…

Geochemistry of phosphatic nodules as a tool for understanding depositional and taphonomical settings in a paleolithic cave site (San teodoro, Sicily)

2021

Interpreting depositional settings of cave sites is generally problematic, especially in absence of palaeontological/archaeological evidence. This is the case of some deposits at San Teodoro Cave (Sicily), a key site for the Mediterranean Palaeolithic. In a stratigraphic level interrupted by a carbonatic concretion, phosphatic nodules are present only in the part enclosed between the concretion and the cave wall. The discovery of these nodules combined with the punctual lack of fossils had initially suggested an erosion phenomenon and subsequent formation of nodules at a vadose level. Here we show the usefulness of an integrated, geochemical-palaeoecological approach in defining stratigraph…

Geochemistry, geochronology and isotope geology of Nakfa intrusive rocks, northern Eritrea: products of a tectonically thickened Neoproterozoic arc c…

2001

Abstract The north-south-trending Neoproterozoic volcano-sedimentary plutonic associations in northern Eritrea are part of the Nubian Shield. The Nakfa intrusive rocks range in composition from gabbro to syeno-diorite to granite and alkaline syenite and intrude supracrustal rocks of volcanic and sedimentary origin. All granitoid rocks are metaluminous or slightly peraluminous and have typical I-type chemical signatures. The calc-alkaline intrusive rocks and the alkaline syenites have geochemical characteristics (e.g. low Nb values) typical of arc intrusives and plot as volcanic arc granites on various discriminant diagrams. Single zircon evaporation Pb-Pb ages and conventional multigrain U-…