Search results for " basin"
showing 10 items of 838 documents
Late Archaean foreland basin deposits, Belingwe greenstone belt, Zimbabwe
2001
Abstract The c. 2.65 Ga old sedimentary Cheshire Formation of the Belingwe greenstone belt (BDB), central Zimbabwe, has been studied in detail for the first time to shed some light on the much debated evolution of this classical belt. The Cheshire Formation rests sharply on a mafic volcanic unit (Zeederbergs Formation) and comprises a basal, eastward-sloping carbonate ramp sequence built of shallowing-upward, metre-scale sedimentary cycles. The cycles strongly resemble Proterozoic and Phanerozoic carbonate cycles and might have formed by small-scale eustatic sea level changes. The top of the carbonate ramp is represented by a karst surface. The carbonates are overlain by and grade laterally…
Sedimentation in a fluvially infilling, barrier-bound estuary on a wave-dominated, microtidal coast: the Oueme River estuary, Benin, west Africa
2002
The Oueme River estuary is located on the seasonally humid tropical coast of Benin, west Africa. A striking feature of this microtidal estuary is the presence of a large sand barrier bounding a 120 km2 circular central basin, Lake Nokoue, that is being infilled by heterogeneous fluvial deposits supplied by a relatively large catchment (50 000 km2). Borehole cores from the lower estuary show basal Pleistocene lowstand alluvial sediments overlain by Holocene transgressive–highstand lagoonal mud and by transgressive to probably early highstand tidal inlet and flood-tidal delta sand deposited in association with non-preserved transgressive sand barriers. The change in estuary-mouth sedimentatio…
Nearshore, temperate, carbonate depositional systems (lower Tortonian, Agua Amarga Basin, southern Spain): implications for carbonate sequence strati…
1997
Abstract The bryozoan-rich lower Tortonian carbonates of the Agua Amarga Basin in southern Spain (Province of Almeria) provide an example of sediments formed in a nearshore, non-tropical depositional setting. Based on data derived from logging of sections and from field mapping, these lower Tortonian carbonates form a depositional sequence, which is subdivided into several depositional systems. A lowstand systems tract, which consists of volcaniclastic fan deltas and washover deposits, formed on the leeward side of a basement shoal which delimited the basin towards the south. A transgressive systems tract, which is characterised by a landward encroachment of deposits, is represented by subm…
Helium isotopes and tectonics in southern Italy
1989
Geodynamic evolution of southern Italy can be understood within the framework of the Mediterranean-Alpine System. Subduction of a plate along the Sicily-Calabrian forearc under the Tyrrhenian Sea has been suggested by many geophysicists, although it is not yet confirmed and remains somewhat controversial. Helium isotope ratios provide useful information on the geotectonic structure of the region. The authors report here the {sup 3}H/{sup 4}He ratios of terrestrial gas samples from southern Italy. The observed {sup 3}He/{sup 4}He ratios are relatively high in the Eolian volcanic arc region and low in the other areas. Dichotomous explanations are presented. Firstly, volcanic arc-forearc hypot…
Des particules charbonneuses, t�moins des variations de l'�rosion chimique d'un bassin versant calcaire durant l'holoc�ne (bassin de chaillexon, doub…
1999
Matter fluxes result from chemical and mechanical weathering that vary as a function of climate, relief, lithology and human activities. The aim of this paper is to characterize chemical weathering variations in the past using coaly particles found in both the geological substratum and the Holocene lacustrine sediments of a calcareous basin (Chaillexon lake, Doubs, France). Results point out that chemical weathering was the predominant erosional process in the watershed, which may be due to the calcareous nature of the bedrock. The significant variability of this process relative to mechanical weathering during the Holocene period can be interpreted as a consequence of the development of th…
Cottus gobio Linnaeus, 1758 Community Interest Species Conservation in Upper Târnava Mare River Basin, Through Fish Populations Rehabilitation for Br…
2017
Abstract The ADONIS: CE software has been used for two fish species, Cottus gobio, of conservation interest and Salmo trutta fario, of economic interest, to design an on-site (upper Târnava Mare River) adapted support-system model for management decision-making. Habitat needs and indicators of favourable conservation status have been investigated, pressures and threats to these fish species have been determined, and management elements have been suggested. This management system allows the proper organization of management measures for the renaturation of the local natural fish associations in the local brown trout zone.
Another New Riparian Dendrobatid Frog Species from the Upper Amazon Basin of Peru
2003
A new dendrobatid frog of the genus Colostethus is described from the Cordillera El Sira, an isolated mountain ridge in the upper Amazon basin of central Peru. It has bright yellowish dorsolateral stripes thus resembling Colostethus exasperatus, Colostethus sp. (cf. exasperatus), and Colostethus nexipus, all from the upper Amazon basin of Ecuador and Peru. In morphology, the new species is most similar to Colostethus mcdiarmidi from the eastern Andean slopes of Bolivia and Colostethus alessandroi from the eastern Andean slopes of Peru. The new species can be distinguished from all these taxa on the basis of coloration including the color of the ring around pupil in life, adult male size, le…
New species of the rugose coral genus Lithostrotion Fleming in the upper Viséan from the Azrou-Khenifra Basin (Morocco)
2020
The new species Lithostrotion termieri Rodríguez & Somerville is described. It shows very large corallites of the rugose genus Lithostrotion Fleming. It has been recorded up to now only in upper Viséan rocks from the type locality, the Akrab ridge, Morocco also called Tizi Ben Zizouit by Termier & Termier (1950), who identified it as Lonsdaleia floriformis, and south-east from Tabainout, also from the Azrou-Khenifra Basin.
Rotifer vertical distributions in a meromictic basin of Lake Banyoles (Spain)
1993
The vertical distribution of rotifer populations has been analyzed in a meromictic basin (III) of the karstic Lake Banyoles. This basin had, at the time of the study, an anaerobic monimolimnion from around 17 m in summer or 21 in winter to 25 m, its maximum depth. However, below this layer a warmer micro aerophiliczone with suspended marls is found in a chimney to a depth of 130 m.
Asociaciones de Ostrácodos del Mioceno Temprano—Medio de Loma Negra (Bardenas Reales de Navarra, Cuenca del Ebro): Evolución Paleoambiental de un Med…
2014
LOWER-MIDDLE MIOCENE OSTRACOD ASSEMBLAGES OF LOMA NEGRA (BARDENAS REALES DE NAVARRA, EBRO BASIN): PALAEOENVIRONMENTAL EVOLUTION OF A LACUSTRINE SYSTEM. The palaeoenvironmental evolution of the Loma Negra section (Bardenas Reales de Navarra, Ebro Basin) during the lower-middle Miocene, is studied for the first time. The paleoen- vironmental interpretation is based on the recovered ostracod assemblages and the sedimentology. The lower part of this section is composed by red, yellow and grey mudstones, and with Paralimnocythere sp. as the most abundant ostracod taxon. The lithological features and the fau- nistic assemblage allows the interpretation of a paleoenvironment with the development o…