Search results for "Sedimentary"
showing 10 items of 455 documents
Cyanophyte calcification morphotypes and depositional environments (Alenquer oncolite, upper Kimmeridgian?, Portugal)
1985
Terrigenous red siliciclastics of Upper Kimmeridgian(?) to Portlandian age around Alenguer, Portugal, comprise a narrow level of oncoid-bearing limestones. Oncoid cortices are composed of cyanophytes which appear in different calcification morphotypes according to changing physico-chemical parameters. Recent examples reveal that in most cases each calcification morphotype is related to one single species or one defined association. Hence, the characteristic calcification patterns are mostly biologically rather than abiogenetically controlled. Oncoid shapes, sizes and arrangement, on the other hand, are mainly determined by the hydraulic parameter within the depositional environment.
Review of “Marine Hard Substrates: Colonization and Evolution,” a Thematic Session at the Geological Society of America Annual Meeting, Denver, USA, …
2005
A theme session, jointly sponsored by the Paleontological Society and the Geological Society of America Sedimentary Geology division, and entitled “Marine Hard Substrates: Colonization and Evolutio...
Beaches in Valencian Coast
2018
The main factors that determined the Valencian beaches characteristics are the configuration of relief structures; fluvial sediment supply; low tidal range; the predominance of low energy waves; scarcity of big storms; longshore littoral drift; and human action. There is a significant prevalence of sandy beaches. Nevertheless, both at the northern part of the Gulf of Valencia and in the structural segment, between the Cape Sant Antoni and Alicante city, pebble and gravel beaches are predominant. Most of the Valencian beaches have experienced significant morphological changes during the last decades due to the human interventions -voluntary or involuntary- in the coastal system. The implemen…
Impact of sedimentology and diagenesis on the petrophysical properties of a tight oolitic carbonate reservoir. The case of the Oolithe Blanche Format…
2013
18 pages; International audience; The Oolithe Blanche Formation was studied in three quarries, located at the south-eastern edge of the Paris Basin (France). Heterogeneities in reservoir properties were assessed through a sedimentological, diagenetic and petrophysical study. The relationships between depositional settings, diagenesis and petrophysical properties were analysed using detailed petrographic studies, image analysis, Nano CTscans and petrophysical measurements. The carbonate reservoir pore network is mainly controlled by intraparticle microporosity which ensures the connectivity with interparticle meso- and macroporosity. Early cementation vs. early compaction processes (mainly g…
Soil and organic carbon redistribution in a recently burned Mediterranean hillslope affected by water erosion processes
2022
Forest fires cause many changes in the physical, chemical and biological soil properties such as aggregation and soil organic carbon contents (SOC) as well as on soil hydrology and erosion processes. Most studies on post-fire soil erosion in Mediterranean environments have been plot-based and research at hillslope or broader scale is scarce. Understanding SOC nature, distribution and modifications, as produced by forest fires and erosion, has become crucial to model and define the role of soil erosion as source or sink of C, and to sustainably manage ecosystem services related to the soil resource. This research provides data about the loss and redistribution of soil and SOC in a Mediterran…
Nitrogen isotope evidence for stepwise oxygenation of the ocean during the Great Oxidation Event
2019
24 pages; International audience; The Earth’s oxygenation represents one of the most important environmental drivers of life’s evolution, with the first rise, known as ‘the Great Oxidation Event’ (GOE), corresponding to unpreceded accumulation of atmospheric O2, changes in the flux of marine nutrients and possibly global glaciations. However, the detailed evolution of the GOE is still debated, as for instance the accumulation trends of oceanic versus atmospheric oxygen and the nature of biogeochemical responses to oxygenation. Here, we combine organic carbon and bulk nitrogen isotope compositions with major element concentrations and iron speciation data of sedimentary rocks recovered from …
The Use of Carbon Stable Isotopes to Investigate the Origin and Distribution of Suspended and Sedimentary Organic Matter in a Semi-enclosed Mediterra…
2001
The natural stable isotope values of different primary sources have been used to trace the fate of organic carbon that enters in the marine food webs of Stagnone di Marsala (Italy). Water and sediment samples were collected monthly (March 1996 – February 1997) at 3 stations, characterized by different amounts of vegetal cover and analysed to determine total organic matter (OM), phytopigments, biopolymeric organic carbon (BPC) and stable carbon isotopic composition (δ13C), the latter measured also in main primary producers. Sedimentary OM accumulated in summer, while total suspended organic matter reached highest concentrations in May and December. The concentration of chlorophyll-a carbon i…
Sources of carbon and dietary habits of new Lessepsian entry Brachidontes pharaonis (Bivalvia, Mytilidae) in the western Mediterranean
2003
The sources of carbon and the dietary habits of Brachidontes pharaonis (Mollusca, Bivalvia), a new Lessepsian entry in the western Mediterranean, living in a cooling vat of a saltworks system in western Sicily (MED), were assessed by estimating throughout a season the relative abundance of a stable carbon isotope (δ13C) in particulate organic matter (POM), sedimentary organic matter (SOM), primary organic matter sources (seagrasses, sand microflora, macroalgae), Brachidontes pharaonis and its biodeposition material. In the saltworks the most enriched primary food source potentially fuelling the saltworks food web was Cymodocea nodosa (seasonal average -7.9±0.6‰), Laurencia papillosa and Cys…
DEEP RESERVOIR TEMPERATURES OF LOW-ENTHALPY GEOTHERMAL SYSTEMS IN TUNISIA: NEW CONSTRAINTS FROM CHEMISTRY OF THERMAL WATERS
2012
Tunisia is characterized by hot and warm groundwaters (temperature up to 75 °C) which represent the surface manifestation of geothermal systems hosted in carbonate-evaporite rock sequences. The T-conditions of Tunisia deep thermal reservoirs are here evaluated for the first time at the regional scale. The results here shown clearly highlight the limitations inherent in the application of common geothermometric methods in the estimation of equilibrium temperatures in sedimentary environments. The modeling approach proposed by Chiodini et alii (1995), which makes use of the ratios between dissolved HCO3, SO4 and F, provides the most reliable results, and allows us to derive equilibrium temper…
Dynamics of sediments along with their core properties in the Monastir-Bekalta coastline (Tunisia, Central Mediterranean)
2017
International audience; The authors report on two campaigns of high-resolution samplings along the shores of Monastir Bay in Tunisia: the first being a study of sediment dynamics, grain size and mineral composition in surface sediment, and the second, eight months later, using four sediment cores to study grain-size distribution in bottom sediments. Particle size analysis of superficial sediment shows that the sand in shallow depths is characterized by S-shaped curves, indicating a certain degree of agitation, possible transport by rip currents near the bottom and hyperbolic curves illustrating heterogeneity of sand stock. The sediments settle in a relatively calm environment. Along the bay…