Search results for "Sedimentary"
showing 10 items of 455 documents
Microbial and meiofaunal response to intensive mussel-farm biodeposition in coastal sediments of the Western Mediterranean
2000
We studied the impact of organic loads due to the biodeposition of a mussel farm in a coastal area of the Tyrrhenian Sea (Western Mediterranean). Sediment chemistry, microbial and meiofaunal assemblages were investigated from March 1997 to February 1998 on monthly basis at two stations: the first was located under the mussel farm, while the second was at about 1-km distance and served as control. Benthic response to changes in the biodepositional regime was investigated in terms of biochemical composition of the sedimentary organic matter, phytopigment content, bacterial abundance and composition and meiofaunal community structure. A large accumulation of chloroplastic pigments, proteins an…
Calcareous nannofossil surface sediment assemblages from the SicilyChannel (central Mediterranean Sea): palaeoceanographic implications.
2008
Quantitative analysis of 67 calcareous nannofossil assemblages from surface sediments recovered in a wide area across the Sicily Channel has been carried out in order to improve the interpretation of palaeontological data based on this planktonic group in a key area for Mediterranean palaeoceanographic studies. The investigation focused on three case studies that demonstrate the high potentiality of such a combined approach, taking into account the recent distribution of taxa or groups of taxa on the sea floor and the palaeontological record. The distribution of reworked specimens over the northern Sicily Channel sea floor validates the role of southern Sicily as a source region for reworke…
The end of the Messinian Salinity Crisis in the western Mediterranean: insights from the carbonate platforms of south-eastern Spain.
2010
International audience; How the Messinian Salinity Crisis (MSC) ended is still a matter of intense debate. The Terminal Carbonate Complex (TCC) is a late Messinian carbonate platform system that recorded western Mediterranean hydrological changes from the final stages of evaporite deposition till the advent of Lago-Mare fresh- to brackish water conditions at the very end of Messinian times. A multidisciplinary study has been carried out in three localities in south-eastern Spain to reconstruct the history of TCC platforms and elucidate their significance in the MSC. Overall, this study provides evidence that the TCC formed following a regional 4th order water level rise and fall concomitant…
A high-resolution record of the last deglaciation in the Sicily Channel based on foraminifera and calcareous nannofossil quantitative distribution
2003
Abstract Relative abundance fluctuations in planktic foraminiferal and calcareous nannofossil assemblages are reported on the basis of a high-resolution study of ODP Leg 160 Hole 963D, drilled in the Sicily Strait, near Capo Rossello (southern Sicily). With its 8 m of undisturbed sediments, the core covers the interval from 1.5 to 23 kyr, allowing a 50–100-yr sampling resolution. All the short warm and cold events and sub-events recorded in this time interval in the GRIP Greenland ice core and at several Mediterranean sites were recognized. On this basis, a total number of nine ecozones based on planktic foraminifera and seven ecozones based on calcareous nannofossils were identified. A sho…
Environmental Constraints on Pathways of Organic Detritus in a Semi-enclosed Marine System (W-Mediterranean)
2001
In order to assess seasonal and spatial changes in water-sediment interaction processes in a semi-enclosed marine system of Western Sicily (Marsala lagoon; W-Mediterranean), the biochemical composition of suspended and sediment organic matter was studied, during a one-year sampling period. The observed dynamic balance of resuspension vs. sedimentation processes and the macroalgal and vascular plant coverage appear major factors in affecting both amounts and biochemical composition of suspended and sedimentary organic matter and allowed us to identify two different sub-systems. The northern area, characterised by frequent wind-induced sediment resuspension events and by a scant vegetation, d…
Late Messinian to Early Pliocene paleoenvironmental changes in the Melilla Basin (NE Morocco) and their relation to Mediterranean evolution
2003
Abstract Three major paleoenvironmental changes have been recognized during the late Miocene to Early Pliocene in the Melilla Basin (Northeastern Morocco) and compared with the regional events that affected the Mediterranean hydrology during this crucial period. The first change was the definitive conversion of the restricted marine conditions that prevailed since the end of the reef carbonate complex into lacustrine environments; this occurred around 5.8 Ma which is earlier than in the rest of the Mediterranean where the Lower Evaporites were still forming. These lacustrine settings display great similarities with the Lago-Mare environments that started in the Mediterranean during the depo…
Multidisciplinary integrated field campaign to an acidic Martian Earth analogue with astrobiological interest: Rio Tinto
2011
Recently reported results from latest Mars Orbiters and Rovers missions are transforming our opinion about the red planet. That dry and inhospitable planet reported in the past is becoming a wetter planet with high probabilities of water existence in the past. Nowadays, some results seem to indicate the presence of water beneath the Mars surface. But also mineralogy studies by NASA Opportunity Rover report iron oxides and hydroxides precipitates on Endurance Crater. Sedimentary deposits have been identified at Meridiani Planum. These deposits must have generated in a dune aqueous acidic and oxidizing environment. Similarities appear when we study Rio Tinto, and acidic river under the control…
Overview of the Opportunity Mars Exploration Rover Mission to Meridiani Planum: Eagle Crater to Purgatory Ripple
2006
The Mars Exploration Rover Opportunity touched down at Meridiani Planum in January 2004 and since then has been conducting observations with the Athena science payload. The rover has traversed more than 5 km, carrying out the first outcrop-scale investigation of sedimentary rocks on Mars. The rocks of Meridiani Planum are sandstones formed by eolian and aqueous reworking of sand grains that are composed of mixed fine-grained siliciclastics and sulfates. The siliciclastic fraction was produced by chemical alteration of a precursor basalt. The sulfates are dominantly Mg-sulfates and also include Ca-sulfates and jarosite. The stratigraphic section observed to date is dominated by eolian bedfor…
In situ evidence for an ancient aqueous environment at Meridiani Planum, Mars.
2004
Sedimentary rocks at Eagle crater in Meridiani Planum are composed of fine-grained siliciclastic materials derived from weathering of basaltic rocks, sulfate minerals (including magnesium sulfate and jarosite) that constitute several tens of percent of the rock by weight, and hematite. Cross-stratification observed in rock outcrops indicates eolian and aqueous transport. Diagenetic features include hematite-rich concretions and crystal-mold vugs. We interpret the rocks to be a mixture of chemical and siliciclastic sediments with a complex diagenetic history. The environmental conditions that they record include episodic inundation by shallow surface water, evaporation, and desiccation. The …
Two Years at Meridiani Planum: Results from the Opportunity Rover
2006
The Mars Exploration Rover Opportunity has spent more than 2 years exploring Meridiani Planum, traveling ∼8 kilometers and detecting features that reveal ancient environmental conditions. These include well-developed festoon (trough) cross-lamination formed in flowing liquid water, strata with smaller and more abundant hematite-rich concretions than those seen previously, possible relict “hopper crystals” that might reflect the formation of halite, thick weathering rinds on rock surfaces, resistant fracture fills, and networks of polygonal fractures likely caused by dehydration of sulfate salts. Chemical variations with depth show that the siliciclastic fraction of outcrop rock has undergon…