The Roussillon sedimentary Basin (South France) is a complex multi-layered aquifer, close to the ... more The Roussillon sedimentary Basin (South France) is a complex multi-layered aquifer, close to the Mediterranean Sea facing seasonally increases of water abstraction and salinization issues. We report geochemical and isotopic vertical variability in this aquifer using groundwater sampled with a Westbay System® at two coastal monitoring sites: Barcarès and Canet. The Westbay sampling allows pointing out and explaining the variation of water quality along vertical profiles, both in productive layers and in the less permeable ones where most of the chemical processes are susceptible to take place. The aquifer layers are not equally impacted by salinization, with electrical conductivity ranging from 460 to 43,000μS·cm(-1). The δ(2)H-δ(18)O signatures show mixing between seawater and freshwater components with long water residence time as evidenced by the lack of contribution from modern water using (3)H, (14)C and CFCs/SF6. S(SO4) isotopes also evidence seawater contribution but some signatures can be related to oxidation of pyrite and/or organically bounded S. In the upper layers (87)Sr/(86)Sr ratios are close to that of seawater and then increase with depth, reflecting water-rock interaction with argillaceous formations while punctual low values reflect interaction with carbonate. Boron isotopes highlight secondary processes such as adsorption/desorption onto clays in addition to mixings. At the Barcarès site (120m deep), the high salinity in some layers appear to be related neither to present day seawater intrusion, nor to Salses-Leucate lagoonwater intrusion. Groundwater chemical composition thus highlights binary mixing between fresh groundwater and inherited salty water together with cation exchange processes, water-rock interactions and, locally, sedimentary organic matter mineralisation probably enhanced by pyrite oxidation. Finally, combining the results of this study and those of Caballero and Ladouche (2015), we discuss the possible future evolution of this aquifer system under global change, as well as the potential management strategies needed to preserve quantitatively and qualitatively this water resource.
ABSTRACT Keywords: Balearic Promontory bedded unit betic corridor evaporites Messinian Salinity C... more ABSTRACT Keywords: Balearic Promontory bedded unit betic corridor evaporites Messinian Salinity Crisis Primary Lower Gypsum The Messinian Salinity Crisis (MSC) was a major ecological crisis affecting shallow and deep-water settings over the entire Mediterranean basin. However, the evolution of the MSC and its ecological impacts have mainly been explained on the basis of sediments from onshore outcrops. Lack of complete and physically connected records from onshore and offshore settings has inhibited comprehensive understanding of basin behaviour during the MSC. Herein we present a continuous record from an intermediate-depth basin on the Balearic Promontory that comprises late Tortonian–Messinian marls and evaporitic beds from the first MSC phase (i.e., Primary Lower Gypsum-PLG stage). Well-log and biostratigraphic data allow us establishing a large-scale calibration to the astronomical solutions, and to correlate pre-MSC sediments with classical rhythmic successions outcropping onshore. Thickness and characteristic sedimentary patterns observed in the offshore evaporitic records resemble those from marginal PLG sequences. Furthermore, seismic reflectors from a Bedded Unit (BU), which corresponds to an evaporitic interval according to well-to-seismic ties, are correlated with the onshore PLG sequences. This correlation constitutes the first attempt to link well-known marginal sequences with intermediate-depth offshore settings, which have previously only been studied through seismic imaging. Our time-calibration provides direct evidence supporting a synchronous onset of the PLG phase between onshore and offshore settings along the southwestern Balearic Promontory margin. Those BU reflectors, which were positively correlated to the PLG, were likely precipitated offshore the continental shelf at Messinian times. These results suggest that gypsum precipitation and/or preservation was not always limited to 200 m water-depths and could occur in non-silled basins. Finally, we only found a major erosion at the top of the PLG sequences, implying that the MSC drawdown occurred after the precipitation of the onshore lower evaporites. Studied sequences provide new insights into the PLG precipitation/preservation settings, as well as into the land-sea correlations of MSC units, and thus could potentially help refine current MSC models.
International Journal of Greenhouse Gas Control, 2014
ABSTRACT The objective of the CO2FieldLab project was to demonstrate that adequate monitoring met... more ABSTRACT The objective of the CO2FieldLab project was to demonstrate that adequate monitoring methods can be deployed to document potential leaks of CO2 from subsurface reservoirs. For this, a shallow injection experiment through permeable sediment was designed and conducted at Svelvik (Norway) in September 2011. The goal was to produce a CO2 leak in order to assess the relative sensitivity of several geochemical and geophysical CO2 monitoring tools. A total mass of 1.67 tons of CO2 was injected at a depth of 20 m through a 45° inclined well over a 6 day period. Time-lapse induction logging and downhole resistivity monitoring from a permanent dipole–dipole array observatory prove to be very sensitive to the presence of CO2 in the shallow subsurface after the start of injection. Electrical resistivity response correlates with progressive CO2 dissolution in groundwater, with resistivity and pH values decreasing due to the increase of bicarbonate and dissolved species. The CO2 plume is channelled by enhanced permeability layers, with updip migration of the gas plume to the North. Other processes responsible for resistivity changes were fresh/salt water mixing, tidal effects and rainfall.
ABSTRACT The Messinian Salinity Crisis is a huge outstanding succession of events that has deeply... more ABSTRACT The Messinian Salinity Crisis is a huge outstanding succession of events that has deeply modified the Mediterranean area within a short time span at the geological scale. The seismic atlas of the Messinian markers in the Mediterranean and Black seas is a collective work summarizing, in one publication with a common format, the most relevant seismic features related to this exceptionnal event. Seismic information has been collected over many years from the offshore domain. Throughout 13 study areas, the seismic facies, geometry and extent of the Messinian markers (surfaces and depositional units) are described. The absolute time succession of the Messinian events, or the processes responsible for their occurrence in space and time are not discussed. The objectives of this atlas are: (1) to image the Messinian seismic markers from the main margins and basins; (2) to propose a new global and consistent terminology for these markers in the entire offshore Mediterranean area and (3) to make this information accessible to the non-geophysicist community. Interpreted seismic data were carefully selected according to their quality, position and significance in order to reach these objectives, and are presented here. Raw and interpreted seismic profiles are available on CD-Rom. The atlas costs 20 euros and can be ordered online here: http://ccgm.org/en/home/148-seismic-atlas-of-the-messinian-salinity-crisis-markers-2853630978.html or http://www.geosoc.fr/publication/memoires/memoires-nouvelle-serie.html
The principal driving force of slope movements is generally considered to be gravity, with the ma... more The principal driving force of slope movements is generally considered to be gravity, with the main triggering factor being the increase of pore pressures by the presence of water contained in the geological environment. It is however difficult to anticipate the ...
... About 5.6 Ma ago (Clauzon et al., 1996 and Krijgsman et al., 1999a), the salinity crisis led ... more ... About 5.6 Ma ago (Clauzon et al., 1996 and Krijgsman et al., 1999a), the salinity crisis led to a dramatic sea-level fall in the Mediterranean basin (Ryan, 1976, Clauzon, 1982, Lofi, 2002 and Steckler et al., 2003). Clauzon et al. ...
The Roussillon sedimentary Basin (South France) is a complex multi-layered aquifer, close to the ... more The Roussillon sedimentary Basin (South France) is a complex multi-layered aquifer, close to the Mediterranean Sea facing seasonally increases of water abstraction and salinization issues. We report geochemical and isotopic vertical variability in this aquifer using groundwater sampled with a Westbay System® at two coastal monitoring sites: Barcarès and Canet. The Westbay sampling allows pointing out and explaining the variation of water quality along vertical profiles, both in productive layers and in the less permeable ones where most of the chemical processes are susceptible to take place. The aquifer layers are not equally impacted by salinization, with electrical conductivity ranging from 460 to 43,000μS·cm(-1). The δ(2)H-δ(18)O signatures show mixing between seawater and freshwater components with long water residence time as evidenced by the lack of contribution from modern water using (3)H, (14)C and CFCs/SF6. S(SO4) isotopes also evidence seawater contribution but some signatures can be related to oxidation of pyrite and/or organically bounded S. In the upper layers (87)Sr/(86)Sr ratios are close to that of seawater and then increase with depth, reflecting water-rock interaction with argillaceous formations while punctual low values reflect interaction with carbonate. Boron isotopes highlight secondary processes such as adsorption/desorption onto clays in addition to mixings. At the Barcarès site (120m deep), the high salinity in some layers appear to be related neither to present day seawater intrusion, nor to Salses-Leucate lagoonwater intrusion. Groundwater chemical composition thus highlights binary mixing between fresh groundwater and inherited salty water together with cation exchange processes, water-rock interactions and, locally, sedimentary organic matter mineralisation probably enhanced by pyrite oxidation. Finally, combining the results of this study and those of Caballero and Ladouche (2015), we discuss the possible future evolution of this aquifer system under global change, as well as the potential management strategies needed to preserve quantitatively and qualitatively this water resource.
ABSTRACT Keywords: Balearic Promontory bedded unit betic corridor evaporites Messinian Salinity C... more ABSTRACT Keywords: Balearic Promontory bedded unit betic corridor evaporites Messinian Salinity Crisis Primary Lower Gypsum The Messinian Salinity Crisis (MSC) was a major ecological crisis affecting shallow and deep-water settings over the entire Mediterranean basin. However, the evolution of the MSC and its ecological impacts have mainly been explained on the basis of sediments from onshore outcrops. Lack of complete and physically connected records from onshore and offshore settings has inhibited comprehensive understanding of basin behaviour during the MSC. Herein we present a continuous record from an intermediate-depth basin on the Balearic Promontory that comprises late Tortonian–Messinian marls and evaporitic beds from the first MSC phase (i.e., Primary Lower Gypsum-PLG stage). Well-log and biostratigraphic data allow us establishing a large-scale calibration to the astronomical solutions, and to correlate pre-MSC sediments with classical rhythmic successions outcropping onshore. Thickness and characteristic sedimentary patterns observed in the offshore evaporitic records resemble those from marginal PLG sequences. Furthermore, seismic reflectors from a Bedded Unit (BU), which corresponds to an evaporitic interval according to well-to-seismic ties, are correlated with the onshore PLG sequences. This correlation constitutes the first attempt to link well-known marginal sequences with intermediate-depth offshore settings, which have previously only been studied through seismic imaging. Our time-calibration provides direct evidence supporting a synchronous onset of the PLG phase between onshore and offshore settings along the southwestern Balearic Promontory margin. Those BU reflectors, which were positively correlated to the PLG, were likely precipitated offshore the continental shelf at Messinian times. These results suggest that gypsum precipitation and/or preservation was not always limited to 200 m water-depths and could occur in non-silled basins. Finally, we only found a major erosion at the top of the PLG sequences, implying that the MSC drawdown occurred after the precipitation of the onshore lower evaporites. Studied sequences provide new insights into the PLG precipitation/preservation settings, as well as into the land-sea correlations of MSC units, and thus could potentially help refine current MSC models.
International Journal of Greenhouse Gas Control, 2014
ABSTRACT The objective of the CO2FieldLab project was to demonstrate that adequate monitoring met... more ABSTRACT The objective of the CO2FieldLab project was to demonstrate that adequate monitoring methods can be deployed to document potential leaks of CO2 from subsurface reservoirs. For this, a shallow injection experiment through permeable sediment was designed and conducted at Svelvik (Norway) in September 2011. The goal was to produce a CO2 leak in order to assess the relative sensitivity of several geochemical and geophysical CO2 monitoring tools. A total mass of 1.67 tons of CO2 was injected at a depth of 20 m through a 45° inclined well over a 6 day period. Time-lapse induction logging and downhole resistivity monitoring from a permanent dipole–dipole array observatory prove to be very sensitive to the presence of CO2 in the shallow subsurface after the start of injection. Electrical resistivity response correlates with progressive CO2 dissolution in groundwater, with resistivity and pH values decreasing due to the increase of bicarbonate and dissolved species. The CO2 plume is channelled by enhanced permeability layers, with updip migration of the gas plume to the North. Other processes responsible for resistivity changes were fresh/salt water mixing, tidal effects and rainfall.
ABSTRACT The Messinian Salinity Crisis is a huge outstanding succession of events that has deeply... more ABSTRACT The Messinian Salinity Crisis is a huge outstanding succession of events that has deeply modified the Mediterranean area within a short time span at the geological scale. The seismic atlas of the Messinian markers in the Mediterranean and Black seas is a collective work summarizing, in one publication with a common format, the most relevant seismic features related to this exceptionnal event. Seismic information has been collected over many years from the offshore domain. Throughout 13 study areas, the seismic facies, geometry and extent of the Messinian markers (surfaces and depositional units) are described. The absolute time succession of the Messinian events, or the processes responsible for their occurrence in space and time are not discussed. The objectives of this atlas are: (1) to image the Messinian seismic markers from the main margins and basins; (2) to propose a new global and consistent terminology for these markers in the entire offshore Mediterranean area and (3) to make this information accessible to the non-geophysicist community. Interpreted seismic data were carefully selected according to their quality, position and significance in order to reach these objectives, and are presented here. Raw and interpreted seismic profiles are available on CD-Rom. The atlas costs 20 euros and can be ordered online here: http://ccgm.org/en/home/148-seismic-atlas-of-the-messinian-salinity-crisis-markers-2853630978.html or http://www.geosoc.fr/publication/memoires/memoires-nouvelle-serie.html
The principal driving force of slope movements is generally considered to be gravity, with the ma... more The principal driving force of slope movements is generally considered to be gravity, with the main triggering factor being the increase of pore pressures by the presence of water contained in the geological environment. It is however difficult to anticipate the ...
... About 5.6 Ma ago (Clauzon et al., 1996 and Krijgsman et al., 1999a), the salinity crisis led ... more ... About 5.6 Ma ago (Clauzon et al., 1996 and Krijgsman et al., 1999a), the salinity crisis led to a dramatic sea-level fall in the Mediterranean basin (Ryan, 1976, Clauzon, 1982, Lofi, 2002 and Steckler et al., 2003). Clauzon et al. ...
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