The Gabes Gulf, recognized for its marine productivity, is the subject of high anthropogenic pres... more The Gabes Gulf, recognized for its marine productivity, is the subject of high anthropogenic pressure. The aim of this synthesis work is to present a global view of metal contamination in marine sediments in the Gabes Gulf and its relationship with anthropogenic sources. The study is based on descriptive and chemometric methods, where contamination indices were used (Enrichment Factor and Geoaccumulation Index). The examined sites, classified in an increasing order of contamination are: southern coast of Sfax, northern coast of Sfax, and Gabes coast. Contamination is mainly explained by the industrial activity of phosphate treatment. Phosphogypsum, which is the main product enriched with metals, is evacuated directly into the sea along the Gabes coast, while small quantities were evacuated into the sea in the northern coast of Sfax. In the southern coast of Sfax, only a part of the phosphogypsum leaching water is drained into the sea. The contamination indices were calculated using ...
Since 1970, Ghannouch field, southeastern Tunisia, has been recognized as an industrial area spec... more Since 1970, Ghannouch field, southeastern Tunisia, has been recognized as an industrial area specialized in mining phosphate processing industry. Furthermore, this region has also been characterized by an excessive groundwater pumping to meet extensive agricultural activities and increasing industrial installation. Degradation of groundwater quality and its contamination became a serious concern of the communities. This manuscript describes the findings of a study performed to investigate the characteristics of groundwater quality and identify the contribution of the different factors to its chemical pollution and degradation. Groundwater was sampled in different locations of the study area. Physical parameters such as EC, TDS, pH were measured and major ions where analyzed. Geochemical, kriging techniques and statistical modeling was used to assess groundwater mineralization. Results show that dominant chemical facies of groundwater is Na-Cl-Ca-SO4-F due to rock-water interaction, ...
In previous studies, an emphasis on the particular vulnerability of small island states to future... more In previous studies, an emphasis on the particular vulnerability of small island states to future sea-level rise and the intensity of increasing storm surges has been discussed. This preliminary assessment develops a Coastal Vulnerability Index (CVI) along the 202 km long coastline of Ngazidja Island (formerly Grande Comore, Comoros Archipelago), using fieldwork, remote sensing, and geographic information system tools (GIS). The CVI considers five structural variables: (a) geology, (b) geomorphology, (c) topography, (d) shoreline change, and (e) shoreline exposure). It also considers three physical process variables: (f) relative sea-level rise, (g) significant wave height, and (h) mean tide range). The land-use variable was added in this analysis to highlight the human asset exposure in the surrounding areas. Each variable was ranked based on local physical and hydrodynamic conditions and their vulnerability contribution to sea-level rise. The CVI was computed in 270 sections. Acco...
The present work investigates the aspects of anthropogenic contamination in the littoral zone of ... more The present work investigates the aspects of anthropogenic contamination in the littoral zone of Gabès city (Tunisia). Special interest was addressed to the effects of chemical industries and coastal dynamics on the pollutant input and distribution along the coast. As a first step, 16 superficial sediment samples were collected including 8 items on the beach and 8 in the intertidal zone. Subsequently, geochemical and granulometric analyses were carried out. Heavy metals (Zn, Cu, Pb, and Cd) as well as sulfates, phosphorus, chlorine, sodium, calcium, bromine, and the percentage of the fine fraction were quantified in all samples. Two approaches were adopted for the interpretation of results. The first descriptive approach revealed that the coastline is subjected to fairly significant anthropogenic pressure. Results showed that the littoral zone is highly contaminated by various toxic elements, notably heavy metals. It seems that the coastal dynamics have a major contribution in the transport and deposition of several contaminants. The second approach allowed identifying the potential origins of pollutants based on a principal component analysis. Results proved that the impact of releases from chemical industries is the most significant. More efforts are required to investigate the mechanisms of ion transfer and exchange between pollutants and the various media such as sediments, water, and air.
Mid-Holocene sea-level emergence was recorded along a mid-latitude coastal site in the Gulf of Ga... more Mid-Holocene sea-level emergence was recorded along a mid-latitude coastal site in the Gulf of Gabes, Tunisia, in beach rock deposits. However, the post-emergence sea-level curve and associated hydro-sedimentary processes have rarely been documented. This study presents new records of sea-level changes along the Tunisian coast since the mid-Holocene. Each phase of the sea-level curve was evidenced and supported by lithostratigraphic, morphological and archaeologic markers. Post-emergence sea-level fall due to postglacial isostatic rebound was recognized in regressive sequences which vary depending on available accommodation space, from a small pocket beach to a well developed dune system. Sea-level stabilization following isostatic rebound has promoted the end phase deposits of the regressive sequences. However, this stability was interrupted during the late Holocene by a high-energy storm event that accumulated a transgressive boulder unit at 2 m above present. Shape and disposition of the boulder ridge behind a prograding modern shoreline suggests that sea level has not changed during the late Holocene. The existence of a Roman fish pond on the upper foreshore confirms stability of sea level during the last two millennia. The combination of lithostratigraphic, morphological and archaeologic markers represents a tool for improving the accuracy of dating of erosional and depositional periods in mid-coastal sections.
The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the sh... more The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the shoreline. The quantification of the pollution level was mainly based on seawater analysis. However, in this environment, the sediment characterization, using quality indicators, may constitute an accurate approach. The latter can be particularly appropriate to define heavy metals pollution degree. Chemical analyses of Cd, Cu, Zn, and Fe were undertaken for a total of 45 surface marine sediment samples of Gabes city coast. There is a significant extension of pollution, strongly influenced by the dominant longshore current. The studied sediments were found usually enriched with Cu, Cd, and Zn. These anthropogenic heavy metals have identical behavior and similar distribution. These metals did not show any correlations with Fe chosen as natural tracer. The multi-element indices used permitted to conclude that 70% of sampling sites are highly affected by heavy metal contamination and associated with very high ecological risk. These indices use a simple contamination factor, which, however, would not take account of the sedimentary inputs and the complex sediment behavior. Consequently, modified indices, employing enrichment factor, were used and demonstrated better to assess pollution and ecological risk.
In the Gafsa basin, the Paleocene-Eocene interval is represented by the evaporite deposits of The... more In the Gafsa basin, the Paleocene-Eocene interval is represented by the evaporite deposits of Thelja Formation, the phosphatic series of Chouabine Formation, and the carbonate bed of Kef Eddour Formation. The Thanetian-Ypresian transition lies within the lower unit (C1) of the Chouabine Formation. These different facies characterize circalittoral to margino-littoral paleoenvironments. Sedimentological analyzes of this interval allowed to define eleven genetic sequences. The comparison of these sequences with the global chart of Sneeden and Liu (2010) shows a good correlation with the third-order cycles. In the eastern part of the Gafsa basin (Jebel Chemsi), the Paleocene-Ypresian transition is characterized by a marly-carbonate series deposited in an isolated open marine environment not recording minor relative sea-level changes. The Selandian Pg10 major maximum flooding is detected within the S2 sequence of the Oued Thelja section. The Thanetian-Ypresian transition (55.8 Ma), identified in the S7 sequence of this section, coincides with a major sea-level rise at the origin of phosphate sedimentation onset in the Gafsa basin and around the Kasserine Island.
The continental shelf of the Gulf of Gabes is outlined, during the MIS 5c and MIS 5a onshore high... more The continental shelf of the Gulf of Gabes is outlined, during the MIS 5c and MIS 5a onshore highstands, by the genesis of forced regressive beach ridges situated respectively at-19 m b.s.l/100 ka and-8 m b.s.l/80 ka. This area, considered as a stable domain since at least the last 130 ka (Bouaziz et al. 2003), is a particular zone for the reconstruction of the late quaternary sea-level changes in the region. Shuttle Radar Topography Mission (SRTM) data and field observations are highlighted to deduce interaction between hydrodynamic factors and antecedent topography. Variations in geomorphology were attributed to geological inheritance. Petrography and sedimentary facies of the submerged coastal ridges reveal that the palaeocoastal morphology was more agitated than today and the fluvial discharges are consistent. Actual morphologic trend deduced from different environment coasts (sandy coasts, sea cliffs and tidal flat) is marked by accumulation of marine sands and progradation. Keywords. MIS 5c and MIS 5a; beach ridges; sea level changes; palaeocoastal morphology; Gulf of Gabes; Tunisia.
Abstract The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and th... more Abstract The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and the deterioration of water quality. The large amount of water shown to exchange tidally between the lagoon and the open sea suggests that while water per se is ...
La morphologie de l'embouchure tidale d'oued el Melah est caractérisée par la récurrence de pério... more La morphologie de l'embouchure tidale d'oued el Melah est caractérisée par la récurrence de périodes d'obturations du chenal. Ce phénomène a été mis en évidence par un suivi régulier du site d'étude. Il se produit régulièrement suivant deux modalités et à deux échelles temporelles différentes. L'obturation de l'embouchure à l'échelle événementielle dure une semaine. Ce phénomène est assuré par la dérive littorale et les processus de swash. Les sédiments charriés parallèlement à la côte sont déposés au niveau de l'embouchure qui constitue un repli littoral. Cependant, l'obstruction de l'embouchure à l'échelle saisonnière peut durer deux mois. La modalité de l'obturation repose sur l'engraissement de la plage par l'action d'une houle de court fetch. Il s'agit d'un remplissage progressif du chenal de communication avec la mer et un rehaussement de l'ensemble de l'embouchure. La réouverture du chenal est générée suite à l'érosion de la berme. A l'échelle événementielle, l'emplacement de l'embouchure est figé. Par contre, à l'échelle saisonnière le tracé de l'embouchure migre latéralement dans un secteur large de 200 m. Il suit le tracé des chenaux d'inondations, creusés par l'eau de mer à l'occasion du débordement de la berme par la houle de long fetch. Après réouverture, les deux rives de l'embouchure montrent la superposition des dépôts de la zone supratidale sur les dépôts de la zone intertidale.
nous avons procédé par une description morphologique détaillée, appuyée par une étude granulométr... more nous avons procédé par une description morphologique détaillée, appuyée par une étude granulométrique. Les résultats de cette étude montrent qu'il s'agit de deux systèmes morphodynamiques différents. Le premier, caractéristique de la côte nord-est, est défini par des conditions hydrodynamiques turbulentes, favorisant l'épanouissement d'un paysage morphologique exposé. Le second, caractéristique de la côte sud-est, constitue un milieu abrité avec un paysage morphologique peu développé. Toutefois, l'action de la dérive littorale demeure déterminante dans l'édification et l'allongement des flèches sableuses. Il s'agit de deux dérives littorales divergentes de part et d'autre de la presqu'île d'el Hadhria.
The Trab El Makhadha beach-ridge plain presents a progradational shoreline feature on the Gulf of... more The Trab El Makhadha beach-ridge plain presents a progradational shoreline feature on the Gulf of Gabes (Tunisia). Diachronic analysis coupled with a morpho-sedimentary approach was applied to elucidate the genesis mode of the beach-ridge plain, its sedimentary sources, and the climatic conditions responsible for the prograding trends in the Gulf of Gabes. Shapes, dimensions, sedimentologic compositions, and other textural parameters of the sandy ridges have been analyzed. Therein, we found that the Trab El Makhdha Coast is made up of two distinctive categories of eolian beach-ridge complex (progradational sequences), implying a significant change in climatic and hydrological conditions during the deposition of each ridge. In the Holocene sequence, about 5600 14 C years old, the predominance of detrital material suggests an important contribution to sediment supply from continental input. The preservation of the eolian beach ridge and its adjacent marine sediment has been favored by the postglacial hydro-isostatic rebound. Today, the paucity of rainfall is reflected by the decrease in input of terrigenous material. Therefore, the modern sequence, which has been emerging since 1987, is made mainly of bioclastic sand supplied by subaqueous shoals due to a rapid rise in sea level. The observed decrease of sea level around 2100 14 C yr B.P. largely contributed to the formation of the swale. The formation of the beach-ridge plain shows that since the middle Holocene highstand the coastal segment of Trab El Makhadha has been governed by equilibrium of sediment abundance.
Le littoral de Trab el Makhadha (golfe de Gabès) est caractérisé par une évolution morphologique ... more Le littoral de Trab el Makhadha (golfe de Gabès) est caractérisé par une évolution morphologique rapide et réversible à l’échelle saisonnière et évènementielle. Un suivi quotidien de l’évolution du profil transversal durant deux années (septembre 2007-novembre 2009) a mis en évidence les facteurs hydrodynamiques à l’origine du transport sédimentaire ainsi que le temps d’ajustement morphologique. Le changement morphologique du littoral de Trab el Makhadha, à l’échelle événementielle, est contrôlé par l’action du vent et des courants locaux ayant le temps d’ajustement morphologique le plus court. La cyclicité saisonnière entre accrétion estival et érosion hivernale du profil transversal de la plage est dictée par l’action de la houle. Le bilan sédimentaire, au cours des trente années précédentes, est excédentaire. La progradation du littoral est matérialisée par la mise en place, depuis les années 1980, d’un cordon sableux de 2 m de hauteur. La genèse du cordon côtier est contemporaine à l’accélération de l’élévation récente du niveau marin.
Over the last 30 years El Grine coast recorded significant morphological changes leading to the s... more Over the last 30 years El Grine coast recorded significant morphological changes leading to the shoreline progradation. Diachronic coastal evolution, through a set of satellite images data, supported by sedimentologic analysis of five sand cores have been applied to elucidate tidal flat reaction following the recent sea level rise. We found that an emerging sandy barrier and salt marsh domain were shaped by the local hydro-sedimentary processes. The marine sediments, mobilised by wave and tide currents, have been the sole sedimentary source. Recent sandy accumulations, occurred around 1987, have been able to balance a recent sea level rise. While during a mid-Holocene period, El Grine coast was governed by net erosion tendency inducing cliff recession.
The Gabes Gulf, recognized for its marine productivity, is the subject of high anthropogenic pres... more The Gabes Gulf, recognized for its marine productivity, is the subject of high anthropogenic pressure. The aim of this synthesis work is to present a global view of metal contamination in marine sediments in the Gabes Gulf and its relationship with anthropogenic sources. The study is based on descriptive and chemometric methods, where contamination indices were used (Enrichment Factor and Geoaccumulation Index). The examined sites, classified in an increasing order of contamination are: southern coast of Sfax, northern coast of Sfax, and Gabes coast. Contamination is mainly explained by the industrial activity of phosphate treatment. Phosphogypsum, which is the main product enriched with metals, is evacuated directly into the sea along the Gabes coast, while small quantities were evacuated into the sea in the northern coast of Sfax. In the southern coast of Sfax, only a part of the phosphogypsum leaching water is drained into the sea. The contamination indices were calculated using ...
Since 1970, Ghannouch field, southeastern Tunisia, has been recognized as an industrial area spec... more Since 1970, Ghannouch field, southeastern Tunisia, has been recognized as an industrial area specialized in mining phosphate processing industry. Furthermore, this region has also been characterized by an excessive groundwater pumping to meet extensive agricultural activities and increasing industrial installation. Degradation of groundwater quality and its contamination became a serious concern of the communities. This manuscript describes the findings of a study performed to investigate the characteristics of groundwater quality and identify the contribution of the different factors to its chemical pollution and degradation. Groundwater was sampled in different locations of the study area. Physical parameters such as EC, TDS, pH were measured and major ions where analyzed. Geochemical, kriging techniques and statistical modeling was used to assess groundwater mineralization. Results show that dominant chemical facies of groundwater is Na-Cl-Ca-SO4-F due to rock-water interaction, ...
In previous studies, an emphasis on the particular vulnerability of small island states to future... more In previous studies, an emphasis on the particular vulnerability of small island states to future sea-level rise and the intensity of increasing storm surges has been discussed. This preliminary assessment develops a Coastal Vulnerability Index (CVI) along the 202 km long coastline of Ngazidja Island (formerly Grande Comore, Comoros Archipelago), using fieldwork, remote sensing, and geographic information system tools (GIS). The CVI considers five structural variables: (a) geology, (b) geomorphology, (c) topography, (d) shoreline change, and (e) shoreline exposure). It also considers three physical process variables: (f) relative sea-level rise, (g) significant wave height, and (h) mean tide range). The land-use variable was added in this analysis to highlight the human asset exposure in the surrounding areas. Each variable was ranked based on local physical and hydrodynamic conditions and their vulnerability contribution to sea-level rise. The CVI was computed in 270 sections. Acco...
The present work investigates the aspects of anthropogenic contamination in the littoral zone of ... more The present work investigates the aspects of anthropogenic contamination in the littoral zone of Gabès city (Tunisia). Special interest was addressed to the effects of chemical industries and coastal dynamics on the pollutant input and distribution along the coast. As a first step, 16 superficial sediment samples were collected including 8 items on the beach and 8 in the intertidal zone. Subsequently, geochemical and granulometric analyses were carried out. Heavy metals (Zn, Cu, Pb, and Cd) as well as sulfates, phosphorus, chlorine, sodium, calcium, bromine, and the percentage of the fine fraction were quantified in all samples. Two approaches were adopted for the interpretation of results. The first descriptive approach revealed that the coastline is subjected to fairly significant anthropogenic pressure. Results showed that the littoral zone is highly contaminated by various toxic elements, notably heavy metals. It seems that the coastal dynamics have a major contribution in the transport and deposition of several contaminants. The second approach allowed identifying the potential origins of pollutants based on a principal component analysis. Results proved that the impact of releases from chemical industries is the most significant. More efforts are required to investigate the mechanisms of ion transfer and exchange between pollutants and the various media such as sediments, water, and air.
Mid-Holocene sea-level emergence was recorded along a mid-latitude coastal site in the Gulf of Ga... more Mid-Holocene sea-level emergence was recorded along a mid-latitude coastal site in the Gulf of Gabes, Tunisia, in beach rock deposits. However, the post-emergence sea-level curve and associated hydro-sedimentary processes have rarely been documented. This study presents new records of sea-level changes along the Tunisian coast since the mid-Holocene. Each phase of the sea-level curve was evidenced and supported by lithostratigraphic, morphological and archaeologic markers. Post-emergence sea-level fall due to postglacial isostatic rebound was recognized in regressive sequences which vary depending on available accommodation space, from a small pocket beach to a well developed dune system. Sea-level stabilization following isostatic rebound has promoted the end phase deposits of the regressive sequences. However, this stability was interrupted during the late Holocene by a high-energy storm event that accumulated a transgressive boulder unit at 2 m above present. Shape and disposition of the boulder ridge behind a prograding modern shoreline suggests that sea level has not changed during the late Holocene. The existence of a Roman fish pond on the upper foreshore confirms stability of sea level during the last two millennia. The combination of lithostratigraphic, morphological and archaeologic markers represents a tool for improving the accuracy of dating of erosional and depositional periods in mid-coastal sections.
The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the sh... more The urbanized coastal zones are frequently faced to various pollutant discharges mainly in the shoreline. The quantification of the pollution level was mainly based on seawater analysis. However, in this environment, the sediment characterization, using quality indicators, may constitute an accurate approach. The latter can be particularly appropriate to define heavy metals pollution degree. Chemical analyses of Cd, Cu, Zn, and Fe were undertaken for a total of 45 surface marine sediment samples of Gabes city coast. There is a significant extension of pollution, strongly influenced by the dominant longshore current. The studied sediments were found usually enriched with Cu, Cd, and Zn. These anthropogenic heavy metals have identical behavior and similar distribution. These metals did not show any correlations with Fe chosen as natural tracer. The multi-element indices used permitted to conclude that 70% of sampling sites are highly affected by heavy metal contamination and associated with very high ecological risk. These indices use a simple contamination factor, which, however, would not take account of the sedimentary inputs and the complex sediment behavior. Consequently, modified indices, employing enrichment factor, were used and demonstrated better to assess pollution and ecological risk.
In the Gafsa basin, the Paleocene-Eocene interval is represented by the evaporite deposits of The... more In the Gafsa basin, the Paleocene-Eocene interval is represented by the evaporite deposits of Thelja Formation, the phosphatic series of Chouabine Formation, and the carbonate bed of Kef Eddour Formation. The Thanetian-Ypresian transition lies within the lower unit (C1) of the Chouabine Formation. These different facies characterize circalittoral to margino-littoral paleoenvironments. Sedimentological analyzes of this interval allowed to define eleven genetic sequences. The comparison of these sequences with the global chart of Sneeden and Liu (2010) shows a good correlation with the third-order cycles. In the eastern part of the Gafsa basin (Jebel Chemsi), the Paleocene-Ypresian transition is characterized by a marly-carbonate series deposited in an isolated open marine environment not recording minor relative sea-level changes. The Selandian Pg10 major maximum flooding is detected within the S2 sequence of the Oued Thelja section. The Thanetian-Ypresian transition (55.8 Ma), identified in the S7 sequence of this section, coincides with a major sea-level rise at the origin of phosphate sedimentation onset in the Gafsa basin and around the Kasserine Island.
The continental shelf of the Gulf of Gabes is outlined, during the MIS 5c and MIS 5a onshore high... more The continental shelf of the Gulf of Gabes is outlined, during the MIS 5c and MIS 5a onshore highstands, by the genesis of forced regressive beach ridges situated respectively at-19 m b.s.l/100 ka and-8 m b.s.l/80 ka. This area, considered as a stable domain since at least the last 130 ka (Bouaziz et al. 2003), is a particular zone for the reconstruction of the late quaternary sea-level changes in the region. Shuttle Radar Topography Mission (SRTM) data and field observations are highlighted to deduce interaction between hydrodynamic factors and antecedent topography. Variations in geomorphology were attributed to geological inheritance. Petrography and sedimentary facies of the submerged coastal ridges reveal that the palaeocoastal morphology was more agitated than today and the fluvial discharges are consistent. Actual morphologic trend deduced from different environment coasts (sandy coasts, sea cliffs and tidal flat) is marked by accumulation of marine sands and progradation. Keywords. MIS 5c and MIS 5a; beach ridges; sea level changes; palaeocoastal morphology; Gulf of Gabes; Tunisia.
Abstract The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and th... more Abstract The Boughrara Lagoon located in southern Tunisia shows evidence of eutrophication and the deterioration of water quality. The large amount of water shown to exchange tidally between the lagoon and the open sea suggests that while water per se is ...
La morphologie de l'embouchure tidale d'oued el Melah est caractérisée par la récurrence de pério... more La morphologie de l'embouchure tidale d'oued el Melah est caractérisée par la récurrence de périodes d'obturations du chenal. Ce phénomène a été mis en évidence par un suivi régulier du site d'étude. Il se produit régulièrement suivant deux modalités et à deux échelles temporelles différentes. L'obturation de l'embouchure à l'échelle événementielle dure une semaine. Ce phénomène est assuré par la dérive littorale et les processus de swash. Les sédiments charriés parallèlement à la côte sont déposés au niveau de l'embouchure qui constitue un repli littoral. Cependant, l'obstruction de l'embouchure à l'échelle saisonnière peut durer deux mois. La modalité de l'obturation repose sur l'engraissement de la plage par l'action d'une houle de court fetch. Il s'agit d'un remplissage progressif du chenal de communication avec la mer et un rehaussement de l'ensemble de l'embouchure. La réouverture du chenal est générée suite à l'érosion de la berme. A l'échelle événementielle, l'emplacement de l'embouchure est figé. Par contre, à l'échelle saisonnière le tracé de l'embouchure migre latéralement dans un secteur large de 200 m. Il suit le tracé des chenaux d'inondations, creusés par l'eau de mer à l'occasion du débordement de la berme par la houle de long fetch. Après réouverture, les deux rives de l'embouchure montrent la superposition des dépôts de la zone supratidale sur les dépôts de la zone intertidale.
nous avons procédé par une description morphologique détaillée, appuyée par une étude granulométr... more nous avons procédé par une description morphologique détaillée, appuyée par une étude granulométrique. Les résultats de cette étude montrent qu'il s'agit de deux systèmes morphodynamiques différents. Le premier, caractéristique de la côte nord-est, est défini par des conditions hydrodynamiques turbulentes, favorisant l'épanouissement d'un paysage morphologique exposé. Le second, caractéristique de la côte sud-est, constitue un milieu abrité avec un paysage morphologique peu développé. Toutefois, l'action de la dérive littorale demeure déterminante dans l'édification et l'allongement des flèches sableuses. Il s'agit de deux dérives littorales divergentes de part et d'autre de la presqu'île d'el Hadhria.
The Trab El Makhadha beach-ridge plain presents a progradational shoreline feature on the Gulf of... more The Trab El Makhadha beach-ridge plain presents a progradational shoreline feature on the Gulf of Gabes (Tunisia). Diachronic analysis coupled with a morpho-sedimentary approach was applied to elucidate the genesis mode of the beach-ridge plain, its sedimentary sources, and the climatic conditions responsible for the prograding trends in the Gulf of Gabes. Shapes, dimensions, sedimentologic compositions, and other textural parameters of the sandy ridges have been analyzed. Therein, we found that the Trab El Makhdha Coast is made up of two distinctive categories of eolian beach-ridge complex (progradational sequences), implying a significant change in climatic and hydrological conditions during the deposition of each ridge. In the Holocene sequence, about 5600 14 C years old, the predominance of detrital material suggests an important contribution to sediment supply from continental input. The preservation of the eolian beach ridge and its adjacent marine sediment has been favored by the postglacial hydro-isostatic rebound. Today, the paucity of rainfall is reflected by the decrease in input of terrigenous material. Therefore, the modern sequence, which has been emerging since 1987, is made mainly of bioclastic sand supplied by subaqueous shoals due to a rapid rise in sea level. The observed decrease of sea level around 2100 14 C yr B.P. largely contributed to the formation of the swale. The formation of the beach-ridge plain shows that since the middle Holocene highstand the coastal segment of Trab El Makhadha has been governed by equilibrium of sediment abundance.
Le littoral de Trab el Makhadha (golfe de Gabès) est caractérisé par une évolution morphologique ... more Le littoral de Trab el Makhadha (golfe de Gabès) est caractérisé par une évolution morphologique rapide et réversible à l’échelle saisonnière et évènementielle. Un suivi quotidien de l’évolution du profil transversal durant deux années (septembre 2007-novembre 2009) a mis en évidence les facteurs hydrodynamiques à l’origine du transport sédimentaire ainsi que le temps d’ajustement morphologique. Le changement morphologique du littoral de Trab el Makhadha, à l’échelle événementielle, est contrôlé par l’action du vent et des courants locaux ayant le temps d’ajustement morphologique le plus court. La cyclicité saisonnière entre accrétion estival et érosion hivernale du profil transversal de la plage est dictée par l’action de la houle. Le bilan sédimentaire, au cours des trente années précédentes, est excédentaire. La progradation du littoral est matérialisée par la mise en place, depuis les années 1980, d’un cordon sableux de 2 m de hauteur. La genèse du cordon côtier est contemporaine à l’accélération de l’élévation récente du niveau marin.
Over the last 30 years El Grine coast recorded significant morphological changes leading to the s... more Over the last 30 years El Grine coast recorded significant morphological changes leading to the shoreline progradation. Diachronic coastal evolution, through a set of satellite images data, supported by sedimentologic analysis of five sand cores have been applied to elucidate tidal flat reaction following the recent sea level rise. We found that an emerging sandy barrier and salt marsh domain were shaped by the local hydro-sedimentary processes. The marine sediments, mobilised by wave and tide currents, have been the sole sedimentary source. Recent sandy accumulations, occurred around 1987, have been able to balance a recent sea level rise. While during a mid-Holocene period, El Grine coast was governed by net erosion tendency inducing cliff recession.
Uploads
Papers by Maher Gzam