Northeastern Tunisia Research Articles

Lithology and planktic foraminifera biostratigraphy of Aptian–Albian boundary as encountered in Jebel Sidi Salem (northeastern Tunisia)

The Aptian–Albian boundary has long been difficult to identify along the foreland basin of the Tunisian Atlas, although ammonites occur in the Fahden Formation. The revision of Aptian–Albian series from Jebel Sidi Salem, in the northeastern part of the Tunisian Ridge, provides new data for the recognition of this boundary. The Jebel Sidi Salem section contains a rich succession of planktic foraminifers’ index species which document a complete marine record of Aptian–Albian boundary with no sign of redeposition. Six zones of planktic foraminifera have been identified through the late Aptian to middle Albian; including Globigerinelloides algerianus Zone, Hedbergella trocoidea Zone, Planomalina cheniourensis Zone, Paraticinella eubejaouensis/Ticinella roberti Zone, Hedbergella planispira Zone and Ticinella primula Zone.

Quaternary Alluvial Aquifer Study Using Integrated Geophysical Approach in Zaghouan Plain (Northeastern Tunisia)

The study area Zaghouan Plain (northeastern Tunisia) is unique for its strategic Quaternary aquifer, which is, in a great proportion, composed of sand lenses that vary in thicknesses and forms. Conducting an integrative approach based on regional mapping and local studies helped provide precise calibration to identify convenient areas for hydrogeological explorations, which are focused on heterogeneous alluvial and fluvio-deltaic aquifers. To enhance the location and the extension of low density related to sand lenses porous aquifers, a regional gravity analysis supported by focused seismic interpretation was performed. Thus, advanced analyses were conducted in the Zaghouan Plain through the implementation of a regional–residual separation, a radially averaged power spectrum and tilt/TDX filter density models. During the process, two major negative gravity anomalies, associated with developed lenses system between Zaghouan Mountain and Henchir Bouslim anticline, were revealed. The anomalies differed in direction from E–W to NW–SE. They also varied widthwise from 1000 to 3000 m and depthwise from 1500 to 2000 m. Hence, with the aim of highlighting the detailed geometry of sand lenses and locating the most interesting zone for future hydrogeological exploration and/or recharge process, 1D time-domain electromagnetic and 2D electrical resistivity tomography studies were conducted and various techniques were applied in a local area situated in the main negative gravity anomaly.

Application of electrical resistivity tomography and hydro-chemical analysis for an integrated environmental assessment

Municipal solid waste disposal sites generate groundwater contamination through leachate release to the surrounding environment, causing various harmful and deleterious effects. Thus, an integrated assessment of landfilling impact on the environment via the combination of electrical resistivity tomography (ERT) and hydro-chemical analysis from existing wells was undertaken to ascertain the contamination of both surface and groundwater near the Bizerte landfill site, northeastern Tunisia. The ERT measurement indicated a polluted depth of over 20 m beneath the surface which coincides with marly substratum.Similarly, hydro-chemical analysis showed that continuous leachate generation obviously affected chemical properties of surface and groundwater, especially an increase in heavy metals contents (lead, cadmium and nickel contents). The results also indicated significant microbiological contaminations of the water samples. Nemerow pollution index (WQI) for water classification indicated that all sites had clean water with respect to metal contamination, except for R1 and R2 (surface water), which have WQI values of 2.5 and 2.1, respectively. Based on those results, it is recommended to strictly monitor leachate generation, surface water and groundwater quality in the Bizerte landfill for an integrated sustainable environmental assessment.

The Eocene‐Oligocene Transition in the South‐Western Neo‐Tethys (Tunisia): Astronomical Calibration and Paleoenvironmental Changes

AbstractA detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South‐Western margin of the Neo‐Tethys ocean (Tunisia) covering the Eocene‐Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera compacta nannofossil Zone (CNE21) to the Reticulofenestra umbilicus Zone (CNO2). The Bc of Clausicoccus subdistichus coincides in northeastern Tunisia with the extinction of hantkeninids and is thus used here to define the Eocene/Oligocene boundary (EOB) at 34.03 Ma. Calcareous nannofossil assemblages suggest a significant change from oligotrophic/warm surface waters during the late Eocene to eutrophic/cool waters during the early Oligocene. The observed changes in trophic conditions are synchronous with a shallowing trend testified by an increase in nearshore species and enhanced terrigenous input. Major environmental changes occurred at the EOB and across glaciation event Oi‐1a whereas we record a poor imprint of glaciation event Oi‐1. Three orbital configurations have been distinguished: (1) The late Eocene is characterized by a prominent 405‐kyr cycle and a weak obliquity component; (2) the onset of cooling at 34.35 Ma coincides with the rosette‐shaped discoaster extinction and is reflected by a shift toward enhanced obliquity and short‐eccentricity cycles. The installation of a fully developed AIS (event Oi‐1a, 32.75 Ma) shows the most pronounced obliquity imprint reflecting an increased influence of high‐latitude climate processes; (3) after 31.75 Ma, the obliquity decreases in coincidence with the return to a dominant long‐eccentricity cycle.

Active fault segmentation in Northern Tunisia

Active shortening structures in Northern Tunisia have developed by tectonic inversion since the Pliocene, after Late Miocene extensional collapse of the whole region. Restored Plio-Quaternary deformation observed on reflection seismic lines indicates deformation rates around 0.6–0.8 mm/yr in the studied segments and larger amounts of shortening to the West of Northern Tunisia (16%) than to the East (7%), which suggests tectonic inversion started earlier to the West and later propagated eastwards, reaching Northeastern Tunisia in the Late Pliocene. This shortening is registered on striated pebbles in Quaternary alluvial terraces and fault-slip data giving two populations of strain ellipsoids with N–S and WNW-ESE maximum shortening. Morphometric analysis in combination with field fault segmentation mapping show that topographic uplift and drainage rejuvenation occurs in relation to 20–30 km long ENE-WSW reverse fault segments and related antiforms that are offset and linked by E-W to WNW-ESE dextral and NE-SW-oriented sinistral faults. The largest fully linked fault system is the Alia-Thibar fault. This 130 km long fault zone shows an helicoidal geometry with five different fault segments, including reverse, dextral, sinistral and oblique faults. Due to the young age of tectonic inversion, after late Miocene extensional collapse of the region, the present relief of Northern Tunisia is characteristic of a young thrust and fold belt, with dominating axial valleys along synforms and an incipient transverse drainage development propagating from West to East.

Assessment of groundwater quality based on GIS and geochemical methods: coastal aquifer of Bouficha (North-Eastern Tunisia)

In Tunisia, Groundwater is an important water source for domestic, agricultural and industrial uses, but the deterioration of its quality, under the influence of anthropogenic activities and natural factors, limits its suitability for human consumption and irrigation. The present study was carried out to assess groundwater quality in Bouficha aquifer in north-eastern Tunisia using geochemical, geospatial and statistical techniques. The relationship between groundwater quality and Land Use Land Cover (LULC) patterns were also explored using remote sensing, geographic information system (GIS) and Landsat satellite images. Groundwater samples were collected from sixteen wells in April 2015 and analyzed for their physical and chemical characteristics. Concentrations of major cations and anions in the groundwater vary spatially. The dominant water types in the investigation area are Na-Cl and Ca–SO4. A basic statistical study, applying hierarchical classification analysis confirms the existence of two groundwater types. To evaluate the suitability of groundwater for irrigation, chemical data were assessed using methods such as Electrical Conductivity, Kelley’s ratio, Sodium Absorption Ratio, Magnesium Hazards, as well as Residual Sodium Carbonate. Regarding drinking groundwater assessment, the World Health Organization (WHO) standards were applied to define sites with drinking water permissible levels. Information was loaded in an ArcGIS software and analyzed with a Spatial Analyst extension using Inverse Spline interpolation methods. Fluoride content in most samples has values as high as 1.97 mg/L, with 53% of the samples showing fluoride concentration higher than the level suggested by the WHO for drinking water of 1.5 mg/L and ratified by the National Society of Exploitation and Drinking Potable Water of Tunisia. Additionally, reported nitrate concentrations are higher than the expected groundwater background level of 10 mg/L; indeed, values are up to 286 mg/L, being hazardous for domestic use and suggesting the presence of anthropogenic sources of water contamination. The Land Use and Land Cover (LULCC) of Bouficha aquifer were changed over seventeen years. The Landsat satellite images have shown that the built-up area increased from 2001 to 2018 to the detriment of water and crop vegetation. The overuse of fertilizers on a total agricultural area of Bouficha aquifer (60%) led to significant pollutants, including nitrate and a deterioration in its water quality. Regarding the WHO and the Tunisian drinking water guidelines, this work provides substantial evidence that groundwater quality is posing a significant health threat for residents. Similarly, results show groundwater’s chemical content is also unsuitable for economic activities in the Bouficha region, mainly hazardous for irrigation purposes.

Upper Cretaceous Abiod and El Haria Formations in Jebel Rhorfa (Grombalia area, northeastern Tunisia): lithology and biostratigraphy revised—with extended comments on Ahlem Amri, Moez Ben Fadhel, Asma Chermiti, and Mohamed Ben Youssef (2018)

In the present work, we comment on Amri et al. Arab J Geosci 11(253) (2018) publication. This latter contains many taxonomic misinterpretations and confusions. That is why, in the present work, we propose accuracy on the chronostratigraphy of the Abiod Formation. So, we demonstrate that this Formation remains in the Late Cretaceous in age as originally defined by its author, Burollet Ann Mines Geol 18:388 (1956), and widely accepted by other geologists working on Cretaceous and Paleogene series in the Grombalia area as well as elsewhere in northern and central Tunisia. It cannot be Paleocene in age indeed. We discuss also much incoherence both in the text and illustrations (figures and plates) provided by Amri et al. Arab J Geosci 11(253) (2018). In order to correct their taxonomic misinterpretation, we use the main characters allowing the distinction of globotruncanids from morozovellids and globigerinids. We also describe Rh section in Jebel Rhorfa from the Grombalia area and we plot the genuine respective range of foraminiferal species. Consequently, we demonstrate that the Abiod Formation is rich in globotruncanids including Upper Cretaceous species belonging to genera Globotruncana, Globotruncanita, Globotruncanella, Radotruncana, and Rugoglobigerina. This formation is well and truly devoid of morozovellids and globigerinids indicative of Paleocene. Hence, no possible reworked Paleocene fauna exists and their proposed scenario with an assumed reworking can be no longer defensible.

Groundwater monitoring for assessing artificial recharge in the Mediterranean coastal aquifer of Korba (Northeastern Tunisia).

Groundwater (GW) artificial recharge with treated wastewater (TWW) is seen as a promising technical solution to overcome groundwater overexploitation and seawater intrusion and to ascertain future water resources availability. While these introduced recharge systems have shown positive impacts in many areas across the world, their effective contribution to GW recharge is still not well quantified in water-stressed regions such as Tunisia. The scarcity of on-site data with accurate temporal and spatial measurements and resolution in such areas hinders the clear assessment of these recharge systems' performances. This article presents an approach based on the on-site monitoring of groundwater level and salinity measurements and recharge rate records spanning over the 6-year period to investigate the performances of a wastewater-based recharge system located in the Korba-El Mida site in Tunisia. The analysis showed that the artificial recharge did not have an impact on groundwater level. Controversially, a decrease in water salinity in and around the study site was observed. Findings emphasize on the weak wastewater volumes applied to the recharge system and the clogging phenomena that occurred in the pool and in the vadose zone. Furthermore, analyzing the information over a short period of time could be misleading as the results of a 6-year period of monitoring show clearly that the way the site was managed and the local conditions have a role in understanding and interpreting the results even if the artificial recharge was appropriately designed.

Impact of temperature and growth phases on lipid composition and fatty acid profile of a thermophilic Bacillariophyta strain related to the genus Halamphora from north-eastern Tunisia

AbstractA thermo-tolerant diatom species has been isolated from Tunisian hot spring water (40°C). The isolated diatom has been molecularly identified and classified into the genus Halamphora. The growth kinetics, lipid content and distribution of fatty acids were assessed at 20 and 30°C temperature levels and constant irradiance in controlled batch cultures (11 days). Halamphora sp. showed better growth (μ = 0.53 day−1) and a higher lipid yield (25% of the dry weight) at a higher temperature (30°C). Under the two temperatures tested, the highest lipid and fatty acid contents were mainly reached during the stationary growth phase. The fatty acid profile showed a significant content of two essential fatty acids, eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (AA, 20:4n-6), reaching ~15% and ~21% of the total fatty acids, respectively, at 20°C and 30°C. The distribution of the different components of the fatty acids showed that EPA and AA were mainly located in the neutral lipid fraction in the stationary phase.

Hydrogeochemistry and evaluation of groundwater suitability for irrigation purpose in the Mornag region, northeastern Tunisia

In semiarid regions, salinization and anthropogenic contaminants are considered as the principal threat to groundwater resource availability. Consequently, the origin and processes of salinization should be identified, to take a sustainable measurement to mitigate these problems. In the present study, groundwater samples from 18 dug wells were collected during the sampling campaign carried out in May 2016 in order to identify the main natural and anthropogenic processes that control the quality of groundwater in the Mornag shallow aquifer (northeastern Tunisia) and to evaluate its suitability for agricultural irrigation purpose. This may create a clear database for decision maker to take suitable actions to sustainably manage the groundwater resources. The hydrogeochemical parameters (major ions concentration, pH, TDS, EC) were examined to assess the quality of groundwater and to identify the main mineralization processes. Permeability index (PI), percentage of sodium (%Na) and the ratio of sodium adsorption (SAR) were investigated to evaluate the groundwater suitability for irrigation. It has been demonstrated that the major ions abundance follows the order of sodium > calcium > magnesium > potassium and chloride > sulfate > bicarbonate > nitrate. Dissolution of evaporite minerals, such as halite, gypsum and anhydrite, and reverse ion exchange are the predominant processes of groundwater mineralization, generating the Cl–SO4–Ca and Na–Cl major water types. The calculated irrigation water quality index displayed that 55% of the Mornag groundwater samples are distinguished by elevated SAR and PI, suggesting their unsuitability for irrigation. So, the present study has provided a precious insight into the major geochemical processes occurring in the Mornag shallow groundwater and their suitability for irrigation which will support future management of these resources.

Using geochemical and isotopic tracers to characterize groundwater dynamics and salinity sources in the Wadi Guenniche coastal plain in northern Tunisia

Northeastern Tunisia is a sub-humid region with annual rainfall ranging from 600 to 650 mm. Unconfined groundwater in this area is easily accessible and represents an important perennial water source for agricultural activities. The present study deals with a multi-parameter investigation of one of the most important basins in northeastern Tunisia: the Wadi Guenniche plain (130 km2). Hydrochemical (major elements and Br−) and isotopic (18O, 2H and 3H) investigations were carried out on 32 shallow wells to gain insights into groundwater recharge and salinity. The dominant water types were Ca–Mg/Cl–SO4 and Na/Cl with electric conductivity values varying between 0.86 and 6.6 mS/cm. Based on ion ratios and saturation indexes, groundwater salinity originated from weathering of carbonate and evaporite minerals and cation-exchange with clays. Additional influence of anthropogenic activities shown by high NO3− concentrations exceeding 100 mg/L was identified in different parts of the plain resulting from irrigation return flow. A six-year record of 18O and 2H signatures of daily rainwater (n = 293) enabled to define a Local Meteoric Water Line for the Bizerte area (δ2H = 7.02 δ18O + 8.27). The isotopic signature of groundwater was very similar to that of the mean annual rainfall in Bizerte suggesting direct recharge of the aquifer. Tritium levels in sampled wells were relatively high and indicated recent recharge and short residence time. Annual recharge of 100 mm was estimated using a mixing model based on 3H contents in precipitation and groundwater.

Enhanced Characterization of Water Resource Potential in Zaghouan Region, Northeast Tunisia

This study presents a range of approaches to achieve enhanced characterization of the Zaghouan aquifer system (northeastern Tunisia). Existing water borehole data were analyzed to identify the different reservoir formations, while satellite imagery is analyzed to determinate the superficial lineaments affecting these formations. To define the deep structures determining the geometry of the Zaghouan aquifer system, lithostratigraphic correlations were constructed and analyzed supported by both quantitative and qualitative assessment of gravity measurements. The available lithological columns and their corresponding well logs reveal different carbonate and detritic reservoirs. The carbonate reservoirs consist of Jurassic, Cretaceous and Eocene limestones, whereas the detritic ones are composed of Oligo–Miocene sandstones and Plio-Quaternary to Quaternary sands and gravels. The structural map obtained from processing the satellite imagery confirms several lineaments drawn on the geological map, such as the Zaghouan fault, but also reveals new ones hitherto unrecognized. The intersections of the detected lineaments explain the occurrence of many springs in the area offering potentially favorable opportunities for accessing water resources in fractured aquifers. Analysis of lithostratigraphic correlations shows notable variations in the thickness, depth and composition of reservoir formations. Gravity data interpretation gives more precision by highlighting buried structures and discontinuities with different directions and depths. The delineated tectonic features demonstrate an aquifer system compartmentalized in raised and subsided blocks. The raised compartments may constitute continental divide areas and preferential aquifer recharge zones, while the sunken ones contain a multilayer aquifer composed of Quaternary and Pliocene reservoirs overlying multiple permeable layers, Tertiary and/or Mesozoic in age.

Assessing Aquifer Water Level and Salinity for a Managed Artificial Recharge Site Using Reclaimed Water

This study was carried out to examine the impact of an artificial recharge site on groundwater level and salinity using treated domestic wastewater for the Korba aquifer (north eastern Tunisia). The site is located in a semi-arid region affected by seawater intrusion, inducing an increase in groundwater salinity. Investigation of the subsurface enabled the identification of suitable areas for aquifer recharge mainly composed of sand formations. Groundwater flow and solute transport models (MODFLOW and MT3DMS) were then setup and calibrated for steady and transient states from 1971 to 2005 and used to assess the impact of the artificial recharge site. Results showed that artificial recharge, with a rate of 1500 m3/day and a salinity of 3.3 g/L, could produce a recovery in groundwater level by up to 2.7 m and a reduction in groundwater salinity by as much as 5.7 g/L over an extended simulation period. Groundwater monitoring for 2007–2014, used for model validation, allowed one to confirm that the effective recharge, reaching the water table, is less than the planned values.

Discovery of late Tortonian incised valleys in the Saouaf Formation (northeastern Tunisia) - Evidence of high-frequency sea-level variations in the central Mediterranean

During the late Miocene, the connection between the Atlantic Ocean and the Mediterranean Sea was progressively restricted. Despite many discoveries of Messinian incised valleys and canyons in the peri-Mediterranean basins, the Tortonian incised valleys are poorly described. The Tortonian series exposed in the northeastern end of the Cap Bon peninsula (northeastern Tunisia, central Mediterranean) provide an excellent example of complex and extensive incised valleys system traceable for up to 5 km (entire length of the outcrop). Detailed facies and sedimentological analysis permitted the recognition of five distinct phases of incision. These valleys (approximately 300 m wide and 10 m to 30 m deep) were incised during sea-level fall and were filled during subsequent sea-level rise. These valleys are characterized by the lack of fluvial deposits at their bases. During sea-level rise, these valleys were filled mainly with cross-bedded estuarine sandstone forming multistorey channels and point-bar deposits. Tidal sand flat deposits are locally well developed at the margins of the valleys fills. These tide-dominated estuarine deposits, corresponding to the transgressive systems tracts, are arranged into fining-upward retrogradationnal parasequences. The highstand systems tracts correspond to wave-dominated deltaic deposits comprising offshore, offshore-transition and shoreface deposits. These successions are typically arranged in thickening and coarsening-upward parasequences. The upper surfaces of the highstand systems tracts are incised by later valleys. The formation and the filling of these valleys record the complex interplay of different allocyclic factors: (1) tectonic uplift due to the major compressive Atlassic phase, (2) high-frequency sea-level variations, (3) warm and humid climate, and (4) high river sediment input. The results of this study provide important data, such as incised valleys geometries, dimension, extension and connectivity. The results of this study emphasis the potential link between high-frequency sea-level variation and progressive restriction of the Mediterranean during the late Tortonian.

Tree growth and leaf gas exchange variability of three Mediterranean Pinus spp. growing in a common garden in Northeastern Tunisia

A dendrochronological approach and gas exchange techniques were used to study the adaptation of Pinus halepensis, Pinus pinea, and Pinus brutia growing in a 47-year-old common garden experiment to the local subhumid climate in Northeastern Tunisia. P. pinea showed the highest survival rate, the greatest height, the widest diameter at breast height, and the largest specific leaf area. The lowest values were recorded for P. halepensis. Ring width data showed that P. pinea had the highest radial growth, which was correlated to the lowest mean sensitivity and the first-order autocorrelation coefficient. The highest values of the abovementioned parameters were recorded for P. halepensis. CO2 response curves of net leaf photosynthesis were used to directly calculate the main photosynthetic parameters, including the CO2-saturated net photosynthesis rate, stomatal limitation, and carboxylation efficiency. At the natural ambient CO2 concentration, P. brutia presented the lowest net photosynthesis, P. pinea exhibited the highest water-use efficiency, and the highest stomatal conductance was recorded for P. halepensis. Furthermore, at a high concentration of CO2, the highest stomatal limitation was recorded for P. brutia, which may partially explain why it presented the lowest net CO2-saturated photosynthesis rate; the highest net CO2-saturated photosynthesis rate was observed for P. halepensis. The response of the growth pattern to the climate was found to depend on the species. P. pinea showed the highest radial growth and water-use efficiency, implying that this species is the best suited of the three species investigated to the pedoclimatic conditions in the studied area.

An experimental study of selected Jurassic carbonate samples from north-eastern Tunisia

The industrial development of the outcrops in the Tunis-Zaghouane area could represent an important economic driver for the country. The main structures are introduced and illustrated with onsite field observations. Moreover, samples which were extracted from the selected regions and are characterized based on measurements of porosity, water absorption and abrasion loss coefficients. The experimental results showed a negligible variation of densities, demonstrated a linear correlation between connected porosity and overall water absorption. In addition, experimental result confirms that outcrops from Jebel Zaghouane, Jebel Hammam Zriba and Jebel Hammam Jedidi could be developed as construction materials.

Migratory behavior of free-living marine nematodes surrounded by sediments experimentally contaminated by mixtures of polycyclic aromatic hydrocarbons

An experiment was conducted using microcosms with connected sedimentary compartments to assess the effects of three polycyclic aromatic hydrocarbons (PAHs) on free-living marine nematodes from Bizerte Bay (northeastern Tunisia). Over 30 days, the nematofauna were exposed to four treatment sediments, including one with chrysene (150 ppb), chrysene (150 ppb) plus fluoranthene (75 ppb), chrysene (150 ppb) and phenanthrene (15 ppb), and an uncontaminated reference. Numerical and qualitative community simplifications occurred in contaminated sediments relative to the reference. The diversity of nematodes differed based on hydrocarbon combinations. Multivariate analyses revealed communities in contaminated compartments differed from those in the initial natural sediment and reference. Differences in sensitivities of nematodes to hydrocarbons and in migratory abilities occurred. Rhabditis sp., Calamicrolaimus honestus, and Oncholaimus campylocercoides were in all compartments and classified as tolerant to PAHs. Nematodes observed only in control compartments, including Parasphaerolaimus paradoxus, Encheliidae (sp.), Trichotheristus mirabilis, and Theristus pertenuis were considered sensitive.

Sedimentology and high-frequency cycles of the late Pleistocene of the Bizerte area (N-E Tunisia)

Quaternary deposits are well known around the Mediterranean basin especially those exposed along the Tunisia Coast. This work focuses on the Pleistocene deposits outcropping along the Bizerte littoral (Northeastern Tunisia) with special attention to coastal deposits and their evolution during the late Pleistocene. The sedimentologic analysis carried on four cross-sections exhibits a complete Quaternary series that begin with basal erosive surface and marine deposits attributed to the last interglacial period. The Pleistocene deposits represent a 3rd-order sequence that is divided into 2 (4th–5th order) shallowing-upward sequences that are interpreted as a response to glacio-eustatic events. The lower sequence consists mainly of shoreface facies which evolve to foreshore and continental facies. The upper sequence shows a dune facies with cross-stratification and continental gastropods (eolian deposit interbedded with red to gray paleosoils). Those eolian deposits and paleosoils levels are related to the highstand system track of the 3rd-order sequence.

A GIS-based tool for automatic extraction of drainage anomalies. A case study of enfidha (North-East of Tunisia)

It is particularly useful to analyze drainage anomalies for morphostructural interpretation of low relief areas. In basins and sub-basins, these anomalies may be due to local changes resulting from lithological discontinuities or tectonic activity caused by subsidence or uplift. Indeed, drainage anomalies are the most revealing geomorphological evidence of active faults. We present a new method to extract the drainage anomalies in watershed. The adapted methodology is therefore based on the drainage anomalies extraction in the Enfidha plain, indicating that the area is potentially tectonically active. Our objective in this article is to develop an automatic extraction tool, using the model builder technique in the ArcGIS environment, to extract drainage anomalies. To use this tool, a Digital Elevation Model (DEM) and drainage networks are required. In order to obtain the desired results, several tools are used: filtering of the DEM, generation of the summit surface, extraction of the slope orientation, calculation of the stream direction, etc. Based on the Automatic Drainage Anomalies Extraction Tool (ADAET), the relationship between drainage anomalies and tectonics was studied in the Enfidha sector of north-eastern Tunisia. The sub-watershed selected for this study is drained by numerous rivers and occupies the northeastern part of the Enfidha plain. This plain is known for its relatively high seismicity. Therefore, the method of automatic extraction of drainage anomalies in a GIS environment based on a global DEM (SRTM), detailed in this paper, appears very promising and can be of great utility in morpho-structural and morpho-neotectonic studies. This method allows to discover a high concentration of drainage anomalies on the Oued El Boul river and in the plain. Correlation with existing tectonic models shows that parts of the selected drains are located near the subsurface fault. Therefore, the drainage anomalies prove the existence of neotectonic deformation in the terrain. The activity of this fault has been proven by several authors. In this region, the extraction of drainage anomalies is most often used and reflects neotectonic activities.

Morphological characteristics and variation of wood, cone and seed productions in the reforestation of Aleppo pine in Northeastern Tunisia using terrestrial and spatial index approaches

Abstract For several decades, forest management policies have encouraged land cover changes, with the establishment of tree cover such as Aleppo pine in natural or degraded ecosystems for soil protection and the firewood production. In order to investigate the importance of Aleppo pine trees in the ecosystem, this study was conducted in the reforestation of the Aleppo pine of Northeastern Tunisia. The production of wood, cones and seeds of Aleppo pine in the 6 date reforestation in Northeastern Tunisia were surveyed using 6 plots (20 tree/plot) spread over 6 different location. Our hypothesis was to determine the characteristics that can be decisive in estimating the production of Aleppo pine in reforestation in Tunisia using terrestrial and spatial measurements including (i) age, (ii) dendrometric characteristics, (iii) silvicultural treatments, (iv) stationary data and/ or (v) remote sensing parameter (NDVI: Normalized Difference Vegetation Index). We found that the Aleppo pine in Northeastern Tunisia and at young age trees (14–35 years) were more productive than the regeneration or reforestation stand, either young or old, in Northwest of Tunisia. Wood, cone and seed productions were significantly different amongst the plots (p <0.05). The NDVI was positively correlated with the production of wood, cones and seeds. Stand age, exposure and longitude were also positively correlated with the production. However, longitude and altitude were negatively correlated with the production, showing a negative effect on the morphological traits of trees and, subsequently, their growth. The regression analysis indicates that NDVI and age were the most determinant factors of seed production. This research suggests that reforestation planning, particularly the choice of altitude and latitude, may result in improved tree morphology that may increase Aleppo pine wood seed and cone crops.