Hédi Zouari

Synsedimentary folding process and transtensive tectonic during Late Miocene to Quaternary in northeastern Tunisia: case of Mateur–Menzel Bourguiba region

The following paper presents an integrated approach of field observations and surface and subsurface data to precisely determine the geodynamic evolution during the Late Miocene of Mateur and Menzel Bourguiba region (northeastern Tunisia). Alternation between compressive and transtensive regime has been generated as a consequence of relative bringing of Africa and Eurasia plates. The first compressive regime controlled the Late Miocene M1 which edified folds and reverse faults. The second one during Late Miocene M2 was transtensive and remobilized E–W right lateral strike slip deep faults which generated the eastern Mateur distensional zone as a NW–SE releasing bend. The last compressive phase during Messinian and Pliocene–Early Quaternary has reactivated the E–W deep faults as right lateral strike slip movement with reverse component, the NE–SW faults were acted with reverse movement and the folding was accentuated. In this study, no deformation is observed affecting Middle Quaternary–actual series, but the compressive regime continues until the present according to the evidence existing in other regions of Tunisia.

Structural cutting of a region showing various compound tectonic deformations (example of Bouficha–Grombalia region)

Bouficha–Grombalia region shows complex tectonic deformations and is affected by faults and folds of different geometry. A structural study has allowed to determine that Bouficha–Grombalia region is affected by significant faults of EW, NE-SW and NW-SE directions. These faults divide Bouficha–Grombalia region into several compartments. We distinguish three important structures whose first is in the SW which corresponds to Zaghouan–Bouficha trough. The second structure is situated in the NE, which corresponds to the Grombalia trough. The third structure occupies a central position; it consists in the Bouficha–Grombalia high structure. The last structure is composed by three blocks. Each block is characterised by particular folds geometry. These structures were outlined at least from middle Miocene, and they have undergone the effect of subsequent compressive tectonic events which have led to folds building above or counter the pre-existing NE-SW faults.

Surface soil clay content mapping at large scales using multispectral (VNIR–SWIR) ASTER data

ABSTRACT The potential of Visible Near-Infrared and Short-Wave Infrared (VNIR–SWIR, 400 nm–2500 nm) hyperspectral imagery for use in multivariate approaches and geostatistical techniques for mapping topsoil properties has been previously demonstrated. However, the use of VNIR–SWIR hyperspectral imagery remains costly, which limits the spatial scales over which it can be applied. This paper aims to evaluate the potential for substituting the more accessible Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) VNIR–SWIR multispectral data for hyperspectral imagery in mapping surface soil clay contents. This study used ASTER multispectral data (nine bands in the VNIR–SWIR spectral domain) acquired over the Cap-Bon region in Tunisia (2000 km2) and 262 surface soil samples collected within the ASTER scene that were subjected to laboratory analysis of the clay fraction (soil particles less than 2 µm). The approach followed two steps: i) estimation of surface soil clay contents for bare soil areas using a Multiple Linear Regression (MLR) model built from the 9 ASTER VNIR–SWIR bands and ii) spatial interpolation (co-kriging) of the soil sampling of measured points and the ASTER-estimates over the whole study area. The MLR model for estimating clay contents using ASTER multispectral data performed correctly ( = 0.60). In addition, this performance is only slightly lower than that obtained using hyperspectral imagery (specifically, an Airborne Imaging Spectrometer for Applications (AISA-DUAL) dual hyperspectral sensor) in a previous study. Moreover, the co-kriging process appeared to yield encouraging results for capturing the large range of variability of clay content values, although it was not able to represent the short scale variability ( = 0.43). Finally, the ASTER multispectral data, despite being underused in the mapping of soil properties, may open up new ways to perform more extensive mapping of surface soil properties in semi-arid contexts characterized by extensive bare and dry soil surfaces.