Late Pleistocene Boulaaba travertine and calcareous tufa, Kasserine, Central Tunisia: Implications for North African spring-fed Ca-carbonates

Abstract

Late Pleistocene (≈21000 BP) travertine and calcareous tufa deposits have been recognized in the region of Boulaaba, Kasserine in Central Tunisia with a variety of morphological aspects and depositional facies. Morphological aspects of these deposits consist of two elongated continental Ca-carbonate masses defined as fissure-ridges built-up around old fissure networks. Distinction between travertine and tufa lithofacies, based on textural, compositional and topographic settings regarding the entire carbonate masses, have led for travertine to 5 lithofacies: (1) banded travertine fissure infill, (2) bacterial shrubs, (3) stromatolitic laminae, (4) pisoids and (5) speleothem-like travertine growth habits. Tufa is composed of autochtonous tufa lithofacies with (1) phytoherme framestone tufa, (2) calcified insect larval constructions, and clastic alllochtonous tufa lithofacies with (1) matrix-supported microdetrital tufa and (2) grain-supported macrodetrital phytoclast tufa. Both lithofacies show variable diagenetic evolutions with an overall lithification. These deposits are concentrated along the Foussana trough-related normal faults and fractures that belong to the extensional regime of the major strike slip fault of Kasserine that enhanced and facilitated fluid upwelling along with movements of faults which damage and fracture the rocks and increase the overall permeability. During this phase (Late Pleistocene), the deposition of Boulaaba travertine and tufa has implied some paleo-hydroclimatic conditions marked in most North African travertine and tufa depositing sites by (1) a higher water table with abundant effective rainfall on the recharge areas, (2) dense plant cover and soils giving acidic water infiltrations, (3) karstic dissolution of Cretaceous limestones (especially the limestone aquifers of Bireno and Abiod), and (4) a strong water mineralization of the groundwater.