Abstract Following our fieldwork in Paleogene deposits of Togo, we herein report cranial as well ... more Abstract Following our fieldwork in Paleogene deposits of Togo, we herein report cranial as well as postcranial elements belonging to the family Dyrosauridae. This assemblage is dated to the Late Paleocene (Thanetian) from two quarries in southern Togo. The specimens include a partial skull presenting two large supratemporal fossae and a massive occipital condyle; long and slender isolated teeth; amphicoelous vertebrae including several articulated ones; and two osteoderms devoid of carina. The morphology of the partial skull reveals similarities with some African longirostrine forms such as Rhabdognathus spp., although this attribution cannot be confirmed. Longirostrine forms, known in the late Paleocene and early Eocene of the Iullemmeden basin (Nigeria, Niger, Mali, Algeria) and in the phosphates of Morocco and Tunisia, is only represented in Thanetian levels in Togo. Different palaeoenvironmental settings seem to have characterized the various African basins during the lower Eocene, with consequences for the geographic distribution of dyrosaurids. These dyrosaurid remains confirm the presence of the family in Togo during the Paleocene and underline the fossiliferous potential of the coastal sedimentary basin in Togo and in the bay of Benin.
Lithological and micropaleontological studies of core-samples from five boreholes drilled in the ... more Lithological and micropaleontological studies of core-samples from five boreholes drilled in the northeastern part of the coastal basin of Togo allow for a specification of the stratigraphy and the paleogeography of this area during the Maastrichtian and Paleogene. A lithological analysis reveals a marine series consisting of a Lower Maastrichtian unit, a Middle Paleocene to Eocene unit, and an upper
ABSTRACT The present paper is an overview of tropical West Africa soils with the aim to compile s... more ABSTRACT The present paper is an overview of tropical West Africa soils with the aim to compile soil characteristics and identify research gaps in respect to rates of soil forming processes. Compilation of morphological, mineralogical and chemical data on soil development has distinguished several types of soils. The major soils identified and described include ferrallitic soils, ferruginous tropical soils, vertisols, semi-arid tropical soils, and hydromorphic soils. Their formation and their evolution depend on climate and paleoclimate actions, parent materials, vegetation, and geomorphology. Most of these soils have been mapped using FAO, CPS classification, and Worldwide Reference Base (WRB). Some aspects of the pedogenesis process are also discussed. Three new methods of investigation used by researchers: Potassium–argon, gold mineralogy, and cosmogenic beryllium-10 allow dating chemical and weathering processes and also led to a quantification of geochemical and mechanical processes in this area. The modern climate has an impact on soils. All these types of soils are experiencing secondary pedogenic processes such as rejuvenation, and especially reworking to some extent by water or wind erosion, giving rise to younger soils. Rapid disturbance through reworking leads to induration and armouring. Soil dating data in this area are very scarce. Some approaches (e.g. mass balance, relative chronology, chronostratigraphic, archaeological, luminescence, paleobiological, radiocarbon, OSL, and termite activity) have been implemented to assess the time factors of soil formation. Finally, this work highlights some gaps about soil research, particularly the need to define soil parameters which can be related to soil age.
Abstract Following our fieldwork in Paleogene deposits of Togo, we herein report cranial as well ... more Abstract Following our fieldwork in Paleogene deposits of Togo, we herein report cranial as well as postcranial elements belonging to the family Dyrosauridae. This assemblage is dated to the Late Paleocene (Thanetian) from two quarries in southern Togo. The specimens include a partial skull presenting two large supratemporal fossae and a massive occipital condyle; long and slender isolated teeth; amphicoelous vertebrae including several articulated ones; and two osteoderms devoid of carina. The morphology of the partial skull reveals similarities with some African longirostrine forms such as Rhabdognathus spp., although this attribution cannot be confirmed. Longirostrine forms, known in the late Paleocene and early Eocene of the Iullemmeden basin (Nigeria, Niger, Mali, Algeria) and in the phosphates of Morocco and Tunisia, is only represented in Thanetian levels in Togo. Different palaeoenvironmental settings seem to have characterized the various African basins during the lower Eocene, with consequences for the geographic distribution of dyrosaurids. These dyrosaurid remains confirm the presence of the family in Togo during the Paleocene and underline the fossiliferous potential of the coastal sedimentary basin in Togo and in the bay of Benin.
Lithological and micropaleontological studies of core-samples from five boreholes drilled in the ... more Lithological and micropaleontological studies of core-samples from five boreholes drilled in the northeastern part of the coastal basin of Togo allow for a specification of the stratigraphy and the paleogeography of this area during the Maastrichtian and Paleogene. A lithological analysis reveals a marine series consisting of a Lower Maastrichtian unit, a Middle Paleocene to Eocene unit, and an upper
ABSTRACT The present paper is an overview of tropical West Africa soils with the aim to compile s... more ABSTRACT The present paper is an overview of tropical West Africa soils with the aim to compile soil characteristics and identify research gaps in respect to rates of soil forming processes. Compilation of morphological, mineralogical and chemical data on soil development has distinguished several types of soils. The major soils identified and described include ferrallitic soils, ferruginous tropical soils, vertisols, semi-arid tropical soils, and hydromorphic soils. Their formation and their evolution depend on climate and paleoclimate actions, parent materials, vegetation, and geomorphology. Most of these soils have been mapped using FAO, CPS classification, and Worldwide Reference Base (WRB). Some aspects of the pedogenesis process are also discussed. Three new methods of investigation used by researchers: Potassium–argon, gold mineralogy, and cosmogenic beryllium-10 allow dating chemical and weathering processes and also led to a quantification of geochemical and mechanical processes in this area. The modern climate has an impact on soils. All these types of soils are experiencing secondary pedogenic processes such as rejuvenation, and especially reworking to some extent by water or wind erosion, giving rise to younger soils. Rapid disturbance through reworking leads to induration and armouring. Soil dating data in this area are very scarce. Some approaches (e.g. mass balance, relative chronology, chronostratigraphic, archaeological, luminescence, paleobiological, radiocarbon, OSL, and termite activity) have been implemented to assess the time factors of soil formation. Finally, this work highlights some gaps about soil research, particularly the need to define soil parameters which can be related to soil age.
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Papers by Pauline Da Costa