Forty-four rock samples from the Landana section, belonging to the historical Dartevelle collection of the Royal Museum for Central Africa (RMCA) at Tervuren, Belgium, were palynologically processed and analysed. Systematic analysis of the samples from the Landana sea cliff locality has revealed 90 dinoflagellate cyst taxa spanning an interval that ranges at least from the middle Paleocene to the late Eocene/early Oligocene. This locality represents the first extensive sub-equatorial African Paleogene dinoflagellate cyst record. Dinoflagellate cyst occurrences were calibrated and evaluated against newly revised foraminiferal ranges. This novel dinoflagellate cyst biostratigraphic record was compared and correlated with contemporaneous records relatively close by in the Gulf of Guinea, as well as with records from more distant locations such as Antarctica, Australia and New Zealand. A preliminary dinoflagellate cyst zonation is here proposed comprising three zones and five unzoned yet otherwise distinct intervals. The lower part of the Landana section records a large portion of the early to middle/ late Selandian, which is made apparent by the presence of taxa such as Isabelidinium cingulatum, Isabelidinium? viborgense, and Spinidinium densispinatum. The Thanetian through Lutetian part of the section is more fragmentary and is devoid of any significant marker taxa normally typical for this time interval elsewhere. The upper part of the record is largely devoid of dinoflagellate cysts, with the few dinoflagellate cyst-bearing samples pointing to an Eocene to early Oligocene age. Dinoflagellate cyst assemblages are relatively variable and often largely dominated by a single particular taxon or complex. We record remarkably abundant peridinioid cysts signalling high palaeoproductivity for protracted periods of time, resulting from either heightened terrestrial influence or enhanced upwelling.
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RBINS Staff Publications 2018
The Grote Brogel Fault (GBF) is a major WNW-ESE striking normal fault in Belgium that diverges westward from the NW-SE striking western border fault system of the Roer Valley Graben. The GBF delimits the topographically higher Campine Block from the subsiding Roer Valley Graben, and is expressed in the Digital Terrain Model (DTM) by relief gradients or scarps. By integrating DTM, Electrical Resistivity Tomography (ERT), Cone Penetration Test (CPT) and borehole data, we studied the Quaternary activity of the GBF and its effects on local hydrogeology. In the shallow subsurface (< 50 m) underneath these scarps, fault splays of the GBF were interpreted on newly acquired ERT profiles at two investigation sites: one on the eastern section and the other on the western section, near the limit of the visible surface trace of the fault. Borehole and CPT data enabled stratigraphic interpretations of the ERT profiles and thereby allowed measuring vertical fault offsets at the base of Pleistocene fluvial deposits of up to 12 m. Groundwater measurements in the boreholes and CPTs indicate that the GBF acts as a hydrologic boundary that prevents groundwater flow from the elevated footwall towards the hangingwall, resulting in hydraulic head differences of up to 12.7 m. For the two investigation sites, the hydraulic head changes correlate with the relief gradient, which in turn correlates with the Quaternary vertical offset of the GBF. ERT profiles at the eastern site also revealed a local soft-linked stepover in the shallow subsurface, which affects groundwater levels in the different fault blocks, and illustrates the complex small-scale geometry of the GBF.
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