A GEOCHEMICAL RECORD OF LATE CENOZOIC SEDIMENTATION HISTORY IN THE SOUTHERN NETHERLANDS

A sediment-geochemical study was performed on unconsolidated Upper Cen ozoic siliclastic sediments from an area in the south of the Netherlan ds. Glauconite-rich sediments (Breda Fm) show high K contents and low Ba/K ratios. Major shifts in sediment composition as a result of chang es in the Rhine system and of shifts between Rhine and Scheldt provena nce, as known from heavy-mineral studies, are also recorded in changes in the grain-size-dependent variations between Al, Na and K. Pleistoc ene Rhine sediments (Tegelen Fm) show higher Na contents than Pliocene Rhine sediments (Oosterhout and Kiezelooliet Fms) and Scheldt-derived material (Kedichem Fm), probably as a result of larger contents of so dic plagioclase. Scheldt-derived sediments show low K/Al ratios as a r esult of a smectite-dominated clay-mineralogical composition and low c ontents of micas, whereas Rhine-derived sediments have high K/Al ratio s which reflect an illite-kaolinite-dominated clay mineralogy and high er contents of muscovite. The presence of siderite causes high Fe cont ents in the Tegelen Fm in the east of the area, suggesting a freshwate r depositional environment. Increased Mg contents in the siderite-bear ing sections of the Tegelen Fm and in parts of the Oosterhout and Kiez elooliet Fms are probably caused by the presence of minor amounts of d olomite. Localized high concentrations of (pyrite-) S are not only fou nd in the marine Oosterhout Fm and the estuarine Tegelen Fm, but also in the fluviatile Kiezelooliet and Kedichem Fms, which indicates at le ast minor marine transgressions during their deposition.