The main geochemical features of this zone were the high content of terrigenous silica (88%) and large Mg/Ca, Na/K and Fe/Mn ratios. We examined three

sediment cores taken from Tromper Wiek (Figure 1). All were characterized by a similar lithology and geochemical composition. The shallowest (core 233230) was taken at a depth of 28.7 m b.s.l. (Figure 5). The sediments could be divided into two zones (Figure 6). The lower zone (E; 132–423 cm) MS 275 contained olive-grey silt with fine humus particles in the lower portion, and fine sand with plant remains in the upper portion. The sediment of zone E had the highest content of terrigenous silica (97%) and a low content of biogenic silica (2%), loss on ignition (2%) and ratios of Mg/Ca

(0.2), and Fe/Mn (40). The Na/K ratio was less than 1. The upper zone (F; 0–132 cm) consisted of olive-grey mud with some shell remains. It was indistinctly laminated below 96 cm and slightly darker and sandy below 127 cm. The base of zone F had the lowest content of terrigenous silica (70%), which gradually increased in the upper portion of the core. This zone had a higher content of biogenic silica (7.3%) than zone E, a higher loss on ignition (7.4%) and greater ratios of Mg/Ca (0.8), Na/K (1.5) and Fe/Mn (100). Core 233240 was taken at a depth of 29.5 m b.s.l., 2 km north-west of core 233230 (Figures 1, 5). The sediments of this core were divided Antiinfection Compound Library datasheet into the same two zones as in core 233230 (Figure 6). The lower Selleckchem Atezolizumab zone (E; 132–328 cm) consisted of fine, pale-olive sand with a thin silty layer at 160 cm and olive-grey silt with a 1 cm layer of peat gyttja at 141 cm. The geochemical composition of zone E had the highest content in the core of terrigenous

silica (96%) and low biogenic silica content (1%), loss on ignition (1.5%) and ratios of Mg/Ca (0.1) and Fe/Mn (55). The Na/K ratio increased gradually to a value of 2 in the upper levels of zone E. The upper zone (F; 0–132 cm) consisted of fine, olive-grey sandy mud with a large broken Arctica shell at 119 cm. The geochemical composition of this zone had the lowest content of terrigenous silica (70%) in the core and a higher contribution of biogenic silica (5.5%), loss on ignition (6%) and ratios of Mg/Ca (0.7), Na/K (1.5) and Fe/Mn (120). The deepest core from Tromper Wiek (core 233250) was taken at a depth of 30.7 m b.s.l., 10 km north-west of core 233240 (Figures 1, 5). This core consisted of two sediment zones (Figure 6). The lower zone (E; 233–431 cm) consisted of fine, dark-grey sand with a downward decreasing number of humus particles. The main features of the geochemical composition were the high content of terrigenous silica (99%), and the low biogenic silica content (1%), low loss on ignition (1.5%) and low ratios of Mg/Ca (0.2) and Fe/Mn (50). The Na/K ratio exhibited poor variability along the core.