GEOCHEMICAL RECORDS OF SEDIMENTS IN THE EASTERN GOTLAND BASIN - PRODUCTS OF SEDIMENT DYNAMICS IN A NOT-SO-STAGNANT ANOXIC BASIN

Geochemical data from 4 cores taken in the Eastern Gotland Basin of th e Central Baltic Sea (68 to 243 m water depth) show that depositional conditions for heavy metals in sediments were similar at all water dep ths prior to anthropogenic influxes. After the onset of industrializat ion, the deep anoxic parts of the basin expanded at irregular interval s and the < 63 mu m fractions of the sediments became characterized by high organic C and heavy-metal accumulation rates. The difference bet ween the enrichment patterns in the basin and on the slope suggests th at material enriched in organic matter (and associated trace elements) and in sulphides (and associated trace elements) is preferentially de posited in the basin. The composition of the sediments in the basin th erefore reflects the effects of lateral transport of the sediment, whi ch enriches organic C in the deepest part of the basin and of anoxia i n the deep water of the basin, where metal sulphides are formed. Previ ous estimates of the timing of the onset of industrial pollution in th e Central Baltic may have been in error because these new data suggest that this began in the Eastern Gotland Basin in about 1870. (C) 1998 Elsevier Science Ltd. All rights reserved.