Sedimentary Trace Elements as Proxies to Depositional Changes Induced by a Holocene Fresh-Brackish Water Transition |
| |
Authors: | John Sternbeck Gustav Sohlenius Rolf O. Hallberg |
| |
Affiliation: | (1) Swedish Environmental Research Institute (IVL), Box 21060, S-100 31 Stockholm, Sweden;(2) Department of Soil Sciences, Swedish University of Agriculture Sciences, Box 7014, S-750 07 Uppsala, Sweden;(3) Department of Geology and Geochemistry, Stockholm University, S-106 91 Stockholm, Sweden |
| |
Abstract: | A halocline developed in the GotlandDeep, Baltic Sea, at c. 8.0 14C ky BP, as theresult of a transition from fresh to brackish water.The sediment-water interface changed from oxic topredominantly anoxic, depositional conditions wereperiodically euxinic and pyrite formation wasextensive. This environmental change led topyritization of the upper part of earlier depositedsediments. This study discusses how the distributionof trace elements (As, Ba, Cd, Cu, Co, Mo, Mn, Ni, Pb,U, Zn and V) were affected by the changing redoxconditions, productivity and salinity. The reducingconditions led to pyritization of Cu, Co, Ni, Cd, Mo,Mn and As. Lead and Zn concentrations are very low inpyrite, in agreement with their coordination tosulfide being tetrahedral. Certain elements areenriched in those sediments deposited under euxinicconditions. This enrichment was caused by scavengingof elements dissolved in the water column and isrestricted to elements that have a comparably longresidence time in the Baltic Sea. Molybdenum appearsto be the most unambigious proxy for euxinicconditions, whereas enrichment of U also requiresbrackish water in the productive zone. In the brackishenvironment, enrichment of Ba and V are linked to thecycling of organic carbon. Manganese and As are theonly elements that have been significantly remobiliseddue to the downward moving pyritization front. |
| |
Keywords: | Baltic Sea euxinic Holocene pyrite trace elements redox conditions sediments |
本文献已被 SpringerLink 等数据库收录! |
|