J. Bjorck et al., Early Holocene deglaciation chronology in Vastergotland and Narke, southern Sweden - biostratigraphy, clay varve, C-14 and calendar year chronology, QUAT SCI R, 20(12), 2001, pp. 1309-1326
Early Holocene varved clay sequences from Vastergotland and Narke, southern
Sweden have been analysed for pollen and marine calcareous fossils. A chro
nology was derived From clay varve measurements and AMS C-14 dating and pol
len stratigraphy. The results suggest that the varve sequences were deposit
ed during the early Holocene between c. 11,500 and 11,200 calendar years BP
which corresponds to the deglaciation of the area. The corresponding varve
ages in the Swedish Time Scale is c. 700-800 years younger which is broadl
y in accordance with the earlier reported error in the Swedish Time Scale.
The discovery of the marine bivalve Portlandia arctica in clay varve sequen
ces from northern Lake Vattern is the first reported evidence of a marine i
ngression into the Baltic basin prior to the Yoldia Sea brackish phase. The
fossil and lithological evidence indicates that the period of marine influ
ence lasted 10-50 years (min age) and occurred c. 140 years before the degl
aciation of the Narke Strait and the subsequent brackish water phase of the
Baltic Yoldia Sea stage. Comparative AMS C-14 datings on terrestrial macro
fossils and the shell of the marine bivalve P. arctica suggest a reservoir
effect of more than 1000 year. However, dates on periostracum from P. arcti
ca gave ages closer to the terrestrial AMS C-14 ages. (C) 2001 Elsevier Sci
ence Ltd. All rights reserved.