Publication Date:
2017-01-24
Description:
Due to a lack of marine macrofossils in many sediment cores from the estuarine Baltic Sea, researchers are often forced to carry out 14 C determinations on bulk sediment samples. However, ambiguity surrounding the carbon source pathways that contribute to bulk sediment formation introduces a large uncertainty into 14 C geochronologies based on such samples, and such uncertainty may not have been fully considered in previous Baltic Sea studies. We quantify this uncertainty by analysing bulk sediment 14 C determinations carried out on densely spaced intervals in independently dated late-Holocene sediment sequences from two central Baltic Sea cores. Our results show a difference of ~600 14 C yr in median bulk sediment reservoir age, or R(t) bulk , between the two core locations (~1200 14 C yr for one core, ~620 14 C yr for the other), indicating large spatial variation. Furthermore, we also find large downcore ( i.e. temporal) R(t) bulk variation of at least ~200 14 C yr for both cores. We also find a difference of 585 14 C yr between two samples taken from the same core depth. We propose that studies using bulk sediment 14 C dating in large brackish water bodies should take such spatiotemporal variation in R(t) bulk into account when assessing uncertainties , thus leading to a larger, but more accurate, calibrated age range.
Print ISSN:
0883-8305
Electronic ISSN:
1944-9186
Topics:
Geosciences
