Quantitative salinity reconstructions of the Baltic Sea during the mid‐Holocene. (30th December 2015)

• Record Type: Journal Article
• Authors: Ning, Wenxin; Andersson, Per S.; Ghosh, Anupam; Khan, Mansoor; Filipsson, Helena L.
• Other Names: Arz H. W. guestEditor.; Leipe T. guestEditor.; Moros M. guestEditor.
• Is Part Of: Boreas. Volume 46:Number 1(2017:Jan.)
• Page Start: 100
• Page End: 110
• Publication Date: 2015-12-30
• Subjects: Geology, Stratigraphic -- Quaternary -- Periodicals; 551.79
• DOI: 10.1111/bor.12156
• Languages: English
• ISSNs: 0300-9483

Abstract

Abstract : We reconstructed the past coastal environment of the Baltic Sea from c . 7300 to 3500 cal. a BP, with a focus on sea surface salinity (SSS). To quantitatively determine the SSS, two methods were employed: measurements of 87 Sr/ 86 Sr ratios in mollusc shells (SSSS r ) and process length variations of dinoflagellate cysts Operculodinium centrocarpum (SSSpl ). The SSSS r was ~6–7 between 6800 and 6400 cal. a BP, similar to modern conditions. Between 6000 and 3900 cal. a BP, SSSS r was consistently higher, ranging between ~9 and 13. Microfossils sensitive to salinity variations, such as Radiosperma corbiforum and Spiniferites spp., support the SSSS r estimate. In comparison with the SSSS r, the SSSpl values were consistently higher, with an average of ~14. We suggest SSSpl tend to overestimate salinity and are not as reliable as SSSSr . A multi‐proxy approach, including analysis of microfossil, organic carbon content, C/N ratios and grain‐size, allowed for a division of the study period into three zones (Zones I–III). Zone I (7300–6400 cal. a BP) is characterized by relatively O. centrocarpum and R. corbiforum concentrations, silt contents and C/N ratios, corresponding to the regional Littorina transgression maximum. Zone II (6400–3900 cal. a BP) is characterized by increased Spiniferites spp. and decreased R. corbiforum abundances, and by lowered C/N ratios and silt contents relative to Zone I. Zone III (3900–3500 cal. a BP) represents the start of the Post‐Littorina Sea phase, indicating a shift to the modern Baltic Sea phase with decreased salinity.