Mid- to late-Holocene reservoir-age variability and isotope-based palaeoenvironmental reconstruction in the Limfjord, Denmark

TY - JOUR

T1 - Mid- to late-Holocene reservoir-age variability and isotope-based palaeoenvironmental reconstruction in the Limfjord, Denmark

AU - Philippsen, Bente

AU - Olsen, Jesper

AU - Lewis, Jonathan P.

AU - Rasmussen, Peter

AU - Ryves, David B.

AU - Knudsen, Karen Luise

PY - 2013/7

Y1 - 2013/7

N2 - Palaeoenvironmental and C-14 reservoir age variability in the Limfjord, a sound through northern Jutland, Denmark, was investigated for the period 7300 to 1300 cal yr BP. Shells and bulk sediment samples from a core from a former inlet, Kilen, were analysed by radiocarbon dating and stable isotope (C/N) measurements. A strong correlation between the C/N ratios and C-13 values verifies that these are good carbon source indicators and thus allow environmental reconstructions. Furthermore, C-13 values are correlated with salinity in the photic zone, inferred quantitatively from diatom assemblages. They are therefore used to differentiate between brackish and marine palaeo-conditions. C-14 reservoir ages of shells vary from R=-140 to +300 C-14 years. Between 7300 and 5400 cal. yr BP, reservoir age and stable isotope values are highly variable and indicate mixing of marine water and brackish surface waters with hard water effects. After 5400 cal. yr BP, the R values stabilise and show an increasingly marine environment, with C-14 reservoir ages close to 400 years (R=0). After 2000 cal. yr BP, Kilen becomes brackish. Reservoir ages and stable isotope values are again highly variable and C-13 and C/N values are no longer correlated. Before 4000 cal. yr BP, N-15 values vary by only 1 parts per thousand and do not reflect the changes in the marine environment. A N-15 increase between 3500 and 2000 cal. yr BP signifies enhanced organic productivity or a change in agricultural practices.

AB - Palaeoenvironmental and C-14 reservoir age variability in the Limfjord, a sound through northern Jutland, Denmark, was investigated for the period 7300 to 1300 cal yr BP. Shells and bulk sediment samples from a core from a former inlet, Kilen, were analysed by radiocarbon dating and stable isotope (C/N) measurements. A strong correlation between the C/N ratios and C-13 values verifies that these are good carbon source indicators and thus allow environmental reconstructions. Furthermore, C-13 values are correlated with salinity in the photic zone, inferred quantitatively from diatom assemblages. They are therefore used to differentiate between brackish and marine palaeo-conditions. C-14 reservoir ages of shells vary from R=-140 to +300 C-14 years. Between 7300 and 5400 cal. yr BP, reservoir age and stable isotope values are highly variable and indicate mixing of marine water and brackish surface waters with hard water effects. After 5400 cal. yr BP, the R values stabilise and show an increasingly marine environment, with C-14 reservoir ages close to 400 years (R=0). After 2000 cal. yr BP, Kilen becomes brackish. Reservoir ages and stable isotope values are again highly variable and C-13 and C/N values are no longer correlated. Before 4000 cal. yr BP, N-15 values vary by only 1 parts per thousand and do not reflect the changes in the marine environment. A N-15 increase between 3500 and 2000 cal. yr BP signifies enhanced organic productivity or a change in agricultural practices.

KW - Denmark

KW - mid to late Holocene

KW - palaeoenvironmental reconstruction

KW - radiocarbon reservoir effect

KW - stable carbon isotopes

KW - stable nitrogen isotopes

KW - ORGANIC-MATTER

KW - DANISH FJORDS

KW - LEVEL CHANGES

KW - SEA

KW - CALIBRATION

KW - DELTA-C-13

KW - SKAGERRAK

KW - CARBONATE

KW - EVOLUTION

KW - SEDIMENTS

U2 - 10.1177/0959683613479681

DO - 10.1177/0959683613479681

M3 - Journal article

SN - 0959-6836

VL - 23

SP - 1017

EP - 1027

JO - The Holocene

JF - The Holocene

IS - 7

ER -