Holocene evolution of a drowned melt-water valley in the Danish Wadden Sea
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Holocene evolution of a drowned melt-water valley in the Danish Wadden Sea. / Pedersen, Jørn Bjarke Torp; Svinth, Steffen; Bartholdy, Jesper.
I: Quaternary Research, Bind 72, Nr. 1, 2009, s. 68-79.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Holocene evolution of a drowned melt-water valley in the Danish Wadden Sea
AU - Pedersen, Jørn Bjarke Torp
AU - Svinth, Steffen
AU - Bartholdy, Jesper
PY - 2009
Y1 - 2009
N2 - Cores from the salt marshes along the drowned melt-water valley of river Varde Å in the Danish Wadden Sea have been dated and analysed (litho- and biostratigraphically) to reconstruct the Holocene geomorphologic evolution and relative sea level history of the area. The analysed cores cover the total post-glacial transgression, and the reconstructed sea level curve represents the first unbroken curve of this kind from the Danish Wadden Sea, including all phases from the time where sea level first reached the Pleistocene substrate of the area. The sea level has been rising from - 12 m below the present level at c. 8400 cal yr BP, interrupted by two minor drops of < 0.5 m at c. 5500 cal yr BP and 1200 cal yr BP, and one major drop of 1.5 m at c. 3300 cal yr BP. Sediment deposition has been able to keep pace with sea level rise, and the Holocene sequence consists in most places of clay atop a basal peat unit overlying sand of Weichselian age and glacio-fluvial origin. In its deepest part, the basal peat started to form around 8400 cal yr BP, and reached a thickness of up to 3.5 m. This thickness is about half of the original, when corrected for auto-compaction. The superimposed clay contains small (63-355 µm) red iron stains in the top and bottom units, and foraminifers of the calcareous type in the middle. The fact that iron stains and foraminifers in no cases coexist, but always exclude each other is interpreted as a result of the difference between salt-marsh facies (iron stains) and tidal-flat facies (foraminifers). This represents a novel and easy way to distinguish between these two otherwise often undistinguishable sedimentary facies in the geological record
AB - Cores from the salt marshes along the drowned melt-water valley of river Varde Å in the Danish Wadden Sea have been dated and analysed (litho- and biostratigraphically) to reconstruct the Holocene geomorphologic evolution and relative sea level history of the area. The analysed cores cover the total post-glacial transgression, and the reconstructed sea level curve represents the first unbroken curve of this kind from the Danish Wadden Sea, including all phases from the time where sea level first reached the Pleistocene substrate of the area. The sea level has been rising from - 12 m below the present level at c. 8400 cal yr BP, interrupted by two minor drops of < 0.5 m at c. 5500 cal yr BP and 1200 cal yr BP, and one major drop of 1.5 m at c. 3300 cal yr BP. Sediment deposition has been able to keep pace with sea level rise, and the Holocene sequence consists in most places of clay atop a basal peat unit overlying sand of Weichselian age and glacio-fluvial origin. In its deepest part, the basal peat started to form around 8400 cal yr BP, and reached a thickness of up to 3.5 m. This thickness is about half of the original, when corrected for auto-compaction. The superimposed clay contains small (63-355 µm) red iron stains in the top and bottom units, and foraminifers of the calcareous type in the middle. The fact that iron stains and foraminifers in no cases coexist, but always exclude each other is interpreted as a result of the difference between salt-marsh facies (iron stains) and tidal-flat facies (foraminifers). This represents a novel and easy way to distinguish between these two otherwise often undistinguishable sedimentary facies in the geological record
KW - Faculty of Science
KW - Varde Å
KW - Vadehavet
KW - Salt-marsh
KW - Incised valley fill
KW - Holocene stratigraphy
KW - The Wadden sea
U2 - 10.1016/j.yqres.2009.02.006
DO - 10.1016/j.yqres.2009.02.006
M3 - Journal article
VL - 72
SP - 68
EP - 79
JO - Quaternary Research
JF - Quaternary Research
SN - 0033-5894
IS - 1
ER -
ID: 12600241