25th International Meeting on Organic Geochemistry IMOG 2011

P-216
A Pleistocene-Holocene transgressive sediment sequence in the
southern North Sea coast area seen from a biomarker
perspective
Depth (m)
0
2
4
6
8
10
12
14
16
18
Grain size
Jürgen Köster, Fenja Müntinga, Jürgen Rullkötter
ICBM, Carl von Ossietzky University of Oldenburg, Oldenburg, Germany (corresponding
author:juergen.koester@icbm.de)
Biomarker investigations of a 20-m sediment core
from the coast of the southern North Sea reveal
differences in the marine and terrestrial sources of
organic matter between Pleistocene sediments,
Holocene channel fill deposits and modern intertidal
sediments.
A sediment core taken in the back-barrier area of the
C 20:1 HBI
[µg/g TOC]
Mud Sand Sh/X 0 2 4 6 8 10 12
C 37 Alkenones
[µg/g TOC]
0 5 10 15 20 25
Temperature
[°C]
8 10 12 14 16
ACL 23-31
26 27 28
20
Fig. 1: Lithological core log (green: mud, yellow: sand, orange: shells and gravel), depths profiles of selected
biomarkers and temperatures calculated from C37 alkenone distributions (ACL: average chain length index).
island of Spiekeroog (Germany) comprises a
transgressive sequence of Pleistocene sands at the
bottom, ca. 9 m of mud-rich sediments (filling up the
Pleistocene paleo-relief in the course of the Holocene
transgression), and 3.5 m of modern tidal-flat sands
on top.
Biomarkers in the channel sediments are
characterized by compounds of marine origin like C37
and C38 alkenones derived from Haptophyte algae
and monounsaturated C20 highly branched
isoprenoids (HBI; five isomers) originating from
diatoms. Perylene and a series of aromatized
triterpenoids (Freemann et al. 1994) occur almost
exclusively in the channel sediments and are possibly
related to microbial activity (Beck et al. 2011)
Different sources and transport processes for
terrestrial organic matter are indicated by the
abundances of pentacyclic triterpenoids. Further, the
distribution patterns of n-alkanes show differences in
the Holocene and Pleistocene sediments. This
indicates distinct units within the stratigraphically
poorly defined Pleistocene sands.
Elevated alkenone-derived temperature data in the
channel deposits are consistent with the channel
filling during times of relatively warm climatic
conditions (Atlantic period, ca. 7500-5000 a BC) and
of rapid sea-level rise.
References:
Beck et al. (2011) Biogeosciences 8, 55-68
Freemann et al. (1994) Org. Geochem. 21, 1037-49
355