Hi fellow students and scientists.
Im studying organic carbon levels and its origins in deep sediment cores from seagrass meadows sampled along the swedish Skagerrak coast. One core was successfully dated with C14, and the oldest section seems to be well within the Littorina sea period.
This site has apparently never been above sealevel, according to geodata since the last glacial ice cover. So I wonder, is it possible that the oldest part (thick, brown clay layer of organic and terrestrial carbon) is ackumulated humus transported by the glacial melting and subsequent runoff on the Swedish west coast?
I read in an article that during the Littorina sea period, there was indeed much runoff from land but nothing was mentioned about organic carbon - just inorganic.
My samples were treated with acid to remove inorganic remains. If there's anybody here with knowledge on postglacial sediments, Id love to hear what you think :)
The core profile can be summarized as follows:
___________________________________________________
1. Seagrass sediment section: Zostera marina.
~0-60 cm slice depth (decompressed).
Age 0-1700 BP.
Exclusively marine signal, from C/N ratio & isotopes.
___________
2. Grey clay section: much rocks and shells.
~65-95 cm slice depth (decompressed).
Age 1700-3800 BP.
Both marine and terrestrial signals, C/N ratio & isotopes.
___________
3. Brown clay section: small amount of rocks.
~105-130 cm slice depth (decompressed).
Age 3800 - 8092 BP.
Exclusively terrestrial signals, C/N ratio & isotopes.
___________________________________________________
Thank you in advance!
Sanne Bergman
I think this paper could help you;
Svensk Kärnbränslehantering AB Shore displacement in northern Uppland during the last 6500 calender years, Anna Hedenström, Jan Risberg, October 2003,
The post-glacial sedimentary pattern in north-eastern Uppland is of interest.
That's available on the ResearchGate Server for download.
I have one small idea. You can have a palynological analysis done. I don't know who can do it today, but I'm sure someone will find it. In our area (Ostrava, Czech Republic) a number of peat sites are known from glacial sequences (glacial s. s., glacilaku., glacifluvi etc.). They probably come from interglacials and sometimes contain rich pollen communities. It was solved a lot in the 50s of the 20th century, today no one deals with it.
So based on what you're saying, you have an interval that is strongly
dominated by by terrestrial "signals." Is this confirmed by observations
of the type of palynomorphs and microscopy? Also, is this 105-130 cm interval have much more or much less total organic matter? This might impact whether it is likely the cause is one of dilution (e.g. less marine but same terrestrial)
or preservation or possibly other reasons. If there was increased runoff
from the continental, the terrestrial content could have accumulated much
faster than the marine, thus increasing the relative proportion. Also consider
the timing of the spread of plants and trees as Scandinavia was deglaciated (I
do not happen to know when this happened, but assume it is well known).
Take away comments:
- Did you inspect the types of organic matter and attempt to ID the palynomorphs?
- If you have, is it worthwhile to do point-count to quantify the relation
between marine and terrestrial organics?
- What was the total organic matter of each layer?
- check literature for not just sea-level change but also the timing of the
spread of flora after deglaciation of Scandinavia
If after the literature search, you realize that little has been written regarding the organic matter story, that might be worth reporting in whatever dissertation or publications you generate.
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