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Organic carbon sources and accumulation rates
along a regional transect of meromictic lakes, Maine (USA)
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Brad Hubeny, Department of Geological Sciences, Salem State University
The study of organic matter deposition in modern meromictic lakes enables
a deeper understanding of past processes involved in the formation of
lacustrine source rocks. We are working to better understand the source of
lacustrine organic matter in eleven Maine lakes, and are utilizing sediment
cores to unravel depositional cycles of organic matter in two meromictic
lakes with laminated sediments. Results to date include:
•The geochemical signature of particulate organic matter filtered from
modern lakes in Maine suggests mixing of lacustrine algae and terrestrial C3
plants (below). Associated surface sediments display enrichment in the C/N
ratio, suggesting early diagenetic loss of nitrogen during the sedimentation
process.
•Low frequency variability in organic matter deposition in lakes hundreds of
kilometers apart (red curve to right) are coherent, suggesting regional
influences on the production and preservation of organic matter in
meromictic lakes. Ongoing work is utilizing the annually-laminated
sediments and additional radiocarbon dates to better constrain the age
models, allowing for the examination of higher frequency coherency in the
region.
-5
Particulate Organic Matter
Surface Sediments
-10
C4 Land Plants
Ž 13C
-15
-20
Lacustrine
Algae
C3 Land Plants
-25
-30
* Radiocarbon Age
-35
0
10
20
30
40
C/N
50
60
70
80