Mathematics – Logic
Scientific paper
Jan 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001gecoa..65..253z&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 65, Issue 2, pp.253-265
Mathematics
Logic
17
Scientific paper
Distribution patterns of C 37 and C 38 polyunsaturated long-chain alkenones (LCAs) serve as proxies for the determination of paleotemperatures for marine surface waters. We studied Recent/Subrecent and Late Glacial/Holocene sediments from Germany, Austria, Russia, and the U.S. to test for a correspondence between LCA distribution and surface water temperature in limnic systems. Previously, reports of LCA occurrence were restricted to sediments of 6 wide distributed freshwater and alkaline lakes. In this study 13 of 27 investigated lakes contained LCAs in surface sediments with concentrations varying between 12 to 205 g/g TOC. Late Glacial to Holocene sediment sequences from Lake Steisslingen and Lake Wummsee, (Germany), Lake Pichozero (Russia), and Brush Lake (U.S.A.) contained abundant LCAs with averaged concentrations of 33 to 7536 g/g TOC. For the first time we observed the occurrence of LCAs within in the water column of oligotrophic Lake Stechlin (NE-Germany). Alkenones were restricted to the zone of maximum chlorophyll concentration within the water column indicating that LCAs have a biosynthetic origin and can be attributed to phototrophic (micro)algae. Attempts to identify the producing organism, however, were not successful. Culture experiments allow various phytoplankton to be excluded as producers. Alkenone-producing algae are evidently of small size, hindering microscopical identification. LCAs commonly occur in high concentrations in Late Glacial sediments, mainly during the cold period of the Younger Dryas, whereas the Holocene usually is devoid of polyunsaturated alkenones. The episodic occurrence of LCAs restricts their utility as proxies for continuous geological records. Furthermore, lack of microscopical verification and the episodic distribution allow for different producers of unsaturated alkenones in Recent and Late Glacial sediments. An empirical relationship between LCA distribution and temperature was observed. In fossil sediments from Lake Steisslingen, there is a good correspondence between Uk37 and the temperature-controlled 18 O isotope ratio of lake chalk. Comparison of LCA patterns obtained from the uppermost centimetres of lake sediments with averaged summer surface water temperatures of the lakes studied, demonstrates a trend of covariance ( r 2 : Uk'37 = 0.90, Uk37 = 0.67; n = 9). Hence, the same mechanism that causes temperature-dependence of LCA patterns in marine systems might be effective in limnic settings. Identification of alkenone producers and their culture under controlled temperature are still mandatory before LCAs can be routinely applied as paleotemperature proxy in limnic systems.
Leythaeuser Detlev
Melkonian Michael
Schwark Lorenz
Zink Klaus-G.
No associations
LandOfFree
Temperature dependency of long-chain alkenone distributions in recent to fossil limnic sediments and in lake waters 1 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Temperature dependency of long-chain alkenone distributions in recent to fossil limnic sediments and in lake waters 1, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature dependency of long-chain alkenone distributions in recent to fossil limnic sediments and in lake waters 1 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-923887