| dc.creator |
Dettman, David L. |
|
| dc.creator |
Palacios-Fest, Manuel R. |
|
| dc.creator |
Nkotagu, Hudson H. |
|
| dc.creator |
Cohen, Andrew S. |
|
| dc.date |
2016-09-21T12:40:34Z |
|
| dc.date |
2016-09-21T12:40:34Z |
|
| dc.date |
2005 |
|
| dc.date.accessioned |
2018-03-27T08:57:33Z |
|
| dc.date.available |
2018-03-27T08:57:33Z |
|
| dc.identifier |
Dettman, D.L., Palacios-Fest, M.R., Nkotagu, H.H. and Cohen, A.S., 2005. Paleolimnological investigations of anthropogenic environmental change in Lake Tanganyika: VII. Carbonate isotope geochemistry as a record of riverine runoff. Journal of Paleolimnology, 34(1), pp.93-105. |
|
| dc.identifier |
http://hdl.handle.net/20.500.11810/3845 |
|
| dc.identifier |
10.1007/s10933-005-2400-x |
|
| dc.identifier.uri |
http://hdl.handle.net/20.500.11810/3845 |
|
| dc.description |
Evaporation dominates the removal of water from Lake Tanganyika, and therefore the oxygen isotope
composition of lake water has become very positive in comparison to the waters entering the lake. The
surface water in Lake Tanganyika has remained relatively unchanged over the last 30 years with a seasonal
range of +3.2 to +3.5& VSMOW. Water from small rivers entering the lake seems to have a d18O value
between 3.5 and 4.0&, based on scattered measurements. The two largest catchments emptying into the
lake deliver water that has a d18O value between these two extremes. This large contrast is the basis of a model
presented here that attempts to reconstruct the history of runoff intensity based on the d18O of carbonate
shells from Lake Tanganyika cores. In order to use biogenic carbonates to monitor changes in the d18O of
mixing-zone water, however, the oxygen isotope fractionation between water and shell carbonate must be
well understood. The relatively invariant environmental conditions of the lake allow us to constrain the
fractionation of both oxygen and carbon isotope ratios. Although molluskan aragonitic shell d18O values are
in agreement with published mineral-water fractionations, ostracode calcite is 1.2& more positive than
that of inorganic calcite precipitated under similar conditions. Ostracode shell d18O data from two cores from
central Lake Tanganyika suggest that runoff decreased in the first half of this millennium and has increased in
the last century. This conclusion is poorly constrained, however, and much more work needs to be done on
stable isotope variation in both the waters and carbonates of Lake Tanganyika. We also compared the d13C
of shells against predicted values based solely on the d13C of lake water dissolved inorganic carbon (DIC).
The ostracode Mecynocypria opaca is the only ostracode or mollusk that falls within the predicted range.
This suggests that M. opaca has potential for reconstructing the carbon isotope ratio of DIC in Lake
Tanganyika, and may be a useful tool in the study of the history of the lake’s productivity and carbon cycle. |
|
| dc.language |
en |
|
| dc.publisher |
Springer |
|
| dc.subject |
Carbon isotope ratio |
|
| dc.subject |
Lake Tanganyika |
|
| dc.subject |
Mollusk |
|
| dc.subject |
Ostracode |
|
| dc.subject |
Oxygen isotope ratio |
|
| dc.subject |
River discharge |
|
| dc.subject |
Stable isotope fractionation |
|
| dc.title |
Paleolimnological Investigations of Anthropogenic Environmental Change in Lake Tanganyika: VII. Carbonate Isotope Geochemistry as a Record of Riverine Runoff |
|
| dc.type |
Journal Article, Peer Reviewed |
|