The sedimentary response to a rapid change in lake level in Lake Tanganyika

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2015-12, Vol.440, p.647-658
• Main Authors: McManus, James, Severmann, Silke, Cohen, Andrew S., McKay, Jennifer L., Montanye, Bo R., Hartwell, Anne M., Brucker, Rebecca L.P., Wheatcroft, Robert
• Format: Article
• Language: English
• Subjects: Freshwater; Geochemistry; Lake Tanganyika; Little Ice Age; Transgression; δ13C; δ15N
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2015.09.035

We present records of sedimentary organic carbon, nitrogen, and carbonate, and stable isotope records of organic material and carbonate from a series of sediment cores that straddle the permanent chemocline in Lake Tanganyika. Sedimentation rates for these cores are consistent among the sites (~0.05–0.1cm y−1), and all records show an increase in sedimentary carbonate (aragonite) content centered at ~1879. The mid-19th century coincides with a major (~10m) lake level transgression. Throughout the period of lake level transgression and subsequent regression, the organic matter δ13C and δ15N records develop a prominent and coincident negative excursion followed by a return to values similar to those prior to the lake level transgression. This negative excursion in δ15N and δ13C is also coincident with an increase in carbonate-corrected organic carbon. We interpret the δ13C results as a decline in primary production during the transgression with the δ15N results signaling a concomitant increase in the reliance on nitrogen fixation as the nitrogen source. The coincident peak in organic carbon is interpreted as being a result of enhanced preservation driven by the precipitation and burial of aragonite. •Elevated carbonate concentrations coincide with maximum lake level.•Negative excursions in both δ13C and δ15N coincide with maximum lake level.•Results imply changes in lake chemistry during lake level oscillation centered at 1879.