The Chew Bahir Coring Project: Climate-vegetation feedbacks during the African Humid Period in the southern Ethiopian Rift
Final Report Abstract
We have collected six up to 18.86 m long sediment cores CB01–06 from the Chew Bahir basin, Southern Ethiopian Rift. The analysis of these cores has provided the necessary information about sedimentary processes in the Chew Bahir as required for detailed planning of deeper drilling in the Southern Ethiopian Rift within the framework of the ICDP Hominid Sites and Paleolakes Drilling Project (HSPDP) project that has already been delivered two up to 272 m long cores to be analyzed from mid April 2015 on. The core lithology of CB01-06 comprises lacustrine silty clays, intercalated with sandy coarse detrital layers, interpreted as resulting from erosional input by strong rainfall events from an arid, sparsely vegetated catchment; diatoms and ostracodes are present, mostly in discrete layers of the core profile; pollen and spore concentrations are low (Objective #1). The uppermost Chew Bahir basin sediments have been shown to be suitable for dating by radiocarbon, while the quartz and tephra content ensure strong potential for luminescence and Ar/Ar dating of the deeper sedimentary archive, supplemented by paleomagnetic geochronology. The mean sediment accumulation rate (SAR) determined from the pilot core is 0.7 mm/a, but the rate varies, with a relatively high value of 1.3 mm/a from 45 to 40 ka BP. After 40 ka BP, sedimentation rates decreased to 0.6 mm/a until ~35 ka BP), and then to 0.1 mm/a until 13 ka BP. The sedimentation rate then increased in two steps, from 0.4 mm/a between 13 and 3 ka BP, to 0.7 mm/a between 3 and 1 ka BP, reaching 1.3 mm/a during the last millennium (Objective #2). Geochemical, physical and biological indicators show that Chew Bahir responded to climatic fluctuations on millennial to centennial timescales, and to the precessional cycle, since the Last Glacial Maximum. Potassium content of the sediment appears to be a reliable proxy for aridity, showing that Chew Bahir reacted to the insolation-controlled humidity increase of the African Humid Period (ca. 15-5 kyr BP) with a remarkably abrupt onset and a gradual termination, framing a sharply defined arid phase (~12.8–11.6 ka cal BP) corresponding to the Younger Dryas chronozone. The Chew Bahir record correlates well with low- and high-latitude (mainly of the northern hemisphere) paleoclimate, demonstrating that the site responded to regional and global climate changes (Objective #3).
Publications
- (2010) Human Evolution and Migration in a Variable Environment: The Amplifier Lakes of East Africa.Quaternary Science Reviews, 29, 2981-2988
Trauth, M.H., Maslin, M.A., Deino, A., Junginger, A., Lesoloyia, M., Odada, E., Olago, D.O., Olaka, L., Strecker, M.R., Tiedemann, R.
- (2010) The sensitivity of East African rift lakes to climate fluctuations. Journal of Paleolimnology, 44, 629–644
Olaka, L.A., Odada, E.O., Trauth, M.H., Olago, D.O.
- (2012) Climatic change recorded in the sediments of the Chew Bahir basin, southern Ethiopia, during the last 45,000 years. Quaternary International, 274, 25–37
. Foerster, V., Junginger, A., Langkamp, O., Gebru, T., Asrat, A., Umer, M., Lamb, H., Wennrich, V., Rethemeyer, J., Nowaczyk, N., Trauth, M.H., Schäbitz, F.
(See online at https://doi.org/10.1016/j.quaint.2012.06.028) - (2013) Hydrological constraints of paleo-Lake Suguta in the Northern Kenya Rift during the African Humid Period (15 - 5 ka BP). Global and Planetary Change, 111, 174–188
Junginger, A., Trauth, M.H.
(See online at https://doi.org/10.1016/j.gloplacha.2013.09.005) - (2014) A new probabilistic technique to build an age model for complex stratigraphic sequences. Quaternary Geochronology, 22C, 65-61
Trauth, M.H.
(See online at https://doi.org/10.1016/j.quageo.2014.03.001) - (2014) A synthesis of the theories and concepts of early human evolution. Philosophical Transactions B, 370, 20140064
Maslin, M.A., Shultz, S., Trauth, M.H.
(See online at https://doi.org/10.1098/rstb.2014.0064) - (2014) East African climate pulses and early human evolution, commissioned review paper. Quaternary Science Reviews, 101, 1-17
Maslin, M.A., Brierley, C.M., Milner, A.M., Shultz, S., Trauth, M.H., Wilson, K.E.
(See online at https://doi.org/10.1016/j.quascirev.2014.06.012) - (2014) The effect of solar irradiation changes on water levels in the paleo-Lake Suguta, Northern Kenya Rift, during the late Pleistocene African Humid Period (15 - 5 ka BP). Palaeogeography, Palaeoclimatology, Palaeoecology, 396, 1–16
Junginger, A., Roller, S., Trauth, M.H.
(See online at https://doi.org/10.1016/j.palaeo.2013.12.007) - (2015) Episodes of Environmental Stability versus Instability in Late Cenozoic Lake Records of Eastern Africa. Journal of Human Evolution
Volume 87, October 2015, Pages 21-31
Trauth MH, Bergner AGN, Foerster V, Junginger A, Maslin MA, Schaebitz F
(See online at https://doi.org/10.1016/j.jhevol.2015.03.011)
