TY - JOUR A1 - Dulanya, Zuze A1 - Croudace, Ian A1 - Reed, Jane M. A1 - Trauth, Martin H. T1 - Palaeolimnological reconstruction of recent environmental change in Lake Malombe (S. Malawi) using multiple proxies JF - Water SA N2 - Shallow inland water bodies in Malawi continue to be threatened by various environmental challenges despite their importance to the fisheries industry. Due to the complex interaction between natural and anthropogenic disturbances, disentangling the effect of the two may be a complicated process. The littoral zone of most water bodies is important in environmental reconstructions including pollution and lake level monitoring. This study used a littoral zone, transect-based approach employing multi-proxy palaeolimnological techniques to reconstruct recent environmental change (ca. 100 yrs.) in Lake Malombe in the Malawi Rift, East Africa. The results of the study could inform fisheries management in Lake Malombe, which experienced a catastrophic decline in fish stocks. Results support documentary evidence for the complete desiccation of the lake less than 100 years ago. Subsequently, there is evidence for accelerated eutrophication in the recent past. In light of these results, it is concluded that transect sampling approaches rather than relying on single core measurements, and the need for careful consideration of the types of proxy, are significant considerations in palaeoenvironmental reconstructions. KW - littoral zone KW - palaeolimnology KW - diatoms KW - Lake Malombe Y1 - 2014 U6 - https://doi.org/10.4314/wsa.v40i4.17 SN - 0378-4738 SN - 1816-7950 VL - 40 IS - 4 SP - 717 EP - 727 PB - Water Research Commission CY - Pretoria ER - TY - JOUR A1 - Junginger, Annett A1 - Roller, Sybille A1 - Olaka, Lydia A. A1 - Trauth, Martin H. T1 - The effects of solar irradiation changes on the migration of the Congo Air Boundary and water levels of paleo-Lake Suguta, Northern Kenya Rift, during the African Humid Period (15-5 ka BP) JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - The water-level record from the 300 m deep paleo-lake Suguta (Northern Kenya Rift) during the African Humid Period (AHP, 15-5 ka BP) helps to explain decadal to centennial intensity variations in the West African Monsoon (WAM) and the Indian Summer Monsoon (ISM). This water-level record was derived from three different sources: (1) grain size variations in radiocarbon dated and reservoir corrected lacustrine sediments, (2) the altitudes and ages of paleo-shorelines within the basin, and (3) the results of hydro-balance modeling, providing important insights into the character of water level variations (abrupt or gradual) in the amplifier paleo-Lake Suguta. The results of these comprehensive analyses suggest that the AHP highstand in the Suguta Valley was the direct consequence of a northeastwards shift in the Congo Air Boundary (CAB), which was in turn caused by an enhanced atmospheric pressure gradient between East Africa and India during a northern hemisphere insolation maximum. Rapidly decreasing water levels of up to 90 m over less than a hundred years are best explained by changes in solar irradiation either reducing the East African-Indian atmospheric pressure gradient and preventing the CAB from reaching the study area, or reducing the overall humidity in the atmosphere, or a combination of both these effects. In contrast, although not well documented in our record we hypothesize a gradual end of the AHP despite an abrupt change in the source of precipitation when a decreasing pressure gradient between Asia and Africa prevented the CAB from reaching the Suguta Valley. The abruptness was probably buffered by a contemporaneous change in precession producing an insolation maximum at the equator during October. Whether or not this is the case, the water-level record from the Suguta Valley demonstrates the importance of both orbitally-controlled insolation variations and short-term changes in solar irradiation as factors affecting the significant water level variations in East African rift lakes. KW - East African Rift System KW - Suguta Valley KW - African Humid Period KW - Congo Air Boundary Y1 - 2014 U6 - https://doi.org/10.1016/j.palaeo.2013.12.007 SN - 0031-0182 SN - 1872-616X VL - 396 SP - 1 EP - 16 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Maslin, Mark A. A1 - Brierley, Chris M. A1 - Milner, Alice M. A1 - Shultz, Susanne A1 - Trauth, Martin H. A1 - Wilson, Katy E. T1 - East African climate pulses and early human evolution JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Current evidence suggests that all of the major events in hominin evolution have occurred in East Africa. Over the last two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of East Africa has varied in the past. The landscape of East Africa has altered dramatically over the last 10 million years. It has changed from a relatively flat, homogenous region covered with mixed tropical forest, to a varied and heterogeneous environment, with mountains over 4 km high and vegetation ranging from desert to cloud forest. The progressive rifting of East Africa has also generated numerous lake basins, which are highly sensitive to changes in the local precipitation-evaporation regime. There is now evidence that the presence of precession-driven, ephemeral deep-water lakes in East Africa were concurrent with major events in hominin evolution. It seems the unusual geology and climate of East Africa created periods of highly variable local climate, which, it has been suggested could have driven hominin speciation, encephalisation and dispersal out of Africa. One example is the significant hominin speciation and brain expansion event at -1.8 Ma that seems to have been coeval with the occurrence of highly variable, extensive, deep-water lakes. This complex, climatically very variable setting inspired first the variability selection hypothesis, which was then the basis for the pulsed climate variability hypothesis. The newer of the two suggests that the long-term drying trend in East Africa was punctuated by episodes of short, alternating periods of extreme humidity and aridity. Both hypotheses, together with other key theories of climate-evolution linkages, are discussed in this paper. Though useful the actual evolution mechanisms, which led to early hominins are still unclear and continue to be debated. However, it is clear that an understanding of East African lakes and their palaeoclimate history is required to understand the context within which humans evolved and eventually left East Africa. (C) 2014 The Authors. Published by Elsevier Ltd. KW - Human evolution KW - East Africa KW - Palaeoclimatology KW - Palaeoliminology KW - Tectonics KW - Hominin KW - Orbital forcing KW - Cenozoic climate transitions KW - Pulsed climate variability hypothesis Y1 - 2014 U6 - https://doi.org/10.1016/j.quascirev.2014.06.012 SN - 0277-3791 VL - 101 SP - 1 EP - 17 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Trauth, Martin H. T1 - A new probabilistic technique to build an age model for complex stratigraphic sequences JF - Quaternary geochronology : the international research and review journal on advances in quaternary dating techniques N2 - The age models of fluvio-lacustrine sedimentary sequences are often subject of discussions in paleoclimate research. The techniques employed to build an age model are very diverse, ranging from visual or intuitive estimation of the age-depth relationship over linear or spline interpolations between age control points to sophisticated Bayesian techniques also taking into account the most likely deposition times of the type of sediment within the sequence. All these methods, however, fail in detecting abrupt variations in sedimentation rates, including the possibility of episodes of no deposition (hiatus), which is the strength of the method presented in this work. The new technique simply compares the deposition time of equally thick sediment slices from the differences of subsequent radiometric age dates and the unit deposition times of the various sediment types. The percentage overlap of the distributions of these two sources of information, together with the evidence from the sedimentary record, helps to build an age model of complex sequences including abrupt variations in the rate of deposition including one or many hiatuses. (C) 2014 Elsevier B.V. All rights reserved. KW - Age-depth modelling KW - Stratigraphy KW - Sedimentation rate KW - Hiatus KW - MATLAB Y1 - 2014 U6 - https://doi.org/10.1016/j.quageo.2014.03.001 SN - 1871-1014 SN - 1878-0350 VL - 22 SP - 65 EP - 71 PB - Elsevier CY - Oxford ER -