Application of GDGT-derived temperature proxies on Mt. Kenya

Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane lipids produced by archaea (isoprenoid GDGTs - iGDGTs) and bacteria (branched GDGTs - brGDGTs) in terrestrial and aquatic settings. Our study examines the relationship between GDGT distribution and environmental parameters in soils collected along Mt. Kenya to examine their applicability as paleotemperature and paleoelevation proxies. Both global and regional calibrations were tested on our dataset. brGDGT-derived temperature for Mt. Kenya linearly correlates with altitude and is consistent for all the calibrations although the derived temperature lapse rate (0.53 °C/100 m) along the mountain from the global soil calibration by [1] is consistent with gridded climate data (0.52°C /100 m) along this transect. This lapse rate is lower than the regional estimate of 0.70°C /100 m previously obtained in other altitudinal gradients (Mt. Rungwe and Mt. Kilimanjaro) from the same region. Although brGDGTs are considered as a robust paleoelevation proxy regionally, individual site performances may be unique to their environmental setting, geographic location and altitude. In addition, a poor linear correlation between altitude and iGDGT-derived TEX86, a rarely investigated proxy in soils, implies that there are many other factors not investigated here that affects its applicability in tracking temperature changes along altitudinal transects

Kantis: A new Australopithecus site on the shoulders of the Rift Valley near Nairobi, Kenya

ケニア・ナイロビ郊外で初めて発見されたアウストラロピテクス. 京都大学プレスりリス. 2016-03-24.Most Plio-Pleistocene sites in the Gregory Rift Valley that have yielded abundant fossil hominins lie on the Rift Valley floor. Here we report a new Pliocene site, Kantis, on the shoulder of the Gregory Rift Valley, which extends the geographical range of Australopithecus afarensis to the highlands of Kenya. This species, known from sites in Ethiopia, Tanzania, and possibly Kenya, is believed to be adapted to a wide spectrum of habitats, from open grassland to woodland. The Kantis fauna is generally similar to that reported from other contemporaneous A. afarensis sites on the Rift Valley floor. However, its faunal composition and stable carbon isotopic data from dental enamel suggest a stronger C4 environment than that present at those sites. Although the Gregory Rift Valley has been the focus of paleontologists' attention for many years, surveys of the Rift shoulder may provide new perspective on African Pliocene mammal and hominin evolutio

Evaluation of branched GDGTs and leaf wax n-alkane δ2H as (paleo) environmental proxies in East Africa

The role of mountain evolution on local climate is poorly understood and potentially underestimated in climate models. One prominent example is East Africa, which underwent major geodynamic changes with the onset of the East African Rift System (EARS) more than 250 Myr ago. This study explores, at the regional East African scale, a molecular approach for terrestrially-based paleo-climatic reconstructions that takes into account both changes in temperature and in altitude, potentially leading to an improved concept in paleo-climatic reconstructions. Using surface soils collected along pronounced altitudinal gradients in Mt. Rungwe (n=40; Southwest Tanzania) and Mt. Kenya (n=20; Central Kenya), we investigate the combination of 2 terrestrial proxies, leaf wax n-alkane δ2H (δ2Hwax) and branched glycerol dialkyl glycerol tetraether (br GDGT) membrane lipids, as (paleo) elevation and (paleo) temperature proxies, respectively. At the mountain scale, a weak link between δ2Hwax and altitude (R2 = 0.33) is observed at Mt. Kenya, but no relationship is observed at Mt. Rungwe. It is likely that additional parameters, such as decreasing relative humidity (RH) or vegetation changes with altitude, are outcompeting the expected 2H-depletion trend along Mt. Rungwe. In contrast, br GDGT-derived absolute mean annual air temperature (MAAT) and temperature lapse rate (0.65 °C/100 m) for both mountains are in good agreement with direct field measurements, further supporting the robustness of this molecular proxy for (paleo) temperature reconstructions. At the regional scale, estimated and observed δ2H data in precipitation along 3 mountains in East Africa (Mts. Rungwe, Kenya and Kilimanjaro) highlight a strong spatial heterogeneity, preventing the establishment of a regional based calibration of δ2Hwax for paeloaltitudinal reconstructions. Different from that, an improved regional soil calibration is developed between br GDGT distribution and MAAT by combining the data from this study (Mts. Rungwe and Kenya) with previous results from East African surface soils along Mts. Kilimanjaro (Tanzania) and Rwenzori (Uganda). This new regional calibration, based on 105 samples, improves both the R2 (0.77) and RMSE (root mean square error; 2.4 °C) of br GDGT-derived MAAT over the global soil calibrations previously established (R2 = 0.56; RMSE = 4.2 °C) and leads to more accurate (paleo) temperature reconstructions in the region

A system approach framework to the management of lake Baringo, Kenya

Dissertação de Mestrado, Gestão da Água e da Costa, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2010Lago Baringo, é um lago pouco profundo situado no Grande Vale do Rifte, na zona este do continente Africano. Sofreu uma drástica redução no volume e na sua área de superfície devido a mudanças no uso da terra, como consequência da sedimentação devido às alterações climáticas e das actividades humanas na sua bacia hidrográfica. A gestão integrada dos recursos hídricos na bacia hidrográfica do lago tem enfrentado desafios na sua implementação devido à falta de ferramentas e quadros legais. Este trabalho avalia o uso potencial da abordagem da Estrutura de Abordagem Sistemática (SAF), desenvolvido no âmbito do projecto europeu SPICOSA, no Lago Baringo com o objectivo de resolver o problema de sedimentação. Esta metodologia identificou que existe falta de dados e lacunas na gestão associadas à implementação de politicas, devido à complexidade das relações ecológicas, sociais e económicas na bacia do Lago Baringo. A metodologia SAF provou ser uma ferramenta útil na identificação das áreas prioritárias, a serem abordadas para uma gestão sustentável dos recursos hídricos.Lake Baringo is a shallow lake situated in the East African Rift valley that has experienced drastic decline in volume and surface area due to land use changes as a consequence of sedimentation due to climate change and human activities in its catchment. Integrated water resource management in the lake’s catchment has faced challenges in implementation due to the lack of tools and frameworks. This project evaluates the potential use of the Systems Approach Framework (SAF) developed under Science and Policy Integration for Coastal Systems Assessment (SPICOSA) in Lake Baringo to address the sedimentation issue. The methodology identified data and management gaps associated with policy implementation due to the complexity of ecological, social and economic relationships in the Lake Baringo catchment. The SAF proved to be a useful tool in identifying priority areas to be addressed in the sustainable management of the water resource

Application of GDGT-derived temperature proxies on Mt. Kenya

International audienc

Corrigendum to “Evaluation of branched GDGTs and leaf wax n-alkane δ²H as (paleo) environmental proxies in East Africa” [Geochim. Cosmochim. Acta 198 (2017) 182–193]

International audienc