TY - JOUR
T1 - Early Pleistocene lacustrine sedimentation and diatom stratigraphy at Munya wa Gicheru, southern Kenya Rift Valley
AU - Owen, R. Bernhart
AU - Lee, Ray K.L.
AU - Renaut, Robin
N1 - Funding Information:
Funding for Owen and Lee was provided by the Research Grant Council of Hong Kong (grant 201709 ) and the Hong Kong Baptist University ( FRG/08-09/056 ). Renaut was supported by NSERC (Canada) Discovery Grant 629-08 , which is gratefully acknowledged. We also would like to thank the Government of Kenya for permission to carry out this research.
PY - 2012/5/1
Y1 - 2012/5/1
N2 - This research develops a detailed palaeoenvironmental history for sediments at Munya wa Gicheru (southern Kenya Rift) and explores the roles of tectonics and climate in the formation of palaeolakes and their use in regional climate correlation. The lacustrine facies of the Munya wa Gicheru deposits were formed from ~1.9 to 1.65Ma and consist of massive and laminated diatomites and diatomaceous silts. Fresh water diatoms include Stephanodiscus transilvanicus, Stephanodiscus niagarae, Aulacoseira agassizi, Aulacoseira ambigua, Aulacoseira goetzeana, Aulacoseira granulata var. valida, A. granulata var. angustissima and Pseudostaurosira zeilleri. One moderately saline phase is marked by the dominance of Cyclotella meneghiniana and by the presence of rare Thalassiosira rudolfii. Twenty-five diatom-based zones and subzones can be distinguished, representing eight high-lake periods and eight shallow-water phases. Erosion surfaces and desiccation cracks indicate two periods of emergence. Lake waters ranged in pH from 7.2 to 9, with conductivities of ~200-11,000μScm -1, but mostly <1000μScm -1. In contrast, the uppermost sediments are comprised of fluvial silts, sands and gravels formed in fluvial, sheetwash and terrestrial settings and represent termination of lacustrine conditions. REE data suggest that the Limuru Trachytes are the dominant source of siliciclastics materials. Geochemical information indicates that catchment weathering was moderate and that CaO concentrations in the sediments are very low. Carbonate rhizoliths are absent. SEM images show minimal corrosion or alteration of the diatom silica.
AB - This research develops a detailed palaeoenvironmental history for sediments at Munya wa Gicheru (southern Kenya Rift) and explores the roles of tectonics and climate in the formation of palaeolakes and their use in regional climate correlation. The lacustrine facies of the Munya wa Gicheru deposits were formed from ~1.9 to 1.65Ma and consist of massive and laminated diatomites and diatomaceous silts. Fresh water diatoms include Stephanodiscus transilvanicus, Stephanodiscus niagarae, Aulacoseira agassizi, Aulacoseira ambigua, Aulacoseira goetzeana, Aulacoseira granulata var. valida, A. granulata var. angustissima and Pseudostaurosira zeilleri. One moderately saline phase is marked by the dominance of Cyclotella meneghiniana and by the presence of rare Thalassiosira rudolfii. Twenty-five diatom-based zones and subzones can be distinguished, representing eight high-lake periods and eight shallow-water phases. Erosion surfaces and desiccation cracks indicate two periods of emergence. Lake waters ranged in pH from 7.2 to 9, with conductivities of ~200-11,000μScm -1, but mostly <1000μScm -1. In contrast, the uppermost sediments are comprised of fluvial silts, sands and gravels formed in fluvial, sheetwash and terrestrial settings and represent termination of lacustrine conditions. REE data suggest that the Limuru Trachytes are the dominant source of siliciclastics materials. Geochemical information indicates that catchment weathering was moderate and that CaO concentrations in the sediments are very low. Carbonate rhizoliths are absent. SEM images show minimal corrosion or alteration of the diatom silica.
KW - Diatoms
KW - Geochemistry
KW - Kenya Rift
KW - Palaeolimnology
KW - Pleistocene
KW - Sedimentology
UR - http://www.scopus.com/inward/record.url?scp=84859865781&partnerID=8YFLogxK
U2 - 10.1016/j.palaeo.2012.02.033
DO - 10.1016/j.palaeo.2012.02.033
M3 - Journal article
AN - SCOPUS:84859865781
SN - 0031-0182
VL - 331-332
SP - 60
EP - 74
JO - Palaeogeography, Palaeoclimatology, Palaeoecology
JF - Palaeogeography, Palaeoclimatology, Palaeoecology
ER -