Quaternary history of the Lake Magadi Basin, southern Kenya Rift

Tectonic and climatic controls

R. Bernhart Owen, Robin W. Renaut, Veronica M. Muiruri, Nathan M. Rabideaux, Tim K. Lowenstein, Emma P. McNulty, Kennie Leet, Daniel Deocampo, Shangde Luo, Alan L. Deino, Andrew Cohen, Mark J. Sier, Christopher Campisano, Chuan Chou Shen, Anne Billingsley, Anthony Mbuthia, Mona Stockhecke

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Sediments from the Magadi Basin (south Kenya Rift) preserve a one-million-year palaeoenvironmental record that reflects interactions between climatic, volcanic and tectonic controls. Climate changes that impacted sedimentation include wet-dry cycles on variable timescales and an overall progressive trend towards greater aridity. Volcanic influences involved inputs of tephra to the basin, significant inflow of geothermal fluids, and the effects of weathering, erosion and transportation of clastics from trachyte and basalt terrains. Tectonic controls, which were often step-like, reflect the influence of faults that provided pathways for fluids and which controlled accommodation space and drainage directions. Intensified aridity and evaporative concentration resulted in salinity and pH increasing with time, which led to a change from calcite deposition in mildly saline lakes before 380 ka to the later formation of zeolites from reactions of volcaniclastic debris with highly alkaline lake and pore water. After 105 ka, hyperalkaline conditions led to trona accumulation and increasingly variable rare earth elements (REEs). The presence of mixed saline and freshwater diatom taxa between 545 and 16 ka indicates climate variability and episodic inputs of fresh water to saline lakes. Calcrete formed in lake marginal settings during semi-arid periods. Tectonic controls operated independently of climate, but they interacted together to determine environmental conditions. Aquatic deposition was maintained during periods of increasing aridity because fault-controlled ambient and geothermal springs continued to flow lakewards. This recharge, in turn, limited pedogenesis: palaeosols are common in other rift floor sequences. Trona formed when aridity and evapoconcentration increased, but its precipitation also reflects increased magmatic CO2 that ascended along faults. Basin fragmentation and north-south fractures caused loss of cross-rift (east-west) drainage from rift-marginal basalts, resulting in reduced transition metals after 545 ka. The Magadi Basin demonstrates how a careful reconstruction of these complex tectono-climatic interactions is essential for accurate palaeoenvironmental reconstruction in continental rifts and in other tectonic settings.

Original languageEnglish (US)
Pages (from-to)97-118
Number of pages22
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume518
DOIs
StatePublished - Mar 15 2019

Fingerprint

dry environmental conditions
tectonics
aridity
Kenya
basins
lakes
basalt
saline lake
history
basin
drainage
transition elements
wet-dry cycles
zeolites
climate
tephra
alkaline water
calcrete
rare earth elements
trachyte

Keywords

  • Diatoms
  • Geochemistry
  • Mineralogy
  • Palaeolakes
  • Rift basins
  • Sedimentology

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology

Cite this

Bernhart Owen, R., Renaut, R. W., Muiruri, V. M., Rabideaux, N. M., Lowenstein, T. K., McNulty, E. P., ... Stockhecke, M. (2019). Quaternary history of the Lake Magadi Basin, southern Kenya Rift: Tectonic and climatic controls. Palaeogeography, Palaeoclimatology, Palaeoecology, 518, 97-118. https://doi.org/10.1016/j.palaeo.2019.01.017

Quaternary history of the Lake Magadi Basin, southern Kenya Rift : Tectonic and climatic controls. / Bernhart Owen, R.; Renaut, Robin W.; Muiruri, Veronica M.; Rabideaux, Nathan M.; Lowenstein, Tim K.; McNulty, Emma P.; Leet, Kennie; Deocampo, Daniel; Luo, Shangde; Deino, Alan L.; Cohen, Andrew; Sier, Mark J.; Campisano, Christopher; Shen, Chuan Chou; Billingsley, Anne; Mbuthia, Anthony; Stockhecke, Mona.

In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 518, 15.03.2019, p. 97-118.

Research output: Contribution to journalArticle

Bernhart Owen, R, Renaut, RW, Muiruri, VM, Rabideaux, NM, Lowenstein, TK, McNulty, EP, Leet, K, Deocampo, D, Luo, S, Deino, AL, Cohen, A, Sier, MJ, Campisano, C, Shen, CC, Billingsley, A, Mbuthia, A & Stockhecke, M 2019, 'Quaternary history of the Lake Magadi Basin, southern Kenya Rift: Tectonic and climatic controls', Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 518, pp. 97-118. https://doi.org/10.1016/j.palaeo.2019.01.017
Bernhart Owen, R. ; Renaut, Robin W. ; Muiruri, Veronica M. ; Rabideaux, Nathan M. ; Lowenstein, Tim K. ; McNulty, Emma P. ; Leet, Kennie ; Deocampo, Daniel ; Luo, Shangde ; Deino, Alan L. ; Cohen, Andrew ; Sier, Mark J. ; Campisano, Christopher ; Shen, Chuan Chou ; Billingsley, Anne ; Mbuthia, Anthony ; Stockhecke, Mona. / Quaternary history of the Lake Magadi Basin, southern Kenya Rift : Tectonic and climatic controls. In: Palaeogeography, Palaeoclimatology, Palaeoecology. 2019 ; Vol. 518. pp. 97-118.
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