气候变化领域集成服务门户(CCPortal): Quaternary history of the Lake Magadi Basin; southern Kenya Rift: Tectonic and climatic controls

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DOI	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 R.W.; Muiruri V.M.; Rabideaux N.M.; Lowenstein T.K.; McNulty E.P.; Leet K.; Deocampo D.; Luo S.; Deino A.L.; Cohen A.; Sier M.J.; Campisano C.; Shen C.-C.; Billingsley A.; Mbuthia A.; Stockhecke M.
发表日期	2019
ISSN	0031-0182
起始页码	97
结束页码	118
卷号	518
英文摘要	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 CO 2 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. © 2019 Elsevier B.V.
英文关键词	Diatoms; Geochemistry; Mineralogy; Palaeolakes; Rift basins; Sedimentology
语种	英语
scopus关键词	aridity; climate variation; diatom; environmental conditions; freshwater environment; geochemistry; lacustrine environment; mineralogy; paleoenvironment; paleosol; Quaternary; reconstruction; sedimentology; tectonic setting; volcaniclastic deposit; East African Rift; Kajiado; Kenya; Kenya Rift; Lake Magadi; Bacillariophyta; Trona
来源期刊	Palaeogeography, Palaeoclimatology, Palaeoecology
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/151064
作者单位	Department of Geography, Hong Kong Baptist University, Kowloon Tong, Hong Kong; Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada; Palynology and Palaeobotany Section, Department of Earth Sciences, National Museums of Kenya, P.O. Box 40658, Nairobi, 00100, Kenya; Department of Chemistry, Rutgers University, Newark, NJ 07102, United States; Department of Geological Sciences, State University of New York, Binghamton, NY 13902, United States; Department of Geosciences, Georgia State UniversityGA 30302, United States; Department of Earth Sciences, National Cheng-Kung University, Tainan, 701, China; Berkeley Geochronology Center, Berkeley, CA 94709, United States; Department of Geosciences, University of Arizona, Tucson, AZ 85721, United States; Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, United Kingdom; Centro Nacional de Investigación sobre la Evolución Humana, Burgos, 09002, Spain; Institute of Human Origins, School of Human Evolution...
推荐引用方式 GB/T 7714	Bernhart Owen R.,Renaut R.W.,Muiruri V.M.,et al. Quaternary history of the Lake Magadi Basin; southern Kenya Rift: Tectonic and climatic controls[J],2019,518.
APA	Bernhart Owen R..,Renaut R.W..,Muiruri V.M..,Rabideaux N.M..,Lowenstein T.K..,...&Stockhecke M..(2019).Quaternary history of the Lake Magadi Basin; southern Kenya Rift: Tectonic and climatic controls.Palaeogeography, Palaeoclimatology, Palaeoecology,518.
MLA	Bernhart Owen R.,et al."Quaternary history of the Lake Magadi Basin; southern Kenya Rift: Tectonic and climatic controls".Palaeogeography, Palaeoclimatology, Palaeoecology 518(2019).