Lake Magadi and the Soda Lake Cycle: A Study of the Modern Sodium Carbonates and of Late Pleistocene and Holocene Lacustrine Core Sediments

摘要

The Magadi Basin, Kenya, within the East African Rift Valley, contains two closed-basin alkaline lakes, Lake Magadi and Nasikie Engida that now precipitate trona (Na2CO3.NaHCO3.2H2O) and nahcolite (NaHCO3). Observations of the conditions of modern trona and nahcolite deposition in the Magadi Basin form the basis of the "soda lake cycle". This study aims to use the sedimentary structures of the modern sodium carbonates of Lake Magadi as an analogue for similar ancient deposits around the world, including the vast trona and nahcolite deposits of the Eocene Green River Formation. Lake Magadi has been evolving since 1.08 Ma within a well-known region of early hominin activity in East Africa. As part of the Hominin Sites and Paleo-lakes Drilling Project (HSPDP) four boreholes were drilled beneath Lake Magadi up to a maximum depth of 197 m. Analysis of three of the extracted sediment cores has provided information on the evolution of Lake Magadi from the Late Pleistocene to present.