PLAYA LAKE AND MARGINAL WETLAND SEDIMENTS RECORD OVER 1000 YEARS OF CLIMATE SHIFTS AT LAKE SOLAI, EAST AFRICAN RIFT, KENYA
The wetland core is divided based on texture, organic matter (OM) content, and biological proxies. Zone 1 (187-67 cm) consists of OM-poor (<0.5 wt% C) crumbly-textured silty clays, scattered carbonate nodules with δ13C and δ18O consistent with pedogenesis, and interbedded laminated clays, suggesting periodic exposure and flooding of a playa lake. An abrupt change to OM-rich black clays and peaty clays occurs at the start of Zone 2 (67-40 cm) and marks the inception of the wetland at ~ AD 1155. Zone 1 (40-0 cm) is more OM-rich (2-7 wt% C) indicating better wetland development and higher lake levels beginning at ~ AD 1490. The lake core (86 cm) consists of crumbly silts interbedded with laminated silty clays consistent with periodic exposure and flooding events. At 65 cm, an abrupt increase in OM content (~2 wt% C) indicates possible correlation with the onset of wetland formation. Greater proportions of detrital kaolinite and illite clay-minerals (highland source) relative to smectite (rift-valley source) occurs in the wetland and upper lake sediments consistent with greater runoff and erosion of the highlands as a result of wetter conditions. Both the wetland and lake records in this small basin indicate inception of wetter conditions at the start of the Little Ice Age.