LABYRINTH PATTERNS IN MAGADI CHERTS: EVIDENCE FOR EARLY FORMATION OF SILICEOUS GELS

Sedimentary cherts, with exceptionally well-preserved microfossils, are known from the Archean, yet their origins remain poorly understood. Lake Magadi, Kenya, has been used as the modern analog system for understanding the origins of non-biogenic chert. Here, we present evidence for synsedimentary formation of Magadi cherts directly from siliceous gels. Petrographic thin section analysis and field emission scanning electron microscopy of subsurface cherts from cores drilled in Lake Magadi during the Hominin Sites and Paleolakes Drilling Project (HSPDP) in 2014, led to the discovery of two-dimensional branching “labyrinth patterns”, which are a type of fractal “squeeze” pattern formed at air-liquid interfaces. Labyrinth patterns preserved in Magadi cherts indicate invasion of air along planes in dewatering gels. The patterns support the precipitation of silica gels in saline-alkaline Lake Magadi and syndepositional drying of gels in contact with air as part of chert formation. Identification of labyrinth patterns in ancient cherts can provide a better understanding of paleoenvironmental and geochemical conditions in the past.