Fig. 4
(Diagram modified from [46])
Diagrammatic sketch contrasting chert-rich, marine carbonate rock and secondary silica and chert rubble deposits in a continental karst terrain. a Early diagenetic, marine carbonate-draped chert nodule with variable percentage of unreplaced carbonate. b Lag accumulation of resistant, slumped and randomly oriented chert nodules in a continental karst terrain. Unreplaced carbonate is leached out and replaced by secondary, cavity-fill silica which consists of fibrous, botryoidal and drusy quartz