Abstract
Phosphatic stromatolites from the early Middle Cambrian (Ordian) of the Georgina Basin are described and identified as Ilicta cf. composita Sidorov. Based on Opik's interpretation of the early Middle Cambrian, the age of the Georgina Basin specimens is similar to that of the type specimens described from the late Early Cambrian of Eastern Siberia. Phosphatic stromatolites occur at the base of dolomitized and partially silicified bioherms up to 4 m thick. The phosphatic forms overlie impermeable, cemented pavement surfaces which were covered by stratiform stromatolites from which rose columnar forms up to 5 cm in height. The stromatolites were phosphatized by penecontemporaneous diagenetic reactions that took place just below the sediment water interface and above the impermeable substrates.
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