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ENVIRONMENTAL CONDITIONS OF SHELLY PHOSPHORITE ACCUMULATION IN THE RAKVERE PHOSPHORITE REGION, NORTHERN ESTONIA

1994; Estonian Academy Publishers; Volume: 43; Issue: 3 Linguagem: Inglês

10.3176/geol.1994.3.01

1736-7913

H Heinsalu, Urmas Raudsepp, V Viira,

Mine drainage and remediation techniques

The established conodont zones in the Cambrian-Ordovician boundary beds in northern Estonia serve as a basis for the interpretation of the succession of changes in the facies conditions of sedimentation.The facies maps compiled by time intervals correspond to the Westergaardodina, Cordylodus andresi, C. proavus, C. lindstromi, and C. rotundatus-C.angulatus conodont zones.Phosphorite accumulation was the most intensive during the C. proavus time.The rugged topography of the underlying Lower Cambrian Tiskre and Vaki formations on the territory of the Rakvere phosphorite region was of great significance in the phosphorite accumulation.At the initial stages of phosphorite accumulation three bottom swells (islands) existed there.The most intensive piling up of phosphorite was related to these swells.They coincide in direction with the present Aseri and Ahtme disturbance zones.