Sudbury Basin Sediments and the Meteoritic Impact Theory of Origin for the Sudbury Structure
The Whitewater Group preserved within the Sudbury Basin structure conforms to a logical succession of beds to be expected for sediments accumulated in a large impact-generated crater. The lowest beds of the Group, the lower Onaping Formation, represent impact-generated breccia and fall-back material, the upper Onaping Formation and the overlying Onwatin Slates represent the restricted crater series, while the succeeding Chelmsford Sandstone represents an open marine turbidite sequence. The turbidites swept across the area at a time when the crater rim was no longer influencing sea bottom current circulation. The apparent anomaly of the occurrence of sediments deposited in an extensive marine environment and presently only found within the Sudbury Basin is attributed to preferential preservation, due to compaction-generated subsidence over the crater and impact-fractured area.