A large sheet-like igneous formation in central Australia was once thought to have been emplaced into its host rocks after they lithified, or to have been deposited on the surface as a welded pyroclastic flow. More detailed field work has shown it to have been emplaced into its host sediments while they were unconsolidated and saturated with water. This new synsedimentary interpretation is based on tell-tale characteristics of magma/sediment interaction at the sill margins, including the presence of peperite. Other large igneous bodies have similarly been found to show evidence of significant magma/sediment interaction in a watery environment. These new discoveries provide clear evidence of rapid, large-scale watery catastrophe consistent with a geologic model based on Noahâ€™s Flood from the Bible.
In 1993, Jocelyn McPhie of the University of Tasmania published a study on the extensive Tennant Creek porphyry formation surrounding Tennant Creek, a small mining town in central Australia.1 She identified peperite texture at the margins of the porphyry sill where it contacts thick sequences of enclosing sedimentary sandstone and siltstone. Her paper provoked responses in the geological literature,2,3 not challenging her interpretation of peperite, but discussing the problem of how the rock formation could possibly have been emplaced within the sediment.