Anatomy of an unconformity on mid‐Oligocene Amuri Limestone, Canterbury, New Zealand

Abstract

Abstract Data from 50 field localities are used to interpret a middle Oligocene (c. 28–32 Ma) regional unconformity cut into the top of the pelagic Amuri Limestone in the Canterbury Basin of New Zealand. The Amuri Limestone comprises coccolith‐rich foraminiferal biomicrite deposited in an outer shelf to upper bathyal setting on flat‐lying calcareous mudstones and glauconitic sandstones. Prior to deposition of the next succeeding unit, substantial erosion and dissolution variably reduced original thicknesses of up to 70 m and in places totally removed the limestone; locally, differences range from 0 to 10+ m over less than 1 km.