Allostratigraphy of coastal south and east Otago: A stratigraphic framework for interpretation of the Great South Basin, New Zealand

Abstract

Sixteen unconformities, some with correlative conformities, are recognised within the Late Cretaceous-Tertiary transgressive-regressive sediments of coastal Otago. These provide the basis for stratigraphic division and correlation with seismic reflectors in the offshore age-equivalent sediments of the Great South Basin. The ages of the unconformities/conformities are constrained mainly by dinoflagellate biostratigraphy, but foraminiferal biostrati-graphy is important for the Oligocene—Miocene. In terms of current biozone-stage correlation, the 16 unconformities comprise the following: two intra-Haumurian (Late Cretaceous) unconformities, one at the K/T boundary, three intra-Teurian (Paleocene) unconformities, two of early Waipawan age, two of late Mangaorapan — early Heretaungan age, a late Heretaungan unconformity, a late Porangan - early Bortonian unconformity, a late Bortonian unconformity (a total of seven Eocene unconformities), a late Runangan - early Whaingaroan unconformity, a late Whaingaroan unconformity (both Oligocene), and a mid-Waitakian (Miocene) unconformity. Other, early—mid-Cretaceous unconformities are inferred from offshore seismic profiles. Six unconformities/correlative conformities in onland Otago provide the basis for recognising four informal alloformations. © 1997 Taylor & Francis Group, LLC.