Burnt Creek Formation and Late Cretaceous basin development in Marlborough, New Zealand

Abstract

Burnt Creek Formation is a Cretaceous sedimentary unit that has been identified from a restricted geographic area southeast of the Ouse Fault in the Coverham-Kekerengu valley region, Marlborough. It comprises a fining-upwards succession of conglomerate, pebbly mudstone, sandstone, sandstone-siltstone couplets, siltstone, and contorted beds. Coarser beds are inferred to have been deposited by a range of submarine sediment gravity-flow processes, in particular debris flows and turbidity currents, in an outer neritic or upper bathyal environment. Burnt Creek Formation was deposited during the Mangaotanean and Teratan ages (middle Turonian—early Santonian). Older parts of the formation occupy a small (c. 1 km across), east—west or northeast—southwest trending, asymmetric basin. They record onlap of an incised valley or deposition adjacent to a synsedimentary fault that was downthrown to the north. The Ouse Fault is inferred to have been a major normal fault during the Clarence Epoch (Albian—Cenomanian) and for at least part of the Raukumara Epoch (Cenomanian— Santonian). Regional extension in Marlborough is suggested also by the presence of Ngaterian (latest Albian — late Cenomanian) and probable Teratan (early Coniacian — early Santonian) intraplate, alkaline basalts. In the Miocene the Ouse Fault was reactivated as a reverse fault, and crustal shortening of perhaps several kilometres juxtaposed the Cretaceous successions now found on either side of the fault. © 1997 Taylor & Francis Group, LLC.