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

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.