THE WARDER FORMATION - CYCLIC FLUVIAL SEDIMENTATION DURING THE NGATERIAN (LATE ALBIAN CENOMANIAN) OF MARLBOROUGH, NEW-ZEALAND

The Warder Formation of Ngaterian (late Albian-Cenomanian) age crops o ut in southern Marlborough, New Zealand. Outcrops are characterised by fining-upward alluvial cycles deposited by easterly flowing rivers on a coastal plain. Within-channel deposits include clast-supported cong lomerate and trough cross-bedded sandstone, overlain by alternating sa ndstone and siltstone, lateral accretion (inclined heterolithic strati fication) beds, in turn overlain by siltstone and claystone. The fine- grained units are interpreted as lacustrine sediments deposited in ox- bow lakes through meander loop cut-off. All outcrops are fault bounded , so a complete pattern of fluvial reconstruction cannot be made. The rivers which deposited the Warder Formation had a mean sinuosity of 1. 5 and a discharge of 72-102 m3/s. Sedimentation was terminated by the eruption of alkaline basalts related to regional sea-floor spreading.