ABSTRACT: Sedimentation and Structural Styles Adjacent to an Obliquely Convergent Plate Margin: the Neogene of Marlborough, New Zealand

BROWNE, G.H., DSIR Geology and Geophysics, Christchurch, New Zealand

The Neogene of Marlborough forms part of a siliclastic dominant succession, ranging in age from the early Miocene (Aquitanian) to late Pliocene (Piacenzian). The range of Neogene rock types is varied and locally is >2.5 km thick. They include siltstone, silty sandstone, flysch, debris flow, and deep-water submarine mass flow conglomerate and locally fluvial conglomerate. Source areas include Mesozoic, Cretaceous, and Paleocene rocks to the west in central Marlborough.

Sedimentation was contemporaneous with active folding about northeast-trending axes, southwest- and west-directed thrusting, folding and uplift at restraining bends, right lateral strike slip movement along several major fault systems, and possible right lateral rotation of fault blocks. Shortening across the region has probably amounted to 50-70% since the early Miocene. In addition, some fault blocks have been tectonically juxtaposed from the east by movement along listric fault decollements.

The significance of the Neogene of Marlborough in terms of petroleum geology is in providing sufficient burial depths for Cretaceous-Paleocene source rocks, and in understanding the structural complexities that these rocks have undergone as a result of the Neogene Kaikoura orogeny. Prospective areas in the offshore of Marlborough may be less affected by the styles of tectonic deformation observed on land.

AAPG Search and Discovery Article #91015©1992 AAPG International Conference, Sydney, N.S.W., Australia, August 2-5, 1992 (2009)