ABSTRACT

Clinoforms, the basic large-scale architectural form within which sediments are stored and eventually fed down depositional dip in clastic wedges, exist in many shapes and sizes. Understanding how they form, evolve, and degrade is critical to understanding how transport mechanisms affect the shelf margin and sediment partitioning and distribution, and their implications on the presence of a working petroleum system. The Neogene stratigraphic succession of the Taranaki Basin in New Zealand contains clinoform packages that display a variety of architectures well imaged on seismic data. Quantitative characterization of this interval was performed to unravel the processes by which clinoforms evolve under the influence of tectonic- and isostatic-driven subsidence, sea-level change, and sediment supply fluctuations. Nine different clinoform packages were identified on the basis of changes in their seismic stratigraphic characteristics. Two-dimensional stratigraphic forward modeling was used to conduct a sensitivity analysis and determine the relative importance of different geologic controls on their genesis. Our results show that during the early to late Pliocene, clinoform architectures were influenced by the opening of a back-arc rifting structure in the Taranaki Basin (northern graben), which controlled sediment redistribution and partitioning. At the same time, a drop in global sea level allowed sediment bypass to distal parts of the basin. During the late Pliocene, changes in the Australian–Pacific subduction zone forced rapid uplifting of the Southern Alps, generating a significant increase in sediment supply. Model simulations suggest that clinoform architectures during the late Pliocene were controlled by this increase in sediment supply and associated loading.

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