Sub-Millennial Anatomy of Late Miocene Deep-Water Mass-Transport Deposits: Case Studies of the Use of Foraminifera to Decipher the Stratigraphic Architecture of the Mount Messenger Depositional System, Taranaki Basin, New Zealand

Martin P. Crundwell and Malcolm J. Arnot
GNS Science, Lower Hutt, New Zealand

The Mount Messenger Formation represents a highly dynamic deep-water system comprising slope to basin floor fan deposits that form stacked 4th to 5th order cycles deposited over timescales of 20-100 kyr. The Late Miocene sedimentary patterns reflect a complex history of shelf progradation, tempered by sediment supply and accommodation, and tectonic controls within and adjacent to the basin. The variable stratigraphic and sedimentological character of the system poses problems for petroleum exploration, because rapid lateral and vertical variation in facies make it difficult to correlate, date and predict the spatial distribution of intervals containing potential reservoir facies.

In this presentation, we outline the application of new high-resolution biostratigraphic data and tools that have been developed by GNS Science to address correlation problems associated with this interval. Extremely high estimated rates of sedimentation are recognised at times within the Mount Messenger succession, based on sub-millennial-scale dating derived from weight-standardised counts of planktic and benthic forams and a non-linear age interpolation method. Intervals of downslope reworking are also recognised using dynamic facies analysis based on minimum paleodepth data. When applied in combination, the new biostratigraphic tools provide a robust temporal and paleoenvironmental framework that enables the stratigraphic architecture of Late Miocene depositional systems to be correlated between wells at a greater level of precision than previously. This has shown that reservoir-quality base of slope sands, the primary Mount Messenger exploration play, are confined to overlapping fan-lobes.

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas