Geochemical, petrographic, and uranium-lead geochronological evidence for multisourced polycyclic provenance of deepwater strata in a hybrid tectonic setting: The upper Miocene upper Mount Messenger Formation, Taranaki Basin, New Zealand

摘要

Petrographic, detrital zircon, major, trace, and rare earth element data from the deep-water slope upper Miocene upper Mount Messenger Formation, Taranaki Basin, New Zealand have been characterized to examine their provenance, tectonic setting, grain size, and source-to-sink implications. Sandstone samples have an average quartz-feldspar-lithic framework composition of Q(37)F(9)L(54). Lithic fragments are metasedimentary and commonly quartz and epidote bearing, having been recycled through at least two phases of erosion and deposition from an original orogenic to transitional arc setting. Detrital zirconU-Pb ages (total 304 single-grain ages) range from 37 to 2466 Ma, with large Triassic to Permian modes and small mid-Cretaceous, Early Jurassic, Devonian-Ordovician, Cambrian, and Proterozoic modes. The ages show subtle variation from the base to the top of the formation and statistical similarity with the Torlesse composite terrane and Waipapa Group. Trace and rare earth element analyses indicate enrichment in Th and Zr compared with Sc and Cr, and a strong Eu anomaly. The depositional system is over-whelmingly fine-to very fine-grained and probably reflects grain recycling andmechanical breakdown, either through an intermediate depositional cycle or derived directly from metasedimentary basement sources. Basement sources appear to be primarily the Torlesse composite terrane (Rakaia, Pahau, and Kaweka terranes) and Waipapa Group located east and southeast of the study area. This study documents source-to-sink elements in a profoundly regressive depositional system within an active margin setting. It also contributes new information on the composition and depositional history of a stratigraphic interval that contains important petroleum reservoirs in the nearby subsurface.