Facies Architecture and Reservoir Quality of Miocene Mt. Messenger Deep-Water Deposits, Taranaki Peninsula, New Zealand

Abstract

The Mt. Messenger Formation exposed along the coastline of the Taranaki Peninsula contains flat-laminated, very-fine to fine-grained sands inlerbedded with bioturbated silt and silty claystone. These beds are typically over 5 cm thick and are the result of high-velocity turbidity currents which allow for good textural sorting and preservation of excellent reservoir-quality sands. Beds less than this thickness, as well as upper parts of many turbidites, typically contain features suggesting reworking, winnowing, and remolding by bottom currents. This winnowing effect is responsible for the good to excellent reservoir properties of the thin, poorly consolidated, well-sorted, very fine-grained lithic arenites. Mt. Messenger sands were deposited on a depositional slope in lower to upper bathyal water depths which was the site for these transforming bottom currents. The Mt. Messenger overlies Mohakatino, Ferry, and Tawariki sandstones and siltstones which were the initial deepwater sediments in the basin. These sandstones are lithic-rich and fine to medium-grained. The beds are typically massiveappearing but locally contain dewatering features, typical ‘classic’ turbidites (graded beds, slurry or low-density turbidity current tops), and were deposited as thick sheet-like bodies on the basin floor. Winnowing of the sandstones did not take place on a large scale and hence reservoir quality is invariably poor to moderate. The mica stilpnomelane in the sands is common; this mineral is restricted areally to low-grade regionally metamorphosed sediments and associated veins, most notably to the schists of western Otago, New Zealand, on the northwestern part of the south island The occurrence of this mineral has important implications as to the source of the Mt. Messenger sediments in the North Taranaki area (transport was from south to north from the South Island).

Cyclicity in turbidites of the Miocene Whakataki Formation, Castlepoint, North Island, and implications for hydrocarbon reservoir modelling

“…2). Fine-grained thin-bedded deep-water sediments are important hydrocarbon reservoirs globally (DeVries & Lindholm 1994;Shew et al 1994;Bramlett & Craig 2002), as well as in the New Zealand context in the Taranaki Basin (King et al 1994;Browne et al 2000) and the East Coast region of the North Island (see below).…”

Grain‐size characteristics for distinguishing basin floor fan and slope fan depositional settings: Outcrop and subsurface examples from the late Miocene Mount Messenger Formation, New Zealand

“…Physical sedimentological features differ between basin floor fan and slope fan deposits within the Mount Messenger outcrop and these features have been reviewed elsewhere King et al 1994;Browne et al 1996Browne et al , 2000Browne & Slatt 2002). Salient features are summarised below and presented in Table 1.…”

“…In these stratigraphically lower depositional cycles, basin floor fan units dominate each 4th-order cycle. Toward the south of the outcrop section, basin floor fan units give way to slope fan deposits that are c. 300 m thick (King et al 1994;Browne et al 1996Browne et al ,2000Browne & Slatt 2002).…”

“…Basin floor fan lithofacies of the Mount Messenger Formation comprise thick-bedded (>30 cm thick) and thin-bedded (<30 cm thick) alternating sandstone and siltstone lithofacies King et al 1994;Browne et al 1996). In both thick-bedded and thin-bedded lithofacies, sandstones comprise moderately to well-sorted, fine to very fine grained beds, commonly with isolated pebble-sized (or larger) clasts of contemporaneous siltstone (Fig.…”

“…The Mount Messenger Formation consists of a c. 700 m thick succession that forms a northwest-progradational package and includes numerous 4th-order (100 000-300 000 yr) sedimentary cycles (King et al 1994;King & Thrasher 1996). The Mount Messenger Formation crops out over a 20 km length of coastline in North Taranaki (Fig.…”