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

Abstract

Outcrop data indicate that basin floor fan sandstones are relatively sand rich in comparison to silt-rich slope fan sandstones. Both basin floor and slope fan sandstones show better sorting with increasing grain size, though cross-plots show the nature of this relationship differs slightly for basin floor and slope fan samples. These relationships appear to hold for both outcrop and subsurface sandstone samples from the formation. This finding is unexpected given the c. 600 m stratigraphic thickness of the formation, representing several million years of depositional history, and implies a uniform sediment texture was supplied to the basin through time.The differentiation of basin floor fan and slope fan deposits is significant especially in subsurface settings involving petroleum well data. Hydrocarbon exploration strategies will vary markedly for basin floor fan versus slope fan reservoirs, making such differentiation of lithofacies types important to optimise hydrocarbon discovery. With subsurface data, the interpretation of these two reservoir sandstone lithofacies is often difficult to make. The grain-size changes appear to mimic the contrasting depositional mechanisms operative in these two deep-water settings.

A New Method For Interpolating Ages Between Calibrated Control Points Based On Foraminiferal Concentrations

“…6) are mainly developed in the intervals where sedimentation rates are lower, and that the muddier intervals correspond to the most rapidly deposited parts of the section. This is consistent with outcrop and subsurface data compiled by Browne et al (2005), which shows slope fan sandstone of the upper Mount Messenger Formation to be siltier than the basin-floor-fan sandstone of the lower Mount Messenger Formation that have been transported a greater distance, and have therefore been subjected to a higher degree of hydraulic sorting and winnowing.…”

“…The Miocene section in this well includes a basin-floor succession of predominantly hemipelagic mudstone between 1459 m and 1020 m (Manganui Formation); an aggradational inner to middle basin-floor fan succession of redeposited sandstone and hemipelagic mudstone between 1020 m and 830 m (lower Mount Messenger Formation); and a progradational slope fan succession of redeposited sandstone and siltstone with major contributions of inherited productivity from mid bathyal and shallower water depths (upper Mount Messenger Formation) (Crundwell 2002;Browne et al 2005;Arnot et al 2007a). Each formation is separated by a hiatus.…”

New Zealand Carbon Dioxide Storage Site Assessment: Phase 1

“…Mount Messenger Formation slope fan sandstone beds in both subcrop and outcrop consist of litharenites and feldspathic litharenites ( Figure 19) (Browne et al 2005). The composition of both outcrop and subsurface examples, of both basin floor fans and slope fans are remarkably similar throughout the onshore Taranaki Peninsula region.…”

“…Feldspar is dominantly monomineralic plagioclase, which is variably degraded and locally sericitic. In both outcrop and subcrop samples there is little or no cement and relatively little diageneitc alteration (Jordan et al 1994;Browne et al 2005). Mineral cements are typically minor.…”

Advances in grain-size, mineral, and pore-scale characterization of lithic and clay-rich reservoirs

“…The sandstones are very fine-to fine-grained and poorly indurated. They have litharenite to feldspathic litharenite compositions (Martin, 1989(Martin, , 1990(Martin, , 1992(Martin, , 1993(Martin, , 1994(Martin, , 1995aBrowne et al, 2005) indicative of a metasedimentary provenance (King and Browne, 2001), and thus are ideally suited for reservoir characterization of a mineralogically complex succession.…”