Diagenetic Implications of Stylolitization In Pelagic Carbonates, Canterbury Basin, Offshore New Zealand

Abstract

Stylolites are irregular discontinuity surfaces that are thought to result from localized stress-induced dissolution during burial or tectonic compression. The genesis of stylolites and the controls on stylolitization are still debated, and the interplay between stylolitization, generation of carbonate-rich fluids, diagenetic fluid flow within fractures and matrix, cementation, and porosity modifications is complex. All of these processes have important diagenetic effects potentially altering the intrinsic properties of the host rock, with implications for hydrocarbon exploration and water resources in aquifers. We investigate the process of stylolitization by a macroscopic, petrographic, and geochemical study of pressure-solution features in Eocene to early Oligocene limestones in cores from the Integrated Ocean Drilling Program (IODP) Hole 317-U1352C (Canterbury Basin). The results indicate correlations among stylolite amplitude, stylolite density, and siliciclastic content of the host rock. These relationships are interpreted to suggest that siliciclastic content in carbonate rocks increases heterogeneity, which in turn impacts stylolite nucleation. Moreover, the geochemical data support that clay along the stylolite is not authigenic, but a relict from impurities in the limestone host rock. The statistical approach of stylolite spacing used in this study, which is different than previous studies, reinforces the model of random occurrence of stylolites in (carbonate) lithologic units.This study shows that local stresses in tectonically passive areas may allow the formation of rare oblique stylolites with peaks perpendicular to the stylolite plane. Estimation of the amount of limestone dissolved during stylolitization (minimum 7% to 12% of the depositional limestone) and the volume of sparite in the host rock (up to 1.6% of the compacted limestone) suggests that the pressure-solution fluids cemented the micropores, reducing porosity to about 10% (from a common porosity of about 40% in mechanically compacted chalk). This study thus highlights the importance of microporosity as a sink for burial cements, an observation difficult to make in thin-section. Analysis of stylolite infills at Site U1352 shows no evidence that the stylolites acted as conduits for diagenetic fluids, unless if the fluid was host-rock buffered and thus its chemistry indistinguishable from that of the host rock.The link between siliciclastic content in carbonate rocks and the spacing and amplitude of stylolites improves understanding of burial compaction processes. Predicting the morphology and spacing of stylolites in the subsurface can be used to identify baffles to cross-stylolite fluid flow or cementation (of microporosity) influencing heterogeneity of petrophysical properties in (subsurface reservoir) host rocks.

The Transformation of Sediment Into Rock: Insights From IODP Site U1352, Canterbury Basin, New Zealand

“…They noted that siliciclastic mud content affects the nature of pressure solution, ranging from serrated stylolites in more pure limestones to nonsutured seams and wispy seams in more "dirty" limestones. This is what we see at Site U1352, where well developed stylolites are present only near the base of the hole below 1600 m. These have been described in some detail by Vandeginste and John (2013). Below 1852 m (Unit III), the lithology is a foraminiferal micritic limestone with clay minerals concentrated in stylolites (offshore equivalent of the Amuri Limestone).…”

Comparison of the diagenetic and reservoir quality evolution between the anticline crest and flank of an Upper Jurassic carbonate gas reservoir, Abu Dhabi, United Arab Emirates

“…33 peloids and dissolution of aragontic skeletal fragments in the shallower burial regime, and stylolitization in the deeper burial regime (Oswald et al, 1995;Neilson et al, 1998;Fabricius and Borre, 2007;Vandeginste and John, 2013;Paganoni et al, 2016), or both. The mass released from stylolitization would presumably diffuse and reprecipitate within a few meters away from stylolites .…”

Bedding-parallel stylolites as a tool to unravel maximum burial depth in sedimentary basins: Application to Middle Jurassic carbonate reservoirs in the Paris basin, France

“…Since stylolites are features that form during chemical compaction, which is a function of the sediment overburden and since the tooth flanks are parallel to maximum the principal compressive stress, the stress clearly plays a key role in the formation of these features. In carbonates, the type of facies (chiefly dependent on depositional texture, primary mineralogy and abundance of allochems, mud and pores), the morphology (Andrews and Railsback, 1997), the presence of clays and organic matter, as well as the vertical heterogeneity of the strata and the applied stress are the main parameters that govern stylolitization (Shinn and Robbin, 1983;Bathurst, 1987Bathurst, , 1991Aharonov and Katsman, 2009;Koehn et al, 2012;Vandeginste and John, 2013;Koehn et al, 2016). Today still, assessing the mechanisms that govern BPS development as well as the quantification of the stress experienced by the stylolite host rock are key points to understand sedimentary basin evolution aiming at improving geological simulations at both the basin and the reservoir scales (Braithwaite, 1988;Andrade Ramos, 2000;Gratier et al, 2005;Peacock and Azzam, 2006; Baron and Parnell, 2007;Benedicto and Schultz, 2010;Angheluta et al, 2012;Koehn et al, 2012;Heap et al, 2013;Khair et al, 2013Khair et al, , 2015Baud et al, 2016;Bertotti et al, 2017).…”