Bedding-parallel stylolites in shallow-water limestone successions of the Apulian Carbonate Platform (central-southern Italy)

Abstract

Bedding-parallel stylolites typically represent the product of chemical compaction (overburden weight-induced pressure solution) experienced by carbonate successions during their burial history, when bedding is still horizontal. Due to their common occurrence in carbonate rocks, with lateral extents that can exceed 1 km, beddingparallel stylolites are of special interest for the hydrocarbon industry because they may affect the regional fluid flow in the subsurface. Aimed at assessing the development and distribution of beddingparallel stylolites in shallow-water, platform limestone successions, field and laboratory studies were carried out on Cretaceous limestones originally pertaining to the Apulian Carbonate Platform realm and now exposed in three distinct Italian locations: Maiella Mountain, Gargano Promontory and Murge Plateau.Results point to a prominent role played by the geological characteristics of limestones on development and localization of beddingparallel stylolites within shallow-water, platform limestone successions. In particular, bedding-parallel lamination and fine rock grain size, co-occurring in stromatolitic limestones, determined there laterally more extensive and closely spaced stylolites than in the associated calcilutites and calcarenites. Large fenestral pores, which are ubiquitous in stromatolitic limestones, represent rock heterogeneities able to influence the roughness of individual stylolites.Laboratory measurements revealed that the permeability of the studied Cretaceous limestones is very low (<10 µD). Pilot tests suggest that bedding-parallel stylolites in stromatolitic layers are not barrier to fluid flow but may represent pathways through low-permeability, platform limestone successions in the subsurface.

The permeability of stylolite-bearing limestone

“…Stylolites are planes of insoluble minerals that form in rocks as soluble minerals are removed by pressure solution (e.g., Park and Schot, 1968;Wanless, 1979;Nenna and Aydin, 2011;Croizé et al, 2013;Toussaint et al, 2018). They are common in limestones due to the relatively high solubility of calcite (e.g., Tondi et al, 2006;Fabricius and Borre, 2007;Benedicto and Schultz, 2010;Smith et al, 2011;Rustichelli et al, 2012;Agosta et al, 2012;Laronne Ben-Itzhak et al, 2014;Rustichelli et al, 2015;Martín-Martín et al, 2018), but are also found in sandstones (Heald, 1955;Walderhaug, 1996;Bjørkum et al, 1998;Walderhaug and Bjørkum, 2003;Emmanuel et al, 2010).…”

“…Due to their macroscopically planar form, the influence of stylolites on fluid flow and reservoir compartmentalisation has drawn considerable interest. A handful of experimental studies have shown that stylolites can provide conduits for flow (Lind et al, 1994;Mallon and Swarbrick, 1998;Heap et al, 2014;Rustichelli et al, 2015), challenging paradigms that stylolites present barriers to fluid flow (Dunnington, 1967;Nelson, 1981;Burgess and Peter, 1985;Koepnick, 1987;Finkel and Wilkinson, 1990;Dutton and Willis, 1998;Alsharhan and Sadd, 2000). Heap et al (2014), for example, measured the permeability of limestone samples that contained no stylolites, one stylolite perpendicular to the imposed fluid flow, or one stylolite parallel to flow.…”

Stylolitic limestone, the stone of choice for ancient sanctuaries and temples, southwestern Peloponnese, Greece

“…Rustichelli et al. () documented the abundance of bedding‐parallel stylolites and pseudo‐bedding in Cretaceous limestone in the southern Appennines. These rocks crop out abundantly on the Gargano Promontory and the Murge Plateau, both bordering the Adriatic Sea.…”

“…At Monte Sant'Angelo Castle on the Murge Plateau, the Giant's Tower (Torre dei Giganti, constructed in 837) may be a candidate for the pseudo‐bedded limestone described by Rustichelli et al. ().…”

Fault‐controlled dolomite bodies as palaeotectonic indicators and geofluid reservoirs: New insights from Gargano Promontory outcrops

“…As bedding-parallel stylolites and stratabound joints and veins typically form during burial (Fig. 14;Bathurst, 1995;Agosta et al, 2009;Rustichelli et al, 2012Rustichelli et al, , 2015bRustichelli et al, , 2016, remnants of such features indicate that the limestones had a significant overburden at the time of dolomitization (at least 90 to 300 m; e.g. Tada & Siever, 1989;Ebner et al, 2009).…”