Diagenesis of polymineralic temperate limestones in a cyclothemic sedimentary succession, eastern North Island, New Zealand

Abstract

Temperate carbonate petrofacies (calcarenite and coquina) in the Pliocene-Pleistocene Petane Group of eastern North Island, New Zealand, are dominated by aragonite faunas consisting primarily of bivalves and gastropods. Unlike calcite-dominated temperate limestones, these polymineralic carbonates have undergone extensive early diagenetic alteration including extensive calcite cementation induced by aragonite dissolution. Marine cementation (type 1: pore-lining, bladed calcite) was isolated to biogenic pores. It predated glauconite and may have been precipitated as lowmagnesium calcite, possibly in marine phreatic environments during sea-level transgressions. Four phases of calcite cement with varying but definitive degrees of meteoric influence occur in the Petane Group. Type 2 (ferroan scalenohedral calcite) was the initial pore-filling cement and precipitated from reduced pore fluids in a phreatic environment, possibly during or soon after the transition from marine to meteoric diagenesis. Type 3 (moderately ferroan drusy) calcite and type 4 (non-ferroan drusy) calcite were sequentially precipitated during meteoric conditions from pore waters that changed from reducing to oxidising. Type 5 (sinter) cements comprise several forms precipitated during vadose meteoric diagenesis, the final meteoric phase of alteration in the Petane Group. Ferroan calcite cementation of silt matrix in coquina limestones overlain by terrigenous silt (type 6: matrix cement) probably occurred simultaneously with type 2/3 pore-filling phases. A similar ferroan to moderately ferroan to non-ferroan suite of drusy calcite cements also lithified concretions in non-carbonate (siliciclastic sand) facies in the Petane Group, but only after the onset of compaction. Extensive skeletal diagenesis (stabilisation of magnesium calcite allochems, dissolution/recrystallisation of aragonite) occurred during type 3 and 4 cementation phases. Diagenesis in the Petane Group was stratigraphically influenced and ultimately controlled by uplift. Alternating sequences of porous and non-porous formations developed a stacked sequence of confined aquifers that forced carbonate diagenesis to operate laterally.

Unveiling the Geological Significance and Industrial Application of Limestone: A Comprehensive Review

“…The composition and texture of limestone deposits can be further altered by diagenetic processes such as recrystallisation, cementation, and dolomitisation (Ganai, Rashid and Romshoo, 2018). Larger crystals are formed, and the original sedimentary textures are destroyed through the process of recrystallisation, which is the dissolution and reprecipitation of calcium carbonate minerals (Haywick, 2004). Secondary minerals like silica or calcite precipitate to fill pore spaces and bind sedimentary particles together, causing cementation.…”

Contrasting mixed siliciclastic-carbonate shelf-derived gravity-driven systems in compressional intra-slope basins (southern Hikurangi margin, New Zealand)

“…Conversely, at Homewood, the occasional sandy shell beds could be contemporaneous with the development of the shelfal environment. Early lithification of the deposits at or near the seafloor may have been triggered by increased saturation of seawaters with respect to CaCO3, following partial dissolution of aragonitic turritellid shells, though such process has been documented to predominantly result from burial diagenesis (i.e., mesodiagenesis) (Nicolaides 1995;Haywick 2004;Caron and Nelson 2009).…”

Missing Aragonitic Biota and the Diagenetic Evolution of Heterozoan Carbonates: A Case Study from the Oligo-Miocene of the Central Mediterranean

“…The diagenetic evolution of heterozoan carbonates (sensu James 1997) has recently become of interest (e.g., James and Bone 1989;Hood and Nelson 1996;Nicolaides and Wallace 1997b;Brachert and Dullo 2000;Haywick 2004). The heterozoan association, in contrast to the photozoan, consists mainly of light-independent biota such as mollusks, bryozoans, and echinoderms, with only minor amounts of light-dependent taxa such as calcareous red algae.…”