The origins and transformation of carbonate mud during early marine burial diagenesis and the fate of aragonite: A stratigraphic sedimentological perspective

Diagenetic Evolution of Upper Cretaceous Kawagarh Carbonates from Attock Hazara Fold and Thrust Belt, Pakistan

“…In Kawagarh, mechanical compaction indicated by the skeletal particle rearrangement, breakage, deformation, and close contacts suggests burial depths of up to 100m. Mechanical compaction always shows greater signals in granular facies as the bigger grains take the first impact of the compaction, whereas the absence of preferred orientations and the neomorphism of intact grains supports how cementation took place before compaction [15]. Sutured skeletal particles contact and stylolite is clear evidence of pressure solutioning (chemical compaction) on depths >300 m and is indicative of the onset of burial diagenesis.…”

“…Despite the insufficient pressure and temperature condition, Munnecke suggested that strong geochemical gradients can be achieved by microbial decomposition of organic matter [77] in shallow burial environments which may dissolve and reprecipitate carbonates. According to [15,76,78], the pore fluid originated from the interlayer marls beds by the dissolution of aragonite, and then it was transported to the adjacent limestone bed where it was reprecipitated as LMC (microspar). Lately, a series of studies [78][79][80][81] led to a limestone-marl layer alternations model which is based on this diagenesis postulate that selective dissolution of aragonite in marl/limemud/shale beds and reprecipitation of calcite cement in limestone beds can result in a bed differentiation which can be confusing with the depositional cyclicity.…”

“…The marine environments are the main source of carbonate deposition where the diagenesis is predominantly influenced by the supersaturated marine pore fluids. Ideal conditions are present in marine environments for the precipitation of calcite cement during the fluid percolation through the pore system [12,14,15]. The precipitation of new mineral phase and/or replacement of existing mineral phase by enriched fluids can bring unprecedent changes and can produce highly complex carbonate fabric and pore systems.…”

Coring tools have an effect on lithification and physical properties of marine carbonate sediments

“…Thereby, a solid matrix originates, which binds together the grains. Cementation can manifest in different forms: (1) the presence of cements that provide insights into the depositional or diagenetic environment (Friedman, 1964;Bathurst, 1972Bathurst, , 1974Bathurst, , 1980Flügel, 1982); (2) the transformation of mud into micrite during early diagenesis, a process known as micritization (Folk et al, 1965;Munnecke, 1997;Munnecke et al, 2023); (3) late diagenetic transformations such as pressure dissolution (Moore and Wade, 2013); (4) dolomitization, during which dolomite replaces the original mineral composition (Budd, 1997;Mckenzie and Vasconcelos, 2009;Mavromatis et al, 2014;Reuning et al, 2022); and (5) the diagenetic transformation of any of the four cases mentioned (Harris et al, 1985). Lithification and cementation modify the physical properties of the sediment, including porosity, density, and P-wave velocity (Fabricius, 2003).…”

“…Doing so becomes exceedingly complicated as several aspects of lithifying carbonate sediments are still not understood. Especially the early diagenetic transformation of soft sediments into solid rock remains enigmatic (Reid et al, 2000;Nohl et al, 2021;Tagliavento et al, 2021;Reuning et al, 2022;Munnecke et al, 2023). What can be inferred is that the microbial decay of organic matter causes variable geochemical gradients impacting porewater alkalinity and pH, which leads to the dissolution of aragonite and a reprecipitation of CaCO 3 as calcite cement (Froelich et al, 1979;Berner, 1980;Munnecke and Samtleben, 1996;Soetaert et al, 2007;Wurgaft et al, 2019;Reuning et al, 2022).…”