Multi-proxy reconstruction of the burial history and porosity evolution of the TOCA carbonate formation in the Lower Congo basin (South West Africa)

Depicting past stress history at passive margins: A combination of calcite twinning and stylolite roughness paleopiezometry in supra-salt Sendji deep carbonates, Lower Congo Basin, west Africa

“…After 15 Ma, no BPS seems to have developed. The first phase of very active pressure-solution was also documented in the underlying pre-rift and pre-salt Toca Fm (Bah et al, 2023), and it coincides with the first burial phase characterized by the greatest burial rate (Fig. 14).…”

“…the difference in height between two consecutive points separated by a set length of observation, is directly related to stress. Bedding-parallel (sedimentary) stylolites (BPS, hereinafter) have been used as paleopiezometers to constrain the maximum depth of active compaction-related pressure-solution in carbonate rocks (Schmittbuhl et al, 2004, Rolland et al, 2012Koehn et al, 2012;Bertotti et al, 2017;Beaudoin et al 2019;Beaudoin et al, 2020a;Labeur et al, 2021;Bah et al, 2023), leading to recent attempts to time the period at which the vertical stress became lower than the horizontal stress (Beaudoin et al, 2020a,b;Labeur et al, 2021;Lacombe et al, 2021b). This approach relies on the assumption that in a contractional setting, the prime reason that makes a population of BPS stops their development is that the maximum principal stress becomes horizontal.…”

“…Beaudoin et al, 2019;Labeur et al, 2021) even though some local fluid pressure effect might also halt pressure solution at depth (e.g. Bah et al, 2023).…”