Reply to the comment by Préat and Weber on Ossa Ossa et al. (2018)
Abstract
We (Ossa Ossa et al., 2018) recently correlated the carbonate succession near Lastoursville (Lastoursville sub-basin) with the FC Formation of the Francevillian Group (mainly defined in the Franceville sub-basin) following Préat et al. (2011). Préat et al. (2011), based on microfacies and chemostratigraphic analysis, included the carbonate successions of Djibalonga (Franceville sub-basin) and Lastoursville-Moukouma (Lastoursville sub-basin) in the FC Formation. In contrast, previous studies (Dunnot and Weber, 1968; Weber, 1968) placed these carbonate successions in the FB2 and FC formations, while noting considerable difficulties with lithostratigraphic correlation between the sub-basins. Bouton et al. (2009) and Thiéblemont et al. (2009) placed the Djibalonga carbonate succession in the FC Formation, while the Lastoursville-Moukouma carbonate succession was only broadly correlated with the FB and FC formations. Préat et al. (2011) observed similar trends in δ13Ccarb values from the two carbonate successions - with positive values in their lower parts and near zero values in their upper parts, interpreted to reflect the end of the Lomagundi Event (LE). We (Ossa Ossa et al., 2018) worked on the same successions and reproduced the same trends. The comment by Préat and Weber (2019), suggesting that the Lastoursville carbonate succession recording the LE correlates to the FB Formation (FB1a-b), is thus highly surprising, as it is in direct conflict with Préat et al. (2011). Préat and Weber (2019) further infer that only the upper FC1 unit as defined by Ossa Ossa et al. (2018) corresponds to the FC Formation, allowing for a single-step deoxygenation event during deposition of the Francevillian Group rather than our proposed two-step deoxygenation event (Ossa Ossa et al., 2018).
- Publication:
-
Earth and Planetary Science Letters
- Pub Date:
- April 2019
- DOI:
- 10.1016/j.epsl.2019.01.013
- Bibcode:
- 2019E&PSL.511..259O