Kaiho et al. (2013) showed that high values of organic molecule indices of combustion, soil erosion, and euxinia occurred at the Frasnian-Famennian transition at Sinsin, Belgium. Marynowski and Racki (2014) commented on the paper. Their issues mainly address (1) the low resolution of the data, (2) the reliability of the proxies, (3) weathering as a cause of the peaks of the proxies, (4) the discrepancy between rare charcoal occurrence and the high combustion proxy, and (5) the stepwise collapse of the huge global reef ecosystem ending well before the F-F boundary. In response to comment (1), the positive excursion of δ13Ccarb marking the F-F transition in the Sinsin section indicates that the Sinsin section has enough strata to detect environmental changes during the culmination of the Late Devonian stepwise mass extinction. On comment (2): soil erosion was indicated not only by dibenzofuran but also by a spike of cadalene. Dibenzothiophene should have increased when euxinic water developed on the surface of sediments, which is supported by the coincidence of isorenieratane and dibenzothiophene on the middle shelf in the late Permian. We show the combustion index at the Cretaceous-Paleogene transition, indicating that this ratio is useful as a proxy of combustion. On comment (3): we cannot explain the high and low combustion, soil erosion, and euxinia index values by weathering because of the consistently well-preserved state of the rock samples. On comment (4): we need to detect charcoal during the F-F transition and early Famennian, corresponding to maxima of high sea levels, to clarify the discrepancy. On comment (5): our model is only for the F-F transition event marked by the extinction acme; it may not explain the collapse of the reef ecosystem that ended before the F-F boundary, but it can explain the extinction acme at the F-F transition.
- Mass extinction
- Polycyclic aromatic hydrocarbons
- Soil erosion
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Earth-Surface Processes