Reply to the comment on 'New insights in the pattern and timing of the Early Jurassic calcareous nannofossil crisis' by M. Clémence, S. Gardin, S. A. Bartolini [Palaeogeography Palaeoclimatology Palaeoecology 427 (2015) 100–108]
| Autor: | Silvia Gardin, Annachiara Bartolini |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
chemistry.chemical_classification
geography geography.geographical_feature_category 010504 meteorology & atmospheric sciences Paleontology Biological pump 010502 geochemistry & geophysics Oceanography 01 natural sciences Seafloor spreading Isotopes of oxygen chemistry.chemical_compound chemistry Sill Paleoclimatology Paleoecology Carbonate Organic matter Ecology Evolution Behavior and Systematics Geology 0105 earth and related environmental sciences Earth-Surface Processes |
| Zdroj: | Palaeogeography, Palaeoclimatology, Palaeoecology. 457:424-427 |
| ISSN: | 0031-0182 |
| DOI: | 10.1016/j.palaeo.2016.05.021 |
| Popis: | In their comment Hermoso and Hesselbo (2015) question i) the temperature control on biocalcification crisis during the Early Toarcian and ii) the interpretation that reduced pelagic calcification led the oceanic carbon pool towards depleted isotopic values. The authors emphasise that the negative CIE recorded during the Toarcian OAE was unlikely caused/enhanced by reduced ballasting of POM to the seafloor because this time interval was characterised by production and accumulation of organic matter. In our reply we point out that the decrease in abundance and size of carbonate producer Schizosphaerella punctulata is stratigraphically consistent with an increasing temperature trend (greenhouse), indicated by the oxygen isotope curve from the onset of the negative CIE sensu Boulila et al. (2014) at around 351 m. This greenhouse climate is interpreted as being linked to the emplacement of the Karoo sill at ~ 183 Ma. The bio-calcification crisis led to a reduced export production and thus to a less efficient CO2 biological pumping that acted as a positive feedback allowing the accumulation of volcanic thermogenic CO2, in the atmosphere/ocean system. This in turn drove seawater isotope DIC towards lighter values that exacerbated the expression of the negative CIE. The reduced carbonate export should not be interpreted as the primary and unique mechanism for highly negative values of the CIE. The T-OAE corresponds to a time of enhanced organic matter deposition but, at the same time, this does not necessarily correspond with an efficient biological pum, especially during the decreasing values of the CIE, when OM accumulation was favoured by preservation rather than by enhanced OM flux to the sea-floor. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect