The record of the early Toarcian and early Aptian oceanic anoxic events in the Apenninic Carbonate Platform (Southern Italy)

• Main Author: Trecalli, Alberto
• Format: Doctoral or Postdoctoral Thesis
• Language: Italian; English
• Published: 2011
• Subjects: Carbonic acid; Ocean acidification
• Online Access: http://www.fedoa.unina.it/8548/; http://www.fedoa.unina.it/8548/1/Trecalli_Alberto_24.pdf; https://doi.org/10.6092/UNINA/FEDOA/8548

About one third of the carbon dioxide released mainly from burning of fossil fuels is absorbed into the oceans where it reacts to form carbonic acid. As a result the pH of the ocean and the amount of carbonate ions decrease in a process called ocean acidification. Detrimental effects on calcifying organisms, which use carbonate minerals to build their protective shells and skeletons, have been documented in the laboratory and in the field. However, due to the spatio-temporal limits of experiments and field observations, the long-term impact on marine ecosystems and the adaptation potential of marine species are best investigated by looking at the geological record of past episodes of ocean acidification. Episodes of short-term massive injection of CO2 in the atmosphere-ocean system are witnessed by negative carbon isotope events (CIE) recorded by marine carbonates and by marine and continental organic matter. Paroxysmal volcanism and/or clathrates dissociation are generally invoked as the source of isotopically depleted excess CO2. High pCO2 is also held responsible for the dramatic increase of atmospheric and seawater temperature. During the Mesozoic some of these events record also the deposition of large amounts of organic carbon in epicontinental and oceanic basins, witnessing widespread marine anoxia. For this reason they are commonly referred to as Oceanic Anoxic Events (OAEs). The early Toarcian (Posidonienschiefer event, T-OAE, 183 Ma) and early Aptian events (Selli event, OAE1a, 120 Ma) represent two of the most severe and best documented episodes of sudden perturbation of the global carbon cycle and therefore have been chosen as subject of this thesis. There is overwhelming evidence for both the events that geologically rapid injection of CO2 into the ocean-atmosphere system caused abrupt global warming. Ocean acidification has also been proposed for both the events. Most of what we know about the record of the early Toarcian and early Aptian events has been revealed by the study of relatively ...