The mass extinction at the Triassic-Jurassic boundary (TJB) was one of the five major biotic crises of the Phanerozoic and coincideed with volcanic activity in the Central Atlantic Magmatic Province. The sections from the Budva Basin in Montenegro provide evidence of an abrupt termination of carbonate deposition across the TJB in a deep-water basin located close to a carbonate platform. For the first time, the stable carbon isotope record was measured in a deep-water TJB succession and, also for the first time, the measurements were done in both bulk carbonate and bulk organic matter. We demonstrated that the negative carbon-isotope anomaly and the drastic drop in carbonate (from 90% to less than 10%) occurred at the same time. These new data support the hypothesis that ocean acidification due to increased CO2, SO2 and CH4 fluxes not only promoted carbonate dissolution in the basin but must have also provoked a severe decline of skeletal carbonate-producing organisms on the adjacent platform.
COBISS.SI-ID: 31903277
Mineralogical and chemical analyses of black coatings from two sites in Postojna cave system were studied. Thin sections, powder X-ray diffraction (XRD) technique and scanning electron microscope coupled with energy dispersive X-ray spectrometer (SEM/EDS) were used. The samples were devoid of Mn and Fe oxides or apatite-group minerals that could be a reason for black colouring, but were enriched in organic carbon. However, the source of organic carbon was probably different at different sites. We concluded that, at the entrance to the cave, the main reason for black coatings was the petrol explosion during WW2. In Črna jama, torches of first tourists are the most probable origin of charcoal. On both locations black coatings can be at least partly explained by microclimate conditions at cave entrances, which caused the deposition of organic material of allogenic origin (for example soot due to the forest fires).
COBISS.SI-ID: 924510
In cooperation with Pennsylvania State University and Geological Survey of Norway, research was done on Precambrian, ca 2 billion years old sedimentary and volcanic rocks from north-western part of Russia. Analyses of stable C and O isotopes in both carbonate and organic matter revealed a negative δ13C anomaly with amplitude larger than 10‰. We have interpreted the release of large amounts of light carbon isotope into the ocean and atmosphere due to initial establishment of oxygen-rich atmosphere, in which massive oxydation of organic-rich rocks was enabled for the first time in the history of the Earth. Our data indicate that oxygenation of atmosphere did not occur 2.4 billion years ago as a single event, but rather as a series of events over hundreds of millions of years.
COBISS.SI-ID: 33386285