Loading...
Publication
Are marine anoxic events recorded in the late devonian-carboniferous boundary in the south portuguese zone?
| Name: | Description: | Size: | Format: | |
|---|---|---|---|---|
| 11.92 MB | Adobe PDF |
Authors
Advisor(s)
Abstract(s)
The Devonian-Carboniferous Boundary (DCB) marks a mass extinction event that coincided with an oceanic anoxic event recognized worldwide. The stratigraphic sequence of the Pedra Ruiva sea cliff in the South Portuguese Zone near the Bordeira village dates back to the end of the Devonian and the start of the Carboniferous periods. To date, no study has been conducted to investigate the presence of oceanic anoxic events at this location during the DCB. Twenty rock samples were collected and analyzed from two outcrops from the Pedra Ruiva sea cliff. This thesis aims to identify and describe any anoxic event in this area. The results showed that during the DCB, the Southern Outcrop went through a decrease in the CIA values. An abundance of SiO₂, changes in the ratio of V/Cr, as well as an increase in the abundances of the heavy metals V, Cr, U, Al₂O₃, and the ratio of V/(V+Ni) were also observed. The Northern Outcrop does not show the same relation between the DCB and the calculated values and abundances. However, it does show a major spike in the CIA values after the DCB that corresponds to an increase in the V/C and V/(V+Ni) ratios, an abundance of SiO₂ and a decrease in Al₂O₃.The sedimentary facies of the two outcrops indicate that the proxies used to detect OAEs were deposited in non-ideal conditions for their preservation. Due to this the findings do not provide a definitive answer; however proxies indicate that a study in the more northern portions of the Tercenas Formation may yield better results.
Description
Keywords
Marine anoxic Sedimentary fácies Sea