PALEOCEANOGRAPHY, PALEOPRODUCTIVITY AND THE APPLICATION OF NOVEL INORGANIC GEOCHEMICAL PROXIES DURING THE PALEOCENE-EOCENE THERMAL MAXIMUM

• Main Author: Mort, Haydon Peter
• Other Authors: Faculty of Science
• Format: Thesis
• Language: English
• Published: 2002
• Subjects: Antarc*; Antarctica; Carbonic acid
• Online Access: http://hdl.handle.net/10026.2/1924

The Paleocene-Eocene boundary represents a profound event in Cenozoic paleoceanography in which carbon isotope values fell by -2 to -3%o and a 30-50% benthic foraminiferal extinction occurred in just a few thousand years. The Paleocene/Eocene thermal maximum (PETM), occurred approximately 55.5 Ma, and is considered to represent an upheaval in the global carbon reservoir with dramatic consequences recorded in most areas of marine and terrestrial palaeoenvironmental analysis. The proposed cause for such an event centres on the sudden and catastrophic destabilisation of methane hydrates and the release of--2000 gigatonnes of isotopically light carbon into the ocean. In this study the subsequent changes in dissolution, paleoproductivity fluxes and redox states are measured utilising a variety of proxies from three ocean core sites. These are DSD? Site 525 and ocean ODP Sites 690 and 865. Dissolution at the PETM is quantifiably measured in a planktonic foraminiferal fragmentation study. Biogenic barium is calculated in order to infer exogenic productivity at each of the sites and redox sensitive metals are used to show whether any anoxia resulting from hydrate dissociation is detectable. The results from Site 865 and Site 525 suggest a general decrease lysocline depth coupled with an enhancement in productivity flux to the ocean floor. Whilst also seeing a large spike in Babiogenic, ODP Site 690 actually witnesses a reduced level of dissolution. A possible mechanism for this apparent contradiction is therefore offered. This involves the formation of South Atlantic warm saline deep water, reducing the CO2 uptake ability and the subsequent decline in carbonic acid production. Site 525 reveals redox metal spikes at the PETM that appear weaker in the other two sites. It is argued that these spikes may represent changes in bottom water oxygenation states resulting from either or both the increased level of CO2 from hydrate derived CH4 / the enhanced decay of organic matter on the sea floor as a result of increased productivity flux. This study supports previous work that suggests enhanced productivity flux may have sequestered CO2 to ocean floor producing the faster-than-expected recovery in carbon isotope values. Furthermore, the model used to explain a drop in dissolution at Site 690 also offers a possible explanation to the enigmatic warming of Antarctica which climate models have previously struggled to explain.