The Miocene Carbonate crash: Shifts in carbonate preservation and contribution of calcareous plankton
This thesis documents sedimentary changes in the middle to late Miocene of the Atlantic and Pacific Ocean basins. This time interval known as the carbonate crash interval (12-9Ma) displays a severe perturbation of the carbonate system in the framework of the major Cenozoic cooling accompanied by cha...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Universität Bremen
2010
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| Online Access: | https://media.suub.uni-bremen.de/handle/elib/215 https://nbn-resolving.org/urn:nbn:de:gbv:46-00102323-13 |
| Summary: | This thesis documents sedimentary changes in the middle to late Miocene of the Atlantic and Pacific Ocean basins. This time interval known as the carbonate crash interval (12-9Ma) displays a severe perturbation of the carbonate system in the framework of the major Cenozoic cooling accompanied by changes in circulation mode, global nutrient shifts, plankton size changes and stratification of the ocean basins. These developments led to modern patterns of biogenic sediment distribution and ecological niches. The main goal of this work was to investigate control mechanisms on Carbonate-Crash-events (CC-events) and to find hints to major discrepancies concerning timing and strength of these events. For this purpose carbonate preservation proxies and carbonate budgets were investigated and evaluated in the Atlantic at the Ceará Rise in a depth transect (ODP sites 926, 927 and 928). The data show that the dissolution occurred in a broad zone between the foraminiferal lysocline at 3300 m depth and the carbonate compensation depth (CCD) at about 4000 m water depth. Detailed mass losses of coccoliths and foraminifer carbonate were calculated among sites. Dissolution is evident throughout the record however preservation seems to increase in correspondence to Northern Component water formation (precursor of North Atlantic Deep water). Productivity decreases of calcareous plankton productivity here (centered at about 9.5 Ma) seem to be as well a factor controlling CC-events during the late Miocene. Furthermore the evaluation of preservation proxies from the coarse calcareous silt fraction (CSmean and CS percent) showed that the fragmentation of foraminifera is probably a more suitable indicator of carbonate dissolution. CSmean and CSpercent did not reproduce the depth dependant carbonate dissolution, which was evident in all other parameters (carbonate content, coarse fraction content, foraminiferal fragmentation). The comparison of Ceará Rise coarse fraction records to Caribbean Site 999 showed in contrast to earlier ... |
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