The southern Campos Basin comprises syn- and post-rift strata characterised by thick and extensive units of non-marine limestones. These carbonate platforms are scientifically significant due to their unusual palaeoenvironmental setting, and the complexity of the factors controlling their accumulation. They are of economic importance due to discoveries of giant hydrocarbon accumulations in these non-marine carbonate rocks. 3D seismic interpretations show an oblique extensional rifting system that formed a series of graben, half-graben, accommodation zones and horsts oriented NESW to NNE-SSW. The area is subdivided into three tectonic domains based on structural style, stretching factors and subsidence rates. The structural template of the syn-rift exerts a strong influence on depositional patterns. Core logging and thin-section work together with FMI and sidewall core data indicate proximal to more distal lacustrine carbonate deposits with fluvio-deltaic clastics in marginal areas. The dominant carbonate facies are molluscan rudstones and floatstones and a taphonomic analysis (taphofacies) of the cored intervals and exposure surfaces indicate accumulation in shallowing-upward cycles in response to changes in lake level. Microbialite facies, Aptian in age, appear to occur in the most distal locations in restricted palaeoenvironmental conditions. Facies models are presented for the skeletal, mollusc-rich deposits of the Barremian Coqueiros Formation and the overlying microbialite-rich Aptian Macabu Formation. The deposits are stacked in a hierarchical arrangement of four levels of cyclicity ranging from the entire rift basin fill to metre-scale cycles. Controls on formation of these cycles include structural setting, climate and lacustrine margin progradation. Different types of carbonate platform form in the different basinal settings and include footwall areas of fault-blocks, accommodation zones and buried horst blocks. The southern Campos Basin evolves from an initial alkali lake (Barremian) to a main phase of syn-rift, brackish lake conditions. The post-rift succession (Aptian) is characterised by both brackish and hypersaline conditions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:594409 |
| Date | January 2013 |
| Creators | Muniz, Moises Calazans |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://repository.royalholloway.ac.uk/items/3f728d6a-29d2-41ab-9a5a-fec206df679b/1/ |
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