Bioestratigrafía y biocronología de nanofósiles calcáreos del Mioceno en el norte de Colombia y Caribe

[EN] Very few stratigraphic and biostratigraphic studies have been done in the land areas of NE South America based on marine fossil faunas and there are few modern paleoceanographic and biostratigraphic calcareous nannofossil reconstructions. A better approximation to paleoceanographic conditions for offshore Colombian Caribbean are compiled in several publications referred to the ODP 165 expedition, concretely for site 999 (Kameo & Bralower, 2000 and references therein). Calcareous nannofossils are one the best micropaleontological group used in many disciplines because of their importance in paleoenvironmental reconstruction and stratigraphy. The bioestratigraphic zonation proposed constitutes the first calcareous nannoplankton research to construct a biochronologic scheme for the Cenozoic of northern Colombia, which has direct applications for oil exploration in the offshore areas of the Colombian Caribbean basin. Its correlation with the well-calibrated ODP Site 999 offshore record provides a robust biostratigraphic framework. In this research, the classical biostratigraphic calcareous nannofossil-based schemes proposed by Martini (1971) and Bukry (1973, 1975) later codified by Okada & Bukry (1980) for the subdivision of Cenozoic have been chosen, because those were established in detailed sequences of the Caribbean Sea. In order to obtain insights into the changes in paleoceanographic conditions and establish biostratigraphic zonation a detailed sampling was carried out in three sequences. Two were recovered in onshore Colombian and the other corresponds to an offshore core drilled in Caribbean Sea. The onshore sequences, Arroyo Alférez and Carmen de Bolívar, Estratigráfico 4 are one of the best Neogene sequences known for the Lower Magdalena Valley. The offshore core ODP 165, Site 999 is located on a previously unnamed rise (Kogi Rise) in the Colombian basin (Western Caribbean). In general, the record is partially continuous and the preservation of nannoplankton assemblage is medium to good. Most of bioevents used are consistently recognizable in the record analyzed. Many other supplementary biohorizons improved the biostratigraphic resolution until ∼0.431 Ma and ∼0.257 Ma in the Arroyo Alférez and Carmen de Bolívar, Estratigráfico 4; respectively. While in the ODP 999 it was increased from ∼0.604 Ma (Kameo & Bralower, 2000) to ∼0.316 Ma. However it is important to mention the evident lack of stratigraphic levels identified in the proximal sequences, the Arroyo Alférez and the Carmen de Bolívar, Estratigráfico 4. The lost levels represent lack of sedimentation and constitute hiatuses but the events of calcareous nannofossils which are defined zone boundaries are not affected. On the other hand this investigation did not reveal the presence of hiatus at any level of ODP 999 record. The global and regional changes occurred in the Caribbean sequences considered in this study are well reflected in the nannofossil assemblage character and in their fluctuation pattern. Exceptional abundances in some species of Sphenolithus were registered in both, the ODP 999 and the Carmen de Bolívar, Estratigráfico 4 sections. They are related or no with important changes in sedimentation rate, assemblage distribution and abundance pattern and represents a potential key for future paleoceanographic interpretations.

Author

• Mejía Molina, Alejandra

• Tesis y disertaciones académicas
• Universidad de Salamanca (España)
• Tesis Doctoral
• Academic dissertations
• Nanofósiles calcáreos
• Cocolitóforos
• Cenozoico
• Bioestratigrafía
• Mar Caribe
• Colombia
• Calcareous Nannofossils
• Coccolithophores
• Cenozoic
• Biostratigraphy
• Caribbean Sea

Identifier

hdl:10366/83320

OAI identifier oai:identifier

oai:gredos.usal.es:10366/83320