Submitted by William Justo Figueiro (williamjf) on 2015-07-15T20:29:02Z No. of bitstreams: 1 14c.pdf: 18447268 bytes, checksum: cb27bcfcdf1b467b658d2ece3ae7777b (MD5) / Made available in DSpace on 2015-07-15T20:29:02Z (GMT). No. of bitstreams: 1 14c.pdf: 18447268 bytes, checksum: cb27bcfcdf1b467b658d2ece3ae7777b (MD5) Previous issue date: 2012-11-12 / Nenhuma / O presente estudo apresenta a taxonomia, bioestratigrafia e paleoecologia dos foraminíferos planctônicos e bentônicos recuperados no intervalo Aptiano superiorAlbiano da sucessão dominantemente carbonática do Deep Sea Drilling Project (DSDP) Site 364, localizado na bacia de Kwanza (costa afora de Angola). Foram identificadas 30 espécies de foraminíferos planctônicos e 42 espécies de foraminíferos bentônicos. Com base nas assembleias de foraminíferos planctônicos, a seção sedimentar estudada foi subdividida em diversas biozonas, abrangendo as idades Aptiano tardio ao Albiano, da Zona Hedbergella trocoidea a Zona Pseudothalmanninella ticinensis. Uma conspícua discordância foi identificada no core 31, compreendendo do topo do Albiano inferior à base do Albiano superior. A composição específica das assembleias de foraminíferos planctônicos as caracteriza como assembleias marinhas de águas rasas e permite a inferência do domínio de condições mesotróficas a eutróficas ao longo do intervalo estudado. As associações aptianas de foraminíferos planctônicos apresentam afinidade paleobiogeográfica tetiana, suportando um influxo de água superficial tetiana no setor restrito (ao norte da Cadeia de Walvis-Elevação do Rio Grande) do Oceano Atlântico Sul setentrional já no Aptiano tardio. Tendências nos valores isotópicos de 13C, que devem ser cuidadosamente interpretadas devido a uma possível alteração diagenética, sugerem uma idade aptiana tardia (Zona Globigerinelloides algerianus) para o intervalo estratigráfico do core 42 ao core 37, no qual fósseis-guia tetianos estão ausentes, além de sugerir que os folhelhos negros da base do testemunho estudado (cores 42-39) podem ser correlatos ao evento anóxico do Aptiano tardio. Entre os foraminíferos planctônicos ocorre uma profunda mudança faunística na passagem Aptiano-Albiano, caracterizada por altas taxas de extinção seguidas por elevadas taxas de surgimento de espécies, além de uma significativa mudança no padrão arquitetural das testas. Foram identificadas três associações de foraminíferos bentônicos, que parecem ser principalmente controladas por variações paleobatimétricas. A fauna de foraminíferos bentônicos pode ser classificada como uma Associação do tipo Marssonella, provavelmente relacionada a paleoprofundidades neríticas a batiais superiores, e também exibindo uma marcada afinidade paleobiogeográfica tetiana. / This work presents a taxonomic, biostratigraphic and paleoecologic study on the planktic and benthic foraminiferal faunas recovered from the late Aptian-late Albian carbonatedominated succession of Deep Sea Drilling Project (DSDP) Site 364, located in the Kwanza Basin (offshore Angola). Thirty planktic and 42 benthic foraminiferal species were identified herein. Based on planktic foraminiferal assemblages, the studied section was subdivided in a series of biozones, late Aptian to late Albian in age, from the Hedbergella trocoidea Zone to the Pseudothalmanninella ticinensis Zone. A remarkable unconformity was identified in core 31, spanning the latest early to earliest late Albian. The specific composition of the recovered planktic foraminiferal assemblages characterizes them as open marine epipelagic dwellers, and permits the suggestion of predominant mesotrophic to eutrophic environmental conditions throughout the studied stratigraphic succession. Aptian planktic foraminiferal assemblages present a significant Tethyan paleobiogeographic affinity, supporting a Tethyan surface-water influx into this restricted southeastern sector of the northern South Atlantic Ocean (north to the Walvis Ridge-Rio Grande Rise) back in the late Aptian. 13C trends, which have to be carefully interpreted due to possible diagenetic overprint, suggest a late Aptian age (Globigerinelloides algerianus Zone) for the stratigraphic interval from core 42 to about core 37, where Tethyan age-diagnostic foraminiferal species are missing, as well as that the black shale levels in cores 42-39 could be correlated to the “late Aptian anoxic event”. Among planktic foraminifera, a conspicuous faunal turnover occurs at the Aptian/Albian transition, characterized by high rates of extinctions followed by increasing rates of species originations and changes in tests’ architecture. Three benthic foraminiferal associations were identified, which seem to be mainly controlled by changes in paleobathymetry. Also, the studied benthic foraminiferal fauna could be classified as a Marssonella Association, probably related to neritic and upper bathyal paleodepths, also exhibiting a Tethyan paleobiogeographic affinity.

The biostratigraphy and isotope stratigraphy of the upper Aptian to lower Cenomanian interval including oceanic anoxic events OAE1b, 1c and 1d are investigated in ODP Site 763, drilled on the Exmouth Plateau offshore northwest Australia. Benthic foraminifera suggest that Site 763 was situated in outer neritic to upper bathyal water depths (~150-600 m). OAEs of the Atlantic basin and Tethys are typically associated with organic carbon-rich black shales and δ13C excursions. However, OAEs at this high latitude site correlate with ocean acidification and/or pyrite formation under anoxic conditions rather than black shales. Ocean acidification maybe responsible for sporadic low abundances of planktic foraminifera compared to radiolarians and benthic foraminifera associated with increased volcanogenic CO2 production during the formation of the Southern and Central Kerguelen Plateaus. Sea surface temperature may have cooled to 11°C in the late Aptian but increased gradually during the Albian. The Aptian/Albian boundary is placed at a negative carbon isotope excursion associated with the lowest occurrence of Microhedbergella renilaevis, typically found within the Niveau Kilian black shale of OAE1b. Third-order sea level cycles, particularly in the middle Albian, produced cyclic changes in the abundance of inoceramid prisms that increased during inferred times of falling sea level. The late Albian OAE1c and OAE1d coincide with horizons of intense pyritization and the absence of all biocomponents suggesting the development of euxinia. Warm Tethyan waters reached the Exmouth Plateau during the latest Albian based on the presence of thermocline dwelling keeled planktic foraminifera including Planomalina buxtorfi.