A growing body of Nd isotope data derived from fish debris and Fe-Mn crusts suggests that the Pacific was characterized by deep-water mass formation in both the North and South Pacific during the Early Paleogene. However, the South Pacific source has not been identified to date. Here we present new fossil fish debris neodymium isotope data from the South Pacific and southern tropical Pacific Ocean Drilling Program and Deep Sea Drilling Project Sites 323, 463, 596, 865 and 869 (paleowater depths spanning 1500 to 5000m) to reconstruct the water mass composition over the time interval ~80 to ~24 Ma. The data indicate a relatively unradiogenic South Pacific water mass composition, and the composition of Nd increases with distance northward. The new tropical Pacific data are consistent with existing records from that region. Analyses of detrital sediment Nd isotopic composition, combined with the dissolved Nd composition recorded by fish debris, suggests that the South Pacific water mass convected in the Pacific sector of the Southern Ocean. We designate this water mass South Pacific Deep Water (SPDW). The Nd isotopic composition of SPDW is more radiogenic than initially hypothesized and the relatively small increase in isotopic composition (from ~-6 to ~-4) during the transit from the Southern Ocean to the tropical Pacific suggests a faster rate of overturning circulation during the greenhouse climate interval than previously thought.

Oceanic circulation remains one of the poorly understood elements of the global climate system, despite its importance to planetary heat redistribution and carbon cycling. The nature of deep-water formation and circulation in ancient oceans are even more poorly constrained. In order to understand climate dynamics of past and future climates we must have a better understanding of the role of deep-ocean circulation. In this dissertation I investigated changes in intermediate- to deep-water circulation in three different ocean basins during two different geologic eras. The first study focused on the late Pleistocene (~25 ? 60 ka) California margin to investigate the role of intermediate water circulation in abrupt climate fluctuations. The other two studies investigated deep-water circulation during the Late Cretaceous (~70 ? 100 Ma) greenhouse interval, to determine if deep waters formed in the southern Indian or Atlantic basins. The above studies employed neodymium isotopes preserved in biogenic apatite (fish teeth and bones) and foraminiferal calcite to reconstruct the provenance of intermediate- to deep-water masses. Here I present data from two sites located at intermediate depths on the late Pleistocene California margin as well as seven Deep Sea Drilling Project and Ocean Drilling Program Cretaceous aged sites; four in the South Atlantic Ocean, and three in the Indian Ocean. The new Pleistocene data rule out changes in the source of intermediate waters to the California margin, thus the recorded changes in seafloor oxygenation were caused by changes in sea surface productivity. In the Cretaceous, the spread of deep waters formed in the high-latitude South Atlantic was hindered by tectonic barriers until the mid Campanian when the subduction of Rio Grande Rise allowed for the continuous flow of deep waters from the Southern Ocean into the North Atlantic. The deep Cretaceous Indian Ocean was filled with deep waters formed in the high-latitude Indian Ocean, until being replaced with waters sourced in the Pacific from the late Cenomanian to early Campanian before a return to southern Indian-sourced waters for the remainder of the study interval.

Approximately 6.6 million years ago in the Eastern Equatorial Pacific a large increase in biogenic mass accumulation rates (MAR’s) occurred. This increased level of biogenic mass accumulation persisted until about 4.4 Ma at which time levels returned to those similar to before the transition at 6.6 Ma. The exact nature of the change that facilitated this transition in biogenic MAR’s, however, was not understood. Here we present the results of a study which characterizes the diatom assemblage spanning the depositional transition at 6.6 Ma from sediments taken from ODP Hole 850B. A close inspection of lithology reveals a clear change in lithology from a diatom nannofossil ooze to a nannofossil diatom ooze at 6.6 Ma. This transition is immediately followed by the occurrence of laminated diatom ooze (LDO). Diatom absolute abundance data reveals three levels of productivity associated with pre-transitional, post-transitional, and LDO formational sediments. An increase in the absolute abundance of Thalassionema nitzschioides was the major contributor to the formation of post-transitional, and LDO sediments. The known ecological preferences of this species indicate an overall increase in nutrient availability followed by sporadic changes in nutrient availability. These changes in nutrient availability could be associated with the establishment, or increase in strength, of an upwelling cell and/or the increase in nutrients made available via upwelling due to a shoaling of the thermocline.

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (leaves 148-150). Also available via World Wide Web.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 296-341).

Bibliography: pages 147-155. / 92 cytheracean species, representing 44 genera are recorded from the Palaeogene Agulhas Bank and west coast margin of South Africa. 11 genera and 3 species are common with the Upper Cretaceous faunas. 12 genera (18 species) are left in open nomenclature. The following genera are represented:- Bythoceratina, Incongruellina, Ruggieria, Eucythere, Krithe, Parakrithe, Eucytherura, Cytheropteron, Ambostracon, Urocythereis, Muellerina, Leguminocythereis, Loxoconcha, Schlerochilus, Poseidonamicus, Bradleya, Agrenocythere, Australileberis, Chrysocythere, Costa, Echinocythereis, Haughtonileberis, Henryhowella, Parvacythereis, Phacorhabdotus, Soudanella, Stigmatocythere, Togoina, Trachyleberis, Veenia, Atlanticythere, Xestoleberis. Data on South African Cretaceous and Palaeogene ostracod faunas are discussed in terms of: faunal associations for the South African Palaeogene JC-1, Agulhas Bank and west coast provinces; characteristic species of Upper Eocene and Upper Eocene to Oligocene strata; generic variations across the Cretaceous/Tertiary boundary. Palaeo-environmental trends from a Cytheracea, Cypridacea + Bairdiacea, Cytherellidae (CCBC) plot indicate a sea level change from <100m (Palaeocene- Eocene), to shallower water with restricted circulation (Upper Eocene) to moderate depth, 100 - 200m (Lower Oligocene). South African faunas are compared with those from adjacent Palaeogene ostracod faunal provinces. Strong generic links occur with West Africa (8 genera in common) and Pakistan (9 genera in common) with only 3 genera in common with Australia and 3 with Argentina.

Thesis (docteur)--Université de Bretagne occidentale, Centre océanologique de Bretagne, 1978. / Includes bibliographical references (leaves [99]-107) and index.

A dissolução do carbonato está ligada à circulação dos oceanos e às variações climáticas. Através desse estudo foi possível identificar, durante o último ciclo glacial (150 mil anos), três eventos de dissolução na Bacia de Santos, durantes os estágios isotópicos marinhos 5d, 5b e 4. Para isso foram utilizados indicadores de dissolução micropaleontológicos, geoquímicos e sedimentares. Através destes indicadores foi possível inferir quais processos estão associados à dissolução do carbonato durante estes períodos. Os indicadores micropaleontológicos densidade área (&#961;A), espécies resistentes à dissolução (ERD e BDI) e índice de fragmentação (IF) foram capazes de identificar o início dos eventos de dissolução, enquanto os indicadores de variação tamanho de grão no sedimento bruto, teor de carbonato de cálcio (%CaCO3) em diferentes frações de tamanho, razão entre foraminíferos bentônicos e planctônicos (B/P) e peso normalizado (SBW) foram relacionados ao auge da dissolução. Os indicadores com base em cocolitoforídeos (CEX\'), índice Broecker/Clark e índice Chiu/Broecker apresentaram resultados inconclusivos. Observou-se que durante os três eventos de dissolução houve um aumento na contribuição de uma massa d\'água de origem sul (mais corrosiva ao carbonato) na região, indicado a partir da variação de &#948;13Cbentônico. Os eventos de dissolução também coincidiram com o aumento do aporte de sedimento não-carbonático (indicador de aporte continental, Fe/Ti e Ti/Ca). Os indicadores de paleoprodutividade (PP, RN e razão G. bulloides/G. ruber) não indicaram um aumento de produtividade primária durante os eventos de dissolução, de modo que a produtividade não foi considerada como um dos processos principais que induziram os eventos de dissolução neste estudo. As profundidades em que estes testemunhos se encontram (&#8764;2000 m) também eliminam a possibilidade de que a dissolução tenha ocorrido em função da variação da posição da lisoclina, mesmo considerando que esta tenha estado &#8764;1000 m mais rasa durante o último período glacial. Desta forma, acreditamos que os eventos de dissolução estejam relacionados com a maior contribuição de uma massa d\'água de sul, mais corrosiva ao carbonato, em torno de 2000 m de profundidade, durante os MIS 5d, 5b e 4, como resultado da reorganização das massas d\'água profundas na região (uma redução na intensidade da AMOC) nestes períodos. / The calcium carbonate dissolution is linked to ocean circulation and climate change. Through this study it was possible to identify, during last glacial cycle (150 kyrs), three dissolution events occurring in the Santos Basin, during MIS 5d, 5b and 4. For this, micropaleontological, geochemical and sedimentary proxies were used. Through these proxies it was possible to infer which processes are associated with the carbonate dissolution during this period. The micropaleontological proxies of area density (&#961;A), dissolution resistent species (ERD and BDI) and fragmentation index (IF), were able to identify the beginning of the dissolution events, while the proxies of grain size variation, calcium carbonate content in different size fractions, benthic/planktonic ratio (B/P) and size normalized weight (SBW) were related with the dissolution peak. The proxies based in cocoliths (CEX\'), Broecker/Clark Index and Chiu/Broecker Index presented inconclusive results. It was observed that during the three dissolution events there was an increase in the contribution of the water mass of southern origin (more corrosive to the carbonate) in the region, indicated from the variation of &#948;13C in benthic foraminifera. This increase also coincided with the increase in the contribution of non-carbonate sediment (continental input indicator -IAC, Fe/Ca and Ti/Ca). The paleoproductivity proxies (based in cocoliths - PP, RN, and G. bulloides/G. ruber ratio) did not indicate an increase in primary productivity during dissolution events, therefore productivity was not considered as one of the processes that led to dissolution in this study. The depths at which these sediment cores are found (&#8764;2000 m) also eliminate the possibility that the dissolution occurred as a function of the variation of the position of the lysocline, even if considering that it was &#8764;1000 m shallower during the last glacial period. In this way, we believe that the dissolution events are related to an increased southern-sourced water mass more corrosive to the carbonate during MIS 5d, 5b and 4, which implies the reorganization of the water masses in the region and a reduction in the strength of AMOC during these periods.

Para melhor entender a relação entre os oceanos e as variações climáticas são necessários registros destes eventos. O presente trabalho tem por objetivo principal estudar as variações climáticas e oceanográficas utilizando os registros de conteúdo de carbonato em dois sedimentos coletados na Bacia de Campos. A cronologia dos testemunhos foi primeiramente estabelecida através do conteúdo de carbonato. Sua validação foi feita através das análises de radiocarbono em duas amostras próximas do topo de cada testemunho. Outros métodos usados para corroborar a cronologia foram o biozoneamento com base nos foraminíferos planctônicos Globorotalia menardii e Pulleniatina obliquiloculata, executadas em ambos os testemunhos; análises de isótopos de oxigênio em foraminíferos planctônicos Globigerinoides ruber em amostras do KF-13; e dados de susceptibilidade magnética para o KF-14. Com exceção de radiocarbono, os outros métodos não fornecem idades absolutas Foi então necessário compará-los com estratos de idade conhecida. Para isso utilizaram-se dados do SPECMAP, tornando possível a inferência dos estágios isotópicos marinhos para estes testemunhos. Estabelecida a estratigrafia para os testemunhos com base no conteúdo de carbonato, identificamos as diferentes condições climáticas nas quais os sedimentos foram depositados. As curvas de conteúdo de carbonato para ambos os testemunhos, junto com os dados de isótopos de oxigênio para o KF-13 e a de susceptibilidade magnética para o KF-14 foram comparados com a curva de isótopos de oxigênio do SPECMAP, inferindo assim idades aproximadas para algumas das feições apresentadas. Também foram utilizadas as biozonas de foraminíferos planctônicos identificadas para estimar as idades aproximadas em pontos ao longo do testemunho, além dos dados de radiocarbono. Estabelecida essa cronologia foi possível fazer o cálculo das taxas de sedimentação. Os resultados aqui apresentados mostram a importância que o conteúdo de carbonato nos sedimentos tem para estudos de variações climáticas. / Records of climatic variations are necessary for better understanding of the relationship between the oceans and these events. The main objective of this work is to study climate and ocean variations using carbonate records in two sediment cores collected from the Campos Basin. The chronology of the sediment cores was established through carbonate content. Validation was achieved through radiocarbon analysis in two samples from the top of each core. Other methods used to corroborate chronology were the establishment of biozones based on the planktonic foraminifera Globorotalia menardii and Pulleniatina obliquiloculata, used in both sediment cores; oxygen isotope analysis on the planktonic foraminifera Globigerinoides ruber in samples from KF-13; and magnetic susceptibility data for KF-14. With the exception of radiocarbon, other methods do not provide absolute ages, making it necessary therefore to compare with other stratum of known ages. Data from SPECMAP were used enabling inference of marine isotopic stages for this sediment cores. Once the stratigraphy was established based on the carbonate content, it was possible to identify the climate conditions in which the sediments were deposited. Carbonate content curves for both cores along with the oxygen isotope data for the KF-13 and KF-14 magnetic susceptibility data were compared with the oxygen isotope curve from SPECMAP, inferring approximate ages for some of the features presented. Identified foraminiferal biostratigraphic zones were used to estimate the approximate ages in certain points along the core, along with radiocarbon dating. Once this chronology was established, it was possible to calculate sedimentation rates along the sediment cores. The results here presented demonstrate the importance of carbonate content variations in sediment cores as a means to understanding climate variations.

Estudos paleoceanográficos são baseados em indicadores indiretos, ou seja, informações sedimentológicas, paleontológicas e geoquímicas que refletem as condições ambientais dos oceanos no passado geológico. Processos tafonômicos como a dissolução podem enviesar a informação contida nestes indicadores. Porém, quando corretamente identificada, a dissolução pode se tornar uma ferramenta para caracterizar mudanças oceanográficas, como variações na distribuição das massas d’água e a acidificação dos oceanos. O objetivo deste estudo é entender como ocorre este enviesamento, identificar indicadores que determinam a presença ou ausência da dissolução e identificar alterações oceanográficas no Quaternário tardio da Bacia de Pelotas em função deste processo. Esta tese compreende várias etapas, incluindo a realização de experimentos de dissolução em varias espécies de foraminíferos provenientes do oeste do Atlântico Sul, a comparação entre dados de fauna de foraminíferos planctônicos de sedimento com as condições ambientais do oceano Atlântico Sul e, finalmente, as análises de testemunhos do Quaternário tardio da Bacia de Pelotas (foraminíferos, cocolitoforídeos, teor de carbonato, granulometria, δ18O, AMS 14C). Os experimentos geraram um ranking de susceptibilidade à dissolução para foraminíferos, identificando Orbulina universa e Hoeglundina sp. como bons indicadores de pouca dissolução, além de identificar a razão entre foraminíferos planctônicos e bentônicos como imprópria para indicar o grau de dissolução. A análise da fauna de foraminíferos planctônicos do Atlântico Sul identificou maior enviesamento por condições ambientais de fundo em áreas com massas d’água mais corrosivas provenientes do sul, bem como o viés observado nas espécies frágeis pode ser relacionado aos erros em estimativas de paleotemperaturas baseadas em censos de fauna. Baseado nos indicadores aqui elaborados, combinado com outros indicadores comuns, as alterações oceanográficas na Bacia de Pelotas indicam um aumento da dissolução em períodos glaciais em função do avanço da Água Antartica de Fundo e da Água Circumpolar Superior. Finalmente, na parte conceitual desta tese, é proposta uma definição de zona tafonômicamente ativa para sistemas pelágicos, que deve considerar a coluna d’água como seu limite superior. / Paleoceanographic studies are based on proxy data, i.e. sedimentological, paleontological and geochemical information that reflect the environmental conditions of the oceans in the geological past. Taphonomic processes such as dissolution may bias the information contained in these proxies. However, when correctly identified, dissolution can become a tool to characterize oceanographic changes, such as variations in the water masses distribution and acidification of the oceans. The purpose of this study is to understand how this bias occurs, to identify proxies that determine the presence or absence of dissolution and to identify late Quaternary oceanographic changes in the Pelotas Basin as a function of this process. This thesis comprises several stages, including dissolution experiments on several foraminifera species from the western South Atlantic, comparison between sediment plankton foraminifera fauna data with environmental conditions of the South Atlantic Ocean, and finally, the analyses of late Quaternary of the Pelotas Basin cores (foraminifera, coccolith, carbonate content, grain size, δ18O, and AMS 14C). The experiments generated a ranking of susceptibility to dissolution for foraminifera, identifying Orbulina universa and Hoeglundina sp. as good proxies of low dissolution, besides identifying the planktonic and benthic foraminifera ratio as inappropriate for indicating the degree of dissolution. The analysis of the planktonic foraminifera fauna of the South Atlantic identified greater bias due to bottom environmental conditions in areas with more corrosive water masses from the south, as well as the observed bias in fragile species may be related to errors in paleotemperature estimates based on fauna census counts. Based on the proxies developed here, and other indicators frequently used, the late Quaternary oceanographic changes in the Pelotas Basin indicate an increase of the dissolution in glacial periods due to the advance of Antarctic Bottom Water and Upper Circumpolar Deep Water. Finally, in the conceptual part of this thesis, a taphonomically active zone for pelagic systems is proposed, which should consider the water column as its upper limit.