Thesis (M. Sc.)--Carleton University, 1992. / Also available in electronic format on the Internet.

Thesis (doctoral)--Universität Bremen, 2006. / Includes bibliographical references.

No description available.

Thesis (Ph.D.)--University of Western Australia, 2003.

A região da Península Antártica (PA) é importante para a circulação oceânica e o equilíbrio da temperatura global, além de ser detentora de grandes reservatórios de água doce e reservas de hidrocarbonetos e de hidrato de gás. Organismos bentônicos desses locais, como os foraminíferos, respondem de forma rápida a variações ambientais e são bastante utilizados em estudos de monitoramento mais precisos. Neste trabalho foram analisadas associações de foraminíferos em relação a parâmetros granulométricos e geoquímicos (elementos maiores e traço) de regiões ricas em hidrato de gás, situadas na PA. Para tal objetivo foram analisados sedimentos superficiais e subsuperficiais de: 1) região costeira (profundidade < 11 m) da Ilha de Marambio (IM), Mar de Weddell e 2) Passagem de Drake (PD). Na PD foram coletados 5 testemunhos (8 cm de comprimento) a 480 m de profundidade (D1) e 2 testemunhos (20 cm de comprimento) de 3800 m de profundidade (D2). Os valores de densidade e diversidade de foraminíferos encontrados aqui raramente são descritos na literatura para a região antártica. Contatou-se que as associações de foraminíferos da região da PA são constituídas por diversas espécies monotalâmicas e aglutinantes. A análise de agrupamento evidenciou associações com diferentes atributos ecológicos. Nas biocenoses da IM observou-se predominância de foraminíferos monotalâmicos de carapaça orgânica ou predominantemente orgânica (Psammosphaga magnetica e allogromiídeos), que apresentaram alta densidade e diversidade em sedimentos lamosos, ricos em nutrientes e valores elevados de oxigênio dissolvido. Já as biocenoses da região D1 apresentaram dominância de foraminíferos calcários, em particular de Epistominella exigua, indicadora de ambiente rico em fitodetritos. Nas tanatocenoses foram observadas predomínio de espécies aglutinantes como Deuterammina grisea e Cribrostomoides jeffreysii, com valores de densidade e riqueza aumentando da base ao topo em todos os testemunhos. Nos testemunhos da área D2, tanto na bio quanto a tanatocenose houve dominância de espécies típicas de ambiente hipóxico e rico em matéria orgânica (e.g., Adercotryma glomeratum e Spiroplectammina biformis) e baixos valores de densidade e riqueza. A morfometria das carapaças da Passagem de Drake (D1 e D2) apontou aumento significativo de A. glomeratum com a profundidade, provavelmente relacionado a adaptações a regiões profundas e a estabilidade ambiental. A Análise de Componentes Principais revelou que oxigênio dissolvido do sedimento, granulometria, porcentagem de CaCO3, concentração de potássio (D1), bem como concentrações de elementos maiores e traços (D2) foram as principais variáveis que influenciaram a distribuição das espécies. Não foi possível identificar alterações nas associações e em relação aos padrões ecológicos, devido às emanações de hidrato de gás. Assim, ressalta-se a necessidade da realização de mais estudos, como análises morfológicas e químicas das carapaças dos foraminíferos, principalmente em espécies aglutinantes, ainda mais em regiões como a PA, reconhecidamente mais sensível as mudanças climáticas e de enorme importância para o equilíbrio do clima da Terra / The Antarctic Peninsula (PA) region is essential for ocean circulation and global temperature equilibrium, as well as having large freshwater reservoirs, hydrocarbon and gas hydrate reserves. Benthic organisms from these locations, such as foraminifera, respond rapidly to environmental variations and are widely used in more accurate monitoring studies. In this work, foraminifera associations were analyzed concerning granulometric and geochemical parameters (major and trace elements) of regions rich in gas hydrate, located at AP. For this purpose, surface and subsurface sediments were analyzed from 1) coastal region (depth <11 m) of Marambio Island (IM), Weddell Sea and 2) Drake Passage (PD). In PD five cores (8 cm long) were collected at 480 m depth (D1) and two cores (20 cm long) at 3800 m depth (D2). Foraminifera density and diversity values found here are rarely described in the literature for the Antarctic region. The results of foraminifera associations in the PA region are composed of several monothalamic and agglutinant species. Cluster analysis showed associations with different ecological attributes. In MI biocenosis there was a predominance of monothalamic foraminifera of organic or predominantly organic tests (Psammosphaga magnetica and allogromiidae), with high density and diversity in muddy sediments, rich in nutrients and high values of dissolved oxygen. On the other hand, the biocenosis of the D1 region was dominated with calcareous foraminifera, in particular, Epistominella exigua, indicating an environment rich in organic matter. In the thanatocoenosis, agglutinating species such as Deuterammina. grisea, and Cribrostomoides jeffreysii predominated, with density and richness increasing from bottom to top in all cores. In the D2 area, both in bio as well as in thanatocoenosis, there was a dominance of typical species of hypoxic environments and rich in organic matter (e.g., Adercotryma glomeratum and Spiroplectammina biformis), and low density and richness values. The morphometry from DP (D1 and D2) showed a significant increase in size of A. glomeratum with depth, probably related to deepsea adaptations and environmental stability. Principal Component Analysis revealed that dissolved oxygen in sediment, granulometry, CaCO3 percentage, potassium concentration (D1) as well as major and trace elements concentrations (D2) were the main variables that influenced species distribution. It was not possible to identify changes in organisms and the relation to ecological standards due to gas hydrate. Thus, further studies are necessary, such as morphological and chemical analysis of foraminifera tests, especially in agglutinating species, even more so in regions such as PA, which are known to be more sensitive to climate change and of great importance to the Earth\'s climate balance

Thick Paleogene sequences occur in the southern deformed fold and thrust belt of the Himalayas. In this thesis I describe detailed litho- and biostratigraphy from ten key stratigraphic sections in the Kohat Basin, the Potwar Basin and the Trans Indus Ranges (TIR). These stratigraphies combined with microfacies analysis resulted in a new interpretation of the tectono-stratigraphic history of the area, which is dominated by India-Asia collision but where eustatatic effects can also be identified. Of particular interest is documenting the timing of the final closure of the northern rim of the Tethys caused by this collision. The Kohat and Potwar Basins represent foreland basins within the collision zone. Their stratigraphies document effects of local tectonics and eustatic sea level. The biostratigraphy is based on occurrences of larger benthic foraminifera. Taxonomy of the species is included in the thesis. The Paleogene rocks of the study area are divided into local larger benthic forminiferal biozones: BFZK 1- BFZK 6 in the Kohat Basin and BFZP 1-BFZP 3 in the Potwar Basin and the TIR. These local biozones are correlated to the global standard biozonation schemes of Höttinger (1960), Schaub (1981), and Serra Kiel et al. (1998). The ages of the sequences are Late Paleocene (Thanitian) to Middle Eocene (Upper Lutetian) in the Kohat Basin, and Late Paleocene (Thanitian) to Early Eocene (Middle Cuisian) in the Potwar Basin and the TIR. The sediments were deposited along a carbonate ramp platform in both areas (sensu Read, 1982, 1985). The sequence stratigraphic histories of the two basins are described as follows. In the Kohat Basin, Thanitian to Middle Cuisian strata record the first Transgressive-Regressive cycle (TRK 1). The first sequence boundary (SBK 1) is followed by Middle Cuisian-Upper Cuisian lowstand progradational deposition that marks the end of TRK 1 cycle. Middle Lutetian 1-Upper Lutetian strata represent the second Transgressive-Regressive cycle (TRK 2). The second sequence boundary (SBK 2) ends TRK 2 deposition, after which no more deposition took place. In the Potwar Basin and the TIR, Thanitian strata comprise the first Transgressive- Regressive cycle (TRP 1), whilst Lower Lllerdian-Middle Lllerdian 1 strata constitute the second Transgressive-Regressive cycle (TRP 2). Middle Lllerdian 2 to Middle Cuisian strata mark the third Transgressive-Regressive cycle (TRP 3). Three sequence boundaries (the SBP 1, the SBP 2 and the SBP 3), marked by exposure surfaces, separate the three depositional cycles. The SBP 1 and SBP 2 sequence boundaries are controlled by local tectonics. In contrast the SBP 3 and SBK 1 sequence boundaries are synchronous at 49.5 Ma, and represent a phase of significant relative sea level fall, possibly driven by the combined effect of uplift (collision tectonics) and eustatic sea level fall (e.g. Haq et al., 1987). This implies that proto-closure of the northern rim of the Tethys occurred around 49.5 Ma. Reestablishment of marine conditions in the Kohat Basin occurred in the Middle Lutetian 1 around 45.8 Ma, possibly caused by a combination of flexural loading of the Indian plate (Pivinik & Wells, 1996) and eustatic sea-level rise (e.g. Haq et al., 1987). The final closure of the Tethys, marked by the end of marine sedimentation in the Kohat Basin, occurred in the Upper Lutetian (41.2 Ma). Finally, Himalayan foreland molasses sedimentation occurred during Miocene to Pliocene.

Thesis advisor: Jeremy Shakun / The mechanisms of abrupt climate change during the last glacial period are not yet fully understood. The objective of this research is to use oxygen isotope and magnesium/calcium ratios from foraminifera in a marine sediment core <200 km southeast of New York City (Ocean Drilling Program 174 Site 1073A) to test the hypothesis that changes in freshwater run-off patterns during intermediate extensions of the Laurentide Ice Sheet caused abrupt climate change by disrupting the Atlantic thermohaline circulation. The combination of foraminiferal δ18O and Mg/Ca yields salinity as an isolated variable, which is used as a proxy for Hudson River discharge through ~42,000-28,000 years ago. This thesis reviews the literature on abrupt climate change and compares the Hudson River paleodischarge record to established records of abrupt climate events observed in Greenland ice cores. It concludes that a higher resolution of data points is required to evaluate the impact of Hudson River discharge on abrupt climate change. / Thesis (BS) — Boston College, 2015. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Earth and Environmental Sciences.

The reliability of foraminifera as stratigraphic index fossils, and as isotopic proxies of marine environments, is based on the assumption that the fossil concepts represent uniform species, responding consistently to their ambient environments. Understanding sources of uncertainty is, therefore, critical. In this dissertation, I explore a potential bias in the application of planktonic foraminifera utilized extensively for Cenozoic paleo-reconstruction and, to a lesser extent, biostratigraphy: the Globigerinoides ruber-elongatus plexus (‘plexus’ meaning a complex network of interconnected members). Taxonomic revisions since 1826 have resulted in the merging of multiple Globigerinoides species names under one general designation (“Globigerinoides ruber”), the implications of which are now under scrutiny. These “morphotypes” of G. ruber have been shown to incorporate stable isotopes and trace elements in seawater dissimilarly, and correspond to multiple genetic species, some of which occupy different environments. Various criteria exist to sub-divide, group, or distinguish members of the Globigerinoides plexus, most notably the recurring use of Globigerinoides elongatus as a less spherical, less symmetrical counterpart to G. ruber. But the efficacy of these various taxonomic criteria has not been tested quantitatively. Most rely on the traits of visually distinctive “end-members,” while specimens in the morphological “transitional zone” are left to an observer’s subjective interpretation. This prevents quantification in census counts, and may lead to erroneous geochemical analyses. Furthermore, molecular clock estimates suggest that the G. elongatus species evolved significantly later than G. ruber, affecting its potential as a biomarker. In this dissertation, I examine the potential of a minimal-criteria system for classifying Globigerinoides-type morphologies using only three conditions: final chamber compression, final chamber asymmetry, and aperture compression. Morphometric analyses on specimens grouped according to this new system allow us to assess to what degree visual classification reflects morphospace discontinuity. Armed with this information, I then explore potential isotopic offsets between members of the Globigerinoides plexus, and its use in reconstructing regional differences in climate or habitat influences in the Gulf of Mexico and Caribbean basins. Finally, having shown that G. ruber and G. elongatus can be reliably visually distinguished, I tracked the species’ fossil presence individually in a deep core from the South China Sea, and confirmed the presence of G. ruber in the South China Sea through the late Miocene, and G. elongatus through the Pleistocene. While it is believed that neither species was traced to its true first occurrence (FO), the relative FO of G. ruber was shown to be 4–5 Ma before G. elongatus

The fossilized remains of the calcite shells of foraminifera comprise one of the most continuous and reliable records of the geologic evolution of climate and ocean chemistry. The trace elemental composition of foraminiferal shells has been shown to systematically respond to seawater properties, providing a way to reconstruct oceanic conditions throughout the last 170 million years. In particular, the boron/calcium ratio of foraminiferal calcite (B/Ca) is an emerging proxy for the seawater carbonate system, which plays a major role in regulating atmospheric CO2 and thus Earth’s climate. In planktic foraminifera, previous culture studies have shown that shell B/Ca increases with seawater pH, which is hypothesized to result from increased incorporation of borate ion (B(OH)4 -) at high pH; increasing pH increases the [B(OH)4 -] of seawater. However, further experiments showed that B/Ca responds to both pH and seawater dissolved inorganic carbon concentration (DIC), leading to the hypothesis that B/Ca is driven by the [B(OH)4 -/DIC] ratio of seawater. Because pH (and thus B(OH)4 -) can be determined via the δ11B composition of foraminiferal calcite, B/Ca therefore may provide an opportunity to determine seawater DIC in the geologic past. The magnesium/calcium ratio (Mg/Ca) of foraminifer shells is a well-established proxy for seawater temperatures, where foraminiferal Mg/Ca increases at greater temperatures. However, foraminifera shell chemistry such as B/Ca and Mg/Ca ratios also depend on the major ion chemistry of seawater. For example, the seawater Mg/Ca ratio (Mg/Casw), which has increased significantly over the last 60 million years, is known to affect the sensitivity of the Mg/Ca proxy to temperature. In addition, the seawater boron concentration ([B]sw) has also increased across the Cenozoic. The dependence of B/Ca proxy relationships on Mg/Casw and [B]sw composition remains unknown. During the Paleogene era (65-34 Ma), Earth’s climate was characterized by a number of rapid warming events termed ”hyperthermals”. Evidence from the sedimentary record suggests that hyperthermals were catalyzed by rapid carbon release and caused widespread ocean acidification and deep-sea deoxygenation. These hyperthermal events present the best geologic analog conditions to anthropogenic climate change, and their study can therefore help to illuminate how the Earth system responds to rapid carbon release and warming. Planktic foraminiferal B/Ca records from the largest hyperthermal event, the Paleocene-Eocene Thermal Maximum (PETM), show a large decrease, which agrees with the theory that ocean acidification should cause B/Ca to decline. However, the decrease is larger than can be reconciled from existing proxy calibrations conducted in modern seawater, begging the question of whether the low Mg/Casw of the Paleogene Ocean affected the sensitivity of B/Ca to the seawater carbonate system. Because there are also a number of outstanding uncertainties regarding the controls on B/Ca- including seawater [Ca] and shell growth rate, light intensity, and phosphate concentration- it is also possible that these factors contributed to the PETM B/Ca excursion. The influence of these additional parameters on B/Ca, as well as the influence of Mg/Casw, needs to be tested in controlled culture experiments. To address these outstanding questions in proxy development, I conducted a series of culture experiments in three living planktic foraminifer species- Orbulina universa, Trilobatus sacculifer, and Globigerinoides ruber (pink). In order to refine our understanding of proxy controls on foraminiferal B/Ca, I investigated how foraminiferal B/Ca is affected by variable light intensity, growth rate (indirectly via seawater [Ca] manipulation), and seawater [B]. Subsequently I tested the influence of low seawater Mg/Ca, analogous to that of the Paleocene ocean, on B/Ca-carbonate chemistry relationships. In Chapters 2 and 3, I detail how my results support the notion that planktic foraminiferal B/Ca in these three symbiont-bearing species is driven by the B(OH)4 -/DIC ratio of seawater and is not compromised by growth rate effects. Furthermore, the sensitivity of B/Ca to B(OH)4 -/DIC is increased under low Mg/Casw in both O. universa and T. sacculifer. In Chapters 2 and 3, I hypothesize that this increased sensitivity is due to decreased cellular pH regulation under low Mg/Casw, leading to a greater sensitivity of the foraminiferal microenvironment’s carbon system to external forcing. I define new culture calibrations that can be applied to records from Paleocene seawater in Chapter 3, and use these calibrations to reconstruct surface ocean DIC and the overall size of the carbon system perturbation across the PETM in Chapter 4. Finally, in Chapter 5, I show how foraminiferal Mg/Ca responds to seawater Mg/Ca and the carbon system from these same experiments, with implications for accounting for carbon system influences on Mg/Ca from early Cenozoic proxy records.

There is general agreement that a range of paleodepths and environments are represented in the individual shell units of the middle Pliocene to earliest Pleistocene Tamiami Formation of southwest Florida, but maximum depths remain poorly constrained. Here, benthic Foraminifera abundances are used as a paleoenvironmental proxy to compare the upper Tamiami from quarries in Sarasota, Florida to Recent modern coastal, bay, and reef habitats of Florida, the Grand Cayman Islands, and Puerto Rico, ranging in depth from 0 to 55 meters. I used: (1) ordination techniques, including detrended correspondence analysis (DCA) and cluster analysis, to compare upper Tamiami foraminiferal assemblages with potential modern analogs; (2) Ammonia-Elphidium (AEI) and FORAM (FI) indices to reconstruct past oxygen levels and environmental stress levels, respectively; and (3) diversity indices and rarefaction to investigate habitat-specific diversity change through time.Results indicate that the upper Tamiami units represent several distinct environments. APAC quarry, Fruitville Member Unit 4 samples group in DCA and cluster analyses with modern shallow, tropical, mangrove-proximate lagoon samples from Puerto Rico; AEI values of both Unit 4 and these lagoonal samples are consistent with high nutrients. APAC quarry, Fruitville Member Unit 3 and Pinecrest Member units 5 and 7, however, group with tropical shallow, open coast environments up to 12 m in depth and have relatively low FORAM indices suggesting stress and AEI values comparable to modern mesotophic, shelf habitats. SMR samples group with modern mangrove environments from White Water Bay at depths approximately 0 to 0.3 m, with FORAM and AEI indices indicating low oxygen and possibly high nutrients. Species richness measured by individual rarefaction in the fossil units is highest in the lowest APAC units sampled and progressively declines in younger APAC units, while SMR beds have the lowest richness of all fossil samples. The lower portion of Unit 7 contains the highest richness of all fossil and modern units, while other fossil units have either lower or comparable richness, diversity, and evenness when compared to modern habitat analogs as identified in cluster and DCA analyses. Thus, there is no clear evidence for wide-scale decline in foraminiferal biodiversity from the Plio-Pleistocene to now. Significantly, the identification of modern habitat analogs for the upper Tamiami units make it possible to compare biodiversity trends in other fauna (e.g., mollusks) thought to have experienced significant extinction.