Clay mineralogy of carbonate-rich sediments of ODP Leg 101 sites

The insoluble residues of samples from ODP Sites 626 and 627 can be subdivided into four groups: (1) illite, 7 A minerals, quartz and feldspar; (2) smectite and zeolite (clinoptilolite); (3) palygorskite and in places sepiolite; and (4) glauconite and pyrite. Whereas group 1 is clearly terrigenous and group 4 authigenic, group 2 is most probably authigenic, as indicated by its abundance in samples with small insoluble residues and its appearance in SEM photographs. Group 3 is authigenic in Albian peritidal dolomite and possibly terrigenous in middle Miocene slumps and debris flows. Smectite crystallinity increases with age. This increase, however, is less pronounced in the Bahamian carbonate-rich samples than in the carbonate-poor silts south of Guatemala (DSDP Leg 84, Sites 569 and 570, the only comparable investigation) as far as can be judged from such a small number of samples.

(Appendix) Oxygen isotope record and carbonate mineralogy of the top part of ODP Hole 101-633A

Hole 633A was drilled in the southern part of Exuma Sound on the toe-of-slope of the southeastern part of Great Bahama Bank during ODP Leg 101. The top 55 m, collected as a suite of six approximately 9.5-m-long hydraulic piston cores, represents a Pliocene-Pleistocene sequence of periplatform carbonate ooze, a mixture of pelagic calcite (foraminifer and coccolith tests), some pelagic aragonite (pteropod tests), and bank-derived fine aragonite and magnesian calcite. A 1.6-m.y.-long hiatus was identified at 43.75 mbsf using calcareous nannofossil biostratigraphy and magnetostratigraphy. The 43.75-m-thick periplatform sequence above the hiatus is a complete late Pliocene-Quaternary record of the past 2.15 m.y. The d18O curve, primarily based on Globigerinoides sacculifera, clearly displays high-frequency/low-amplitude cycles during the early Pleistocene and low-frequency/high-amplitude cycles during the middle and late Pleistocene. Variations in aragonite content in the fine fraction of the periplatform ooze show a cyclic pattern throughout the Pleistocene, as previously observed in piston cores of the upper Pleistocene. These variations correlate well with the d18O record: high aragonite corresponds to light interglacial d18O values, and vice versa. Comparison of the d18O record and the aragonite curve helps to identify 23 interglacial and glacial oxygen-isotope stages, corresponding to 10.5 aragonite cycles (labeled A to K) commonly established during the middle and late Pleistocene (0.9 Ma-present). Strictly based on the aragonite curve, another 11 aragonite cycles, labeled L to V, were identified for the early Pleistocene (0.9 to 1.6 Ma). Mismatches between the d18O record and the aragonite curve occur mainly at some of the glacial-to-interglacial transitions, where aragonite increases usually lag behind d18O depletion. When one visually connects the minima on the Pleistocene aragonite curve, low-frequency (0.4 to 0.5 m.y.) supercycles seem to be superimposed on the high-frequency cycles. The timing of this supercycle roughly matches the timing of the Pleistocene carbonate preservation supercycles described in the Pacific, Indian, and Atlantic oceans. Mismatches between aragonite and d18O cycles are even more obvious for the late Pliocene (1.6 to 2.15 Ma). Irregular aragonite variations are observed for the late Pliocene, although after the onset of late Pleistocene-like glaciations in the North Atlantic Ocean 2.4 m.y. ago the d18O record has shown a mode of high-frequency/low-amplitude cycles. Initiation of climatically induced aragonite cycles occurs only at the Pliocene-Pleistocene transition, 1.6 m.y. ago. After that time, aragonite cycles are fully developed throughout the Quaternary. The 11-m-thick periplatform sequence below the hiatus represents a lower Pliocene interval between 3.75 and 4.45 Ma. The bottom half (4.25-4.45 Ma) has a fairly constant, high aragonite content (averaging 60%) and high sedimentation rates (28 m/m.y.) and corresponds to the end of the prolonged early Pliocene interglacial interval (4.1-5.0 Ma), established as a worldwide high sea-level stand. The second half (3.75-4.25 Ma), in which aragonite content decreases by successive steps, paralleled by a gradual 5180 enrichment in Globigerinoides sacculifera and low sedimentation rates (10 m/m.y), corresponds to the climatic deterioration established worldwide between 4.1 and 3.8 Ma, to a decrease of carbonate preservation observed in the equatorial Pacific Ocean, and to a global sea-level decline. Dolomite, a ubiquitous secondary component in the lower Pliocene, is interpreted as being authigenic and possibly related to diagenetic transformation of primary bank-derived fine magnesian calcite. Transformation of the primary mineralogical composition of the periplatform ooze was evidently minor, as the sediments have retained a detailed record of the Pliocene-Pleistocene climatic evolution. Clear evidence of diagenetic transformations in the periplatform ooze includes (1) the disappearance of magnesian calcite in the upper 20 m of Hole 633A, (2) the occurrence of calcite overgrowths on foraminiferal tests and microclasts at intermittent chalky core levels, and (3) the ubiquitous presence of authigenic dolomite in the lower Pliocene.

Authority and stratification in the Bahamas: The quest for legitimacy

This longitudinal study provides a detailed description of the transition in the Bahamas from British colony to independent country. It analyzes the ongoing process of legitimation and delegitimation of Bahamian political parties and of the transfer of authority from the white minority to the black majority. It is a story of social and political struggles that take place within the quarter century following World War II. These struggles are analyzed within a theoretical framework which focuses on the meaning of symbols used to support claims to authority, and/or which function to delegitimize alternative claims. Specifically, this study looks at the delegitimization of the institutions of colonialism and the concurrent profession of symbols to support both independence and a fully enfranchised democracy in the Bahamas. ^ The research methodology includes an extensive analysis of official British colonial documents, private governmental dispatches, and contemporaneous newspaper articles. The sources were primarily the Public Records Office of Great Britain; the Archives of the Bahamas; and the Institute for Social and Economic Research, University of the West Indies. Secondary literature on civil rights, political science, religion, Black Nationalism, corruption, social theory, and popular culture was studied. Two hundred days of participant observation, spread over seven years of study, resulted in notes from which information was gleaned. During that time, seventeen open-ended interviews with a cross section of Bahamians (male and female, black and white) who lived through this period were recorded, information from which was also incorporated. ^ A detailed description of the socio-historical process, and an analysis of data, demonstrates how the black majority's desire for political representation, and future independence, pressured Great Britain to come into line with the desires of the majority of Bahamians. The symbolic universe that had historically divided white from black now urged dramatic social and political change. ^ The documents and testimonials studied demonstrate how symbols and symbolic events supported and/or undercut the claims to legitimacy proffered by different groups in the Bahamas in their respective attempts to solidify their social and political position within the society. ^

The peopling of the Bahamas: A phylogeographical perspective

During the past 500 years, the Bahamas has been influenced by a wide array of settlers, including but not limited to, the Arawak Indians, Eleutherian Adventurers, British Loyalists, Creole slaves, liberated Africans as well as Chinese, Greek, Jewish, Lebanese, Jamaican and Haitian migrants. To date, however, only a few reports analyzing the genetic makeup and population dynamics of the Bahamas have been published, making this work pivotal in the endeavor to ascertain the genetic ancestry of these groups. As such, the current investigation was undertaken to genetically characterize six of the more densely populated islands throughout the Northwest (Grand Bahama and Abaco) and Central (Eleuthera, Exuma, Long Island and New Providence) Bahamas using different forensic marker systems. When autosomal STR markers are employed, the Bahamian collections were all found to receive differential contributions from the African, European, East Asian and Native American collections utilized in the analyses. Similar findings were also observed for two other Afro-Caribbean populations, Haiti and Jamaica, although the latter populace was found to share a greater proportion of its autosomal component with non-African sources than the former. On the contrary, analysis of the six Bahamian collections using high-resolution Y-chromosome markers identifies genetic signals emanating exclusively from Africans and Europeans, but this is likely the result of smaller sample sizes collected from each island and/or sex-biased gene flow from East Asian and Native American groups.

The influence of body size on the ecology of coastal fish predators in the Bahamas

Body size is a fundamental structural characteristic of organisms, determining critical life history and physiological traits, and influencing population dynamics, community structure, and ecosystem function. For my dissertation, I focused on effects of body size on habitat use and diet of important coastal fish predators, as well as their influence on faunal communities in Bahamian wetlands. First, using acoustic telemetry and stable isotope analysis, I identified high variability in movement patterns and habitat use among individuals within a gray snapper (Lutjanus griseus) and schoolmaster snapper (L. apodus) population. This intrapopulation variation was not explained by body size, but by individual behavior in habitat use. Isotope values differed between individuals that moved further distances and individuals that stayed close to their home sites, suggesting movement differences were related to specific patterns of foraging behavior. Subsequently, while investigating diet of schoolmaster snapper over a two-year period using stomach content and stable isotope analyses, I also found intrapopulation diet variation, mostly explained by differences in size class, individual behavior and temporal variability. I then developed a hypothesis-testing framework examining intrapopulation niche variation between size classes using stable isotopes. This framework can serve as baseline to categorize taxonomic or functional groupings into specific niche shift scenarios, as well as to help elucidate underlying mechanisms causing niche shifts in certain size classes. Finally, I examined the effect of different-sized fish predators on epifaunal community structure in shallow seagrass beds using exclusion experiments at two spatial scales. Overall, I found that predator effects were rather weak, with predator size and spatial scale having no impact on the community. Yet, I also found some evidence of strong interactions on particular common snapper prey. As Bahamian wetlands are increasingly threatened by human activities (e.g., overexploitation, habitat degradation), an enhanced knowledge of the ecology of organisms inhabiting these systems is crucial for developing appropriate conservation and management strategies. My dissertation research contributed to this effort by providing critical information about the resource use of important Bahamian fish predators, as well as their effect on faunal seagrass communities.

Investigating the Effects of Cognitive Apprenticeship-Based Instructional Coaching on Science Teaching Efficacy Beliefs

The overall purpose of this collected papers dissertation was to examine the utility of a cognitive apprenticeship-based instructional coaching (CAIC) model for improving the science teaching efficacy beliefs (STEB) of preservice and inservice elementary teachers. Many of these teachers perceive science as a difficult subject and feel inadequately prepared to teach it. However, teacher efficacy beliefs have been noted as the strongest indicator of teacher quality, the variable most highly correlated with student achievement outcomes. The literature is scarce on strong, evidence-based theoretical models for improving STEB. This dissertation is comprised of two studies. STUDY #1 was a sequential explanatory mixed-methods study investigating the impact of a reformed CAIC elementary science methods course on the STEB of 26 preservice teachers. Data were collected using the Science Teaching Efficacy Belief Instrument (STEBI-B) and from six post-course interviews. A statistically significant increase in STEB was observed in the quantitative strand. The qualitative data suggested that the preservice teachers perceived all of the CAIC methods as influential, but the significance of each method depended on their unique needs and abilities. STUDY #2 was a participatory action research case study exploring the utility of a CAIC professional development program for improving the STEB of five Bahamian inservice teachers and their competency in implementing an inquiry-based curriculum. Data were collected from pre- and post-interviews and two focus group interviews. Overall, the inservice teachers perceived the intervention as highly effective. The scaffolding and coaching were the CAIC methods portrayed as most influential in developing their STEB, highlighting the importance of interpersonal relationship aspects in successful instructional coaching programs. The teachers also described the CAIC approach as integral in supporting their learning to implement the new inquiry-based curriculum. The overall findings hold important implications for science education reform, including its potential to influence how preservice teacher training and inservice teacher professional development in science are perceived and implemented. Additionally, given the noteworthy results obtained over the relatively short durations, CAIC interventions may also provide an effective means of achieving improvements in preservice and inservice teachers’ STEB more expeditiously than traditional approaches.

Carbonate preservation of sediment cores from the Great Bahama Bank

The oceanic carbon cycle mainly comprises the production and dissolution/ preservation of carbonate particles in the water column or within the sediment. Carbon dioxide is one of the major controlling factors for the production and dissolution of carbonate. There is a steady exchange between the ocean and atmosphere in order to achieve an equilibrium of CO2; an anthropogenic rise of CO2 in the atmosphere would therefore also increase the amount of CO2 in the ocean. The increased amount of CO2 in the ocean, due to increasing CO2-emissions into the atmosphere since the industrial revolution, has been interpreted as "ocean acidification" (Caldeira and Wickett, 2003). Its alarming effects, such as dissolution and reduced CaCO3 formation, on reefs and other carbonate shell producing organisms form the topic of current discussions (Kolbert, 2006). Decreasing temperatures and increasing pressure and CO2 enhance the dissolution of carbonate particles at the sediment-water interface in the deep sea. Moreover, dissolution processes are dependent of the saturation state of the surrounding water with respect to calcite or aragonite. Significantly increased dissolution has been observed below the aragonite or calcite chemical lysocline; below the aragonite compensation depth (ACD), or calcite compensation depth (CCD), all aragonite or calcite particles, respectively, are dissolved. Aragonite, which is more prone to dissolution than calcite, features a shallower lysocline and compensation depth than calcite. In the 1980's it was suggested that significant dissolution also occurs in the water column or at the sediment-water interface above the lysocline. Unknown quantities of carbonate produced at the sea surface, would be dissolved due to this process. This would affect the calculation of the carbonate production and the entire carbonate budget of the world's ocean. Following this assumption, a number of studies have been carried out to monitor supralysoclinal dissolution at various locations: at Ceara Rise in the western equatorial Atlantic (Martin and Sayles, 1996), in the Arabian Sea (Milliman et al., 1999), in the equatorial Indian Ocean (Peterson and Prell, 1985; Schulte and Bard, 2003), and in the equatorial Pacific (Kimoto et al., 2003). Despite the evidence for supralysoclinal dissolution in some areas of the world's ocean, the question still exists whether dissolution occurs above the lysocline in the entire ocean. The first part of this thesis seeks answers to this question, based on the global budget model of Milliman et al. (1999). As study area the Bahamas and Florida Straits are most suitable because of the high production of carbonate, and because there the depth of the lysocline is the deepest worldwide. To monitor the occurrence of supralysoclinal dissolution, the preservation of aragonitic pteropod shells was determined, using the Limacina inflata Dissolution Index (LDX; Gerhardt and Henrich, 2001). Analyses of the grain-size distribution, the mineralogy, and the foraminifera assemblage revealed further aspects concerning the preservation state of the sediment. All samples located at the Bahamian platform are well preserved. In contrast, the samples from the Florida Straits show dissolution in 800 to 1000 m and below 1500 m water depth. Degradation of organic material and the subsequent release of CO2 probably causes supralysoclinal dissolution. A northward extension of the corrosive Antarctic Intermediate Water (AAIW) flows through the Caribbean Sea into the Gulf of Mexico and might enhance dissolution processes at around 1000 m water depth. The second part of this study deals with the preservation of Pliocene to Holocene carbonate sediments from both the windward and leeward basins adjacent to Great Bahama Bank (Ocean Drilling Program Sites 632, 633, and 1006). Detailed census counts of the sand fraction (250-500 µm) show the general composition of the coarse grained sediment. Further methods used to examine the preservation state of carbonates include the amount of organic carbon and various dissolution indices, such as the LDX and the Fragmentation Index. Carbonate concretions (nodules) have been observed in the sand fraction. They are similar to the concretions or aggregates previously mentioned by Mullins et al. (1980a) and Droxler et al. (1988a), respectively. Nonetheless, a detailed study of such grains has not been made to date, although they form an important part of periplatform sediments. Stable isotopemeasurements of the nodules' matrix confirm previous suggestions that the nodules have formed in situ as a result of early diagenetic processes (Mullins et al., 1980a). The two cores, which are located in Exuma Sound (Sites 632 and 633), at the eastern margin of Great Bahama Bank (GBB), show an increasing amount of nodules with increasing core depth. In Pliocene sediments, the amount of nodules might rise up to 100%. In contrast, nodules only occur within glacial stages in the deeper part of the studied core interval (between 30 and 70 mbsf) at Site 1006 on the western margin of GBB. Above this level the sediment is constantly being flushed by bottom water, that might also contain corrosive AAIW, which would hinder cementation. Fine carbonate particles (<63 µm) form the matrix of the nodules and do therefore not contribute to the fine fraction. At the same time, the amount of the coarse fraction (>63 µm) increases due to the nodule formation. The formation of nodules might therefore significantly alter the grain-size distribution of the sediment. A direct comparison of the amount of nodules with the grain-size distribution shows that core intervals with high amounts of nodules are indeed coarser than the intervals with low amounts of nodules. On the other hand, an initially coarser sediment might facilitate the formation of nodules, as a high porosity and permeability enhances early diagenetic processes (Westphal et al., 1999). This suggestion was also confirmed: the glacial intervals at Site 1006 are interpreted to have already been rather coarse prior to the formation of nodules. This assumption is based on the grain-size distribution in the upper part of the core, which is not yet affected by diagenesis, but also shows coarser sediment during the glacial stages. As expected, the coarser, glacial deposits in the lower part of the core show the highest amounts of nodules. The same effect was observed at Site 632, where turbidites cause distinct coarse layers and reveal higher amounts of nodules than non-turbiditic sequences. Site 633 shows a different pattern: both the amount of nodules and the coarseness of the sediment steadily increase with increasing core depth. Based on these sedimentological findings, the following model has been developed: a grain-size pattern characterised by prominent coarse peaks (as observed at Sites 632 and 1006) is barely altered. The greatest coarsening effect due to the nodule formation will occur in those layers, which have initially been coarser than the adjacent sediment intervals. In this case, the overall trend of the grain-size pattern before and after formation of the nodules is similar to each other. Although the sediment is altered due to diagenetic processes, grain size could be used as a proxy for e.g. changes in the bottom-water current. The other case described in the model is based on a consistent initial grain-size distribution, as observed at Site 633. In this case, the nodule reflects the increasing diagenetic alteration with increasing core depth rather than the initial grain-size pattern. In the latter scenario, the overall grain-size trend is significantly changed which makes grain size unreliable as a proxy for any palaeoenvironmental changes. The results of this study contribute to the understanding of general sedimentation processes in the periplatform realm: the preservation state of surface samples shows the influence of supralysoclinal dissolution due to the degradation of organic matter and due to the presence of corrosive water masses; the composition of the sand fraction shows the alteration of the carbonate sediment due to early diagenetic processes. However, open questions are how and when the alteration processes occur and how geochemical parameters, such as the rise in alkalinity or the amount of strontium, are linked to them. These geochemical parameters might reveal more information about the depth in the sediment column, where dissolution and cementation processes occur.

What are the effects of the 6 +1 Writing Traits on the Attitudes and Writing Skills of Fifth Grade ELLs?

In the Bahamas, ELLs consist mainly of Haitian descent students. Unfortunately, this demographic of students continuously score below their Bahamian counterparts in Creative Writing. This research examined the affects the 6 + 1 Writing Traits assessment had on the attitudes and writing abilities of fifteen, fifth grade, Haitian descent students.

Investigating the effects of cognitive apprenticeship-based instructional coaching on science teaching efficacy beliefs

The overall purpose of this collected papers dissertation was to examine the utility of a cognitive apprenticeship-based instructional coaching (CAIC) model for improving the science teaching efficacy beliefs (STEB) of preservice and inservice elementary teachers. Many of these teachers perceive science as a difficult subject and feel inadequately prepared to teach it. However, teacher efficacy beliefs have been noted as the strongest indicator of teacher quality, the variable most highly correlated with student achievement outcomes. The literature is scarce on strong, evidence-based theoretical models for improving STEB.^ This dissertation is comprised of two studies. STUDY #1 was a sequential explanatory mixed-methods study investigating the impact of a reformed CAIC elementary science methods course on the STEB of 26 preservice teachers. Data were collected using the Science Teaching Efficacy Belief Instrument (STEBI-B) and from six post-course interviews. A statistically significant increase in STEB was observed in the quantitative strand. The qualitative data suggested that the preservice teachers perceived all of the CAIC methods as influential, but the significance of each method depended on their unique needs and abilities. ^ STUDY #2 was a participatory action research case study exploring the utility of a CAIC professional development program for improving the STEB of five Bahamian inservice teachers and their competency in implementing an inquiry-based curriculum. Data were collected from pre- and post-interviews and two focus group interviews. Overall, the inservice teachers perceived the intervention as highly effective. The scaffolding and coaching were the CAIC methods portrayed as most influential in developing their STEB, highlighting the importance of interpersonal relationship aspects in successful instructional coaching programs. The teachers also described the CAIC approach as integral in supporting their learning to implement the new inquiry-based curriculum. ^ The overall findings hold important implications for science education reform, including its potential to influence how preservice teacher training and inservice teacher professional development in science are perceived and implemented. Additionally, given the noteworthy results obtained over the relatively short durations, CAIC interventions may also provide an effective means of achieving improvements in preservice and inservice teachers’ STEB more expeditiously than traditional approaches.^