Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1986. / Vita. / Includes bibliographical references (leaves 208-215). / A study of the remineralization of organic carbon was conducted in the organic-rich sediments of Buzzards Bay, MA. Major processes affecting the carbon chemistry in sediments are reflected by changes in the stable carbon isotope ratios of dissolved inorganic carbon (XCO2) in sediment pore water. Six cores were collected seasonally over a period of two years. The following species were measured in the pore waters: JC02, &'3 C-2CO2, P04, JH 2S, Alk, DOC, and Ca. Measurements of pore water collected seasonally show large gradients with depth, which are larger in summer than in winter. The 613C (PDB) of IC02 varies from 1.3 o/oo in the bottom water to approximately -10 o/oo at 30 cm. During all seasons, there was a trend towards more negative values with depth in the upper 8 cm due to the remineralization of organic matter. There was a trend toward more positive values below 8 cm, most likely due to biological irrigation of sediments with bottom water. Below 16-20 cm, a negative gradient was re-established which indicates a return to remineralization as the main process affecting pore water chemistry. Using the XC02 depth profile, it was estimated that 67-85 gC/m 2 are oxidized annually and 5 gC/m 2-yr are buried. The amount of carbon oxidized represented remineralization occurring within the sediments. This estimate indicated that approximately 20% of the annual primary productivity reached the sediments. The calculated remineralization rates varied seasonally with the high of 7.5 x 10-' mol/L-sec observed in August 84 and the low (0.6 x 10-) in December 83. The calculated remineralization rates were dependent on the amount of irrigation in the sediments; if the irrigation parameter is known to ±20%, then the remineralization rates are known to this certainty also. The amount of irrigation in the sediments was estimated using the results of a seasonal study of 2 2 2Rn/ 22 'Ra disequilibria at the same study site (Martin, 1985). Estimates of the annual remineralization in the sediments using solid-phase data indicated that the solid-phase profiles were not at steady-state concentrations. The isotopic signature of 2C02 was used as an indicator of the processes affecting IC02 in pore water. During every month, the oxidation of organic carbon to C02 provided over half of the carbon added to the IC02 pool. However, in every month, the 6'"C of XCO2 added to the pore water in the surface sediments was greater than -15 o/oo, significantly greater than the 613C of solid-phase organic carbon in the sediments (-20.6 o/oo). The 613C of IC02 added to the pore water in the sediments deeper than 7 cm was between -20 and -21 o/oo, similar to the organic carbon in the sediments. Possible explanations of the 1 3C-enrichment observed in the surface sediments were: a) significant dissolution of CaC0 3 (613C = +1.7 o/oo) b) the addition of significant amounts of carbonate ion from bottom water to pore water c) an isotopic difference between the carbon oxidized in the sediments and that remaining in the sediments. The effect of CaC0 3 dissolution was quantified using measured dissolved Ca profiles and was not large enough to explain the observed isotopic enrichment. An additional source of 13C-enriched carbon was bottom water carbonate ion. In every month studied, there was a net flux of 2C0 2 from pore water to bottom water. The flux of pore water 2C02 to bottom water ranged from a minimum of 10 x 10-12 mol/cm 2 -sec in December 83 to a maximum of 50 x 10-12 mol/cm2-sec in August 84. However, because the pH of bottom water was about 8 while that of the pore water was less than or equal to 7, the relative proportion of the different species of inorganic carbon (H2CO, HCO-, C0~) was very different in bottom water and pore water. Thus, while there was a net flux of IC0 2 from pore water to bottom water, there was a flux of carbonate ion from bottom water to pore water. Because bottom water JC02 was more 13C-enriched than pore water JC0 2, the transfer of bottom water carbonate ion to pore water was a source of 13C-enriched carbon to the pore water. If the &'3C of CO2 added to the pore water from the oxidation of organic carbon was -20.6 o/oo, then the flux of C3% from bottom water to pore water must have been 10-30% of the total flux of 2C02 from pore water to bottom water. This is consistent with the amount calculated from the observed gradient in carbonate ion. Laboratory experiments were conducted to determine whether the 613C of C02 produced from the oxidation of organic carbon (613C-OCOX) was different from the 613C of organic carbon in the sediments (613C-SOC). In the laboratory experiments, mud from the sampling site was incubated at a constant temperature. Three depths were studied (0-3, 10-15, and 20-25 cm). For the first study (IEl), sediment was stirred to homogenize it before packing into centrifuge tubes for incubation. For the second study (IE2), sediment was introduced directly into glass incubation tubes by subcoring. The second procedure greatly reduced disturbance to the sediment. Rates of C02 production were calculated from the concentrations of 2C02 measured over up to 46 days. In both studies, the values of Re in the deeper intervals were about 10% of the surface values. This was consistent with the field results, although the rates decreased more rapidly in the field. In all cases, the remineralization rates during the beginning of IEl were much greater than those at the beginning of IE2. The sediment for IEl was collected in February 84. The measured value of Rc in the surface sediment of the laboratory experiment (24 x 10- mol/L-sec) was much greater than the value of Rc observed in the field in another winter month, December 83 (.62 x 10~9). The sediment for IE2 was collected in August 85. The measured values of Re in the surface sediment (6.6-12 x 10~9 mol/L-sec) were consistent with the field values from August 84 (7.5 x 10-9). The XC02 results indicated that IE2 reproduced field conditions more accurately than IEl did. The isotopic results from the experiments strongly suggested that 613C-OCOX in the surface sediments (-17.8 o/oo ± 1.9 o/oo) was greater than 6'3C-SOC (-20.6 ± 0.2 o/oo). The magnitude of the observed fractionation was small enough that the observed values of 613C-C02 in the pore waters could be explained by fractionated oxidation coupled with the diffusion of carbonate ion from bottom water to pore water. The observed fractionation was most likely due to the multiple sources of organic carbon to coastal sediments. A study of the natural levels of radiocarbon in these sediments indicated that the carbon preserved in the sediments is approximately 30% terrestrial while the rest is from phytoplankton. / by Ann P. McNichol. / Ph.D.

Thesis (MSc)--University of Stellenbosch, 1989. / AFRIKAANSE OPSOMMING: Senosoiese sedimente langs die suidooskus van die Kaapprovinsie is periodiek deur verskeie outeurs vir meer as 'n eeu bestudeer. In hierdie aanbieding word die Iiteratuur saamgevat en vele dubbelsinnige stratigrafiese onderverdelings en definisies opgeklaar. Die Senosoiese afsettings kan volgens oorsprong geklassifiseer word as marien, eolies en fluviaal. Die mariene afsettings, synde strand-, nabystrand-, estuarien of lagunale afsettings geassosieerd met transgressiewe/ regressiewe kusIyne, word nou op grond van kenmerkende litologiese, paleontologiese sowel as ouderdomsverskille onderverdeel in die Paleogeen Bathurst, Neogeen Alexandria en Kwaternere Salnova Foraasies. Die Laat-Plioseen tot Vroeg-Pleistoseen Nanaga Formasie, Middel- tot Laat- Pleistoseen Nahoon Formasie en die Holoseen Schel• Hoek Formasie vorm die kus-eoliese afsettings. AI die mariene en marienverwante (eoliese} formasies, gekenmerk deur kalkige klastiese afsettings, is saamgegroepeer in 'n nuutgedefinieerde Algoa Groep. Fluviale afsettings word onderverdeel in die Martindale, Kinkelbos, Bluewater Bay, Kudus Kloof en Sunland Formasies. Die onderskeie afsettings word gekorreleer met verskillende seevlakstande deur geologiese tye. Die vroegste Senosoiese transgressiewe/regressiewe siklus het in die Vroeg-Paleoseen begin en die hoogste aangetekende elevasie vir die era bereik. Die Bathurst Formasie is waarskynlik gedurende hierdie regressie afgeset. 'n Tweed~ kleiner transgressie/ regressiesiklus het plaasgevind gedurende die Laat-Eoseen tot Vroeg-Oligoseen. Sover tans bekend, kan geen afsetting in die dagsoomgebied van die Algoa Groep definitief met hierdie siklus in verband gebring word nie. Die volgende siklus, wat 'n transgressiewe maksimum van c. 250 m bereik het, het begin in die Middel-Mioseen en verstryk in die Vroee Plioseen. Mariene planasie van die kusplatform het gedurende die transgressie plaasgevind terwyl die Alexandria Formasie wat tans bo 120 m geleë is, gedurende die regressie afgeset is. Die Vroeg-Plioseen transgressie het waarskynlik 'n maksimum huidige hoogte van c. 120 m bereik, waartydens o.a. die 120 m branderstoep en "Humansdorpterras" gekerf is. Die Alexandria Formasie tans geleë tussen 60 en 120 m, is afgeset gedurende die Laat-Plioseen regressie. Hierdie regressie het verskeie relatief lang stilstande, wat waarskynlik die 106-m, 90- tot 100-m en 84-m branderstoepe verklaar, ondervind. Selfs die 60-m en 52-m kuslyne kon tydens hierdie regressie gevorm het. Voorlopige paleontologiese getuienis dui egter daarop dat die 60-m kuslyn 'n transgressiewe maksimum van 'n daaropvolgende siklus verteenwoordig, gevolg deur 'n regressie met minstens een beduidende stilstand by 52 m. Die Alexandria Formasie geleë tussen c. 60 en 30 m, is waarskynlik gedurende hierdie regressie gedeponeer, waartydens ook die Bluewater Bay, Kinkelbos en Kudus Kloof Formasies afgeset is. Gedurende die Kwaternêre transgressie/regressiesiklusse, waarvan minstens vier aangedui word, is die Salnova Formasie (afwesig bo 30 m) afgeset. Die Nahoon Formasie, wat ook op groot skaal op die kontinentale bank ontwikkel is, is gedeponeer gedurende die laaste twee Pleistoseen glasiale toe seevlakke tot benede -100 m gedaal het. Die Schelm Hoek Formasie wat tans nog afgeset word, het ontstaan uit die transgressiewe maksimum van die Flandriese transgressie aan die begin van die Holoseen. / ENGLISH ABSTRACT: Cenozoic sediments along the south-east coast of the Cape Province have been studied intermittently for more than a century by various authors. In this presentation the literature is reviewed and many ambiguous stratigraphic subdivisions and definitions are clarified. The Cenozoic deposits can be classified, according to origin, as marine, aeolian and fluvial. The marine deposits, being lagoonal deposits either beach, nearshore, estuarine or associated with transgressive/regressive shorelines, are now subdivided on the grounds of distinct lithological, palaeontological as well as age differences into the Palaeogene Bathurst, Neogene Alexandria and Quaternary Salnova Formations. The Late Pliocene to Early Pleistocene Nanaga Formation, the Hiddle to Late Pleistocene Nahoon Formation and the Holocene Schelm Hoek Formation constitute the coastal and marine-related aeolian deposits. All the marine (aeolian) formations, which are characterised by calcareous clastics, have been grouped together in a newly defined Algoa Group. Fluvial deposits are subdivided into the Martindale, Kinkelbos, Bluewater Bay, Kudus Kloof and Sunland Formations. The various deposits are correlated with different stands of sea-level through geological time. The earliest Cenozoic transgression/regression cycle started in the Early Palaeocene and reached the highest recorded altitude for the era. The Bathurst Formation was probably deposited during this regression. A second lesser transgression/regression cycle occurred in the Late Eocene to Early Oligocene. As far as is presently known, no deposit in the outcrop area of the Algoa Group can be definitely related to this cycle. The next cycle, which reached a transgressive maximum of c. 250 m, started in the Middle Miocene and terminated in the Early Pliocene. Marine planation of the coastal platform took place during the transgression, whilst the Alexandria Formation presently situated above 120 m, was deposited during the regression. The Early Pliocene transgression is considered to have reached a maximum present-day elevation of c. 120 m, during which the 120 m marine bench and "Humansdorp Terrace", amongst others, were carved. The Alexandria Formation presently situated between 60 and 120 m, was deposited during the Late Pliocene regression, which experienced several relatively long stillstands which probably account for the 106 m, 90 t.o 100 m and 8.4 m benches. Even the 60 m- and 52 m-shorelines could have been formed during this regression. Preliminary palaeontological evidence, however, suggests that the 60 m shoreline represents a transgressive maximum of a subsequent cycle followed by a regression with at least one significant stillstand at 52 m. The Alexandria Formation situated between c. 60 and 30 m, was probably deposited during this regression, which also saw the deposition of the Bluewater Bay, Kinkelbos and Kudus Kloof Formations. During the Quaternary transgression/regression cycles, of which at least four are indicated, the Salnova Formation (absent above 30 m) was deposited. The Nahoon Formation, which is also extensively developed on the continental shelf, was deposited during the last two Pleistocene glacials, when sea-levels receded to less than -100 m. The Schelm Hoek Formation, which is still being deposited, originated from the transgressive maximum of the Flandrian transgression at the start of the Holocene.

Measuring the impact of physical disturbance on macrofaunal communities and sediment composition is important given the increased demand for the exploitation and disturbance of marine ecosystems. The aim of the present investigation was to provide a comprehensive study about the extent to which the disturbance (especially aggregate dredging) may affect benthic ecosystem function. The first part of the thesis concerns a field investigation of the impacts of dredging on the benthic community and related ecosystem function which was measured by different approaches including traditional methods based on benthic community structure and a more novel approach based on the functional traits of benthic organisms. The assessment was done by comparing dredged sites (Area 222, southeast England) with nearby undisturbed reference sites from the years 2001 to 2004 and in 2007. In general, low dredging intensity did not appear to impose great impacts on the benthic community and related ecosystem function compared to the higher intensity activity. Most of the analyses suggested that the community at the high dredging intensity site had yet to recover at the end of this study period. Among many factors related to the recovery of the benthic community was sediment composition where gravel deposits appeared to support a faster biological recovery. Meanwhile, the recovery of species with specific traits, such as tube-building and filter feeding also indicate a faster recovery for the whole community. The experimental work to determine different impacts of Hediste diversicolor on its surrounding depending on its relative size is discussed in Appendix 1.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2014. / The Karasburg Basin is situated in southern Namibia and preserves a heterogeneous succession of Karoo Supergroup strata up to 1000m thick. The uppermost preserved succession in this basin is the Amibberg Formation which is 250m thick and consists of intervals of sandstone, siltstone and mudstone. This study uses facies analysis, sequence stratigraphy and petrography to determine the palaeogeography and provenance for the Amibberg Formation. This is then used to establish environmental variability across the Karasburg – Aranos – Main Karoo basins and to define an equivalent of the Amibberg Formation in the Main Karoo Basin. Detailed stratigraphic logging of five outcrop localities has led to the identification of seven distinct lithofacies and two dominant ichnofacies (Cruziana and Skolithos). These lithofacies include: 1) Massive, laminated and bioturbated mudstones interpreted as offshore deposits (OS); 2) Bioturbated siltstones and sandstones which are representative of offshore-transitional environments (OST); 3) Interbedded sandstones and siltstones also interpreted as offshore-transitional deposits (OST) and generated by river-fed hyperpycnal plumes; 4) Sharp based, massive sandstones interpreted as being deposited on the distal lower shoreface (dLSF); 5) Non-amalgamated hummocky cross-stratified (HCS) and wave rippled sandstones interpreted as distal lower shoreface deposits (dLSF); 6) Amalgamated HCS and wave rippled sandstones interpreted as proximal lower shoreface deposits (pLSF); and 7) Soft-sediment deformed (SSD) sandstones and siltstones occurring in close juxtaposition with dLSF and pLSF deposits. The vertical arrangement of these lithofacies shows a general coarsening and shallowing upward trend. Overall the rocks of the Amibberg Formation consist of wave-dominated shoreface deposits with significant influence by tidal processes. Petrographically, the sandstone samples fall into the class of quartz and feldspathic wackes and are sourced from craton interior provenances. Geochemical analysis of mudstones and nodules indicate high levels of microbial activity under predominantly oxic conditions during the deposition of the Amibberg Formation. Five poorly defined 4th order T-R cycles are observable within the strata of the Amibberg Formation. Large regressive intervals are capped by thin transgressive tracts and these cycles are interpreted to have formed due to eustatic processes. Overall, the Amibberg Formation represents a regressive shoreline. iii Based on the mean palaeocurrent vectors a NNE-SSW palaeoshoreline orientation is deduced and the shoreface must have occupied a palaeohigh on the northern side of the western Cargonian Highlands. This emergent highland acted as an extensive headland and assisted in the connectivity of the Karasburg and Aranos basins, with partial connectivity with the Main Karoo Basin during the Early Permian. Based on this study, the Amibberg Formation is considered an equivalent of the Waterford Formation in the Main Karoo Basin based on similar: stratigraphic position; thickness; sedimentary structures; trace fossil assemblages and stacking patterns.

Os radionuclídeos naturais das séries radioativas do 238U e do 232Th têm sido aplicados com sucesso como traçadores de processos ambientais atuais e mudanças climáticas. O 210Pb (meia-vida de 22,2 anos) é empregado na técnica de datação geocronológica de testemunhos sedimentares dos últimos 100-150 anos e na determinação de taxa de sedimentação. As concentrações dos isótopos 226Ra e 228Ra (meia-vida de 1.600 anos e 5,75 anos, respectivamente) auxiliam no cálculo das atividades de 210Pb em excesso no sedimento e auxiliam na identificação de processos marinhos importantes, como, por exemplo, a intrusão de água subterrânea. Neste trabalho foram quantificadas as concentrações de atividade de 226Ra, 228Ra e 210Pb em quatro testemunhos marinhos curtos coletados desde a plataforma continental até o talude superior do Atlântico Sudoeste. A partir dos resultados obtidos, as taxas de sedimentação em cada local e as idades de cada fatia de sedimento foram determinadas pelo método de datação geocronológica com 210Pb. As amostras sedimentares sofreram digestão total ácida em microondas. A separação radioquímica sequencial de 226Ra, 228Ra e 210Pb foi realizada com a obtenção dos precipitados de Ba(Ra)SO4 e PbCrO4. As medidas α total do 226Ra e β total do 228Ra e do 210Pb a partir dos precipitados foram feitas em um detector proporcional de fluxo gasoso de baixa radiação de fundo. Com relação aos testemunhos analisados, as concentrações de atividade dos radionuclídeos variaram de 14 Bq.kg-1 a 154 Bq.kg-1 para o 226Ra; de 17 Bq.kg-1 a 45 Bq.kg-1 para o 228Ra; de 20 Bq.kg-1 a 2.073 Bq.kg-1 para o 210Pb. Valores altos de 210Pb foram encontrados no topo de todos os perfis sedimentares, proveniente principalmente da deposição atmosférica. Os dados coletados neste trabalho estão na mesma faixa de grandeza de outros relacionados a medições de 226Ra, 228Ra, 210Pb em áreas não contaminadas do Oceano Atlântico Sudoeste. As taxas de sedimentação diminuíram com o aumento da profundidade de coluna dágua, cujos valores variaram de 0,049 cm.ano-1 a 0,40 cm.ano-1. / Natural radionuclides from 238U and 232Th series have been successfully applied as tracers of environmental process and climate changes. The 210Pb (half-life of 22.2 years) is used in the geochronological dating technique of sediment cores of the last 100-150 years, and its respective sedimentation rate determination. The study of 226Ra and 228Ra concentrations (half-lives of 1,600 years and 5.75 years, respectively) helps calculate the activity of 210Pb in excess in the environment, besides being important tracers of marine processes, as ground water discharge. In this work it was determined the activity concentrations of 226Ra, 228Ra and 210Pb in four short marine cores collected since the continental platform to upper slope of Southwest Atlantic Ocean. Taking into account the results obtained, sedimentation rates and the ages of each sediment layer were determined using the geochronological dating method with 210Pb. All sediment samples were total acid digested in microwave. The sequential radiochemical separation of 226Ra, 228Ra, 210Pb were performed, obtaining in the end the precipitation of Ba(Ra)SO4 and PbCrO4. The gross α measurements of 226Ra and gross β measurements of 228Ra and 210Pb from the precipitates were carried out in a gas-flow low background proportional counter. Concerning all cores analyzed, the activities concentrations of 226Ra ranged from 14 Bq.kg-1 to 154 Bq.kg-1; the concentrations of 228Ra ranged from 17 Bq.kg-1 to 45 Bq.kg-1; and the concentrations of 210Pb ranged from 20 Bq.kg-1 to 2,073 Bq.kg-1. High values of 210Pb were observed on the top of all the cores studied, mainly related to atmospheric deposition. The results obtained in this work were of the same order of magnitude of those reported in the literature available on non contaminated areas of Southeast Brazilian Coast. Sedimentation rates fall with the increase of water column depth and ranged from 0,049 cm.ano-1 to 0.40 cm.y-1.

Os radionuclídeos naturais das séries radioativas do 238U e do 232Th têm sido aplicados com sucesso como traçadores de processos ambientais atuais e mudanças climáticas. O 210Pb (meia-vida de 22,2 anos) é empregado na técnica de datação geocronológica de testemunhos sedimentares dos últimos 100-150 anos e na determinação de taxa de sedimentação. As concentrações dos isótopos 226Ra e 228Ra (meia-vida de 1.600 anos e 5,75 anos, respectivamente) auxiliam no cálculo das atividades de 210Pb em excesso no sedimento e auxiliam na identificação de processos marinhos importantes, como, por exemplo, a intrusão de água subterrânea. Neste trabalho foram quantificadas as concentrações de atividade de 226Ra, 228Ra e 210Pb em quatro testemunhos marinhos curtos coletados desde a plataforma continental até o talude superior do Atlântico Sudoeste. A partir dos resultados obtidos, as taxas de sedimentação em cada local e as idades de cada fatia de sedimento foram determinadas pelo método de datação geocronológica com 210Pb. As amostras sedimentares sofreram digestão total ácida em microondas. A separação radioquímica sequencial de 226Ra, 228Ra e 210Pb foi realizada com a obtenção dos precipitados de Ba(Ra)SO4 e PbCrO4. As medidas α total do 226Ra e β total do 228Ra e do 210Pb a partir dos precipitados foram feitas em um detector proporcional de fluxo gasoso de baixa radiação de fundo. Com relação aos testemunhos analisados, as concentrações de atividade dos radionuclídeos variaram de 14 Bq.kg-1 a 154 Bq.kg-1 para o 226Ra; de 17 Bq.kg-1 a 45 Bq.kg-1 para o 228Ra; de 20 Bq.kg-1 a 2.073 Bq.kg-1 para o 210Pb. Valores altos de 210Pb foram encontrados no topo de todos os perfis sedimentares, proveniente principalmente da deposição atmosférica. Os dados coletados neste trabalho estão na mesma faixa de grandeza de outros relacionados a medições de 226Ra, 228Ra, 210Pb em áreas não contaminadas do Oceano Atlântico Sudoeste. As taxas de sedimentação diminuíram com o aumento da profundidade de coluna dágua, cujos valores variaram de 0,049 cm.ano-1 a 0,40 cm.ano-1. / Natural radionuclides from 238U and 232Th series have been successfully applied as tracers of environmental process and climate changes. The 210Pb (half-life of 22.2 years) is used in the geochronological dating technique of sediment cores of the last 100-150 years, and its respective sedimentation rate determination. The study of 226Ra and 228Ra concentrations (half-lives of 1,600 years and 5.75 years, respectively) helps calculate the activity of 210Pb in excess in the environment, besides being important tracers of marine processes, as ground water discharge. In this work it was determined the activity concentrations of 226Ra, 228Ra and 210Pb in four short marine cores collected since the continental platform to upper slope of Southwest Atlantic Ocean. Taking into account the results obtained, sedimentation rates and the ages of each sediment layer were determined using the geochronological dating method with 210Pb. All sediment samples were total acid digested in microwave. The sequential radiochemical separation of 226Ra, 228Ra, 210Pb were performed, obtaining in the end the precipitation of Ba(Ra)SO4 and PbCrO4. The gross α measurements of 226Ra and gross β measurements of 228Ra and 210Pb from the precipitates were carried out in a gas-flow low background proportional counter. Concerning all cores analyzed, the activities concentrations of 226Ra ranged from 14 Bq.kg-1 to 154 Bq.kg-1; the concentrations of 228Ra ranged from 17 Bq.kg-1 to 45 Bq.kg-1; and the concentrations of 210Pb ranged from 20 Bq.kg-1 to 2,073 Bq.kg-1. High values of 210Pb were observed on the top of all the cores studied, mainly related to atmospheric deposition. The results obtained in this work were of the same order of magnitude of those reported in the literature available on non contaminated areas of Southeast Brazilian Coast. Sedimentation rates fall with the increase of water column depth and ranged from 0,049 cm.ano-1 to 0.40 cm.y-1.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2006. / Includes bibliographical references. / South American climate has undergone dramatic changes since the last glacial period, as evidenced from Cariaco Basin (Venezuelan coast) and Peru Margin marine sediment biomarker records. Compounds derived from vascular plant leaf waxes and delivered to the marine sedimentary environment, including long-chain (C24-C32) n-alkanoic acids, were used as proxies for terrestrial vegetation type, aridity, and atmospheric circulation. Marine biomarkers, such as sterols and phytol, were used to reconstruct productivity in the Peru Margin upwelling zone, where sedimentary conditions are not conducive to the preservation of foraminifera. Through the use of organic molecular isotopic techniques and multi-molecular stratigraphy, a great deal can be learned about communities of marine organisms and terrestrial plants that existed in the past and the environments in which they lived. Vascular plant leaf wax carbon and hydrogen isotopic records were generated from n-alkanoic acids preserved in Cariaco Basin marine sediments. These records were compared to previously established pollen and climate records and were found to parallel local millennial-scale climate changes between the late Glacial and Preboreal periods, which were characterized by migrations of the inter-tropical convergence zone. / (cont.) Differences in 6D between C,6-C18 and C24-C30 n-alkanoic acids suggest a marine source for the shorter chain lengths and a terrestrial source for the longer chains. Stacked 6D and 613C records both exhibited isotopic enrichment during the late Glacial and Younger Dryas periods and depletion during the B011ing-Aller0d and Preboreal periods. If interpreted as an aridity proxy, the 6D record is in agreement with Cariaco Basin sediment grey scale records, suggesting that the late Glacial and Younger Dryas were more arid than the B011ing-Aller0d and Preboreal periods. n-Alkanoic acid 613C, which is a proxy for C3 versus C4 plant type, indicates that C3 plants predominated in this area of the tropics during warm and wet periods, such as the Bolling-Aller0d and the Holocene, and C4 plants proliferated during cooler and more arid periods, such as the Glacial and Younger Dryas. The biomarker 613C record agrees with pollen data previously developed from Cariaco Basin sediments, confirming that leaf wax compounds preserved in marine sediments can accurately record terrestrial vegetation changes. Analytical methods utilizing stir bar sorptive extraction (SBSE) and thermal desorption were developed and applied to investigate lipid organic matter in a suite of alpine ice cores. / (cont.) These methods permit use of small volume (10-30 ml) samples, as would be required for high-resolution down-core analyses. SBSE involves using a polymer coated stir bar to extract organic matter from aqueous samples, after which it is loaded directly into a thermal desorption unit and the organic matter transferred in its entirety to a gas chromatograph inlet. To test these methods and the organic content of tropical ice, post-industrial samples from two South American, two Asian, and one African ice core were analyzed. Compounds identified in the modem ice core samples included natural and anthropogenic biomarkers such as n-alkanes, n-alkanoic acids, n-alkyl amides and nitriles, polycyclic aromatic hydrocarbons (PAHs), and diterpenoids. Variability in the distributions of these compounds between different cores demonstrated that the lipid organic fraction in each core was representative of mostly local inputs. To further investigate natural inputs, several pre-industrial samples were analyzed from the Sajama ice core in the Andes and The Puruogangri core on the Tibetan Plateau. Inputs of terrestrial vegetation combustion biomarkers such as PAHs, diterpenoids, and alkyl amides were consistent with periods of enhanced aridity in each core. / (cont.) The results of this investigation demonstrate the utility of the methodology, which could now be applied to generate very high-resolution biomarker records from tropical ice cores. Gas chromatography/time-of-flight mass spectrometry (GC/TOF-MS) was used to generate a high-resolution, multi-molecular organic biomarker record from Peru Margin sediments (-110S, 252 m water depth) for the last 15 ka. Because of their position beneath the oxygen minimum zone of a productive upwelling region, these sediments contain a wealth of compounds that can be exploited as paleoclimate indicators. TOF-MS and fast GC techniques allowed me to generate this record in a short amount of time and without employing the traditional suite of purification techniques. Before about 9 ka, organic carbon and biomarker concentration records exhibited similar variability, implying a forcing mechanism that affected input and/or preservation of both marine and terrestrial organic matter, such as large-scale climate change. ... / by Matthew C. Makou. / Ph.D.

Permafrost soils in the Arctic store large quantities of organic matter, roughly twice the amount of carbon that was present in the atmosphere before the industrial revolution. This freeze-locked carbon pool is susceptible to thawing caused by amplified global warming at high latitudes. The remobilization of old permafrost carbon facilitates its degradation to carbon dioxide and methane, thereby providing a positive feedback to climate change. Accelerating coastal erosion in addition to projected rising river discharge with enhancing sediment loads are anticipated to transport increasing amounts of land-derived organic carbon (OC) to the Arctic Ocean. On its shallow continental shelves, this material may be remineralized in the water column or in the sediments, transported without being altered off shelf towards the deep sea of the Arctic Interior or buried in marine sediments and hence sequestered from the contemporary carbon cycle. The fate of terrigenous material in the marine environment, though offering potentially important mechanisms to either strengthen or attenuate the permafrost-carbon climate feedback, is so far insufficiently understood. In this doctoral thesis, sediments from the wide East Siberian Arctic Shelf, the world’s largest shelf-sea system, were used to investigate some of the key processes for OC cycling. A range of bulk sediment properties, carbon isotopes and molecular markers were employed to elucidate the relative importance of different organic matter sources, the role of cross-shelf transport and the relevance of degradation during transport and after burial. Overall, OC released from thawing permafrost constitutes a significant proportion of the sedimentary organic matter on the East Siberian Arctic Shelf. Two sediment cores from the inner and outer East Siberian Sea recorded no substantial changes in source material or clear trends in degradation status for the last century. With increasing distance from the coast, however, strong gradients were detected towards lower concentrations of increasingly reworked land-derived OC. The time spent during cross-shelf transport was consequently found to exert first-order control on degradation. Compound-specific radiocarbon dating on terrigenous biomarkers revealed a net transport time of ~4 000 years across the 600 km wide Laptev Sea shelf, yielding degradation rate constants for bulk terrigenous OC and specific biomarkers on the order of 2-4 kyr-1. From these results, the carbon flux released by degradation of terrigenous OC in surface sediments was estimated to be ~1.7 Gg yr-1, several orders of magnitude lower than what had been quantified earlier for dissolved and particulate OC in the water column. Lower oxygen availability and close associations with the mineral matrix may protect sedimentary OC from remineralization and thereby weaken the permafrost-carbon feedback to present climate change. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Manuscript.</p>

This study aims to unravel the ecological and evolutionary dynamics within the calcareous nannofossil communities at the Eocene/Oligocene (E/O) transition and during the Oligocene time when Cenozoic 'icehouse' conditions were established. The main question this study aims to answer is whether the changes in the nannofossil assemblages were controlled by intrinsic evolutionary trends or if the changes were controlled by environmental factors such as changes in temperature and nutrient availability in the surface water. These questions are addressed with detailed analyses of the taxonomy, biostratigraphy and fluctuations in abundance and diversity of calcareous nannofossil assemblages from a continuous latest Eocene through Oligocene sediment section from the ODP Site 1218 (8°53.38´N, 135°22.00´W), paleo-equatorial Pacific Ocean. An improved nannofossil taxonomy and biostratigraphy has been established. At the E/O transition, changes in the nannofossil preservation mimics changes in calcium carbonate content. A detailed investigation of late Eocene and Oligocene sediments yields age estimates for ten nannofossil bioevents. Morphometric studies of the Reticulofenestra umbilicus-R. hillae show that these cannot be subdivided into two different morphospecies. Based on different morphometry and stratigraphic ranges, the Oligocene Sphenolithus lineage appears to be the result of a combined anagenetic and cladogenetic evolution. A new nannolith species is described: Triquetrorhabdulus longus. High-resolution nannofossil data indicate changes in the composition, abundance and diversity of the mid-Oligocene assemblages. Intervals of high diversity index coincide with Oi-glaciation events. However, visual examination of the variations in abundance of nannofossil taxa do not appear to correlate with changes in either oxygen or carbon isotopes. This presumably indicates that a dynamic equilibrium did not exist between these Oligocene nannoplankton assemblages and changes in surface water temperature or productivity conditions. / Doctoral Thesis in Marine Geoscience at Stockholm University, Sweden 2009

Το λιμάνι του Πειραιά είναι το πιο σημαντικό της Ελλάδας και ένα από τα σπουδαιότερα της Μεσογείου. Στην ευρύτερη περιοχή του λιμανιού λαμβάνουν χώρα ένα πλήθος από δραστηριότητες που επιβαρύνουν σημαντικά το λιμάνι σε βαρέα μέταλλα. Σκοπός της εργασίας αυτής είναι ο προσδιορισμός βαρέων μετάλλων σε επιφανειακά ιζήματα από το επιβατικό τμήμα του λιμανιού του Πειραιά. Στην αρχή γίνεται μια εισαγωγή για τα βαρέα μέταλλα και το ρόλο τους στα θαλάσσια ιζήματα. Ακολουθεί βιβλιογραφική ανασκόπηση που σχετίζεται με την παρουσία βαρέων μετάλλων σε θαλάσσια ιζήματα που έχουν συλλεχθεί από διάφορα λιμάνια με ποικίλες δραστηριότητες ανά τον κόσμο. Μετά από κάποια γενικά στοιχεία για το λιμάνι του Πειραιά, αναφέρονται στοιχεία της γεωλογίας της περιοχής μελέτης. Στην συνέχεια ακολουθεί περιγραφή των εργασιών πεδίου και γίνεται εκτενής αναφορά στην μεθοδολογία των χημικών αναλύσεων που εφαρμόστηκαν. Στους πυρήνες που συλλέχθηκαν έγιναν κοκκομετρικές αναλύσεις, προσδιορισμός οργανικού άνθρακα και προσδιορισμός συγκεντρώσεων βαρέων μετάλλων. Χρησιμοποιήθηκε η ολική διάσπαση (HF - HNO3 - HClO4) για τον προσδιορισμό των ολικών συγκεντρώσεων των μετάλλων και επίσης χρησιμοποιήθηκε η διαδοχική εκχύλιση για τον προσδιορισμό της χημικής κατανομής των μετάλλων στις διάφορες φάσεις των ιζημάτων και για την αποτίμηση της κινητικότητας τους. Τα αποτελέσματα των παραπάνω αναλύσεων έδειξαν την αρκετά σημαντική επιβάρυνση του λιμανιού σε βαρέα μέταλλα και προσδιόρισαν την κινητικότητα συγκεκριμένων μετάλλων. / The Port of Piraeus is the most important port in Greece as well as one of the important ports around the Mediterranean Sea. A lot of activities (commercial, industrial et.c) load the given port with a huge variety of heavy metals. The aim of this study is to determine the heavy metals in surface sediments from the passenger part of Port of Piraeus. At the beginning of the study there is an introduction of heavy metals and their role in marine sediments. A bibliographical review follows which is relevant to the presence of heavy metals found in marine sediments which have been collected from several ports around the world with various activities. Some data about the port is given, and then, takes place references for the geology of study area. Then, a description of field works and a detailed report of the methodology used for chemicals analysis follow. In the cores that were sampled, have been applied, grain size distribution and concentrations of heavy metals and organic carbon. In order to determine the total metal concentrations, the total digestion (HF-HNO3-HClO4) was used, and the sequential extraction procedure (BCR-SEP) was used for the determination of chemical speciation of metals. The results showed the enormous encumberment of port by heavy metals and determined the mobility of various metals.