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2012 (9)

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Dissertation
Late Holocene vegetation dynamics in a mountainous environment in the territory of Sagalassos, Southwest Turkey (Late Roman till present).
Authors: --- --- --- ---
ISBN: 9789086495351 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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Abstract

Anatolia is characterized by a very complex history of climate and human related vegetation change, which varies strongly from location to location. The region forms a bridge between Europe, Asia, and Africa for plants as well as human civilisation. The regional climate is equally influenced by North Atlantic, Asian, and African climatic forces and may vary regionally due to the rough topography of Anatolia. While palynological data are available for the Eastern Mediterranean, well dated records focussing on the period from the end of the Roman Imperial period to the present are rare for Anatolia and absent for SW Turkey. Additionally, while climatic data are available for the Eastern Mediterranean, no climatic records exist for SW Turkey. The aforementioned complexity of the climatic system makes it impossible to reliably use existing climatic proxies for locations for which such data are not yet available.The Sagalassos Archaeological Research Project has been involved in excavating the classical city of Sagalassos, in the Western Taurus Mountains, Turkey. Since 1993, the archaeological project has had an interdisciplinary character, not only focussing on classical archaeology, but also involving palaeo-environmental research in an effort to understand the history of not only the city itself, but also its surrounding rural landscape.In recent times, archaeological research has been focussed at the Late Roman and Early Byzantine periods, while in the next years, the focus will shift towards the interval from the Early Byzantine period to the present. The present research has been performed as part of the Sagalassos Archaeological Research Project, and the research results may contribute to a better understanding of vegetation dynamic and human impact within the territory, while the archaeological data may help explain the nature of the environmental changes observed in the data. Additionally, the climatological aspect of the research, as well as the fact that no detailed palaeoecological records exist which cover the most recent 2000 years in detail in SW turkey, give the research results a regional significance, providing an important new insight in the complex patterns of vegetation and climate change in the Middle East.Two well dated palaeoecological records from the territory of Sagalassos provide a first relatively detailed record of vegetation dynamics in Southwest Turkey focussing on the period from late Roman times until the present. Combining pollen, non-pollen palynomorphs and charcoal data with multivariate statistics, sedimentological and archaeological data, allows for the disentangling of climatic and anthropogenic influences on vegetation change in this under-researched region of the Eastern Mediterranean.The palynological and sedimentological data revealed several periods of human occupation in the pollen record, previously unknown for SW Turkey. Signs of intensive crop cultivation in the two records started to decline after the mid 3rd century AD, completely disappearing from one basin. A further, more complete shift from crop cultivation to livestock herding, possibly (semi)pastoralism, occurred in the mid 7th century. Resurgence in human impact, in the form of deforestation, livestock herding, and limited crop cultivation occurred from the mid 10th to the mid 12th century AD, after which human impact declined abruptly and completely, allowing for the establishment of a pine forest at both sites. This pine forest persisted until the mid 16th century, after which there was a gradual deforestation of the area, in combination with signs of grazing, perhaps linked to livestock herding. A pollen spectrum representative of the modern day agricultural practices in the study area only occurred in the topmost part of the available pollen record.The numerical analyses revealed a succession of relatively wet and relatively dry bioclimatic trends occurring throughout the study area and surrounding territory, and corresponding with well-defined European climate shifts, allowing the assessment of the exact timing and impact for the first time in this region of Anatolia. The data show a shift towards increased moisture availability occurs during the 3rd century and from the mid 10th to the early 14th century AD. Relatively dry conditions prevailed prior to the mid 3rd century AD, from the mid 7th to the mid 10th century AD, and from the early 13th century AD onwards. A shift towards moister environmental conditions in the 18th century may be an artefact caused by the deforestation of the study area at that time.The available sediment records from the study area, as well as an external tree ring record, implied that a more realistic estimate for the end of the second wet phase was the mid 13th century AD. Additionally the tree ring record indicated that both the bioclimatic proxy and calcium carbonate record from one of the locations were accurate records of regional climatic change and that the estimated chronology for this location was also highly accurate.Statistical analyses performed on the charcoal record from both records revealed that fire activity in the rural landscape from the Early Byzantine period onwards was limited. Only a few fires were recorded and these were mostly reasonably small, no fires were recorded simultaneously at both sample sites. Only a small amount of the recorded fires appeared to be connected to human activity. Most others were primarily connected to fuel availability, and their occurrence was not related to specific environmental conditions.Research into the pollen production and dispersal of some important plant taxa in the study area revealed that for many of the plant taxa included in the analyses, the relevant source area of pollen is relatively small, likely due to the rough topography of the study area. As a consequence, when researching regional changes in climate and vegetation through time, it is vital to study multiple records from the same study area in order to distinguish between local and regional environmental phenomena. When studying more local phenomena, such as human impact in the vicinityof a sample site of a pollen record, it is vital to keep in mind that the pollen signal may only represent the vegetation within a relatively short distance around the sample site. Changes in human activity, especially when they occur simultaneously in multiple records, may still be representative of larger scale changes in human impact in the research area, especially when coinciding with marked changes observed in the climatological or archaeological record, but they must not be seen as representative of how human impact changed throughout the territory.Comparing the research results with the historical and archaeological record of Sagalassos and historical, archaeological, and palaeoecological data from the wider region of Anatolia revealed how human impact and climate drove environmental change, both together as well as individually.The decrease in intensive crop cultivation at both sample sites differed from the regional trend of increased anthropogenic activity during this relatively moist period, and is also at odds with the archaeological record of Sagalassos, which indicates the city and territory remained relatively prosperous during this period. The decrease in human impact may be a local phenomenon and a result of the local wetlands increasing in size, encroaching onto formerly arable land. However, the possible role of political, economical and military instability throughout the wider region may not be ignored. The further shift to animal grazing/herding coincided with a climatic deterioration during the mid 7th century, as well as the start of Arab incursions into Anatolia. During the 8th/9th centuries AD, the Byzantine Empire underwent a political, economical and military revival, but at Sagalassos, as well as at other locations, a true increase in human impact only occurred during the mid 10th century, coinciding with the start of the Medieval Climate Anomaly (MCA) in the Eastern Mediterranean. It is proposed that, while the local population had the financial means to expand their agricultural practices; it was the start of the MCA which made the rural basins in the territory of Sagalassos suitable for agriculture. The disappearance of agriculture during the 12th century does not appear to be connected to environmental change, and may be driven by the political instability of that period and changes in land ownership at the cost of small-scale independent farmers. Gradual deforestation occurring from the 16th century onwards has been linked to changes in landscape use during the ottoman reign, rather than climatic change.


Dissertation
The impact of the Paleocene-Eocene thermal maximum on benthic foraminiferal shelf communities : paleoenvironmental reconstructions and stratigraphic correlations.
Authors: --- --- ---
ISBN: 9789086495290 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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Paleoclimate research is currently a hot topic in the international debate on how greenhouse-gas emissions affect climate change. Now that the idea of unavoidable global warming by the end of this century is commonly accepted, interest in the early Paleogene climate changes is increasing. During this period, Earth’s climate experienced episodes of rapid global warming and massive injections of carbon dioxide are linked to these transient temperature anomalies. The Paleocene-Eocene thermal maximum (PETM) at the Paleocene-Eocene (P-E ~55.8 Ma) boundary is the most extreme climate event as it represents a rapid worldwide 5-8 &#176;C warming of Earth’s surface as well as the deep oceans, associated with large changes in ocean chemistry (ocean acidification). In addition, the PETM is recognized as a critical evolutionary turning point in, which the biosphere was reorganized on a global scale. Unique faunal and floral extinction, radiation and migration patterns are recognized in both terrestrial and marine ecosystems, including a major extinction in deep-sea foraminiferal faunas.In order to establish clear biogeographic patterns of how shallow marine ecosystems responded to the climate changes during the PETM, I studied the benthic foraminiferal distributions in neritic (<200 m water depth) settings in the Northern Hemisphere. During my PhD, I explored the Tunisian Basins and the North Atlantic Coastal Plain in the United States, and compared them to the well-studied Egyptian Basin. I discussed the various aspects of the environmental parameters controlling the benthic foraminiferal distributions and correlated the P-E boundary within the studied basins. The overall result is a synthesis of the short-term biotic response to the PETM.In general, stable latest Paleocene benthic foraminiferal assemblages were in all studied location abruptly replaced by more stress-tolerant faunas during the early stages of the PETM. Our observations indicate that the PETM exerted worldwide environmental stress on benthic foraminiferal communities, triggering prominent transient changes in population structures and biodiversity. Yet the evolutionary impact was minor compared to the deep-sea extinction event. This implies the existence of refugia on the shelves.The increase in abundance of stress-tolerant faunas reflects more stressed dysoxic to anoxic eutrophic marine environments, due to higher nutrient delivery and stratification of the water column. These hypoxic conditions occurred in the early stages of the PETM continually or with high frequencies and evolved towards periodic (seasonal?) oxygen depletion during the later stages of peak warming or initial recovery. The final recovery phase reflects a reoxygenation of the sea floor. These eutrophic conditions remained stable and continued in the aftermath of the PETM and the bottom waters became permanently reoxygenated.Although paleogeographic and climate conditions were different than those of today, the PETM offers insights of how modern regional shelf ecosystems may respond to the massive anthropogenic input of carbon dioxide. This study reveals that benthic foraminifera living on the shelf are not immune to the environmental degradation during global warming and benthic ecosystems will undergo significant transient changes in species composition as global peak warming takes place.


Dissertation
Evolution of the South-Rayan dune-field (Central Egypt) and its interaction with the Nile fluvial system.
Authors: --- ---
ISBN: 9789086495528 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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This thesis aims at studying the recent dune dynamics and the interaction between the aeolian and fluvial processes at different temporal and spatial scales. The South-Rayan Dune-Field (SRDF) in Central Egypt was selected as the main study area for this research because it provides a typical example for analyzing dune dynamics and aeolian-fluvial interaction. At a first step a multi-temporal analysis of Landsat-TM5 images was performed to detect the migration of desert dunes in the SRDF over the time period 1984-2003. The near-infrared (NIR) spectral bands of the old and new Landsat-TM5 images were combined in a bi-temporal layerstack (BTLS), from which the dune migration and the overall sand drift over the entire dune-field can be detected. The BTLS was then used as an input to RGB-clustering (RGBC), which was performed to convert the color display of the BTLS into a map of dune activity between 1984 and 2003. In order to check the applicability and limitations of the technique it was also tested in other four dune systems around the globe. The technique proposed here was very successful in providing an initial insight into the dune dynamics in the dune-field


Dissertation
Assimilating remotely sensed cloud parameter for improved regional air quality simulations.
Authors: --- --- ---
ISBN: 9789086495511 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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Clouds have a significant effect on air quality, among others by affecti ng photolysis (through their effect on shortwave radiation), and because of their role in chemical reactions that occur at the interface of clou d droplets. Yet, atmospheric models experience great difficulty in simul ating cloud-related variables correctly, which regularly leads to poorly simulated concentrations of atmospheric pollutants such as tropospheric ozone and fine particulate matter. Considering this, the main goal of t he proposed research is to improve the simulation of cloud in atmospheri c models by exploiting satellite data in a data assimilation procedure, and to demonstrate the impact of an improved representation of cloud on simulated air quality at the regional scale. The methodology will be as follows. In a first step, relevant satellite data will be evaluated and selected. Criteria for selection will be based, among others, on the type of geophysic al parameter the instrument can provide (e.g., cloud top temperature, op tical depth, ...), as well as other observation characteristics (e.g., s patial and temporal resolution). Next, the selected data will be process ed to yield the required information (e.g., vertical profiles of cloud l iquid/ice water). Resulting profiles will be compared with data from an independent source, e.g. from recently launched satellite instruments de veloped for experimental cloud studies. Retrieved cloud parameter profil es will then be inserted into the mesoscale meteorological model Advance d Regional Prediction System (ARPS) using data assimilation techniques. Subsequently, the impact of assimilating cloud data into ARPS will be ev aluated, by confronting simulated values of relevant quantities (e.g., s urface shortwave radiation, cloud liquid water content) with observed va lues. Following the succesful validation of ARPS, the urban/regional air quality model AURORA will be enhanced to fully benefit from the im proved cloud simulations. This will be achieved by improving parameteris ations that calculate photolysis coefficients. Finally, the accuracy of regional air quality simulated with the improved AURORA model will be ev aluated, focusing on ground-level pollutant concentrations of ozone.&nbs p; It is expected that a successfull a chievement of the objectives will lead to significantly improved air qua lity simulations with the AURORA model, especially for ozone.

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Dissertation
Levels, fractionation and mobility of potentially toxic elements in sediments of Quang Ninh- Hai Phong coastal region, Vietnam.
Authors: --- --- --- ---
ISBN: 9789086495337 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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In this project, three estuarine and river-mouth areas, namely Cua Ong Estuary, Cua Luc Estuary and Cam River-mouth that belong to the Quang Ninh- Hai Phong coastal region (Vietnam) were investigated for the status as well as history and origin of the heavy metal and arsenic contamination of sediments. In addition, the speciation and mobility of heavy metals and arsenic under changing environmental conditions (Eh and pH) in vertical profiles or upon simulated on-land disposal of dredged sediments in the Cam River-mouth area (Hai Phong Province) were also investigated. The project included many different works including the collection of surficial bed-sediment and core-sediment samples, the performance of ripening experiments, porewater collection, single (ammonium-EDTA) and sequential (BCR 3-step) extractions, and pHstat-leaching tests as well as analyses of chemical composition of major and trace elements (Al, Ca, Fe, K, Mg, Na, S, P, As, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn), anions (F-, Cl-, Br-, NO2-, NO3-, SO42- and PO43-, etc….), grain-size, mineralogy, organic matter content (OM), cation exchange capacity (CEC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and 137Cs isotope dating.In Cua Ong and Cua Luc estuaries, heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn) and As mainly display a natural origin (from the weathering and erosion processes of rocks). In contrast, in the Cam River-mouth, heavy metals and arsenic are considered to be minorly to moderately enriched as a result of anthropogenic activities in Hai Phong City and Northern Vietnam. Especially, Cu, Mn, Pb and Zn in sediments increased rapidly by a factor of approximately 2 from 1954 to 1975 and then remained nearly unchanged from 1975 to 2008.In the Cam River-mouth, heavy metals (Cu, Mn, Pb and Zn) and As show overall decreasing trends of concentrations in porewater or sediment from top to bottom of a sediment core. Moreover, non-silicate fractions of these elements (exchangeable and carbonate-bound, Fe and Mn hydr/oxide-bound, and organic matter and sulphide-bound) also decrease from top to bottom as a result of their anthropogenic origin in surficial sediment layers and decreasing Eh and increasing pH values with depth. The pHstat-leaching tests on the original suboxic and oxidized sediments indicate that the pH-dependent leaching behavior of Cu, Mn, Pb, Zn and As reflects a V-shaped pattern in which they are strongly leached at highly-acid pH (2) or highly-alkaline pH (11), and minimum leachabilities are obtained in the slightly acid to slightly alkaline pH-range (6 – 8). Under the effect of oxidation, for Mn, Pb and Zn a transfer from the exchangeable and carbonate-bound fraction to the Fe and Mn hydr/oxide-bound fraction, and for Cu a transfer from the organic matter and sulphide-bound fraction to the Fe and Mn hydr/oxide-bound fraction occurred. In accordance with these results, Mn, Pb, Zn and As are characterized by a slower and lower release in the pH range 2 – 11 while for Cu, the pattern is opposite at pHs 2 – 8. A ripening experiment that simulates the on-land disposal of dredged sediments suggests that the porewater concentrations of heavy metals and arsenic increase immediately after exposure to the atmosphere, but then decrease to levels below their initial concentrations in the porewater. This implies a short-term risk for groundwater pollution by leaching of heavy metals and arsenic in the beginning of the on-land disposal, however, the risk will be mitigated with time when the oxidation further proceeds.


Dissertation
Metallogenesis of Sn and W vein-type deposits in the Karagwe-Ankole belt (Rwanda).
Authors: --- --- --- ---
ISSN: 02507803 ISBN: 9789086495658 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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Although not well known by most people, tin (Sn) and tungsten (W) are two metals that are important in our society. Tin is for instance used for the production of corrosion-resistant steel, as a solder and for the production of bronze, while tungsten is used in cutting tools, heavy metal alloys, light bulbs and dental drills. Tin and tungsten deposits can be found worldwide. Tin and tungsten are often closely associated to one another and can even occur in the same deposit. The Mesoproterozoic Karagwe-Ankole belt (KAB) in Central Africa hosts numerous Sn and W deposits. These mineralisations principally occur in pegmatites and hydrothermal quartz veins that are presumably related to granite intrusions. This PhD study focuses on the Sn and W vein-type mineralisations in the central part of the KAB, in Rwanda. This study aims to determine the origin and evolution of the Sn and W vein-type deposits, focussing on the evolution of the mineralising fluids and their composition (geochemistry). The mineralising fluids are studied by means of a detailed petrographical, geochemical and microthermometrical study and by using specialised geochemical techniques (LA-ICP-MS, crush-leach, Raman analysis and stable isotope geochemistry). The absolute age of the ore deposits is determined by means of the 40Ar-39Ar dating technique. The metasedimentary rocks of the KAB in Central Africa have been affected at ~1375 Ma by a major intracratonic bimodal magmatic event (Tack et al., 2010).


Dissertation
De regulatie van de West-Afrikanse stadstuinbouw : diversiteit in de kleinschalige groente- en fruitteelt in Ouagadougou en Katar.
Authors: --- --- --- --- --- et al.
ISBN: 9789086495160 Year: 2012 Publisher: Leuven KU Leuven. Faculteit Wetenschappen

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Dissertation
Episodic circulation of reactive fluids along faults : from travertine- to basin-scale study on the Colorado Plateau natural example (USA).

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Understanding the mechanisms of porosity/permeabilityevolution during fluid circulation episodes in a fault zone is a current challenge. This multidisciplinary study of CO2 natural leakage in the ColoradoPlateau area reveals a localization and several episodes of CO2 fluidscirculation operating along faults .By means of field to thin sectionscale studies, coupling structural geology, petrography, stable isotopes andU/Th geochemistry, we investigated i) the field evidences of CO2-leakage fromdeep horizons toward the surface, ii) the alternating circulation and sealingprocesses, iii) the spatial evolution of the CO2 leakages and of thecomposition of the fluids, and finally iv) the overall fluid circulationhistory by dating the diagenetic cements and travertines.Fieldwork across a fractured zone alllowedto reconstruct the architecture of the CO2 path from the depth to the surface.The CO2 leaking zone migrated spatially and temporally along the faults: tracesof fossil and modern leakages are obvious at fault relay zones with amineralization concentration reaching an average thickness up to 15 meters atground level, mainly expressed by calcium carbonate veins and surfacetravertine. Dedicated petrographic and geochemical studies of this zone revealedsuccessive episodes of dissolution and precipitation. The precipitation couldtake place after the opening of dissolution cavities or the two dissolution andprecipitation processes could operate at the same time, depending on both thefluid flow and the pore fluid pressure. The joint study of stable isotopes andU/Th dating of representative samples ranging from late Pleistocene untilpresent day and collected at a same leaking place allows also to calibrate theCO2 leakage time-laps, rates, cycles and volumes and to discuss this archivemeaning. Based on these results, we propose a conceptual andnumerical modeling of CO2-leakage through a faulted zone which links episodicvariations of CO2-circulation to successive stages of fault opening andsealing: CO2-input corresponding to the opening of the fault is followed by anexponential decrease rate of the CO2 flowrelated to the post-seismic fault sealing by the mineralization of calciumcarbonate

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Dissertation
Sediment yield from european catchments : exogenic, endogenic and anthropogenic controls.

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