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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Vegetationshistoria de senaste 5000 åren kring Fållnäs gård, Södermanland : med tyngdpunkt på antropogena aktiviteter

Liljedahl, Hanna January 2009 (has links)
<p>The manor Fållnäs gård is situated at the northern end of the bay Fållnäsviken, c. 12 km north-west of Nynäshamn, Sweden. A 300 cm long sediment core collected in the bay has been analyzed regarding pollen stratigraphy. AMS <sup>14</sup>C dating of terrestrial macrofossils indicates that the sequence covers the last c. 5400 years.</p><p>The aim has been to study vegetational changes, especially human impact, in the surroundings of Fållnäs gård. Continuous findings of charcoal particles indicate that humans were present in the area at least from c. 3400 BC. Cattle breeding is indicated from c. 2200 BC by almost continues occurrences of <em>Plantago lanceolata</em>. The occurrences of pollen from cereals reveals that humans have been practicing cultivation continuously since the Neolithic/Bronze Age transition, c. 1700 BC, i.e. including a period of c. 1500 years barren of archaeological findings in the area.</p>
2

Vegetationshistoria de senaste 5000 åren kring Fållnäs gård, Södermanland : med tyngdpunkt på antropogena aktiviteter

Liljedahl, Hanna January 2009 (has links)
The manor Fållnäs gård is situated at the northern end of the bay Fållnäsviken, c. 12 km north-west of Nynäshamn, Sweden. A 300 cm long sediment core collected in the bay has been analyzed regarding pollen stratigraphy. AMS 14C dating of terrestrial macrofossils indicates that the sequence covers the last c. 5400 years. The aim has been to study vegetational changes, especially human impact, in the surroundings of Fållnäs gård. Continuous findings of charcoal particles indicate that humans were present in the area at least from c. 3400 BC. Cattle breeding is indicated from c. 2200 BC by almost continues occurrences of Plantago lanceolata. The occurrences of pollen from cereals reveals that humans have been practicing cultivation continuously since the Neolithic/Bronze Age transition, c. 1700 BC, i.e. including a period of c. 1500 years barren of archaeological findings in the area.
3

HIGH RESOLUTION GEOPHYSICAL INVESTIGATION OF LATE QUATERNARY DEFORMATION IN THE LOWER WABASH VALLEY FAULT SYSTEM

Rutledge III, Frederick Alexander 01 January 2004 (has links)
Seven and a half kilometers of high-resolution SH-wave seismic reflection profiles were collected across the Mt. Vernon graben, a 35 km by 3 km graben (bounded by the Wabash Island (WIF) and Hovey Lake faults (HLF)) in the southern Wabash Valley fault system (WVFS) of southern Indiana. Forty-six discrete faults were imaged that displaced Quaternary horizons in the vicinity of the WIF and HLF. The structural styles associated with faults include: 1) normal displacement, 2) reverse displacement and other compressional features, 3) varying magnitudes of slip along fault planes, and 4) different senses of slip along individual fault planes. Carbon 14 dating of displaced horizons suggests movement between approximately 26,000 and 42,000 YBP. The style and timing of Quaternary deformation within the WVFS, the close association of soil faults to documented post-Pennsylvanian bedrock faults (HLF and WIF), and focal mechanism studies of current seismicity in the Wabash Valley seismic zone are all direct evidence that the extensionally-formed faults of the WVFS are being transpressionally reactivated: a manner consistent with the current east-northeast westsouthwest regional compressive stress field.
4

GEOPHYSICAL AND GEOLOGICAL INVESTIGATION OF NEOTECTONIC DEFORMATION ALONG THE CABORN AND HOVEY LAKE FAULTS, WABASH VALLEY FAULT SYSTEM, CENTRAL UNITED STATES

Whitt, James 01 January 2007 (has links)
Seismic reflection (P- and SH-wave), ground-penetrating radar, correlative drilling, and age dating data provide evidence of neotectonic deformation along the Caborn (CF) and Hovey Lake (HLF) faults, in the Wabash Valley fault system (WVFS). The WVFS is a series of high-angle normal faults located primarily in southern Indiana and Illinois. Since their formation, these faults have likely been transpressionally reactivated in the contemporary E-W-oriented compressive stress state. The WVFS has experienced large prehistoric earthquakes, but only moderate historic and contemporary seismicity; therefore, the seismic potential in this region is poorly defined. The bedrock expressions of the CF and HLF were imaged with seismic reflection data (P- and SH-wave). Higher resolution analyses were performed with seismic (SHwave) and ground-penetrating radar surveys to characterize structure that may extend into the overlying Quaternary sediments. Anomalous features were cored to verify structure, and to collect datable material. The CF and HLF are interpreted to extend into the uppermost five meters of sediment and to displace horizons dated to 19,740 and 31,000 years before present, respectively. Displacement along the HLF is interpreted to extend 2-3 meters above the associated age date. These structures represent the only known primary coseismic deformation of the Late Quaternary within the WVFS.
5

Present and Past Coastal Dune Environments of South Buenos Aires Province, Argentina

Fontana, Sonia L. January 2004 (has links)
<p>The aim of this thesis is to describe present and past coastal dune environments in southern Buenos Aires Province, Argentina. </p><p>The present vegetation of a dune system and its zonation are described on the basis of air photographs, physiognomy of the dune system and floristic composition. The vegetation was characterized by a large number of Poaceae and Asteraceae species. Five vegetation zones, based on floristic composition, were defined by cluster analysis. </p><p>Pollen-vegetation comparison revealed that pollen assemblages differed considerably from the associated vegetation. Some of the major discrepancies were caused by large differences between pollen and vegetation proportion of <i>Hyalis argentea</i> and <i>Discaria americana</i>. However, the local vegetation was well represented in recent soil samples. Pollen traps recorded predominantly extralocal and regional pollen. </p><p>A new species of ostracods was recovered from an interdunal lake. The species, a giant cypridid, was described and illustrated, and its geographical distribution and ecology were discussed. </p><p>Two sediment sequences from the coastal intertidal zone and from a shallow freshwater lake were analysed for loss on ignition, calcareous microfossils (ostracods and foraminifers), macro remains and pollen. The coastal sequence was deposited between 7890 and 7630 cal. BP. Its pollen assemblages were typical for halophytic associations, with some psammophytic taxa also present in recent vegetation. The microfossils were representative of a littoral lagoon. The lake sequence comprised the last 3000 cal. BP. Pollen spectra indicated a relatively stable vegetation composition after the lake had been formed. Pollen assemblages reflected the present regional grassland vegetation with taxa characteristic for the surrounding dune communities. Human settlement was indicated in the pollen spectra by the presence of introduced taxa in the uppermost samples. </p><p>The data presented provide a useful reference for the interpretation of fossil sequences from similar environments.</p>
6

The Holocene Spread of Spruce in Scandinavia

Giesecke, Thomas January 2004 (has links)
<p>The Holocene spread of <i>Picea abies</i> in Scandinavia provides an excellent opportunity for detailed study of the dynamics of tree spread and population expansion. Early- and mid-Holocene macrofossil evidence for the presence of <i>Picea abies</i> in Scandinavia has questioned traditional interpretations of the timing and direction of its spread. This study aims to determine the pattern of the spread of <i>Picea abies</i> in Scandinavia from pollen and other data, to evaluate the significance of possible early outpost populations and to deduce possible factors that influenced the spread and population expansion of <i>Picea abies</i> in Scandinavia. </p><p>Palaeoecological investigations were carried out on the sediments of four small lakes in central Sweden to gain detailed insight into the dynamics of the spread. Holocene pollen diagrams with independent dating control were collected from Fennoscandia and adjacent areas to compare the timing of selected features of the <i>Picea abies</i> pollen curve. Computer models were used to test possible scenarios for the spread and <i>Picea abies</i> population expansion. </p><p><i>Picea abies</i> entered the Scandinavian peninsula from the east at different times and by different pathways. Early-Holocene outposts can be discerned in pollen records from northwest Russia, eastern and northeastern Finland for the time before 9000 cal. BP. Pollen records from Sweden and Norway indicate small <i>Picea abies</i> populations after 8000 cal. BP. The mid to late-Holocene spread, which superficially resembles a front-like pattern, may in fact represent a wave of expanding populations. Disturbance through fire and human activity did not significantly influence the pattern of the spread. Changing climate parameters, slow adaptation and gene flow through seeds and pollen have to be considered as possible explanations for the late spread of the tree. Population dynamics and propagule pressure are likely to be important factors that shaped the spread of <i>Picea abies</i>.</p>
7

Present and Past Coastal Dune Environments of South Buenos Aires Province, Argentina

Fontana, Sonia L. January 2004 (has links)
The aim of this thesis is to describe present and past coastal dune environments in southern Buenos Aires Province, Argentina. The present vegetation of a dune system and its zonation are described on the basis of air photographs, physiognomy of the dune system and floristic composition. The vegetation was characterized by a large number of Poaceae and Asteraceae species. Five vegetation zones, based on floristic composition, were defined by cluster analysis. Pollen-vegetation comparison revealed that pollen assemblages differed considerably from the associated vegetation. Some of the major discrepancies were caused by large differences between pollen and vegetation proportion of Hyalis argentea and Discaria americana. However, the local vegetation was well represented in recent soil samples. Pollen traps recorded predominantly extralocal and regional pollen. A new species of ostracods was recovered from an interdunal lake. The species, a giant cypridid, was described and illustrated, and its geographical distribution and ecology were discussed. Two sediment sequences from the coastal intertidal zone and from a shallow freshwater lake were analysed for loss on ignition, calcareous microfossils (ostracods and foraminifers), macro remains and pollen. The coastal sequence was deposited between 7890 and 7630 cal. BP. Its pollen assemblages were typical for halophytic associations, with some psammophytic taxa also present in recent vegetation. The microfossils were representative of a littoral lagoon. The lake sequence comprised the last 3000 cal. BP. Pollen spectra indicated a relatively stable vegetation composition after the lake had been formed. Pollen assemblages reflected the present regional grassland vegetation with taxa characteristic for the surrounding dune communities. Human settlement was indicated in the pollen spectra by the presence of introduced taxa in the uppermost samples. The data presented provide a useful reference for the interpretation of fossil sequences from similar environments.
8

The Holocene Spread of Spruce in Scandinavia

Giesecke, Thomas January 2004 (has links)
The Holocene spread of Picea abies in Scandinavia provides an excellent opportunity for detailed study of the dynamics of tree spread and population expansion. Early- and mid-Holocene macrofossil evidence for the presence of Picea abies in Scandinavia has questioned traditional interpretations of the timing and direction of its spread. This study aims to determine the pattern of the spread of Picea abies in Scandinavia from pollen and other data, to evaluate the significance of possible early outpost populations and to deduce possible factors that influenced the spread and population expansion of Picea abies in Scandinavia. Palaeoecological investigations were carried out on the sediments of four small lakes in central Sweden to gain detailed insight into the dynamics of the spread. Holocene pollen diagrams with independent dating control were collected from Fennoscandia and adjacent areas to compare the timing of selected features of the Picea abies pollen curve. Computer models were used to test possible scenarios for the spread and Picea abies population expansion. Picea abies entered the Scandinavian peninsula from the east at different times and by different pathways. Early-Holocene outposts can be discerned in pollen records from northwest Russia, eastern and northeastern Finland for the time before 9000 cal. BP. Pollen records from Sweden and Norway indicate small Picea abies populations after 8000 cal. BP. The mid to late-Holocene spread, which superficially resembles a front-like pattern, may in fact represent a wave of expanding populations. Disturbance through fire and human activity did not significantly influence the pattern of the spread. Changing climate parameters, slow adaptation and gene flow through seeds and pollen have to be considered as possible explanations for the late spread of the tree. Population dynamics and propagule pressure are likely to be important factors that shaped the spread of Picea abies.
9

Diatom distribution in the lower Save river, Mozambique : Taxonomy, salinity gradient and taphonomy

Christiansson, Marie January 2016 (has links)
In this study diatom distribution within the lower Save River, Mozambique, has been identified from surface sediments, surface water, mangrove cortex and buried sediments. Sandy units, bracketing a geographically extensive clay layer, have been dated with optical stimulated luminescence (OSL). Diatom analysis has been used to interpret the spatial salinity gradient and to discuss taphonomic processes within the delta. Previously, one study has been performed in the investigated area and it is of great importance to continue to identify diatom distributions since siliceous microfossils are widely used for paleoenvironmental research. Two diatom taxa, which were not possible to classify to species level have been identified; Cyclotella sp. and Diploneis sp. It is suggested that these represent species not earlier described; however they are assigned a brackish water affinity. Diatom analysis from surface water, surface sediments and mangrove cortex indicate a transition from ocean water to a dominance of freshwater taxa c. 10 km upstream the delta front. Further, ratios between marine/brackish taxa for samples from surface water and surface sediments do not correspond. It is therefore suggested that diatoms in surface sediments underestimate prevailing salinity conditions in water. In the investigated area extensive taphonomic processes seem to have large impact on diatom frustules in sediments and may bias interpretations. Therefore it is recommended to carefully investigate geology, geomorphology and vegetation before diatom analysis is applied in studies of delta paleoenvironments.
10

An Evaluation of Late Holocene Sea Level Rise and Anthropogenic Impacts; Jones Narrows Marsh, Chatham County, Georgia

Hughes, Jessie 14 December 2016 (has links)
A detailed record of the Late Holocene sea level rise and landscape evolution that has taken place on the Georgia coast is contained within the sedimentary stratigraphy of its salt marsh depositional basins. Global relative sea level (RSL) has risen during the Late Holocene, and the rate of rise has accelerated during the Anthropocene. Jones Narrows marsh stratigraphy and radiocarbon analysis indicate increasing rates of RSL rise for the late Holocene on the Northern Atlantic Coast of Georgia, while FPXRF analysis of the marsh sediments facilitates a chemostratigraphic study of Jones Narrows salt marsh deposition and landscape evolution. Sedimentation and hydrology at the site have been heavily influenced by recent local anthropogenic impacts, which are examined through stratigraphic and spatial methods.

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