<p>Detailed information on past oceanographic and climatic changes is crucial for our understanding of natural climate variability and for the assessment of future climate variations. Sediments strongly influenced by the North Atlantic Current accumulate at high rates in the northeastern Skagerrak, forming a potential highresolution archive for information on past climatic and oceanographic processes and events. Through a highresolution, multi-proxy study of the 32 meter long core MD99-2286 from the north-eastern Skagerrak, and interpretation of chirp sonar profiles from the coring area, this thesis provides new and detailed insights about the paleoceanographic development of the eastern North Sea region since the deglaciation.</p><p>The chronostratigraphic control of core MD99-2286 relies on 27 radiocarbon dates. Ages are presented in calibrated thousand years before present (abbreviated “kyr”). Core MD99-2286 was correlated to chirp sonar profiles using measured physical properties. This correlation demonstrates that a strong regional acoustic reflector, previously assumed to represent the Pleistocene/Holocene boundary, was formed as a result of rapid ice retreat during the latest Pleistocene. Based on the distribution of ice rafted debris in the core, ice berg calving in the Skagerrak ended at 10.7 kyr. Detailed grain-size analyses of the core were interpreted using a novel 3D-visualization technique. Between 11.3 and 10.3 kyr, clay-rich distal glacial marine sediments were deposited in the northeastern Skagerrak, derived from Baltic melt-water outflow across south-central Sweden through the Otteid-Stenselva strait. As a result of differential isostatic uplift, the route of the major outflow and the associated sediment deposition moved southwards along the Swedish west coast. After 10.3 kyr, sediment deposition in the north-eastern Skagerrak gradually adopted to a fully interglacial normal marine sedimentation dominated by Atlantic inflow and the North Jutland Current.</p><p>The establishment of the modern circulation system in the eastern North Sea is marked by abrupt coarsening of the sediments in core MD99-2286 at 8.5 kyr. This was a result of increased Atlantic inflow, opening of the English Channel and the Danish straits, and formation of the South Jutland Current. Mineral magnetic properties of the core show a distinct relationship reflecting general sediment source variability. After 8.5 kyr, sediments in the northeastern Skagerrak were derived predominantly from the Atlantic Ocean and the North Sea, with varying contributions from the South Jutland Current, the Baltic Current, and the currents along the coasts of western Sweden and southern Norway. Between 6.3 and 3.8 kyr, the eastern North Sea was further developed towards the modern situation by an increase of the South Jutland Current flow. The Skagerrak bottom currents were probably forced by strong Atlantic water inflow between 0.9 and 0.5 kyr, and after that by increased wind stress. The influence of regional climate on the eastern North Sea circulation has increased since the middle of the Holocene.</p>

<p>This thesis focuses on responses in raised bogs to changes in the effective humidity during the Holocene. Raised bogs are terrestrial deposits that can provide contiguous records of past climate changes. Information on and knowledge about past changes in climate is crucial for our understanding of natural climate variability. Analyses on different spatial and temporal scales have been conducted on a number of raised bogs in south-central Sweden in order to gain more knowledge about Holocene climate variability.</p><p>Peatlands are useful as palaeoenvironmental archives because they develop over the course of millennia and provide a multi-faceted contiguous outlook on the past. Peat humification, a proxy for bog surface wetness, has been used to reconstruct palaeoclimate. In addition measurements of carbon and nitrogen on sub-recent peat from two bogs have been performed. The chronologies have been constrained by AMS radiocarbon dates and tephrochronology and by SCPs for the sub-recent peat.</p><p>A comparison between a peat humification record from Värmland, south-central Sweden, and a dendrochronological record from Jämtland, north-central Sweden, indicates several synchronous changes between drier and wetter climate. This implies that changes in hydrology operate on a regional scale.</p><p>In a high resolution study of two bogs in Uppland, south-central Sweden, C, N and peat humification have been compared to bog water tables inferred from testate amoebae and with meteorological data covering the last 150 years. The results indicate that peat can be subjected to secondary decomposition, resulting in an apparent lead in peat humification and C/N compared to biological proxies and meteorological data.</p><p>Several periods of wetter conditions are indicated from the analysis of five peat sequences from three bogs in Värmland. Wetter conditions around especially c. 4500, 3500, 2800 and 1700-1000 cal yr BP can be correlated to several other climate records across the North Atlantic region and Scandinavia, indicating wetter and/or cooler climatic conditions at these times. Frequency analyses of two bogs indicate periodicities between 200 and 400 years that may be caused by cycles in solar activity.</p>

<p>This thesis presents palaeoenvironmental data from equatorial Africa covering two important time intervals; i) the warming period forming the Pleistocene/Holocene transition and ii) the last millennium. The Empakaai Crater, in northern Tanzania contains a lake from where sediment cores, spanning two time-slices 14.8-9.3 ka and 800-2000 AD, have been studied. Palaeoecological and palaeohydrological reconstruction is based on a multitude of proxies from the sediments, representing both catchment environment and the lakes aquatic ecosystem response. Between 14.8 and 10 ka the catchment vegetation and lake hydrology responded to both regional climate changes and local environment, but with different amplitude and frequency, reflecting temporal and spatial lags between the two systems. However, at c 10 ka both lake conditions and catchment vegetation showed drastic changes towards drier conditions. The record covering the last millennium reveals environmental changes related to climate and human activities. The catchment’s vegetation was affected by frequent fires, most probably human induced, while near shore vegetation responded to lake level fluctuation associated with rainfall variability. About 15 km from Empakaai Crater is an extensive abandoned irrigation system, the Engaruka complex, which was in active use between c 1400 AD and 1840 AD. By comparing a number of social and environmental factors potentially influencing the societal development at Engaruka it is shown that wet climate conditions have had positive effects on the societal development but also that dry climate conditions were not always disastrous to the society. The resemblance of the pollen taxa present is strong between the two time slices and pollen representing catchment conditions respond in similar manner in both records. The lake conditions are however very different between the two periods Thus the lake responds to both long and short term changes of variable amplitude, while the catchment vegetation seems to responds to high amplitude, low frequency changes.</p>

<p>Lake sediments are frequently used as archives of climate and environmental change. Minerogenic sediment variability in alpine lakes is often used to reconstruct past glacier and slope process activity. Alpine lake sediments can however have many different origins, which may induce errors in paleoenvironmental reconstructions. The aim of this project was to enhance the understanding of minerogenic lake sedimentation in alpine lakes and improve their use as environmental archives.</p><p>Catchment geomorphology and Holocene sediment sequences were analysed for five alpine lakes. Several minerogenic sediment sources were detected in catchments and sediment sequences. Slope-, fluvial-, periglacial-, nival- and aeolian sediment transportation processes contribute to create complex lake sediment patterns. Large variations in sedimentation rates were discovered within and between lakes, which has implications for sampling strategies and age-model constructions. Similar fine-grained minerogenic laminations were found in four of the investigated lakes, despite large differences in setting. The demonstrated similarity between glacial and non-glacial lakes may complicate interpretations of glaciolacustrine sediment signals.</p><p>The main conclusion is that lake sedimentation in alpine environments is highly dependent on several geomorphological factors. All lakes should therefore be viewed as unique and the geomorphology should be thoroughly investigated before environmental reconstructions are based on lake sediment proxies. This study has confirmed the multi-source origin of alpine lake sediment, which also opens possibilities of more multi-faceted paleoenvironmental studies. Different process-proxies could potentially be used to separate different climate signals, e.g. precipitation, temperature and wind, in lake sediments. Analysis of grain-size distribution, detailed mineralogy and magnetic mineralogy in combination with X-ray radiography are suggested methods for such reconstructions.</p>

<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>

Tsunamis are low amplitude, large wavelength waves that can significantly impact coastal regions. Although their destructive impacts are clear from recent events, the frequency with which tsunamis occur is less well constrained. To better understand the tsunami history and coastal impacts in Sri Lanka, this study compares sediments deposited by the December 26, 2004, tsunami to older lagoon sediments in search of evidence for paleotsunami deposits. Results from this study illustrate that the coastal lagoons in Sri Lanka preserve tsunami deposits and can provide the first steps towards constraining the paleotsunami history of the Indian Ocean. Because Sri Lanka is a far field location relative to the Sumatra-Andaman subduction zone, the preserved tsunami deposits are likely mega-tsunami events similar in size and destruction to the December 26, 2004, tsunami. The December 26, 2004, M 9.1?9.3 Sumatra-Andaman earthquake generated a massive tsunami that propagated throughout the Indian Ocean, causing extreme coastal inundation and destruction. The southeastern coastline of Sri Lanka was impacted by the 2004 tsunami where between one and three waves inundated coastal villages, lagoons, and lowlands, killing more than 35,000 people. Karagan Lagoon, located on the southeastern coast of Sri Lanka, was impacted by two waves from this tsunami. Although the lagoon commonly is dominated by organic-rich, siliciclastic clays, silts, and fine sands, the 2004 tsunami deposited a distinct layer of coarse quartz-dominated sand between 1 and 22 cm thick. The base of the 2004 deposit is sharp and erosional and some layers feature faint subparallel laminations. The 2004 tsunami deposit is generally continuous, fines landward, and is confined to the eastern portion of Karagan Lagoon, in the direction from which the tsunami arrived. Sri Lankan lore, in conjunction with reconstructed historical earthquake data, suggests that other tsunamis likely affected Sri Lanka in the past. To test this, twenty-two 1?4 m sediment cores were collected from Karagan Lagoon, providing key information for unraveling the pre-2004 tsunami history of southeastern Sri Lanka. At depth, sixteen cores from Karagan Lagoon contain as many as ten distinct sand layers, including the deposit from the 2004 tsunami. These cores feature siliciclastic clays, silts, and fine sands that dominate the background lagoonal sedimentation that are punctuated by coarse sand layers. These sand-rich layers feature sharp, erosional bases, coarsen and fine upwards, vary in thickness from 1 to 22 cm, and include varying percentages of fine to very coarse sand, with a low-abundance of silt and clay. In the best constrained interval, three coarse sand layers include composition, grain size, grading, and sedimentary structures similar to the sediments deposited by the December 26, 2004, tsunami. The layers are identified in five of the twenty-two cores, although the thicknesses vary. Six additional less well constrained sand layers are present in four of the twenty-two cores. Cores located closer to the lagoon mouth and the eastern coastline (the direction from which the 2004 tsunami arrived) contain more sand layers than cores farther away from the tsunami wave entry point. On the basis of their sedimentary structures, geometry, and extent, these sandy layers are interpreted to represent paleotsunami deposits. AMS radiocarbon dating was used to date the bulk organic sediment from above, between, and below the ten paleotsunami layers in sediment cores from Karagan Lagoon to constrain the timing of events in southeastern Sri Lanka. Material from within the deposit was not dated because it was likely transported from various sources during the event and thus does not represent the age of the tsunami. AMS radiocarbon dates from above and below the paleotsunami layers were calibrated from radiocarbon years before present to calendar years before present (Cal YBP) using OxCal v. 4.0 (Bronk Ramsey, 1995; Bronk Ramsey, 2001) with calibration curve IntCal04 (Reimer et al., 2004). The constraining time intervals of tsunami deposits II?VI were averaged to yield deposits of ages 226, 1641, 4198, 4457, 4924 Cal YBP. Tsunamis VII?X only had sediment dated immediately below the deposit and therefore were deposited prior to 6249, 6455, 6665, and 6840 Cal YBP. In total, ten tsunami deposits, including the 2004 event, are preserved in Karagan Lagoon on the southeastern coast of Sri Lanka. The Karagan Lagoon paleotsunami deposits provide constraints on the recurrence interval of tsunamis similar in magnitude to the 2004 event. The uppermost paleotsunami units were deposited 226, 1641, 4198, 4457, and 4924 Cal YBP, based on AMS radiocarbon dating. Thus, including the 2004 event, six tsunamis affected Karagan Lagoon in the past 5500 years, yielding a recurrence interval of approximately 916 years. Three of the six events, however, occur between ~4000 and 5500 years yielding a recurrence interval of approximately 500 years for this 1500 year period. Four additional older paleotsunami deposits occur in the deeper sections of the cores and were deposited prior to 6249, 6455, 6665, and 6840 Cal YBP, yielding a recurrence interval of approximately 200 years for this time period. Assuming that Karagan Lagoon contains a complete record of tsunami events, the recurrence of tsunamis similar in magnitude to the December 26, 2004, event can occur as often as 200 years. This ?recurrence interval? is illustrated by our data for the time period with increased tsunami activity from ~4000 to 7000 Cal YBP. Tsunamis may potentially affect Sri Lanka at relatively high frequency during certain time intervals though the overall recurrence pattern of these events displays a highly irregular distribution. This extreme variability needs to be taken into consideration when such events are related to earthquake recurrence intervals. Prior to the December 26, 2004, tsunami, paleotsunami deposits in the Indian Ocean were largely unstudied and consequently, Holocene tsunami chronology was incompletely understood for the Indian Ocean. The results from this study represents the first geologic evidence of paleotsunami deposits in Sri Lanka generated by tsunamis during the past 7000 years. The identification of these paleotsunami deposits illustrates that the 2004 tsunami was not a ?one-time event,? but in fact has ancient counterparts.

Thesis (Ph.D.)--Southern Methodist University, 2004. / Advisers: Fred Wendorf, Lewis Binford. Includes bibliographical references.

Sediment records of three European lakes were investigated in order to reconstruct the regional climate development during the Lateglacial and Holocene, to investigate the response of local ecosystems to climatic fluctuations and human impact and to relate regional peculiarities of past climate development to climatic changes on a larger spatial scale. The Lake Hańcza (NE Poland) sediment record was studied with a focus on reconstructing the early Holocene climate development and identifying possible differences to Western Europe. Following the initial Holocene climatic improvement, a further climatic improvement occurred between 10 000 and 9000 cal. a BP. Apparently, relatively cold and dry climate conditions persisted in NE Poland during the first ca. 1500 years of the Holocene, most likely due to a specific regional atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the remaining Scandinavian Ice Sheet (SIS) might have blocked the eastward propagation of warm and moist Westerlies and thus attenuated the early Holocene climatic amelioration in this region until the final decay of the SIS, a pattern different from climate development in Western Europe. The Lateglacial sediment record of Lake Mondsee (Upper Austria) was investigated in order to study the regional climate development and the environmental response to rapid climatic fluctuations. While the temperature rise and environmental response at the onset of the Holocene took place quasi-synchronously, major leads and lags in proxy responses characterize the onset of the Lateglacial Interstadial. In particular, the spread of coniferous woodlands and the reduction of detrital flux lagged the initial Lateglacial warming by ca. 500–750 years. Major cooling at the onset of the Younger Dryas took place synchronously with a change in vegetation, while the increase of detrital matter flux was delayed by about 150–300 years. Complex proxy responses are also detected for short-term Lateglacial climatic fluctuations. In summary, periods of abrupt climatic changes are characterized by complex and temporally variable proxy responses, mainly controlled by ecosystem inertia and the environmental preconditions. A second study on the Lake Mondsee sediment record focused on two small-scale climate deteriorations around 8200 and 9100 cal. a BP, which have been triggered by freshwater discharges to the North Atlantic, causing a shutdown of the Atlantic meridional overturning circulation (MOC). Combining microscopic varve counting and AMS 14C dating yielded a precise duration estimate (ca. 150 years) and absolute dating of the 8.2 ka cold event, both being in good agreement with results from other palaeoclimate records. Moreover, a sudden temperature overshoot after the 8.2 ka cold event was identified, also seen in other proxy records around the North Atlantic. This was most likely caused by enhanced resumption of the MOC, which also initiated substantial shifts of oceanic and atmospheric front systems. Although there is also evidence from other proxy records for pronounced recovery of the MOC and atmospheric circulation changes after the 9.1 ka cold event, no temperature overshoot is seen in the Lake Mondsee record, indicating the complex behaviour of the global climate system. The Holocene sediment record of Lake Iseo (northern Italy) was studied to shed light on regional earthquake activity and the influence of climate variability and anthropogenic impact on catchment erosion and detrital flux into the lake. Frequent small-scale detrital layers within the sediments reflect allochthonous sediment supply by extreme surface runoff events. During the early to mid-Holocene, increased detrital flux coincides with periods of cold and wet climate conditions, thus apparently being mainly controlled by climate variability. In contrast, intervals of high detrital flux during the late Holocene partly also correlate with phases of increased human impact, reflecting the complex influences on catchment erosion processes. Five large-scale event layers within the sediments, which are composed of mass-wasting deposits and turbidites, are supposed to have been triggered by strong local earthquakes. While the uppermost of these event layers is assigned to a documented adjacent earthquake in AD 1222, the four other layers are supposed to be related to previously undocumented prehistorical earthquakes. / Sedimente aus drei europäischen Seen wurden untersucht um die regionale Klimaentwicklung während des Spätglazials und Holozäns und die Reaktion der Ökosysteme auf Klimaschwankungen und menschlichen Einfluss zu rekonstruieren sowie die regionalen Besonderheiten der spätquartären Klimaveränderungen in einen überregionalen Kontext zu setzen. Die Sedimente des Jezioro Hańcza (Nordostpolen) wurden im Hinblick auf die frühholozäne Klimaentwicklung und die Identifikation möglicher Unterschiede gegenüber Westeuropa untersucht. Im Anschluss an die Erwärmung zu Beginn des Holozäns konnte eine weitere Verbesserung der Klimabedingungen zwischen 10 000 und 9000 Jahren vor heute nachgewiesen werden. Offensichtlich herrschten in Nordostpolen während der ersten 1500 Jahre des Holozäns noch relative kalte und trockene Klimabedingungen, höchstwahrscheinlich als Resultat besonderer regionaler atmosphärischer Zirkulationsverhältnisse. Eine antizyklonale Zirkulationszelle als Resultat eines Hochdruckgebiets über dem Rest des Skandinavischen Eisschilds verhinderte wahrscheinlich das Vordringen warmer und feuchter Luftmassen aus Westen und verursachte damit eine Abschwächung der frühholozänen Klimaverbesserung in dieser Region bis zum endgültigen Zerfall des Eisschilds, was grundsätzlich von der frühholozänen Klimaentwicklung in Westeuropa abweicht. Die spätglazialen Sedimente des Mondsees (Oberösterreich) wurden im Hinblick auf die regionale Klimaentwicklung und die Reaktion des Ökosystems auf abrupte Klimaschwankungen untersucht. Während die Erwärmung zu Beginn des Holozäns von einer zeitgleichen Reaktion des Ökosystems begleitet wurde, war die Reaktion des Ökosystems auf die Erwärmung zu Beginn des Spätglazials deutlich verzögert. Insbesondere die Ausbreitung von Nadelwäldern und die Reduktion des klastischen Eintrags folgten der spätglazialen Erwärmung erst mit einer Verzögerung von ca. 500–750 Jahren. Die Abkühlung zu Beginn der Jüngeren Dryas war durch eine deutliche Synchronizität zwischen Temperatur- und Vegetationsänderung gekennzeichnet, wohingegen der Anstieg des klastischen Eintrags erst 150–300 Jahre verzögert folgte. Eine komplexe Reaktion des Ökosystems zeigt sich auch während kurzfristiger spätglazialer Klimaschwankungen. Zusammenfassend lässt sich sagen, dass abrupte Klimaveränderungen durch komplexe und zeitlich variable Reaktionsmuster des Ökosystems gekennzeichnet sind, die hauptsächlich von dessen Klimasensitivität und den ökologischen Ausgangsbedingungen abhängen. Eine zweite Studie an den Sedimenten des Mondsees konzentrierte sich auf zwei Klimaschwankungen vor ca. 8200 und 9100 Jahren, für die Schmelzwassereintrag in den Nordatlantik und ein damit verbundenes Zusammenbrechen der thermohalinen Zirkulation als Ursache angesehen wird. Durch Warvenzählungen und 14C-Datierungen konnten sowohl die Dauer (ca. 150 Jahre) als auch das absolute Alter der Kältephase vor ca. 8200 Jahren zuverlässig bestimmt werden, welche in guter Übereinstimmung mit Resultaten aus anderen Paläoklimaarchiven stehen. Darüber hinaus wurde eine kurze Warmphase direkt im Anschluss an das Abkühlungsereignis identifiziert, die auch in anderen Klimaarchiven im nordatlantischen Raum nachweisbar ist. Diese wurde wahrscheinlich durch ein Wiedererstarken der thermohalinen Zirkulation verursacht, welches darüber hinaus eine Verschiebung ozeanischer und atmosphärischer Frontsysteme zur Folge hatte. Obwohl andere Klimaarchive auch nach dem Abkühlungsereignis vor ca. 9100 Jahren auf ein Wiedererstarken der thermohalinen Zirkulation hindeuten, finden sich in den Sedimenten des Mondsees keine Anzeichen für eine solche Wärmeperiode, was die Komplexität des globalen Klimasystems verdeutlicht. Die holozänen Sedimente des Lago d’Iseo (Norditalien) wurden im Hinblick auf die regionale Erdbebenaktivität und den Einfluss von Klima und Mensch auf Erosionsprozesse im Einzugsgebiet und den klastischen Eintrag in den See untersucht. Zahlreiche kleinere detritische Lagen in den Sedimenten spiegeln Eintrag durch extreme Oberflächenabflussereignisse wieder. Während des Früh- und Mittelholozäns zeigt sich eine deutliche Übereinstimmung zwischen erhöhtem klastischen Eintrag und kühleren und feuchteren Klimaverhältnissen, was auf einen dominanten Einfluss der natürlichen Klimavariabilität hindeutet. Im Gegensatz dazu zeigen Phasen erhöhten klastischen Eintrags während des Spätholozäns teilweise auch eine Korrelation mit erhöhter Siedlungsaktivität, was die Komplexität der Einflüsse auf Erosionsprozesse im Einzugsgebiet verdeutlicht. Darüber hinaus konnten auch fünf größere Ereignislagen nachgewiesen werden, welche durch Rutschmassen und Turbidite gekennzeichnet sind und für die lokale Erdbeben als Ursache vermutet werden. Die jüngste Ereignislage kann mit einem historisch dokumentierten proximalen Erdbeben im Jahr AD 1222 korreliert werden. Für die anderen vier Ereignislagen werden bisher undokumentierte prähistorische Erdbeben als Ursache angenommen.

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.

Detailed information on past oceanographic and climatic changes is crucial for our understanding of natural climate variability and for the assessment of future climate variations. Sediments strongly influenced by the North Atlantic Current accumulate at high rates in the northeastern Skagerrak, forming a potential highresolution archive for information on past climatic and oceanographic processes and events. Through a highresolution, multi-proxy study of the 32 meter long core MD99-2286 from the north-eastern Skagerrak, and interpretation of chirp sonar profiles from the coring area, this thesis provides new and detailed insights about the paleoceanographic development of the eastern North Sea region since the deglaciation. The chronostratigraphic control of core MD99-2286 relies on 27 radiocarbon dates. Ages are presented in calibrated thousand years before present (abbreviated “kyr”). Core MD99-2286 was correlated to chirp sonar profiles using measured physical properties. This correlation demonstrates that a strong regional acoustic reflector, previously assumed to represent the Pleistocene/Holocene boundary, was formed as a result of rapid ice retreat during the latest Pleistocene. Based on the distribution of ice rafted debris in the core, ice berg calving in the Skagerrak ended at 10.7 kyr. Detailed grain-size analyses of the core were interpreted using a novel 3D-visualization technique. Between 11.3 and 10.3 kyr, clay-rich distal glacial marine sediments were deposited in the northeastern Skagerrak, derived from Baltic melt-water outflow across south-central Sweden through the Otteid-Stenselva strait. As a result of differential isostatic uplift, the route of the major outflow and the associated sediment deposition moved southwards along the Swedish west coast. After 10.3 kyr, sediment deposition in the north-eastern Skagerrak gradually adopted to a fully interglacial normal marine sedimentation dominated by Atlantic inflow and the North Jutland Current. The establishment of the modern circulation system in the eastern North Sea is marked by abrupt coarsening of the sediments in core MD99-2286 at 8.5 kyr. This was a result of increased Atlantic inflow, opening of the English Channel and the Danish straits, and formation of the South Jutland Current. Mineral magnetic properties of the core show a distinct relationship reflecting general sediment source variability. After 8.5 kyr, sediments in the northeastern Skagerrak were derived predominantly from the Atlantic Ocean and the North Sea, with varying contributions from the South Jutland Current, the Baltic Current, and the currents along the coasts of western Sweden and southern Norway. Between 6.3 and 3.8 kyr, the eastern North Sea was further developed towards the modern situation by an increase of the South Jutland Current flow. The Skagerrak bottom currents were probably forced by strong Atlantic water inflow between 0.9 and 0.5 kyr, and after that by increased wind stress. The influence of regional climate on the eastern North Sea circulation has increased since the middle of the Holocene.