Palaeotsunami imprints in the near-coast sedimentary records of the Gulfs of Lakonia and Argolis (Peloponnese, Greece)

From historical accounts it is well-known that the coasts of the Gulfs of Lakonia and Argolis (southern and eastern Peloponnese, Greece) have been repeatedly affected by tsunamis during historical times. It is assumed that these palaeotsunamis left sedimentological and geomorphological traces in the geological record which are still detectable these days. As both gulfs are located within one of the seismically most active regions in whole western Eurasia in particular the nearby Hellenic Trench is regarded as the main trigger for tsunami generation. Against this background, selected near-coast sedimentary archives were studied by means of sedimentological, geomorphological, geophysical, geochemical and microfaunal investigations in order to detect signatures of Holocene palaeotsunamigenic activity. The investigations revealed allochthonous sediment layers featuring distinctive sedimentary characteristics of marine high-energy event deposits in most of the investigated study areas. In order to differentiate between the geomorphodynamic driving mechanisms for the deposition of the associated marine high-energy event layers, a multi-method approach was used. The detected high-energy marine deposits are suggested to be of tsunamigenic origin. Radiocarbon dating results allowed establishing local event geo-chronostratigraphies and correlations on a local and regional scale as well as correlations with already described palaeotsunami findings on a supra-regional scale. The geochronological dataset attests repeated tsunamigenic activity at least since the 5th millennium BC up to the 17th century AD. For the studied areas in southeastern Lakonia up to four palaeotsunami event generations were identified, for central Lakonia three and for the investigated areas around the Argolis Gulf also up to four. Comparing the findings with literature data, chronological correlations were found with palaeotsunami deposits detected in near-coast geological archives of Akarnania, of the southwestern, the western and northwestern Peloponnese, with event deposits found on Crete and on the Ionian Islands of Cefalonia and Lefkada as well as with findings from southeastern Sicily (Italy) and Cesarea (Israel). By the identification of multiple palaeotsunami event layers, disturbing autochthonous near-coast sedimentary records of the Gulfs of Lakonia and Argolis during the last seven millennia, a significant tsunami frequency is attested for these regions.

Holocene tsunami events in the Eastern Ionian Sea - Geoscientific evidence from Cefalonia and the western Peloponnese (Greece)

This study presents geo-scientific evidence for Holocene tsunami impact along the shores of the Eastern Ionian Sea. Cefalonia Island, the Gulf of Kyparissia and the Gialova Lagoon were subject of detailed geo-scientific investigations. It is well known that the coasts of the eastern Mediterranean were hit by the destructive influence of tsunamis in the past. The seismically highly active Hellenic Trench is considered as the most significant tsunami source in the Eastern Ionian Sea. This study focuses on the reconstruction and detection of sedimentary signatures of palaeotsunami events and their influence on the Holocene palaeogeographical evolution. The results of fine grained near coast geo-archives are discussed and interpreted in detail to differentiate between tsunami, storm and sea level highstands as sedimentation processes.rnA multi-method approach was applied using geomorphological, sedimentological, geochemical, geophysical and microfaunal analyses to detect Holocene tsunamigenic impact. Chronological data were based on radiocarbondatings and archaeological age estimations to reconstruct local geo-chronostratigraphies and to correlate them on supra-regional scales.rnDistinct sedimentary signatures of 5 generations of tsunami impact were found along the coasts of Cefalonia in the Livadi coastal plain. The results show that the overall coastal evolution was influenced by tsunamigenic impact that occured around 5700 cal BC (I), 4250 cal BC (II), at the beginning of the 2nd millennium cal BC (III), in the 1st millennium cal BC (IV) and posterior to 780 cal AD (V). Sea level reconstructions and the palaeogeographical evolution show that the local Holocene sea level has never been higher than at present.rnAt the former Mouria Lagoon along the Gulf of Kyparissia almost four allochtonous layers of tsunamigenic origin were identified. The stratigraphical record and palaeogeographical reconstructions show that major environmental coastal changes were linked to these extreme events. At the southern end of the Agoulenitsa Lagoon at modern Kato Samikon high-energy traces were found more than 2 km inland and upt ot 9 m above present sea level. The geo-chronological framework deciphered tsunami landfall for the 5th millennium cal BC (I), mid to late 2nd mill. BC (II), Roman times (1st cent. BC to early 4th cent. AD) (III) and most possible one of the historically well-known 365 AD or 521/551 AD tsunamis (IV).rnCoarse-grained allochthonous sediments of marine origin were found intersecting muddy deposits of the quisecent sediments of the Gialova Lagoon on the southwestern Peloponnese. Radiocarbondatings suggest 6 generations of major tsunami impact. Tsunami generations were dated to around 3300 cal BC (I), around the end of 4th and the beginning of 3rd millennium BC (II), after around 1100 cal BC (III), after the 4th to 2nd cent. BC (IV), between the 8th and early 15th cent. AD (V) and between the mid 14th to beginning of 15th cent. AD (VI). Palaeogeographical and morphological characteristics in the environs of the Gialova Lagoon were controlled by high-energy influence.rnSedimentary findings in all study areas are in good accordance to traces of tsunami events found all over the Ionian Sea. The correlation of geo-chronological data fits very well to coastal Akarnania, the western Peloponnese and finding along the coasts of southern Italy and the Aegean. Supra-regional influence of tsunamigenic impact significant for the investigated sites. The palaeogeographical evolution and palaeo-geomorphological setting of the each study area was strongly affected by tsunamigenic impact.rnThe selected geo-archives represent extraordinary sediment traps for the reconstruction of Holocene coastal evolution. Our result therefore give new insight to the exceptional high tsunami risk in the eastern Mediterranean and emphasize the underestimation of the overall tsunami hazard.

Ancient Greek harbours used as geo-archives for palaeotsunami research : case studies from Krane (Cefalonia), Lechaion (Gulf of Corinth) and Kyllini (Peloponnese)

Since historical times, coastal areas throughout the eastern Mediterranean are exposed to tsunami hazard. For many decades the knowledge about palaeotsunamis was solely based on historical accounts. However, results from timeline analyses reveal different characteristics affecting the quality of the dataset (i.e. distribution of data, temporal thinning backward of events, local periodization phenomena) that emphasize the fragmentary character of the historical data. As an increasing number of geo-scientific studies give convincing examples of well dated tsunami signatures not reported in catalogues, the non-existing record is a major problem to palaeotsunami research. While the compilation of historical data allows a first approach in the identification of areas vulnerable to tsunamis, it must not be regarded as reliable for hazard assessment. Considering the increasing economic significance of coastal regions (e.g. for mass tourism) and the constantly growing coastal population, our knowledge on the local, regional and supraregional tsunami hazard along Mediterranean coasts has to be improved. For setting up a reliable tsunami risk assessment and developing risk mitigation strategies, it is of major importance (i) to identify areas under risk and (ii) to estimate the intensity and frequency of potential events. This approach is most promising when based on the analysis of palaeotsunami research seeking to detect areas of high palaeotsunami hazard, to calculate recurrence intervals and to document palaeotsunami destructiveness in terms of wave run-up, inundation and long-term coastal change. Within the past few years, geo-scientific studies on palaeotsunami events provided convincing evidence that throughout the Mediterranean ancient harbours were subject to strong tsunami-related disturbance or destruction. Constructed to protect ships from storm and wave activity, harbours provide especially sheltered and quiescent environments and thus turned out to be valuable geo-archives for tsunamigenic high-energy impacts on coastal areas. Directly exposed to the Hellenic Trench and extensive local fault systems, coastal areas in the Ionian Sea and the Gulf of Corinth hold a considerably high risk for tsunami events, respectively.Geo-scientific and geoarcheaological studies carried out in the environs of the ancient harbours of Krane (Cefalonia Island), Lechaion (Corinth, Gulf of Corinth) and Kyllini (western Peloponnese) comprised on-shore and near-shore vibracoring and subsequent sedimentological, geochemical and microfossil analyses of the recovered sediments. Geophysical methods like electrical resistivity tomography and ground penetrating radar were applied in order to detect subsurface structures and to verify stratigraphical patterns derived from vibracores over long distances. The overall geochronological framework of each study area is based on radiocarbon dating of biogenic material and age determination of diagnostic ceramic fragments. Results presented within this study provide distinct evidence of multiple palaeotsunami landfalls for the investigated areas. Tsunami signatures encountered in the environs of Krane, Lechaion and Kyllini include (i) coarse-grained allochthonous marine sediments intersecting silt-dominated quiescent harbour deposits and/or shallow marine environments, (ii) disturbed microfaunal assemblages and/or (iii) distinct geochemical fingerprints as well as (iv) geo-archaeological destruction layers and (v) extensive units of beachrock-type calcarenitic tsunamites. For Krane, geochronological data yielded termini ad or post quem (maximum ages) for tsunami event generations dated to 4150 ± 60 cal BC, ~ 3200 ± 110 cal BC, ~ 650 ± 110 cal BC, and ~ 930 ± 40 cal AD, respectively. Results for Lechaion suggest that the harbour was hit by strong tsunami impacts in the 8th-6th century BC, the 1st-2nd century AD and in the 6th century AD. At Kyllini, the harbour site was affected by tsunami impact in between the late 7th and early 4th cent. BC and between the 4th and 6th cent. AD. In case of Lechaion and Kyllini, the final destruction of the harbour facilities also seems to be related to the tsunami impact. Comparing the tsunami signals obtained for each study areas with geo-scientific data from palaeotsunami events from other sites indicates that the investigated harbour sites represent excellent geo-archives for supra-regional mega-tsunamis.

Geochemie, Geochronologie und Isotopie der Grundgebirgsgneise und ausgewählter Marmore der zentralen Kykladen, Griechenland

Das Attisch-Kykladische Massiv ist Teil der Helleniden, einem Gebirgszug im östlichen Mittelmeerraum zwischen Alpen und Himalaya. Seit dem späten Mesozoikum unterlag diese Region dem Einfluß der alpidischen Orogenphasen. Die vorliegende Arbeit befasst sich mit den präalpidischen Grundgebirgseinheiten der Kykladen, die durch grünschieferfaziell überprägte Gneise und Marmore repräsentiert werden. Diese wurden geochemisch und isotopisch analysiert. Geochemisch stellen sie granitische und granodioritische Orthogneise subalkalinen, peraluminösen Charakters dar. Ihre Haupt- und Spurenelementsignaturen deuten auf die Existenz separater Schmelzen ähnlicher krustaler Zusammensetzung hin. Dies reflektiert auch die Rb/Sr- und Sm/Nd-Isotopie mit Errorchronenaltern von ca. 310 Ma. Die 87Sr/86Sri-Zusammensetzung besitzt einen rel. niedrigen Mittelwert von 0.7072±0.0019. Das 143Nd/144Ndi-Verhältnis von 0.51187±0.00011 korrespondiert mit leicht erhöhten eNd-Werten zwischen -8 und –7, was auf komplex zusammengesetzte Ausgangsschmelzen deutet (Hybridtyp "Hs" ). Zirkonanalysen liefern magmatische Intrusionsalter von 300 Ma, ererbte Körner bis zu 2305±1 Ma, was die Beteiligung alter Kontinentalkruste belegt. Das Tectonic Setting befindet sich im aktiven Kontinentalrand und wird als VAG klassifiziert. Ausgewählte Marmore von Naxos weisen ein relativ niedriges 87Sr/86Sr-Verhältnis von 0.707295±0.000012 auf, das mit dem des Meerwassers während des Mittleren Juras übereinstimmt und mit dem Pb/Pb-Isochronenalter von 172±17 Ma korreliert

European phylogeography of the coastal plants Cakile maritima Scop. (Brassicaceae) and Eryngium maritimum L. (Apiaceae)

Linear dispersal systems, such as coastal habitats, are well suited for phylogeographic studies because of their low spatial complexity compared to three dimensional habitats. Widely distributed coastal plant species additionally show azonal and often essentially continuous distributions. These properties, firstly, make it easier to reconstruct historical distributions of coastal plants and, secondly, make it more likely that present distributions contain both Quaternary refugia and recently colonized areas. Taken together this makes it easier to formulate phylogeographic hypotheses. This work investigated the phylogeography of Cakile maritima and Eryngium maritimum, two species growing in sandy habitats along the north Atlantic Ocean and the Mediterranean Sea coasts on two different spatial scales using AFLP data. The genetic structure of these species was investigated by sampling single individuals along most of their distributions from Turkey to south Sweden. On a regional scale the population genetic structure of both species was also studied in detail in the Bosporus and Dardanelles straits, the Strait of Gibraltar and along a continuous stretch of dunes in western France. Additionally, populations of C. maritima were investigated in the Baltic Sea/Kattegat/North Sea area. Over the complete sampling range the species show both differences and similarities in their genetic structure. In the Mediterranean Sea, both species contain Aegean Sea/Black Sea and west Mediterranean clusters. Cakile maritima additionally shows a clustering of Ionian Sea/Adriatic Sea collections. Further, both species show a subdivision of Atlantic Ocean/North Sea/Baltic Sea material from Mediterranean. Within the Atlantic Ocean group, C. maritima from the Baltic Sea and the most northern Atlantic localities form an additional cluster while no such substructure was found in E. maritimum. In all three instances where population genetic investigations of both species were performed in the same area, the results showed almost complete congruency of spatial genetic patterns. In the Aegean/Black Sea/Marmara region a subdivision of populations into a Black Sea, a Sea of Marmara and an Aegean Sea group is shared by both species. In addition the Sea of Marmara populations are more close to the Aegean Sea populations than they are to the Black Sea populations in both cases. Populations from the Atlantic side of the Strait of Gibraltar are differentiated from those on the Mediterranean side in both species, a pattern that confirms the results of the wide scale study. Along the dunes of West France no clear genetic structure could be detected in any of the species. Additionally, the results from the Baltic Sea/North Sea populations of C. maritima did not reveal any geographical genetic pattern. It is postulated that the many congruencies between the species are mainly due to a predominantly sea water mediated seed dispersal in both species and their shared sandy habitat. The results are compared to hypothetical distributions for the last glacial maximum based on species specific temperature requirements. It is argued that in both species the geographical borders of the clusters in the Mediterranean area were not affected by quaternary temperature changes and that the Aegean/Black Sea/Marmara cluster, and possibly the Ionian Sea/Adriatic Sea cluster in C. maritima, is the result of sea currents that isolate these basins from the rest of the sampled areas. The genetic gap in the Strait of Gibraltar between Atlantic Ocean and Mediterranean Sea populations in both species is also explained in terms of sea currents. The existence of three subgroups corresponding to the Aegean Sea, Black Sea and Sea of Marmara basins is suggested to have arisen due to geographical isolation during periods of global sea regressions in the glacials. The population genetic evidence was inconclusive regarding the Baltic Sea cluster of C. Maritima from the wide scale study. The results of this study are very similar to those of an investigation of three other coastal plant species over a similar range. This suggests that the phylo-geographic patterns of widespread coastal plants may be more predictable than those of other terrestrial plants.

The pre-alpine evolution of the basement of the Pelagonian Zone and the Vardar Zone, Greece

The Pelagonian Zone and the Vardar Zone in Greece represent the western part of the Hellenide hinterland (Internal Hellenides). While the Pelagonian Zone comprises predominantly crystalline basement and sedimentary cover rocks, the Vardar Zone has long been regarded as an ophiolite-decorated suture zone separating the Pelagonian Zone from the Serbo-Macedonian Massif to the east. Felsic basement rocks from both areas, with the main focus put on the Pelagonian Zone, were dated in order to identify the major crust-forming episodes and to improve the understanding of the evolutionary history of the region. The interpretation of the single-zircon geochronology results was aided by geochemical investigations. The majority of the basement rocks from the Pelagonian Zone yielded Permo-Carboniferous intrusion ages around 300 Ma, underlining the importance of this crust-forming event for the Internal Hellenides of Greece. Geochemically these basement rocks are classified as subduction-related granitoids, which formed in an active continental margin setting. An important result was the identification of a Precambrian crustal unit within the crystalline basement of the Pelagonian Zone. Orthogneisses from the NW Pelagonian Zone yielded Neoproterozoic ages of c. 700 Ma and are so far the oldest known rocks in Greece. These basement rocks, which are also similar to active margin granitoids, were interpreted as remnants of a terrane, the Florina Terrane, which can be correlated to a Pan-African or Cadomian arc. Since the gneisses contain inherited zircons of Middle to Late Proterozoic ages, the original location of the Florina Terrane was probably at the northwestern margin of Gondwana. In the Vardar Zone an important phase of Upper Jurassic felsic magmatism is documented by igneous formation ages ranging from 155 to 164 Ma. The chemical and isotopic composition of these rocks is also in accord with their formation in a volcanic-arc setting at an active continental margin. Older continental material incorporated in the Vardar Zone is documented by 319-Ma-old gneisses and by inherited zircons of mainly Middle Palaeozoic ages. The prevalence of subduction-related igneous rocks indicates that arc formation and accretion orogeny were the most important processes during the evolution of this part of the Internal Hellenides. The geochronological results demonstrate that most of the Pelagonian Zone and the Vardar Zone crystalline basement formed during distinct pre-Alpine episodes at c. 700, 300 and 160 Ma with a predominance of the Permo-Carboniferous magmatic phase.

Climate signatures in corals of the tropical-temperate transition zone (Late Miocene, Crete/Greece)

The present study describes a Late Miocene (early Tortonian - early Messinian) transitional carbonate system that combines elements of tropical and cool-water carbonate systems (Irakleion Basin, island of Crete, Greece). As documented by stratal geometries, the submarine topography of the basin was controlled by tilting blocks. Coral reefs formed by Porites and Tarbellastrea occurred in a narrow clastic coastal belt along a „central Cretan landmass“, and steep escarpments formed by faulting. Extensive covers of level-bottom communities existed in a low-energy environment on the gentle dip-slope ramps of the blocks that show the widest geographical distribution within the basin. Consistent patterns of landward and basinward shift of coastal onlap in all outcrop studies reveal an overriding control of 3rd and 4th order sea level changes on sediment dynamics and facies distributions over block movements. An increasingly dry climate and the complex submarine topography of the fault block mosaic kept sediment and nutrient discharge at a minimum. The skeletal limestone facies therefore reflects oligotrophic conditions and a sea surface temperature (SST) near the lower threshold temperature of coral reefs in a climatic position transitional between the tropical coral reef belt and the temperate zone. Stable isotope records (δ18O, δ13C) from massiv, exceptionally preserved Late Miocene aragonite coral skeletons reflect seasonal changes in sea surface temperature and symbiont autotrophy. Spectral analysis of a 69 years coral δ18O record reveals significant variance at interannual time scales (5-6 years) that matches the present-day eastern Mediterranean climate variability controlled by the Arctic Oscillation/North Atlantic Oscillation (AO/NAO), the Northern Hemisphere’s dominant mode of atmospheric variability. Supported by simulations with a complex atmospheric general circulation model coupled to a mixed-layer ocean model, it is suggested, that climate dynamics in the eastern Mediterranean and central Europe reflect atmospheric variability related to the Icelandic Low 10 million years ago. Usually, Miocene corals are transformed in calcite spar in geological time and isotope values are reset by diagenetic alteration. It is demonstrated that the relicts of growth bands represent an intriguing source of information for the growth conditions of fossil corals. Recrystallized growth bands were measured systematically in massive Porites from Crete. The Late Miocene corals were growing slowly with 2-4 mm/yr, compatible with present-day Porites from high latitude reefs, a relationship that fits the position of Crete at the margin of the Miocene tropical reef belt. Over Late Miocene time (Tortonian - early Messinian) growth rates remained remarkably constant, and if the modern growth temperature relationship for massive Porites applies to the Neogene, minimum (winter) SST did not exceed 19-21°C.

Entwicklung einer Anordnung zur Nutzung von Massenschwerebewegungen beim Quarzitabbau im Rheinischen Schiefergebirge

Die (Wieder-)Nutzung auf Schwerkraft basierender Fördertechniken, die insbesondere durch das niedrige Energiepreisniveau in den Jahrzehnten nach dem 2. Weltkrieg in der Tagebautechnik nahezu vollständig verdrängt wurden, ist bei den heutigen wirtschaftlichen Randbedingungen und anzustrebenden ökologischen Standards eine Herausforderung für die bergbautreibende Industrie. Seit Aufnahme der Entwicklung des Förderkonzeptes – Geführte Versturztechnik – Mitte der 1990er Jahre haben sich die Kosten für Rohöl vor Steuern nach dem Tiefstand um das Jahr 1998 bis heute mehr als verdreifacht, alleine seit 2004 mehr als verdoppelt. Gesetzliche Regelwerke wie die europäische IVU-Richtlinie 96/61/EG zur „integrierten Vermeidung und Verminderung der Umweltverschmutzung“ fordern, Genehmigungen nur noch bei Einsatz der besten verfügbaren Techniken (BVT oder BAT: „best available techniques“) zu erteilen. Die Umsetzung in nationale Vorschriften wie das Bundes-Immissionsschutzgesetz und nachgeordnete Regelwerke fordern hierauf aufbauend, dass Umweltbelastungen nicht in andere Medien verlagert werden dürfen. Die Anordnung einer Versturzrinne zur Nutzung von Massenschwerebewegungen am Beispiel von Quarzitabbau im Rheinischen Schiefergebirge bei denen die Förderbezugsebene unterhalb der Strossen liegt, die zur sichern und selektiven Gewinnung des Rohstoffs aufgefahren werden müssen, erfüllt durch Rückgriff auf ein vermeintlich „archaisches“ Förderkonzept durch Nutzung der Schwerkraft die obigen Anforderungen. Offenkundige Umweltbelastungen, die alleine durch die Verbrennung von Dieselkraftstoff und hieraus resultierender Schadstoff- und Wärmeeinträge in die Luft beim verbreiteten Einsatz von SLKW zur Abwärtsförderung entstehen, können erheblich vermindert werden. Der Aspekt der Betriebssicherheit einer solchen Anordnung kann durch Auffahren eines geradlinigen Bauwerks mit an das Fördergut angepassten Dimensionen sowie Einrichtungen zur Beschränkung der kinetischen Energie erreicht werden. Diese stellen auch gleichzeitig sicher, dass die Zerkleinerung des durch die Versturzrinne abwärts transportierten Materials betrieblich zulässige Grenzen nicht überschreitet. Hierfür kann auf das umfangreiche Wissen zu Massenschwerebewegungen Rückgriff genommen werden. Dem Aspekt des Umweltschutzes, der sich in Bezug auf das Medium Luft auf den autochtonen Staub reduziert, kann durch Vorrichtungen zur Staubniederschlagung Rechnung getragen werden. Vertiefende Untersuchungen sind erforderlich, um die mit komplexen, aber erprobten Techniken arbeitende Tagebauindustrie auch in dicht besiedelten Regionen wieder an die Nutzung von Schwerkraft (-gestützten) Fördertechniken heranzuführen. Auch das Konzept – Geführte Versturztechnik – ist auf konkrete Anwendungsfälle hin in Details anzupassen.

Applications of remote sensing and geographic information systems in geomorphological studies: Safaga - El Quseir area, Red Sea coast, Egypt as an example

In den letzten drei Jahrzehnten sind Fernerkundung und GIS in den Geowissenschaften zunehmend wichtiger geworden, um die konventionellen Methoden von Datensammlung und zur Herstellung von Landkarten zu verbessern. Die vorliegende Arbeit befasst sich mit der Anwendung von Fernerkundung und geographischen Informationssystemen (GIS) für geomorphologische Untersuchungen. Durch die Kombination beider Techniken ist es vor allem möglich geworden, geomorphologische Formen im Überblick und dennoch detailliert zu erfassen. Als Grundlagen werden in dieser Arbeit topographische und geologische Karten, Satellitenbilder und Klimadaten benutzt. Die Arbeit besteht aus 6 Kapiteln. Das erste Kapitel gibt einen allgemeinen Überblick über den Untersuchungsraum. Dieser umfasst folgende morphologische Einheiten, klimatischen Verhältnisse, insbesondere die Ariditätsindizes der Küsten- und Gebirgslandschaft sowie das Siedlungsmuster beschrieben. Kapitel 2 befasst sich mit der regionalen Geologie und Stratigraphie des Untersuchungsraumes. Es wird versucht, die Hauptformationen mit Hilfe von ETM-Satellitenbildern zu identifizieren. Angewandt werden hierzu folgende Methoden: Colour Band Composite, Image Rationing und die sog. überwachte Klassifikation. Kapitel 3 enthält eine Beschreibung der strukturell bedingten Oberflächenformen, um die Wechselwirkung zwischen Tektonik und geomorphologischen Prozessen aufzuklären. Es geht es um die vielfältigen Methoden, zum Beispiel das sog. Image Processing, um die im Gebirgskörper vorhandenen Lineamente einwandfrei zu deuten. Spezielle Filtermethoden werden angewandt, um die wichtigsten Lineamente zu kartieren. Kapitel 4 stellt den Versuch dar, mit Hilfe von aufbereiteten SRTM-Satellitenbildern eine automatisierte Erfassung des Gewässernetzes. Es wird ausführlich diskutiert, inwieweit bei diesen Arbeitsschritten die Qualität kleinmaßstäbiger SRTM-Satellitenbilder mit großmaßstäbigen topographischen Karten vergleichbar ist. Weiterhin werden hydrologische Parameter über eine qualitative und quantitative Analyse des Abflussregimes einzelner Wadis erfasst. Der Ursprung von Entwässerungssystemen wird auf der Basis geomorphologischer und geologischer Befunde interpretiert. Kapitel 5 befasst sich mit der Abschätzung der Gefahr episodischer Wadifluten. Die Wahrscheinlichkeit ihres jährlichen Auftretens bzw. des Auftretens starker Fluten im Abstand mehrerer Jahre wird in einer historischen Betrachtung bis 1921 zurückverfolgt. Die Bedeutung von Regentiefs, die sich über dem Roten Meer entwickeln, und die für eine Abflussbildung in Frage kommen, wird mit Hilfe der IDW-Methode (Inverse Distance Weighted) untersucht. Betrachtet werden außerdem weitere, regenbringende Wetterlagen mit Hilfe von Meteosat Infrarotbildern. Genauer betrachtet wird die Periode 1990-1997, in der kräftige, Wadifluten auslösende Regenfälle auftraten. Flutereignisse und Fluthöhe werden anhand von hydrographischen Daten (Pegelmessungen) ermittelt. Auch die Landnutzung und Siedlungsstruktur im Einzugsgebiet eines Wadis wird berücksichtigt. In Kapitel 6 geht es um die unterschiedlichen Küstenformen auf der Westseite des Roten Meeres zum Beispiel die Erosionsformen, Aufbauformen, untergetauchte Formen. Im abschließenden Teil geht es um die Stratigraphie und zeitliche Zuordnung von submarinen Terrassen auf Korallenriffen sowie den Vergleich mit anderen solcher Terrassen an der ägyptischen Rotmeerküste westlich und östlich der Sinai-Halbinsel.

Geochemistry, petrogenesis and tectonic setting of ophiolites and mafic-ultramafic complexes in the Northeastern Aegean Region

In this study two ophiolites and a mafic-ultramafic complexes of the northeastern Aegean Sea, Greece, have been investigated to re-evaluate their petrogenetic evolution and tectonic setting. These complexes are: the mafic-ultramafic complex of Lesvos Island and the ophiolites of Samothraki Island and the Evros area. In order to examine these complexes in detail whole-rock major- and trace-elements as well as Sr and Nd isotopes, and minerals were analysed and U-Pb SHRIMP ages on zircons were determined. The mafic-ultramafic complex of Lesvos Island consists of mantle peridotite thrusted over a tectonic mélange containing metasediments, metabasalts and a few metagabbros. This succession had previously been interpreted as an ophiolite of Late Jurassic age. The new field and geochemical data allow a reinterpretation of this complex as representing an incipient continental rift setting that led to the subsequent formation of the Meliata-Maliac-Vardar branches of Neotethys in Upper Permian times (253 ± 6 Ma) and the term “Lesvos ophiolite” should be abandoned. With proceeding subduction and closure of the Maliac Ocean in Late Jurassic times (155 Ma) the Lesvos mafic-ultramafic complex was obducted. Zircon ages of 777, 539 and 338 Ma from a gabbro strongly suggest inheritance from the intruded basement and correspond to ages of distinct terranes recently recognized in the Hellenides (e.g. Florina terrane). Geochemical similar complexes which contain rift associations with Permo-Triassic ages can be found elsewhere in Greece and Turkey, namely the Teke Dere Thrust Sheet below the Lycian Nappes (SW Turkey), the Pindos subophiolitic mélange (W Greece), the Volcanosedimentary Complex on Central Evia Island (Greece) and the Karakaya Complex (NW Turkey). This infers that the rift-related rocks from Lesvos belong to an important Permo-Triassic rifting episode in the eastern Mediterranean. The ‘in-situ’ ophiolite of Samothraki Island comprises gabbros, sparse dykes and basalt flows as well as pillows cut by late dolerite dykes and had conventionally been interpreted as having formed in an ensialic back-arc basin. The results of this study revealed that none of the basalts and dolerites resemble mid-ocean ridge or back-arc basin basalts thus suggesting that the Samothraki ophiolite cannot represent mature back-arc basin crust. The age of the complex is regarded to be 160 ± 5 Ma (i.e. Oxfordian; early Upper Jurassic), which precludes any correlation with the Lesvos mafic-ultramafic complex further south (253 ± 6 Ma; Upper Permian). Restoration of the block configuration in NE Greece, before extensional collapse of the Hellenic hinterland and exhumation of the Rhodope Metamorphic Core Complex (mid-Eocene to mid-Miocene), results in a continuous ophiolite belt from Guevgueli in the NW to Samothraki in the SE, thus assigning the latter to the Innermost Hellenic Ophiolite Belt. In view of the data of this study, the Samothraki ophiolite represents a rift propagation of the Sithonia ophiolite spreading ridge into the Chortiatis calc-alkaline arc. The ophiolite of the Evros area consists of a plutonic sequence comprising cumulate and non-cumulate gabbros with plagiogranite veins, and an extrusive sequence of basalt dykes, massive and pillow lavas as well as pyroclastic rocks. Furthermore, in the Rhodope Massif tectonic lenses of harzburgites and dunites can be found. All rocks are spatially separated. The analytical results of this study revealed an intra-oceanic island arc setting for the Evros ophiolitic rocks. During late Middle Jurassic times (169 ± 2 Ma) an intra-oceanic arc has developed above a northwards directed intra-oceanic subduction zone of the Vardar Ocean in front of the Rhodope Massif. The boninitic, island arc tholeiitic and calc-alkaline rocks reflect the evolution of the Evros island arc. The obduction of the ophiolitic rocks onto the Rhodope basement margin took place during closure of the Vardar ocean basins. The harzburgites and dunites of the Rhodope Massif are strongly depleted and resemble harzburgites from recent oceanic island arcs. After melt extraction they underwent enrichment processes by percolating melts and fluids from the subducted slab. The relationship of the peridotites and the Evros ophiolite is still ambiguous, but the stratigraphic positions of the peridotites and the ophiolitic rocks indicate separated origin. The harzburgites and dunites most probably represent remnants of the mantle wedge of the island arc of the Rhodope terrane formed above subducted slab of the Nestos Ocean in late Middle Jurassic times. During collision of the Thracia terrane with the Rhodope terrane thrusting of the Rhodope terrane onto the Thracia terrane took place, whereas the harzburgites and dunites were pushed between the two terranes now cropping out on top of the Thracia terrane of the Rhodope Massif.

Evolution of South African Bruniaceae: evidence from ecological and geographical investigations

The central aim of the present study was to analyse ecological and geographical mechanisms that led to the species diversity and distribution pattern of the South African (sub-) endemic Bruniaceae shown today. To answer the question if the endangerment of some species and the sometimes restricted distribution area is due to an incongruence of pollination and breeding system, pollinator observations and the breeding system were analysed. rnThe effectiveness of the plant-pollinator interactions should be reflected in the reproductive success wherefore fruit set analyses were carried out. The genetic constitution of distant and close-by populations along a spatial gradient should illuminate gene-flow or habitat isolation that could have led to the species diversity. Since niche-inhabitation could be shown in the present study, an overall biogeographical analysis illuminated the distribution pattern on family level and the geographical as well as ecological factors that led to species persistence. rnThe study illuminated that the plant-pollinator interactions and the breeding system are adaptations to the fynbos biome but can not be defined as factors that drove speciation or have tremendous influence on distribution of Bruniaceae. In fact the geography of South Africa with its fragmented landscape as well as close niche-inhabitation of co-occuring species is the reason for species diversity and the recent distribution.rn

Geomorphologische Untersuchungen im Land der tausend Hügel - oder: Wie europäisch ist die rwandische Landschaftsentwicklung?

Das ursprüngliche Ziel der vorliegenden Dissertation war die Untersuchung der Talgenese im Zentralen Hügelland Rwandas. Entstehung und Form der Täler, die Stratigraphie und das Alter der Hang- und Talsedimente sowie die wirkenden reliefgestaltenden Prozesse sind bei weitem nicht abschließend erforscht. Da Strukturen und Prozesse im Rahmen von Prozessresponssystemen in Wechselwirkung stehen, bietet die Untersuchung der Strukturen gleich zwei Möglichkeiten, sich den Prozessen zu nähern: Strukturen sind sowohl Verursacher als auch Indikatoren von Prozessen. Entsprechend der ursprünglichen Fragestellung sollten nach einer Beschreibung der gegenwärtigen Strukturen (morphographische Geomorphologie) die formbildenden Prozesse ergründet werden (funktionale Geomorphologie), um dann die Entwicklung der Strukturen und Prozesse unter Einbeziehung der relevanten Phasen der Erdgeschichte und des Paläoklimas zu rekonstruieren (genetische Geomorphologie). Im Verlauf der zu diesem Zweck durchgeführten geomorphologisch-stratigraphischen Untersuchungen in den Tälern der Region von Butare (Südrwanda) stellten sich aber die holozänen Hangdeckschichten und Talfüllungen als derart mächtig heraus, dass tiefer liegende Sedimente nicht erschlossen werden konnten. Die älteren Strukturen ließen sich daher nur unzureichend rekonstruieren und die eingangs formulierte Fragestellung konnte nicht wie erwartet bearbeitet werden. Angesichts der Mächtigkeit der Sedimente wurde offensichtlich, dass sowohl die spätpleistozäne als auch die holozäne Dimension der Sedimentbildung völlig unterschätzt wurde. Diese Beobachtungen warfen zwei grundlegende Fragen auf: einerseits die Frage warum die holozänen Sedimente so mächtig ausgebildet sind, und andererseits, weshalb ihre Mächtigkeit derartig unterschätzt wurde. Rasch stellte sich heraus, dass die Bearbeitung der ersten Frage eine interdisziplinäre Öffnung und die der zweiten Frage eine interkulturelle Öffnung der Fragestellung erforderte. Dabei stellen sich vor allem zwei Fragen: Zum einen, inwiefern der europäische Ursprung der Begriffe, Theorien und Modelle, die zur Beschreibung und Interpretation der rwandischen landschaftlichen und landschaftsgestaltenden Prozesse verwendet werden, eben jene Beschreibung und Interpretation beeinflusst, und zum anderen, ob und inwiefern auch naturwissenschaftliche Disziplinen in ihrem Umgang mit ‚natürlich gedachten’ Strukturen und Prozessen von diesen Konstruktionen betroffen sind. Ziel der Dekonstruktion der Begriffe, Theorien und Modelle ist kein ‚richtigerer’ oder ‚wahrhaftigerer’, sondern ein ‚bewussterer’ Umgang mit den Begriffen, Theorien und Modellen und dadurch eine bewusstere Rekonstruktion der Strukturen und Prozesse der Landschaften und Paläolandschaften des rwandischen Zentralen Hügellandes.rn

Die Schuldenkrise und die Unterstützung der Europäischen Union

Die Unterstützung der EU durch ihre Bürger ist spätestens seit dem Vertrag von Maastricht Gegenstand einer Vielzahl von Beiträgen in der Einstellungsforschung. Eine zentrale Annahme der bisherigen Forschung war die große Distanz der EU zur Alltagswirklichkeit der Bürger. Nach dieser werden Einstellungen zur EU nur aufwendig oder mit Rückgriff auf Einstellungen zum Nationalstaat gebildet. Mit der Euro-Schuldenkrise, deren wirtschaftlichen Auswirkungen für die Bürger und einer Vielzahl von EU-Krisengipfeln erfuhr die europäische Politik seit 2010 eine enorme Aufmerksamkeit in der Öffentlichkeit. In dieser Arbeit wird die Entwicklung der EU-Unterstützung vergleichend in Deutschland und Griechenland vor und während der Schuldenkrise untersucht: 1) Zunächst wird diskutiert, inwieweit die Schuldenkrise mit den etablierten Determinanten der Unterstützungsforschung theoretisch zusammenhängt. Im Mittelpunkt stehen wirtschaftliche und demokratische Performanz, europäische und nationale Identität sowie Heuristiken zum Nationalstaat. 2) Der Fokus auf Deutschland und Griechenland ermöglicht einen Vergleich der Determinanten vor und während der Krise, da beide Länder substanziell völlig unterschiedlich, jedoch gleichzeitig betroffen waren. Während die Bürger in Griechenland spürbare Wohlstandsverluste erleiden, stellt sich in Deutschland die Frage nach der Solidarität mit den europäischen Nachbarn. 3) Die empirische Analyse zeigt, dass die etablierten Determinanten in der Schuldenkrise ihre Relevanz behalten. Das individuelle wirtschaftliche Schicksal ist in Griechenland ein stärkerer Einflussfaktor als vor der Krise. Es bestätigt sich die Erwartung, dass die größere Präsenz der EU in der Krise mit einer geringeren Bedeutung der Einstellungen zum Nationalstaat einhergeht.