Description: The Davis Strait is located between Canada and Greenland and connects the Labrador Sea and the Baffin Bay basins. Both basins formed in Cretaceous to Eocene time and were connected by a transform fault system in the Davis Strait. Whether the crust in the central Davis Strait is oceanic or continental has been disputed. This information is needed to understand the evolution of this transform margin during the separation of the North American plate and Greenland. We here present a 315-km-long east–west-oriented profile that crosses the Davis Strait and two major transform fault systems—the Ungava Fault Complex and the Hudson Fracture Zone. By forward modelling of data from 12 ocean bottom seismographs, we develop a P -wave velocity model. We compare this model with a density model from ship-borne gravity data. Seismic reflection and magnetic anomaly data support and complement the interpretation. Most of the crust is covered by basalt flows that indicate extensive volcanism in the Davis Strait. While the upper crust is uniform, the middle and lower crust are characterized by higher P -wave velocities and densities at the location of the Ungava Fault Complex. Here, P -wave velocities of the middle crust are 6.6 km s –1 and of the lower crust are 7.1 km s –1 compared to 6.3 and 6.8 km s –1 outside this area; densities are 2850 and 3050 kg m –3 compared to 2800 and 2900 kg m –3 . We here interpret a 45-km-long section as stretched and intruded crust or as new igneous crust that correlates with oceanic crust in the southern Davis Strait. A high-velocity lower crust (6.9–7.3 km s –1 ) indicates a high content of mafic material. This mantle-derived material gradually intruded the lower crust of the adjacent continental crust and can be related to the Iceland mantle plume. With plate kinematic modelling, we can demonstrate the importance of two transform fault systems in the Davis Strait: the Ungava Fault Complex with transpression and the Hudson Fracture Zone with pure strike-slip motion. We show that with recent poles of rotation, most of the relative motion between the North American plate and Greenland took place along the Hudson Fracture Zone.

Description: Über die Labrador See und Baffin Bay wird zwischen Grönland und Kanada Flachwasser zwischen dem Arktischen Ozean und dem Atlantik ausgetauscht. Dieser Energietransport beeinflusst die klimatischen Bedingungen dieser Region wesentlich, so dass die wenig untersuchte tektonische Öffnung dieser Becken für das Paläoklima von besonderem Interesse ist. Hier werden Ergebnisse eines refraktionsseismischen Profils mit 24 Ozeanbodenseismometern des Fahrtabschnittes MSM09/3 mit der Maria S. Merian vorgestellt, das sich über 470 km von der Baffin Insel im SSW nach Grönland im NNO erstreckt und die vermutete Position einer Spreizungszone kreuzt. Auffällig ist eine Verdickung der Kruste westlich der vermuteten Spreizungszone, die durch eine negative Schwereanomalie bestätigt wird. Nordöstlich zeigt sich eine komplexe Struktur, die mit einer positiven Schwereanomalie zusammenfällt und auf Intrusionen mafischer Körper hinweist. Die anschließende grönländische Seite des Spreizungsbeckens ist weitgehend homogen mit dem typischen Aufbau ozeanischer Kruste, während sich auf kanadischer Seite ein komplexer struktureller Aufbau zeigt. Wir vermuten, dass die Komplexität mit wiederholten mafischen Intrusionen und/oder Scherzonen in Verbindung steht.

Description: The continental margin of Mozambique formed during the initial dispersal of Gondwana about 180 Ma. Due to the lack of deep seismic and dense potential field data, many details of the timing and geometry of the early breakup in this region remained unknown to date. To close this gap, a research project (MoBaMaSis (“Mozambique Basin Marine Seismic Survey”) with the French research vessel R/V Marion Dufresne II was conducted in 2007. This paper presents the results of P-wave, magnetic and 2D-gravity modelling along two parallel seismic refraction profiles between 37° and 41° E, crossing the Mozambique rifted margin. The crust shows the characteristics of normal to slightly thickened oceanic crust. A lower crustal highvelocity- body with P-wave-velocities of 7.0–7.5 km/s is observed along both profiles. Its origin is discussed in the context of upper mantle convection and thermal properties. The existing magnetic anomaly identifications have been extended to older ages. We postulate that the oldest oceanic crust near the Central Mozambique continental margin has been formed around M41n (166 Ma). Closer to the coast a pronounced negative magnetic anomaly exists that we interpret to coincide with the continent–ocean-transition. This implies that the position of the continent–ocean-transition is located significantly closer to the shoreline than proposed before.

Description: Baffin Bay is an Arctic basin between Canada and Greenland, connected via Davis Strait with the Labrador Sea in the south. Due to its shallow water depth of only 500 m, Davis Strait acts as a gateway for the Arctic water exchange between Baffin Bay and the Atlantic. The nature of Baffin Bay and Davis Strait crust has long been a subject of debate. Either oceanic or stretched continental crust have been proposed by different authors from sonobuoy readings, seismic reflection and potential field data. We here present the new results of two seismic refraction lines acquired with ocean bottom seismometers. P-wave velocity models for both lines are constrained and complemented by density models, seismic reflection and magnetic anomaly data. Line AWI-20080500/AWI-20100400, in southern Baffin Bay, is oriented across a proposed Eocene spreading centre. This line confirms the existence of oceanic crust in southern Baffin Bay and allows for a regional mapping of the oceanic crust. With a plate kinematic model we depict the evolution of this basin and can distinguish between Palaeocene and Eocene oceanic crust. Line AWI-20080700 in Davis Strait crosses the Ungava Fault Complex, a major transform fault, where extension was followed by a stage of transpression. We here find deformed blocks of continental crust that are separated by transform faults of the Ungava Fault Complex. Between these blocks a region of 50 km is characterized by high P-wave velocities and a thin crust that we interpret as stretched and highly intruded crust. Tectonic modelling depicts a great lateral movement of 310 km of the continental blocks along the Ungava Fault complex. The compressional component is visible in a 70 km wide overlap of crust that had to be compensated by deformation of the blocks. With our new models and the compilation of published Moho depth and seismic stratigraphy we try to estimate the paleo bathymetry and the role of Davis Strait as a polar gateway.

Description: Der Wasserspiegel des Toten Meeres sinkt rapide um durchschnittlich einen Meter pro Jahr. Dadurch hat der Salzsee bereits ein Drittel seiner Oberfläche verloren. Dies hat u. a. dramatische Auswirkungen auf die einzigartige Ökologie. Entlang der ausgedörrten Ufer bilden sich täglich neue so genannte Erdfälle oder Sinkholes, die bis zu 20 Meter tief sind. Gut 1000 dieser plötzlich einfallenden Sinkholes haben sich inzwischen an der Küstenlinie des Toten Meeres gebildet. Während der Messkampagne zum Dead Sea Integrated Research Project (DESIRE) 2007 wurde das Küstengebiet südlich von Ein Gedi zusätzlich mit einem Laser Mirror Scanner der Firma RIEGL beflogen, um entsprechende Sinkholes zu detektieren. Das Gebiet besitzt eine Ausdehnung von etwa 20 mal 4 km. Die Datenakquirierung erfolgte durch Befliegung in Nord-Süd-Richtung in 20 Streifen und einer Überdeckung von 50%. Für die Auswertung stand die Software TopPIT der Firma Trimble Geospatial zur Verfügung. Ziel der Befliegung ist neben der Berechnung eines Digitales Geländemodells (DGM) die Schaffung einer Bestandsaufnahme bestehender Sinkholes, durch die Veränderungen im Vergleich mit zukünftigen Aufnahmen aufgedeckt werden können. Zudem soll die Leistungsfähigkeit der eingesetzten Messmethode als geeignetes Verfahren nachgewiesen werden.

Description: The Dead Sea Transform (DST) is a system of left-lateral strike-slip faults that accommodates the relative motion between the African and Arabian plates. Furthermore the water level of the Dead Sea is sinking rapidly at an average of one meter per year. Because of this the salt lake has already lost one third of its surface and along the parched shores are formed daily new sinkholes that are up to 20 meters deep. About 1000 of these sudden incident sinkholes have formed in the meanwhile the shoreline of the Dead Sea. They represent danger both to life and property, disrupt life in the area, and aversely affect building and development. During the measurement campaign for the Dead Sea Integrated Research Project (DESIRE) 2007 the coastal area was flown to the south of En Gedi also with a laser mirror scanner constructed by RIEGL to detect relevant sinkholes. The airborne survey area covers a surface of approximately 20 by 4 km. The data acquisition was done by flights in North-South direction in 20 strips with an overlap of 50 percent. For the data analysis focused on the software TopPIT of Trimble Geospatial was used. The aim of the airborne survey was the calculation of a digital terrain model (DTM) but also the creation of an inventory of existing sinkholes, that can be used to detect temporal changes by comparison with future recordings. Moreover, the efficiency of the method used should be demonstrated as an appropriate procedure compared with traditional field data collection.