Beschreibung: The Baffin Bay between Greenland and Baffin Island (Canada) opened during the separation of Greenland and Canada in the Palaeocene and Eocene. The Melville Bay is situated in its northeastern part. The crustal composition of Northern and Southern Baffin Bay has been studied in detail: Southern Baffin Bay is underlain by oceanic crust with volcanic margins, while the margins of northern Baffin Bay are characterized by serpentinized mantle material. In contrast, the nature of crust in the deep, central Baffin Bay and the Melville Bay was still unclear due to a lack of deep seismic sounding lines. In 2010 a joint geophysical experiment in the Greenlandic part of Baffin Bay acquired seismic, magnetic and gravity data. We present three velocity and density models derived from seismic refraction and gravity data. Two of the three profiles are located within the Melville Bay and extend in a SW - NE direction from the deep sea area of central Baffin Bay to the shelf area of the Melville Bay. The third profile crosses the northern profile in the Melville Bay and extends in a N - S direction into the Northern Baffin Bay. The profiles in the Melville Bay can be divided in three crustal sections. The deep-sea area reveals a 3.5 - 7 km thick, 2-layered oceanic crust with increasing thickness towards the shelf and up to 6 km thick sediments. The crust is underlain by serpentinized upper mantle with velocities of 7.6 - 7.8 kms-1. A transition zone, which is affected by volcanism, connects the oceanic crust with stretched continental crust underneath the Melville Bay. Basement highs and deep sediment basins characterize the stretched and rifted continental crust. The Melville Bay Graben, the deepest rift basin in Melville Bay, contains up to 10 km thick, possibly metamorphosed sediments with unusually high velocities of up to 4.9 kms 1. Well-constrained reflections of the crust-mantle boundary can be found in many seismic sections indicating a maximum crustal thickness of ~ 26 km in the northern profile and ~ 32 km in the southern profile. In the southern part of the third, N-S extending profile, a 2-layered oceanic crust is covered by up to 5 km thick sediments. Underneath the shelf edge, the crust thickens towards the north in several steps and reaches a maximum thickness of ~ 40 km. The northern part of the profile is characterized by faulted end eroded basement, which crops out at the seafloor.

Beschreibung: Davis Strait is a bathymetric high, located between Canada and Greenland. With a water depth of only 500 m, it acts as a gateway for the exchange of polar water from Baffin Bay in the north to the Labrador Sea and the Atlantic in the south. The Davis Strait region has undergone a complex tectonic evolution and the nature of crust is disputed. In a first stage the strait was characterized by extension due to the separation of the North American plate and Greenland. In a second stage transpression was the dominating force. The most prominent geologic feature is the Ungava Fault Complex, a major transform fault that cuts Davis Strait. To investigate the role of Davis Strait as a polar gateway during the opening of the Labrador Sea and Baffin Bay rift system, we analyse recent seismic reflection and refraction data in combination with potential field data. This information is incorporated into a plate tectonic model. On a 230-km-long east west line in central Davis Strait, a P-wave velocity and a density model were obtained by forward modelling. The models show several blocks of continental crust that are separated by major faults of the Ungava Fault Complex. High velocities in the lower crust indicate intense intrusions of mafic material, which we relate to the arrival of the Iceland mantle plume beneath Greenland in the Paleocene. Seismic reflection data were used to model the complex basement morphology and to develop a sediment stratigraphy. The tectonic modelling reveals that an overlap of 70 km of stretched continental crust needs to be compensated for in the transpressional stage of Davis Strait. We are now working on displaying the evolution of Davis Strait from the initial opening of the Labrador Sea to today and will present new results of this study.