ALBERT

Description: New marine geophysical data acquired across the partly ice-covered northern East Greenland continental margin highlight a complex interaction between tectonic and magmatic events. Breakup-related lava flows are imaged in reflection seismic data as seaward dipping reflectors, which are found to decrease in size both northward and southward from a central point at 75°N. We provide evidence that the magnetic anomaly pattern in the shelf area is related to volcanic phases and not to the presence of oceanic crust. The remnant magnetization of the individual lava flows is used to deduce a relative timing of the emplacement of the volcanic wedges. We find that the seaward dipping reflectors have been emplaced over a period of 2–4 Ma progressively from north to south and from landward to seaward. The new data indicate a major post-middle Eocene magmatic phase around the landward termination of the West Jan Mayen Fracture Zone. This post-40-Ma volcanism likely was associated with the progressive separation of the Jan Mayen microcontinent from East Greenland. The breakup of the Greenland Sea started at several isolated seafloor spreading cells whose location was controlled by rift structures and led to the present-day segmentation of the margin. The original rift basins were subsequently connected by steady-state seafloor spreading that propagated southward, from the Greenland Fracture Zone to the Jan Mayen Fracture Zone.

Description: The electrical conductivity of the seafloor derived from marine controlled source electromagnetic (CSEM) data can be related to the gas hydrate concentration and distribution within the stability zone, and can provide valuable information for resource assessment. Gas hydrates are electrically resistive in contrast to the conductive pore fluid and may significantly increase the bulk resistivity where they occur in sufficient quantities. The marine electromagnetic group at BGR has developed a new, seafloor-towed, electrical multi-receiver system that consists of a transmitting dipole and four receiving dipoles at increasing offsets, sensitive to depths relevant for gas hydrate evaluation from the seafloor to some hundred meters below. The system was successfully deployed on a test cruise on RV Poseidon in water depth of 1335 m over known gas hydrate targets in the Danube Delta, and in shallow water on the upper rim of the Danube Canyon. Inversion of the data reveals highly anomalous resistivity which at least for the deep water deployment can be explained with a combination of fresh pore water and the presence of gas hydrates in the sediments.

Description: Halotectonic pulses in the Bays of Mecklenburg and Kiel including the Glückstadt Graben have been previously explained by reactive and passive diapirism or differential load, e.g., caused by sub-salt faulting. Salt walls that formed above those sub-salt faults further grew during phases of inversion. Consequently, phases of enhanced halotectonics have been mainly related to the Triassic W-E extension, Jurassic North Sea doming, the Alpine orogeny. The location of salt walls was attributed to deep rooted sub-salt faults. Alternative concepts of salt tectonics have been developed for continental slopes. Salt deformation may start already during the precipitation of the salt due to basin floor tilt, which may result from thermo-tectonic subsidence or from the salt load. As the consequence the emerging salt layer creeps towards the basin center causing internal folding and thrusting (“gravity gliding”). The resulting thickness variations of the salt are considered to be significant enough that sedimentation in the depressions directly initiate differential load and passive diapirism. Extensional faulting in the basin margin and diapirism in the central basin continues if basin subsidence continues or if basin margin sedimentation causes differential load on the salt rim (“gravity spreading”). In the course of RV MARIA S. MERIAN expedition MSM52 (BalTec) in March 2016 we imaged the tectonic conditions within the Paleozoic to recent sedimentary strata of the southern Baltic Sea between the North German Basin across the Tornquist Fan with yet unparalleled vertical resolution. The equipment consisted of 8 GI-Guns (70 Hz dominant frequency) as a source array and a digital seismic streamer of 2700 m active length. Due to the short initial offset of 37 meters between the seismic source array and the first active streamer section the data image without gap the subsurface geology from the Paleozoic strata or basement up to the seafloor. A SW-NE striking seismic profiles from the central Mecklenburg Bay to the Skurup Block covers the northeastern North German Basin and its marginal setting where several fault systems are present. The Agricola fault system is a set of arcuate faults in the Post-Permian strata which emerged above along the pinch-out line of the mobile salt. Faults reach partly up to the seafloor suggesting recent displacement. Fault planes dip mainly towards the basin. These faults can well be understood as the consequence of salt gliding towards the basin center, hence, as the consequence of gravity gliding. The Werre and Prerow fault systems evolved above a salt anticline on top of the Grimmen High. A first major halotectonic pulse is suggested for the upper Triassic which led to salt depletion and enhanced deposition. During the Cretaceous inversion of the Grimmen High, a salt pillow emerged between both fault systems when the salt moved towards northeast and southwest. The absence of significant fault displacements beneath the salt pillows in the Mecklenburg bay is further consistent with the gravity gliding concept which explains salt pillow growth by thin-skinned shortening.

Description: The article focuses on the status of the research after the second project year. In addition to the basic characterisation of the chosen reference material mixture for sanitary slip casting, as presented in previous publications for the Geotechnologien Science Reports, it focuses especially on the characterisation results of the basic raw material components, which in the second year of the project were investigated. These are the basis for the funtional characterisation of novel body concepts and reference systems for the experimental validation of the simulation model. The development of first body concepts, derived from the mineralogical characterisation of the raw materials, is supported using a principal FMEA-based assesment of influences on the functional behaviour of the body as casting slip. Parameter analysis and statistical design of experiment techniques are being implemented to experimentally evaluate basic mineralogical influences within the context of a slip composition including differerent additive contributions. Significant interactions have to be specified and and to parameters effects ranked for further development. These insights will be the basis for laboratory pilot scale tests, which will in the next project phase focus on identifying and validating processing parameter influences. The characterisation results have furthermore been used to develop simplified reference systems for the experimental validation of the simulation. After a short standstill in the modell development, caused by the relocation of the simulation expertise provided by CME from RWTH Aachen to the Materials and Process Simulation Group in Bayreuth, the results are being transferred into a binary, up to ternary model approach, based upon a simplified composition and particle system. The simplification, performed in varying degrees, is based on the translation of the identified mineralogy of the components into particle systems with particle size and ratio aspects, charge specifications of identified surfaces and surface potential effects in different settings and environments. As the experimental validation is ambiguous due to the limitations of the experimental techniques for the basic systems, recommended literature as well as first approach validation experiments are used to generate basic input. The status of the development of the hybrid model algorithm, first implementation of parameter settings so far, resulting input requirements and the next steps to be taken are discussed. In this regard the importance of the working procedure for rheological slip characterisation, developed within the project for functional characterisation of the systems is highlighted.

Description: Previous geophysical measurements found several methane seep sites and wide-spread bottom simulating reflectors along the Hikurangi Margin in New Zealand. To study the variability of methane seepage and the distribution of gas hydrate filled sediments, marine controlled source electromagnetic (CSEM) data were collected over a number of known seep sites on Opouawe Bank as part of the multidisciplinary NEMESYS project. The CSEM data were inverted to give one-dimensional layered and laterally continuous two- dimensional electrical resistivity models, which revealed anomalously high resistivities (3-100 m) coincident with several seep sites, namely North Tower, South Tower, Piwakawaka, Pukeko and Riroriro. The resistivity anomalies are located in the top 200 mbsf with lateral extents of 500-1000 m. These results are also consistent with three-dimensional forward modeling studies. A possible explanation for the high resistivities is the presence of resistive gas hydrates beneath the seep sites, although the presence of free gas and carbonate crust cannot be completely ruled out. To explain the observed resistivity anomalies, gas hydrate fractions of 31-40% are required. In contrast, Takahe seep site is characterized by only a narrow channel (200 m) of moderately elevated resistivities (5 m), which can be explained by gas hydrate fractions of ~20%.