ALBERT

Description: The Quaternary volcanic fields of the Eifel (Rhineland‐Palatinate, Germany) had their last eruptions less than 13,000 years ago. Recently, deep low‐frequency (DLF) earthquakes were detected beneath one of the volcanic fields showing evidence of ongoing magmatic activity in the lower crust and upper mantle. In this work, seismic wide‐ and steep‐angle experiments from 1978/79 and 1987/88 are compiled, partially reprocessed and interpreted, together with other data to better determine the location, size, shape and state of magmatic reservoirs in the Eifel region near the crust‐mantle boundary. We discuss seismic evidence for a low‐velocity gradient layer from 30‐36 km depth, which has developed over a large region under all Quaternary volcanic fields of the Rhenish Massif and can be explained by the presence of partial melts. We show that the DLF earthquakes connect the postulated upper mantle reservoir with the upper crust at a depth of about 8 km, directly below one of the youngest phonolitic volcanic centers in the Eifel, where CO2 originating from the mantle is massively outgassing. A bright spot in the West Eifel between 6‐10 km depth represents a Tertiary magma reservoir and is seen as a model for a differentiated reservoir beneath the young phonolitic center today. We find that the distribution of volcanic fields is controlled by the Variscan lithospheric structures and terrane boundaries as a whole, which is reflected by an offset of the Moho depth, a wedge‐shaped transparent zone in the lower crust and the system of thrusts over about 120 km length.

Description: At the geothermal test site near Groß Schönebeck (NE German Basin), a new 3D seismic reflection survey was conducted to study geothermal target layers at around 4 km depth and 150°C. We present a workflow for seismic facies classification and modelling which is applied to a prospective sandstone horizon within the Rotliegend formation. Signal attributes are calculated along the horizon using the continuous Morlet wavelet transform. We use a short mother wavelet to allow for the temporal resolution of the relatively short reflection signals to be analysed. Time‐frequency domain data patterns form the input of a neural network clustering using self‐organizing maps. Neural model patterns are adopted during iterative learning to simulate the information inherent in the input data. After training we determine a gradient function across the self‐organizing maps and apply an image processing technique called watershed segmentation. The result is a pattern clustering based on similarities in wavelet transform characteristics. Three different types of wavelet transform patterns were found for the sandstone horizon. We apply seismic waveform modelling to improve the understanding of the classification results. The modelling tests indicate that thickness variations have a much stronger influence on the wavelet transform response of the sandstone horizon compared with reasonable variations of seismic attenuation. In our interpretation, the assumed thickness variations could be a result of variable paleo‐topography during deposition of predominantly fluvial sediments. A distinct seismic facies distribution is interpreted as a system of thicker paleo‐channels deposited within a deepened landscape. The results provide constraints for the ongoing development of the geothermal test site.

Description: The 208 km long profile 3B/MVE (West) was recorded in 1990 as part of the joint seismic reflection venture DEKORP 1990-3/MVE (Muenchberg-Vogtland-Erzgebirge) between the two former German Republics shortly before their unification. The aim of DEKORP 1990-3/MVE was to explore the structure of the crust from the Rhenish Shield through the Bohemian Massif to the Ore Mountains. The entire profile consists of DEKORP 3A, DEKORP 3B/MVE (West) and its prolongation to the east DEKORP 3B/MVE (East). Its total length amounts to about 600 km. 24 short seismic cross lines and associated 3D blocks with single fold coverage were also recorded. The seismic survey of 3B/MVE (West) was performed to investigate the deep crustal structure and the transition zone between the Rhenohercynian and Saxothuringian units with high-fold near-vertical incidence vibroseis acquisition. The results were compared with the results from the surveys DEKORP 1 and DEKORP 2, running nearly parallel to the line 3B/MVE (West). Details of the 3B/MVE (West) experiment, its preliminary results and interpretations may be obtained from DEKORP Research Group (A) et al. (1994) and DEKORP Research Group (C) et al. (1994). The Technical Report of line 3B/MVE (West) gives complete information about acquisition and processing parameters. The European Variscides, extending from the French Central Massif to the East European Platform, originated during the collision between Gondwana and Baltica in the Late Palaeozoic. Due to involvement of various crustal blocks in the orogenesis, the mountain belt is subdivided into distinct zones. The external fold-and-thrust belts of the Rhenohercynian and Saxothuringian as well as the predominantly crystalline body of the Moldanubian dominate the central European segment of the Variscides. Polyphase tectonic deformation, magmatism and metamorphic processes led to a complex interlinking between the units. The mainly NW-SE running DEKORP 3B/MVE (West) runs perpendicular to the Variscan strike direction and traverses the southern part of the Rhenohercynian unit with the Northern Phyllite Zone and the northern part of the Saxothuringian unit including the Mid-German Crystalline High. Starting in the Kellerwald the profile crosses the Hessian Depression, the Tertiary volcanic Rhoen Mountains and the Mesozoic of the Franconian Basin (DEKORP Research Group (C) et al., 1994). East of Staffelstein the profile turns to the east and ends on the Franconian Line, the southwestern boundary fault zone of the Bohemian Massif. The line 3B/MVE (West) is intersected by ten cross lines along the profile and by DEKORP 3A at its northwestern end. To the east the profile is extended by DEKORP 3B/MVE (East).

Description: The profile 1C was recorded in 1988 as part of the joint reflection venture DEKORP 1 of DEKORP (German Deep Seismic Reflection Program) and BELCORP (Belgian Continental Reflection Seismic Program) groups. The seismic survey of the ca. 75-km long line 1C was conducted to investigate the deep crustal structure of the western Rhenish Massif with high-fold near-vertical incidence vibroseis acquisition. The objectives of the experiment were to analyse deep Variscan and post-Variscan crustal structures in the region and to compare them with the results from the eastern Rhenish Massif gathered from the survey DEKORP 2N. The first results were presented by DEKORP Research Group (1991) and supplemented by many other researches. The Technical Report of line 1C gives detailed information about acquisition and processing parameters. The European Variscides, extending from the French Central Massif to the East European Platform, originated during the collision between Gondwana and Baltica in the Late Palaeozoic. Due to involvement of various crustal blocks in the orogenesis, the mountain belt is subdivided into distinct zones. The external fold-and-thrust belts of the Rhenohercynian and Saxothuringian as well as the predominantly crystalline body of the Moldanubian dominate the central European segment of the Variscides. Polyphase tectonic deformation, magmatism and metamorphic processes led to a complex interlinking between the units. The Rhenohercynian Zone is a foreland fold-and-thrust belt cropping out in the Rhenish Massif which extends from the Ardennes to the Harz Mountains. This geological unit consists predominantly of Devonian and Lower Carboniferous rocks affected by very low-grade metamorphism (DEKORP Research Group, 1991). The survey 1C was carried out in the western part of the Rhenish Massif and intersects the Variscan main structures almost perpendicular. It stretches from the Mosel Syncline to the Saar-Nahe Basin (WNW-ESE) crossing the Devonian metamorphic rocks of the Hunsrueck Mountains, the Northern Phyllite Zone and the Hunsrueck Boundary Fault separating the Rhenohercynian and Saxothuringian Zones. In the northwest 1C joins line 1B which runs through the Hocheifel area. In the southeast the line continues with 9N running across the northern part of the Upper Rhine Graben.

Description: The 50 km long profile 1B was recorded in 1987 as part of the joint reflection venture DEKORP 1 of DEKORP (German Deep Seismic Reflection Program) and BELCORP (Belgian Continental Reflection Seismic Program) groups. It was surveyed to investigate the deep crustal structure of the western Rhenish Massif with high-fold near-vertical incidence vibroseis acquisition. The objectives of the experiment were to analyse deep Variscan and post-Variscan crustal structures in the region and to compare them with the results from the eastern Rhenish Massif gathered from the survey DEKORP 2N. The first results were presented by DEKORP Research Group (1990, 1991) and supplemented by many other researches. The Technical Report of line 1B gives detailed information about acquisition and processing parameters. The European Variscides, extending from the French Central Massif to the East European Platform, originated during the collision between Gondwana and Baltica in the Late Palaeozoic. Due to involvement of various crustal blocks in the orogenesis, the mountain belt is subdivided into distinct zones. The external fold-and-thrust belts of the Rhenohercynian and Saxothuringian as well as the predominantly crystalline body of the Moldanubian dominate the central European segment of the Variscides. Polyphase tectonic deformation, magmatism and metamorphic processes led to a complex interlinking between the units. The Rhenohercynian Zone is a foreland fold-and-thrust belt cropping out in the Rhenish Massif which extends from the Ardennes to the Harz Mountains. This geological unit consists predominantly of Devonian and Lower Carboniferous rocks affected by very low-grade metamorphism (DEKORP Research Group, 1991). The survey 1B was carried out in the western part of the Rhenish Massif and trends nearly N-S starting in the western volcanic zone of the Eifel, the Tertiary Hoch Eifel Volcanic Field represented by alkali basalts and fractionated volcanics. The line also runs over a positiv magnetic anomaly, the Kelberg Magnetic High which is located on the southern flank of the East Eifel Main Anticline. Afterwards, 1B crosses the SE-dipping Siegen Main Thrust and ends in the Mosel Syncline, the northern border of the Hunsrueck Mountains (DEKORP Research Group, 1991). The profile joins line 1A in the north and continues to the southeast with line 1C.

Description: The 128 km long profile 3A was recorded in 1990 as part of the joint seismic reflection venture DEKORP 1990-3/MVE (Muenchberg-Vogtland-Erzgebirge) between the two former German Republics shortly before their unification. The aim of DEKORP 1990-3/MVE was to explore the structure of the crust from the Rhenish Shield through the Bohemian Massif to the Ore Mountains. The entire profile consists of DEKORP 3A, DEKORP 3B/MVE (West) and its prolongation to the east DEKORP 3B/MVE (East). Its total length amounts to about 600 km. 24 short cross lines and associated 3D blocks with single fold coverage were also recorded. The seismic survey of 3A was conducted to investigate the deep crustal structure of the Hessian Depression with high-fold near-vertical incidence vibroseis acquisition, and thus to connect DEKORP 3B/MVE (West) to oil industry seismic profiles in the Leinegraben area. Details of the experiment, preliminary results and interpretations may be obtained from DEKORP Research Group (A) et al. (1994) and DEKORP Research Group (C) et al. (1994). The Technical Report of line 3A gives complete information about acquisition and processing parameters. The European Variscides, extending from the French Central Massif to the East European Platform, originated during the collision between Gondwana and Baltica in the Late Palaeozoic. Due to involvement of various crustal blocks in the orogenesis, the mountain belt is subdivided into distinct zones. The external fold-and-thrust belts of the Rhenohercynian and Saxothuringian as well as the predominantly crystalline body of the Moldanubian dominate the central European segment of the Variscides. Polyphase tectonic deformation, magmatism and metamorphic processes led to a complex interlinking between the units. The N-S trending DEKORP 3A line aimed at a seismic characterisation of the crust beneath the Permo-Mesozoic to Tertiary Hessian Depression. Running from the Solling Dome in the Rhenohercynian through the Kassel Graben and the late Tertiary volcanic fields of the Reinhardswald and Soehrewald, the 3A line ends in the Northern Phyllite Zone north of the Vogelsberg Volcano, the largest of the Cenozoic volcanoes in Europe (DEKORP Research Group (C) et al., 1994). DEKORP 3A is intersected by six short cross lines along the profile and by DEKORP 3B/MVE (West) at its southern end.

Description: DEKORP 2S was the first profile carried out in 1984 as part of the DEKORP project, the German deep seismic reflection program. The seismic line has a length of 250 km and was the first and only DEKORP line to be acquired using explosives as source energy. The objectives of the experiment were to explore the deep crustal structure of the Saxothuringian Zone and of its transitions into the adjacent Moldanubian and Rhenohercynian Zones of the Variscan Belt, to obtain evidence about vertical tectonic processes during the Variscan orogenesis, to understand the causes of observed gravity and magnetic anomalies and to recognize and define the Variscan front to the north. In addition, the survey contributed to the International Lithosphere Program (ILP) and the former European Geotraverse (EGT). Details of the experiment, preliminary results and interpretations may be obtained from DEKORP Research Group (1985) or Meissner et al. (1987). The Technical Report of line 2S gives complete information about acquisition and processing parameters. The European Variscides, extending from the French Central Massif to the East European Platform, originated during the collision between Gondwana and Baltica in the Late Palaeozoic. Due to involvement of various crustal blocks in the orogenesis, the mountain belt is subdivided into distinct zones. The external fold-and-thrust belts of the Rhenohercynian and Saxothuringian as well as the predominantly crystalline body of the Moldanubian dominate the central European segment of the Variscides. Polyphase tectonic deformation, magmatism and metamorphic processes led to a complex interlinking between the units. The SE-NW striking DEKORP 2S line runs perpendicular to the Variscan strike direction and crosses the tectonic boundaries between the Moldanubian, Saxothuringian and Rhenohercynian units, which are predominantly covered by Permian and younger sediments (DEKORP Research Group, 1985). Extending from the Danube river to the Taunus Mountains line 2S crosses the Franconian Platform passing through the Noerdlinger Ries, where the impact excavated crystalline basement slivers of the Moldanubian zone, the Spessart Mountains, a part of the Mid German Crystalline High and the NE trending Hessian Through (DEKORP Research Group, 1985). Ending beyond the northeast branch of the Rhine Graben within the Taunus Mountains the profile is extended by line 2N to the northwest.