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Reprocessed deep seismic reflection profile DEKORP 1-Laacher See Experiment 8701 across the Laacher See Volcano, East Eifel, Germany

The deep seismic reflection survey DEKORP 1-Laacher See was conducted as additional measurements in the Laacher See area in 1987 as part of the DEKORP-1 project, one main traverse of the German continental seismic reflection program. This small survey was an attempt to reveal the 3-D crustal structure in an area of the Quaternary East Eifel Volcanism and possibly find some magma chambers in the crust with high-fold near-vertical incidence vibroseis acquisition (DEKORP Research Group, 1991). The measurement consists of a 8,64 km long, multifold 2D seismic line 8701 across the Laacher See in NE-SW direction and two pseudo-3D seismic areas 8702 north of the lake and 8703 beneath the lake with one-fold coverage in each case. Laacher See or Lake Laach is a caldera lake in the Rhineland-Palatinate, Germany, one of the volcanic centres of the East Eifel Volcanic Field. It belongs together with the West Eifel to the youngest volcanic areas in Central Europe. The caldera of the Laacher See was formed about 12 900 years ago after the volcano explosively erupted, and the remaining crust collapsed into the empty magma chamber below. The Laacher See is still considered to be an active volcano, proven by seismic activities and thermal anomalies under the lake. The first processing of the Laacher See data was carried out at the Geophysical Institute of the CAU University Kiel in 1990. Unfortunately, these results have not been preserved or published. According to DEKORP Research Group (1991) the first processing resulted in poor data quality caused by high scattering and attenuation in the volcanic material near the surface. This reflected energy was not enough to image a magma chamber beneath the lake or any other structures. Thus, information about the structure of the Earth’s crust of the Eifel is mainly based on the deep seismic reflexion profile DEKORP 1B, running ca. 25 km to the west from the Laacher See und crossing DEKORP 1A at its northern profile end. In recent years, deep low‐frequency (DLF) earthquakes have been detected in the Laacher See area indicating ongoing magmatic activity in the lower crust and upper mantle (Hensch et al., 2019, Dahm et al. 2020). These and other signatures suggested the reprocessing of the Laacher See data with modern methods. Thus, the 2D seismic line 8701 has been reprocessed in 2020 within the framework of the Master’s thesis by Agafonova (2020) written at the Technical University of Berlin and supervised by the GFZ Potsdam. All reprocessed data come in SEGY trace format, the final sections additionally in PNG or PDF graphic format: as raw FF-sorted unstacked data, as preprocessed CDP-/FF-sorted unstacked data as well as poststack-time/-depth unmigrated and migrated sections. Moreover, the results of the tomographic inversion are included. Detailed information about acquisition and reprocessing parameters of line 8701 can be found in the accompanying Technical Report (Agafonova & Stiller, 2021). The reprocessed results of the Laacher See survey 1987 can be of importance for better understanding the structure of the Eifel crust. Even though significant knowledge gaps and uncertainties exist due to the insufficient data quality, such important questions can already be discussed as: • How complex is the structure beneath the Laacher See? • Can the Mantle-Crust Boundary be defined at ca. 34 km depth? • Are the strongly inclined events in the Upper Crust between 1-5 km depth parts of caldera ring-faults? • Do the reflections between 5-7 km depth indicate boundaries of a possible magma chamber?

Reprocessed deep seismic reflection profile DEKORP 1990-3B/MVE (West) across the Rhenohercynian and Saxothuringian zone of the state of Hesse, Germany

The profile DEKORP 3B/MVE, consisting of the two segments West and East, was recorded in 1990 as part of the DEKORP project, the German deep seismic reflection program. The focus of the DEKORP project was on deep crustal and lithospheric structures and therefore originally not on structures at shallower depths. From today's perspective, however, this depth range is of great interest for a wide range of possible technical applications (including medium-depth and deep geothermal projects). The original data is published by Stiller et al. (2021). The westernmost 91 km of the 208 km long profile 3B (West) were reprocessed on behalf of the Hessian Agency of Nature Conservation, Environment and Geology (HLNUG). As a particularity, also a set of 18 cross-lines, each ca. 12 km in length and perpendicular to the main lines, were surveyed along DEKORP 3B/MVE to get information about possible cross-dips. Four of those short cross-lines were reprocessed in 2D as well. The focus of the reprocessing of the old data was on improving the resolution / mapping of geological structures down to a depth of 6 km (approx. 3 s TWT) to describe the prolongation of faults and geological structures in more detail than in previous studies. In order to achieve these goals and in view of the fact that today's processing and evaluation methods have been improved considerably compared to the 1990‘s, a state-of-the-art reprocessing was implemented. In comparison with the original processing (Stiller et al. (2021)), more sophisticated processing steps like CRS (Common Reflection Surface) instead of CDP (Common Depth Point) stacking, turning-ray tomography and prestack time and depth migration were carried out. The reprocessing results of the DEKORP 3B (West) survey comprise all datasets newly achieved in addition to the datasets from the original processing (Stiller et al. (2021)), i.e. (1) the migrated CRS image gathers as unstacked data, and (2) the pure CRS stack, the poststack-time as well as prestack-time and prestack-depth migrated sections as stacked data. Moreover, (3) all velocity models used for the different versions including (4) the separate first-break tomography inversion, are contained. Additionally, the results of the 2D-reprocessing of cross-lines Q21-Q24 are included. All reprocessed data come in SEGY trace format, the final sections additionally in PDF graphic format. A reprocessing report is included as well as again all meta information for each domain (source, receiver, CDP) like coordinates, elevations, locations and static corrections combined in ASCII-tables for geometry assignment purposes. The DEKORP 3 survey was a combined seismic survey investigating the Variscan structures of the Rhenohercynian and the Saxothuringian. Consisting of three seismic lines it starts in the Rhenohercynian Hessian Depression (DEKORP 3A), crosses the Saxothuringian Mid-German Crystalline High (DEKORP 3B/MVE (West)) and runs parallel to the northern margin of the Moldanubian (DEKORP 3B/MVE (East)). The 207.65 km long DEKORP 3B (West) profile trends NW-SE and intersects DEKORP 3A in the Tertiary volcanic field within the "Northern Phyllite Zone". It crosses the Hessian Depression of the Rhenohercynian, runs through the Rhön Tertiary volcanic province and the Mesozoic Franconian Basin to the Bohemian Massif. The line ends at the Franconian Line. The reprocessed datasets contain a sub-section of the entire 3B (West) profile with a total length of 90.8 km of full CDP coverage, covering the territory of the state of Hesse, i. e. from the profile’s starting point in the NW to the SE until the Rhön volcanic complex. The reprocessed part of 3B (West) is intersected by four short cross-lines along the profile at km 8.75, 32.6, 64.75, 84.35 and by DEKORP 3A at km 42.3. The DEKORP '90-3B profile is of particular interest to investigate the seismic resolution of the Hessian depression, the east-hessian Buntsandstein nappe as well as the tertiary volcanic fields of the Kellerwald and Rhön.

Reprocessed deep seismic reflection profile DEKORP 1990-3A (including cross-profiles Q12-Q16) across the Hessian Depression, Northwest Germany

The profile 3A was recorded in 1990 as part of the DEKORP project, the German deep seismic reflection program. The focus of the DEKORP project was on deep crustal and lithospheric structures and therefore originally not on structures at shallower depths. From today's perspective, however, this depth range is of great interest for a wide range of possible technical applications (including medium-depth and deep geothermal projects). The original data is published by Stiller et al. (2021). On behalf of the Hessian Agency of Nature Conservation, Environment and Geology (HLNUG). From the 128 km long profile 3A the southernmost 104 km (plus additional 9 km northwards with decreasing CDP coverage to avoid boundary effects during migration) were reprocessed. As a particularity, also a set of 6 cross-lines, each ca. 9.6 km in length and perpendicular to the main line, were surveyed along DEKORP 3A to get information about possible cross-dips. Five of those short cross-lines (Q12-Q16) were reprocessed in 2D and 3D as well. The focus of reprocessing of the old data was on improving the resolution / mapping of geological structures down to a depth of 6 km (approx. 3 s TWT) to describe the prolongation of faults and geological structures in more detail than in previous studies. In order to achieve these goals and in view of the fact that today's processing and evaluation methods have been improved considerably compared to the 1990‘s, a state-of-the-art reprocessing was implemented. In comparison with the original processing (Stiller et al. (2021)), more sophisticated processing steps like CRS (Common Reflection Surface) instead of CDP (Common Depth Point) stacking, turning-ray tomography and prestack time and depth migration were carried out. The reprocessing results of the DEKORP 3A survey comprise all datasets newly achieved in addition to the datasets from the original processing (Stiller et al. (2021)), i.e. (1) the migrated CRS image gathers as unstacked data, and (2) the pure CRS stack, the poststack-time as well as prestack-time and prestack-depth migrated sections as stacked data. Moreover, (3) all velocity models used for the different versions including (4) the separate first-break tomography inversion, are contained. Additionally, the results of the 2D- and 3D-reprocessing of cross-lines Q12-Q16 are included. All reprocessed data come in SEGY trace format, the final sections additionally in PDF graphic format. A reprocessing report is included as well as again all meta information for each domain (source, receiver, CDP) like coordinates, elevations, locations and static corrections combined in ASCII-tables for geometry assignment purposes. Detailed information about acquisition and reprocessing parameters can be found in the accompanying Technical Report (Stiller & Agafonova, 2022). The DEKORP 3 survey was a combined seismic survey investigating the Variscan structures of the Rhenohercynian and the Saxothuringian. Consisting of three seismic lines it starts in the Rhenohercynian Hessian Depression (DEKORP 3A), crosses the Saxothuringian Mid-German Crystalline High (DEKORP 3B/MVE (West)) and runs parallel to the northern margin of the Moldanubian (DEKORP 3B/MVE (East)). The 128 km long DEKORP 3A profile runs N-S within the Hessian Depression from the Solling Dome in the Rhenohercynian to the Vogelsberg Volcano of the Saxothuringian Mid-German Crystalline High. The middle part of the profile crosses the "Northern Phyllite Zone". The reprocessed datasets contain a sub-section of the entire profile with a total length of 104.1 km of full CDP coverage, covering the territory of the state of Hesse. The reprocessed part of 3A is intersected by five short cross-lines along the profile at km 31.75, 53.55, 73.75, 89.85, 109.85 and by DEKORP 3B/MVE (West) at km 120.75 at its southern end. The DEKORP '90-3A profile is of particular interest to investigate the seismic resolution of the crust beneath the Permo-Mesozoic to Tertiary Hessian depression, the Kassel graben structure, as well as the tertiary volcanic fields of the Reinhardswald, Habichtswald, Knüll, Söhrewald and stopping just north of the large Cenozoic Vogelsberg complex.

Deep seismic reflection profile DEKORP 1986-2N across the eastern Rhenish Massif and the Muensterland Basin, Northwest Germany

The profile 2N was recorded in 1986 as part of the DEKORP project, the German deep seismic reflection program. The seismic survey of the ca. 220 km long line 2N was conducted to investigate the deep crustal structure of the eastern Rhenish Massif and the Muensterland Basin with high-fold near-vertical incidence vibroseis acquisition. The objectives of the survey were to image the Variscan structures in detail with respect to their specific transitions, 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 line contributed to the International Lithosphere Program (ILP) and the former European Geotraverse (EGT). The first outcomes of the survey were presented by Reichert (1988). A detailed description of seismic results is provided by Franke et al. (1990) as well as by DEKORP Research Group (1990) and supplemented by many other researches. The Technical Report of line 2N 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 nearly S-N striking DEKORP 2N line reveals an almost complete cross-section through the Rhenohercynian Zone. The profile runs from the Taunus Mountains, i.e. the southeastern rim of the Rhenish Massif over the Lahn-Dill Trough, through the Ebbe Mountains to the borehole Muensterland 1 in the Muensterland Basin, which belongs to the sub-Variscan Foredeep. The profile is the northern prolongation of DEKORP 2S. Line DEKORP 2Q crosses line 2N perpendicularly in its northern part extending northeastwards to the borehole Versmold 1.

Deep seismic reflection profile DEKORP 1990-3B/MVE (West) from the Kellerwald to the Bohemian Massif, West Germany

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).

Deep seismic reflection profile DEKORP 1987-1A across the western Rhenish Massif, West Germany/ East Belgium

The c. 93 km long profile 1A was recorded in 1987 as part of the joint seismic reflection venture DEKORP 1 of the DEKORP (German Deep Seismic Reflection Program) and BELCORP (Belgian Continental Reflection Seismic Program) project steering 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 1A 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 nearly NW-SE running survey 1A starts at the Dutch-Belgian border southeast of Maastricht on the southern flank of the London-Brabant Massif. The seismic line also crosses the northern rim of the Rhenish Massif passing through the Aachen Thrust, a part of the North Variscan Deformation Front. 1A runs over the Stavelot-Venn Anticline into the Northern Eifel intersecting the N-S trending axial depression of the Eifel North-South Zone nearly perpendicularly to its strike direction. The eastern flank of the depression was affected by volcanic activity of the High Eifel Volcanic Field during Early Tertiary times (DEKORP Research Group, 1991). Near Adenau the southern end of line 1A crosses the northern beginning of line DEKORP 1B, which proceeds through the Kelberg Magnetic High farther to the south.

Deep seismic reflection profile DEKORP 1984-2S across the Franconian Platform, South Germany

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.

Deep seismic reflection profile DEKORP 1990-3A across the Hessian Depression, Northwest Germany

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.

Deep seismic reflection profile DEKORP 1987-1B across the western Rhenish Massif, West Germany

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.

Deep seismic reflection profile DEKORP 1988-1C across the western Rhenish Massif, West Germany

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.

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