State of Geomorphological Research in 2012 Field Trip Guide

Home , Bohemian Massif, Fichtel Mountains

State of geomorphological research in 2012

18 – 20th April 2012, Sokolov

Field trip guide

Štěpančíková P., Peterek A., Marek T. (editors)

INTRODUCTION A. Peterek

The Cenozoic Eger Rift with its central Eger Graben, the crossing Mariánské Lázně Fault (MLF), and the Cheb-Domažlice Graben (CDG) belong to the most prominent morphotectonic structures of the Bohemian Massif (Malkovský 1987, Ziegler & Dézes 2006, 2007, Peterek et al. 2011). Earthquake swarms, CO2-emanation, and geomorphological/geological as well geophysical investigations give evidence for a concealed active magmatism (Kämpf et al. 2005, Bräuer et al. 2005, 2009) and ongoing tectonic activity.

During the last decades the term “Eger Rift” became prevalent against “Ohře-/Eger Graben”. This expression better includes the flanks of the Eger Graben east of the MLF but also the whole area west of it, including the Cheb-Domažlice Graben, the Česky les, the Upper Palatinate Forest, and the Fichtel Mountains (fig. 1). West of the MLF the Eger Rift is predominated by a complex pattern of horsts, grabens, and basins. However, the occurrence of fault systems that parallel the Eger Graben, and of Cenozoic volcanisms and CO2-degassing centers also in Bavaria clearly document the continuation of the volcanotectonic structure of the Eger Rift towards the SW. Moreover, the Cenozoic geological and geomorphological evolution in this part of the Eger Rift is very similar to that in the Czech part of the rift.

The Eger Rift is part of the “European Cenozoic Rift Systems” (Kopecký 1978; Prodehl et al. 1995, Ulrych et al. 2011, Sissingh 2006, Ziegler & Dézes 2006). Its geological evolution since the late Eocene is well documented by the stratigraphic record. The oldest sedimentary unit, the Staré Sedlo Fmt., belongs to a fluvial system that origined in the central Bohemian Massif and that crossed the not yet existing Eger Rift (Pietzsch 1962, Hurnik & Krutský 1995, Eismann 1997, Suhr 2003). Remnants of the Staré Seldo Fmt. are still preserved on the uprised flanks of the Eger Graben.

The evolution of the Eger Graben as a morphotectonic structure started not before the late Oligocene, most likely even not prior the early Miocene (23 – 19 Ma; Elznic et al. 1998). However, the present-day prominent morphostructure of the rift with steep escarpments and differences in altitude up to 600 meters most likely developed not before the late Pliocene (Peterek et al. 2011).

Volcanic activity along the Eger Rift started in its eastern part (České středohoří) already during the late Upper Cretaceous/early Tertiary (Ulrych & Pivec 1997, Ulrych et al. 2003). According to Ulrych et al. (2011) the main phases of volcanic activity are:

1) Pre-Rift phase (late Cretaceous until Middle Eocene; 79 – 49 Ma) in a compressional tectonic regime, 2) Syn-Rift phase (Middle Eocene until Mid-Miocene; 42 – 16 Ma) in a tensional tectonic regime, 3) Post-Rift phase (16-0.26 Ma) with 3.1) Middle Miocene until Upper Miocene (Messinian; 16 – 6 Ma) in a compressional tectonic regime, 3.2) Upper Miocene/Messinian until Lower Pleistocene (6 – 0.9 Ma) in a tensional tectonic regime, 3.3) Lower Pleistocene – Upper Pleistocene (0.9 – 0.26 Ma) in a compressional tectonic regime.

The Eger Rift consists of several subbasins (Fichtel Mts., Northern Upper Palatinate Basin, Cheb Basin, Sokolov Basin, Most Basin; fig. 1, 2) with similar sedimentary and tectonic evolution (for the Cheb Basin see fig. 3). In all basins the sedimentary records documents a hiatus after the deposition of the lower Miocene Cypris Fmt. (e.g. Rojik 2010). Sedimentation resumed again during the late Pliocene (Vildštejn Fmt; < 3.5 Ma, Bucha et al. 1990). These sediments mainly occur in the Cheb Basin and along the MLF towards the South (Domažlice Basin). Facies pattern and increase of the thickness of the Vildštejn Fmt. towards the MLF clearly document synsedimentary activity along this prominent fault during the Plio- /Pleistocene. The Vildštejn Fmt. is mainly absent in the central Eger Graben. It is unclear whether this is the consequence of erosion or it has not been deposited. In the western Eger Graben erosion predominates deposition. Partly, incision of the Ohře/Eger River occurs also into the basement rocks. Therefore, the graben is recently under uplift. This is consistent with the occurrence of young compressional deformation in Pleistocene sediments (Rojík 2010) and a compressional tectonic regime (Ulrych et al. 2011).

During the last two decades the CO2-emanation in the Cheb Basin and the intense earthquake swarm activity in its northeastern part (Nový Kostel area) came into the focus of several international working groups (with special publications in several journals, e.g. J. Geodynamics 35, 2003; Stud. Geoph. et geod. 44/2000, 52/2008, and 53/ 2009). Bankwitz et al. (2003) for the first time reported in the northern part of the Cheb Basin an active fault scarp (Plesná fault) along the southern prolongation of the so-called Počátky-Plesná Zone (PPZ). Since the PPZ seems to cross the MLF in the seismically active Nový Kostel area they concluded that the MLF is inactive and seismicity is related to the PPZ and the Plesná fault. Furthermore, they interpreted the PPZ to be part of the some hundred of kilometers long and seismically active Rostock-Leipzig-Regensburg lineament (Bankwitz et al. 2003). A lot of research work has been done by several working groups during the last years to clarify the morphotectonic and seismotectonic situation in the Nový Kostel area and along the Plesná fault zone (see for Kämpf et al. 2011, Peterek et al. 2011, and this conference abstract volume).

The northern part of the Cheb Basin is one of the seismically most active regions in Central Europe. Typical for the seismicity are earthquake swarms (“Erdbebenschwärme”, Herrmann Credner introduced first this term 1904 to describe such earthquakes in the area of NW Bohemia and Southwest Saxonia/Vogtland). Earthquake swarms are known especially from active rift zones with magmatic and volcanic activity (Kämpf et al. 2011). Earthquake swarms differ from classical tectonic earthquakes as they do not show one single prominent earthquake. Intense earthquake swarms can last several months with some ten thousands of earthquakes of similar magnitude and seismic characteristics.

During the last 30 years several periods with intense earthquake swarm activity occurred (July 1985 until April 1986, max. magnitude 4.6; August until December 2000, max. magnitude 3.3; October until December 2008, max. magnitude 3.8)(Fischer et al. 2010). Earthquake activity is concentrated mainly in the Nový Kostel area but also occurs in the areas of Marktredwitz, Plesná, Bad Elster, Lazy, Werdau, and in the region between Kraslice and Plauen (Neunhöfer & Hemmann 2005).

Recently, earthquake swarm activity is discussed to be triggered by magmatic fluids ascending from the upper mantle into the upper crust (Bräuer et al. 2009, Kämpf et al. 2011). Evidence for this is given among others by (lit in Kämpf et al. 2011):  the characteristics of the seismic waves (see for Fischer et al. 2010),  young volcanic and hydrothermal activity, 4

 origin of the CO2 in the mofetts and the mineral springs from magma sources in the lithospheric mantle, and  the rise of the Moho (from 30 – 31 km in the surroundings to 27 km) beneath the region of strong CO2-degassing in the triangular Františkovy Lázně – Mariánské Lázně – Karlovy Vary.

Fig. 1 Geological setting of the study area and the Eger Rift. Subregions of the Eger (Ohře) Rift: BERR = Bavarian Eger Rift Region, CB = Cheb Basin, DB = Domažlice Basin (CD + DB = Cheb-Domažlice Graben CDG), DV = Doupov volcanic complex, MB = Most Basin, NUPB = Northern Upper Palatinate Basin, SB = Sokolov Basin. MLF = Mariánské Lázně Fault. Source: Geological map 1 : 1 Mio., Federal Republic of Germany, FEDERAL INSTITUTE FOR GEOSCIENCES AND NATURAL RESOURCES (1993). From PETEREK et al. (2011).

Fig. 2 Geological map of the Cheb Basin and surroundings (modified from SCHUNK et al. 2003; based on Geological map 1 : 200.000, CC 6334, Bayreuth sheet; FEDERAL INSTITUTE FOR GEOSCIENCES AND NATURAL RESOURCES 1981) with the excursion stops (1 – 8).

1 = Late Variscan granites and granitoids; 2 = Variscan metamorphic units; 3 = Volcanics (mainly Oligo-/Miocene); 4 = Eocene – Oligocene (Staré Sedlo Formation); 5 = Miocene (Cypris Formation), partly covered by thin Pliocene deposits; 6 = Plio-/Pleistocene (Vildštejn Formation); 7 = Quaternary, 7a Quaternary undifferentiated, 7b = Volcanic cone; 8 = faults, 8a = mapped, 8b = supposed; 9 = Main swarm earthquake focal zone of Nový Kostel (according to FISCHER & HORÁLEK 2003); 10 = Water reservoirs; 11 = Czech-German border; 12 = location of cross-sections given in the excursion guide (P1, P2, P3). D. = Dvory, H. = Harbatov, KH = Komorní hůrka, M. = Milhostov, N. = Nebanice, ND. = Nový Drahov, NV. = Nová Ves, NKC = Nový Kostel seismic station, ZH = Železná hůrka. From PETEREK et al. (2011).

Fig. 3 Stratigraphy of the Cheb Basin (after ŠANTRŮČEK 1991, SHRBENÝ 1994, ULRYCH et al. 1999, ŠPIČÁKOVÁ et al. 2000, STD 2002, WAGNER et al. 2002, SCHUNK et al. 2003, KÄMPF et al. 2005). From PETEREK et al. (2011).

EXCURSION STOPS

STOP 1 Peterek, A. & Schunk, R. Location: South of the Jesenice water reservoir, 1 km east of Stebnice Topics: Overview Cheb Basin and Mariánské Lázně Fault

The viewpoint gives the opportunity to introduce the morphology of the Cheb Basin and its eastern marginal fault, the Mariánské Lázně Fault. The Cenozoic sedimentary infill of the asymmetrically subsided Cheb Basin is about 280 m (fig. 2, 4). Pre-Pliocene sediments also occur south of the southern marginal fault, the Wondreb fault that parallels the Eger Rift direction, obviously in paleovalleys. Southerly widespread pediments in an altitude between 490 to 530 m a.s.l. overlead to the Dyleň Massif. Remnants of deposits of the Vildstejn Fmt. document a formerly larger extension of this Plio-/Pleistocene unit. The Dyleň Massif is situated on the southern flank of the Eger Rift (fig. 5).

The Dyleň Massif and the Slavkovský les (east of the MLF) are separated by a broad depression, which links the Cheb Basin (CB) and the Domazlice Basin (DB). The drainage divide between the CB and the DB is located in this depression at Lázne Kynzvart, exactely where a line connecting the summits ot the two massifs crosses the depression (fig. 6). This drainage divide coincides with a small NW-SW striking topographic high located about 100 – 150 m above the average level of the CB.

Whilst the transition to the CB is characterised by step-like slopes, the topography gently decreases towards the SE. Valleys that are tributary to the CB are distinctly incised and show notably steeper longitudinal profiles than those flowing SE-ward into the DB. The depression lining the CB and DB is bounded to the NE by the prominent MLF escarpment towards which its topography decreases slightly, reflecting continuing activity along the MLF.

The depression forms part of the late Pliocene continuous Cheb-Domažlice Graben (CDG) as documented by moldavite-bearing late Pliocene to early Pleistocene deposits in the CB that were derived from the SE across the present-day water shed (fig. 6, A; Kopecký & Václ 1999; Trnka & Houzar 2002). The NW directed drainage of the CDG changed during the Pleistocene to the present-day SE directed system of the DB despite the Pleistocene subsidence of the CB (fig. 6, B). This drainage system reorganization is attributed to uplift of the southern Eger Rift flank, which extends across the CDG. Pleistocene accelerated subsidence of the CB enhanced stream gradients between the basin and the water shed, causing stream incision and retreat of the water shed towards the DB (fig. 6, C).

From the viewpoint the MLF and its continuation towards the north is well visible. A striking feature is that the escarpment of the MLF nearly disappears north of the Slavkovský les. This is related to the crossing Eger Graben (fig. 7). For the geological evolution of the Cheb Basin see fig. 8. Peterek et al. (2011) interpreted the recent crustal deformation in the area of the Cheb Basin different from that east of the MLF. Whereas the Eger Graben seems to be uprised due to compression, the CDG is deformed in a transtensional regime. Due to regional uplift of the southern flank of the Eger Rift the CB is separated from the DB (fig. 9). The MLF forms a fundamental boundary between the transtensionally deformed region west of it and the uplifted Eger Graben area.

Fig. 4 Geological cross-section through the Cheb Basin (CB) in the Nový Kostel area (modified after VÁCL, unpubl. data). For location see fig. 2 (P1). Vertical exaggeration: fivefold. From PETEREK et al. (2011).

Fig. 5 Profile across the Inner and Outer Cheb Basin summarizing its post-Pliocene evolution (geological units not to scale). Note elevation difference in the reconstructed aggradational basin plain during deposition of the Plio/Pleistocene Vildštejn Fm. and the early Mid- Pleistocene Milhostov Fm. and the present basin topography. For location see fig. 2 (P2). Vertical exaggeration: 12-fold. From PETEREK et al. (2011).

Fig. 6 Evolution of the drainage divide between the Cheb Basin (CB) and Domažlice Basin (DB) at the restraining bend of the MLF-A segment. A: NW-directed drainage of DB into CB as evidenced by moldavite-bearing Plio-/Pleistocene sediments; B: early Pleistocene uplift of the southern shoulder of the Eger Rift (Dyleň and Slavkovský les, SL) and drainage reversal in DB; C: subsidence of the CB causing intense stream incision, headward erosion and drainage capture. From PETEREK et al. (2011). 9

Fig. 7 Geological cross-section through the Plesná Fault Scarp, eastern Cheb Basin (for location see fig. 2: P3), showing the displacement of the Mid-Pleistocene landsurface across the Plesná Fault. The maximum displacement of the surface Δh is about 12 m. The base of the Milhostov Fmt. is not known. The Plesná Fault bounds the Central Cheb Basin Depression (CCBD) to the Northeast (see fig.11). Vertical exaggeration: 20-fold. From PETEREK et al. (2011).

Fig. 8 Longitudinal profile of the Ohře (Eger) River terraces T1 – T5 between Cheb in the West and Kynšperk nad Ohří in the East. From PETEREK et al. (2011).

Fig. 9 Geologic cross-sections retracing the evolution of the CB and MLF (not to scale). Compiled according to ŠANTRŮČEK (1991), SHRBENÝ (1994), ŠPIČÁKOVÁ et al. (2000), SCHUNK et al. (2003), SCHRÖDER & PETEREK (2001), SUHR (2003), and Peterek et al. (2011). From PETEREK et al. (2011). 12

STOP 2 Mrlina, J.1 & Kämpf, H.2 (1Institute of Geophysics ASCR, Prague, Czech Republic, 2GeoForschungsZentrum Potsdam, Germany) Location: Mýtina, Železná hůrka Topics: Quaternary magmatic activity – Železná hůrka scoria cone and Mytina maar, West Bohemia

West Bohemia is a region characterized by increased crustal dynamics that is expressed by relatively high seismotectonic activity, as well as the presence of Quaternary volcanoes and magmatic fluids emissions (CO2, He). There are three prominent neotectonic structures: the ENE–WSW trending Ohře (Eger) Rift, the NNW–SSE trending Cheb-Domažlice Graben and the N-S trending Regensburg-Leipzig-Rostock Zone (Bankwitz et al., 2003). At the junction of these three tectonic systems, the Quaternary volcanism is represented by the Komorní hůrka (Kammerbühl) and Železná hůrka (Eisenbühl) volcanoes.

Fig. 10 Location map of the western Eger rift area (after Mrlina et al., 2009). Black lines: tectonic faults; triangles: volcanoes (scoria cones) of Železná hůrka ZH and Komorní hůrka KH, Quaternary in age; red circle: location of Mytina Maar; white circles: seismicity (ML >0.5) from 1962 to 1999; stars: locations of main swarm areas; yellow ellipse represents the area of most active CO2 emissions sites; full and dashed lines: approximate course of the MLFZ Mariánské Laznĕ fault zone, PPZ Pocatky-Plesna zone, RLRZ Regensburg-Leipzig- Rostock zone, TFZ Tachov Fault zone. Upper right: position of the study area within central Europe.

The target of this excursion Stop-1 is to demonstrate different manifestations of “recent” (Quaternary) volcano-magmatic activity. The excursion in the surrounding of the Železná

13 hůrka Hill (Eisenbühl) includes two sub-stops – scoria cone of the Železná hůrka and the Mytina Maar crater with very different morphological characteristics. Stop 2-1: Železná hůrka Hill/Eisenbühl scoria cone

The hill (elevation 622 m) is situated approximately 11 km SSE of Cheb and 1 km N of Neualbenreuth just at the Czech-German border (Kämpf et al., 2007). Železná hůrka Hill Quaternary volcano pierces phyllites of the Cheb-Dyleň Crystalline Complex. It was Goethe (1823) who called attention to the Železná hůrka Hill (Eisenbühl).

A profile is exposed in a quarry in the southern part of hillock with superelevation of some 15 m. According to Hradecký (1994) the lower part of the whole scoria cone corresponds to Strombolian activity. With the extension of conduit, the Strombolian activity passed into that of Hawaian type. The two eruption types need not to be separated by a longer hiatus, the unconformity can be explained by a relatively short shift of the original vent or by eruption from the newly formed fissure. The presence of both types of pyroclastic rocks is a frequent phenomenon of cinder cones. The latest result of age determination by Mrlina et al. (2007) from a sample in the tephra layer about 1.5 km N of Železná hůrka provided the age of 288 ky.

Fig. 11 Železná hůrka quarry/outcrops with a gravimeter LaCoste&Romberg (left), and GPS surveying (photos J.Mrlina)

Stop 2-2: Quaternary Mytina maar structure (location: ca. 900m SSW of Mýtina)

Maar-diatreme volcanoes develop when magma rises in dykes and interacts with ground water causing thermohydraulic explosions (Lorenz et al., 2003), usually forming craters filled by lakes. Up-to-now, north of the Alps and east of the Eifel, Germany, there is no Quaternary maar known in Central Europe.

Based on stratigraphy, composition, and textural features of the tuff-tephra-deposit in a temporary excavation north of Mýtina, as well as the geometry of two large tephra fans in relation to morphological depression, Geissler et al. (2004) postulated the existence of a possible maar structure, Quaternary in age, close to the Železná hůrka scoria cone. From the topographic character of the area and from the digital elevation model, the morphological depression SW of Mýtina was a conspicuous structure, see Fig. 12.

Despite only limited geophysical data were available, the results of tentative 3D gravity modelling indicate that the depression could be formed by a volcanic explosion of maar 14 character. Such structure would be filled by various volcanic material of low density and high magnetic susceptibility, as well as by the relicts of country rocks. On top of the structure we expect a cover of alluvial and maar lake sediments. However, no maar sediments, diatreme breccia or volcanic material have been found on surface inside the depression. The morphological depression is open to NW - that is the trend of the Cheb-Domažlice graben and its western principal Tachov fault in particular. As well, a north-south trending regional fault system was documented in the adjacent area. Later, detailed gravity/magnetics survey in 2006-2008, and an exploratory drilling proved the existence of the Mytina Maar (Mrlina et al., 2009).

Fig. 12 Two views of topography (DEM) of the Mýtina surrounding region (after Mrlina et al., 2009). Left – 3D view from south, view inclination 77°, sunlight from west. Morphological features show general drainage trends with prevailing direction NNW-SSE and perpendicular NEE-SSW. Mýtina depression is in the centre, on top of a hilly massif (orange to ochre colour). Right – top view of gray scale DEM (sunlight from NW) with drainage system indicated by blue, red and green dashed lines. 1 – Železná hůrka volcano, 2 – CO2 emmission site, 3 – exploratory trench in Mýtina, 4 – morpho-logical depression of the maar.

Conclusion Despite no eartquake activity was recorded around the Železná hůrka volcano, the above described evidence of recent (Quaternary) volcanic/magmatic activity in the vicinity of Železná hůrka, together with nearby Kyselecký Hamr mineral water spring with significant CO2 emissions, indicate that this area belongs to the most dynamic parts of the West Bohemia region.

The two volcanic structures represent two completely opposite morphological characteristics – a scoria cone (hill) and a volcanic maar crater (depression). The maar was discovered thanks to the inspection of topografy and a test geophysical survey (Mrlina et al. 2007), that exhibited signifiant geophysical anomalies.

STOP 3 Dvořák, J. Location: Františkovy Lázně Spa Topics: mineral springs

The famous spa was founded in 1793. It was originally named Kaiser Franzensdorf (Emperor Francis II's village), later renamed to Franzensbad. The base for the spa are more than 20 mineral springs (unfortunately more than 10 dry up) and the fact that the town is located in a former moorland. Therefore, Františkovy Lázně was the first peat pulp bath in the world.

The natural mineral water originally emanated at natural springs, today they are exploited by well drillings with different depths. The content of mineral salt and carbon dioxide (CO2) depend from the geological layers from which the water origins. Typical is a high content of Glauber’s salts (Na2SO4·10H2O).

Fig. 13 Informations panels for three important mineral springs of Františkovy Lázně: Glauber III, Glauber IV, Kostelní in front of the main springhouse.

Fig. 14 Geological cross section across the northern part of the Cheb Basin with drilling wells for mineral water (after Burda & Babůrek 1998). 16

Characteristics of the mineral springs (according to Burda & Babůrek 1998): Temperature: 8.6 – 13 °C Discharge: 15 l/s (900 l/min) until 25 l/s (1500 l/min) – depending form CO2 pressure Chemistry: Type Na-SO4-HCO3-Cl, Na-SO4-Cl-HCO3, Na-SO4-Cl, with high content of SiO4 (bis 84 mg/l), mineral salts: 1.0 – 22 g/l.

The effect of medical application of the carbon dioxide is a better performance of the cardiovascular system. It also decreases the blood pressure in the pulse and lowers the occurrence of chronic inflammatory processes in the body. It further lowers rheumatic afflictions and improves the blood circulation in tissues and the vegetative stabilisation.

STOP 4 Peterek, A. & Schunk, R. Location: Lesinka, road side stop opposite of the bus stop Topics: Ohře/Eger River valley and displaced river terraces

Between Cheb in the W and Kynšperk nad Ohří in the E (fig. 2) the Ohře River is characterized by a flight of terraces (cp. Králik 1991). Although, the highest terraces are intensely eroded it is possible to distinguish five terraces between 1 m (= T1) and 20 m (= T5) above the recent floodplain. Longitudinal profiles of the terraces T1 to T5 show that the upper terraces (T3 to T5) diverge 8 km downstream from Cheb by up to 7 m (fig. 15) reflecting differential uplift of the downstream in the eastern part of the CB.

The youngest terraces T1 and T2 show no appreciable displacement. Terrace T3, which is only evident in the downstream part of the river, converges upstream with terrace T2. The observed displacement of the Ohře River terraces can be related to activity along the Nebanice Fault Zone in the prolongation of the Plesná Fault (fig. 16). Terrace T1, which consists of thick re-deposited soil material (colluvium) containing ceramics, is historic in age. Terraces T2 and T3 post-date the Last Glacial Maximum (Weichselian; < 15 ka) since neither loess deposits nor paleosoils of the Eemian interglacial were identified on them. Terrace T5 is well exposed in an open gravel pit 1 km west of Nebanice (location in fig. 4) and consists of deeply weathered fluvial sediments that are buried by solifluction deposits. Therefore, the terrace T5 must be older than the Eemian interglacial (115 – 126 ka) and thus must be Saalian in age (126 – 380 ka; Sqs 2010) or even older (Elsterian; 420 – 475 ka). Králik (1991) attributes terrace T5 to the third last glacial period based on the assumption that each glacial cycle is represented by a single terrace. This would be consistent with an Elsterian age of terrace T5. Although, the age of terrace T5 is still uncertain, we can set limits: about 145 ka at the minimum (Saalian glacial maximum; in this case terrace T4 must be late Saalian in age) and about 475 ka at the maximum (Elsterian glacial). Taking into account the cumulative 7 m vertical displacement of terrace T5 a displacement rate of 0.014 to 0.048 mm/a is indicated for the Nebanice Fault Zone.

The stop enables a view across the Ohře valley and shows the terrraces T1, T4, and T5 (according to the mapping of Schunk, in prep.).

Fig. 15 Morphotectonic map of the eastern Cheb Basin showing MLF and related faults. K = Kynšperk nad Ohří; MLF-A, MLF-B, MLF-C, MLF-D = segments of the MLF; N = Nebanice, NK = Nový Kostel, NKC = Seismic station Nový Kostel. From PETEREK et al. (2011). 18

Fig. 16 Neotectonic model for the western Eger Rift with Eger Graben, Cheb Basin, and Mariánské Lázně Fault area. Legend: 1 = direction of predominating extension; 2 = position of the PPZ (PPZ = seismic Počátky-Plesna Zone); 3 = vertical block movement: (-) = subsidence, (+) = uplift; 4 = topographic culmination due to uplift of the Eger Rift flanks; 5 = maximum horizontal stress direction (black arrows: after European Stress Map; white arrows: after focal mechanisms of earthquake swarms after IBS-VON SEHT et al. 2006); 6 = regional slope. Black lines = prominent faults. Abbreviations: CB = Cheb Basin, CFMB = Central Fichtel Mts. Basin, DB = Domažlice Basin, EG = Eger Graben, FL = Franconian Lineament, KTB = Continental deep drilling site Windischeschenbach, MLF = Mariánské Lázně Fault, NUPB = Northern Upper Palatinate Basin, SL = Slavkovský les, UPF = Upper Palatinate Forest. From PETEREK et al. (2011).

STOP 5 Dvořák, J. Location: Czech Natural Reserve of Soos, near Hájek (6 km NE Františkovy Lázně) Topics: Soos mofett field and mineral springs (text after Kämpf et al., 2005)

The nature protected area of Soos is a small post-glacial moorland area (2.2 km2). It is located in the centre of one of the largest NW-Bohemian gas emission zones, the escape centre of Františkovy Lázně (Weinlich et al. 1999). Besides the CO2 emanations, the Soos area is also well-known for various hydrochemical types of mineral and surface waters, mofettes,

19 organogenic sediments (diatomaceous earth, covered with salt efflorescence), and botanical specialities. The Soos Basin is a separate hydrogeological unit supplied with mineral and atmospheric water. The near-surface groundwater and mineral water belong to three types: sodium sulphate, sodium bicarbonate, and calcium-magnesium bicarbonate. Their total dissolved solid contents range from 0.1 to 6.3 g/l. In the central part of the diatomite deposits and the area of the mineral springs and mofettes black near-surface groundwater of sodium type occur with pH 7.6 to 8. The total gas flux in the Soos area by hundreds of mofettes and small gas vents is estimated to some hundreds of cubic meters per hour (Weinlich et al. 1999).

At one of the Soos mofettes, hydrostatic pressure, gas flow rate, water temperature, logger temperature, and soil temperature have been recorded for four years by the seismo- hydrological group of the Saxon Academy of Sciences/Bad Brambach (Koch et al. 2003; Škuthan et al. 2001). The results show that the gas flux depends on the barometric pressure, which is typical for open systems. Seismo-hydrological effects were not recorded. During several years gas flux and isotope compositions have been monitored at a second mofettes by the Deutsche GeoForschungsZentrum (GFZ) of the Helmholtz-Zentrum Potsdam and the Umweltforschungszentrum Leipzig-Halle (UFZ).

STOP 6 Fischer, T. & Horálek, J., Mrlina, J. & Polák, V. (Geophysical institute, Czech Academy of Sciences, Prague) Location: Skalná Topics: Geodynamic and seismological observatory in Skalná, earthquake swarm activity

Earthquake Swarm Activity in West Bohemia/Vogtland Fischer, T. & Horálek, J.,

From the viewpoint of recent geodynamics, the western part of the Bohemian Massif ranks among the exceptional natural laboratories of Europe. The occurrence of numerous mineral springs with a high production of CO2 of magmatic origin and repeating earthquake swarms are subjects of enduring interest to geophysicists. Earthquake swarms are sequences of numerous small events with shallow focal depths (usually 4 – 20 km) which distinctively cluster in time and space. Seismic swarms are in general associated with active volcanism and geothermal fields. Their origin is usually explained as an interaction of the tectonic stress and high-pressurised crustal fluids in a subcritically loaded rock environment.

Earthquakes occur most frequently on preexisting faults. Two almost vertical fault systems intersect the region: the Eger Rift – a neo-tectonic structure in ENE-WSW direction that reaches great depths – and the Marianské Lázně Fault in NNW-SSE direction. Also different fault directions with prevailing N-S trend were identified in the Cheb Basin, which is the place of most frequent earthquake swarm activity within the previous 100 years.

Up to the present, the strongest instrumentally registered earthquake in the region on November 3, 1908 reached a magnitude of ML ≈ 5.0 and dominated in a series of earthquake swarms, which occurred there during the years from 1896 to 1908. The first seismographs were installed in the region during that period of high seismic activity – one in the German town of Plauen (in 1905) and another, the first seismograph in Czech territory, in the town of Cheb (in 1908). However, the low sensitivity of these seismographs permitted the registration of only strong local earthquakes that recorded more than 3.0 on the Richter scale (ML > 3.0). The recurring seismic activity in that period gave the name to earthquake swarms; the term 20

Schwarmbeben comes from research of German spa engineers at the end of the 19th century. Earthquake activity in the region of western Bohemia recurred several times in the second half of the 20th century. Among the earthquake swarms that were felt by local residents are the swarms of autumn 1962, the turn of the year 1985-86, in the autumn 2000 and 2008 and in late summer of 2011.

West Bohemia and Vogtland belong to the best-monitored seismically active areas in Europe. WEBNET network, jointly operated by the Geophysical Institute and the Institute of Rock Structure and Mechanics of the ASCR in Prague is deployed in the Czech part of the seismoactive region. Further networks have been operating in NE Bavaria and SE Saxony. WEBNET network consists of thirteen three-component digital seismic stations covering an area of about 900 km2. Its configuration and the parameters of seismograph systems guarantee high-quality recording of local events of magnitudes -0.5  ML  5. On the basis of continuous observations several seismically active zones were determined. The main epicentral zone, where almost 90% seismic energy was released is situated in the area of Nový Kostel (the main hypocentre cluster in Fig. 17).

Fig. 17 3-D cube showing the hypocenters of swarm seismicity in the area of Cheb Basin within the period 1991 – 2011. WEBNET stations are indicated by pink triangles. The size of hypocenter symbols is proportional to earthquake magnitiude and their color is proportional to the occurrence time. (top). Magnitude - Time plot for the same time period (bottom). 21

Epicenters in this area line up in a north-south direction (strike 169oN) and the focal zone displays a pronounced westward dipping (dip 80 o) plane at depths between 6 and 11 km (Fig. 17). The source mechanisms are of oblique strike-slip type, which matches very well the geometry of the hypocenter cluster. Most of them point to left-lateral slip with subsidence of the western block corresponding to the basement of the Cheb basin. However, the strike of the fault differs from that of the Mariánské Lázně Fault by ~25°, which indicates that different fault system is activated by the recent seismic activity. No fault outcrop that could be associated to the seismic activity in depth was identified so far.

Several dry CO2 vents (mofettes) are located in the Cheb Basin. The CO2 flux and further parameters are monitored in the Soos and Hartoušov mofettes. So far, no anomalies of CO2 flux related to the seismic activity have been identified.

Geodynamic observatory in Skalná, West Bohemia Mrlina, J. & Polák, V.

In the seismoactive region of West Bohemia (e.g. Fischer et al., 2003, Horálek et al., 1996, and others) continuous detailed seismological observations were initiated after the earthquake swarm in 1985/86. Further, some geodynamic observations have been introduced to the West Bohemia region in mid-90-ties: GPS and precise levelling for surface displacement control, repeated gravity measurements aimed at mass/stress redistribution monitoring, and groundwater level observations (Mrlina, 2000, Mrlina et al., 2003, Mrlina and Seidl, 2008). Later, one seismological station has been converted into a complex geodynamic observatory. The aim was to monitor continuously the ongoing geodynamic processes and to improve our chance to detect potential precursory phenomena preceding earthquake swarms.

Fig. 18 Gravimeter Graviton EG during data transfer (left), and the recording unit of tiltmeters (right). The tiltmeters are covered by plastic sheets.

The observatory SKAL is located in an underground gallery of a granite outcrop in the valley passing through the town of Skalná. It is also hosting one of the seismic stations of the WEBNET network. The multiparameter observatory is thus equipped with a seismograph, a couple of tiltmeters, a barometer and a strainmeter. In some time periods, the observations are supplemented by continuous measurements of gravity to evaluate local changes of gravity field (Fig. 18). Significant signal was recorded during the Sumatra earthquake in Dec. 2004 by the LCR Graviton EG apparatus. The records document the fact that even distant regional and global events can lead to consequent redistribution of stress and mass that are detectable by sensitive gravimeters (Mrlina in Boušková et al., 2007).

Fig. 19 Tiltmeter record showing changes of tilt during 2 microswarms in areas adjacent to the observatory in February 2007. The Nový Kostel microswarm (8 km NE from the observatory) was reflected by a sharp tilt to ENE, while the Skalná – Plesná microswarm (2 km to the north by approx. three-day tilt to SWW followed by a change of long-term trend of tilts.

Observatory SKALNA, West Bohemia Tiltmeters: raw data 1-30 October, 2008 N-S Institute of Geophysics, Prague – Geodynamics Group E-W

Anomalous tilts incl. sharp shifts were observed during earthquake swarm 10/2008

Phases of earthquake swarm 10/2008

16 14 12 10 Precipitation (mm) 8 6 precip. (mm) precip. 4 2 0 1.10.08 2.10.08 3.10.08 4.10.08 5.10.08 6.10.08 7.10.08 8.10.08 9.10.08 10.10.08 11.10.08 12.10.08 13.10.08 14.10.08 15.10.08 16.10.08 17.10.08 18.10.08 19.10.08 20.10.08 21.10.08 22.10.08 23.10.08 24.10.08 25.10.08 26.10.08 27.10.08 28.10.08 29.10.08 30.10.08

Fig. 20 Tiltmeter record showing abrupt tares and change of trends during the first phase of the Autumn 2008 significant earthquake swarm. Some tilt indications also reflect rainfall periods. 23

Tiltmeters were installed in 2004. No enormous tilts have been recorder till now. However, an example of the tilts related to February 2007 microswarm are presented as an example. Despite barometric pressure disturbing effects, it is clear that the tiltmeters reflect the behaviour of the massif during such tectonic events, see Fig. 19. Much stronger disturbances and tilt changes were observed before and during the Autumn 2008 swarm, see Fig. 20.

STOP 7 Štěpančíková, P. (Institute of Rock Structure and Mechanics, Czech Academy of Sciences, Prague) Location: Kopanina site, between Nový Kostel and Kopanina village Topics: Fault scarp morphology within the Mariánské Lázně fault zone

The site is situated at the mountain front line of the Krušné hory Mts. controlled by the northern termination of the MLF, referred as the Eastern Marginal Fault of the Cheb Basin, between Kopanina and Nový Kostel villages. The trace of the fault controlling the most recent morphology of the marginal slope within the MLF zone is suggested by a linear arrangement of points where series of sub-parallel valleys become deeply incised into an apparently uplifted blocks (Fig. 21). In the Kopanina site, the fault trace was inferred from a linear foot of the slope with gently convex morphology. The geomorphologic analysis facilitated to place a paleoseismic trench of 100 m length, azimuth of 62°, and varying depth of 1.5 to 2.5 m, which has been however already filled back.

The trench exposed a succession of sedimentary units (Fig. 22), whose lithologies are briefly described downhill southwestwards as follows: in the very upper part of the trench fluvio-colluvial sandy deposits with cobbles fill the depression in clayey-sandy colluvial sediments, which cover completely disintegrated, chemically weathered mica- schists basement. Following inclined beds of probably Lower Clay and Sand Formation overlaying the basement consist of basal conglomerates with ferric cement, heterogenous units of poorly sorted sandy gravels with clayey silty matrix, and reworked gravely sands with ferricretes. This formation is terminated by the fault striking at 162° towards the following Vildstein Formation, which is formed by diagonally stratified fine gravels and sands. These sediments are disturbed by minor sub-parallel 137°-142° striking normal faults with offsets of ca 10 cm. Further downhill, up to 45° tilted heterogeneous Fig. 21 Studied fault trace within the layers of overlying fine gravels and sands Mariánské Lázně Fault zone indicated by are cut by the sub-vertical fault with strike slope change and linear arrangement of of 132°. This fault filled with white clay is beginnings of deeper valleys. accompanied by distinctive iron mineralization penetrating laterally. Very 24 preliminary results of OSL dating suggest the age of the sediments cut by this fault as cca 260 ka. The following layers of clayey sand to clay are downwarped and deformed by the youngest 134° striking fault, which separates them from deformed stratified coarse sands to the southwest. This youngest fault coincides with the slightly convex morphology of the fault scarp on the foot of the slope. The youngest sediments downwarped by this fault were dated by radiocarbon dating method as cca 4.8 ka BP and further current dating is expected to might show even younger age. In the lowest part of the trench clayey sand to clay is overlain by loamy gravelly colluvium.

Fig. 22 Lithological section along the trench Kpanina.

STOP 8 Peterek, A. Location: Hartoušov Topics: moffetes

Plesná valley near to Hartoušov

The Hartoušov area came into the focus of interest of a multidisciplinary working group during the last years (see Kämpf et al. 2011). It is located in the Plesná valley approx. 1.5 km south of the well-known mofette of Bublak which is the mofette with the highest rate of CO2- emanation in the Cheb Basin (at least 18.000 l/h).

At the Hartoušov site several “dry mofettes” occur that belong to a “Diffuse Degassing Structure” (Kämpf et al. 2011). The degassing area is located in the alluvial plain of the valley and is approx. 400 long and 200 m broad. It runs NNW-SSE. Since 2007 geophysical, geological as well as biological and geochemical studies have been carried out mainly in the southern part of the structure (reported by Kämpf et al. 2011). In this central area, which is slightly elevated, CO2-degassing rates show the highest values and the content of chlorophyll of the plants is reduced (Pfanz & Sassmannshausen 2010). The plants are smaller than in the surroundings with lower root depth. Several slots occur with dead insects (CO2 vents).

Geoelectrical studies carried out by Flechsig and collaborators (in Kämpf et al. 2011) show high CO2 degassing in the central part of the structure: 6.5 kg/m2/day whereas at the flanks the values decrease to 0.04 kg/m2/day. The CO2 content in the soil gas reaches values more than 80 %, whereas it decreases towards the flanks less than 1 %.

In the degassing center a more than 2 m thick Corg-rich layer was drilled. The Corg content decreases drastically towards the flanks. Kämpf et al. interprete this as a combined result of anorganic and microbiological influences caused by the high CO2 content and low O2

25 concentration, respectively. Flechsig et al. (2008) assume that in the degassing centre microbiological activity and biodegradation is reduced.

The biological investigations show more than 100 plant species with the dominance of grasses and sedges (Sassmannshausen 2010, Rennert et al. 2011). The distribution of the species correlates with the CO2 content in the soil gas. Carbon isotopic investigations on the gras Deschampsia cespotosia indicate that in the degassing center the plants use up to 37 % of geogene CO2 for covering their need of carbon (lit. in Kämpf et al. 2011). Zoological studies had been carried out by Hohlberg and Schulz from the Senkenberg Museum Görlitz. They showed that even in an atmosphere of 100 % of CO2 in the soil gas springtails and nematodes exist. The values of the CO2 in the soil gas influence the compositon of the individial species. It is remarkable that also springtails occur that are known only from Norway, the Arctic archipelagos, NE Siberia, and Middle Asia. The springtail Folsomia mofettophila (Schulz & Potapov 2011) was describted for the first time at the Hartoušov site. They belong to the springtail group of Folsomia bisetosa, that are known from the circumpolar region.

The diffuse degassing structure of Hartousov is an unique biosphere influenced by the CO2.

REFERENCES

Bankwitz, P., Schneider, G., Kämpf, H. & Bankwitz, E. (2003): Structural characteristics of epicentral areas in Central Europe: study case Cheb Basin (Czech Republic). – J. Geodynamics 35: 5-32.

Boušková, A., Horálek, J., Mrlina, J., Polák, V. and Špičák, A. (2007): Seismic and geodynamic observatory of the Institute of Geophysics, Academy of Sciences of the Czech Republic, Skalná near Cheb. - Proceedings and Excursion Guide - CzechTec 07 (Edit. Z.Venera), April 11-14, 2007, Teplá, Czech Republic, 113-119.

Bräuer, K., Kämpf, H., Niedermann, S. & Strauch, G. (2005): Evidence for ascending upper mantle- derived melt beneath the Cheb basin, central Europe. – Geophys. Res. Lett. 32, L08303, doi: 10.1029/2004GL022205.

Bucha, V., Horácek, J. & Malkovský, M. (1990): Palaeomagnetic stratigraphy of the Tertiary of the Cheb Basin (W-Bohemia). – Vĕstnik Ústředního ústavu geologického 65(5): 267-278.

Burda, J. und Babůrek, J. (1998): Hydrogeologie des westböhmischen Bäderdreieckes (Frantiskovy Lazne / Franzensbad – Karlovy Vary / Karlsbad – Marianske Lazne / Marienbad). Jber. Mitt. oberrhein. geol. Ver., N.F. 80, 91-110.

Credner, H. (1904): Der Vogtländische Erdbebenschwarm vom 13. Februar bis zum 18. Mai 1903 und seine Registrierung durch das Wiechertsche Pendelseismometer in Leipzig, Abhandl. d. K.S. Gesellsch. d. Wissensch., math-phys Kl., XXVIII (Nr. VI), 419–530.

Eissmann, L. (1997): Das quartäre Eiszeitalter in Sachsen und Nordostthüringen. Landschaftswandel am Südrand des skandinavischen Vereisungsgebietes. – Altenbg. nat. wiss. Forsch., 8: 1-98; Altenburg.

Elznic, A., Čadková, Z. & Dušek, P. (1998): Palaeogeography of the Tertiary sediments of the North Bohemian Basin. – Sbor. Geol. Ved. Geol. 48: 19-46; Prague (in Czech).

Fischer, T. and Horálek, J., 2003: Space-time distribution of earthquake swarms in the principal focal zone of the NW Bohemia/Vogtland seismoactive region: period 1985-2001. J.Geodynamics, 35/1-2, 125-144.

Fischer, T., Horalek, J., Michalek, J. & Bouskova, A. (2010): The 2008 West Bohemia earthquake swarm in the light of the WEBNET network, J. Seismol., 14, 665-682.

Fischer T., Štěpančíková P., Karousová M., Tábořík P., Flechsig Ch. (2012): Imaging the Mariánské Lázně Fault (Czech Republic) by 3-D ground-penetrating radar and electric resistivity tomography. Studia Geophysica et Geodaetica, (submitted).

Flechsig, C., Bussert, R.,. Rechner, J., Schütze, C. & Kämpf, H. (2008): The Hartousov Mofette Field in the Cheb Basin, Western Eger Rift (Czech Republic): a Comperative Geoelectric, Sedimentologic and Soil Gas Study of a Magmatic Diffuse CO2-degassing Structure, Z. Geol. Wiss. 36, 3, 177-193.

Geissler W.H., Kämpf H., Bankwitz P. und E. Bankwitz (2004): Das quartäre Tephra-Tuff- Vorkommen von Mytina (Südrand des westlichen Eger-Grabens/Tschechische Republik): Indikationen für Ausbruchs- und Deformationsprozesse. - Z. geol. Wiss., 32, 31-54.

Goethe, v. W. (1823): Uralte, neu entdeckte Naturfeuer und Gluthspuren. - In: Goethes werke, Ed. Cotta (1851), Bd. XXX, 239-242.

Horálek J., Boušková A., Hampl F., and Fischer T., 1996: Seismic regime of the West-Bohemian earthquake swarm region: Preliminary results. Studia geophys. et geod. 40, 398-412.

Horálek J., and T. Fischer, 2010. Intraplate earthquake swarms in West Bohemia/Vogtland (Central Europe), Jökull, 60, 67-88.

Hradecký, P. (1994): Volcanology of Železná and Komorní hůrka in Western Bohemia. – Věst. Čes. geol. Úst., 69, 2, 89–92.

Hurnik, S. & Krutský, N. (1995): Paläogeographische Probleme des Nordböhmischen Tertiärs. – Z. geol. Wiss., 23: 219-223; Berlin.

Ibs-von Seht, M., Plenefisch, T. & Schmedes, E. (2006): Fault style and stress field investigations for swarm earthquakes in NE Bavaria/Germany – the transition between Vogtland/NW-Bohemia and the KTB-site. – J. Seismology 10: 197-211.

Kämpf, H., Mrlina, J., Ulrych, J., Ackerman, L. and P. Hradecky (2007): STOP 3 (3-1 to 3-3) Surroundings of the Železná Hůrka Hill (Eisenbühl). - In: Z. Venera (Ed.), CzechTec 07, Proceedings and excursion guide, 119-125, Czech Geological Survey, Prague, ISBN 978-80-7075-695-0.

Kämpf, H., Peterek, A., Flechsig, C., Bräuer, K., Strauch, G. & Schunk, R. (2011): Junge Tektonik, Vulkanismus, aktive magmatische Prozesse und CO2-Geo-Bio-Wechselbeziehungen in der Schwarmbebenregion des westlichen Eger Rifts. – Exkursionsführer 21. Jahreshauptversammlung des Thüringischen Geologischen Vereins e. V. Marktredwitz 24. - 27.06.2011, 1-56, Jena.

Kämpf, H., Peterek, A., Rohrmüller, J., Kümpel, H.-J. & Geissler, W. (eds.) (2005): The KTB Deep Crustal Laboratory and the western Eger Graben. – Schriftenreihe Dt. Ges. Geowiss. 40: 37-107.

Koch, U., Heinicke, J. & Voßberg, M. (2003): Hydrogeological effects of the latest Vogtland-NW Bohemian swarmquake period (August to December 2000). – J. Geodyn., 35: 107-123.

Kopecký, L. (1978): Neoidic taphrogenic evolution of young alkine volcanism of the Bohemian Massif. – Sborník Geologických Vĕd. Řada Geologie 30, 91-107.

Kopecký, L. & Václ, J. (1999): Problematik der Lokalisation des Streufeldes der Moldavite aus dem Eger-Becken. – Schr. Staatl. Mus. Mineral. Geol. Dresden 10: 57-58.

Králik, F. (1991): Kvarteru. – In: P. Šantrůček (ed.): Geologická Mapa ČR, Cheb (11-14), 1:50.000. – Czech Geological Survey, Prague.

Lorenz V., Suhr, P. & Goth, K. (2003): Maar-Diatrem-Vulkanismus – Ursachen und Folgen. Die Guttauer Vulkangruppe in Ostsachsen als Beispiel für die komplexen Zusammenhänge. - Z. geol. Wiss., 31(4-6), 267-312, Berlin.

Malkovský, M. (1987): The Mesozoic and Tertiary basins of the Bohemian Massif and their evolution. – Tectonophysics 137: 31-42.

Mrlina, J., 2000. Vertical displacements in the Nový Kostel seismoactive area. Studia geoph. et geod., 44, 336-345. 27

Mrlina, J., Kämpf, H., Geissler, W.H., van den Boogart, P. (2007): Assumed Quaternary maar structure at the Czech/German boundary between Mýtina and Neualbenreuth (western Eger Rift, Central Europe): geophysical, petrochemical and geochronological indications – Z. geol. Wiss., 35, 4- 5: 213-230.

Mrlina, J., Kämpf, H., Kroner, C., Mingram, J., Stebich, M., Brauer, A., Geissler, W.H., Kallmeyer, J., Matthes, H. and Seidl, M. (2009): Discovery of the first Quaternary maar in the Bohemian Massif, Central Europe, based on combined geophysical and geological surveys. – J. Volc. Geoth. Res. , 182, 97-112.

Mrlina, J. and Seidl, M. (2008): Relation of surface movements in West Bohemia to earthquake swarms. – Stud. Geoph. Geod., 52, 4, 549-566.

Mrlina, J., Špičák, A. and Skalský, L., 2003. Non-seismological indications of recent tectonic activity in the West Bohemia earthquake swarm region. J. Geodynamics, 35, 1-2, 221-234. Neunhöfer, H. & Hemmann, A. (2005): Earthquake swarms in the Vogtland/Western Bohemia region: Spatial distribution and magnitude–frequency distribution as an indication of the genesis of swarms? J. Geodyn., 39, 2005, 361–385.

Peterek, A., Reuther C.-D. & Schunk, R. (2011): Neotectonic evolution of the Cheb Basin (Northwestern Bohemia, Czech Republic) and ist implications for the late Pliocene to Recent crustal deformation in the western part of the Eger Rift. – Z. geol. Wiss., 335-365, Berlin.

Pietzsch, K. (1962): Geologie von Sachsen. – 618 S., Berlin (Akademie-Verlag).

Pfanz H., & Sassmannshausen, F. (2008): Geogenic CO2-Exhalations and Vegetation: Its possible use to predict volcanic eruptions, Geophys. Res. Abstr. 10, EUG2008-A-12108.

Prodehl, C., Müller, S. & Haak, V. (1995): The European Cenozoic rift system. – In: K.H. Olsen (ed.): Continental rifts: evolution, structure, tectonics. – Developments in Geotectonics 25: 133-212.

Rennert, T., Eeustehues, K., Pfanz, H. & Totsche, K.U. (2011): Influence of geogenic CO2 on mineral and organic soil constituents on a mofette site in the NW Czech Republic, Eur. J. Soil Sci., akzeptiert, doi: 10.1111/j.1365-2389.2011.01355.x

Rojík, P. (2004): New stratigraphic subdivision of the Tertiary of the Sokolov Basin in the Northwestern Bohemia. – J. Czech Geol. Soc. 49: 173-185.

Rojík, P., Dašková, J., Fejfar, O., Krásný, J., Kvažek, Z., Pešek, J., Sýkorová & Teodoridis, V. (2010): Chebská pánev. - In: Pešek, J. (ed.): Terciérní pánve a ložiska hnedého uhlí České republiky: 206–229, Prague (Česká geologická služba).

Sassmannshausen, F. (2010): Vegetationsökologische Charakterisierung terrestrischer Mofettenstandorte am Beispiel des westtschechischen Plesná-Tals, unv. Diss., Universität Duesburg- Essen.

Shrbený, O. (1994): Tertiary of the Bohemian Massif. – In: Klomínský, J. (ed.): Geological Atlas of the Czech Republic. Stratigraphy. Czech Geological Survey, Prague.

Schulz, H.-J. & Potapov, M. (2010): A new species of Folsomia from mofette fields of the Northwest Czechia (Collembola, Isotomidae), ZOOTAXA, 2253, 60-64.

Schröder, B. & Peterek, A. (2001): Känozoische Hebungs- und Abtragungsgeschichte im Umfeld des westlichen Egergrabens. – Z. Deutsch. Geol. Ges. 152: 387-403.

Schunk, R. (in prep.): Structure and morphogenesis of the Cheb Basin since the late Pliocene. – PhD Thesis, Hamburg University.

Schunk, R., Peterek, A. & Reuther, C.-D. (2003): Untersuchungen zur quartären und rezenten Tektonik im Umfeld der Marienbader Störung und des Egerer Beckens (Tschechien) - erste Ergebnisse. – Mitt. Geol.-Paläont. Inst. Univ. Hamburg 87: 19-46.

Sissingh, W. (2006): Syn-kinematic palaeogeographic evolution of the West European Platform: correlation with Alpine plate collision and foreland deformation. – Netherlands J. of Geosciences 85: 131-180.

Sqs (= Subcommission on Quaternary Stratigraphy)(2010): Global chronostratigraphical correlation table for the last 2.7 million years. – http://www.quaternary.stratigraphy.org.uk/charts/

Std (= Deutsche Stratigraphische Kommission)(2002): Stratigraphische Tabelle von Deutschland 2002. – Forschungsinstitut Senckenberg, Frankfurt a. Main.

Suhr, P. (2003): The Bohemian Massif as a catchment area for the NW European Tertiary Basin. – Geolines 15, 147-159.

Šantrůček, P. (ed.)(1991): Geological map of Czech Republic, sheet 11-14, Cheb, 1:50.000. – Czech Geologcial Survey, Prague

Škuthan, B., Hron, J., Pěček, J. & Keprta, M. (2001): Carbon dioxide field in the West Bohemian Spring Region: Introductory results. – Bull. Czech. Geol. Surv., 76: 203-208.

Škvor, V. & Sattran, V. (eds.) (1974): Krušné Hory, západní část, 1:50.000. – Ústředni ústav geologický, Prague.

Špičáková, L., Uličný, D. & Koudelková, G. (2000): Tectonosedimentary evolution of the Cheb Basin (NW Bohemia, Czech Republic) between the Late Oligocene and Pliocene: a preliminary note. – Studia geoph. et geod. 44, 556-580.

Trnka, M. & Houzar, S. (2002): Moldavites: a review. – Bull. Czech Geol. Surv. 77: 283-302.

Ulrych, J., Dostal, J., Adamovič, J., Jelínek, E., Špaček, Hegner, E. & Balogh, K. (2011): Recurrent Cenozoic volcanic activity in the Bohemian Massif (Czech Republic). – Lithos 123: 133-144.

Ulrych, J., Lloyd, F.E. & Balogh, K. (2003): Age relations and geochemical constraints of Cenozoic Alkaline Volcanic series in W Bohemia: a review. – Geolines 15: 168-180.

Ulrych, J. & Pivec, E. (1997): Age-related contrasting alkaline volcanic series in North Bohemia. – Chem. Erde, 57: 311-356; Jena.

Václ, J. (1966): The Cheb Basin. – In: Svoboda, J. (ed.): Regional geology of Czechoslovakia. Part I: The Bohemian Massif. – Ústr. úst. geol.: 516-532, Prague.

Václ, J. (1979): Geologická stavba chebské pánve jejího okolí. – Geologický průzkum 8: 233-235.

Wagner, G.A., Gögen, K., Jonkhere, R., Wagner, I. & Woda, C. (2002): Dating of the Quaternary volcanoes Komorní Hůrka (Kammerbühl) and Železná Hůrka (Eisenbühl), Czech Republic, by TL-, ESR-, alpha-recoil and fission track chronometry. – Z. geol. Wiss. 30, 191-200.

Weinlich, F., Bräuer, K., Kämpf, H., Strauch, G., Tesař, J. & Weise, S. (1999): An active subcontinental mantle volatile system in the western Eger Rift, Central Europe: Gas flux, isotopic (He, C, and N) and compositional fingerprints. – Geochim. Cosmochim. Acta 63: 3652-3671.

Ziegler, P.A. & Dèzes, P. (2006): Crustal evolution of Western and Central Europe. – Mem. Geol. Soc. Lond. 32: 43-56.

Ziegler, P.A. & Dèzes, P. (2007): Cenozoic uplift ofVariscan Massifs in the Alpine foreland: Timing and controlling mechanisms. - Global and Planetary Change 58: 237–269. doi:10.1016/j.gloplacha.2006.12.004.