Publisher © Czech Geological Survey, ISSN: 2336-5757 (online), 0514-8057 (print)
Spatial variations of radon concentrations and equivalent gamma dose rate at faults in the Flysch and basinal clastic sediments of Central Moravia
Published online: June 20, 2018 Barnet, I. - Poňavič, M. - Pacherová, P. (2017): Variace radonu a dávkového příkonu na tektonických poruchách v sedimentárních horninách Českého masivu. - Zpr. geol. Výzk. 50, 57-63. Havíř, J. - Pazdírková, J. - Sýkorová, Z. (2012): Zvýšená seizmická aktivita v epicentrální oblasti Lašťany (střední Morava). Increased seizmic activity in the epicentral area Lašťany (central Moravia). - Geol. Výzk. Mor. Slez., 47-49. Havlíček, P. et al. (1999): Geologická mapa ČR 1 : 50 000, list 25-31 Kroměříž. - Čes. geol. služba. Praha. Nováková, Z. (2016): Mapování kvartérní výplně lutínské brázdy a hornomoravského úvalu metodami mělké geofyziky: refrakční seizmika, georadar. Diplom. práce. - Univ. Palackého. Olomouc. Pacherová, P. - Poňavič, M. - Barnet, I. (2016): Variace radonu a dávkového příkonu na tektonických poruchách v metamorfitech a granitoidech (Český masiv). - Zpr. geol. Výzk. 49, 69-74. Pálenský, P. et al. (1997): Geologická mapa ČR 1 : 50 000, list 25-13 Přerov. - Čes. geol. služba. Praha. Růžička, M. et al. (1997): Geologická mapa ČR 1 : 50 000, list 24-22 Olomouc. - Čes. geol. služba. Praha. Růžička, M. (2016): Účelová geologická mapa hydrogeologických rajonů 1610-1624 a textové vysvětlivky (kvartér horní Moravy). - MS Čes. geol. služba. Praha. Špaček, P. - Sýkorová, Z. - Pazdírková, J. - Švancara, J. - Havíř, J. (2006): Present-day seizmicity of the south-eastern Elbe fault system (NE Bohemian Massif). - Stud. Geophys. Geod. 50, 233-258. Zimák, J. (2012): Přirozená radioaktivita kulmských sedimentů na východním okraji Českého masivu. - Geol. Výzk. Mor. Slez., 130-133. Abstract
The variations of radon concentrations and equivalent gamma dose rate (referred to as Rn and H´) were studied in sedimentary rocks on the contact of the Bohemian Massif and Carpathian Outer Flysch (Central Moravia) along profiles oriented perpendicularly to the supposed and detected and overthrust faults. These measurements were carried out recently on faults in the Bohemian Massif (Pacherová et al. 2016, Barnet et al. 2017). The faults in Central Moravia are characterized by a thick Quaternary cover but are thought to attain greater depths. Three areas were selected for measurements (16 profiles - 10 measured points each, inferred fault core at point 5, the measured points are 3 m apart, Rn was measured at a depth of 80 cm using a radonmeter RM 2, and H´ was measured 1 m above the ground using radiometer Gamma-Scout®). The surveyed areas are situated at Lutín close to Olomouc (localities 1-5 with supposed faults and Carboniferous metashales forming the bedrock), at Fryšták near Zlín (localities 6-11 with overthrust faults, bedrock formed by Paleocene sandstones and Cretaceous claystones), and around the Kokory near Přerov (localities 12-16 with detected faults, bedrock formed partly of Miocene sediments and Carboniferous laminated metashales). The position of individual profiles is shown in Fig. 1. The results of mutual trends of Rn and H´ along the measured profiles in all three areas (with respect to inferred fault at point 5 of each profile) are presented in Table 1. The differences in medians of Rn and H´ in individual areas are shown in Fig. 2, which can be explained by different types of faults and the bedrock geology; Fig. 3 illustrates the number of Rn and H´ maximum values around the supposed fault core at point 5 of the profile. The medians of Rn and H´ (Fig. 4) at individual profile points show the decrease in both measured parameters at point 5, while the rise of medians can be observed at points 4 and 7 of the measured profiles. This may indicate a greater extent of fault zone around relatively less permeable fault core. Similar observations were made in platform sediments of the Bohemian Massif. The results of radon and equivalent gamma dose rate variations will be used for upgrading the Complex radon information within the web mapping server of the Czech Geological Survey.References
