Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Krutský

Protection of maars along the western margin of the České středohoří Mts

Journal of the Czech Geological Society, volume 39 (1994), issue 2-3, 251 - 256

The article deals with the state of the main maars at the West margin of the České středohoří Mts. (North Bohemia) from the point of view of their protection as significant natural monuments. Maars as products of likely the younger phase of Tertiary volcanic activity in North Bohemia are best preserved in the South environs of Most at Bečov. Their sediment filling occurs in the overburden of pipe breccias of some diatremes, whereas maar sediments of the majority of diatremes were not preserved. For protection as natural geological monuments, there are proposed 2 major localities - Písečný vrch (317 m) and Verpánek (356 m), SE of Bečov on both sides of the road to Raná. At Písečný vrch, there is a diatreme with a fossil maar filling covering an area 800x200 m, at Verpánek an area 750x600 m. In the first case, subaqueous sediments consist of sands to sandstones with layers of tuffites and contain large blocks of quartzites which originated by silicification. These sediments are cut by pipe breccias with xenolites of Cretaceous and Tertiary rocks, gneiss and fossil wood. According to Kopecký (1971), it is the most characteristic maar of the region exhibiting best outcrops. At Verpánek, there are subaerial and subaqueous maar sediments in overburden of the pipe breccia. In the latter, tuffites with lenses of silicified sandstones are most abundant. They are cut by younger dikes of basaltic rocks. Mining of quartzites already ceased at Písečný vrch. The locality is protected as an archeological site (prehistoric mining of quartzites). At Verpánek, the quarry was partially filled up with a dump. Now it is recultivated. Another possible locality for protection is the diatreme of Milá and Odolický vrch, where maar sediments are likely to occur.