GEOLOGICAL SETTING

The Doupov Mountains are an important region of Cenozoic volcanic activity in the Bohemian Massif. They are situated in the Ohre River rift, a northeast-southwest trending volcanic zone developed adjacent to crystalline complexes of various ages. The Doupov Mountains composite stratovolcano covers more than 500 km2. The rocks forming this volcano are mostly basaltic with non-olivine tephrites to foidites prevailing over olivine composition. Trachytoid intrusive bodies occur at several localities, especially at the margin of the volcanic complex. The ratio between massive rocks and volcanic clasts is about 1:4.

Geologic investigation in this region started at the beginning of the last century. Hibsch (1901) first described the stratovolcanic setting. Kopecky wrote his dissertation on the southern part of the area during the late 1940s and compiled regional data during the 1950s and early 1960s for a 1:200 000 scale geologic map. The central part of these mountains became a restricted military area in the post-war period and since 1968 has been strictly closed to access except for marginal areas, restricting geological research until the last few years.

New data indicate a crater vent near the location where the small town of Doupov used to be, in the central part of the mountains. The vent is filled with syenitic rock. Other eruptive vents have been identified in this complex, including a number of parasitic vents whose necks are found scattered throughout the complex. The central area near Doupov has a caldera-like shape modified by erosion. Multiple stages of eruption are indicated by varying genetic composition as is seen in other well-explored volcanic complexes of the Ceské Stredohorí Mountains.

The Doupovské Hory volcanics have a preserved maximum thickness of about 500 m. The alternation of subaerial lava flows interbedded with volcaniclastic deposits is the main feature of this complex. Reworked pyroclastic rocks are common. Several sedimentary processes have been recognized including lahars, fluvial, and lacustrine deposition, especially in the marginal parts of the complex. Many volcaniclastic deposits show secondary carbonate deposition. Fine-grained reworked tuffs with admixtures of non-volcanic material preserved the fossil flora and fauna.