Journal of
GEOsciences
  (Formerly Journal of the Czech Geological Society)

Original Paper

Reconstruction of eroded monogenic Strombolian cones of Miocene age: A case study on character of volcanic activity of the Jičín Volcanic Field (NE Bohemia) and subsequent erosional rates estimation

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Abstract:
Relics of solitary volcanic edifices in NE Bohemia were newly interpreted as remnants of scoria cones and their conduits. Volcanic activity in this area occurred in a form of scattered Strombolian eruptions of basanitic magmas mostly ascending along E-W trending faults. Nearly all studied volcanoes erupted in similar style, Strombolian, mostly not producing larger lava flows. This volcanic activity took place mainly during Miocene (24.6-16.5 Ma). The lavas known on the Kozákov Hill were produced by much younger volcanic activity (6.7-3.5 Ma) and one of the studied locations is supposed to represent their feeder. The older Strombolian cones are relatively weakly affected by weathering processes. The erosional level at individual sites depends on geomorphology. On some of the edifices non-welded, poorly stratified scoriae are well preserved, at other sites a basal facies or upper vent facies were exposed by selective erosion. Interpretation of the exposed facies with the use of radiometric data brought new insight in relief evolution of this area. Erosion of Cretaceous marine deposits was very intensive during Oligocene, whereas during the last 17 M.y. only some 70 m of weak sediments were eroded.