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 estimation of subsequent erosional rates.
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 Strombolian style mostly not producing lava flows. This volcanic activity took place mainly during Miocene.
The lavas of 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 weakly affected by weathering processes.
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. Erosion of Cretaceous marine deposits was intensive during Oligocene, whereas during the last 17 M.y. only some 70m of sediments were eroded.