First evidence of Pinaceae and Fagaceae in the fossil wood record of the České středohoří Mts. (Czech Republic): A comprehensive study of fossiliferous sites in pyroclastic rocks surrounding the late Oligocene Milá stratovolcano

Abstract

A comprehensive anatomical and mineralogical study of fossil wood fragments from fields in the vicinity of Bečov and Břvany villages (NW Bohemia, Czech Republic) indicates that Taxodioxylon gypsaceum (Cupressaceae s.l.) predominates, but also identifies another coniferous wood: Pinuxylon parryoides (Pinaceae) and three angiosperms Quercoxylon böckhianum, Castanoxylon bavaricum and Lithocarpoxylon sp. (all Fagaceae). This paper therefore presents the first occurrence of Pinaceae and Fagaceae fossil wood in the volcanic rocks of the České Středohoří Mts. as well as its youngest palaeobotanical record in general, late Oligocene in age (26.56 ± 0.38 Ma). The samples were buried by alkaline pyroclastic deposits and were mineralized by carbonates. Two distinct depositional processes burying the fossil woods were identified. Closer to the vent, the woods occur in a near-vent pyroclastic fall deposits of the former pyroclastic cone, whereas more distant sites consist of pyroclastic flow deposits. Carbonate mineralization mostly consists of dolomite, but subordinate amounts of magnesite (likely the first time this is documented in fossil wood) as well as calcite and siderite are present. Only one sample collected in the same area, bearing clear signs of riverbed transport (Lithocarpoxylon sp.), was perfectly silicified, but its origin remains unclear.