Tracing the Eocene–Oligocene transition: a case study from North Bohemia

Abstract

Geology and palaeontology of the Roudnky area, situated between the Most Basin and the esk stedoho Mountains in North Bohemia, the Czech Republic, is treated in detail. The volcano-sedimentary structure underlying the basin with the included fossiliferous layers is newly interpreted as a maar-diatreme. The radiometric age of the basalts was determined to 35.4 0.9 Ma and 37.1 0.9 Ma -late Eocene, Priabonian. The fish fauna consists of amiids characteristic of other adjacent late Eocene sites while the co-occurring macroflora includes many elements that are typical of the Oligocene. Closest relations are to the fauna and flora of the Vtrue Hill at st nad Labem. Based on palaeoclimatic estimates the major turnover from subtropical to warm-temperate climatic regimes in North Bohemia appears to have initiated in the late Eocene by an increase of seasonality and the resulting vegetation change from the evergreen to mixed mesophytic forest types well before the maximum temperature drop of mean annual temperature at ca 33.5 Ma.