Abstract Late Oligocene (ca 25 Ma) volcano‐sedimentary successions exposed on the western periphery of the Doupovské Hory Volcanic Complex reveal a complex sedimentation history influenced in various ways by decay of the alkali basalt volcanic edifice. Weathering of the volcanic rocks supplied abundant reactants that promoted carbonate precipitation in the peripheral palaeolakes—as evidenced by strongly non‐radiogenic 87Sr/86Sr values (0.7038–0.7041). On the other hand, the sediments of the initial shallow lake became deformed by the bulldozing effect of a debris avalanche. The debris flow and avalanche deposits filled up the original depression, modified the basin morphology and shifted the peripheral lacustrine setting further away from the volcano. At this stage, surface water influx from the surrounding granites conferred a more radiogenic character (87Sr/86Sr values 0.7046–0.7049) to the calcrete deposits. Fossil assemblages as well as limestone textures suggest significant seasonal water‐level fluctuations, possibly reflecting the alternating rainy and dry‐seasons of a prevalently humid Central‐European Late Oligocene climate. The seasonal drying out of the ponds resulted in significant 18O enrichments. Although the ca 0‰ δ13C values might suggest mixing of atmospheric and volcanic CO2 during carbonate precipitation, no active volcanic conduits of relevant age are known in the close vicinity. The lower δ13C values are likely a result of mantle degassing through rift faults, a phenomenon observed in the magmatically extinct Ohře Rift until present. This paper demonstrates that limestones derived from weathered alkaline basalts are characterised by highly non‐radiogenic Sr isotopic ratios (87Sr/86Sr ca 0.704), suggesting a magmatic origin for the Ca within these carbonates. Contrary to the notion of carbonatites being present when highly non‐radiogenic Sr isotopes are found, these results show that Sr isotopes in carbonates formed in alkali basalt‐sourced environments only reveal the source of the Sr (and Ca) ions, not necessarily the presence of carbonatite.

Fossilised remains of plants and animals can be found at many sites of volcaniclastic deposits and intravolcanic sediments (limestones, diatomites, lignite) of the České středohoří Volcanic Complex. Many of these localities have been known and studied since the 19th century. Some of these localities even gained international recognition due to abnormal abundance of fossil material. Collected and carefully stored paleontological material is still intensively studied with an aim to better understand the evolution of life but also environmental changes in Central Europe during Cenozoic. Combination of paleontology and volcanology has a potential to better constrain the paleo-environmental interpretations, as the two geological branches use different methods and gathered results can be confirmed by independent techniques. For this reason, our research focused on less-known paleontological locality at Starý Šachov, which provides interesting exposure documenting relations between volcanic activity, surrounding environment and biosphere during early stage of the České středohoří Volcanic Complex formation. The site Starý Šachov, also referred to as Malý Šachov (Radoň 2001), belongs to the basanitic Lower Oligocene Ústí Fm. of the České středohoří Volcanic Complex (sensu Cajz 2000) and is located at the northern margin of the České středohoří Mts. (Fig 1a). The Starý Šachov gorge exposes a sequence of pyroclastic rocks, capped with basanite lava (Fig. 1b), which was dated to 30.70 ± 0.45 Ma (K-Ar, bulk- rock). The pyroclastic sequence overlays redeposited volcaniclastic and intravolcanic sedimentary rocks (Fig. 1c). The volcaniclastic layers in the lower part of the sequence, where they alternate with intravolcanic sediments, consist of a mixture of basaltic epiclasts, and redeposited pyroclasts mixed with quartz and K-feldspar grains (Fig. 2a). This association suggests a short fluvial transport of volcaniclastic material from the growing volcanic complex, mixed with clastic material of the poorly solidified Merboltice Fm. sandstones representing the intimate bedrock of the locality. The pyroclastic sequence starts with deposits dominated by glassy non-vesiculated lapilli (Figs 1e and 2b, c) later replaced by deposits dominated by highly vesiculated lapilli (Figs 1d and 2d). The light-coloured sediments from the lower part of the succession contain abundant paleontological material. Clusters of white strongly flattened and crushed mollusc shells (Figs 3a, d, f, g) occur in whitish to light grey thinly bedded claystones. Together with molluscs, small cracked ostracod shells (Figs 4a–c) and caddisfly (Trichoptera) larval cases (Figs 4e, f ) are very abundant. Very rarely, twigs of plants from the Taxodiaceae family (Radoň 2001) and indeterminable leaf fragments were found. In dark coaly clays, undercut ostracod valves are abundant as well as in light coloured clays. Small rounded seeds of water lily-like plants (Fig. 4h) and fragments of frog bones (Fig. 4i) occur in larger numbers in the coaly clays. Gyrogonites of charophytes (Figs 4d, g) and only three shells of freshwater gastropods were found in the redeposited volcaniclastic layer underlaying the light clays. Unlike the compressed and crushed gastropod shells of the overlying clays, these three shells are spatially preserved. They belong to the species Planorbarius blazkai (Klika 1891) and Stagnicola sp.Based on the described taphocenosis, sedimentary and pyroclastic deposits we may reconstruct the paleoenvironment of this locality in Early Oligocene (Fig. 5). The landscape prior to the volcanic activity can be characterized as alluvial plain on the northern periphery of a growing volcanic complex. In this plain, braiding rivers were transporting and depositing volcaniclastic material as well as quartz grains of the poorly solidified Merboltice Fm. sandstones. Numerous oxbow lakes from abandoned meanders represented static water bodies. Such environment explains the observed biotic assemblages, dominated by flowing water preferring like trichoptera, with sporadic finds of static water elements like water lily-like plants, which may be either redeposited or reflect presence of minor static water bodies (oxbow lakes). The water rich environment is reflected also in the character of the subsequent volcanic activity. The phreatomagmatic pyroclastic deposits suggest that the eruption started in water- saturated environment (Surtseyan style eruption in a shallow lake or marsh) and later turned into the drier style (Strombolian) as the volcano emerged above the water body. The volcanic activity was terminated by lava emission.

A small, inconspicuous scoria cone in western Bohemia, known as Komorní hůrka Hill, played a crucial role during the controversy between Plutonists and Neptunists over the origin of rocks in the first half of the nineteenth century. The year 2017 represents the 180th anniversary of one successful resolution of this debate: at the instigation of J.W. Goethe, adits were dug into this volcano to access its feeding system in order to observe whether volcanoes were fed by burning coal seams, or feeder dikes of magma. The adits into Komorní hůrka Hill were the first large earth-works with a solely scientific goal and with no commercial mining purposes. The basaltic feeder exposed in the adits decided definitively in favour of the Plutonists after decades of ongoing arguments with the Neptunists. Here, we summarize the overall history of this small volcano. A recently conducted ground geophysical survey confirmed the position of historical adits, marked on several archive sketches. The geophysical data, comprising ground magnetometry, electric resistivity tomography and refraction seismic profiles, also revealed the internal structure of the volcano, including the position of the feeder dike and the geometry of a lava flow emitted from the crater. With the position of these historical adits confirmed by geophysical survey, excavations can safely reopen these historical earth-works and provide access to a wider public. Komorní hůrka could then serve as an educational geosite to exhibit the structure of a small monogenetic volcano, as well as illustrating a stage in the history of Earth Sciences.

The material of Machichnus regularis and Machichnus multilineatus was re-examined with respect to the potential tracemaker. New characters were defined for M. multilineatus – scratch profile with flat horizontal bottom and undulated microrelief of scratches. Based on these characters and additional information, both previously suggested tracemakers (beavers and porcupines) are rejected and a new one – a large squirrel is proposed. The squirrel origin of gnawing traces is additionally supported by actuopalaeontologic study on gnawing behaviour of recent red squirrels. On this basis, squirrels are recognized as overlooked but important taphonomic agents in Late Cenozoic assemblages. The tracemaker of M. regularis was not unambiguously recognized, but a connection with smaller squirrel or aplodontid species seems probable.

The Ahníkov (Miocene, Czech Republic) site represents a concentration of vertebrate skeletal remains in a swamp setting. Autochthonous bone deposits were strongly altered by sedimentary processes and early diagenesis. Biting and gnawing traces recognized on hard animal tissues (bones, teeth, antlers, turtle thoraces) represent seven recurring morphotypes. The following ichnotaxa are erected: Nihilichnus nihilicus n. igen. et n. isp., Nihilichnus mortalis n. isp., Machichnus regularis n. igen. et n. isp., Machichnus multilineatus n. isp., Machichnus bohemicus n. isp., and Brutalichnus brutalis n. igen. et n. isp. Each kind of bones or similar substrates bears a specific proportion of various bite traces but no observed morphotype is specific for a single substrate. Ethologically, traces of sharpening of teeth are principally different from predation traces. The beavers Steneofiber eseri and Steneofiber depereti, the carnivore Amphicyon sp. and the crocodiles are presumed as the tracemakers.