NÁLEZY BADENSKÝCH FOSÍLIÍ V JESKYNI SVÁŽNÁ STUDNA, MORAVSKÝ KRAS – DŮSLEDKY PRO SPELEOGENEZI

Relatively rich macrofauna and microfauna of Badenian age was found in a depth of 25–32 m in a vertical cave Sváná studna (Moravian Karst). The cave was excavated downwards from a sinkhole situated at the foot of upper part of the valley (canyon). The lower part of the canyon is filled with more than 100m thick marine Badenian clays with horizons of volcanic tuffites. The stage of preservation of macrofauna and microfauna suggests very little or no transport and thus primary sedimentation in pre-Badenian cavities

Geological structure of the Macocha Abyss in the Moravian Karst on the basis of structural and stratigraphic research

The main concern of this study is the tectonics of the Macocha Abyss (Macocha Chasm) and a part of the Punkva Cave in the Moravian Karst. Two systems of subvertical faults with NNE–SSW and NW–SE strike are the most important for the genesis of the abyss. The third system (related to décollements) strikes NE–SW and dips 40 to 60 degrees to the SE. The intersection of these three systems was crucial for the collapse of the roof of the original cave dome and the genesis of the abyss. These structures were formed during the Variscan orogeny but modified during the Alpine orogeny. A 3D model of the Macocha Abyss based on a geodetic surveying is presented.The main concern of this study is the tectonics of the Macocha Abyss (Macocha Chasm) and a part of the Punkva Cave in the Moravian Karst. Two systems of subvertical faults with NNE–SSW and NW–SE strike are the most important for the genesis of the abyss. The third system (related to décollements) strikes NE–SW and dips 40 to 60 degrees to the SE. The intersection of these three systems was crucial for the collapse of the roof of the original cave dome and the genesis of the abyss. These structures were formed during the Variscan orogeny but modified during the Alpine orogeny. A 3D model of the Macocha Abyss based on a geodetic surveying is presented

Osmium and lithium isotope evidence for weathering feedbacks linked to orbitally paced organic carbon burial and Silurian glaciations

The Ordovician (∼487 to 443 Ma) ended with the formation of extensive Southern Hemisphere ice sheets, known as the Hirnantian glaciation, and the second largest mass extinction in Earth History. It was followed by the Silurian (∼443 to 419 Ma), one of the most climatically unstable periods of the Phanerozoic as evidenced by several large scale (>5‰) carbon isotope (δ13C) perturbations associated with further extinction events. Despite several decades of research, the cause of these environmental instabilities remains enigmatic. Here, we provide osmium (187Os/188Os) and lithium (δ7Li) isotope measurements of marine sedimentary rocks that cover four Silurian δ13C excursions. Osmium and Li isotope records resemble those previously recorded for the Hirnantian glaciation suggesting a similar causal mechanism. When combined with a new dynamic carbon-osmium-lithium biogeochemical model we suggest that astronomical forcing of the marine organic carbon cycle, as opposed to a decline in volcanic arc degassing or the rise of early land plants, resulted in drawdown of atmospheric CO2, triggering continental scale glaciation, intense global cooling and eustatic sea-level lows recognised in the geological record. Lower atmospheric pCO2 and temperatures during the Hirnantian and Silurian glaciations suppressed CO2 removal by silicate weathering, driving 187Os/188Os and δ7Li variability, supporting the existence of climate-regulating feedbacks

The earliest growth stages of amphiporids and archaeocyaths - a comparison

The initial growth stages of amphiporids and archaeocyaths are mutually similar to identical. They both consist of (1) rudimentary bottom disc (covered by small tubercles or septum-like bulges), (2) first chamber, (3) smooth first tube and (4) an interval with relatively rapid metamorphosis to complex adult morphologies. Probably no sponges can produce such an earliest skeletal formation that consists of the first chamber and tube, both resembling an external wall, because the typical sponge gemmules usually produce a number of cells that expand laterally very fast, forming a soft network, and it is a very different process. The great degree of similarity between the earliest growth stages of amphiporids and archaeocyaths suggests that there was a sharply separated group of "archaeocyathid-amphiporid" organisms (working name "Amphicyathida"), which was different from other corals, sponges or stromatoporoids

Koncepce devonských ostrovních elevací a vývoj porozit v macošském souvrství

Philosophy of the Devonian insular elevations (DIE) and evolution of porosity in the Macocha Formatio

Ekologické vazby ohledně endolitických producentů mikrovrteb a substrátů v barrandienských vápencích devonského stáří, Česká republika

The microboring activity in barrandian seas was generally low. It was limited by relatively cold geostrophic currents in outer parts, and the seafloors in inner basin depressions were also adversely influenced by stagnant d18O-positive and heavy-metal-rich bottom waters. The really flourished microborers were only in two stratigraphical intervals, and both have shown /"redbeds-like/" deposits. The first developed close with major end-Tippecanoe regressions in Praha sequence, and the second occurred in the Daleje-Trebotov sequence. These /"redbeds-like/" periods correspond mineralogically, geochemically and paleobiologically to relatively hot humid climates (~ mesotrophic but well oxygenated waters). It differed from other long intervals characterized by marine Corg and silica burial (cherts

Gamma spectrometric and magnetosusceptibility logs from the Frasnian platform limestones (Moravia): indications of their large correlation potential

The study develops two geophysical and interpretation concepts related to the reciprocal lowstand clastic and highstand carbonate sedimentation on Middle to Late Devonian carbonate platforms. The gamma spectrometric and magnetosusceptibility measurements document the lowstand episodes and major phases in dispersal of terrigenous weathering products. Six Frasnian cycles were tested for their global correlation capacity and environmental/paleoclimatic significance