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Pedogenesis was studied on clayey sandstones, calcareous sandstones, sandy marlstones and silty marlstones in the Bohemian Cretaceous Basin. These rocks were evaluated by petrography and X-ray diffractometry. The soils were characterized on the basis of a variety of analyses of organic and anorganic components. Soil formation proceeded predominantly under neutral and basic conditions. Calcaric Leptosols are of smaller thickness and less prominent pedogenesis than Cambic Leptosols. The main pedogenetic process in all soils is humification. A rapid reduction of the amount of organic matter in soil profiles is typical for soils on clayey sandstone and sandy marlstone. The content of organic matter decreases gradually down the soil profiles on calcareous sandstone and silty marlstone. The intensity of modern pedogenesis is higher in Cambic Leptosols developed on calcareous sandstone and silty marlstone compared to Calcaric Leptosols on sandy marlstone and clayey sandstone. This is due to the more balanced quartz/calcite ratio in the parent material (1.06 for calcareous sandstone, 1.51 for silty marlstone). It appears that the most important factor in Leptosol development is the parent material and that the development towards Cambisols can be hardly expected on silicate- carbonate rocks with a high proportion of quartz. [ABSTRACT FROM AUTHOR]

[Display omitted] Caves in coastal cliffs in the Apostle Islands were analyzed for factors controlling their origin and evolution. Even though the Bayfield Group quartz sandstones were found to be of relatively low tensile strength, the traditional explanation attributing speleogenesis to localized zones of lithological and tectonic weakness does not adequately explain all geomorphic features of the caves. The caves were found to be formed by coalescence of smaller arcade-shaped cavities serially developed along subhorizontal discontinuities. In concordance with the previously formulated "arcade principle", positions and shapes of the cavities are defined by areas of reduced stress within the gravity-induced stress field. Evacuation of material from the rock massif can be attributed to wave action including the effect of water-pressurized air, and frost action. Compound cavities above the discontinuities tend to form "higher-order" arcade-like cavities/caves while those beneath more resistant strata rather develop into elongated overhangs similar to ordinary coastal notches. Propagation of the largest cavities, formed along steeply dipping joints and faults, is attributed to mass wasting and roof collapses. Similar examples of discontinuity-related cavities in coastal settings, suspectedly also controlled by gravity-induced stress distribution, can be found worldwide, being mostly concentrated to areas covered by ice sheets in the Pleistocene. The interplay between post-glacial isostatic uplift and Holocene lake-level rise is responsible for the development of mature forms of coastal caves in the Apostle Islands where present cliffs are estimated to have been exposed to the effects of wave action for the last 3–5 ky. [ABSTRACT FROM AUTHOR]

The Lusatian Fault in the northern Bohemian Massif is one of the most prominent products of the latest Cretaceous to Paleogene thrusting in the Alpine foreland in Europe. Its fault plane dips to the N to NE, typically separating crystalline units in the N from Upper Paleozoic and Cretaceous units in the south. Crystalline units in Lusatia consist of Proterozoic to Lower Paleozoic rocks epi- to mesozonally metamorphosed during the Variscan Orogeny, cut by Cadomian and Variscan granitoid plutons. Anatomy of the fault was studied in outcrops and in a series of test trenches, and the course of fault trace in complex topography was used to determine the dip of the fault. Based on a detailed analysis of brittle structures accompanying the main fault, the Lusatian Fault Belt can be further subdivided into the fault core, zone of wall-rock brecciation, and the damage zone which also includes large-scale dismembered blocks and flanking structures. Other components of the fault belt originated in spatial association with the Lusatian Fault, during its formation (e.g., the drag zone and bedding-plane slips in the footwal 1-block sediments) or later, during its multi-stage evolution. A general dependence of fault belt architecture on the orientation of the fault plane to the acting stress can be demonstrated. With the NNE-SSW subhorizontal maximum principal stress calculated for the thrusting episode at the Lusatian Fault, less complex structures appear where the dip of the fault is shallower, and more complex structures including thicker damage zone and drag zone were formed where the fault was steeper. In flat fault segments, competent members of the footwall-block sedimentary package, whose bedding planes were sub-conformable to the fault plane, were sheared during the thrusting and dragged to near-surface levels as dismembered blocks. A progressive eastward increase in the fault dip angle is associated with the appearance of the zone of flanking structures in which the degree of rotation is a function of the fault dip angle. In the eastern part of the fault (fault dip angle of ~60°), the same stress acted at a high angle to the fault plane producing a "bulldozer effect". Limbs of the flanking structures were overturned, and a parallel, more gently inclined Frýdštejn Fault was initiated as a structure more advantageous for slip movement. [ABSTRACT FROM AUTHOR]

Dykes of the Late Cretaceous to Early Tertiary (79.5 ± 3.5 to 60.7±2.4 Ma) melilitic rock series of the Osečná Complex and the Devil's Walls dyke swarm, including ultramafic lamprophyres - polzenites - of Scheumann (1913) occur dispersed in the entire Upper Ploučnice River basin in northern Bohemia. Polzenites and associated melilitic rocks are characterized by the mineral association of olivine + melilite ± nepheline, haüyne, monticellite, phlogopite, calcite, perovskite, spinels and apatite. New data on their mineral and chemical compositions from original Scheumann's localities (the Vesec, Modlibohov, Luhov types) argue against the abolition of the group of ultramafic lamprophyres and the terms 'polzenite' and 'alnöite' by the Le Maitre (2002) classification. Marginal facies and numerous flat apophyses of the lopolith-like body known as the Osečná Complex show an olivine micro-melilitolite composition (lamprophyric facies). The porphyritic texture, chemical composition and the presence of characteristic minerals such as monticellite and phlogopite point to their affinity with ultramafic lamprophyres - polzenites of the Vesec type. Melilite-bearing olivine nephelinites to olivine melilitites (olivine + clinopyroxene + nepheline + melilite ± haüyne and spinels with apatite) form a swarm of subparallel dykes known as the Devil's Walls. The Scheumann's non-melilite dyke rock "wesselite", spatially associated with polzenites and often erroneously attributed to the polzenite group, is an alkaline lamprophyre of monchiquite to camptonite composition (kaersutite + phlogopite + diopside + olivine phenocrysts in groundmass containing clinopyroxene, phlogopite, haüyne, analcime, titanian magnetite, apatite ± glass/plagioclase). First K-Ar data show Oligocene ages (30.9± 1.2 to 27.8± 1.1 Ma) and an affinity to the common tephrite-basanite rock series. [ABSTRACT FROM AUTHOR]

Copyright of Archeologické Rozhledy is the property of Academy of Sciences of the Czech Republic, Institute of Archaeology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)