Showing papers in "Geological Quarterly in 1987"

Ruchy masowe na zboczach zbudowanych z ilów krakowieckich (na przykładzie doliny Wisły i Sanu)

Abstract: Najbardziej charakterystycznymi typami powierzchniowych ruchow masowych na zboczach zbudowanych z ilow krakowieckich w dolinie Wisly i Sanu są klasyczne osuwiska, zsuwy i spelzywanie. O stateczności tych zboczy decydują przede wszystkim powierzchnie oslabienia i resztkowe parametry wytrzymalości na ścinanie. Okres stabilizacji zboczy w ilach krakowieckich zalezy od drenazu wod i w przypadku zboczy silnie zawodnionych jest on dlugotrwaly. MASS MOVEMENTS ON THE SLOPES COMPOSED OF THE KRAKOWIEC CLAYS (EXEMPLIFIED IN THE VISTULA AND SAN V ALLEYS) Almost on the whole area of the Krakowiec clays occurrence, the slopes of the great river valleys show the features of the slide origin morphology and recently in many places, significant activity of mass movements can be observed. Many years' observations of natural slopes of the Vistula Valley (between Baranow Sandomierski and Tarnobrzeg) and the San Valley (between Krzeszow and Zarzecze near Nisko) have given information on character and dynamics of slide process development in various geological conditions (including hydrogeological conditions) and on effects of the letter on the process of the slope stabilization. The paper presents the major conclusions resulting from analysis of the above dependences regarding to properties of the internal structure of the massif composed of the Krakowiec clays. The properties of the clays, particularly the over consolidated clays (to which the Krakowiec clays belong) depend on time. With lapse of time they absorb water and the primary mainly negative, pore pressure is subject to diffusion, the water content increases, and effective strength decreases. This picture is complicated by natural surface of weakening, both the sedimentation type and discontinuity type. The strength along these surfaces is close to the residual strength. The residual angle of internal friction ranges from 8 to 10° in the maximum value 16-18°. \ High sensiveness on egzogenic factors is a very important feature of the Krakowiec clays. Under the influence of cyclic drying and wetting they are subject to convert from soil of very good strength properties into the weathering soil eluvium with low strength parameters. The following major conclusions resulted from the investigation: 1. The most characteristic types of surface mass movements developed on natural slopes of the investigated river valleys are classica1 slides, weathering cover slides and creeps. 2. Surfaces of weakening and residual shear strength parameters determine mainly the stability of profiled slopes in the non-weathering Krakowiec clays. 3. The period of the slope stability in the Krakowio: clays depends on water drain. In case of highly watered slopes the process is longlasting. 4. No visible with deformations are observed on slopes with inclination less then 7-8°. These slopes are stable.

Zdarzenia na późnodewońskim szelfie południowej Polski i ich znaczenie stratygraficzne

Abstract: Analiza sekwencji facjalnych gornego dewonu i rejonu Debnika-Zawiercia, regionu kieleckiego i Lubelszczyzny wskazuje na wystepowanie pieciu waznych zdarzen geologicznych na obszarze zbiornika epikontynentalnego poludniowej Polski. Są to: podstawowa transgresja franska (dolny? podpoziom asymmetricus ), szybka transgresja poprzedzona regresją (dolny podpoziom gigas ), enigmatyczne zdarzenie na granicy franu z famenem (środkowy podpoziom triangularis ) i puls regresji (środkowy podpoziom crepida ). Wymienione epizody (niektore o wymiarze globalnym) charakteryzowaly sie krotkotrwalością w czasie geologicznym, porownywalną do trwania jednego podpoziomu konodontawego. Mialy one ponadto czytelny. choc zroznicowany w poszczegolnych strefach facjalnych. wplyw na sedymentacje. Zdarzenia te mogą stanowic zatem dogodną podstawe do precyzyjnej korelacji czasowej odleglych sekwencji weglanowych, co najmniej w obrebie badanej cześci basenu sedymentacyjnego. EVENTS ON THE LATE DEVONIAN SHELF IN SOUTHERN POLAND AND THEIR STRATIGRAPHICAL SIGNIFICANCE The present study is based on a comparison of facies sequences in the following three areas of the Late Devonian shelf in southern Poland: the Debnik-Zawiercie area near Cracow, the Kielce region in the Holy Cross Mts., and the Lublin area (Fig 1). These areas represent different tectonic and paleogeographic settings. This made possible sorting out a common developmental pattern from some purely local effects. The interpretation of the facies superposition within a framework of the standard conodont zonation allows one to distinguish five important geological events which occurred over the whole investigated shelf portion. 1. The basal Frasnian transgression (probably Lower asymmetricus Zone). This event is generally expressed as the contact of dark, dis-to anaerobic marly subtidal deposits with the underlying stromatoporoid·coral biostromal complex (localities Debnik, Klucze near Zawiercie and Minkowice 4a borehole; Fig. 2, Tab. 1). Locally, isolated organic buildups developed over biostromal platform; they range from small bioherms (Kowala) through kilometer-sized reefs (Dyminy Reef –l ocality Ostrowka, Bystrzyca 2 borehole 1). 2. The regressive pluse (Lower gigas Zone). The lithological evidence is variable: thick, coarse-grained intercalations within the basinal marly mudstones (Klucze, Kowala); rapid grain·size coarsening in the detrital units (Debnik); and karsted surfaces (Ostrowka). The fact that similar phenomena have not been so far described from the Lublin area is probably due to insufficient sedimentological and biostratigraphical analyses. 3. The transgressive event (Lower gigas Zone). Typically, this episode is evidenced by the marly mudstones with a pelagic fauna overlying the detrital deposits of the earlier regressive pulse (Debnik - Zawiercie, Kowala, Kadzielnia). Submerged reef-complexes were the sites of either nondeposition (Ostrowka ?) or condensed sedimentation of cephalopod limestones (Lublin area - Bystrzyca 2) and organodetrital limestones of a reef·cap type (Psie Gorki in Kielce). 4. The Frasnian/Famennian boundary event (Middle triangularis Zone). In the sections displaying continuous basinal development in late Frasnian to Famennian, the F/F boundary is either difficult to discern within a monotonous marly sequence (Kielce region) or it is marked by the abrupt decrease in carbonate to clay ratio (Zawiercie). The dead organic buildups display nondeposition (Ostrowka, Kadzielnia) which is reflected in stratigraphical gaps spanning an age interval ranging from two conodont subzones to more than a stage. 5. The regressive pulse (Middle crepida Zone). This event is marked by an appearance of intraformational erosion levels along with benthic skeletons, and by an increase in a carbonate content. Those phenomena were observed in the marginal parts of the basin (Debnik - Zawiercie, Lublin area) while they are hardly discernible in the Kielce region. The lithological record associated with the above events may be clearly distinguished in sections representing contrasting paleogeographical and facies settings (Fig. 2, Tab. 1). This ubiquity seems to be controlled mostly by a pattern of sealevel changes which is common for at least the investigated shelf area (Fig. 3). In fact, both transgressive episodes most probably had a world-wide occurrence (J.G. Johnson et aI., 1985); also the regressive pulses may have had an eustatic character. A global extent may be also attributed to the F/F event (D.J. Mc Laren, 1982). From the present analysis it is concluded that the major geological events may provide a useful basis for detailed chronostratigraphic correlations between various paleogeographic and facies areas of the Upper Devonian. The future application of the event·stratigraphic scheme should, however, involve refining of sedimentological and facies analysis of key sections.