Jerzy Żaba

The Colca Valley in the Central Andes is a region characterized by the occurrence of large slow-moving landslides and a high level of seismic activity. In this study, we aimed to determine passive and active tectonic control on the formation of selected five large landslides in the Colca Valley and to assess geohazard associated with these features. For that purpose, we performed a post-landslide field survey, applied remote sensing techniques, and obtained eyewitness accounts. Recently, the need to understand mass movement processes in this region is even higher due to the establishment of the Colca y Volcanes de Andagua Geopark (Colca and Andagua Volcanoes Geopark). Our results suggest that the studied landslides usually represent a complex failure mechanism, dominated by translational sliding or rotational displacements, commonly associated with the formation of horst-and-graben like structures. We found a spatial correlation between the distribution of landslides and inherited fault network. The head scarps appear to be limited by the WNW- to NW-striking faults, whereas the lateral extent of some of the reported features seems to be connected with the NNE-striking normal faults, common in both, the Mesozoic strata and the Pleistocene-Holocene deposits.

Geophysical and geological data from the eastern sector of the Central European Variscan belt are presented and reviewed in the regional tectonic context. Matched filtering of isostatic gravity, guided by results of spectral analysis, along with other derivatives of gravity and magnetic fields reveal a dominant WNW–ESE-trending pre-Permian structural grain in the external zones of the Variscan belt in Poland. This trend is confirmed by regional distribution of dips in Carboniferous and Devonian strata that were penetrated by boreholes beneath Permian-Mesozoic sediments. Based on these data, two alternative concepts explaining the connection of the Variscan belt and its NE foreland, those of strike-slip tectonics versus oroclinal bending, are discussed. The WNW–ESE structural trend in the Variscan foreland is parallel to a set of major strike-slip fault zones in the area, including those of Upper Elbe, Intra-Sudetic, Odra, Dolsk and Kraków-Lubliniec. These faults are considered to convey a significant dextral displacement between Laurussia and Gondwana. The revised position of the Variscan deformation front shows a similar, uninterrupted, generally WNW–ESE trend, up to the SE border of Poland, which indicates an initial continuation of the Variscan belt into the area of the present-day Western Carpathians. The geometry of the Variscan deformation front along with the pattern of the Variscan structural grain are inconsistent with the idea of an oroclinal loop affecting the external, non-metamorphic Variscan belt. However, the data presented do not entirely rule out an oroclinal loop within the Variscan internides. The still possible options are (1) a semi-oroclinal model postulating ~ 90° bending of the Variscan tectonostratigraphic zones into parallelism with the WNW–ESE strike-slip faults or (2) an orocline limited only to the belt linking the Wolsztyn High and Moravo-Silesian non- to weakly-metamorphic fold-and-thrust belt. Regardless of the kinematic model preferred, our data indicate that structural evolution of the Polish Variscides was concluded with the end-Carboniferous NNE–SSW shortening that resulted in the present-day extent of the Variscan deformation front.

In situ gamma-ray measurements of 40K, 232Th and 238U in high-grade metamorphic rocks from the Sowie Mountains (Sudetes, SW Poland)

We aimed to determine variations in stress regimes during the youngest Variscan deformations in the northern part of the Bohemian Massif. For this purpose, we calculated the orientation of the principal stress and strain axes for kink folds observed in the metamorphic envelope of the Karkonosze Granite, using two methods: 1) the traditional method, incorporating structural diagrams (for conjugate kink folds only), and 2) butterfly diagram analysis. The use of both methods enabled us to determine the stress regime, based not only on conjugate but also on monoclinal kink bands. The obtained results prove that butterfly diagram analysis, when applied to monoclinal kink folds, yields reliable results, especially when calibrated using the internal friction angle (Ф) calculated for the conjugate structures. We identified two generations of kink folds: 1) an older one, developed under sublatitudinal shortening and most probably related to the Early Carboniferous terminal stages of the northwest-directed thrusting of the metamorphic units, and 2) a younger one; produced by north-south Variscan Carboniferous compression, and the emplacement and subsequent doming of the Karkonosze Granite. This is the first study on brittle-ductile structures observed commonly in the metamorphic units of the Bohemian Massif, showing their relation to the granitoid intrusion and complementing the tectonic models that usually omit kink folds.

The Zembrzyce Beds were studied to interpret the environments and facies in the western part of the Siary Subunit. New sedimentological data were obtained for the reconstruction of the depositional architecture of the Zembrzyce Beds. Based on detailed facies analysis, 9 facies and 4 facies associations were recognized. The facies associations represent different architectural elements of a submarine fan, such as: termination of distributary channel with transition to depositional lobe (distal part of mid-fan/outer fan sub-deposystem), lobes and distal lobes (outer fan sub-deposystem). According to the classification of Reading & Richards (1994) the fan deposystem can be classified as mud/sand-rich ramp. This system consists of several elongated lobes that formed synchronously, migrated laterally, and then retreated or decayed. The depositional system was supplied from the north and north-east. The inner-fan sub-deposystem was not detected. The sediments were deposited by high- and low-density turbidity currents and hyper-concentrated density flows sensu Mulder & Alexander (2001) with participation of the depositional background processes (pelagic settling). The sedimentary conditions of the Zembrzyce Beds during the Late Eocene were controlled by tectonic movements, the progress of the subduction and the global sea level changes.

Around 88% of the history of the Earth occurred during the Precambrian period, which can be subdivided into the Archaean and the Proterozoic eons (Figs. 2.1 & 2.2). The Archaean eon (Greek archaia — ancient ones; 4.56-2.5 Ga) comprises the Eo-Palaeo-, Meso-and Neoarchaean eras. For the early Archaean the term Hadean is also used (Greek hades — unseen or hell; 4.56-3.8 Ga) (Fig. 2.1). The Proterozoic eon (Greek proteros — first, zoon — creature; 2.5-0.542 Ga) is composed of the Palaeo-, Meso-and Neoproterozoic eras (Fig. 2.2). The latter eras can be subdivided into different periods defined by the International Commission on Stratigraphy on the basis of geochronological data and characteristic features such as particular geotectonic settings and events (Gradstein et al. 2004). Palaeoproterozoic periods include the Siderian (Greek sideros — iron; 2.5-2.3 Ga), the Rhyacian (Greek rhyax — steam of lava; 2.3-2.05 Ga), the Orosirian (Greek orosira — mountain range; 2.05-1.8 Ga) and the Statherian (Greek statheros — stable; 1.8-1.6 Ga). The Calymmian (Greek calymma — cover; 1.6-1.4 Ga), Ectasian (Greek ectasis — extension; 1.4-1.2 Ga), and Stenian (Greek stenos — narrow; 1.2-1.0 Ga) are the Mesoproterozoic periods, while the Neoproterozoic is subdivided into the Tonian (Greek tonas — stretch; 1.0-0.85 Ga), Cryogenian (Greek cryos — ice, genesis — birth; 0.85-0.635 Ga), and finally Ediacaran (0.635-0.542 Ma). This latter is named after the Ediacara Hills (Flinders Ranges, Australia) and characteristically contains the Ediacara biota which represents the dawn of evolved life-forms. The Ediacaran period

The natural radioactivities of five characteristic igneous rocks of the eastern foreland of the Opava Mountains (Eastern Sudetes, Poland), obtained in the laboratory and under in situ conditions, are presented. The activity concentrations of ²³²Th, ²³⁸U, and ⁴⁰K were measured using an HPGe gamma-ray spectrometry system. The ranges of the activity concentrations of ²³²Th were 7–71 Bq kg⁻¹ in the laboratory and 6–68 Bq kg⁻¹ for the in situ measurements. For ²³⁸U, the ranges of the activity concentrations were 5–52 Bq kg⁻¹ in the laboratory and 9–48 Bq kg⁻¹ for the in situ measurements, and for ⁴⁰K, the ranges were 520–1560 Bq kg⁻¹ in the laboratory and 537–1700 Bq kg⁻¹ for the in situ measurements. These determined activity concentrations were compared with the average activity concentrations of the radionuclides in similar types of rocks and with data from the Sudetes available in the literature. No significant differences were found between the in situ and laboratory measurements.

The Kaczawa Mountains along with the Kaczawa foothill comprise a complicated geological unit that is called the Kaczawa metamorphic (Sudetes, SW Poland). The aim of our work was to identify the iron-bearing minerals in samples of basalts and pillow lavas from the Kaczawa metamorphic using ⁵⁷Fe Mössbauer spectroscopy. Based on the preliminary results, the Fe³⁺/Fe²⁺ ratio in the samples was determined.