Structural interpretation of semi-detailed magnetotelluric survey in Kamienica Dolna-Gogołów area in the Polish Outer Carpathians

Semi-detailed magnetotelluric sur vey was carried out in the area between Kamienica Dolna, Gogołów and Łopuchowa in the Polish Outer Carpathians. Magnetotelluric soundings were made along three lines located in a zone of the tectonic loop in the Carpathians' basement, which is reflected by the distribution of flysch outcrops. The sounding sites along profiles were ca 1.5 km apart. Magnetotelluric data were measured with the use of MT-1 system. To eliminate the effects of electromagnetic noise, the magnetic field remote reference was applied. Measurement data were processed using standard procedures of remote reference processing. Quantitative data interpretation was made with the use of 1D LSQ inversion. Initial geoelectric models were constructed basing on geological cross-sections obtained from surface and borehole data. 2D resistivity cross-sections, obtained from MT data interpretation, allowed the general structure of the flysch cover and its basement to be identified. Two major high-resistivity horizons were related to the top of Meso-Palaeozoic and Precambrian basement. A low- resistivity layer, related to the Lower Palaeozoic sediments, was interpreted

Provenance of Lower Cretaceous deposits of the western part of the Silesian Nappe in Poland (Outer Carpathians) : evidence from geochemistry

The turbiditic to hemipelagic, fine-grained deposits of the Hradiště Formation (Hauterivian, 132 Ma) to the Lhoty Formation (Albian-Cenomanian, 99 Ma) in the western part of the Silesian Nappe (Polish Outer Car- pathians) were studied mineralogically and geochemically to determine if the main factors controlling the che- mistry of the sedimentary material can be attributed to provenance, or to post-depositional processes. A high degree of weathering of the source rocks is indicated by the chemical index of alteration (CIA) that varies from 75.98 to 89.86, and Th/U ratios (~4 with outliers at 1.85 and >6). The co-occurrence of rounded and unabraded grains of zircon and rutile, the enrichment in Zr and Hf, as well as the high Zr/Sc ratios suggest that the Hradiště and Veřovice Formations contain recycled material. Plots of La/Th versus Hf and Th against Sc show that samples occur in the field of felsic and mixed felsic/basic sources. On a ternary La-Th-Sc diagram, all of the sediments studied are referable to the continental island-arc field. The European Plate, as an alimentary area, has a mosaic structure consisting of Cadomian and Variscan elements. The Proto-Silesian Ridge was detached from the conti- nent, because of rifting. Therefore, it could have corresponded to a continental island arc. The concentrations of Fe and trace metals (e.g., Mo, Au, Cu) in the Veřovice Formation and silica and potassium additions to the Veřovice and Lhoty Formations, as well as the fractionation of REE, and Nb, Ta, Zr, Hf, and Y can be explained by the action of basinal brines. The fluids were of hydrothermal origin and/or were released, owing to the dewatering of clay minerals. Diagenetic processes could have exerted a greater influence on sedimentary rock chemistry than the provenance and sedimentary processes. A distinction between primary, terrigenous elements and those changed diagenetically is necessary for the reliable determination of provenance

Provenance and diagenesis of siliciclastic and organic material in the Albian-Turonian sediments (Silesian Nappe, Lanckorona, Outer Carpathians, Poland) : preliminary studies

The provenance and diagenesis of the siliciclastic and hemipelagic sediments of three lithostratigraphic units: Lhoty Formation, Barnasiówka Radiolarian Shale Formation (BRSF) and Variegated Shales from Lancko- rona area, Polish Outer Carpathians, was approached by means of petrological and geochemical analysis of the representative samples. Data show that studied succession was mainly derived from two sources: 1. a dominant terrigenous fine-grained components have affinity with average upper continental crust (basing on mineral detritus, K2O/Rb ratio and Y/Ni vs. Cr/V ratios) and 2. biogenic siliceous material and macerals. Composition varies up section and accounts for changes in the detrital supply due to eustatic sea-evel changes. Organic petrology shows presence of organic detritus within the Lhoty Fm and dominance of marine-derived macerals in the BRSF. Chemical and petrological features imply a progressive deepening of the basin. The studied succession was diagenetically altered (e.g. coalification of bituminite, illitisation of smectite and pyritisation)

Soft-sediment deformation structures in seismically affected deep-sea Miocene turbidites (Cilento Basin, southern Italy)

Soft-sediment deformation structures (SSDS) are widespread in the upper part of the S. Mauro Formation (Cilento Group, Middle-Late Miocene). The succession is represented mainly by thick and very thick, massive, coarse-grained sandstones, deposited by rapid sedimentation of high-density turbidity currents. The most common SSDS are short pillars, dishes, sedimentary sills and convolutions. They occur mostly in the upper parts of sandstone beds. Vertical tubes of 4-5 cm in diameter and up to 50 cm long constitute the most striking structures. They begin in the middle part of sandstone beds, which are basically massive or contain faint dish structures. These tubes can bifurcate upwards and/ or pass into bedding-parallel veins or dikes. The vertical tubes sometimes form sand volcanoes on the then sedimentary surface. The SSDS are interpreted as the result of earthquake-triggered liquefaction and/or fluidisation of the turbidites that were affected by the seismic shocks. This implies that the deformed layers should be considered as seismites

Geodynamic evolution of the orogen : the West Carpathian and Ouachitas case study

Twelve time interval maps have been presented which depict the plate tectonic configuration, paleogeography and lithofacies for the circum-arpathian area from the Late Carboniferous through Neogene and for the circum-Ouachita region from Late Cambrian through Early Permian. The following geodynamic evolutionary stages can be distinguished in these two orogens: Stage I - rifting of terranes off the major continent, forming oceanic basins (Triassic-Early Cretaceous in the Carpathian region, Cambrian-Devonian in the Ouachita region); Stage II - formation of subduction zones along the active margin, partial closing of oceanic basin, development of deep-water flysch basin associate with this rifting on the platform (passive margin) with the attenuated continental crust (Late Cretaceous-Paleocene in the Carpathian region, Early Carboniferous in the Ouachitas); Stage III - collision, perhaps terrane-continent, with the accompanying conver- gence of two large continents, development of accretionary prisms, Eocene-Early Miocene time in the Carpathian region, Late Carboniferous in the Ouachitas; and Stage IV - postcollisional, (Miocene-Present-future? in the Carpathians, Permian-Triassic in the Ouachitas). Both, Carpathians and Ouachitas are accretionary prisms formed in response to terrane-continent and continent-continent collision. The paleogeographic approach we have taken shows how these mountain belts were constructed through the orogenic cycle, which reflects complex plate tectonic processes. Carpathians and Ouachitas record complete and homologous Wilson cycle