Glacifluviálně-glacilakustrinní sekvence u Vidnavy na severním okraji Žulovské pahorkatiny

Glaciofluvial and glaciolacustrine sediments were discovered in a small sandpit situated 800 m SE from Vindava (the Polský kopec Site). Sediments fill two channels located in superposition. Three facies associations (FA) were distinguished in this sedimentary section. The base of the lower channel is formed by gravel lag overlain by gravel-sandy sediments of 3-D dunes and a side bar (FA1). The upper channel infill begins also by basal lag and grades to a fining-upwards sequence from sand to silt (FA2). The sequence is formed from the base up by sediments of small 3-D dunes, A-type ripples, B-type ripples, C-type ripples, and horizontally laminated sediments. The sequence reveals a vertical transition from glaciofluvial (sand) to glaciolacustrine (silt) sedimentation. The sedimentary section is terminated by flat glaciofluvial bedforms (FA3) deposited under upper plane bed conditions. These bedforms arose after the restoration of glaciofluvial conditions. The base of the glaciolacustrine sequence is located at an altitude of ~ 275 m as well as the Old Kaolin Mine Site (850 m SW from the Polský kopec Site) where very similar sediments have been already described. The sediments of both localities represent a proglacial outwash plain in front of the retreating ice sheet (FA1 consists of ~ 23% of erratic rocks), where a relatively large lake, or a system of smaller lakes evolved at the same time.

Faunistické společenstvo kroměřížského souvrství na lokalitě Litenčice (karpatská předhlubeň, střední Morava)

The fossil assemblages of the foraminifers, bryozoans, molluscs, corals, decapods, sharks and teleosteans were analysed from the Litenčice sand pit in the middle part of the Carpathian Foredeep. The section can be assigned to the Karpatian Stage of the Central Paratethys regional stratigraphy (uppermost Lower Miocene) on the basis of species Uvigerina graciliformis Papp et Turn., Lampanyctus carpaticus (Brz.) and Agapilia pachii (Hoern.). Rich and diversified assemblages indicate mainly shallow water marine environment. Foraminifers and molluscs indicate salinity perturbations. Bryozoans and also molluscs document environment with relatively high dynamics and depth of water about 100 m. Foraminifers, fishes and sharks represent deeper water taxa and indicate a possible reworking of shallow-water elements. The studied sands and gravels of the Holešov Member of the Kroměříž Formation are interpreted as sediments of gravitational currents, more precisely dense turbidity currents (high-density turbidity currents) in the sense of Lowe (1982). The deposition environment can probably be placed on the submarine slope of the coarse-grained delta of the Gilbert type (so-called foresets). This study provided evidence of a number of fossil groups that occur at the site.

Orientace puklin a zlomů v kulmských horninách jižně od Skalky u Prostějova

Tento článek informuje o výsledcích studia orientace křehkých poruch (puklin a zlomů) provedeného v prostoru jižně od Skalky u Prostějova. Tento prostor je situován na východním okraji Českého masivu v blízkosti kvasického zlomu. Křehké poruchy byly studovány zejména v kulmských horninách, sada deseti strmých puklin byla zjištěna také na lokalitě miocenních klastik. V kulmských sedimentech bylo rozlišeno několik systémů strmých až subvertikálních křehkých poruch (především puklin), na některých lokalitách byly pozorovány také mírně až středně ukloněné diskontinuity. Některé plochy byly tektonizované. Na lokalitě SP09A (v lomu severně od Pivína) byl pozorován relativně významný strmý zlom (horizontální posun) směru SSZ-JJV, který je pravděpodobně součástí zlomové struktury tvořící východní tektonické omezení vystouplého bloku kulmských hornin jižně od Skalky.

Hydrotermální karbonáty a termometrie žilné mineralizace v terciérních vulkanitech u Uherského Brodu

Hydrothermal mineralization in the Bučník quarry near Uherský Brod is the best locality for the study of this type of mineralization in the Outer Western Carpathians. The studied sulfide vein mineralization is genetically linked to Tertiary volcanics and represents a distance manifestation of the same vein type in the metallogenetic region of the Central Slovakian Volcanic Field.Study of vein structure, ore textures and structures, chemical composition of carbonates, isotope thermometry (isotopic composition of sulfur sphalerite/galena) and fluid inclusions, including microthermometry, shows that mineralization occurred under complex and variable conditions. Carbonates, defined as calcites with a proportion of Fe and Mn, dolomites and Fe- and Mn-dolomites, Mg-ankerites, show a highly variable chemical composition clearly documented as fine zones in CL-microscopy and BSE images.Fluid inclusions contain the aqueous system H2O-NaCl and H2O-NaCl + MgCl2 + FeCl2-3. Fluid salinity ranges from 2.7 to 14.7 mass% NaCl eq. whereas it is higher for sphalerite than for carbonates. The same trend is for homogenization temperatures in the range of 121-272 °C.Isotopic thermometry in combination with microthermometry shows a relatively wide probable range of temperature conditions. The younger carbonate mineralization may begin at temperatures of 125 °C and around 200 °C may overlap with a temperature of sulfide association that ranges from 170 °C to 335 °C. Isotopic thermometry also suggests possible higher temperatures up to 450 °C and above, but these highest temperatures are rather unlikely. The wide temperature range in which the mineralization originated is in accordance with the development of the hydrothermal system in a very dynamic environment in terms of tectonic, magmatic and hydrothermal. The studied hydrothermal system has a number of physico-chemical parameters similar to vein systems in the Central Slovakian volcanics region.

Reflexně seismický výzkum pozdně kenozoické zlomové tektoniky na vybraných lokalitách hornomoravského úvalu

We measured shallow reflection seismic profiles across the assumed faults in the Late Cenozoic (Pliocene – Holocene) Upper Morava Basin (UMB). The faults in the UMB are indicated by horst-and-graben morphology, differential thickness of Pliocene and Quaternary siliciclastic sediments, considerable gravity gradients a present-day seismicity. Four seismic lines, 380 to 860 m long (fixed geophone spread) were designed to cross the assumed faults at three sites, Mezice, Drahlov and Výšovice. The data were acquired by 24-channel ABEM Terraloc Mk-8 seismic system with PEG-40 accelerated weight drop source and processed by Sandmaier ReflexW and Halliburton Landmark ProMax® seismic processing software. The processing included application of filters (DC shift, scaled windowgain, bandpass frequency and muting), stacking using normal moveout constant velocity stack, additional application of subtrack-mean (dewow) filter, topographic correction and low velocity layer static correction. Distinct reflectors were detected up to 400 ms TWT, which corresponds to maximum depth of 280 and 350 m at 1400 and 1750 km.s-1 velocities, respectively. The observed reflection patterns were classified into three seismic facies, which were interpreted as crystalline rocks (Brunovistulicum) and/or well consolidated Paleozoic sedimentary rocks (SF1), unconsolidated Quaternary siliciclastic sediments (SF2) and semi-consolidated Neogene clays (SF3) based on the cores drilled in their close vicinity. Distinct faults were observed at the Drahlov and Výšovice 2 profile, which coincided with the observed topographic steps between the horsts and grabens. Presence of the fault at the Drahlov profile separating the Hněvotín Horst from the Lutín Graben was demonstrated by independent electrical resistivity tomography profile. On the other hand, another topographic step at the Mezice profile, between the Hněvotín Horst and Olomouc Graben, does not correspond to any seismic indication of a fault. The reflection seismic proved to be useful and relatively low-cost method to visualize the shallow subsurface geology in the Upper Morava Basin.

Holocenní sedimentární pánev mezi Židlochovicemi a Blučinou na severozápadním okraji Výhonu

The studied area is located in a small basin between between Strže („Cézavy“) and Výhon hills. The „Cézavy“ site is an important Bronze Age enclosed settlement. Geological setting was examined by coring and electric resistivity tomography. Selected horizons were dated by C14 method. Holocene infill of basin is composed of two sedimentary units: intra-basin facies of dark coloured lacustrin-swamp clayey-silty sediments and marginal facies of clayey-silty-sandy sediments. Basin of assymetrical shape is deepest near foothill of „Cezávy“, where started infilling of basin as soon as ~3600 BP or earlier. The basin is delimited by bodies of Miocene rocks. Geochronological model shows existence of swamps-lacustrine basins in a time span since 17th century BC till 18th centuriy AD. It indicates, that main cause that filled the basin is individual landslides. Every landslide event caused new spatial configuration of basins and elevations. Last significant events were probably extensive, historically recorded landslides in 70‘s of 18th century. Recent morphology was formed as late as in 19th century.

Těžké minerály rozsypových ložisek zlata vázaných na khantaishirský ofiolitový komplex poblíž měst Altaj a Khaliun (jihozápadní Mongolsko)

Detailed morphological and chemical studies of heavy minerals from two localities fluvial sediments in the area of the khantaishir ophiolitic complex near the towns Altai and Khaliun (Southwestern Mongolia) allowed the interpretation possible source region for the gold. The heavy mineral spectrum from the sediments near the Altai town is dominated by magnetite (32 %), chromite (27 %), epidote (11 %), apatite (6 %), and clinopyroxene (5 %). We assume that these minerals come from the ultrabasic and basic igneous rocks in the Neoproterozoic khantaishir ophiolitic complex. The relatively undeformed and three-dimensional shape of gold particles indicating short distance their transport. Rare is native gold enclosed in dolomite or quartz, which indicates that potential gold sources are listvenite. The heavy mineral spectrum from the fluvial sediments in the small creek near the Khaliun town is different. The studied sample includes magnetite (31 %), amphibole (19 %), zircon (18 %), pyrite (13 %), apatite (5 %), epidote (4 %), titanite (4 %), clinopyroxene (2 %), monazite (1 %), ilmenite (1 %), garnet (1 %), and barite (0.1 %). Large variations in the mineral composition heavy mineral spectrum indicate a wide source area which includes basic to intermediate igneous rocks Cambrian-Ordovician Ikh-Mongol Arc System and medium-grade metamorphic rocks (metapelite). The subspherical rounded shape of the gold particles indicates fluvial transport. In the case of small and geologically simple drainage area as creek near the Altai town represents heavy minerals a good tool for determination of the origin of placer gold. There is a contrast between the heavy mineral spectrum from the localities near the Altai and Khaliun towns. The shape of gold particles as well as a simple heavy mineral spectrum from sediments near the Altai indicates short transport from the limited draining area (approximately 6 km2). Gold probably originating from the ultramafic rocks (listvenite), according to associated dolomite and simple spectrum of heavy minerals. Whereas the origin of gold from the placer deposits near Khalinun remains unclear and most probably could originate from the hydrothermal veins in intermediate or basic igneous rocks (presence of barite associated with abundant pyrite).

Vliv sedimentačního prostředí na magnetickou susceptibilitu přelivových sedimentů nivy Moravy ve Strážnickém Pomoraví

Four profiles in different sedimentary environments - natural levee, proximal floodplain, distal floodplain, oxbow lake - were sampled to obtain magnetic susceptibility (MS), grain size, organic matter content (LOI) and pH. Relationships between selected parameters (χlf, D50, LOI, pH) were analysed by means of statistical analysis (linear regression, PCA, factor analysis). Principal goal was to investigate how character of individual sedimentary environments and their distance from the active river channel is reflected in the magnetic signal of overbank deposits. A decrease in the magnetic signal with increasing distance from the river channel was shown, confirming that fluvial deposition is a major factor of contamination of floodplain sediments by anthropogenic magnetic particles. The base of elevated values of MS (levee: 80 cm, proximal floodplain: 30 cm) probably corresponds to the turn of the 19th and 20th century and the strongest magnetic signal (levee: 32,5 cm, proximal floodplain: 5 cm) belongs to the 1980s. Statistically significant relationships were found between: χlf and LOI (direct dependence), LOI and D50 (indirect dependence), pH and D50 (direct dependence) when data from all profiles were analysed together.