Heavy mineral suites in Oligocene-Miocene sediments (Fore-Sudetic Monocline, SW Poland): Provenance signals versus weathering alteration

Julita Biernacka

Institute of Geology, A. Mickiewicz University, Maków Polnych 16, 61-606 Poznań, e-mail: julbier@amu.edu.pl

Key words:  heavy minerals, provenance, weathering, Oligocene, Miocene, Fore-Sudetic Monocline

Abstract
The paper describes the diversity of the heavy mineral suites in the Oligocene and Miocene sediments that were deposited in the foreland of the Sudetic part of the Bohemian Massif. The observed mineral variability is the result not only of changes in sediment transport directions, but also of chemical weathering and hydrodynamic sorting of the minerals by density. All the heavy mineral assemblages lack olivines, pyroxenes and amphiboles, i.e. chemically unstable minerals. Moreover, the terrestrial sediments are impoverished in non-resistant heavy minerals in comparison to the marine ones.
The central and eastern part of the Fore-Sudetic Block and, from the Middle Miocene, a part of what are now the Sudetes Mts. constituted the main source areas supplying detrital material to the Fore-Sudetic Monocline. Generally, the heavy minerals document a gradual lowering of the western fragment of the Meta-Carpathian Arch separating the North-West European Basin from the Paratethys, and a distinct shift in source areas delivering detrital material to the basin in the Middle Miocene. Furthermore, a pyroclastic origin for some heavy minerals from the sands/silts of the Middle Miocene Mużaków formation is suggested.

Geologia Sudetica, 36: 21-38.

Fluvial sedimentation of sandy deposits of the Słupiec Formation (Middle Rotliegendes) near Nowa Ruda (Intra-Sudetic Basin, SW Poland)

Leszek Kurowski

Institute of Geological Sciences, University of Wrocław, Pl. Maksa Borna 9, 50-204 Wrocław, Poland   e-mail: lkur@ing.uni.wroc.pl

Key words:  arid climate, lithofacies analysis, fluvial environment, terminal fan, palaeochannel, Sudetes

Abstract
The sandy sediments described in this paper are the lower, approximately 400-meter-thick part of the Słupiec Formation, which is part of lower Permian clastic deposits in the Intra-Sudetic Basin. At their base, the sandy deposits of the Słupiec Formation are bounded by fine-grained lacustrine sediments known as the Upper Anthracosia Shale (Krajanów Formation); upwards, they pass into the Walchia Shale (the upper part of the Słupiec Formation), also regarded to be of lacustrine origin. These sandstones consist chiefly of sublithic to subarkosic arenites and wackes. In places, polymictic conglomerates and fine-grained sediments, and also sublithic to subarkosic mudstones occur. These sediments form a structurally varied facies assembly, presumably fluvial in origin. An analysis of the vertical sequence of lithofacies revealed a distinct tendency towards the formation of simple cyclical sequences with the grain fining upwards and with a distinctly expressed asymmetry in favour of 'high-energy' medium- and coarse-grained facies. The oscillation tendency was marked only in 'low-energy' fine facies, which are sparsely represented in the sequence. The paleochannel analysis yielded results compatible with the outcome of the lithofacies analysis. The paleochannels are very shallow in relation to their width, and have a planar, erosional bottom configuration, and in places a terrace bank morphology. The fluvial system features described here may indicate a terminal fan environment as the possible depositional location place of the Słupiec Formation sandy sediments. The source areas were located at the S and SE margins of the Intra-Sudetic Basin, and the flow was towards the W and NW towards its centre, to shallow inland basins, probably of a playa type. The red colour of the sediments may be indicative of arid or semi-arid climatic conditions in this environment during the Middle Rotliegendes .

Geologia Sudetica, 36: 39-51.

In situ growth of monazite in anchizonal to epizonal mudrocks: first record from the Variscan accretionary prism of the Kaczawa Mountains, West Sudetes, SW Poland

Ryszard Kryza*, Jan A. Zalasiewicz**, Norman Charnley***, Antoni E. Milodowski****, Joanna Kostylew* & Rafał Tyszka*

* Institute of Geological Sciences, University of Wrocław, Cybulskiego 30, 50-205 Wrocław, Poland, e-mail: rkryza@ing.uni.wroc.pl;
** Department of Geology, University of Leicester, University Road, Leicester, LE1 7RH, UK
*** Department of Earth Sciences, University of Oxford, Park Roads, Oxford, OX1 3PR, UK
**** British Geological Survey, Kingsley Dunham Centre, Keyworth, Nottingham, NG12 5GG, UK

Key words:  monazite, mudstone, mélange, diagenesis, cleavage formation, low-grade metamorphism, Kaczawa Complex, Sudetes

Abstract
We report the first occurrence of diagenetic or low grade metamorphic monazite from the Palaeozoic mudrock successions of the Kaczawa Complex of the West Sudetes, Poland. Where observed in relation to the enclosing mudrock, this monazite comprises tiny irregular grains, less than 20 microns in diameter, intergrown with the surrounding matrix minerals. This monazite resembles previously described examples of diagenetic monazite from elsewhere in the world in mostly possessing low contents of Th and U but differs in forming much smaller grains, which show only slight zonation of rare earth elements (REEs). Some of the monazite grains studied also appear to have formed synchronously with the cleavage, perhaps a function of early deformation and fluid release in an accretionary prism environment. Relatively Th-rich cores, and an association with altered detrital biotite in some instances, suggests that at least some of the in situ monazite growth might have taken place as overgrowths on primary detrital monazite particles.

Geologia Sudetica, 36: 53-66.

Late Carboniferous weathering and regolith at the Kudowa Trough, West Sudetes: palaeogeographic, palaeoclimatic and structural implications

Czesław August & Jurand Wojewoda

Institute of Geological Sciences, Wrocław University, ul. Cybulskiego 30, 20-205 Wrocław, Poland; e-mail: august@ing.uni.wroc.pl, juwo@ing.uni.wroc.pl

Key words:  granite, saprolite, clay minerals, kaolinite, mixed-layer I/S, fault, tectonic block, Sudetes

Abstract
In the marginal part of the Kudowa Trough, on the border of Carboniferous granite and Permian (Saxonian) sediments, features typical for the profile of chemical weathering occurring in a regolith type sequence are described. Previously this border was interpreted as a tectonic fault. According to the authors, location of the initial cataclastic zone, followed by weathering of granite, is incidental. The extent of soil, its structural features and mineralogy are indicative of weathering in moderate-to-warm and humid climate conditions. Stratigraphic position of soil and its regional palaeogeographical and palaeoclimatic context make it possible to assume Late Westphalian (B and C, about 313-311 Ma) as the oldest, most likely beginning date of the weathering process. This opinion does not exclude the possibility of reactivation of weathering processes in Kudowa granite in the Early Cretaceous or even in the Triassic.