Pylova analyza sedimentarni vyplne byvaleho rybnika v udoli Bochovskeho potoka v Doupovskych horach

A biostratigraphic research of organic sediments on map sheet of Bochov (1 : 25 000, 11-241, an area along the southern edge of the Doupovské hory Mts., the Tepelská vrchovina Highland) was carried out within geological mapping of the Czech Republic. The Bochov (DM069, Fig. 1) locality was studied, and sediments (Figs 2–4) for pollen analysis were sampled. For time reasons only the most representative samples were chosen for the detailed palynological, paleoecological and stratigraphic studies. The most important and interesting sediments of the Bochov locality occur near the Bochovský potok Brook. The identified polen assemblages argue for the Holocene epoch: from the post-Middle ages to recent. The character of pollen spectrum indicates (see Fig.5) the time of sediment deposition after the High Middle Ages (High Medieval Period), and is approaching the recent (the youngest phase of the younger Subatlantic Xc period, stratigraphy modified according to Firbas 1949, 1952 – see Břízová – Juřičková 2011, Břízová et al. 2012, Břízová 2014). The origin of the water reservoir cannot be stratigraphically fully dated, because it was impossible to collect samples for analysis from the base of the Quaternary sediment due to high groundwater level. It is widely believed that local ponds were mostly founded in the 16th century. The pollen analysis tentatively dates the sediments to have been deposited in the 17th -18th century which is also reflected in the pollen spectrum. The most likely woody species that grew in the area were pine forests with an admixture of broad leaved woody species. Alders (Alnus) and willows (Salix) grow along local streams. Human activity is indicated by an occurrence of mostly common crops such as major wheat (Cerealia T. Triticum), rye (C. T. Secale) and other undistinguished corn species. They are accompanied by weeds such as Centaurea cyanus (corn flower), common corncokle (Agrostemma githago), etc. The results of pollen analysis are used for the reconstruction of vegetation evolution in the Doupovské hory Mts. From geological point of view there exist very favourable conditions for founding ponds. The relief is slightly undulating with occasionally preserved paleorelief on the watershed between the Ohře and Berounka rivers. The basement is built mostly by garnet paragneiss with kyanite, and on the surface there occur weathering residues of fossil kaolin, coloured to red, being up to a few metres thick. These can be observed on a large part of the area, being covered by clayey tuffs- a clastic sequence up to several metres thick, forming impermeable beds in depressions. This article is intended to contribute to the basic research of the Quaternary. The sediments of water reservoirs (ⁿQ) can be found virtually on each map sheet, but such a well-preserved sedimentary filling, suitable for biostratigraphic studies, has not been documented so far. This work highlights the practical importance of sediments in water reservoirs from the viewpoint of regional geological studies and suggests possibilities of their further investigation. Palynological dating brings data on the development of the youngest Holocene sediments originated in historical times.

References

Břízová, E. (2014): Nové poznatky o výskytu organických sedimentů stáří pozdní glaciál-holocén v České republice. – Zpr. geol. Výzk. v Roce 2013, 47–54.

Břízová, E. – Juřičková, L. (2011): Could canopy forests survive agricultural colonization in the Polabí lowland (Czech Republic)? – Bull. Geosci. 86, 2, 283–300. DOI 10.3140/bull.geosci.1260. View article

Břízová, E. – Pazdur, A. – Piotrowska, N. (2012): Upper Holocene development of vegetation and radiocarbon dating in the vicinity of the Cerhovka brook (Bohemian-Moravian Uplands, Czech Republic). – Geochronometria 39, 4, 251–262. DOI 10.2478/s13386-012-0016-2.View article

Dohnal, Z. – Kunst, M. – Mejstřík, V. – Raučina, Š. – Vydra, V. (1965): Československá rašeliniště a slatiniště. – 336 str. Nakl. Čs. akad. věd. Praha.

Erdtman, G. (1954): An introduction to pollen analysis. – 239 str. Chron. Bot. Comp. Waltham.

Firbas, F. (1949, 1952): Spät- und nacheiszeitliche Waldgeschichte Mitteleuropas nördlich der Alpen. I. Allgemeine Waldgeschichte. II. Waldgeschichte der einzelnen Landschaften. – 480 str., 256 str. Jena (Fischer).

Fuksa, V. (1968): Zpráva o průzkumu rašelinných ložisek v kraji Západočeském. – Exped. skupina průzk. půd, Čes. akad. zeměd. Praha.

Hradecký, P. – Matějů, M., ed. (v tisku): Příroda a krajina Doupovských hor.

Chytil, J. – Hakrová, P. – Hudec, K. – Husák, Š. – Jandová, J. – Pellantová, J. (1999): Mokřady České republiky – přehled vodních a mokřadních lokalit České republiky. – 328 str. Čes. ramsar. výbor. Mikulov.

Mlčoch, B. – Břízová, E. – Havlíček, P. – Rapprich, V. – Šebesta, J. – Verner, K. – Skácelová, Z. – Knésl, I. – Hrazdíra, P. – Sidorinová, T. – Skácelová, D. – Janderková, J. – Kycl, P. – Martínek, K. – Godány, J. – Kramolišová, P. (2014a): Vysvětlivky k základní geologické mapě ČR, list 11-241 Bochov. – 150 str. MS Čes. geol. služba. Praha.

Mlčoch, B. – Rapprich, V. – Šebesta, J. (2014b): Základní geologická mapa České republiky 1 : 25 000 s Vysvětlivkami, list 11-241 Bochov. – MS Čes. geol. služba. Praha.