Miscellanea Geographica 11 KGE, ZĆU v Plzni, 2005 Research paper

The terrace system on the middle and lower course of the Klabava River and its relation to the surrounding relief Václav Šastný

stastny@centrum. Cz Department of Physical Geography and Geoecology, Faculty of Science, Charles University Albertov 6, 128 43 Praha 2

Introduction Klabava is the most important watercourse in north–western Brdská vrchovina (Highland). Research on Neogene sediments and Quaternary river terraces, which are assumed to be important morphostratigraphic levels, contributes to understand genesis of the river valley and the surrounding relief. The research presented in this paper was focused on following topics: What are the extension and the structure of the fluvial sediments? How many morphostratigraphic levels do exist, and what is the difference among them? How did the river valley and surrounding relief develop during the Cenozoic?

Previous studies Terrace system of the Klabava River has been not yet completely investigated. It was may be caused by a relative small size of this river, or by an important anthropogenic relief transformation. A review of previous researches till the year 1959 was published by BALATKA & SLÁDEK (1962). According to these authors, there are developed three Pleistocene terrace levels, obviously diverging downstream with the present river. ZEMAN (1962) made a short remark about three terrace levels in a relative height of 30–40 m, 15–17 m and 5 m above the present stream. He parallelised these levels with the terrace system of the Berounka River. In next period the research was focused on Neogene sediments and on a paleogeographic reconstruction of the river system. Unpublished researches (PEŠEK & WILD 1970) were summed up in a paper by PEŠEK (1972). A variety of Neogene sediments and a tectonic disruption of sedimentary basins follow from this report. Author expects an isochronal disposition of the drainage pattern with the time of origin in upper Miocene in Western and Central Bohemia. Research reported by PEŠEK & SPUDIL (1986) was based on previous paper. It was focused on a question of correspondence of the upper Miocene river system and the present river system. New investigation aimed on pebble analysis has validated conclusions, which were made by PEŠEK (1972). They reconstructed watercourse D1, which had drained an adjacent area of the Brdy Mountains, with a help of petrologic analysis and

73 morphologic situation of Neogene sediments between and Chrást u Plzn village. This stream D1 followed generally the present Klabava River and flowed into the Central River close to Druztová. Another variant of the lower course in the direction to and further along the present Radnický Brook was also expressed in this paper. Unpublished technical reports and geological researches focused on gravel deposits play a very important role in the river terraces research. Many gravel and sand bodies close to Berounka River were investigated in a project Berounka I (WILD et al. 1961). There were noticed river terraces around Klabava river mouth. Project Berounka II (WILD et al. 1965) assessed fluviatile deposits on larger tributaries of the Berounka River. In this report, there were described primarily Neogene fluviatile sediments situated close to Klabava village and Quaternary river terraces in some measure. The geological map 1 : 50,000, sheet Plze (MAŠEK ed. 1994) indicates in the surrounding of the Klabava River several deposits of fluviatile sediments, which are classified and dated to Pliocene and Miocene. Sandy gravel sediments charted at the confluence of the Klabava River and Berounka River are dated to Mindel 1. According to explanatory notes (MÜLLER ed. 1997) to this map, the fluviatile sediments were distinguished into the Pliocene and Miocene level with a help of petrologic diversity and grain size. Papers by BALATKA & LOUĆKOVÁ (1991, 1992) are the most important for parallelization of the Klabava River terrace system with the Berounka River terrace system. There were distinguished two Neogene levels and thirteen Quaternary terrace levels along Berounka River by these authors. Neogene level A, Quaternary terraces IIIb, IVa, Va, Vb, VII and floodplain were noticed in the surrounding of the Klabava River mouth.

Methods Presented study of Klabava’s sediments is based on a field research and on a study of published and unpublished (Geofond) papers. There were determined in field: 1. the extend of river terraces, 2. petrologic characteristics of sediments. Valley sections along river km 11.7–19.0 and 24.9–26.2 were not investigated (serious relief changes caused by iron ore mining, ironworks, artificial lakes). These localities were assessed only with a contribution of archive reports. Unpublished papers also helped to delimit relics of Neogene sediments (PEŠEK & WILD 1970) and to specify bases of Quaternary river terraces. Mapped localities were plotted on a longitudinal profile (vertical exaggeration 138x, Fig. 3). Identified river terrace levels (Fig. 1) were parallelized with the terrace system of the Berounka River (BALATKA & LOUĆKOVÁ 1992). Nx – signature of Neogene sediment relics distinguished according to PEŠEK & WILD (1970), Kx – signature of Quaternary river terraces recognized in field.

74 Basic hydrographical and hydrological characteristics of Klabava Klabava River is the first important tributary of the Berounka River under the city of Plze. The river rises southeast of Padrské ponds in Brdská vrchovina (Highland) at an altitude of 678 m a.s.l. and it runs after 49 km into Berounka close to Chrást u Plzn at an altitude of 288 m a.s.l. Catchment area 2 3 -1 covers 372 km . Long-term average flow rate in mouth is 2,1 m . s (VLĆEK et al. 1984).

Geological structure, valley character Klabava flows through an area built of different resistant rocks. A geomorphologic rock value reflects in the river valley character. The longitudinal river profile is smooth and it does not indicate any important difference, caused by a recent tectonic activity. Through the Padrská kotlina (Basin), which is built of slightly metamorphosed Proterozoic slates, runs the stream in a very shallow and narrow depression (river km 43.7–41.1; gradient 9.9 ‰). Next does the river flow into an area of resistant Palaeozoic conglomerates and sandstones. Contents of quartz components, high intensity of diagenesis and high resistance are typical for these rocks. The river flows through this area in a valley, which is probably predisposed by a disjunctive tectonic activity (river km 41.1–24.8; gradient 13.5 ‰). In the Rokycanská kotlina (Basin) does the river incise into Palaeozoic shales (river km 24.8–16.9; gradient 4,7 ‰). Cross valley asymmetry is obvious in this river section. An usually steeper and higher slope on the right bank (northeast) is formed by an erosion rock step. A gentle slope on the left bank (southwest) passes gently into a surrounding relief. Next, close to Klabava village, does the river flow into Proterozoic phyllites, spilites and lydites (river km 16.9–0; gradient 3.6 ‰). The relief of the river valley is obviously transformed by previous human impacts. The original character of the valley is able to follow from Horomyslice. The river curves and meanders through a valley, which is deeply incised (40–50 m) in a surrounding relief. Such a type of valley is characteristic for most tributaries of the upper Berounka River course.

Neogene sediments Seven resp. eight relics of Neogene fluvial–lacustrine sediments (Fig. 2) were delimited after PEŠEK & WILD (1970). The relic N1 was charted by PEŠEK & WILD (1970) at the eastern periphery of Strašice round the elevation point 520 m a.s.l. Some authors (PEŠEK, SPUDIL 1986) consider these sediments to be a relic of a paleoriver D1, which drained Brdy (Mountains) in the direction along the present Klabava River, or of a paleoriver D2, which flowed in the direction from Strašice, between Komárov and Hoovice to Broumy and next to Kivoklát (there is no present

75 equivalent watercourse in this direction). There were not found out any details about this relic in unpublished reports (Geofond), therefore it is not charted in the map and on the longitudinal river profile. Neogene sediments of the relic N2 were find out to the south of Rokycany (ZÁLESKÝ 1987). Fluvial–lacustrine sandy sediments (average contents of 30 % quartz, lydite, spilit and greywacke) lie over Ordovician shales. Sandy sediments alternate with argillaceous and gravel fillings. Quaternary cover consists of soliflucted slope sediments. The base of Neogene sediments lies at an altitude of 375–377 m a.s.l. and the surface at an altitude of 380–382 m a.s.l. Thickness of sediments reaches up to 4,5 m (ZÁLESKÝ 1987). The triangle shaped relic N3 reaches from the north periphery of Rokycany as far as to the foot of the monadnock Vršíćek (430 m a.s.l.). Red to brown argillaceous sands and gravels change very quickly in lateral and vertical direction. They are overlain by reddish clays containing dispersed pebbles of conglomerate and quartz (PEŠEK & SPUDIL 1986). Base formed by Proterozoic and Ordovician shales varies from an altitude of 366 to 386 m a.s.l. Thickness of sediments reaches up to 20 m. The relic surface is situated at an altitude of 383–397 m a.s.l. These sediments are exposed in a sand pit to the south of the Vršíćek monadnock, or close to a cemetery to the north of Rokycany. In this connection it is important to remark an extensive locality N4, that is covered by lydite, sandstone and conglomerate gravel. This site is situated on the field 1,5 km to the east of Rokycany (along the red hiking trail). There were exposed white to yellow clays under gravel. The surface of this probably Neogene relic is located at a height of 410–415 m a.s.l., which is at the highest altitude of all fluviatile sediments in the Rokycanská kotlina (Basin). The base’s situation is unknown. The relic of Neogene sediments N5 is situated in the area between Klabava village and monadnock Smrkový vrch (443 m a.s.l.). In the section red to brown sandy layers alternate with greyish white argillaceous layers. The sediment surface reaches an altitude of 381 m a.s.l. The sediment base built of Ordovician and Proterozoic shales is situated at an altitude of 362 m a.s.l. (WILD et al. 1965). White to yellow clays are exposed in a sand pit to the southwest of the monadnock Smrkový vrch. The most extensive and the most important occurrence of Neogene sediments N6 in research area is situated between and Kyšice. Up to 60 m (PEŠEK & WILD 1970) thick fluvial and lacustrine sediments of fresh– water lake flown through were aggraded on a bedrock built of Proterozoic and Upper Palaeozoic sediments. Basal coarse gravels start at the bottom of the section. Upwards they turn into sands and clays of lacustrine provenance containing plant fossils. These sediments are grey to white coloured (PEŠEK & WILD 1970). The highest elevation point of the surface of these sediments is situated at an altitude of 399 m a.s.l., on the western margin of former lake basin under a monadnock Pohodnice (499 m a.s.l.). This hill is the locality of

76 origin of a thick cover of soliflucted slope sediments (according to LOCHMANN, 1961 is the thickness up to 49 m), which protected lacustrine sediments from denudation. Sediments in the eastern area were denudated about 20 m in comparison to the western area, located under the monadnock (LOCHMANN 1961). Neogene sediment’s base altitude varies evidently from 394 m a.s.l. to 324 m a.s.l., where it is slanting even below the present Klabava River (Fig. 3). According to PEŠEK & SPUDIL (1986), this fact was probably caused by a synsedimentary tectonic descent of the lake basin. The small relic N7 of Neogene fluvial sediments is located between Dýšina and Nová Hu. This occurrence is exposed by a small sand pit, which is situated 100 m to the west of a railway underpass. Reddish to brown argillaceous sands and gravels occur here. An altitude of this sand pit is 350 m a.s.l. Base of sediments is situated at an altitude of 329 m a.s.l. according to borehole V216 (PEŠEK & WILD 1970). These sediments were stated to be of Quaternary age in paper by DLOUHÝ (1984). Another small occurrence of Neogene sediments N8 was charted by PEŠEK & WILD (1970) on the northern periphery of Dýšina. There were found argillaceous sands and sandy gravels to the south of this relic, with the surface at an altitude of 350–352 m a.s.l. The thickness is not less then 4 m, but the base was not reached (ADLER & BOUĆEK 1985).

Quaternary river terraces River terraces of the Klabava River form a system of 4 terrace levels on the middle and lower river course (Fig. 3). There was distinguished relatively small number of 18 terrace localities on 30 km of investigated river section (Fig. 2). Most problematic is the totally reformed river section between Horomyslice and Klabava villages. Many terrace flights were overlain by slope sediments (as supported by geological boreholes), or removed by slope processes. Terrace localities mentioned in older reports (ANDRUSOV et al. 1940; WILD et. al. 1965; CEJNAR & VACHTL 1959 etc.) often do not correspond to each other, as well to the field situation. For that reason this paper describes only river terraces evident in field. Classification of these river terrace occurrences into a system, especially on the middle river course, is due to their low number (and extension) very problematic and follows from their topographical position above all. Surprisingly, it is possible to find semi–rounded to rounded conglomerate pebbles and boulders in a coarse–grained gravels of river terraces (K17, K18), which are situated very close to Brdy (Mountains). Siliceous conglomerates, very common in the geological structure of this mountain range, usually disintegrate into angular blocks. Such blocks should not be distinctly rounded, due to a high resistance of the rock and because of short gravel transportation. A solution of this task may be found in a slope sediments section, which is located at Bahna area to the south of Strašice village. An upper layer consists

77 of conglomerate angular blocks floating in clays (probably a soliflucted layer). A bottom layer, under a sharp boundary, is compound of corroded semi–rounded rock fragments with a sandy filling (probably weathered in situ). Structural mature of such fragments may be very high, even if the fluviatile transportation is very short. The second variant is a redeposition of pebbles, which weathered from Upper Palaeozoic arkoses (a small relic around Mirošov town).

Terrace level I Terrace level I comprises extensive terrace flights located above the edge of the river downcut. Terrace flights pass gently into a higher relief very often. Due to this fact, it is very complicated to mark boundaries of terraces. This terrace level probably corresponds to the IIIb terrace (Mindel 1/Elster) of the Berounka River (BALATKA & LOUĆKOVÁ 1992). Both the Berounka River and the Klabava River aggraded the extensive river terrace K4 to the north and northeast of Chrást u Plzn village. The flight slopes very moderately downward to edges, which are incised by erosion furrows. The terrace flight’s surface, covered by quartz and lydite pebbles up to 10 cm in diameter, is located at an altitude of 337–340 m a.s.l. According to numerous boreholes (WILD et al. 1961), the terrace K4 consists of brown to red gravely sands up to 5 m thick, with the base at an altitude of 334–335 m a.s.l. This locality was charted by BALATKA & LOUĆKOVÁ (1992) as the IIIb river terrace of the Berounka River. In C. PURKYN’S conception (1913) it was charted as the I. upper river terrace. The same opinion was expressed by WILD et al. (1961). Very close to this terrace flight there are exposed saprolithes of graphitic slates and spilites (WILD & HEJCMAN 1978) in a clay pit on the south periphery of Chrást u Plzn village. Their base lies at an altitude of 350–355 m a.s.l. The river terrace K5 is situated on the opposite bank of the Klabava River in the same altitudinal position and it reaches as far as to Smdćice and Sedlecko. The body consists of yellow to brown sand with quartz and lydite gravel admixture (there were found white to grey clays thick up to 0.75 m in an excavation at an altitude of 340 m a.s.l. on the west margin of Smdćice). The terrace base built of Proterozoic slates is situated at the depth of 3 m. Terrace edges are disrupted by erosion furrows. The locality K5 was classified as the river terrace IIIb in the Berounka River terrace system (BALATKA & LOUĆKOVÁ 1992). PURKYN (1913) classified it as the I. upper river terrace, identically to WILD et al. (1961). The river terrace K15 was identified on the right river bank from Osecký Brook mouth to D5 highway feeder close to Rokycany. The terrace flight is situated at an altitude of 360–364 m a.s.l., 10–12 m above the river. The step of this terrace is covered by field sheet wash sediments. At the depth of 2–3 m, there are exposed coarse-grained gravels (boulders up to 30 cm in

78 diameter) in erosion furrows. The terrace surface passes unobviously into a higher relief and the area extend of K15 fluviatile sediments is a controversional question, identically to other occurrences in the Rokycanská kotlina (Basin). Gravels of this terrace were also identified by the borehole J73 at an altitude of 358/359 m a.s.l. Equivalent sandy gravels were reached by the borehole J181 at an altitude of 354/360 m a.s.l. and J182 at an altitude of 356/358 m a.s.l. on the opposite bank of the Klabava River (HORÁK 1988). The river terrace K17 follows the right bank of the Klabava River above Kamenný Újezd. The extensive terrace flight is covered by semi-rounded to rounded conglomerate and lydite pebbles up to 20–30 cm in diameter. The terrace surface slopes downward to edges very moderately as well it gradually passes into the surrounding relief. The terrace flight is located at a relative height of 18–20 m above the present stream, i.e. at a typical altitude of 392– 394 m a.s.l. The terrace base built of Ordovician shales is exposed at the depth of 2–3 m. The Klabava River’s right bank from Dobív to Hrádek u Rokycan is accompanied by a river terrace K18. The terrace flight at an altitude of 412– 416 m a. s. l. is located at a relative height of 12–14 m above the river. It is possible to find semi-rounded to rounded conglomerate pebbles up to 5–10 cm in diameter (boulders up to 50 cm, too) on its surface. Argillaceous sands were exposed by deep ploughing, especially on the edge of the terrace flight. Sands with gravel admixture are exposed along the road to the south of Pavlovsko.

Terrace level II

The river terrace K6 is represented by the terrace flight at an altitude of 314–316 m a.s.l., with a relative height of 20 m above the present river. The surface covered by resistant rocks pebbles is separated from the river terrace K4 by a steeper slope. There was exposed brown gravel (consisting of pebbles up to 5 cm in diameter) in a test pit on the north margin of the terrace flight. The locality K6 was classified as the river terrace Va (Mindel 2–Riss 1/Fuhne–Saale) in the Berounka River system by BALATKA & LOUĆKOVÁ (1992).

Terrace level III Occurrences of the terrace level III are usually found as sedimentary relics left on rock outcrops at a height of 12–15 m above the present watercourse. River terraces of the III. level corresponds probably to the V. group of river terraces (Mindel 2–Riss 1/Fuhne–Saale) of the Berounka river (BALATKA & LOUĆKOVÁ 1992). 2 A small relic of the river terrace K1 with an area of 400 m is located above the contact of floodplains of both Berounka River and Klabava River. The terrace surface lies at an altitude of 302–303 m a.s.l., approximately 15 m

79 above the river. It is possible to find quartz pebbles on the terrace flight. The base at the depth of maximally 1 m is shown by phyllite outcrops. The river terrace K2 is situated on the left bank of the Klabava River mouth. The terrace flight lies at an altitude of 303–304 m a.s.l., at a relative height of 15 m above the present stream. Many quartz and lydite pebbles were found on the surface in sandy soil. In PURKYN’S conception (1913) was this locality charted as the II. middle river terrace. A flight of the river terrace K7 slopes moderately down to the edge along the left bank of Klabava River, close to a bridge on the road Chrást– Smdćice. The terrace surface is located at a height of 310–313 m a.s.l., and reaches relative height of 12–15 m above the river. According to slate outcrops overlain by gravel (quartz and conglomerate pebbles 3–5 cm in diameter), lies the base at the depth of 1.5–2 m. The narrow river terrace K8 with a similar altitudinal position (310–313 m a.s.l.) is situated just on the opposite bank of the Klabava River. Slate outcrops are covered by reddish brown coloured sandy gravel 2 m thick. The river terrace K10 is located in the centre of the river curve close to Dolní Chrást. The surface, covered by rounded pebbles and boulders, slopes moderately down to flight’s edges. A typical altitude of the terrace surface reaches 312–314 m a.s.l., approximately 13–15 m above the stream. This locality was classified as the VI. river terrace in the Berounka River terrace system (BALATKA & LOUĆKOVÁ 1992). PURKYN (1913) mapped this occurrence as the III. lower river terrace. The same opinion was expressed by WILD et al. (1961). There were charted even three terrace levels in the river curve centre on the geological map by ANDRUSOV et. al (1940). But the field situation does not correspond to this fact. The river terrace K13 is represented by a narrow terrace flight on the right bank of the Klabava River, close to Horomyslice. The surface is located at an altitude of 328–330 m a.s.l. (relative height 12–14 m) and it slopes downward slightly to the edge. Spilite outcrops at the base are overlain by a gravel accumulation up to 0,75 m thick (pebbles 5–10 cm in diameter) with sandy filling. The flight’s edge is undulated due to erosive processes. The river terrace K13 was charted in a map by PURKYN (1913) as a locality of the I. terrace level. The river terrace has probably continued up the stream to the area, which is now covered by extensive slag heaps, as follows from the mentioned map (PURKYN 1913). A very small relic of the river terrace K14 consists of reddish brown sandy gravel. The terrace body is lying at an altitude of 328 m a.s.l. (relative height 13 m) on a spilit outcrop just under the Golf Centre in Horomyslice on the left bank of the Klabava River. Due to earthworks during the golf playground building, this relic is the last evidence of the river terrace presence in this place.

80 Terrace level IV Terrace bodies of this level are located very often on rock outcrops close to Klabava river, or at the contact of valley sides with the floodplain. Terrace level IV corresponds to the VII. group of river terraces (Würm/Weichsel) of Berounka (BALATKA & LOUĆKOVÁ 1992). The flight of the river terrace K3 flanks the right margin of the floodplain and it rises up by 5–6 m. The terrace surface at an altitude of 296–298 m a.s.l. slopes gently downward to the edge along the river. The base position is unknown. The terrace flight’s centre is dissected by now waterless erosion furrows with a wide alluvial cone. The terrace flight extends upstream from several meters up to 30 m. On the terrace edge there are exposed quartz and lydite pebbles 10–15 cm in diameter. The river terrace K3 is equivalent to the locality charted in PURKYN’S map (1913) as the III. lower terrace. The river terrace K9 is situated south–west to the bridge lying on the road from Chrást to Smdćice. The terrace surface reaches a relative height of 5–6 m above the present stream, i.e. 304–305 m a.s.l. The terrace base is defined by a rock outcrop at an altitude of 303 m a.s.l., overlain by sandy gravel up to 1.5 m thick. The locality K11 is located to the southeast of Dolní Chrást village. The terrace flight lies at a relative height of 6–8 m above the Klabava River, at an altitude of 307–309 m a.s.l. Base situated on spilite outcrops is exposed at the depth of 1–2 m. This river terrace was charted as the III. lower terrace in C. PURKYN‘S conception (1913). In the system by BALATKA & LOUĆKOVÁ (1992) was the locality K11 classified as the river terrace of the VI. group. The river terrace K12 is situated along the right river bank, to the west of the river meander in Nová Hu. There is still visible a Holocene paleochannel of a meandering river at the foot of the terrace step. The terrace surface is covered by well–rounded pebbles of conglomerate, quartz and spilites. The terrace flight slopes downstream into the floodplain. Typical height of the river terrace K12 is 6–7 m above the present watercourse, i.e. 311–312 m a.s.l. The base at the depth of 2 m is located on rock outcrops. This river terrace was classified as the III. lower terrace in the system by PURKYN (1913). Between Rokycany and the south–western periphery of Kamenný Újezd, there is situated the terrace flight K16 on the right bank of the Klabava River at a relative height of approximately 6–8 m (374–376 m a.s.l.). The base is unknown. There is exposed boulder gravel (conglomerate) in the terrace step at the depth of 1–1.5 m. The terrace surface passes gently upward into the river terrace K17. Sandy gravel detected by boreholes (base at an altitude of 357–358 m a.s.l.) in the town centre of Rokycany (HROUDA 1990) pertain probably to the terrace level IV as well as gravel at an altitude of 359 m a.s.l., which were exposed by an archaeological research in the year 2004 close to the Museum of Rokycany.

81 Floodplain The arrangement of the floodplain was able to investigate only by a help of insufficient quantity of boreholes and sections. The base of the floodplain is usually situated at the depth of 4–6 m and it slopes regularly down the river. The only localities, where the exposed bedrock appears in the riverbed, are situated in Kamenný Újezd (river km 23.7 and 22.0). In these places the river flows rapidly over low rock bars in the river channel. There are usually aggraded coarse–grained fluviatile sediments – boulder to sandy gravel with a smaller portion of fine–grained material (prevailing conglomerate, quartz and lydite first of all) on the bedrock. This layer is overlain by alluvium accompanied by fluvisols. The floodplain surface is mostly situated 1–2 m above the present river. The vertical structure of the floodplain is excellently exposed in position of the Klabava River inflow into the flooded quarry (river km 14.7) close to Ejpovice. The river eroded a concrete channel during the flood in August 2002 in this place and exposed river banks as deep as to the bedrock. Due to previous iron ore mining is the riverbed incised 4–5 m in comparison to an original position. The bedrock built of Ordovician shales is overlain by a 140– 160 cm thick layer of sandy gravel compound of quartz, sandstone and conglomerate pebbles up to 20 cm in diameter. The sand admixture rises upward in this layer. The section continues above a sharp boundary by a 90– 110 cm thick layer of well consolidated grey coloured alluvium sediments. These sediments are high–resistant in dry state. Above the upper boundary of this layer occurs several centimetres thick filling compound of sand with slag fragments (probably a relic of former ironworks in Klabava village). Upward follows a 15–20 cm thick layer of horizontal lamellae, where fine sands and soil sediments are regularly changing. This layer probably documents an episodical flood aggradation. Last layer of this section consists of chaotic mixture of rock fragments, pebbles and soil sediments and it is related to overburden removal. The floodplain width depends on the valley character. Only several metres wide is the floodplain in Brdy Mountains. Its development is made impossible by a large volume of angular blocks in the river channel. From Dobív village enlarges the floodplain up to 200–300 m in Rokycanská kotlina (Basin). The maximal floodplain width occurs between Rokycany and Klabava village (550 m) and close to the confluence of the Klabava River and Berounka River.

Geomorphologic development of the river valley and the surrounding relief An existence of an elevation in the area of the present Brdská vrchovina (Highland) already during Cretaceous period is indicated by Cretaceous

82 marine sediments, that occur only to the north of this mountain range and do not penetrate to the south of it (CHLUPÁĆ et al. 2002). Also during the Lower Miocene period was this mountain range a part of so–called Bohemian threshold (e.g. TYRÁĆEK 2001). The study area is located since Palaeozoic in terrestrial settings, where an intensive denudation is in progress. Geomorphologic development of the relief along the Klabava River may be reconstructed on the basis of evidences only since the Lower Cenozoic period. As a reflection of a warm humid climate during the Palaeogene, several relics of thick chemical weathering mantels may be found in the study area. Their occurrence depends on geological structure and on preservation possibility. The existence of chemical paleoweathering on the middle course of the Klabava River is proved by silcretes fragments found in water lain gravel. Silcretes genesis used to be associated with a kaolinitic saprolith, where silica is transferred (SUMMERFIELD 1983). The existence of silcretes along the Klabava River is probably connected to small areas of feldspars rich rock (arkoses close to Mirošov and Skoice, granites eastward of Padrské ponds). Coat silcretes were found in crevices of conglomerate walls on the Žár hill (629 m a.s.l.). Mean accumulations are located 20 m bellow a rock–face edge at an altitude of 520–540 m a.s.l. These silcretes were sedimented in shallow layers up to 4 mm thick and shaped into vertical ridges and strias. They probably developed by a circulation of silica–rich groundwater through the bedrock and by a transport of fine silica particles. The age of these silcretes seems to be probably Miocene (Š ASTNÝ 2004). An interesting locality of an argillaceous weathering mantle is situated in a clay pit on the southern periphery of Chrást u Plzn village on the lower course of the river. There is exposed up to 15 m thick saprolith of Proterozoic graphitic slates and spilites with the base at an altitude of 350–355 m a.s.l. (WILD & HEJCMAN 1978). This locality was preserved against denudation by favourable conditions. These reddish to dirty white clays with sandy admixture consist of kaolinite, illite, quartz and weathered plagioclase (WILD & HEJCMAN 1978). In bottom horizons of sections are situated deeply weathered rocks with well-preserved structure. This saprolith is absolutely non-resistant. The material was washed off in Miocene into surrounding fresh-water lakes, where the evidences of a sheet wash from Proterozoic rocks was found (WILD & HEJCMAN 1978). This fact manifests the maximal Miocene age of described weathering mantle. Also the findings of greyish white water lain clays at an altitude of 340 m a.s.l. on the western margin of Smdćice indicates the fact, that in the period of river aggradation in this highest level, there were still washed off argillaceous sediments from surrounding saprolith. Another explanation may be seen in repetitive transport of Miocene lacustrine sediments. In crevices of lydite monadnocks and on ryolith veins in Rokycanská pahorkatina (Hilly land), there were found several relics of argillaceous

83 saprolith at an altitude of 380–450 m a.s.l. (LOCHMANN 1963, ŠTAFL 1957). The saprolith consists of sericite, kaolinite and micas. ŠTAFL (1957) ruminated on Neogene age of these relics, while LOCHMANN (1963) supposed the Palaeogene age. Both authors consider these occurrences to be relics of a Tertiary planation surface. It is possible to prove a development of a drainage pattern since Miocene. A watercourse (Paleoklabava), that followed more or less the present stream, arose because of neotectonic movements, which have dissected a Palaeogene planation surface and have formed fundamental morphostructures. M. MALKOVSKÝ (1975) assumes the Palaeogene planation surface splits up in the Lower Miocene. Neogene unterraced sediments are usually several metres thick, with a maximum thickness of over 60 m in the relic N6 close to Ejpovice (PEŠEK & WILD 1970). Frequent lateral and vertical structural changes of deposits indicate a fluviatile sedimentary environment. An extensive deposit of coarse- grained basal gravels overlain by thick clays with sandy fillings has developed close to Ejpovice village. This body was aggraded in a fresh-water lake. Bases of Neogene deposits vary vertically (see the longitudinal profile). Some authors (PEŠEK & SPUDIL 1986) explain vertical differences by tectonic movements. This explanation may be accepted in case of thick deposits of some relics (e.g. N6), where the thickness was probably reached by synsedimentary tectonic descent (PEŠEK & SPUDIL 1986). These authors (PEŠEK & SPUDIL 1986) suppose on the basis of structural similarity the isochronal Middle to Upper Miocene age of all deposits. MALKOVSKÝ (1975) considers these fluviatile sediments to be of Lower Miocene age. The deposits along the Klabava River are usually unfossiliferous and the dating is for that reason very controversial. For that reason I prefer to state only a Neogene age in case of non–dated deposits. Some localities may represent relics of much younger fluviatile aggradation. E.g. classification of the deposit N2 (southward of Rokycany) to be a Miocene relic (ZÁLESKÝ 1987; PEŠEK & SPUDIL 1986) is problematic. This locality is situated at the altitude identically to Quaternary river terrace K17 (Fig. 3) and therefore it might be a younger aggradation, that was deposited by a shallow incised water stream. This might be also indicated by a presence of an extensive surface N4 (to the east of Rokycany town), that is covered by gravel. This deposit is located at an altitude of 410–415 m a.s.l., that is 30 m higher than the relic N2 and it also corresponds structurally and altitudinally to the locality N3 between Rokycany town and village. It is evident from known localities, in Miocene the Paleoklabava River coursed in a shallow depression from the Rokycanská kotlina (Basin) to Chrást u Plzn village among the elevations Vršíćek, Smrkový vrch and Hradišt on the right side and Ćilina, Pohodnice and Ćerná my on the left side. The river probably flowed into the Central River close to Druztová on

84 the lower course (PEŠEK & SPUDIL 1986). The variant of the lower course directing to Radnice and further along the present Radnický Brook (watercourse Dx by PEŠEK & SPUDIL 1986) seems to be less likely. Deposits 62 and 63 (sensu PEŠEK & SPUDIL 1986) do not contain Lower Palaeozoic rocks, which are present still in the relic N6 (59 sensu PEŠEK & SPUDIL 1986). In the next period (i.e. till the aggradation of the uppermost terrace level I), that was most important for conversion of the Miocene river system into a modern drainage pattern, it is impossible to prove the development of the river and surrounding. A paleogeographical reconstruction is difficult due to a lack of evidences, as in many places of the Bohemian Massif (TYRÁĆEK 2001). Because the present river follows the Miocene stream, the same position of the river in Pliocene is most likely. Till the river incised into gravel deposits of the I. Quaternary terrace level, it has flown in a wide and shallow valley during this period. The valley floor was located 45–50 m above the present stream on the lower course, as the base of the river terrace K4 proves. On the middle course flowed the river in a position approximately 20 m above the present watercourse (base of the river terrace K17). The relative height of the I. terrace level increases downstream with an obvious divergence. The base of argillaceous saprolith at an altitude of 355–360 m a.s.l. very close to the river terrace K4 (surface at an altitude of 337–340 m a.s.l.) indicates, that the modern Klabava River, resp. Berounka River did not reach this altitude and water lain aggradations of the I. terrace level, resp. river terrace IIIb may incorporate bodies of several older periods. From the edge of the river valley on the middle course, especially in the Rokycanská kotlina (Basin), extends a soft and gently undulated relief with protruding monadnocks. As the morphometric analysis has shown, gently inclined slopes 0–4° predominate in this area. The following facts indicate, that the surface may be classified as a fossil planation surface at a foot position. o Extensive and gently inclined surfaces spread from the Klabava River and its tributaries. o The bedrock consists of Ordovician shales, Proterozoic shales and greywackes. The boundary between these rocks (from the eastern margin of cross the southern foot of the monadnock Vršíćek to the Klabava dam) is not manifested in the relief. o Though the sedimentary rocks are inclined in different angles (15–55°), the surface is horizontal to sub–horizontal and it cuts across the bedrock. o The thickness of a saprolith on the bedrock is usually very low, some ditches are dug even right into shales.

85 o Between and Svojkovice, there were not find any cryogenetic transformations of the shale saprolith, in a drainage trench up to 3 m deep (such cryogenetic transformations were found in the relief of surrounding elevations e. g. southwest of Ohrada 509 m a. s. l.). The saprolith formed probably during the Holocene due to this fact. It may be also indicated by their low thickness 0.15–3 m, which depends on hydrogeological conditions (MAREK 1985, HORÁK 1988). o Unfortunately any knickpoints of planation surface and back slopes were found, because all the slopes are covered by thick taluses. On lydite monadnocks it is probably also caused by an extreme rock resistance.

These planation surfaces might develop in an existing depression of the Rokycanská kotlina (Basin), already since Upper Miocene to aggradation of the I. terrace level. Also the development in the next period (after the downcut into the I. terrace level) is most likely, because the surrounding surface passes unmarkedly onto the terrace flight K17 or K15. The Klabava River incised into a deep valley during a period next to an aggradation of the I. terrace level and before an aggradation of the III. terrace level. A valley floor was cut down by up to 30 m on the lower course and became narrow. Potentional reasons for changes in downcut dynamics and for an obvious altitudinal interval between „upper“ and „middle“ river terraces in Bohemian Massif were formulated by TYRÁĆEK (2001). It might be caused by a netotectonic phase, glaciisostatic movements, or by an abrupt climate changes from low-amplitude climatic cycles (Laplace period) to high- amplitude climatic cycles (Milankovich period), which occurred in the Middle Pleistocene (TYRÁĆEK 2001). On the middle river course, with a bedrock compound of low-resistant shales and Neogene fluviatile deposits, flowed the river longer in a shallow valley, because it had to respect the intensity of incision into more resistant Proterozoic rocks on the lower course. The valley downcut is not so deep in this section and also the differentiation of river terraces is problematic. Next incision, to the IV. terrace level, resp. present valley floor, was not so distinct and the valley floor was cut down by 8–10 m, resp. 6–7 m. Coarse- grained gravels with overlying fine-grained flood sediments have aggraded on valley bottom during the Holocene. As a characteristic feature of the floodplain river meandering occurred. Relict meanders are still visible in the river section Nová Hu–Dolní Chrást. Valley slopes are formed by erosion furrows. Sediments, which are very often supported by a field sheet-wash are transported through these furrows and aggraded into alluvial cones on margins of the floodplain. The original relief of the valley and surrounding was intensely transformed by a human impact during 50’s to 70’s of the last century.

86 The longitudinal profile of the Klabava River (Fig. 3) is smooth and does not show any Quarternary tectonic changes (cf. STARKEL 2003). Therefore is probably incorrect the opinion of PEŠEK & SPUDIL (1986), who speculated of Quaternary tectonic movements in relic N6 close to Ejpovice on the basis of presence of 40–50 m thick talus (LOCHMANN 1961) aggraded at the eastern foot of the monadnock Pohodnice. Taluses with similar thicknesses were recognised in other places, e. g. in Brdská vrchovina (Highland) (CÍLEK & LOŽEK in CÍLEK et al. 2005). Such a phenomenon should be more likely connected with a climatically conditioned intensity of weathering during the Quaternary. On the contrary, the extensive planation surfaces developed at a foot position in Rokycanská kotlina (Basin), indicate a long-lasting tectonic stability of the area (cf. DEMEK 2004).

References ADLER J. & BOUĆEK M. 1985. Inženýrskogeologický przkum Ejpovice. I. a II. etapa prací. Praha : MS Geofond. P053633. ANDRUSOV D. et al. 1940. Geologická mapa Protektorátu Ćechy a Morava. List Kralovice 4051. Praha. BALATKA B. & SLÁDEK J. 1962. íćní terasy v ćeských zemích. Praha. Praha : Geofond v nakladatelství ĆSAV. 580 s. BALATKA B. & LOUĆKOVÁ J. 1991. Kvartérní terasy eky Berounky. Geografie – Sborník ĆGS 96 (3): 145–162. BALATKA B. & LOUĆKOVÁ J. 1992. Terasový systém a vývoj údolí Berounky. Studia Geographica 96. Brno: GÚ ĆSAV. 53 s. CEJNAR V. & VACHTL B. 1959. Závrećná zpráva Ejpovice a okolí – Klabava, Fe rudy. Praha : MS Geofond. FZ002943. CHLUPÁĆ I. et al. 2002. Geologická minulost Ćeské republiky. Praha : Academia. 437 s. CÍLEK V. et al. 2005. Stední Brdy. Píbram: MZ ĆR, MŽP ĆR, ĆSOP Píbram a Kancelá pro otázky ochrany pírody a krajiny Píbram. 376 s. DEMEK J. 2004. Etchplain, Rock Pediments and Morphostructural Analysis of the Bohemian Massif (). In: Drbohlav D., Kalvoda J., Voženílek V. eds.): Czech Geography at the Dawn of the Millenium. Olomouc : Palackého univerzita v Olomouci. p. 69–81. DLOUHÝ V. 1984. Surovinová studie. Západoćeský kraj. Surovina písky. Okres Plze- sever. Surovina – písek stavební. Praha : MS Geofond. P045249. HORÁK L. 1988. Zpráva o podrobném inženýrskogeologickém przkumu pro akci Dálnice D5, stavba 0508 Svojkovice–Klabava. Praha: MS Geofond. P059506. HROUDA E. 1990. Rokycany – podrobný inženýrskogeologický przkum staveništ školy. Praha : MS Geofond. P068910. LOCHMANN, Z. 1961. Poznámky ke geologii kvartéru v okolí Ejpovic (Plzeská pánev). Ćasopis pro mineralogii a geologii 6 (1): 37–45. LOCHMANN Z. 1963. Denudaćní relikty fosilních zvtralinových pláš Plzeské pahorkatiny. Ćasopis pro mineralogii a geologii 8 (1): 21–28. MALKOVSKÝ M. 1975. Paleogeography of the Miocene of the Bohemian Massif. Vstník ÚÚG 50. Praha : ÚÚG. s. 27–31. MAREK V. 1985. Inženýrskogeologický przkum trasy dálnice D5 v úseku Svojkovice– Rokycany. Praha: MS Geofond. P049482. MAŠEK J. ed. 1994. Geologická mapa ĆR. List 12–33 Plze. Praha: ĆGÚ.

87 MÜLLER V. ed. 1997. Vysvtlivky k souboru geologických a ekologických úćelových map pírodních zdroj v mítku 1: 50 000. List 12–33 Plze. Praha: ĆGÚ. 61 s. PEŠEK J. 1972. Terciérní sedimenty ve stedních a západních Ćechách. Sborník ZPĆ muzea – ada Píroda 6. Plze: Západoćeské muzeum. 56 s. PEŠEK J. & SPUDIL J. 1986. Paleogeografie stedoćeského a západoćeského neogénu. Studie ĆSAV 14. Praha: Academia. 79 s. PEŠEK J. & WILD J. 1970. Litostratigrafický a paleogeografický výzkum sediment stedoćeského karbonu a terciéru. Praha: MS Geofond. P022049. PURKYN C. 1913. Geologie okresu Plzeského. Plze: Okresní výbor v Plzni. 137 s. STARKEL L. 2003. Climatically controlled terraces in uplifting mountain areas. Quaternary Science Reviews 22: 2189–2198. ŠTAFL I. 1957. Zbytky tercierních zvtralin na dolním toku Úslavy. Sborník ĆSZ 62 (3): 238–239. Š ASTNÝ V. 2004. Silkrety z vrchu Žár (Strašická vrchovina). Geografie - Sborník ĆGS 109 (4): 332–334. SUMMERFIELD M. A. 1983. Silcrete. In: Goudie A. S., Pye K. eds. : Chemical sediments and geomorphology: precipitates and residua in the near–surface environment. London : Academic Press. s. 59–91. TYRÁĆEK J. 2001. Upper Cenozoic fluvial history in the Bohemian Massif. Quaternary International 79: 37–53. VLĆEK V. et al. 1984. Zempisný lexikon ĆSR – vodní toky a nádrže. Praha: ĆSAV. WILD J. et al. 1961. Przkum štrkopísk Berounka I – 51 300 056. Praha: MS Geofond. P013252. WILD J. et al. 1965. Berounka II – 512 325 060. Praha: MS Geofond. P019066. WILD J. & HEJCMAN Z. 1978. Chrást u Plzn. Surovina: cihláské suroviny. Praha: MS Geofond. FZ005672. ZÁLESKÝ J. 1987. Rokycany – inženýrskogeologický przkum J1 - J23, J3A, J3B, J16A. Praha: MS Geofond. P057043. ZEMAN A. 1962. Zpráva o mapování pokryvných útvar na severním okraji Rokycan. Zprávy o geologických výzkumech v roce 1961. Praha: ÚÚG. s. 260–261.

88

Surface Locality Base Thickness Level Stratigraphy Altitude Relative (sign.) (m a.s.l.) (m) (sign.) (m a.s.l.) height (m)

N1 520? 70? ? ? ? ? N2 381 22 376 < 5 N Neogene Neogene N3 397 45–50 366–386 < 20 N Neogene N4 415 40–42 ? ? N Neogene N5 381 41 362 19 N Neogene N6 399 69 324–394 > 60 N Neogene N7 350 42–44 329 21 N Neogene N8 350–352 48 348 4 N K1 302–303 15 301–302 1 III V (Mindel2-Riss1/Fuhne-Saale) K2 303–304 15 ? ? III V (Mindel2-Riss1/Fuhne-Saale) K3 296–298 5–6 ? ? IV VII (Würm/Weichsel) K4 337–340 48–52 334–335 3–5 I IIIb (Mindel1/Elster) K5 336–340 48–52 333–337 3 I IIIb (Mindel1/Elster) K6 314–316 20 ? ? II IVa (Mindel2-Riss1/Fuhne-Saale) K7 310–313 12–15 308 2 III V (Mindel2-Riss1/Fuhne-Saale) K8 310–313 15 309 2 III V (Mindel2-Riss1/Fuhne-Saale) K9 304–305 5–6 303 1–2 IV VII (Würm/Weichsel) K10 312–314 13–15 ? ? III V (Mindel2-Riss1/Fuhne-Saale) K11 307–309 6–8 306–308 1–2 IV VII (Würm/Weichsel) K12 311–312 6–7 309–311 2 IV VII (Würm/Weichsel) K13 328–330 12–14 327–329 1 III V (Mindel2-Riss1/Fuhne-Saale) K14 328 13 327 1 III V (Mindel2-Riss1/Fuhne-Saale) K15 360–364 10–12 358 2–3 I IIIb (Mindel1/Elster) K16 374–376 6–8 ? ? IV VII (Würm/Weichsel) K17 392–394 18–20 390–391 2–3 I IIIb (Mindel1/Elster) K18 412–416 12–14 ? ? I IIIb (Mindel1/Elster) floodplain 1-2 Holocene

Fig. 1. Basic characteristics of Neogene sediments and Quaternary river terraces on the middle and lower course of the Klabava River. Stratigraphy parallelized with the terrace system of the Berounka River (BALATKA & LOUĆKOVÁ 1992).

89

Fig. 2. Map of Neogene sediments and Quaternary river terraces in study area.

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Fig. 3. Longitudinal profile of Neogene sediments and Quaternary river terraces (vertical exaggeration 138x ).

91