8589356506

18 JACEK LECH

Fig. 18. Ojców National Park near Cracow. Korytania ravine.

Searching for flint in conditions approximating to primeval

Photo by F.M.Stępniowski

II.    Siliceous rocks in the Tertiary cluvial deposits.

III.    Siliccous rocks in thc Quaternary glacial tills; glacifluvial sands and grits and in other loosc litholo-gical formations (Tertiary and older ones) as well as on the sca shores and in the Holocene wash.

Abundant and terrential rainfall is the most important agent exposing and revealing the siliceous rock deposits (Armstrong 1926, 101). In the Atlantic period it was greater than at present. We can imagine that the mor-phological action of the torrential rain had a vast efFect on the deposits from the Atlantic period, sińce we have a good contemporary knowledge of this type of process (Kondracki 1937; Starkel 1967, 491, 493).

The erosive action of sea wavcs, of divagating rivers and streams, was exposing in some places all the deposits of the siliceous rocks mentioned so far. Those agents were of special significance for the exposure of the deposits in the massive rocks. To a certain extent they could release them, leading to the formation of loose rock as screes, which were then transported further by water.

The tectonic faults, first of all in the Jurassic lime-stones, had some influence on the accessibility of the raw materials in the massive rocks. Rockfall and slump-ing due to the weathering could in some places release fiints, hornstones and radiolarites gathering together with the Calcerous debris at their foot (Alexandrowicz 1956, llf.; Gerlach 1976, 94).

Ali varieties of siliceous rock deposits in the condi-tion of the primeval vcgetation were revealed in the result of soil creep and landslides on maturę slopes with angles ranging from 2° to 45°. Those processes under natural conditions are morę unusual than in land-scape which has been effected by man (Bukowy 1956, 46 f., Tyczyńska 1968, 51-54; Gerlach 1976, 83 f.). In the Atlantic and Subboreal periods they were pro-bably only accompanying phenomena to the action of rain waters, seas, rivers and streams.

Fig. 19. Ojców National Park. Korytania ravine. Large, wcathered Jurassic-Cracow flint nodule, crodcd by stream which at times

flows along the bot tom of the ravine

Photo by F.M.Stępniowski

A morę important role should be attributed to the process of so-called “uprooting of trees” connected with the wind action on the territories covered with forests or single trees (Gerlach 1976, 46, 88). It means pulling out together with roots of falling trees of considerable amounts — sometimes scveral m³ — of soil and its bedrock. These phenomena occur most often on slopes. The materiał pulled out by the roots was translocated and placed at a smali distance from thc place where the trec grew. In the place of extraction, smali depres-sions approx. 60 cm deep and up to 4 m across are found. Falling trees could bring into daylight the siliceous rocks, whereever they occurred near the soil sur-face. That would be one of the most important ways of revealing the presence of flint raw materiał, taking into account the primeval forest vegctation on the terri-tory of Central Europę. A. L. Armstrong drew attention to this at the mines of Grime’s Graves in England (1926, 101).

Soil and ground movements due to freezing and thawing were eąually important, and brought to the sur-face siliceous rocks found in the loose Tertiary eluvial or Quaternary deposits (Bac 1951, 52).

These agents were interrelated and often it would be difiicult to State which of them were primary and which secondary. We can assume that the mining of some raw materials, and the lack of interest in others was most freąucntly due to a deliberate choice, depending on the technical fcatures of the given raw materiał, on the type of deposit, and the cultural tradition. Exploitation of only certain flint raw materials in the region of the Holy Cross Mountains or in the Cracow Upland, and the complete lack of interest in others can serve as an cxam-ple. Exploitation of particular flint layers at the Rijck-holt—St.Geertruid and Krzemionki Opatowskie mines has similar significance. The interest in a specific deposit did not stop pcople occasionally gathering suitable rocks, that they found chance.