Lithologic characteristics of gravels of the Libotínský potok Stream (Podbeskydská pahorkatina Hilly Land)

The paper describes downstream relationships between local sediment inputs, petrology and grain-size of bed sediments with measured grains of Di≥10 mm in the flysch-based Libotínský potok Stream (Podbeskydská pahorkatina Hilly Land, Outer Western Carpathians). Downstream increase of sandstone pebble share in bed sediments reflects their higher resistance and their continual delivery into the channel. Teschenites have their source zones in the upper part of studied basin and a gradual downstream decrease to ca. 15-20% of total pebble counts is observed. Soft claystones decrease from ca. 50% in the upper part to 20% in the lowermost parts. Grain-sizes of D90 and D75 percentiles fluctuate without any significant downstream trend and are independent on the ratio of soft rocks in bed sediments. Lower percentiles indicated almost constant values. Calculated gradation coefficient of bed sediments points up on the poor correlation with the D25 grain-size percentile.