Hradiště near Semily

Series of rock outcrops.

Melaphyres (andesitoids) are exposed by a road cut in the length of about 500 m and a height of max. 7 m. Their contact with sedimentary rocks visible at this site is one of the best in the Krkonoše Piedmont Basin. Deposits of the Vrchlabí Formation, reddish-brown silty claystones and clayey siltstones, are exposed primarily in the northern part of the exposure. The southern part is dominated by amygdaloidal, locally massive melaphyres, pertaining to the lower andesitoid sheet of the Vrchlabí Formation. The amygdules are up to 10 cm in diameter, being composed mostly of chalcedony, agate, rarely of crystals of quartz, amethyst, aragonite, calcite, and dolomite. Some cracks are filled with calcite veins and rarely also by black asphalt-like matter.


17_ Hradiste u Semil foto Ludek Antos

17_ Hradiste u Semil foto Ludek Antos

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