Commune: Janowice Wielkie (pow. jeleniogórski, woj. dolnośląskie)
Framework element or context represented:
Lithological diversity of a typical intrusive rock for Mid-European mountains and characteristic rock landforms developed from granite.
Primary geological/geomorphological interest:
Granite residual landform (tor) with two petrological variants of granite exposure.
Comparative assessment justification:
A good example of a residual tor, with clear relationship between geology and morphology. One of the best exposures of a contact zone within a granite massif in the Sudetes.
Protection status and accessibility:
No special protection. The object is located within the boundaries of the Rudawy Landscape Park (Rudawski Park Krajobrazowy). Access via a marked trail.
Character of site: Natural outcrop
Area: 0.25 ha
Altitude: 570 m a.s.l.
Lithology: granitoids
Discipline: Geomorphology, Petrography
Process Age: Neogene, Paleogene, *all periods
Bedrock Age: Carboniferous, *all periods
Description of primary interest:
Piec is one of many residual granite outcrops in the northern part of the Rudawy Janowickie range, but combines two important aspects from the point of view of geodiversity. First, two granite variants are exposed within the outcrop, offering a rare opportunity to examine the contact zone, establish the history of intrusive processes, and infer palaeotemperatures at the time of intrusion. The lower part is built of densely jointed, fine-grained porphyritic granite with aplite veins and biolite schlieren, the upper one is made of massive medium-grained granite. Contact phenomena indicate that the fine-grained granite is younger. Second, Piec is one of the most spectacular rock outcrops in the whole Karkonosze-Izera granite massif and its unusual shape reflects the presence of two lithological variants of host granite. The massive upper part forms a huge overhand above a recess developed in jointed fine-grained granite, thus illustrating bedrock control on the shape of granite tors. The total height of the outcrop is 20 m, hence it is one of the highest in the massif.
Literature:
MIERZEJEWSKI M.P., WOJNAR B. 1986–A sequence of two granitic masses and their crystalization temperatures at the endocontacts (English sum.). Geol. Sudetica 21(1): 231-258.