Commune: Suwałki (pow. suwalski, woj. podlaskie) , Suwałki (pow. Suwałki, woj. podlaskie)
Framework element or context represented:
Pleistocene landforms.
Primary geological/geomorphological interest:
Morphology of post-pingo form.
Comparative assessment justification:
The relict of the ancient Pleistocene pingo is exceptionally well-preserved. Such forms described from other localities in Europe (also in Poland) are indistinctly exposed in the relief.
Protection status and accessibility:
Post-pingo form is protected within Wigry National Park (15 085 ha) established at 1989. Tourist trails run within the Park around the Lake Wigry (21,7 km²) and along some small lakes called “suchary”, but not near the Lake Petronajć.
Character of site: Landform.
Area: 1.71 ha
Altitude: 135-150 m a.s.l.
Lithology: gravels, sands, other sedimentary rocks, peats
Discipline: Geomorphology, Stratigraphy of Quaternary
Process Age: Pleistocene, *all periods
Bedrock Age: Quaternary, *all periods
Description of primary interest:
The Lake Pietronajć in the Wigry National Park (NE Poland) is located in the depression of the remnant after the pingo degradation. It is a post-pingo form. The lake is nearly round, reaches 140 m in diameter and up to 6.6 m deep. It is situated in the Wiatrołuża river valley formed by the outflow of subglacial waters coming from the melting ice sheet at the end of the last glaciation. Water level in the lake is considerably higher than in the Wiatrołuża river. In the bottom of the lake noncalcareous gyttja occur. The lake is surrounded by semicircular rampart 10-18 m high above water level and 80-105 m wide. The inner slopes are inclined 15-30º towards the lake, while outer ones are slightly steeper, 20-35º. The whole rampart is of the similar width and it does not show any traces of erosion even in the narrowest part of the valley, which suggests that it is younger than Wiatrołuża valley. The lower part of the rampart is built of fine-grained sand intercalated by sand with gravels. The inclination of these sediments (37-47º) indicates on the postsedimentary disturbations. The presence of young peats in the bottom lake sediments (6410 BP) can indicate that the described form is not pingo, but meteorite crater. However microgravimetric profiles shows that it could not be iron meteorite. Futhermore meteoritic craters of the Holocene age are very rare, and ramparts surrounding the lake Pietronajć aredisproportionatelyhigh in comparison with craters produced by meteorites.
Literature:
KOSTROWICKI A.S. (ed.) 1988–A geo-ecological study of the Wigry Lakes region (English sum.) Prace Geogr. IGiPZ PAN 147, pp 134. MÜLLER F. 1959–Beobachtungen über Pingos. Medd. om Groenland 153, 3: 1-127. RUTKOWSKI J., KRÓL K., KRZYSZTOFIAK L. 2001–Lake Pietronajć in the Wigry National Park - origin and the present state (English sum.). Chrońmy Przyrodę Ojczystą 57, 2: 61-72. RUTKOWSKI J., KRÓL K., LEMBERGER M. 1998–The pingo remnant in the Suwałki lake region (NE Poland). Quaternary Stud. Pol. 15: 55-60. WIEGANT G. 1965–Fossilepingos in Mitteleuropa. Wurzburger Geogr. Arbeit. 16: 1-152.