Moränstratigrafisk undersökning i kustklintar, NV Polen

Abstract

Summary: This study is a part of the project "Lithostratigraphy and glacial dynamics during the Pomerian Phase". The objective is to solve the problems concerning the deglaciation of the south Baltic area during the last glaciation.
The Polish Baltic coast is under heavy erosion from the seawaves. Steep morainic cliffs, often more than 10 meters high, offer excellent sections.
A clear difference in colour can be seen almost everywhere in the cliffs, a brown boulder clay on the top, 3-4 meters thick, and a grey boulder clay below. They have formerly been mapped as two different tills. The locality in Sliwin was studied in the early sixties. It was then proposed that the whole sequence consisted of one till and that the brown colour was a result of weathering (Karczewski 1961). This study was carried out through sampling with fixed intervalls. The rock composition was investigated and four groups were identified: precambrian rock, quartz, carbonate rocks and other sedimentary rocktypes.
The purpose of the present study was to investigate the profile in detail. A subdivision of rock types should also be more diversified.
The locality is situated in Sliwin about 50 km east of Swinoujscie. The section is 10 meters high and clear from vegetation and scree. It consists of a matrix supported diamicton. The lower part is grey and homogenus, with a sandy silty grain-size distribution. 4-6 meters below the ground surface the diamicton changes colour to brown och rustybrown lenses appears. There is no significant change in grain-size. Fabric analyses have been carried out in ten spots at nine levels. The orientation is generally from NE/NW, but the strength is usally low. On the top there is a 20 centimeters thick layer of eolian sand which has not been investigated in this work.
In Lukecin, about 40 km east of Swinoujscie a smaller section was also investigated. This section is 6 meters high. The material here is a grey diamicton with high clay content. The grain-size distribution is uniform throughout the section, but the content of clay and silt is much higher than in Sliwin. The diamicton in Lukecin is heterogeneous and has a lot of sand and silt lenses. One lens is much bigger than the others, about 4 X l meters and shows signs of tectonic influence. The whole lens dips in the SE direction, but the internal structure is more complicated.
Both sections have been sampled for analyse of rock composition. The samples were taken at the same levels as the fabric analyses were carried out. Determination was made under microscope and fractions bigger than 2.8 mm were used. Between 480 and 750 particles were counted and determined in each sample. Ten different rock-types were found in rates over 2%. In Sliwin the difference between the samp1es is very small, except that the carbonate rocks disappear in the uppermost meters. No change is recorded at the level of colour change a few meters below. There is no big difference betweeen the two sections, crystalline rocks and Paleozoic limestone dominate. In Lukecin there is a slightly higher rate of limestone than in Sliwin, and that corresponds with the higher carbonate content. Other important rocks are Jotnian and Cambrian sandstones. All these are transported a long way and have their outcrops in the area of the islands of Öland and Gotland. Material from the south Baltic is more rare. Cretaceous glaukonite sands and chalk were found, but in small amounts. Dolomite derived from the eastern part of the Baltic depression has also been found in small quantities.
There is nothing in Sliwin that indicates that the section should consist of more than one massive diamicton unit. All investigations, fabric analyses, rock composition and detailed investigation of the profile centimeter by centimeter, shows no discordance or any differences between top and bottom that can not be explained by weathering. If the diamcton was deposited as a melt out till or flow till sorted Laminae or flow structures would be expected, but they have not been found. The most likely interpretation of this thick, massive diamicton bed is that it is a logdement till.
The section in Lukecin has sand and silt lenses and laminae. They could be formed by melt out from stagnant ice. The disturbances could then be explained by compaction and flow. Another possible explanation is tectonics caused by an overriding active ice. To get the complete picture of the stratigraphy and the paleoenviromental development larger regional investigation is required.

• author: Johansson, Per
• supervisor: Kärstin Malmberg Persson; Erik Lagerlund
• organization: Department of Geology
• year: 1992
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: kustklint, moränstratigrafi, geografi, geologi, Polen
• publication/series: Examensarbeten i geologi vid Lunds universitet
• report number: 41
• language: Swedish
• additional info: Kärstin Malmberg Persson, Lunds universitet.
• id: 2370619
• date added to LUP: 2012-06-25 14:04:30
• date last changed: 2012-06-25 14:05:34