Die Rekonstruktion der Gewässerlandschaft auf der Basis dieser Werte bleibt auch bei genauer Datierung der Wasserstände problematisch, wie Untersuchungen zwischen dem Festlandufer des Plauer Sees und der Kohlinsel gezeigt haben. Nördlich der dokumentierten Brückentrasse ist der See nur 1,6-1,8 m tief. Ein um 2 m, d.h. auf den
slawenzeitlichen Wasserstand abgesenkter Pegel hätte zur Folge, dass die Insel über einen Damm mit dem Festland verbunden wäre. Unterwasserarchäologische Sondagen haben aber belegen können, dass dieser „Damm“ ausschließlich aus limnischen Sedimenten aufgebaut ist (Bleile 2008, S. 67). Ralf Bleile
Abstract: In the second half of the 7th century AD Slavonic settlers reached the presumably widely deserted area of Northern Germany. Their expansion ended in the west on the River Elbe and further to the north possibly in the course of the River Schwentine, to an area which marked the border between the German empire and the Slavonic tribes of the Abodriten. In medieval chronicles this borderline is called the „limes Saxoniae“. For the Slavonics, settling close to lake shores, water level variations had in the long term serious effects on the development of the settlement scenery as the explosive increase of island settlements and island castles is pointing out since the 10th century AD (Fig. 16). The 10th century AD is valid as the time of the medieval climate optimum with relatively high average temperatures and low precipitation. At the end of this century, for example, Scandinavian settlers hit Greenland. Dendrochronological investigations showed that the annual tree rings of oaks were coined in the area of the lower River Oder in the first half of the 10th century and in the area of the Lake Plauer See in Mecklenburg at the end of the 10th century. Furthermore archaeological findings of a wooden trail and a bridge joining in it which led to an island castle in the Lake Teterower See (Mecklenburg) give an impressive instruction to sinking water levels in the course of the 10th century. In Lake Plauer See existed a settlement on the Island Kohlinsel between the 10th-12th century AD which was developed at the latest at the end of the 11th century to the castle (“castrum Cuscin”). A little bit more than 30 m before the today’s north shore of the island there is in a water depth of nearly 2 m an old wooden embankment in which still thin oaken and birch posts of a palisade of the 11th century stand (Fig. 18). At this point ends the Slavonic cultural layer of the island settlement which lies immediately on a calcareous gyttja. This circumstance can be explained with the fact that the settlement of the Island Kohlinsel grasped areas in the second half of the 10th century at least on the today’s north shore which had liked scarcely drily. The palisade served as a protection against the erosion which the rising lake level caused (Bleile 2008, p. 34-40). Before the island, as well as on the land side there are remains of wooden plank ways till 2 m water depth. They date to the end of 10th and the 11th century AD. However, in the whole ways course also posts stand which are to be appealed as remains of a bridge of the second half of the 12th century. The rising water level of Lake Plauer See in the 12th century cannot be explained yet with the construction by water mills, because the first mills were built in Plau town at the earliest in decades after 1200 AD. The construction of water mills in the Slavonic settled part of North Germany falls in the time of the German juridical transformation since the last decades of the 12th century. The first mills originated at the cloisters and in the still young towns. The oldest water mills are known in the Brandenburg Mark already in the seventies and eighties of the 12th century. Since the 13th century the water mill foundings also increase for the Mecklenburg area. In spite of the regulations in the 19th and 20th century the water levels of most Northeast German lakes lie even today always on an average 1-2 m above the Slavonic lake levels (Fig. 17, Bleile 2005a).
STOP 4
Glazifluvialer Übergangsbereich der Pom- merschen Endmoräne in der Kiesgrube Charlottenthal (Mecklenburg-Vorpommern) – Sedimentologische Untersuchungen und Lithostratigraphie von Tills Sedimentological investigations and lithos- tratigraphy of tills in a transitional fan of Pomeranian Phase at Charlottenthal gravel pit
Die Landschaft um Charlottenthal wird von einer stark hügeligen Landschaft um 53-58 m NN im Bereich der Pommerschen Endmoräne geprägt (Schulz, 1963). Der Aufschluss der Kiesgrube Charlottenthal liegt im Übergangsbereich des sub- und inglazialen Schmelzwassersystems zur proglazialen Zone der südlich angrenzenden, durch eine Vielzahl von Seen gegliederte Sanderzone. Im zentralen Bereich des Kiesgruben-Restsees wird bei ca. 49 m NN
Exkursion A ¬ Mecklenburgische Seenplatte und Wismar-Bucht
ein nach N einfallender unterer Till von ca. 5-15 m mächtigen glazifluvialen Kiessanden (Kiesanteil 5-29%, GFE, 1998, 2000) überlagert. Im nördlichen Abbaubereich oberhalb 50 m NN bedeckt ein lückenhaft auftretender, 1-3 m mächtiger oberer Till die liegende glazifluviale Abfolge.
Sedimentologie
Die glazifluviale Folge ist in zwei Lithofaziesbereiche untergliedert. Im Bereich der nördlichen Aufschlusswand sind im unteren Profilteil trogförmig-kreuzgeschichtete Sande (Abb. 19, Lithofazies: St) und flach-kreuzgeschichtete Sande (Sp) mit gering wechselnden Kiesanteilen aufgeschlossen. Über diesen kiesigen Sanden liegen massive Lagen von Kiesen und steinigen Kieslagen auf (GRm, GPm and GCm), horizontal-geschichtete Grobsande (Sh) und Feinsande in kleindimensionaler Rippelschichtung (Src). Die linsenförmigen Lagen weisen durchschnittliche Mächtigkeiten zwischen 10-30 cm (Src, Sp, GRm, GPm, GCm) und 50 cm (Sp)
27
A