Ancylus Lake is a name given by geologists to a large freshwater lake that existed in northern Europe approximately from 9500 to 8000 years BC being in effect one of various predecessors to the modern Baltic Sea .
21-592: The Ancylus Lake replaced the Yoldia Sea after the latter had been severed from its saline intake across a seaway along the Central Swedish lowland , roughly between Gothenburg and Stockholm . The cutoff was the result of isostatic rise being faster than the concurrent post-glacial sea level rise . In the words of Svante Björck the Ancylus Lake "is perhaps the most enigmatic (and discussed) of
42-766: A backflow from the North Sea , creating saline regions in which the marine bivalve Yoldia flourished. This was the Yoldia Sea. The Yoldia Sea existed from 11.7 ka BP, but it took about 400 years before the brackish phase that lasted from 11.3 to 11.1 ka BP. Geographically, the Gulf of Bothnia remained under the ice. The Gulf of Finland was open but most of Finland was an archipelago , over which debris carried by glacial streams gradually spread. A land bridge joined Germany to southern Sweden through Denmark. Relieved of its weight of ice, Finland rose gradually and unevenly from
63-638: Is a name given by geologists to a variable brackish water stage in the Baltic Sea basin that prevailed after the Baltic Ice Lake was drained to sea level during the Weichselian glaciation . Dates for the Yoldia sea are obtained mainly by radiocarbon dating material from ancient sediments and shore lines and from clay-varve chronology . Such dates tend to vary by as much as a thousand years in
84-521: Is general agreement that the drainage process only lasted about a year but no agreement as to when salt water mixing was well established as this depended on factors such as world sea level raise. The straits through the present Stockholm region (via Lake Vänern and the Strait of Närke ) to the Atlantic were the only outlet at that time. When lake level reached sea level the difference in salinity caused
105-706: The Littorina Sea when rising sea levels broke through the Dana River forming the Great Belt. This transformation was gradual as salt-water had begun to enter the Ancylus Lake 8800 years B.P. The salt-water that entered the lake resulted in episodic brackish water pulses. The final end of the Ancylus Lake, however, came 7800–7200 year B.C. when Øresund was flooded causing a massive inflow of salt-water. Shorelines of Ancylus Lake can be found today at c. 60 m above sea level in southern Finland and at c. 200 m near
126-440: The Ancylus Lake. Svea River was finally dismissed in 1981 when potholes there were found to predate the lake. The demise of Svea River led authors in the late 1970s and 1980s to revisit the idea that the fresh-water Ancylus Lake was at sea level. Further studies confirmed then that Vänern was part of the lake and that it was above sea level, dismissing the idea of a sea-level lake a second time. Yoldia Sea Yoldia Sea
147-667: The Svea River canyon was the outlet of the Ancylus Lake gradually lost ground by the works of Sten Florin, Astrid Cleve and Curt Fredén . In 1927 Cleve who was already "an outcast of the geological community" commented in an opinion piece in Svenska Dagbladet on a proposal of making Svea River a national monument. She supported the idea of protecting the area but criticized the established interpretation of Munthe and von Post. Munthe replied in Dagens Nyheter and
168-612: The Yoldia Sea, during which saline water poured into the Baltic, before the acceleration of glacial melting. The Baltic Ice Lake , the Yoldia Sea, the Ancylus Lake and the Littorina Sea are four recognized stages in the postglacial progression of the Baltic basin – there are also transition periods which can be considered as substages. From earliest to most recent they run: The Baltic Ice Lake came to an end when it overflowed through central Sweden and drained. There
189-412: The balance between saline and fresh water. The Yoldia Sea became Ancylus Lake . The Yoldia Sea stage had three phases of which only the middle phase had brackish water. The name of the sea is adapted from the obsolete name of the bivalve, Portlandia arctica (previously known as Yoldia arctica ), found around Stockholm . This bivalve requires cold saline water. It characterizes the middle phase of
210-475: The debate went over to a personal quarrel in two more newspaper letters in January 1928. Cleve outlined her ideas for Svea River and Ancylus Lake in detail in 1930 making an alternative and intricate theory involving tectonic movements. By 1946 she had changed mind as she then proposed an altogether different theory claiming the Svea River canyons and potholes formed by subglacial drainage and had nothing to do with
231-555: The existence of the lake. Geologists had until then subscribed to a simple scheme for the evolution of the Baltic Sea where small local ice-lakes were succeeded by the Yoldia Sea that then evolved directly to the Littorina Sea . The lake was named by Gerard De Geer in 1890 after the fossils. The lack of an obvious outlet of the lake led to intermittent debates involving not only Munthe and De Geer but also Ernst Antevs , Arvid Högbom , Axel Gavelin , N.O. Holst and H. Hedström. As
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#1732779724574252-458: The lake level over hundreds of years, which then continued at a slower pace. Another consequence of the lowering of the lake and isostatic uplift was that a north-south land bridge formed between Lake Vänern and the Ancylus Lake effectively making Lake Vänern a separate basin. The Ancylus Lake existed from approximately 9500 to 8000 years B.C. calibrated, during the Boreal period . The lake became
273-521: The lake tipping over a till substrate at what is now the Great Belt in Denmark. Being located no less than 10 m above sea level the lake began thus to drain to the sea through the Dana River between 9000 and 8900 years B.C. The formation of the Dana River is thought to have caused a dramatic erosion of sediments, peatlands and forests along its path. This led initially to a relatively rapid fall in
294-413: The lake/sea broke through Denmark creating the first Great Belt channels and the Dana River along the new outlet. The total opening was less than 1 km (0.62 mi) wide and included two channels at the northern end. This likely led to an initial lowering of the Ancylus Lake by about 5 m (16 ft). At about 9.8 ka BP, sea level became higher than the lake level, and saline water began to enter
315-443: The life of the sea and from location to location the salinity was a variable. Whether it is possible to speak of stages of salinity that would apply uniformly to the whole sea is debatable. The land uplift in south-central Sweden as the glaciers retreated, stopped the water inflow from the world sea by 10.7 ka BP. A rapid Ancylus Lake transgression started then about 10.7 ka BP, and reached its highstand about 10.3 ka BP. At 10.2 ka BP
336-470: The literature, but were corrected in 2021 for the whole of the Holocene. The sea can not have existed before the final drainage to sea level of the Baltic Ice Lake in 11,620 cal. year BP . Current rounded estimates are 11.7 to 10.7 ka BP equivalent to about 9,750–8,750 calendar years BCE. The sea ended gradually when isostatic rise of Scandinavia closed or nearly closed its effluents, altering
357-410: The many Baltic stages". The lake's outlet and elevation relative to sea-level was for long time surrounded by controversy. It is now known that the lake was above sea level, included Lake Vänern , and drained westward through three outlets at Göta Älv , Uddevalla and Otteid . As result of the continued isostatic uplift of Sweden, the outlets in central Sweden were severed. In turn this resulted in
378-437: The northern Gulf of Bothnia . In 1887 Henrik Munthe was the first geologist to draw the conclusion that the Baltic Sea must once have been a freshwater lake. Munthe did so after finding fossils of the freshwater snail Ancylus fluviatilis in sediments. While these fossils were also found slightly before him by other geologists they thought they belonged to rivers, small former lakes or brackish water, failing thus to realize
399-542: The outlet was lacking there were doubts on whether Lake Vänern had been part of the lake or not, and on the position of its outlet or whether an outlet actually existed considering the lake could have been at sea level. Lennart von Post discovered by accident a small canyon near Degerfors in 1923 which he thought could be the elusive outlet. This came with time to be known as Svea River. Von Post collaborated initially with Munthe to study Svea River but their collaboration fell apart by 1927 over personal issues. The idea that
420-575: The sea. Parts of the Yoldia shoreline are above sea level today while other parts remain below. The Yoldia Sea toward its end was about 30m below current sea level. A channel at the location of the Neva River connected Yoldia Sea to Lake Ladoga . The Yoldia Sea existed entirely within the Boreal Blytt–Sernander period . The forests and species lining its shores were boreal. Mesolithic cultures continued to occupy Denmark/south Sweden and
441-462: The southern shores of the sea. The sea as an ecologic system came to an end when Scandinavia rose sufficiently to block the flow through the Stockholm area and the saline balance shifted toward a lacustrine ecology once again. After formation, increased melting of ice provided additional fresh water and the sea became stratified ( meromictic ), with salt water on the bottom and fresh on top. Over
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