Yoldia Sea
Encyclopedia
Yoldia Sea 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 Weichsel glaciation. Dates for the Yoldia sea are obtained mainly by radiocarbon dating material from ancient sediments and shore lines and from clay-varve chronology.
They tend to vary by as much as a thousand years, but a good estimate is 10,300 – 9500 radiocarbon years BP, equivalent to ca 11,700-10,700 calendar years BP. The sea ended gradually when isostatic rise of Scandinavia
closed or nearly closed its effluents, altering 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 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, a process complete by about 10,300 BP (radiocarbon years). 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 see level the difference in salinity caused a backflow from the North Sea
, creating saline regions in which the marine bivalve Yoldia flourished. This phase lasted until about 10,000 BP.
Subsequently, increased melting of the glacier provided additional fresh water and the lake became stratified (meromictic), with salt water on the bottom and fresh on top. Over 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.
At about 10,000 BP, the exit continued to rise and the lake/sea broke through Denmark
creating the first Great Belt
channels. The total opening was less than 1 km wide and included two channels at the northern end. The Great Belt channels was blocked again by rising land from the post-glacial rebound
that created Ancylus Lake.
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 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 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.
Baltic Sea
The Baltic Sea is a brackish mediterranean sea located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. It is bounded by the Scandinavian Peninsula, the mainland of Europe, and the Danish islands. It drains into the Kattegat by way of the Øresund, the Great Belt and...
basin that prevailed after the Baltic ice lake
Baltic ice lake
The Baltic ice lake is a name given by geologists to a freshwater lake that gradually formed in the Baltic Sea basin as glaciation retreated from that region at the end of the Pleistocene. The lake, dated to 12,600-10,300 BP, is roughly contemporaneous with the three Pleistocene Blytt-Sernander...
was drained to sea level during the Weichsel glaciation. Dates for the Yoldia sea are obtained mainly by radiocarbon dating material from ancient sediments and shore lines and from clay-varve chronology.
They tend to vary by as much as a thousand years, but a good estimate is 10,300 – 9500 radiocarbon years BP, equivalent to ca 11,700-10,700 calendar years BP. The sea ended gradually when isostatic rise of Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
closed or nearly closed its effluents, altering the balance between saline and fresh water. The Yoldia Sea became Ancylus Lake
Ancylus Lake
Ancylus lake is a name given by geologists to the body of fresh water that replaced the Yoldia Sea after the latter had been severed from its saline intake across central Sweden by the isostatic rise of south Scandinavian landforms. The dates are approximately 9500-8000 BP calibrated, during the...
. 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
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
. This bivalve requires cold saline water.
It characterizes the middle phase of the Yoldia Sea, during which saline water poured into the Baltic, before the acceleration of glacial melting.
Description
Littorina Sea
Littorina Sea is a geological brackish-water stage of the Baltic Sea, which existed around 7500–4000 BP and followed the Mastogloia Sea, transitional stage of the Ancylus Lake...
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 – fresh water proglacial lakeProglacial lakeIn geology, a proglacial lake is a lake formed either by the damming action of a moraine or ice dam during the retreat of a melting glacier, or by meltwater trapped against an ice sheet due to isostatic depression of the crust around the ice...
with level greater than sea level – dammed by glacial ice until the ice dam broke free at the north slope of BillingenBillingenBillingen is the largest of the thirteen mesas in the Swedish county of Västra Götaland, with a maximum altitude of . The mesa extends in a north-southerly direct with a length of and a width of ....
uplands – the lake level then dropped ~ 26 meters to sea level - ~ 10,000 years before the present (ΒP). - Transition period - Between the Baltic Ice Lake and the Yoldia Sea there was a transient lake stage before the ingression of salt water. This lasted ~300 years (292 - 309 annual deposition varveVarveA varve is an annual layer of sediment or sedimentary rock.The word 'varve' is derived from the Swedish word varv whose meanings and connotations include 'revolution', 'in layers', and 'circle'. The term first appeared as Hvarfig lera on the first map produced by the Geological Survey of Sweden in...
s are seen in the geologic record, depending on where measured). - The Yoldia Sea – a short lived connection with the sea across south-central Sweden over the Närke strait – approximately 10,000 to 9,600 BP.
- The Ancylus Lake – creation of a fresh water lake through uplift, which blocked the Närke strait- 9,600 to 7,800 ΒP.
- The Littorina SeaLittorina SeaLittorina Sea is a geological brackish-water stage of the Baltic Sea, which existed around 7500–4000 BP and followed the Mastogloia Sea, transitional stage of the Ancylus Lake...
– with the rise in sea level and the submergence of the Øresund strait, the Baltic again communicated with the North Sea beginning ~ 7,800 ΒP to present. This is sometimes split into substages: - The Mastogloia SeaMastogloia SeaThe Mastogloia Sea is one of the prehistoric stages of the Baltic Sea in its development after the last ice age. This took place ca. 8000 years ago following the Ancylus Lake stage and preceding the Littorina Sea stage....
- a substage sometimes used to distinguish the period between 8000 and 7000 years ago when the Baltic became distinctly brackish - during this period the English Channel and the Danish straits circulation was established, increasing Atlantic water inflow. - The Limnea Sea – a substage sometimes used to distinguish the transition of the Baltic Sea to a more stagnant phase, which currently exists – about 2,500 BP.
The Baltic Ice Lake came to an end when it overflowed through central Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
and drained, a process complete by about 10,300 BP (radiocarbon years). The straits through the present Stockholm region (via Lake Vänern
Vänern
Vänern is the largest lake in Sweden, the largest lake in the EU and the third largest lake in Europe after Ladoga and Onega in Russia. It is located in the provinces of Västergötland, Dalsland, and Värmland in the southwest of the country.- History :...
and the Strait of Närke
Närke
' is a Swedish traditional province, or landskap, situated in Svealand in south central Sweden. It is bordered by Västmanland to the north, Södermanland to the east, Östergötland to the southeast, Västergötland to the southwest, and Värmland to the northwest...
) to the Atlantic were the only outlet at that time. When lake level reached see level the difference in salinity caused a backflow from the North Sea
North Sea
In the southwest, beyond the Straits of Dover, the North Sea becomes the English Channel connecting to the Atlantic Ocean. In the east, it connects to the Baltic Sea via the Skagerrak and Kattegat, narrow straits that separate Denmark from Norway and Sweden respectively...
, creating saline regions in which the marine bivalve Yoldia flourished. This phase lasted until about 10,000 BP.
Subsequently, increased melting of the glacier provided additional fresh water and the lake became stratified (meromictic), with salt water on the bottom and fresh on top. Over 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.
At about 10,000 BP, the exit continued to rise and the lake/sea broke through Denmark
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
creating the first Great Belt
Great Belt
The Great Belt is a strait between the main Danish islands of Zealand and Funen . Effectively dividing Denmark in two, the Belt was served by the Great Belt ferries from the late 19th century until the islands were connected by the Great Belt Fixed Link in 1997–98.-Geography:The Great Belt is the...
channels. The total opening was less than 1 km wide and included two channels at the northern end. The Great Belt channels was blocked again by rising land from the post-glacial rebound
Post-glacial rebound
Post-glacial rebound is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period, through a process known as isostasy...
that created Ancylus Lake.
Geographically, the Gulf of Bothnia
Gulf of Bothnia
The Gulf of Bothnia is the northernmost arm of the Baltic Sea. It is situated between Finland's west coast and Sweden's east coast. In the south of the gulf lie the Åland Islands, between the Sea of Åland and the Archipelago Sea.-Name:...
remained under the ice. The Gulf of Finland
Gulf of Finland
The Gulf of Finland is the easternmost arm of the Baltic Sea. It extends between Finland and Estonia all the way to Saint Petersburg in Russia, where the river Neva drains into it. Other major cities around the gulf include Helsinki and Tallinn...
was open but most of Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...
was an archipelago
Archipelago
An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...
, over which debris carried by glacial streams gradually spread. A land bridge joined Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
to southern Sweden through Denmark. Relieved of its weight of ice, Finland rose gradually and unevenly from 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
Neva River
The Neva is a river in northwestern Russia flowing from Lake Ladoga through the western part of Leningrad Oblast to the Neva Bay of the Gulf of Finland. Despite its modest length , it is the third largest river in Europe in terms of average discharge .The Neva is the only river flowing from Lake...
connected Yoldia Sea to Lake Ladoga
Lake Ladoga
Lake Ladoga is a freshwater lake located in the Republic of Karelia and Leningrad Oblast in northwestern Russia, not far from Saint Petersburg. It is the largest lake in Europe, and the 14th largest lake by area in the world.-Geography:...
.
The Yoldia Sea existed entirely within the Boreal
Boreal (period)
In paleoclimatology of the Holocene, the Boreal was the first of the Blytt-Sernander sequence of north European climatic phases that were originally based on the study of Danish peat bogs, named for Axel Blytt and Rutger Sernander, who first established the sequence. In peat bog sediments, the...
Blytt-Sernander
Blytt-Sernander
The Blytt-Sernander classification, or sequence, is a series of north European climatic periods or phases based on the study of Danish peat bogs by Axel Blytt and Rutger Sernander...
period. The forests and species lining its shores were boreal. Mesolithic
Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....
cultures continued to occupy Denmark/south Sweden and the southern shores of the sea. The sea as an ecologic system came to an end when Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...
rose sufficiently to block the flow through the Stockholm area and the saline balance shifted toward a lacustrine
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
ecology once again.