THE ENVIRONMENT OF AMBER FORMATION

Amber started formatting 55-40 million years ago (during Cenozoic and Paleocene periods). The amber-full woods grew in the southern and middle part of what is now Scandinavia and in the adjacent areas of the Baltic Sea bottom (the Baltic Sea started formatting around 13 thousand years ago). Coniferous woods grew in this territory and from their resin amber was formed.

In XIX  and  XX centuries most scientists stated, basing their statements on research of the inclusions found in amber, that the habitat of the amber-full woods is far greater, because the insects and plants found in amber are typical to tropical regions and flora and fauna from different climate zones can‘t co-exist in the same area.

Scientist O. Her when explaining in 1869 how plants and animals typical to tropical and middle climates appeared in amber, stated that amber woods spanned through a huge mountain range covering areas from Scandinavia to Middle Europe and rivers from all of these areas carried amber with insects and animals to the sea, thus the variations in amber inclusions found in one place.

H.Konvent in his 1890 work „Monograph about amber“ wrote that amber woods were dense, humid, dark and on their southern edges warmth-loving and even tropical plants grew. According to him almost all the trees were diseased. They were crippled by insects, parasite fungus, plants and various natural disasters (storms, thunders, fires, falling trees). While being constantly crippled these trees produced much resin which formed amber.

In 1915 the researcher of amber inclusions V. Vyler, while researching amber pieces with several or more inclusions, noticed that each of them contains insects of tropical and moderate climates. The scientist explained this fact – at the time of amber formation the tropical climate changed into the moderate one, thus the fauna is relict.

After summarizing previous scientists‘researches of insects, in 1942 an analyst of amber fauna K. Anders formulated a hypothesis that amber forests grew on mountains. On mountaintops and on north sides coniferous trees grew and warmth-loving trees – on the mountain bases and southern parts, that‘s why, according to the author, insects of various climate zones are found in amber.

Later amber inclusion researches regarding its varietal composition proved that the insects and plants specific to tropical and moderate climate zones existed simultaneously. This fact is explained by the researches of amber and climate: it‘s very hard to distinguish such climate zones typical today at the period of amber formation (paleogenic period). Climate research shows that during paleogenic period variations in temperature weren‘t apparent, so they didn‘t have much significance on the spread of flora.

During the growth of amber forests the climate was warm (average yearly temperature was around +20° C) and very humid. It‘s stated that it was very similar to the Mediterranean sea climate type characterized by apparent wet and dry seasons. The researcher of European climate during the paleogenic period V. Sinycin pointed out that at the present territory of Poland and Germany evergreen flora with a large addition of sub-tropical coniferous and deciduous trees was spread.

This zone reached Scandinavia where coniferous and broad-leaved deciduous flora dominated. Mediterranean plants (bayberry, mirth, palms) took second place there and coniferous trees were present from both moderate and sub-tropical climates. These circumstances explain the coexistence of various species and their integrated appearance in amber pieces. Current climate zones became clearer only after the amber formation processes were over.

The biggest part of amber forest grew in lower plain or a little hilly relief because insect species living in still water or swamps predominate in amber pieces. Only a very small part of the inclusions show that amber forest grew in mountainous regions. It is believed that this was the western-most part of the amber forest habitat.

There were many swamps, big deep lakes, numerous rivers and streams in the amber forest. The soil was similar to current tropical forest soil type. Amber forests grew on carbonaceous and sandy soil. The soil contained much humus, but it also was well aerated and drained. The forest floor was constituted of wood mould, leaves, thorns and continuous moss covering. On warm and damp climate conditions these remains decomposed rapidly and the decomposed remains were spread by atmospheric rainfall. Oxygen penetrating lower soil layers determined oxidation processes.

It‘s believed that amber forest was very similar to today’s Eastern Asian sub-tropical forests – very dense and dark at parts. Many various species of trees, bushes and other plants grew there. Those were the gigantic sequoias (50-80 m), oaks, chestnuts, many coniferous trees, many maples, fig trees, cypress family coniferous trees, small trees and bushes, dwarf palms and lianas. Moss, ferns and graminaceous plants rallied around the edges of the forest.

Amber trees grew in groups on higher areas and a big part was interblended with other trees. They grew on the edges of the forest, coasts of rivers and lakes and on mountain slopes. For this reason insects living in rivers and lakes are found together with forest plants in amber. Warm and very moist climate stimulate and intensive growth of fungus and other cryptogam plants which influenced changes in resin. Amber forests were populated by many sorts of insects, birds and mammals.

THE PHYSIOLOGY OF RESIN EMITION

Amber was produced by a certain type of pine Pinus succinifera. This is confirmed by the anatomic structure of the wood found in amber and chemical composition of amber. These pines had naturally typical features as well as influences on growth conditions to emit considerably higher amounts of sap when compared to modern pine trees (today there‘s not a single type of pine that would emit such amounts of resin or would be related to amber trees). The purpose of conifer sap is to protect the wood and the whole tree from unfavorable environmental influences – mostly from rot and parasites. The filled wood layers become resin and doesn‘t allow the tree to rot. Extremely high resin emission isn‘t normal, because a big part of the valuable materials needed for the tree to grow is used up to produce sap. For this reason the trees weaken and might even become extinct.

During the formation of amber (at the beginning of middle Eocene period) Europe‘s climate was changing: it became warmer and more humid. With the changing climate the positions of the climate zones changed as well. Pines best growing in the middle climate zone had to adapt to the changed environmental conditions. All conifer trees react to any climate change by either increasing or decreasing the amount of sap they produce. When climate started changing in the Paleocene period to the end of the Eocene period it changed to sub-tropical. Unstable climate, changed air temperature, increased humidity of the air and soil influenced the growth processes of conifer trees – amber tree sap emission increased and from this sap amber started to form.

Sap in conifer trees is accumulated and circulated in two types of sap vessels – longitudinal and transversal. Longitudinal sap vessels start at roots, continue though the trunk and end at the top of branches. Transversal sap vessels form in the tree‘s heart radius and go through the surface of the trunk. Tree bark only has the transversal sap vessels. Apart from longitudinal and transversal sap vessels timber often has pathological vessels that differ by structure and larger diameter. They form in damaged areas when the conifer trees grow under unfavorable conditions. Many pathological sap vessels were present at the amber producing pines.

When the sap vessel is full huge sap pressure is created that can‘t be barred by the vessel walls, they burst and the sap spills to the outside of the tree. The sap that stays in the wood starts to migrate to a lower pressure point and the condensing sap plugs the injured area and its spilling stops. Over time the tree rebuilds the lost sap amount, the sap fills the vessels and the plug on the injured area is pushed out – the sap starts running again. The running of the sap is repeated in cycles until on the tree trunk next to the injured area food materials are depleted or the spot is plugged with hardened sap and it grows over.

During the time amber formed optimal conditions predominated that stimulated the flow of sap: amber tree sap vessels were larger in diameter, the sap system more exuberant, the sap was more liquid because of the great amount of volatile terpenes (no less than 30%), the roots and the crown of the trees were lush, high air temperature and high humidity. Sap in amber trees were produced much more quickly than in modern conifer trees, their flow was intensive, the cycles frequent, but short.

Baltic amber is 50 million years ago (during the Eocene period) hardened conifer resin. It is though that at that time the whole Northern Europe was a single land piece also called Fenoskandia. Huge forests grew there. The accumulated sap from the forest soil was washed out by rivers and carried southwards to the sea. As time went by, because of oxidation and polymerization processes, the sap became amber. Baltic amber formed from the mentioned conifer trees over 2 million years acquiring various forms, colors and sometimes „accommodating“ various fossils.

According to scientists „amber colors and its clarity were influenced by the changes in the sap: evaporating elements from transparent sap could form many gaseous micro-bubbles that „clouded“ the sap (yellow amber)“.

If this process was especially intensive very great amounts of bubbles could form (up to 1 million of these bubbles) and so white amber was created.

Bluish shade of the amber originated when brazil (FeS2) impurities got into the sap that was on the ground. By the way, blue shade of amber is the rarest one.

Black amber was formed when resin mixed intensely with the soil, green – with plant parts.

Amber is a witness of Earth‘s deep historic past that reached us. According to the natural form of the amber pieces its forming processes can be established. They can be of inner or outer origin. Inner type of amber formed when sap filled the tree‘s inner gaps as well as in between bark and trunk; outer type formed when sap was leaking out of damaged areas.

The most interesting are amber drops „Amber tears“ that formed when sap drops broke away from the main flow that ran down the trunk. It is established that periodic flow of sap lay in layers – in such pieces most of the inclusions are found.

Inclusions (Latin – inclusus) are a frozen live organism (usually invertebrates, but also vertebrates are found). Plants and animals were preserved in such way 50 million years ago. Around 86% of inclusions are insects, 12% – spiders, 1,5% – other animals, 0,5% – plants. It is established that in amber inclusions the DNA was preserved even through 2 million years.

SAP FORMATION ON A TREE

Volatile terpene full sap (transparent, colorless fluid with pine smell that is constituted of carbohydrate found in sap) constantly seeped to the tree‘s surface. Here it was influenced by lower pressure so it became less soluble; the volatile terpenes were evaporating quickly because of environmental influence. In sap that was on the sunny side the terpenes evaporated quicker. From its gas many small bubbles formed and the sap got clouded. Gas bubbles moved in the liquid sap, joined one another so semi-transparent or cloudy sap zones appeared. In dense sap the bubbles stayed small, densely scattered, so clouded, yellowish or even white sap areas appeared.

The thick sap slowly flowed down the tree trunk different color and denseness zones mixed creating amber with various patterns and colors.

After most of the terpenes evaporated the sap melting temperature increased, so sun heat couldn‘t melt them anymore. The sap stuck to the trunk and totally hardened. All colors that appeared during the flow stayed and can be seen in amber. Sap that was evaporating very quickly in sunlight became foamy and formed the very common porous foam amber.

Terpenes from seeping sap that was in shade evaporated very slowly, so this sap hardened slowly and stayed clear. Oxidation process that was especially intense because of light, heat and ozone effects also had influence on the color of amber. The color of amber affected by oxidation is much darker than that of inner formed amber.

Microorganisms, organic and mineral acids and humidity didn‘t participate in the processes of this stage. Amber form sap changed a little differently. It‘s shown by the physical features and chemical composition. This sort of amber is very bright, sometimes even colorless because the sap didn‘t react with oxygen (there was no oxidation process). Terpenes didn‘t evaporate so the amber contains almost all the volatile components that reacted with other constituents, thus this sap is very clear.

AMBER MIGRATION AND CLUSTER FORMATION

Rain, rivers and sea waters that washed and flowed amber through long ages formed wide amber spread areal. Amber clusters formed in Southern Sweden, Semba peninsula, Southern England, Ukraine, Belarus, Poland, Germany, Denmark, The District of Kaliningrad, Lithuania and in a small part of Riga bay. Apart from this areal only isolated amber findings are found that were brought there by humans.

At the late Eocene period first amber clusters formed in the areas of the amber forests. Water started to fragment them and carry to the river delta‘s sediment at the Sempa peninsula and Southern Sweden. The biggest part of the amber settled together with the sand, clay, wood parts carried by the river at the front of the delta at the point where the flowing river water met the standing sea water. Amber layers created in this time and covered by the river sediment have survived to this day. The old diggers called these rocks were called „the blue earth“because of glauconitic (from Greek glaukos – greenish mineral hyrdomica) additives that colored these layers by greenish grey colour. At this finding spot the biggest amount of amber is found – from 0.5 to 2.5 kg in one cubic meter. The thickness of the layer at various depths is 7-8 meters. At the whole area (the Western part of the Sempa peninsula) there are several hundred tons of amber (around 90 % of all amber in the world).

During the Oligocene period the initial amber clusters were fragmented by river and sea currents further, the Eocene period Semba peninsula cluster was being washed away. This sea amber was spread through huge area: Germany, Poland, Belarus, and Ukraine.

During the Neocene period not many initial amber clusters were left, but they‘re still being eroded. Neocene rivers flowed through the Semba peninsula southwards carrying great amount of amber which clustered in Poland. Lots of it was dug up here during XVII-XVIII centuries.

Amber spread widely though the Kvarter period. Glaciers formed in Scandinavia creped through the landscape and totally destroyed the original cluster remains as well as largely destroyed clusters and finding-places of all periods. Accidental amber finds are found in arctic sediments around the Baltic Sea basin, Belarus and Ukraine territories. In Lithuania such finds can be detected at current lake shores (Platelių, Lūksto, Vištyčio, Dusios) and in sediments of formed arctic sediment adjacent basins (near Kaltinėnai, Kazlų Rūda, Marijampolė, Širvintos, Strėva).

From the destroyed amber-full sediment at the Sempa peninsula it mostly spread together with arctic sediment in the current District of Kaliningrad, North-Eastern Poland, partly in Belarus and Ukraine. The amber washed out of the sediment traveled with river Dnieper almost to the Black Sea.

After the arctic age a lot of amber was washed out by the currents and waves of the Baltic Sea when eroding the Semba peninsula. During the Litorine sea period (3500-300 B.C.) this process was mostly active when the sea level was 4-6 meter higher than the current one.

Currents that were close to shore carried the washed out amber northward and laid it in calmer and deeper lagoons and beach sand. One of the biggest lagoons separated from the sea by an underwater ridge was between Pervalka and Klaipeda, at the Northern part of the Curonian Lagoon. Dozens of tons of amber were accumulated here in the oozy sand sediment at the depths of 6-15 meters, which was exploited around Juodkrante over XIX century. Similar lagoons were around Šventoji, Liepaja and other places where beach swamps and lakes are present. Some amber is found up to Riga bay. North o fit amber is very rare.

On the Western end of the Baltic Sea at the Jutland peninsula most of the amber was accumulated during the melting of the arctic ice, where carried by the currents it reached even the Southern parts of England.

INNER MORPHOLOGICAL AMBER VARIETIES

1. Cortical amber

This is the most spread and varying morphological variety of amber (58%). The sap flowing onto the surface of the trunk created large clusters that slowly oozed down. They melted and hardened again while heated by the sun. Because of the heat volatile components evaporated, though because of the viscous sap mass not all gas was able to evaporate. Various currents mixed together when the sap was flowing down the trunk, so this outer amber is of various colors.

Cortical amber can be from few centimeters in size to big pieces weighing several kilograms.

Cortical type amber pieces are thick, on a transversal cut they’re convexed, with oval front part, with uneven longitudinal surface, when looking sideways it reminds a loaf of bread. The bottom and concaved part is usually with apparent or less noticeable pine bark marks. The convexed surface is variously carved – usually with grove of irregular forms that formed when the sap oozed in various directions or over gaps, hollows that remains from the pine plates, branches and other remains. Much rarely its surface is even or rippled. Sometimes in this resin carbonated bark plate remains or their imprints can be found.

Even thin plates, long flattened cylindrical trickles sometimes occur. The form of the cortical amber depends on the sap’s flow width and form, the viscosity of the sap, the speed of the flow, the surface of the trunk and other influences.

2.Cortical sap flow

Timber resin lenses were formed inside the sap vessels inside the tree trunk. When the pressure grew inside the sap vessels, the pressured sap expanded the timber tissue, damaged the sap vessel walls and the resin flowed out easily. Cortical lenses are transparent and light-colored, because the resin that forms it was under pressure and isolated from the outside environment. There are no prints on the surface or inclusions. It’s a very transparent, yellowish, without any impurities, oval, correctly shaped amber.

3.Sub-cortical sap flow

Sub-cortical sap lenses were formed under the bark when because of the pressure longitudinal and transversal vessel ruptured. The resin flowed under the bark, tore it of timber and the vessels formed there. Sub-cortical amber like the cortical one is clear and yellowish, thin (no more than 3 cm), though sub-cortical lens’ surface always has cambium fiber prints.

4. Bark amber

Bark amber is formed in the thick amber tree bark when its planks separated.

This type of amber is clear and light colored, of unique and uneven form, cut edges that were formed by the contours of the separated tree bark plates. The archetypal bark amber characteristic is bark prints on both sides: bulging on one side and on the other side concaved. Bark amber plates can be from 5 to 15 cm length, 4-7 cm wide and 0.5-3 cm thick. Organic inclusions aren’t found in them.

5. Micro-trickles – is “amber inside amber”. They’re first resin portions that flowed out and were conserved in macro-trickles – they’re also rudiments of big trickles. They’re created of thin (1-3mm thick) trickles, usually with a drop at the end, sometimes even the whole chain of such drops can be found. Micro-drops are of similar descent – clear amber drops that detached themselves from the tops of the trickles.

6. Macro-trickles – it’s clear, layered amber that formed when resin periodically oozed out of the damaged tree part. Macro-trickles – the main containers of plant and animal remains, more than 95% of all inclusions are found in them.

The trickles were hanging on think (2-8 cm diameter) branches with sap coming out of them. There are many trickles that were attached to flat surfaces such as tree trunk or base of the branch. Most common trickles are cylindrical, 20 cm long or even longer and 2-3 cm in diameter. Completely intact trickles are never found, only their fragments, as they were broken while flowing down rivers.

Amber trickles – only clear amber. The yellow color of amber is because of oxidation and is darker than inner varieties of amber. They can contain gas bubbles and their clusters that are sometimes filled with water.

7. Amber drops

Amber drops are excess resin that detached from the trickles and the sap flows of the trunk. This morphological variety of amber is the most interesting by the variety of forms and the formation processes. Two types of amber drops are distinguished – clear and unclear amber drops.

Clear amber drops are little and clear like trickles. The biggest drop found is 1.5 cm in diameter. The drops are rarely found because they were quite small and after oxidizing disintegrated in initial clusters on the forest soil. They’re deformed (mostly flattened), because the liquid drop hit the ground while dripping of the trickles.

Unclear amber drops have various morphological characteristics. It’s always cloudy, from whitish to brightly white color and formed from very viscous resin. Sometimes foam shaped amber drops are found, their color isn’t uneven and without and patterns. Average size of the unclear amber drop is 2.5-3 cm, though sometimes 5-10 cm drops can be found.