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What is Amber?

Amber is the fossilized resin from ancient forests. Amber is not produced from tree sap, but rather from plant resin. This aromatic resin can drip from and ooze down trees, as well as fill internal fissures, trapping debris such as seeds, leaves, feathers and insects. The resin becomes buried and fossilized through a natural polymerization of the original organic compounds.

How is amber formed?            Why is resin produced?

What is amber's botanical affinity?            When was Kansas amber produced?

What type of depositional environment preserved amber?

How is amber formed?

Amber is a fossilized resin, not tree sap. Sap is the fluid that circulates through a plant's vascular system, while resin is the semi-solid amorphous organic substance secreted in pockets and canals through epithelial cells of the plant. Land plant resins are complex mixtures of mono-, sesqui-, di-, and triterpenoids, which have structures based on linked isoprene C5H8 units (Langenheim, 1969, p. 1157). Volatile terpenoid fractions in resins evaporate and dissipate under natural forest conditions, leaving nonvolatile terpenoid fractions to become fossilized if they are stable enough to withstand degradation and depositional conditions. The fossil resin becomes incorporated into sediments and soils, which over millions of years change into rock such as shale and sandstone.

Therefore, amber is formed as a result of the fossilization of resin that that takes millions of years and involves a progressive oxidation and polymerization of the original organic compounds, oxygenated hydrocarbons. Although a specific time interval has not been established for this process, the majority of amber is found within Cretaceous and Tertiary sedimentary rocks(approximately 30-90 million years old).

Why is resin produced?

Although there are contrasting views as to why resin is produced, it is a plant's protection mechanism. The resin may be produced to protect the tree from disease and injury inflicted by insects and fungi. Resin may be exuded to heal a wound such as a broken branch, and resins possess odors or tastes that both attract and repel insects (Langenheim, 1969, p. 1167). In mature trees, resin may simply exude from vertical fissures in the bark due to tension produced by rapid growth (Langenheim, 1969, p. 1166). Resin may also be produced as a plant's method for disposing of excess acetate.

What is amber's botanical affinity?

There is no one tree responsible for the resin that fossilizes into amber. Botanical affinities have been suggested based on examination of the entombed debris and through chemical studies of the resin. The botanical affinity of jelinite, Kansas amber, appears to be from the Araucariaceae family, which is considered to be a primary Mesozoic amber tree. Although this tree does not exist today in the northern hemisphere, it would closely resemble Agathis australis, or the huge Kauri pine found today in New Zealand.

During most of the Mesozoic geologic time period, gymnosperms dominated land vegetation. Conifers are the most successful gymnosperm living today (Cleal & Thomas, 1999, p. 62). Some of the amber land plants were probably conifers from the order Pinales, in the families: Araucariaceae (e.g., Norfolk Pine, Monkey Puzzle, Kauri Pine), Taxodiaceae (e.g., sequoias and bald cypresses), Taxaceae (e.g., yews), Pinaceae (e.g., pine and larches), Cupressaceae (e.g., cedars, cypresses, junipers), and Podocarpaceae.

Studies by Göppert (1836), based on botanical debris entombed in amber, concluded that members of the Pinaceae were the source of Baltic amber. Specifically, Göppert (1836) designated the amber tree as Pinites succinifer, although he clearly stated this wood anatomy was not the same as any living pine today. Disregarding botanical evidence and concentrating on chemical evidence, Beck (1999) and Larsson (1978) suggested sources other than Pinaceae for Baltic amber, including Araucariaceae, Cupressaceae, and Taxodiaceae; they believed that chemically Göppert's Pinites was a closer match to the Araucariaceae than to Pinaceae.

When was Kansas amber produced?

Kansas amber was found among Cretaceous age rock, which is in the Mesozoic Era. Fossil resin and copal occur on the North American continent among strata from Triassic to Recent. The oldest amber is found in the Upper Triassic Chinle Formation, New Mexico (Grimaldi, Nascimbene, Luzzi, Case, 1998, p. 81). The next oldest deposits of amber are Cretaceous in age. The most abundant North American Cretaceous fossil resins are from the states of Alaska and New Jersey, USA and from the provinces of Alberta and Manitoba, Canada.

What type of depositional environment preserved amber?

One depositional environment for amber is marginal marine. Amber's specific gravity is slightly over 1 and it floats in saltwater; therefore amber becomes concentrated in estuarine or marine deposits, moved some distance from the original site (Langenheim, 1969, p. 1159). Trees and resin may be transported and deposited in quiet water sediments that formed the bottom of a lagoon or delta at the margin of a sea. Wood and resin are buried under the sediment and while the resin becomes amber, the wood becomes lignite. Wet sediments of clay and sand preserve the resin well because they are devoid of oxygen.

Therefore, given copious resin producing trees and appropriate burial conditions, amber is preserved in sedimentary clay, shale, and sandstones associated with layers of lignite, a woody brown coal. A generalized interpretation of the depositional conditions present in Kansas amber-bearing strata is that a transgressing or advancing Cretaceous sea in north-central Kansas led to deposition and preservation of fluvial, estuarine, and lagoon or bay deposits behind a barrier island system (Franks, 1980, p. 56).

For more information:

  • An excellent overview of Baltic amber (authored by B. Kosmowska-Ceranowicz, K. Leciejewicz, K. Kwiatkowska, and A. Pieliñska) can be found at http://www.hermuz.hu/engweb/nws/amber2.htm
  • Andzia's Amber Reading Room has many interesting articles to choose from, http://www.amberjewelry.com/Amber_Reading_Room_p1.htm and Amber Myths and History at http://www.amberjewelry.com/amber_myths_and_history_p1.htm
  • Quick Amber Facts at Dragonfly Amber.com, http://www.dragonflyamber.com/choosing_amber/amber_quick_facts.html.
  • Amber: the Jurassic Gem.
  • Amber by Martin Rees

    References

  • Langenheim, J. H. (1969). Amber-a botanical inquiry. Science 163(3): 1157-1169.
  • Cleal, C. J., and Thomas, B. A. (1999). Plant fossils the history of land vegetation. Woodbridge, Suffolk, UK: The Boydell Ress.
  • Göppert, H. R. (1836). Fossile Pflanzenreste des Eisensandes von Aachen. Nova Acta Academiae C. L. C. Nat., Curiosum, 19: 150.
  • Beck, C. W. (1999). The Chemistry of Amber. Estudios del Museo de Ciencias Naturales de Alava 14 (2): 33-4873-117. Spain.
  • Grimaldi, D., Nascimbene, P., Luzzi, K., and Case, G. (1998). North American ambers and an exceptionally diverse deposit from the Cretaceous of New Jersey, USA. World Congress on Amber Inclusions. Museo de Ciencias Naturales de Alava, Abstracts: Spain, p. 81.
  • Franks, P. C. 1980. Models of marine transgression-example from Lower Cretaceous fluvial and paralic deposits, north-central Kansas. Geology 8(1): 56-61.
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