Orsten
Encyclopedia
The Upper Cambrian Orsten fauna includes fossilized organisms preserved in Orsten lagerstätte
n, notably at Kinnekulle
and on the island of Öland
, all in Sweden
.
The initial site, discovered in 1975 by Klaus Müller and his assistants, exceptionally preserves soft-bodied organisms, and their larva
e, who are preserved uncompacted in three dimensions. The fossil
s are phosphatized
and silicified
, thus the delicate chitin
ous cuticle and soft parts are not affected by acids, which act upon the limestone nodule
s within which the fossils have survived. Acids dissolve the limestone, revealing the microfossils in a recovery process called "acid etching". To recover the fossils, more than one and a half tons of Orsten limestone have been dissolved in acid, originally in a specifically designed laboratory in Bonn
, more recently moved to Ulm
. The insoluble residue is scanned by electron microscope
.
The Orsten fauna has improved our understanding of metazoan phylogeny and evolution, particularly among the arthropod
s, thanks in part to unique preservation of larval stages. The Orsten sites reveals the oldest well-documented benthic meiofauna in the fossil record. For the first time, fossils have been found of tardigrade
s ("water bears") and apparently free-living pentastomids.
The Cambrian stratum consists of alum
shale
s with limestone nodules, which are interpreted as the products of an oxygen-depleted ("dysoxic") marine bottom water habitat of a possibly offshore seashelf at depths of perhaps 50–100 mThe bottom was rich in organic detritus, forming a soft muddy zone with floc
in its surface layer.
Further Orsten fauna have been found by Dieter Waloszek in the outback of the Northern Territory
of Australia.
Lagerstätte
A Lagerstätte is a sedimentary deposit that exhibits extraordinary fossil richness or completeness.Palaeontologists distinguish two kinds....
n, notably at Kinnekulle
Kinnekulle
- External links :* *...
and on the island of Öland
Öland
' is the second largest Swedish island and the smallest of the traditional provinces of Sweden. Öland has an area of 1,342 km² and is located in the Baltic Sea just off the coast of Småland. The island has 25,000 inhabitants, but during Swedish Midsummer it is visited by up to 500,000 people...
, all in 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....
.
The initial site, discovered in 1975 by Klaus Müller and his assistants, exceptionally preserves soft-bodied organisms, and their larva
Larva
A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...
e, who are preserved uncompacted in three dimensions. The fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s are phosphatized
Phosphate
A phosphate, an inorganic chemical, is a salt of phosphoric acid. In organic chemistry, a phosphate, or organophosphate, is an ester of phosphoric acid. Organic phosphates are important in biochemistry and biogeochemistry or ecology. Inorganic phosphates are mined to obtain phosphorus for use in...
and silicified
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
, thus the delicate chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
ous cuticle and soft parts are not affected by acids, which act upon the limestone nodule
Nodule (geology)
A nodule in petrology or mineralogy is a secondary structure, generally spherical or irregularly rounded in shape. Nodules are typically solid replacement bodies of chert or iron oxides formed during diagenesis of a sedimentary rock...
s within which the fossils have survived. Acids dissolve the limestone, revealing the microfossils in a recovery process called "acid etching". To recover the fossils, more than one and a half tons of Orsten limestone have been dissolved in acid, originally in a specifically designed laboratory in Bonn
Bonn
Bonn is the 19th largest city in Germany. Located in the Cologne/Bonn Region, about 25 kilometres south of Cologne on the river Rhine in the State of North Rhine-Westphalia, it was the capital of West Germany from 1949 to 1990 and the official seat of government of united Germany from 1990 to 1999....
, more recently moved to Ulm
Ulm
Ulm is a city in the federal German state of Baden-Württemberg, situated on the River Danube. The city, whose population is estimated at 120,000 , forms an urban district of its own and is the administrative seat of the Alb-Donau district. Ulm, founded around 850, is rich in history and...
. The insoluble residue is scanned by electron microscope
Electron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
.
The Orsten fauna has improved our understanding of metazoan phylogeny and evolution, particularly among the arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...
s, thanks in part to unique preservation of larval stages. The Orsten sites reveals the oldest well-documented benthic meiofauna in the fossil record. For the first time, fossils have been found of tardigrade
Tardigrade
Tardigrades form the phylum Tardigrada, part of the superphylum Ecdysozoa. They are microscopic, water-dwelling, segmented animals with eight legs. Tardigrades were first described by Johann August Ephraim Goeze in 1773...
s ("water bears") and apparently free-living pentastomids.
The Cambrian stratum consists of alum
Alum
Alum is both a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated potassium aluminium sulfate with the formula KAl2.12H2O. The wider class of compounds known as alums have the related empirical formula, AB2.12H2O.-Chemical properties:Alums are...
shale
Shale
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...
s with limestone nodules, which are interpreted as the products of an oxygen-depleted ("dysoxic") marine bottom water habitat of a possibly offshore seashelf at depths of perhaps 50–100 mThe bottom was rich in organic detritus, forming a soft muddy zone with floc
Floc
Floc can refer to either:* FLOC is the abbreviation for the Farm Labor Organizing Committee, a labor unionor* Floc is flake of precipitate that comes out of solution during the process of flocculation...
in its surface layer.
Further Orsten fauna have been found by Dieter Waloszek in the outback of the Northern Territory
Northern Territory
The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...
of Australia.