The Diabasbrottet quarry (58°21′32.2"N 12°30′08.6"E), located on Mt. Hunneberg

Hunneberg

Hunneberg is a Swedish mountain just east of Vänersborg and Trollhättan....

, Västergötland

Västergötland

', English exonym: West Gothland, is one of the 25 traditional non-administrative provinces of Sweden , situated in the southwest of Sweden. In older English literature one may also encounter the Latinized version Westrogothia....

, 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....

, is the location of the Global Boundary Stratotype Section and Point

Global Boundary Stratotype Section and Point

A Global Boundary Stratotype Section and Point, abbreviated GSSP, is an internationally agreed upon stratigraphic section which serves as the reference section for a particular boundary on the geologic time scale. The effort to define GSSPs is conducted by the International Commission on...

 (GSSP) which marks the boundary between the Floian and Tremadocian stages of the Early Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

. It was selected over "The Ledge" in western Newfoundland

Newfoundland and Labrador

Newfoundland and Labrador is the easternmost province of Canada. Situated in the country's Atlantic region, it incorporates the island of Newfoundland and mainland Labrador with a combined area of . As of April 2011, the province's estimated population is 508,400...

 in 2000 and ratified as the GSSP by the International Union of Geological Sciences

International Union of Geological Sciences

The International Union of Geological Sciences is an international non-governmental organization devoted to international cooperation in the field of geology.-About:...

 in 2002.

The first appearance

First appearance datum

First appearance datum is a term used by geologists and paleontologists to designate the first appearance of a species in the geologic record. In other words, FADs represent the geologically oldest fossil of a particular species that has yet been discovered.FADs are frequently used to designate...

 of Tetragraptus approximatus, a graptolite

Graptolite

Graptolithina is a class in the animal phylum Hemichordata, the members of which are known as Graptolites. Graptolites are fossil colonial animals known chiefly from the Upper Cambrian through the Lower Carboniferous...

, defines the boundary. The rock section, dominated by 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...

, is unusually fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

iferous, including fossilized remains of graptolites, conodont

Conodont

Conodonts are extinct chordates resembling eels, classified in the class Conodonta. For many years, they were known only from tooth-like microfossils now called conodont elements, found in isolation. Knowledge about soft tissues remains relatively sparse to this day...

s, and trilobite

Trilobite

Trilobites are a well-known fossil group of extinct marine arthropods that form the class Trilobita. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period , and they flourished throughout the lower Paleozoic era before...

s. It is highly compressed, and the Ordovician section is only 12 m thick.