Sirius Passet is a

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

Lagerstätte A Fossil-Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that preserves an exceptionally high amount of palaeontological information. ''Konzentrat-Lagerstätten'' preserv ...

Peary Land Peary Land is a peninsula in northern Greenland, extending into the Arctic Ocean. It reaches from Victoria Fjord in the west to Independence Fjord in the south and southeast, and to the Arctic Ocean in the north, with Cape Morris Jesup, the nor ...

Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland. It comprises six places in

Nansen Land Nansen Land is a peninsula in far northwestern Greenland. It is a part of the Northeast Greenland National Park. The Arctic wolf is present in the peninsula. The northern shore facing the Lincoln sea slopes evenly and is fertile for the area, be ...

, on the east shore of J.P. Koch Fjord in the far north of Greenland. It was discovered in 1984 by A. Higgins of the Geological Survey of Greenland. A preliminary account was published by

Simon Conway Morris Simon Conway Morris (born 1951) is an English palaeontologist, evolutionary biologist, and astrobiologist known for his study of the fossils of the Burgess Shale and the Cambrian explosion. The results of these discoveries were celebrated ...

and others in 1987 and expeditions led by J. S. Peel and Conway Morris have returned to the site several times between 1989 and the present. A field collection of perhaps 10,000 fossil specimens has been amassed. It is a part of the

Buen Formation The Buen Formation is a Formation (geology), geologic formation and Lagerstätte in Peary Land, North Greenland. The shale preserves fossils dating back to the Early Cambrian Period (geology), period (Atdabanian in the local timescale, about 520 ...

Age

The fauna is inevitably compared to that of the

Burgess Shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest fos ...

, although it is probably ten to fifteen million years older – vs. ) – and more closely contemporaneous with the fauna of the

Maotianshan shales The Maotianshan Shales () are a series of Early Cambrian sedimentary deposits in the Chiungchussu Formation or Heilinpu Formation, famous for their '' Konservat Lagerstätten'', deposits known for the exceptional preservation of fossilized orga ...

from Chengjiang, which are dated to .

Preservation

The preservation of the Sirius Passet is traditionally considered to represent

silicification In geology, silicification is a process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO2). Silica is a naturally existing and abundant com ...

associated with a

death mask A death mask is a likeness (typically in wax or plaster cast) of a person's face after their death, usually made by taking a cast or impression from the corpse. Death masks may be mementos of the dead or be used for creation of portraits. The m ...

, recalling the 'Ediacara-type' preservation of the Precambrian

Ediacara biota The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were enigmatic tubular and frond-shaped, mostly sessile, organis ...

. A 2022 study suggested that the original preservation mode was phosphatisation that was later altered by low-grade

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

with a peak temperature of during the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Ellesmerian orogeny, which resulted in widespread mineral replacement. Geochemical analysis indicates that the fossils lived close to the boundary of an oxygen minimum zone, possibly being preserved in oxygen-starved periods.

IUGS geological heritage site

In respect of the importance of the exceptionally preserved fossils in our understanding of the event, the 'Cambrian Explosion in Sirius Passet' was included by the

International Union of Geological Sciences The International Union of Geological Sciences (IUGS) is an international non-governmental organization devoted to global cooperation in the field of geology. As of 2023, it represents more than 1 million geoscientists around the world. About Fo ...

(IUGS) in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an 'IUGS Geological Heritage Site' as 'a key place with geological elements and/or processes of international scientific relevance, used as a reference, and/or with a substantial contribution to the development of geological sciences through history.'

Fauna

Although the fauna has not yet been fully described, it is known to consist of a moderate number of arthropods and sponges, and rare representatives of other groups. It has yielded the problematic taxon '' Halkieria'', and the Panarthropods ''

Kerygmachela ''Kerygmachela kierkegaardi'' is a Kerygmachelidae, kerygmachelid Lobopodia#Gilled lobopodians, gilled lobopodian from the Cambrian Stage 3 aged Sirius Passet Lagerstätte in northern Greenland. Its anatomy strongly suggests that it, along with i ...

'' and ''

Pambdelurion ''Pambdelurion'' is an extinct genus of Panarthropoda, panarthropod from the Cambrian aged Sirius Passet site in northern Greenland. Like the morphologically similar ''Kerygmachela'' from the same locality, ''Pambdelurion'' is thought to be closel ...

'', all of which have played prominent roles in discussions about the origins of the modern animal phyla.

Taxa from the Sirius Passet fauna

After

Arthropods

Other animals

References

External links

Palaeos.com: Cambrian ''Sirius Passet''
{{Burgess shale type preservation Geologic formations of Greenland Cambrian Greenland Cambrian paleontological sites Paleontology in Greenland Lagerstätten * Peary Land First 100 IUGS Geological Heritage Sites

Age