Buen Formation

The Buen Formation is a geologic formation and Lagerstätte in Peary Land, North Greenland. The shale preserves fossils dating back to the Early Cambrian period (Atdabanian in the local timescale, about 520 to 513 Ma).^[1]

Buen Formation
Stratigraphic range: Cambrian Series 2 (Atdabanian) ~520–513 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Unit of	Sirius Passet
Sub-units	Upper & lower members
Underlies	Hans Tavsen icecap
Overlies	Portfjeld Formation
Thickness	Up to 700 m (2,300 ft)
Lithology
Primary	Mudstone
Other	Sandstone, shale
Location
Coordinates	83.1°N 33.8°W / 83.1; -33.8
Approximate paleocoordinates	22.1°S 49.0°W / -22.1; -49.0
Region	Peary Land
Country	Greenland
Extent	Franklinian Basin
Type section
Location	Southern Peary Land
Buen Formation (Greenland)

Description

Geologic map of Sirius Passet with the Buen Formation shown in black

The oldest Cambrian series of the area was deposited in the Franklinian Basin and is poorly exposed in fragmentary, heavily metamorphosed outcrops in Peary Land. It was emplaced during the Ellesmerian orogeny.^[2][3]

Paleogeography

Cambrian paleogeography with the Buen Formation in orange

During the Cambrian, Greenland was located in the southern tropical to temperate region. The Buen Formation forms part of the southern shelf succession of the Franklinian Basin of North Greenland and the Canadian Arctic Islands. The formation, approximately 325 metres (1,066 ft) thick, consists of a lower, sand−dominated, member overlain by an upper member dominated by dark grey−green mudstones and siltstones in its type area in southern Peary Land. It thickens to around 700 metres (2,300 ft) in northern Peary Land where it comprises a mud−rich transitional succession into deep water trough deposits of the Polkorridoren Group. Dark grey to black mudstones form part of this transitional succession from the shelf to the slope. To the south they lie in faulted contact with pale dolomites of the underlying Portfjeld Formation, and to the north with bioturbated mudstones and sandstones of the Buen Formation.^[4]

Fossil content

The following fossils have been reported from the formation:^[1]

Fossils from the Buen Formation, Sirius Passet, Greenland

Group	Taxon	Image	Notes
Annelids	Phragmochaeta canicularis		[5]
Arthropods	Buenaspis forteyi		[6]
	Buenellus		[1]
	Aaveqaspis
	Kerygmachela
	Tamisiocaris
	Limniphacos
	Waptia
	Kleptothule rasmusseni		[6]
	Isoxys volucris
	Hadranax augustus
	Pauloterminus spinodorsalis
Molluscs	Halkieria evangelista
Demosponges	Choia hindei
Others	Heliosphaeridium dissimilare
	Trapezovitus malinkyi		[1]
	Kalaallitia myliuserichseni
	Nasaaraqia hyptiotheciformis
	Nevadotheca boerglumensis
	Sullulika broenlundi
	Alutella siku		[7]

See also

• List of fossiliferous stratigraphic units in Greenland
• Sirius Passet