Gauja Formation

The Gauja Formation is a Middle Devonian fossil locality in Estonia and Latvia.[1] It is named after the Gauja River, where it is exposed along the banks.[2]

Gauja Formation
Stratigraphic range: Middle Devonian
The Ergelu Cliffs along Gauja River, Latvia belong to the Gauja Formation
TypeGeological formation
Sub-unitsSietin Member
Lode Member
UnderliesAmata Formation
OverliesPlavinas Formation
Thickness80 m (260 ft)
Lithology
PrimarySandstone
OtherArenite, Quartz
Location
Coordinates57.30°N 25.12°E / 57.30; 25.12
Country Estonia
 Latvia
Type section
Named forGauja River

The Gauja Formation has a maximum thickness of 80 m (260 ft). It is composed of weakly to moderately cemented layers of fine-grained to very fine-grained sandstone. The layer is predominantly light to yellowish-gray in color, but can be pinkish brown or variegated. It is mostly composed of quartzose arenites. It is overlain by the 30 m (98 ft) thick Amata Formation and the Plavinas Formation.[3]

The Gauja Formation contains two cyclic members. The lower layers are known as the Sietin Member and are composed mostly of sandstone with a thin layer of siltstone at the top.[3] It has yielded numerous fossils of fishes. Among them are Asterolepis, Bothriolepis, Glyptolepis baltica, Laccognathus panderi, and Megadonichthys kurikae.[1]

The upper layers are thicker, and the lower part of it is known as the Lode Member. The Lode Member dates from the Middle Devonian and is composed of light colored sandstone. The area is indicative of a near-shore environment of retreating sea.[3] Only large plant remains and miospores are known from this member. Examples of which include Hostinella, Archaeopteris, Retusotriletes rugulatus, and Ancyrospora. Palynological studies indicate that the Middle to Upper Devonian boundary may exist in this member.[4]

See also

References
  1. "Gauja Stage". Geological collections of Estonia, Institute of Geology at TUT, University of Tartu, Estonian Museum of Natural History.
  2. "Gauja River". Tūrisma informācija īpaši aizsargājamā dabas teritorijā – Gaujas nacionālajā parkā. Archived from the original on 2012-03-26.
  3. Anne Kleesment; Väino Puura; Toivo Kallaste (2002). "Clastic dikes in Middle Devonian sandstones of the Gauja Formation, southeastern Estonia". Proceedings of the Estonian Academy of Sciences, Geology. Estonian Academy Publishers. 52 (3): 155–177.
  4. Elga Mark-Kurik; Alain Blieck; Stanislas Loboziak; Anne-Marie Candlier (1999). "Miospore Assemblage from the Lode Member (Gauja Formation) in Estonia and the Middle-Upper Devonian Boundary Problem". Proceedings of the Estonian Academy of Sciences, Geology. Estonian Academy Publishers. 48 (2): 86–97.
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