The Gauja Formation is a

Middle Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...

fossil locality This list of fossil sites is a worldwide list of localities known well for the presence of fossils. Some entries in this list are notable for a single, unique find, while others are notable for the large number of fossils found there. Many of t ...

Estonia Estonia, formally the Republic of Estonia, is a country by the Baltic Sea in Northern Europe. It is bordered to the north by the Gulf of Finland across from Finland, to the west by the sea across from Sweden, to the south by Latvia, and t ...

and

Latvia Latvia ( or ; lv, Latvija ; ltg, Latveja; liv, Leţmō), officially the Republic of Latvia ( lv, Latvijas Republika, links=no, ltg, Latvejas Republika, links=no, liv, Leţmō Vabāmō, links=no), is a country in the Baltic region of ...

. It is named after the Gauja River, where it is exposed along the banks.

Description

The Gauja Formation has a maximum thickness of . It is composed of weakly to moderately cemented layers of fine-grained to very fine-grained

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

. 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 thick

Amata Formation According to Roman mythology, Amata (also called Palanto) was the wife of Latinus, king of the Latins, and the mother of their only child, Lavinia. In the Aeneid of Virgil, she commits suicide during the conflict between Aeneas and Turnus o ...

and the Plavinas Formation. 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 Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

at the top. It has yielded numerous fossils of fishes. Among them are '' Asterolepis'', '' Bothriolepis'', ''

Glyptolepis baltica ''Glyptolepis baltica'' is an extinct species of lobe-finned fishes belonging to the family Holoptychiidae Holoptychiidae is an extinct family of lobe-finned fishes which lived during the Devonian period. At least one genus, ''Laccognathus'' ...

'', ''

Laccognathus panderi ''Laccognathus panderi'' is an extinct lobe-finned fish from northern Europe. They existed from the Middle Devonian to the Late Devonian (around 397.5 to 360 mya). ''L. panderi'' has been recovered from the Middle Devonian Gauja Formation an ...

'', '' Livoniana multidentata'',Ahlberg et al., 2000 and ''

Megadonichthys kurikae ''Megadonichthys kurikae'' is an extinct species of fish belonging to the family Osteolepididae Osteolepididae is an family of primitive, fish-like tetrapodomorphs (the clade that contains modern tetrapods and their extinct relatives) that l ...

''. 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. Only large plant remains and

miospore Cryptospores are fossilised primitive plant spores that first appear in the fossil record during the middle of the Ordovician period. Evidence that cryptospores derive from land plants Occurrence Cryptospores are generally found in non-marine roc ...

s are known from this member. Examples of which include '' Hostinella'', ''

Archaeopteris ''Archaeopteris'' is an extinct genus of progymnosperm tree with fern-like leaves. A useful index fossil, this tree is found in strata dating from the Upper Devonian to Lower Carboniferous (), the oldest fossils being 385 million years old, a ...

'', '' Retusotriletes rugulatus'', and ''

Ancyrospora ''Ancyrospora'' is a fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animal ...

''. Palynological studies indicate that the Middle to Upper Devonian boundary may exist in this member.

References

Bibliography

* {{cite LSA , first=P.E. , last=Ahlberg , first2=E. , last2=Lukševis , first3=E. , last3=Mark-Kurik , year=2000 , title=A near-tetrapod from the Baltic Middle Devonian , journal=

Palaeontology Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...

, volume=43 , pages=533–548 Geologic formations of Europe Geology of Estonia Geology of Latvia Devonian System of Europe Givetian Stage Sandstone formations Shallow marine deposits Devonian southern paleotropical deposits Fossiliferous stratigraphic units of Europe Paleontology in Estonia Paleontology in Latvia

Description

See also

References

Bibliography