Starorusskaya Formation

Starorusskaya Formation
Stratigraphic range: Late Ediacaran PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Sub-units	See: Members
Underlies	Vasileostrovskaya Formation
Overlies	Pasha Formation
Thickness	44 - 52 m
Lithology
Primary	Argillite, sandstone, siltstone
Other	Conglomerates, clay
Location
Country	Northwest Russia

The Starorusskaya Formation is an Ediacaran fossiliferous geologic formation found in Northwestern Russia.

Members

The Starorusskaya Formation consists of 3 Members. Every member within the formation contains fossil material.

The members are as follows, listed by ascending age:

• Lower Member is characterized by clays with sandstone interbeds. There are also greenish-gray to blueish thin-bedded sandy and silty clays, which is replaced in the upper sections of the member by dense greenish-gray clays. There are also light gray quartz sandstones, ranging from fine-medium-grained to coarse-grained, and contain a mixture of gravels. It is up to 16.3 m thick, and contains the microfossils of the formation. ^[1]
• Middle Member is composed primarily of clays. This includes dark red clays with thin interbeds of light gray siltstones. Other areas contain gray, thin-bedded silty clays, containing interbeds of fine-gravel and sandstones. It is up to 22 m thick, and contains the least amount of fossils in the formation ^[1]
• Upper Member is composed of thin interbedded sandstones, siltstones and clays. The clays are predominately blueish to greenish-gray, which are finely laminated and leafy, containing dark red spots through-out. The sandstones and siltstones are greenish-gray also, with the sandstones being coarse-grained. It is up to 13.4 m thick, and contains the macrofossils of the formation. ^[1]

Paleoenvironment

From the information gathered from the lithology of the Starorusskaya Formation, its paleoenvironment was most likely a sloped environment either below the wave base or even storm wave base, and was within the photic zone, inferred from the presence of Doushantuophyton lineare , overall suggesting a prodelta environment where organisms could be buried in situ. ^[1]

Paleobiota

The Starorusskaya Formation contains a number of organisms from the Ediacaran, including unique forms such as Redkinia . ^{[1] [2]}

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon		Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

incertae sedis

Genus	Species	Notes	Images
Orbisiana [2] [1]	Orbisiana sp. O. simplex	Palaeopascichnid organism.
Redkinia [2]	R. spinosa	Rod-like fossils, possible jaw fragments of stem-arthropods.
Cucullus [2]	Cucullus sp.	Tubular organism.

Flora

Genus	Species	Notes	Images
Siphonophycus [1]	Siphonophycus sp.	Filamentous cyanobacteria.
Oscillatoriopsis [1]	Oscillatoriopsis sp.	Filamentous cyanobacteria.
Zinkovioides [1]	Zinkovioides sp.	Filamentous cyanobacteria.
Obruchevella [1]	O. parva	Filamentous cyanobacteria.
Doushantuophyton [2] [1]	D. lineare	Branching macroalgae.
Morania [2]	M. zinkovi	Filamentous cyanobacteria.
Chuaria [2]	C. circularis	Enigmatic fossil, possibly synonymous with Tawuia.
Polytrichoides(?) [2]	Polytrichoides sp.(?)	Filamentous algae.

Microorganisms

Genus	Species	Notes	Images
Leiosphaeridia [2] [1]	Leiosphaeridia sp. L. jacutica L. crassa L. minutissima L. tenuissima	Acritarch.
Tynnia [1]	T. precambrica	Acritarch.
Tuberculum (Acritarch) [1]	T. mamillatum	Acritarch.
Ceratosphaeridium [3]	Ceratosphaeridium sp.	Acritarch.
Ostiana [3]	Ostiana sp.	Acritarch.
Ceratophyton(?) [3]	Ceratophyton sp.(?)	Acritarch.

See also

• Ediacaran biota

References

1. Golubkova, E. Yu.; Bobrovskiy, I. M.; Kushim, E. A.; Plotkina, Yu. V. (September 2021). "Fossil Organisms of the Redkino Regional Stage of the Upper Vendian of the Northwestern Russian Platform (Leningrad Region)". Paleontological Journal. 55 (5): 579–587. doi:10.1134/S0031030121050051.
2. Golubkova, E. Yu.; Kushim, E. A.; Kuznetsov, A. B.; Yanovskii, A. S.; Maslov, A. V.; Shvedov, S. D.; Plotkina, Yu. V. (March 2018). "Redkinian Biota of Macroscopic Fossils from the Northwestern East European Platform (South Ladoga Region)". Doklady Earth Sciences. 479 (1): 300–304. doi:10.1134/S1028334X18030169.
3. Golubkova, E. Yu.; Kushim, E. A.; Kuzmenkova, O. F.; Laptsevich, A. G.; Plotkina, Yu. V.; Silivanov, M. O. (December 2023). "Stratigraphic Distribution of Fossil Organisms in the Upper Vendian Deposits of the Central and Southwestern Regions of the East European Platform". Paleontological Journal. 57 (S3): S211 –S236. doi:10.1134/S0031030124600124.