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Sylvitsa River and surrounding area, Central Urals
The sites along and near to the Sylvitsa River in the Central Urals are spread across an area of almost 200 km (Grazhdankin et al. 2007), to the northwest of the city of Yekaterinburg. The Kos’va and Koiva Rivers in the north of the Kvarkush-Kamennogorsk Meganticlinorium were the sites of the first discoveries (Bekker 1977, 1980), with fossils along the Sylvitsa River to the south discovered in the late 1980s (see history in Grazhdankin et al. 2009). More recent studies have examined numerous sections on the nearby Us’va, Chusovaya, and Mezhevaya Utka Rivers (Grazhdankin et al. 2009).
Stratigraphy, age and palaeoenvironmental interpretation
The Sylvitsa Group comprises, in order of deposition, the Staropechny Formation (with a basal diamictite), Perevalok, Chernokamen (a.k.a. Chernyi Kamen), and Ust’-Sylvitsa Formations (Ronkin et al. 2006). A Miaohe-type biota of carbonaceous macroscopic algal fossils is preserved within the Perevalok Formation (Grazhdankin et al. 2007), but the majority of the Ediacara-type fossils occur in siltstones and sandstones of the Chernokamen Formation. The units are interpreted to record a shallow-marine to fluvial environment, with repeated transgressive-regressive cycles (Grazhdankin et al. 2009). U-Pb dating of a tuff at the base of the Chernokamen Formation yields an age of 557 ± 13 Ma (Ronkin et al. 2006), while a second tuff at the base of the algae-bearing Peravalok Formation is dated at 567.2 ± 3.9 Ma (Grazhdankin et al. 2011), demonstrating a Late Ediacaran age for the biota. On the basis of litho-, bio-, and sequence stratigraphy, the Sylvitsa Group has been correlated convincingly with units found in the White Sea sections to the north (Grazhdankin et al. 2007). Up to 1600 m of stratigraphic section (Perevalok and Chernokamen Formations) is exposed (Grazhdankin et al. 2009).
Significance of the site
The Sylvitsa River site possesses a moderately diverse but abundant fossil assemblage. However, its main contribution to our understanding of late Ediacaran evolution is the co-occurrence of macroscopic algae alongside Avalon, White Sea, and Nama-type assemblages (cf. Waggoner 2003) in the same sequence. The site is thus pivotal for permitting researchers to understand the extent to which these assemblages are governed by taphonomic or sedimentological variables, rather than by biological or evolutionary factors.
Key references
Ronkin et al. 2006; Grazhdankin et al. 2007, 2009, 2011.
The sites along and near to the Sylvitsa River in the Central Urals are spread across an area of almost 200 km (Grazhdankin et al. 2007), to the northwest of the city of Yekaterinburg. The Kos’va and Koiva Rivers in the north of the Kvarkush-Kamennogorsk Meganticlinorium were the sites of the first discoveries (Bekker 1977, 1980), with fossils along the Sylvitsa River to the south discovered in the late 1980s (see history in Grazhdankin et al. 2009). More recent studies have examined numerous sections on the nearby Us’va, Chusovaya, and Mezhevaya Utka Rivers (Grazhdankin et al. 2009).
Stratigraphy, age and palaeoenvironmental interpretation
The Sylvitsa Group comprises, in order of deposition, the Staropechny Formation (with a basal diamictite), Perevalok, Chernokamen (a.k.a. Chernyi Kamen), and Ust’-Sylvitsa Formations (Ronkin et al. 2006). A Miaohe-type biota of carbonaceous macroscopic algal fossils is preserved within the Perevalok Formation (Grazhdankin et al. 2007), but the majority of the Ediacara-type fossils occur in siltstones and sandstones of the Chernokamen Formation. The units are interpreted to record a shallow-marine to fluvial environment, with repeated transgressive-regressive cycles (Grazhdankin et al. 2009). U-Pb dating of a tuff at the base of the Chernokamen Formation yields an age of 557 ± 13 Ma (Ronkin et al. 2006), while a second tuff at the base of the algae-bearing Peravalok Formation is dated at 567.2 ± 3.9 Ma (Grazhdankin et al. 2011), demonstrating a Late Ediacaran age for the biota. On the basis of litho-, bio-, and sequence stratigraphy, the Sylvitsa Group has been correlated convincingly with units found in the White Sea sections to the north (Grazhdankin et al. 2007). Up to 1600 m of stratigraphic section (Perevalok and Chernokamen Formations) is exposed (Grazhdankin et al. 2009).
Significance of the site
The Sylvitsa River site possesses a moderately diverse but abundant fossil assemblage. However, its main contribution to our understanding of late Ediacaran evolution is the co-occurrence of macroscopic algae alongside Avalon, White Sea, and Nama-type assemblages (cf. Waggoner 2003) in the same sequence. The site is thus pivotal for permitting researchers to understand the extent to which these assemblages are governed by taphonomic or sedimentological variables, rather than by biological or evolutionary factors.
Key references
Ronkin et al. 2006; Grazhdankin et al. 2007, 2009, 2011.
