| Belongs to |
Iru Subseries
|
| Type | chronostratigraphy |
| Rank | Stage |
| Scope | regional |
| Status | formal standard |
| Author | Männil in Aaloe et al. |
| Year | 1958 |
| Etymon | Varangu, vil. (E) |
| Age top (Ma) | 483.4 |
| Age base (Ma) | 486.2 |
| Age (Ma) |
Tremadocian
|
| Age reference | Cooper & Sadler, 2004 |
| Index | AIII |
| Alt. index | O1VR |
| Date changed | 2014-11-28 |
| Locality | Type | From (m)1 | To (m)2 | Reference | Remarks |
|---|---|---|---|---|---|
holostratotype
| Heinsalu, H., 1987 | Selja river bank |
Varangu Stage
H. Heinsalu & V. Viira
Original text from: Raukas, A., Teedumäe, A. (eds). 1997. Geology and Mineral Resources of Estonia. Estonian Academy Publishers, Tallinn. 436 pp. ISBN 9985-50-185-3. Available online at: sarv.gi.ee/geology.
The later Tremadoc rocks, which belong to the Varangu Stage (Männil 1990, = Ceratopyge Stage, Männil 1966, Viira et al. 1970) and have a thickness of 4-5 m extend, as a relatively narrow (20-50 km) belt in northern Estonia (Fig. 29). In the argillites, the lower boundary of the stage can be established by the appearance of graptolites of the Kiaerograptus Zone and conodonts of the Paltodus deltifer pristinus Subzone. The appearance of adelograptids marks the lower boundary of the Varangu Stage in the lithologically quite uniform Türisalu Formation. The upper part of the formation differs from the lower part, which belongs to the Pakerort Stage, by the occurrence of interbeds of very fine-grained quartzose sands from some mm up to 4-5 cm in thickness. Frequently, these interbeds abound in pyrite concretions.The Toolse area, where the Toolse Member was defined, has been studied in particular detail (Kivimägi & Loog 1972, Heinsalu 1980).
Varangu Formation
The Varangu Formation, the youngest part of the Tremadoc, is widely distributed in northwestern Estonia (Fig. 29). It is at its thickest (ca 3 m) between Haljala and Kunda in northeastern Estonia where the Varangu Formation can be subdivided into three lithologically different parts. The lower and upper parts are predominantly clayey, consisting mostly of compact claystone which comprises glauconite and pyrite, scattered or concentrated in small lenses. The middle part is rich in glauconite and very fine-grained quartz, sometimes prevailing over pelitic material. The sand is hardly pyritized. A similar three-part sequence of the Varangu Formation occurs also on the Pakri Cape in northwestern Estonia, but its thickness there is only 0.3-0.4 m.
In most of western Estonia, the Varangu Formation is characterized by the greenish-grey compact silty clay or sandy deposits with glauconite grains. In some sequences the clays of the Varangu Formation are dark in colour which makes them similar to the Dictyonema shale.
