Silurian deposition in East Siberia and the absence of large-scale eustatic fluctuations
Silurian deposition in East Siberia and the absence of large-scale eustatic fluctuations
Russian Geology and Geophysics (October 2002) 43 (10): 839-862
- Aeronian
- Asia
- biostratigraphy
- boreholes
- coastal environment
- Commonwealth of Independent States
- depositional environment
- Devonian
- epicontinental seas
- eustasy
- intertidal environment
- Irkutsk Russian Federation
- Lena Basin
- Llandovery
- Lower Devonian
- Lower Silurian
- numerical models
- outcrops
- paleobathymetry
- paleogeography
- Paleozoic
- Pridoli
- regression
- Rhuddanian
- Russian Federation
- sea-level changes
- sedimentary rocks
- shallow-water environment
- Siberian Platform
- Silurian
- stratigraphic gaps
- subsidence
- Telychian
- Tunguska
- Upper Silurian
- Vilyuy River basin
- Wenlock
- Yakutia Russian Federation
- Yenisei Basin
- Moyero River basin
- Morkoka River basin
- Ilim River basin
- Nyuya River basin
The concept of time-dependent eustatic fluctuations has been largely recognized, and a number of eustatic events with magnitudes from 20 to 100 m and durations 1 to 3 m. y. (third-order cycles) have been suggested for the Phanerozoic. Eight cycles were distinguished in the Silurian on the basis of sea depth variations in different regions. East Siberia in Silurian time was occupied by a large sea, and its bottom fill has been well documented in many sections. Slow continuous deposition for 10 to 20 m. y. in peritidal environments (< or =10 m) recorded in some Silurian sections rules out large-scale eustatic events. The magnitude of the Silurian events could not exceed approximately 10-20 m, as follows from analysis of eustatic fluctuations and sedimentation rates in the sections. The absence of large-scale eustatic events in the Cambrian and earliest Ordovician inferred in an earlier study in the East Baltic regions, along with the results from the Silurian sections of Siberia, casts doubt on the existence of rapid large-scale eustatic fluctuations over the greatest part of the Phanerozoic. Considerable sea-depth changes that occurred in Cambrian and Silurian deposition basins at a relatively stable water level are rather of tectonic origin. Rapid crustal uplift and subsidence on the background of slow deepening of the basins is a specific type of tectonic movements on platforms.