Siberian Traps - Introduction

The Siberian Traps are the remnants of widepread volcanic activity that occurred in northern Pangea, about 250 m.y. ago. The most common rock type is basalt, which usually erupts effusively rather than explosively, but the eruptions can be prolonged, lasting for years or even decades, and producing vast flows. From comparisons with the much younger Columbia River Basalts (erupted 15 m.y. ago), single flow events ('flow fields') may have exceeded 2000 cubic km - hence the term 'flood basalts'. Flow fields in the larger provinces, such as the Deccan and Siberian Traps, may have been much larger.

Other rock types include the more coarsely crystalline equivalents of basalt (dolerite and gabbro) emplaced as intrusive sheets and stocks; and, beneath the West Siberian Basin, rare rhyolites. Unusual alkaline picrites, maymechites, occur in the Maymecha-Kotuy region NE of Noril'sk. Abundant basaltic pyroclastic rocks in the lower parts of the succession in Nizhnyaya-Tunguska indicate explosive, phreatic eruptions.

The Siberian Traps have attracted considerable study, not least around the region of the Noril'sk Ni sulfide deposit, the largest in the world, where the Traps gain their maximum known thickness. Data from other regions in Siberia are sparse, because of the difficult terrain, and because the Traps are buried beneath thick piles of sediments (e.g., beneath the West Siberian Basin).

Figure Caption: Photograph of the Pu'u 'O' fissure eruption, Hawai'i, in July 1986. This illustrates the type of eruption event that may have produced the Siberian flood basalts. However, the eruption volumes and rates would have been substantially greater in Siberia. Note the substantial gas clouds (containing sulfur dioxide, carbon dioxide, and water vapour) issuing from the vent. (Photo copyright USGS.)

Over the last two decades, interest has increased because of the possible link between the Traps and the end-Permian mass extinction. Similar 'coincidences' exist between the Deccan Traps and the end-Cretaceous extinction (at 65 Ma), and the Central Atlantic Magmatic Province and the end-Triassic extinction (at 200 Ma). To fully evaluate these links - causal or not - we need to know the full extent of the Traps and their duration, and then determine the enviromental impact of the volcanism.
A statistic: An individual basalt flow with a volume of 1500 km³ would bury the whole of the UK beneath about 6 metres of lava, or Greater London beneath about 1 km. Assuming a total volume of 3 million km³ for the Siberian Traps, this could bury the whole of western Europe beneath more than 1 km of basalt, or the whole of the UK beneath about 12 km.