Figure 2.

Outcrop examples of large sills in Siberia. (a) Overview of a lower Tunguska river section outcrop with sills and sediment highlighted. (b) At least four thick sills are clearly visible as steps in the outcrop (many smaller sills can be found on closer inspection within the sediments). (c) The contact of the sills with organic-rich sediments (coal) reveal metamorphic aureoles due to baking from the sill intrusions, a process which liberates gases from the host rocks. (Online version in colour.)