| Bezys and Risk suggested that the black shales and mudstone facies were the results of a stratified water column with a pycnocline. |
| The pycnocline is a very stable layer that acts as a barrier to the transfer of water and energy between the surface and subsurface layers. |
| In tropical areas there is usually a well-mixed layer of uniform density close to the surface above the pycnocline, a layer in which density increases extremely rapidly. |
| Internal waves occur in the ocean at the base of the pycnocline, especially at the bottom edge of a steep thermocline. |
| These waves occur in the ocean's interior and propagate horizontally, concentrating their energy around the oceanic pycnocline. |
| Below the pycnocline density continues to increase but much more slowly. |
