The Grey Downtonian facies occurs in the Downton Castle Sandstone Group[2] of the British Old Red Sandstone, and more or less straddles the Devonian-Silurian boundary.
[3] The Ludlow Bone Bed and Temeside Shales are sometimes also included in the Grey Downtonian, which is also referred to as the Temeside group, part of the Downton Series.
[4] It is intermediate between the marine flagstones beneath it and the terrestrial deposits above it.
[5] The beds were deposited in a marine environment, with some material being washed in from the nearby land.
[1]