The Wentnor Group is an assemblage of two rock formations associated with the Longmyndian Supergroup of Precambrian age in present-day Wales, U.K.
At the base of the Stretton Group the rocks are of basinal oceanic facies and over time a coarsening occurs with increased terrigenous input from the continent.
Turbidites are observed and deltas form latterly with alluvial plains with occasional marine washovers.
Thick cross-bedded sandstones are recorded with sharp erosional bases and are interpreted as fluvial channels running upon mud rich alluvial plain deposits.
There are interbeds of cross-laminated finer grained sandstones with apparent upward fining successions.