AbstractWenlock age turbidites in central Powys are subdivided into the mudstone rich Llanbadarn Formation and the underlying more sandy Castle Vale Formation. Sand turbidites were deposited by NNE directed flows along the base of a fault controlled basin slope dipping WNW. The resulting Castle Vale Formation thins laterally onto the slope, first onlapping it then offlapping it to be overlain diachronously by silt–mud turbidites of the Llanbadarn Formation. A finely laminated hemipelagic facies occurs between the turbidites throughout. The fine laminae are interpreted as having an annual origin. Bioturbation is entirely absent suggesting that sediment pore‐waters may have been ano