May Hill Sandstone Group
Age: 444-428 million years (Silurian, Llandovery)
Silurian rocks in Herefordshire and Worcestershire are used as markers for this period of earth history throughout the world. They mark a time when the world’s great oceans were in the process of closing, leading to the formation of marine sandstones, mudstones and limestones. The rocks are also famous for their diversity and richness of fossils, and this has led to accurate sub-divisions of the period being devised: the Llandovery (443-428Ma), Wenlock (428-423Ma), Ludlow (423-419Ma) and the Pridoli (419-416Ma). All four of these time frames are represented in the two counties.
The boundary with the underlying Precambrian (Malverns Complex) rocks is tectonic in many places, but an unconformity can be seen in places, where a basal conglomerate (Miss Phillips Conglomerate) is developed. This was formed on the shore of a rocky coastline. Recently following re-excavation of the boundary, the succeeding shale layer has been recorded as being sheared, showing that both an unconformity and faulting are features of the contact between the Malverns Complex and Silurian rocks.
The May Hill Sandstone has been divided in the Malvern area into the Cowleigh Park Formation and the overlying Wyche Formation. In the May Hill area it is divided into the Huntley Hill Formation and Yartleton Formation respectively. In the Woolhope Dome the sandstone-dominated Lower Haugh Wood Beds and the mudstone-dominated Upper Haugh Wood Beds (collectively the Haugh Wood Formation) have been mapped. In the Fownhope Borehole below the Haugh Wood Formation occur the Huntley Hill Formation and the Fownhope Formation, which is nowhere exposed at the surface. These last two Formations have not been quarried for aggregate.
Further information on these units can be found by clicking on the following links: