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 Cowleigh Park Formation forms the lower part of the Llandovery Series May Hill Sandstone Group and crops out in the Malverns area. The Huntley Hill Formation is an equivalent unit in terms of age and characteristics but crops out in the May Hill area of southern Herefordshire.
The unit consists of buff, brown and purple, medium-coarse sandstones and conglomerates, interbedded with thin mudstones, some containing brachiopod fossils. The rocks are interpreted as having formed from flash-flood events; such episodes washed out sediment to the shallow shelf sea that was in existence.
The type section at Cowleigh Park shows an upwards succession of the unit into the overlying rocks (Wyche Formation). Exposures in disused quarries on the banks of the Leigh Brook provide the best opportunity to view this Formation, although these are now becoming very overgrown and difficult to access.
The Huntley Hill Formation is seen on May Hill Common, where it contains very coarse-grained, pebbly feldspathic quartz sandstone, whose pebbles include quartzite and pink felsite. The beds are poorly fossiliferous.
Leigh Quarry, Worcestershire (Cowleigh Park Formation)
May Hill Common Quarry, Herefordshire (Huntley Hill Formation)