Lower Ludlow Shales Group

Lower Ludlow Shales Group

Age:  423-419 million years (Silurian, Ludlow)

Overview

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 outcrop of Silurian rocks generally follows a north-south linear trend, beginning just north of the Malvern Hills and continuing along the central and eastern half of the Teme Valley, before splitting into two discrete outcrops around Abberley.

The Lower Ludlow Shales Group is part of the Mid-Late Silurian Ludlow Series, a succession represented by the Lower Ludlow Shale, the Aymestry Limestone and the Upper Ludlow Shale. The type area containing the Ludlow Anticline in northwest Herefordshire has been studied in some detail and subdivided using the rich variety of fossils. The lithologies in this area change from shallow, continental shelf in the east, to a deepening continental slope moving west.

Rocks of the Ludlow Series have been steeply folded to the west of the Malvern Hills. They occur in the May Hill uplift, the Woolhope Dome and the anticline on Shucknall Hill. They are also found in the Ludlow Anticline and in northwest Herefordshire.

Lithology

In Worcestershire, the unit tends to be described as undifferentiated Lower Ludlow Shales Group. Comprised of calcareous silty mudstones and siltstones with occasional bentonites, this fossiliferous rock forms linear outcrops in the low-lying ground west of the Wenlock Limestone ridge in Worcestershire. It also forms the SE slopes of the Abberley Hills, marking a transition from shallow water conditions of the Wenlock epoch, to the deeper waters of Ludlow times. Despite its low-lying nature, there are numerous small exposures, additional to the two largest and most important sites – Shavers End Quarry and Woodbury Quarry. The latter, being a SSSI, is designated for its excellent succession through the entire Ludlow Series.

In Herefordshire, the Lower Ludlow Shales Group tends to be divided into the Elton Formation and Lower Bringewood Formation. Both are dominated by calcareous silty mudstone and mudstone with horizons that are locally very fossiliferous. Of the two units, it is the Elton Formation that has been most extensively quarried for aggregate. At the type locality in the Mortimer Forest, the entire Elton and Lower Bringewood Formation can be seen. Click here for more information on the Elton Formation.

Sites

Shavers End Quarry, Worcestershire

Woodbury Quarry, Worcestershire

Wordell’s Farm Quarry, Herefordshire

Trippleton Lane, Herefordshire

Coneygree Wood Quarry, Herefordshire