Elton Formation - Earth Heritage Trust

Elton Formation, Lower Ludlow Shales

Age: 423-421 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.

In Worcestershire 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 outcrops around Abberley.

The Elton Formation falls within the Mid-Silurian Ludlow Series; a succession represented by the Lower Ludlow Shale (containing the Elton Formation), 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 lithological environments 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 in northwest Herefordshire, where the entire Elton Formation can be seen in Mortimer Forest.

Lithology

The Elton Formation comprises silty mudstones and siltstones, which are generally calcareous. Some horizons are highly fossiliferous, with assemblages dominated by brachiopods with trilobites, solitary corals and cephalopods commonly occurring. Broken shell debris is also present. The parent unit, the Lower Ludlow Shales, generally occurs in poorly exposed low lying land between the ridges of the Much Wenlock and Aymestry Limestones.

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