Geological Mapping

Roderick Murchison

Eighteenth century Britain arguably witnessed the emergence of the modern science of geology with the publication of James Hutton’s seminal paper of 1785 entitled Theory of the Earth1. The first geological map of Britain was completed thirty years later in 1815 by William ‘Strata’ Smith (1769–1839) and the British Geological Survey began its comprehensive mapping of the UK and the Isle of Man as early as 1835.

Sir Roderick Impey Murchison (1792-1871) was a Scottish geologist and geographer who was the first person to investigate and describe the Silurian system. In 1831 Murchison travelled to the border of England and Wales to determine whether the rocks underlying the Old Red Sandstone could be grouped into a definite order of succession. These formations, outcropping in Wales and the west of Britain were at that time, geologically speaking, completely unknown. Following years of painstaking fieldwork, Murchison established the outlines of the Silurian system under which were grouped, for the first time, a remarkable series of formations, each with its own particular fossil record and each distinct from those of the other rocks of England1. These discoveries were articulated by Murchison in The Silurian System, first published in 1839. 

Plate 31, figure 1; Detail of Section Drawing of the Upper Silurian Rocks between Llandeilo Hill and The Blorenge Murchison, Roderick, 1839. The Silurian system, founded on geological researches in the counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester, and Stafford: with descriptions of the coalfields and overlying formations.
Plate 31, figure 1; Detail of Section Drawing of the Upper Silurian Rocks between Llandeilo Hill and The Blorenge

The geological section drawings of the Upper Silurian Rocks, drawn by Murchison himself, reveal both the strata of the underlying rock formations and the topography of the wider landscape in delightful multicoloured profiles.

Murchison, Roderick, 1839. The Silurian system, founded on geological researches in the counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester, and Stafford: with descriptions of the coalfields and overlying formations. London: J. Murray (ODS 00254)  

Plate 33, figure 4; Detail of Section Drawing of the Ludlow Rocks between Radnor Forest and Kington Murchison, Roderick, 1839. The Silurian system, founded on geological researches in the counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester, and Stafford: with descriptions of the coalfields and overlying formations
Plate 33, figure 4; Detail of Section Drawing of the Ludlow Rocks between Radnor Forest and Kington

These two images illustrate why the Mercian King Offa, in attempting to defend his territory against persistent and hostile Welsh incursions, used the terrain, rather than a Dyke, in those places where the ‘border’ ran along natural barriers; in these two examples the flanks of the Black Mountain (plate 31, figure 1) and the spine of Hergest Ridge (plate 33, figure 4) provide that natural defence. The English/Welsh border is seen to respect this ancient boundary on Camden’s map of South Wales in his 1789 edition of Britannia. 

Notes: 1. http://www.oxforddnb.com/view/article/19555?docPos=1 (accessed 03/07/2013)

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