80 | Great Geologists
Ben Peach (right) and John Horne (left) outside the Inchnadamph Hotel whilst leading a field
excursion in 1912.
John Macculloch, who first described the geology of the region,
considered this a standard younging-upwards stratigraphic
succession. This idea was adopted by the titan of mid-19th
century geology, Sir Roderick Murchison, the ‘King of Siluria,’
with the Moine Schists being regarded as Silurian. The
uppermost (Durness) limestones, beneath the Moine Schists,
contained fossils that indicated a ‘lower Silurian’ age (Ordovician
in the current sense) (the first fossils had been found by Ben
Peach’s father). Above the Moine Schists lay Devonian Old Red
Sandstones. Murchison, therefore, reasoned that despite their
metamorphosed state and the unmetamorphosed state of the
sediments below them, the Moine Schists must be part of his
beloved Silurian system.
The idea that the geology of the North-West Highlands was so
simple sat ill with a number of geologists working in the region.
The first was James Nicol, Professor of Geology at Aberdeen
University, who had accompanied Murchison on one of his visits
to the region. He gathered evidence showing multiple repetitions
of the strata, and that the contact between the Moine Schists
and the underlying rocks was tectonic in origin. Unfortunately,
the prestige of Murchison, supported by his protégé, Archibald
Geikie, the first Director of the Scottish Geological Survey, meant
that Nicol’s views were largely ignored.
Nonetheless, the doubts continued to amass. In 1883, Charles
Lapworth, Professor at Birmingham University, who had
recognised imbrication in the southern Uplands of Scotland
by means of biostratigraphic control using graptolites, was
advocating that the Moine Schists were tectonically emplaced
over the underlying sediment. He noted the mylonites at the fault
boundary, evidence for deformation by lateral translation of the
overlying thrust sheet. By this time, Murchison had passed away
and Geikie could hardly ignore the evidence that was gathering.
Accordingly, he assembled a team led by two of his best
geologists — Peach and Horne — to map the area and provide
the definitive evidence.
Benjamin Peach was born in Gorran Haven, Cornwall in 1842.
His father, Charles, was an amateur naturalist and geologist.