lanarkshire-1978/03_033

Transcription

INTRODUCTION
to the Inventory of the Prehistoric and
Roman Monuments of Lanarkshire

PART 1. GENERAL

TOPOGRAPHY AND GEOLOGY

To a greater extent than most Scottish counties Lanarkshire is a geographical unit,
occupying the upper and middle basin of the River Clyde. Except for the Biggar Water,
which flows eastwards through the Biggar Gap into the Tweed, and the Rivers Almond
and Avon, which discharge into the Forth, the county is drained solely by the Clyde and its
tributaries, a fact which accounts for its alternative name 'Clydesdale'. As Fig. 1 shows, it
measures 80 km in length from north-west to south-east by a maximum of 33 km transversely,
and is more or less symmetrical in shape - progressively widening downstream from the head-
waters of the Clyde as the basin of the river broadens, and then contracting again towards
the north-western extremity. Lanarkshire, with roughly its present bounds, was established
as a sheriffdom in 1402, when the sheriffdom of Lanark was divided into those of Lanark
and Renfrew. Until the middle of the 18th century it comprised two wards, the Upper Ward
(the Upper Clyde valley) and the Lower Ward, but in consequence of the rapid growth of the
population during the Industrial Revolution the Lower Ward was subsequently subdivided
into the Middle and Lower Wards.
The topography of the county is largely determined by the underlying geology, and falls
broadly into two parts separated by the Southern Upland Fault, which runs south-westwards
from Biggar to beyond Crawfordjohn. To the south of the fault-line the rocks consist mainly
of marine greywacke and shales of Ordovician and lower Silurian age, and the land is pre-
dominantly hilly; the highest hill lying entirely within the county is Green Lowther (732 m),
3 km south-south-east of Leadhills, although Culter Fell on the Lanarkshire-Peebleshire
border is 16 m higher. The rocks contain few minerals of economic value, apart from deposits
of lead and small amounts of gold and other metallic ores in the Leadhills district of the
Lowther Hills, and as yet there is no evidence that these ores were exploited in prehistoric or
Roman times.
North of the Southern Upland Fault there is an abrupt change in the scenery, open and
rolling landscape replacing the high hills and deeply incised valleys of the south. An exception
is Tinto (707 m), an igneous intrusion just north of the fault-line and the county's most
conspicuous hill, whose summit commands an extensive prospect in all directions ranging as
far as the Grampians, Goatfell (Arran), Cumbria and Ireland. Elsewhere the rocks are generally

-- 1