Page:VCH Lancaster 1.djvu/41

GEOLOGY

THE Geology of Lancashire is of such a character that probably no other county in England can so well show the mercantile development due to its mineral wealth. The Furness and Ulverston districts with their rich deposits of hæmatite have furnished an abundance of iron ore, and the rich Coal measures which cover a large portion of the county have alone rendered possible the creation of huge manufacturing towns crowded with factories and workshops, whilst the low Triassic plains, with overlying superficial deposits, which form the seaboard from Liverpool to Fleetwood yield a soil well adapted for agriculture. The Carboniferous Limestone and Millstone Grit are admirably fitted for road-making and building purposes, and many of the shales and under-clays associated everywhere with the coal, and the thick layers of boulder clay, are equally useful in the manufacture of bricks and coarse pottery. Many of the large towns are crowded so closely together as to be practically continuous, and it is no fanciful figure of speech to say that at least the southern half of Lancashire is one great workshop.

The general sequence of formations is as follows:—

Blown Sand
Alluvium
Glacial Drift	Boulder Clay and Sands.
Trias	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Keuper Marls and Sandstone. Bunter Sandstone and Pebble Beds.
Permian	$\scriptstyle {\left\{{\begin{matrix}\ \\\ \end{matrix}}\right.}$	Sandstones, Marls, and thin Limestones. Magnesian Limestone.
Carboniferous	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Coal Measures. Millstone Grit. Mountain Limestone Series.
Silurian	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Bannisdale Flags. Coniston Grits and Flags. Stockdale Shales.
Ordovician	$\scriptstyle {\left\{{\begin{matrix}\ \\\\\ \ \end{matrix}}\right.}$	Coniston Limestone Series. Borrowdale Volcanic Series. Skiddaw Slates (in part Cambrian?).

PALÆOZOIC

The only exposures or the older Palæozoic rocks (Ordovician and Silurian) in Lancashire are limited to the Ulverston, Coniston, and Cartmel area, which is geographically a part of the Lake District. They consist of a small patch of Skiddaw Slates, the Borrowdale Volcanic series, and the Coniston Limestones seen in the neighbourhood of Ireleth, and a much larger northern area covered by the Stockdale Shales, Coniston Flags and Grits, and the Bannisdale Flags.

ORDOVICIAN

SKIDDAW SLATES

The Skiddaw Slates, which occupy a considerable area in the adjacent county of Cumberland, consist of from 10,000 to 12,000 feet of dark grey slates, mudstones, and grits, which have undergone so much alteration since they were deposited that the task of determining their general