AND LEICESTERSHIEE AND THEIR RELATIONS TO OEOLOGICAL STRUCTURE. 101 
towards Melton Mowbray, 10 miles from the outermost visible Chariiian strike-line, 
these older rocks are probably buried under at least 1000-3000 feet of newer strata. 
4. The Igneous Rocks. 
(f) Dolerites Intrusive into the Coal Measures. 
No intrusive dolerites are present in the visible outcrop of the Coal Measures of the 
Yorkshire and Nottinghamshire Coalfield, but in the concealed portion of the coalfield 
several dolerites have been proved through the medium of deep borings. 
One of these intrusions occurs in the central part of the area under consideration. 
It was penetrated by the Owthorpe boring at a depth of 1743 feet below O.D. 
Where pierced by the bore-hole the rock was only 40 feet thick.Further north two 
other examples have also been met in bores through the Coal Measures. One of these 
is at Kelham near Newark, where a thickness of 77 feet of dolerite was proved 
between 1715 and 1792 feet below O.D.t The other is near South well,| about seven 
miles E.N.E. of Newark. 
In the west of the district a dolerite has been pierced by a number of shafts near 
Whitwick in the Leicestershire coalfield. This rock occurs over an area of about 
3|- miles by 1 mile, and varies from 15 to 81 feet in thickness. It rests upon the 
upturned edges of the Coal Measures, but it is said not to alter the Triassic rocks 
above. § 
In other parts of the country the frequent association of intrusive basic rocks with 
Coal Measure strata is well known. It is only necessary to mention the intrusions at 
Rowley Regis, Walsall, &c., in the South Staffordshire Coalfield,|| at the Clee Hills in 
Shropshire, and elsewhere. Similar dolerites are occasionally intrusive into lower 
horizons of the Carboniferous Rocks. They are found for example in the Millstone 
Grit, and in the Carboniferous Limestone of Shropshire,^ and in the Lower Carboniferous 
Rocks of Scotland. 
It has Hot yet been established whether these intrusions are of pre-Triassic age or 
younger, but the question is not of great importance so far as this investigation is 
concerned, for despite the wide outcrop of the Mesozoic rocks in the Midlands, 
and although their underground extension has been well explored by borings and 
deep wells, the only intrusion known to occur in them is the one at Butterton, 
“ The Geology of Newark and Nottingham,” ‘ Mem. Geol. Survey,’ 1908, p. 106. 
t “The Concealed Coalfield of Yorkshire and Nottinghamshire,” ‘Mem. Geol. Survey,’ 191.3, p. 58; 
also A. Stkahan, ‘Lecture to Royal Institution of Great Britain,’ March 17, 1916, p. 6. 
X The details of this boring have not at present been made public. I am indebted to Dr. Walcott 
Gibson for information as to the occurrence of the intrusive rock. 
§ “ The Geology of the Leicestershire and South Derbyshire Coalfield,” ‘ Mem. Geol. Survey,’ 1907, 
p. 33. 
II W. W. Watts, “ Geology of the Birmingham District,” ‘ Proc. Geol. Assoc.,’ vol. XV. (1898), p. 397. 
11 W. W. Watts, “ Geology of South Shropshire,'” ‘ Proc. Geol. Assoc.,’ vol. XIII. (1894), p. 343. 
