THE RH^TIC ROCKS OF NOTTINGHAMSHIRE. 
195 
observed at Newark by tlieRev. A, Irving,* and Mr. Horace Woodward,! 
and at Elton Station on, the Nottingham and Grantham Line by Mr. 
11. Etheridge, F.R.S. All these sections, however, were more or less 
imperfect either above or below. 
Seven or eight years ago, several new and some complete sections of 
the Rhsetic rocks were exposed on the eastern and southern borders of 
Nottinghamshire, chiefly by new railway works. These sections, un¬ 
fortunately, are now all covered up and grass-grown. As, however, 
they disclosed several interesting facts and some new features, a record 
of them seems desirable. 
The Rhsetic formation in this country is usually subdivided 
into three groups of rocks, viz.: (1) Loioer Rhcetic: grey or green 
indurated marls (“ Tea-green marls ” of Etheridge); (2) Avicula 
contorta series (black fissile shales, with thin seams of sandstone 
and limestone, with or without one or more bone beds) ; and (3) 
Upper Rhcetic or White Lias (a variable series of shales and light- 
coloured limestones). This threefold division has generally been con¬ 
sidered to hold good for Nottinghamshire. In this and the adjoining 
counties we get at the top (3) a series of pretty thickly laminated grey 
marls with bands, or layers of blue-centred nodules of limestone (con¬ 
taining Estheria viinuta). Below these we have (2) the characteristic, 
black, thinly-laminated shales of the Avicula contorta series, and beneath 
these come (1) a series of indurated unfossiliferons light blue maiis that 
weather a yellowish green, and break up into cuboidal fragments— 
for reasons presently to be given, I would take these “ Tea-green 
marls ” from the Rhsetic and relegate them to the Keuper formation 
(see Fig. 1). 
I now proceed to briefly describe the chief Rhaetic sections that 
are or have been exposed in this district : — Gainsborough: In the 
cuttings of the Great Northern Railway, at Lea, near Gainsborough, 
Lincolnshire, the Avicula contorta beds represented by at least 25 feet of 
fossiliferous black shales, with several bands of micaceous sandstone 
and one or two “ bone beds,” may be seen resting with conformable 
stratification on “an eroded surface” of blue marl of the Upper 
Keuper series; The upper portion of the cutting is occupied by Glacial 
drift, which appears to cut out the higher beds of the Rhaetics at this 
point. The Gainsborough section is remarkable for the exceptional 
development of the Avicula contorta beds, and for the numerous and 
thick bands of sandstone they contain. Its preservation as a section is, 
I understand, due to the benevolence of the Great Northern Railway 
Company, the cutting being left vertical and bare for some distance 
where the Rhaetics outcrop, a favour for which all local geologists 
should be grateful. Mr. F. M. Burton, F.G.S., who accurately described 
this highly interesting section in the year 1867, then thought that the 
Rhaetics were limited to a small area of three or four miles long, by a 
* “ Proceedings of the Geologists’ Association,” vol. iv, 
t “Geological Magazine,” October, 1874. 
