268 H.C. Sargent—Carboniferous Cherts in Derbyshire. 
bedding lines of the overlying rock curve over the nodules, showing 
clearly that the latter were in sitti before it was deposited (Fig. 1). 
Under similar conditions the bedding lines of the rock below a 
nodule are disturbed to conform with the irregular under-surface 
of the nodule (Fig. 2). The last feature appears to prove that 
the chert had consolidated more rapidly than the calcareous ooze 
into which it was pressed down. 
<A 
Parcel Ee 
Fic. 1.—Chert-nodules in shaly, laminated limestone, Shiningbank Wood, 
near Alport. Solid limestone above and below the shaly bed. 
{ 1 
=X 
Fic. 2.—Chert-nodule, Lovers’ Walk, Matlock Bath. Solid limestone above, 
shaly, laminated limestone below the nodule. 
Cracks in the nodules, or sheets, are often filled with limestone, 
which appears to be obviously contemporaneous with the enclosing 
rock} 
It may often be seen that the upper surface of a sheet of tabular 
chert is quite level, as if spread out by currents, and contrasting 
strongly with the irregular lower surface. A rough flow-structure 
may sometimes be seen in thin sections. 
Contemporaneity is not claimed for chert filling fissures or joints 
in the limestone. Such occurrences are rare in Derbyshire, and 
they appear to be clearly of later formation. In the few instances 
1 Cf. W. A. Tarr, ‘‘ Origin of the Chert in the Burlington Limestone” : 
Amer. Journ. Sct., vol. xliv, 1917, p. 422. 
