22 R. H. Tiddeman — Formation of Reef Knolh. 



little visible bedding, but with abundant fossils in a perfect state^ 

 we have still to learn what has become of the shales which ar© 

 almost always present with the black limestone. If squeezed out, 

 as might be suggested, they would at least leave partings behind, 

 and the rock would be moi'e bedded than it is; 



Mr. Marr contemplates the likelihood of several different lime- 

 stones being shifted together to make one reef-knoll, but if so, are 

 we not as likely to get the thin sandstones of the Pendleside Grit 

 sandwiched into them as well? Yet sandstones and shale-beds are 

 unknown in the reef-knolls. 



Mr. Marr makes a number of statements about what he calls the 

 Vs of the Middle Craven Fault. His opinion is that this is a great 

 thrust-plane dipping gently north, and that the Coal-measures are 

 forced beneath the limestone, and so on along its course. A bed of 

 coal in the limestone at Ingleton is regarded by him as having been 

 forced up from underlying Coal-measures by pressure, and not as- 

 originally interbedded. Unfortunatelj' for these views, there are no 

 proper Vs or dipping planes of faulting indicated in the map. The 

 sinuous track of the Craven Fault is not so drawn to accommodate- 

 any theory, but is merely put where the exposures of rock show it 

 to run. Its wanderings are either dictated by or stand in relation 

 to the two principal lines of jointing in the limestone, which range 

 W.N.W. and N.N.W. Sometimes one direction, sometimes the 

 other, has the mastery. At Clapham the line is absolutely straight,. 

 and does not curve up-stream as suggested by Mr. Marr. The coal- 

 seam mentioned is well known to me. On searching it I found 

 several Producti, fairly perfect, embedded in it and filled with it, and 

 the conclusion I came to was that it was either a coal-seam which 

 had grown on a reef and been submerged, or a deposit of seaweed. 

 These Producti seem to disagree with the injection theory. Such 

 coal-seams are found occasionally in the limestone. One near 

 Kirkby Lonsdale has been worked for coal. 



Mr. Marr has mentioned two places where knolls of grit occur. 

 I do not admit that a knoll of grit can have anything in common 

 with the reef-knolls of Craven unless it be the external form ; but if 

 such structures were made by earth thrusts and abounded, it would 

 no doubt be a strong point in favour of his views. One of these 

 grit knolls is said to be in the canal at the back of Shipton Castle. 

 I think this must be an error. I know of no sandstone in that 

 locality, though I know it well. I have consulted others who are, 

 as geologists, conversant with Shipton, competent to form an opinion,, 

 and they agree with me that nothing but limestone and shales occur 

 in that canal at that point. The beds there are certainly contorted, 

 but they are not sandstone, and contortions do not necessarily imply 

 reef-knolls. 



I feel unable to regard Mr. Marr's 'model knoll' as in any respect 

 resembling what I have called reef-knolls. That is, according to his 

 views, a broken plication of a thin hard bed of limestone in a mass 

 of softer shale, the shale surrounding its broken fragments. The 

 knolls to which I allude are almost solid limestone from top to base. 



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