354 SECTIONAL TRANSACTIONS.— C. 



structure has been demonstrated experimentally by Prof. W. J. Sollas in his models 

 of ' Pitch Glaciers.' 



Lonstrup. — The cMs S.S.W. of Lonstrup form a median longitudinal section 

 through the Rubjerg Knude Hill, the coast scenery resembling that of the Cromer 

 Chfis. The disturbances extend from Grot ten Point to Martorv Bakker, a distance 

 of 2i miles. The material involved consists entirely of drift of two types, clay 

 and sand; but boulder clay associated with gravel and sand flanks the sides of the 

 disturbed zone and is overlain by Saxicava sand and Yoldia clay. The undisturbed 

 glacial clay is exposed between Det lille Blaa and Grotten Point, whilst the under- 

 lying deposit of Oeldre Yoldia clay outcrops in the disturbed zone at Stortorn Pomt. 



The structure shows a progressive development when traced towards the N.N.E., 

 i.e. in the reverse direction to that of movement, and may be divided into three 

 Eones : 



(a) At the Martorv Bakker, where the disturbances were initiated, the arrangement 

 of the sand and lenticles of clay is analogous to that of the englacial deposits 

 in stagnant glaciers of Arctic type. The iceward limb displays evidence of 

 much pressure, including the packing of clay lenticles into a minor ' horst.' 

 To the N.N.E. of this ' horst,' sand predominates. In this zone the original 

 stratigraphical relationship between the clay and sand is lost. 



(6) The central area between Rubjerg Knude Fyr and Brede Rende may be 

 described as a Zone of thrust- planes. Inclined wedges and lenticles of clay 

 and sand form ' pairs of deposits.' The original stratigraphical relationship 

 between the two is preserved, but adjacent ' pairs ' are divided by thrust- 

 planes, the ' pairs ' being repeated many times, suggesting ' fish-scale ' or 

 ' imbricate ' structure. The dip of the thrust-planes gradually increases 

 until vertical, and the zone terminates in a clay ' horst ' near Rubjerg 

 Knude Fyr. 



(c) The Zone of squeezed anticlines. — Between Maarup Kirke and Rubjerg Knude 

 Fyr considerable pressure is shown. The ' roots ' of at least four squeezed 

 anticlines or overfolds occur, the upper limbs of each being a thrust-plane. 



The structure differs from that of the Moen area in the fact that the beds have a 

 uniform direction of dip to the N.N.E., but agrees with the phenomena seen at 

 Moen on the iceward limbs of the ' cores.' 



The Lonstrup sections represent the tectonics of a stagnant glacier as reflected 

 in the lower englacial material. 



The expenses of this investigation were defrayed by a grant from the Dixon 

 Fund of the University of London in 1925. 



Afternoon. 

 Excursion to Chawley and Boar's Hill. 



Tuesday, August 10. 



15. Mr. W. B. Wright. — Stratigraphical Diachronism in the Millstone 

 Grit of Lancashire. 



An examination of the marine bands of the Millstone Grits and Lower Coal 

 Measures of the Rossendale Antichne by the Lancashke Unit of the Geological 

 Survey has demonstrated on the whole the reliability of the zonal scheme estabUshed 

 by Mr. W. S. Bisat. The goniatites, on which the system is based, being found 

 only in thin bands at intervals throughout the succession, showed, at first, a fairly 

 clear-cut subdivision into species. The development being only recorded at well- 

 spaced intervals, there was no baifling continuity of evolution. When, however, 

 as in the upper beds, continuous exposure over a wide area allowed of more extended 

 study, considerable lateral variation became apparent. This became distressing 

 when it amounted to a distinct departure from type, and even more so when it led 

 to the replacement of one zonal form by another in the same marine band, thus giving 

 the impression that the zonal scheme might be, as regards its details, of only local 

 value. The subsequent discovery that the variation was systematic put a new aspect 

 <in the question, however, and it now seems as if what at first appeared a troublesome 



