Geological Society, 263 



PROCEEDINGS OF LEARNED SOCIETIES. 



GEOLOGICAL SOCIETY. 



June 6th, 1917.— Dr. Alfred Harker, F.R.S., President, 

 in the Chair. 



The following communication was read : — 



' Con-elation of Jurassic Chronology.' By S. S. Buckman, F.G.S, 



This paper owes its inception to certain discoveries made by the 

 Officers of the Scottish Geological Survey during their investiga- 

 tions of the Jui'assic deposits of the Isles of Raasay and Skye. 

 The ammonites and brachiopods were sent to the Author for 

 examination, and the sequence of faunas which they disclosed 

 necessarily led to comparison with results obtained in other areas — 

 with Yorkshire, on which the Author had recently written a 

 palajontological chapter for a Geological Survey Memoir, based 

 largely on information and specimens submitted by the Survey; 

 with the Dorset coast, helped by Mr. W. D. Lang's most pains- 

 taking work ; with other areas within the Author's field experience, 

 helped largely by information most freely communicated by Mr. J. 

 AV. Tutcher. The results appeared to be so far-reaching, that 

 permission was asked of the Director of H.M. Geological Survey 

 to lay before the Society a synopsis of the information obtained 

 through the investigations of Survey Officers ; this was kindly 

 accorded, and the present paper is the outcome of research thus 

 originated. 



One of the principles utilized in this paper to ascertain or to 

 surmise faunal sequence where precise information is defective, is 

 that of what may be called 'faunal dissimilarit}- ' — that is, if the 

 deposits of two neighbouring localities A and B, supposedly iso- 

 chi'onous from their sequential position, show diifering faunas, it is 

 a reasonable inference that the faunas are not of the same date. 

 Theoretical stratigraphical coi'relation has usually Avorked along 

 these lines, but the principle involved has not been recognized by 

 name. Now the principle is utilized, not only in regard to neigh- 

 bouring localities, but even more widely, with suggestive results. 



The paper is chiefly concerned with the Liassic Ages hitherto 

 known as Domerian, Charmouthian, Sinemurian. In all of them 

 there is proposed a considerable increase of the number of faunal 

 horizons indicative of consecutive time-intervals, or hemerse. In 

 the case of the fii-st no change of name is made ; but in regard to 

 the other two, subdivision seemed necessary, and each is appor- 

 tioned into three Ages, as follows : — 



Proposed Names. Old Tertns. 



Hiriccian. 

 Wessexian. \- Cliarmouthian. 



Eaasayan. 



Deiran. 



Mercian. \- Sinemurian. 



Lymian. 



