19^2. The B)itish Association in Belfast. 279 



Mr. Cunningham Craig asked if the thrust really affected the Old 

 Red Sandstone, and what its actual age was. 



Mr. Barrow, in replying, said the movement was undoubtedly lower 

 than any part of the Old Red Sandstone. Movements of the kind were 

 progressive, and as one came further away from the centre where they 

 had started they gradually became of a newer age. 



THE POST-GIvACIAL DEPOSITS OF THE BELFAST DISTRICT. 



BY R. I,I,OYD PRAKGER- 



The silted-up head of Belfast Lough and other similar places in the 

 district display a remarkably fine series of deposits, extending from the 

 close of the glacial epoch to the present day, with a rich fauna, from 

 which much of the history of the intervening period may be gleaned. 

 A typical section at Belfast shows the following sequence : — 



Feet. Inches. 

 Surface clays, . . . . .66 



Yellow sand, . . . . .20 



Blue clayiyPP^^' ' * ' ' ^ ° 



(Lower, . . . .00 



Grey sand, . . . . • .20 



Peat, . . . . . • .16 



Grey sand, . . . . • .20 



Red sand, . . • • • .40 



Boulder clay (base not reached), . . 15 o 



45 o 



The peat bed, which at Belfast is twenty feet below low- water level, 

 reappears between tides at various other places in the district. It repre- 

 sents an old land surface, and its fossils include the " Irish Elk." The 

 blue clay is the most important bed of the series. Two divisions can be 

 clearly distinguished in it, the lower clay being littoral, and characterised 

 by such shells as Scrobicularia piperaia, the upper yielding an abundant 

 fauna pertaining to five or ten fathoms of water ; Thracia convexa is a 

 characteristic fossil. In both clays some of the bivalves occur in beds, 

 each shell in its natural position, and many of the species attain remark- 

 ably large proportions. In places the Scrobicularia clay is overlaid by 

 raised beaches. Thus at Larne twenty feet of stratified gravels, contain- 

 ing marine shells and neolithic implements throughout, replace the 

 Thracia clay, and serve to date it. The fauna of the Thracia clay has a 

 distinctly southern aspect when compared with the present fauna. As 

 regards oscillations of level, the peat proves a level higher than the 

 present in certain places by at least thirty feet. Subsidence, irregular 

 both as regards rate and area affected, superseded to the extent of fifty 

 to eighty feet ; the final elevation, which brought about the existing 

 state of things, amounted to thirty or forty feet. As regards climate, the 

 northern fauna of the glacial period appears to have passed away by the 

 time the peat was formed Southern species immigrated till the 



