THE POST-DRIFT FOSSILS OF THE CLYDE DRAINAGE 



AREA AT LOW LEVELS. 



BY JOHN SMITH, THOMAS SCOTT, F.L.S., and JAMES STEEL. 



A SHORT distance below and above the present sea-level in the Clyde area 

 there occur a series of beds containing Arctic shells, many of which are now 

 extinct in the Clyde estuary and in British seas. These beds sometimes rest 

 on rock or Boulder-clay, but often on a very fine-grained laminated clay 

 which contains no organic remains except a few foraminifera. 



The deposits passed through in sinking coalpits at Bogside, Lucknow, and 

 Misk, on the Ayrshire coast, may have belonged to the same period. In the 

 latter pit they reached a depth of 42 feet below sea-level. Large scratched 

 boulders, covered with polyzoa, etc., were found in them, along with Arctic 

 shells. 



The Raised-Beach beds are clearly distinguished from the glacial or Post- 

 drift deposits above mentioned, (a) by the absence of boulders, (6) by the 

 absence of extinct shells of boreal habit, and (c) by the presence of remains 

 of the recent Clyde estuarine fauna. Only the youngest Raised-Beach (which 

 lies at about 10 feet above present high-tide mark) and the 40-feet one 

 possess distinctive features and show fairly continuous lines, but the others 

 occur in patches, up to a height of 120 feet above sea-level. As these beaches 

 principally consist of sandy deposits, the organic remains have now either 

 wholly disappeared from many of them or are only represented by decayed 

 fragments. To this there is one notable exception : this is the 40-feet Beach 

 at Shewalton near Irvine, which still contains quantities of shells, and these 

 are exposed after floods in the river. 



The lower Raised-Beaches contain at least two beds of peat in situ as they 

 were laid down, which are covered by shelly deposits, bearing evidence to 

 changes of level during their deposition. At present the shores along the 

 Ayrshire coast are sinking. 



The Post-drift, or as they were formerly known, the Post-tertiary, 

 deposits of the West of Scotland were first investigated largely by the late 

 James Smith of Jordanhill, whose numerous papers on the subject to the 

 Wernerian Society and other bodies were begun in 1836. After his time the 

 work was carried on by Dr. David Robertson and Rev. Dr. Crosskey amongst 

 others, which resulted in the full account of the beds and their fossil remains 

 published in the " Catalogue of the Western Scottish Fossils " in 1876, where 

 a detailed description of many of the localities will also be found. 



Since that time considerable additions have been made through the 

 exhaustive work carried on at Garvel Park Dock, Greenock, and elsewhere 

 in the area, with the result that the present may be taken as a fairly 

 complete list of the organisms found in the low-level Post-drift beds of the 

 Clyde area. 



