252 Formation and Age of the Queensberrys. 



family before its final extinction. The maximum thickness of the 

 Birkhill shales is 90 feet. They contain six distinct zones, each 

 characterised by its peculiar group of fossils. The highest band, 

 forming the last of the series, is known as the Rastrites maximus 

 zone, and is immediately followed by the hard Queensberry grits. 

 Ascending the stream from the central anticline of Hartfell shales, 

 we find the same order of succession, terminating in the overlying 

 grits and greywacke. They form the largest part of the Queens- 

 berry structure. The few fossils that they contain are of a 

 dwarfed character, proving that these muddy seas were unfavour- 

 able to graptolitic life. The zonal form, Monograptus exiguu.s, 

 confirms this. 



We are now in a position to enter into the successive stages 

 of mountain building revealed to us by the history of a few small 

 animals in the fight for life throughout a chequered career, 

 finished in an unknown obscurity hundreds of millions of years 

 ago. 



The area now occupied by Queensberry was covered in the 

 Silurian epoch by a great ocean reaching from Ireland across 

 Scotland into Norway, including England and part of Southern 

 Europe. The foundation structure of the hills consists of a thick 

 platform of volcanic lava, representing the Arenig Age. During 

 that period this area was far removed from land ; the water over 

 it was free from earthy sediments or shore deposits. These deep- 

 sea and clear-water conditions are shown by the cherts. Great 

 submarine volcanic eruptions flowed along the ocean floor from 

 the north-west, possibly proceeding from the volcanic vent at Bail 

 Hill, Sanquhar. During the intervals of volcanic activity the sea 

 bed was being covered by a deposit of ooze, formed by the skele- 

 ton remains of minute radiolaria. The deposits in the Girvan dis- 

 trict during this age are 1500 feet, chiefly volcanic ; towards San- 

 quhar they have decreased to 500 feet ; while Queensberry has 

 only 100 feet in the same period. These cherts are succeeded 

 gradually by the Glenkiln shales. From the nature of their grap- 

 tolites, they are found to be contemporary with a similar group 

 in Wales, and are therefore ascribed to the Llandeilo Age. Dur- 

 ing this age a slight elevation of the sea bottom allowed the 

 muddv material to be carried further out, and therefore the Glen- 

 kiln shales are found just within the verge of sedimentation. The 

 various shore deposits of Llandeilo Age total 1000 feet at Girvan 



