FROM THE TERTIARY LAVAS AROUND BEN MORE, MULL. 



zone occurs on An G earn a and Beinn Fhada, two ridges running from Ben More in 

 a north-westerly direction, and also on Maol nan Damh, a spur running south-west 

 from Ben More towards Loch Scridain. Its distribution is indicated on the accom- 

 panying sketch-map (fig. 1), and, as the geology of the region is complex, I include 

 here short descriptions of the localities, kindly furnished by Mr Richey, who surveyed 

 An Gearna and Beinn Fhada, and Mr Anderson, who mapped Maol nan Damh :— 



"The parallel ridges of Beinn Fhada and An Gearna are situated at the western 



Fig. 1. — Map showing the distribution of the zeolite-bearing zone 

 (dotted) and the granophyre (crossed). 



border of the Mull plutonic centre. Tertiary plateau lavas form the country rock 

 which is intruded by plutonics, sheets and dykes. The lavas are olivine basalts 

 making thick cappings to the hills. A large granopbyre mass (the Beinn a' Ghraig 

 granophyre) cuts through Beinn Fhada and ends in the valley below, not reaching 

 to An Gearna. Its junctions with the lavas, seen in extenso on the hill-face, slope 

 steeply outwards, while the valley stream -sections show a like relation in detail. 

 On the south-east end of Beinn Fhada part of an earlier granophyre is cut ofi' against 

 the granophyre of Beinn a' Ghraig. 



" There are two series of sheets both intermediate between the granophyres in age. 

 The belt of thin inclined sheets which encircles the Mull plutonic centre crosses 



