Vol. 69.] THE VOLCANIC ROCKS OF THE FORFARSHIRE COAST. 459 



21. The Volcanic Rocks of the Forfarshtre Coast and the Asso- 

 ciated Sediments. By Albert Jo-\vett, D.Sc. F.G.S. (Bead 

 June 11th, 1913.) 



[Plates XLV & XL VI.] 



Contents. 



Page 



I. Introduction 459 



II. Field-Eelations of the Eocks 401 



(a) Montrose to Lunan Bay. 



(b) Lunan Bay to the Bed Head. 



[II. Petrography of the Igneous Bocks 472 



(a) Lavas. 



(b) Dykes. 



IV. The Sediments Associated with the Lavas 475 



(a) Petrography of the Sediments. 



(b) Amygdaloidal Sediments. 



(c) Metamorphism of the Sediments. 



V. Fault-Breccias 480 



VI. Conclusions 481 



I. Introduction. 



The earliest description of the volcanic rocks of Lower Old Bed 

 Sandstone age, which are so admirably exposed on the coast of 

 Forfarshire, we owe to the Bev. John Fleming, 1 whose observations 

 were in a remarkable degree unprejudiced by the theories prevalent 

 at the time when he wrote. 



A fuller account of the rocks as they appear in the field is 

 given by Sir Archibald Geikie in his ' Ancient Volcanoes of Great 

 Britain;' 2 but no attempt has been made, up to the present, to 

 describe the rocks of this locality as they appear under the micro- 

 scope, although similar rocks in adjoining areas 3 have been so 

 dealt with. 



The Geological Survey 1-inch maps 1 clearly indicate the occurrence 

 of a great anticline, a continuation of the Ochil Axis, which runs 

 in a general east-north-easterly direction, passing out to sea near 

 Montrose, 3 where exposures of the oldest lavas may be seen. 

 On following the coast southwards from Montrose, one meets with 

 higher beds in the volcanic series ; these extend as far as the 

 Lunan-Bay sands, beyond which a newer and higher series of lavas 



1 ' On the Mineralogy of the Redhead in Angus-shire ' Mem. Wern. 

 Nat. Hist. Soc. vol. ii, pt. 2 (1815-18) p. 339. 

 - Vol. i (1897) pp. 299-301. 



3 'The Geology of Central & Western Fife & Kinross' Mem. Greol. Surv. 

 1900 ; ' The Geology of Eastern Fife ' Mem. Geol. Surv. 1902 ; E. Campbell, 

 ' Geology of S.E. Kincardineshire' GgoI. Mag. dec. 5, vol. viii (1911) p. 69. 



4 Forfar, Sheet 57 ; Arbroath, Sheet 49. 



5 Sir Archibald Geikie, ' Ancient Volcanoes of Great Britain ' vol. i (1897) 

 p. 299. 



