. The Quarterly journal of the Geological Society of London. sseparated by a narrow gap from the cliff. It consists partly of adyke1 and partly of the lavas into which the dyke was dyke is about 6| feet wide, and is a brownish-red rock withfairly large felspar-phenocrysts and some green amygdales. Thisrock is a porphyrite, and is easily distinguished by its felsparsfrom the lavas into which it is intruded, as also by the absence ofthe sandstone-filled fissures and clinker-beds which are so charac-teristic of the latter. West of the harbour of Fishtown of Usan, the olivine-basalts
. The Quarterly journal of the Geological Society of London. sseparated by a narrow gap from the cliff. It consists partly of adyke1 and partly of the lavas into which the dyke was dyke is about 6| feet wide, and is a brownish-red rock withfairly large felspar-phenocrysts and some green amygdales. Thisrock is a porphyrite, and is easily distinguished by its felsparsfrom the lavas into which it is intruded, as also by the absence ofthe sandstone-filled fissures and clinker-beds which are so charac-teristic of the latter. West of the harbour of Fishtown of Usan, the olivine-basalts aresucceeded by a type of volcanic rock which is characterized by largeplagioclase-phenocrysts, as also abundant red and green new type of lava, an enstatite-basalt, is a famoushunting-ground for agates and other secondary minerals,2 and theupper portion of each sheet is seamed by fissures filled with pale- 1 Geol. Surv. 1-inch map, Sheet 57. 2 M. F. Hedclle, Mineralogy of Scotland 1901, vol. i, pp. 75-76, 106, 131,&, pp. 140, 464 DK. A. JOWETT ON THE [Oct. 1913, green sandstone. As the strike is here parallel to the coastline, notmany different lava-flows are exposed. At the liock of St. Skae occurs another dyke1 of porphyrite,which is intruded in close proximity to an important fault. Thedyke and silicified fault-breccia together form a vertical wall of rock WCv. ° -4~£- - ^~^ SB DPfDI o« 33. ?c \m -a u \ v:-A O 1 k ^#r 1 1 u I 3 ^ \ \I7 ^>i 1 | J> \ ..Jft . i ^S 1 s £ S K S u ~ S \ ^m 1 111i ^ \ \ j \ 0- ¥/•( ^ 1 !!?&! s \ 1L1 ^ 2 •£ £ = -S *n V J ilk fc] 0 oG 6 t> N ^lllk ^ \ ^Ik XjJP^Wa ^ ?CJ3 o^^^^ilfe .-£. _3 ^ tm ^ i I) *P 0 \°ll Ik ^ ra »- v* ^x ° yV \ 0- rising from the beach to a height of over TOO feet, and projectingfrom the cliff southwards across a small bay which is flanked oneach side by steep cliffs. The Rock has been tunnelled by the 1 G-eol. Surv. 1-inch map, Sheet 57. Vol. 6g.] VOLCANIC ROCKS OF THE FORFARS
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Keywords: ., bookcentury1800, bookdecade1840, booksubjectgeology, bookyear1845
