part 4] PETROLOGY OF THE ARNAGE DISTRICT. 471 



transition occupies a width of about 10 yards perpendicular to the 

 direction of flow. It is important to note that the fluxion becomes 

 more intense with the development of granitic character, and 

 maintains a rigid direction of north 15° west over the whole 

 exposure. 



Locality 3. — Quarry, north of the Yowlie Burn, 850 

 yards north-west of Hillhead of Ardlethen. — A freshly 

 quarried face here gives another transition from a western outcrop 

 of xenolithic Arnage Type to a mass mainly of acid Ardlethen 

 Type, with streaks and bands of dark biotite-rich, felspar-poor 

 rock ; the acid type passes eastwards into a biotite-rich contam- 

 inated rock, with flattened lenticles of xenoliths. The strike of 

 the fluxion and streaking is north 15° west in both Arnage and 

 Ardlethen Types. This constancy of the strike of the fluxion, 

 observed at both Locality 2 and Locality 3, shows that the two 

 rock-types belong to the same period of intrusion, and that the 

 granitic product cannot be interpreted as a later intrusion — a con- 

 clusion confirmed by the complete absence of intrusive junctions 

 and by the detailed petrography of the product (see p. 472). 



Locality 4. — Old quarry, at the roadfork, 640 yards 

 south -south -east of Ardlethen. — This quarry is much over- 

 grown, but shows the acidic Ardlethen Type with fluxion running 

 north 20° west. The rock holds a few ghosts of xenoliths. 



Locality 5. — Quarry, at the roadside, 340 yards south- 

 south-east of Ardlethen. — This small quarry shows many 

 varieties of contaminated rock, the main variety being a pink, 

 streaky, acidic Ardlethen Type, with less common hornblendic and 

 biotite-rich Aniage Types. All these varieties occur in bands 

 striking north 15° west, and showing a fluxion in the same direc- 

 tion. An acid rock from this locality has been analvsed (see 

 Analysis VIII, Table III, p. 464). 



Locality 6. — Wood, 350 yards south-east of Ard- 

 lethen. — Here occurs a massive homogeneous acid rock, with no 

 visible xenoliths, and showing flow-structure which strikes north 

 10° east. 



Locality 7. — Craigiehill Wood, 700 yards south-east 

 of Ardlethen. — Many bold crags in this wood show a close 

 association of contaminated rocks of Arnage and Ardlethen Types, 

 the former containing garnets and blue hornfels-xenoliths. The 

 strike of the fluxion varies from north 20° west to north 5° west, 

 and is seen in both types of rock. 



Locality 8. — 250 yards north of Ardlethen. — -Garneti- 

 ferous and cordierite-bearing acidified products are here seen lit- 

 par-lit injected into, and mixed by absorption with, garnetiferous 

 blue hornfelses. The contaminated rocks vary from a cordierite- 

 bearing granitic Ardlethen Type, back to a cordierite and biotite- 

 rich type of normal Arnage facies. 



Q.J.G.S. No. 316. 2 k 



