PorthySga. 
EXPLANATION. 
Up.  Hornblende  pierize. 
iia.  Hornblende  diabase. 
o’.  Gabbro  etc. 
Granite . 
Ordosncian  or 
Looser  Silurian . 
[>r  ^  7->| 
Granitoid  rock. 
Diabase,  etc. 
Schists. 
Porth  LI  an.',  ax 
Limestone.  \CSchistoserrocks  •which  maj 
include  some  igneous../ 
Localities  'inhere 
Variolite  occurs. 
Dinas-fach  * 
Dinas  Fawr 
Porth  Orion 
Braich  Anneiog 
Braich  y  Pwll 
Maen  me/y"  !|eyr:\ 
Paf€dl"C 
My 
d° 
gr.. 
err. 
BARDSEY 
ISLAND 
eo//ioyn 
SKETCH-MAP 
of  the  Sr  w.  part  of  the 
LLEYN  PENINSULA 
(CAERNARVONSHIRE) 
SCALE.  zkinc]i=i  mile. 
Maen  du 
1 3 r:  •  v; ier-  Cr. Sc. 
The  outcrops  of  igneous  roots  beyond  the  important  lines  of  fault,  which 
extend  east  of  Llangwnadl.  are  copied  from  Mr.  Alfred  Harter's  map  in  ‘  The 
Bala  Volcanic  Series  of  Caernarvonshire,’  p.  59.  The  areas  marted  ’  Lower 
Silurian,  with  their  faulted  boundary,  are  taten  from  the  Geological  Survey 
map  :  these  strata  are  probably  of  Ordovician  age.  The  country  west  of  the  main 
faults  which  is  left  blant  is  generally  covered  with  drift.  Numerous  diabase 
dykes  cut  the  roots  along  the  coast  of  the  Lleyn,  but  it  is  impossible  to  show 
them  on  a  map  of  this  scale. 
Q.  J.  G.  S.  No.  T9T.  ji 
