156  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   1903.  [bull. 225. 
has  been  found  both  in  lodes  and  in  alluvial  deposits  at  a  number  of 
widely  separated  localities. 
In  1903  the  writer,  assisted  by  Mr.  Frank  L.  Hess,  was  detailed  to 
continue  the  investigation  of  the  mineral  resources  of  Seward  Penin- 
sula. In  the  course  of  the  investigation  the  York  region  was  again 
visited,  hasty  examinations  were  made  of  the  three  localities  which 
give  the  most  promise  of  the  production  of  tin,  and  reports  were 
obtained  from  many  other  localities  which  have  been  prospected  to 
some  extent.  The  three  localities  visited  are  known  as  Lost  River, 
Buck  Creek,  and  Cape  Mountain,  the  two  extreme  points  being  25 
miles  apart.  The  examination  of  the  Lost  River  locality  was  made  by 
Mr.  Hess  and  the  writer,  jointly,  while  Buck  Creek  was  visited  by 
Mr.  Hess  and  Cape  Mountain  by  the  writer. 
GENERAL  GEOLOGY  OF  THE  YORK  REGION. 
The  geology  of  the  York  region  has  been  the  subject  of  investiga- 
tion during  the  years  1900,  1901,  and  1903,  but  all  of  this  work  has 
been  of  a  reconnaissance  character.  Four  distinct  rock  types  have 
been  recognized  in  the  region.  These  include  slates  and  limestones, 
both  probably  of  Paleozoic  age,  and  some  granular  intrusives,  chiefly 
of  acid  character.  The  slates  and  limestones,  broadly  speaking,  form 
north-south  belts  of  irregular  outline,  while  the  igneous  rocks  are 
found  in  intrusive  stocks  or  dikes,  the  former  outcropping  in  more  or 
less  circular  areas.  Besides  these  bed-rock  formations,  Pleistocene 
sands  and  gravels  mantle  the  northern  coastal  plain,  and  are  also  found 
along  the  valleys  of  many  of  the  streams. 
The  larger  part  of  the  area  of  the  York  Mountains  is  occupied  by 
limestone  of  ash-gray  color,  which  exhibits  little  evidence  of  meta- 
morphism.  This  formation,  called  the  Port  Clarence  limestone  in 
previous  reports,  is  of  upper  Silurian  age.  West  of  this  large  lime- 
stone area  there  is  a  broad  belt  of  slates  or  phyllites,  often  so  much 
altered  as  to  be  more  properly  called  schists.  They  are  of  a  graphitic 
arenaceous  and  sometimes  calcareous  character,  are  of  a  tine  texture, 
and  are  much  jointed,  the  lines  of  cleavage  breaking  them  into  rhom- 
boidal  blocks  and  pencil-shaped  fragments.  The  bedding  is  often 
obscured  and  sometimes  completely  obliterated  b}^  the  highly  devel- 
oped joint  structures. 
The  age  of  these  slates  and  their  relation  to  the  Port  Clarence  lime- 
stone have  not  been  determined.  There  is  some  indication  of  faulting 
along  the  contact. 
West  of  the  slate  area  there  is  a  belt  of  highly  altered  limestone 
more  or  less  interbedded  with  micaceous  schists.  This  belt,  about  4 
miles  in  width,  lies  between  the  slates  on  the  east  and  the  large  mass 
of  granite  which  forms  the  peak  known  as  Cape  Mountain  on  the 
west,     Some  obscure  fossils  collected  last  season   indicate  that  these 
