54  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
Structure. — It  is  not  possible,  within  the  limits  of  the  present  report, 
to  discuss  the  structural  features  of  the  area  except  in  a  very  general 
way.  Only  three  periods  of  deformation  since  the  beginning  of 
Paleozoic  sedimentation  are  clearly  shown,  although  more  are  known 
to  have  occurred.  The  first  of  these  took  place  at  the  close  of  the 
Paleozoic,  and  produced  the  sharp  flexures  seen  in  the  Red  Beds  just 
north  of  Ouray,  and  also  in  the  Ouray  limestone  south  of  the  town. 
All  of  these  beds  were  at  the  same  time  given  a  moderate  dip  to  the 
northwest.  The  second  period  occurred  somewhere  near  the  close  of 
the  Mesozoic,  and  belonged  to  the  series  of  movements  that  were 
felt  all  over  the  Rocky  Mountain  area.  It  is  recorded  in  the  gentle 
northerly  dip  of  the  Mesozoic  rocks.  These  later  movements  were 
accompanied  by  comparatively  unimportant  faulting,  which  possibly 
followed  lines  initiated  during  the  earlier  period.  The  final  period 
followed  the  intrusions  of  porphyry,  and,  except  at  few  places,  accom- 
plished little  more  than  local  fracturing  or  Assuring,  accompanied 
by  very  slight  displacements.  The  most  striking  of  the  faults  is  the 
one  passing  across  the  lower  end  of  the  Box  Canyon  of  Canyon  Creek 
and  extending  a  little  south  of  east  to  the  southern  wall  of  the  Amphi- 
theater. By  this  the  older  Paleozoic  rocks  have  been  dropped  300 
feet  to  the  north,  with  Uncompahgre  quartzites  on  the  south  side 
of  the  fault. 
ORE  DEPOSITS. 
GENERAL   FEATURES. 
A  few  of  the  larger  ore  bodies  are  situated  in  localities  where  the 
sion  of  a  group  of  metalliferous  deposits  that  is  widely  developed  in 
the  Silverton  quadrangle,  which  adjoins  the  Ouray  quadrangle  on  the 
south.  While  they  are  thus  in  a  sense  closely  related  to  the  Silverton 
deposits  they  form  a  group  which  possesses  marked  individual  fea- 
tures— features  that  are  in  many  cases  unique  and  of  such  scientific 
interest  as  to  warrant  a  somewhat  fuller  description  than  would  be 
justified  by  the  statistics  of  their  production. 
The  region  in  which  the  ores  occur  is  of  small  area  and  may  all  bo 
Included  in  a  semicircle  with  a  radius  of  4  miles,  described  to  the 
north  of  Ouray  and  having  its  center  about  a  mile  south  of  the  town. 
A  few  of  the  larger  ore  bodies  are  situated  in  localities  where  the 
rocks  are  much  broken  and  disturbed,  and  where  intrusive  dikes  and 
sheets  of  porphyry  occur  in  the  near  neighborhood,  but  many  are 
found  in  formations  which  have  been  only  slightly  disturbed.  In 
the  case  of  the  Black  Girl  and  Newsboy  mines,  on  the  east  side  of 
the  Uncompahgre  River,  the  veins  occur  in  strata  so  regular  and  so 
