788  PRE-CAMBRIAN    GEOLOGY    OF    NORTH   AMERICA. 
transition  here.  However,  the  granite  became  a  true  porphyry  in 
places,  a  fact  difficult  of  explanation  unless  it  is  regarded  as  a  later 
intrusive. 
In  the  Cambrian  of  the  Little  Cottonwood  was  found  a  conglomer- 
ate which  carries  unmistakable  granite  pebbles  and  black  fragments 
which  were  thought  in  the  field  to  resemble  the  black  hornblendic 
areas  so  often  observed  in  the  granite.  These,  however,  when  ex- 
amined in  thin  section  were  found  to  be  entirely  unlike  those  contained 
in  the  granite.  The  granite  fragments  are  small  and  sparse  and  do 
not  appear  to  be  lithologically  like  the  massive  granite  of  the 
CottonwTood. 
An  examination  of  Weber  Canyon  and  of  the  Farmington  area 
showed  that  the  rocks,  instead  of  always  having  a  western  dip  as 
described,  are  most  intricately  and  minutely  folded  and  dip  both  east 
and  west,  although  having  a  general  sameness  of  dip  for  considerable 
areas.  In  this  canyon  and  in  Sawmill  Canyon  a  search  for  evidence  of 
unconformity  between  two  series  of  Archean  rocks  was  unsuccessful. 
The  schists  and  gneisses  are  cut  by  pegmatitic  granite  veins  in  the  most 
irregular  and  intricate  fashion.  The  main  mass  of  the  lower  part  of 
the  Sawmill  Canyon  Archean  is  a  series  of  schists.  In  going  up  the 
canyon,  granite  begins  to  appear,  cutting  the  schists,  and  becomes 
more  and  more  prominent  until  it  is  the  most  abundant  material. 
It  is  here  exceedingly  coarse,  and  the  whole  appearance  is  that  of  an 
intrusive  which  has  cut  the  schists  and  gneisses  by  numerous 
apophyses.  It  is  probable  that  the  small  area  referred  to  by  King  as 
being  the  older  unconformable  Archean  was  not  found. 
Boutwell,51  in  1903,  stated  that  the  granite  of  Lone  Peak  and  Little 
Cottonwood  canyons,  the  granodiorite  at  the  heads  of  Big  and  Little 
Cottonwood  canyons,  American  Fork,  and  Snake  Creek,  and  the 
diorite  at  the  heads  of  Big  Cottonwood  Canyon,  East  Canyon,  and 
Snake  Creek,  with  its  extension  northeastward  through  the  Park 
City  district,  in  the  form  of  dikes,  are  intrusive.  Their  intrusive 
origin  was  found  to  be  demonstrated  by  the  character  of  the  contacts 
between  the  intrusives  and  the  elastics,  by  the  marmorization  and 
deformation  of  the  adjacent  country  rock,  and  by  the  occurrence  of 
an  unusually  complete  series  of  typical  contact-metamorphic  minerals. 
Their  ages  and  relationships  have  not  yet  been  completely  established. 
Emmons,52  in  1903,  agrees  with  Boutwell  that  the  Little  Cotton- 
wood granite  is  intrusive  into  the  Cambrian  quartzite.  In  1900  and 
1901,  on  the  south  face  of  the  Twin  Peak  ridge,  a  few  miles  below 
Alta,  apophyses  of  granite  were  observed  by  Boutwell,  and  in  1902 
by  Emmons  and  Boutwell,  to  run  across  the  bedding  of  the  quartzite 
for  some  distance,  and  in  one  observed  instance  to  spread  out  again 
in  the  beds  in  a  considerable  body.  It  is  suggested  that  the  Cotton- 
wood quartzite,  the  Clayton  Peak  mass,    some  of    the    porphyritic 
