PHOSPHATE    DEPOSITS    IN    WESTERN    UNITED    STATES.  451 
Silurian : 
Thin-bedded  limestone,  where  present. 
Ordovician: 
White  and  green  quartzites. 
Light-colored,  generally  thick-bedded  limestone. 
Cambrian: 
Thin-bedded  blue  and  gray  limestone. 
Quartzites,  mainly  white  in  some  areas,  purple  in  others. 
In  portions  of  the  area  some  parts  of  this  section  are  absent  by  rea- 
son of  nondeposition. 
Three  quartzite  series  are  thus  shown  to  be  present  in  parts  of  this 
region.  Since  the  phosphate  series  occurs  a  short  distance  above  one 
of  these  quartzites,  it  is  important  that  the  prospector  be  able  to  recog- 
nize its  occurrence  in  the  field.  This  can  be  done  in  one  of  two  ways. 
If  a  person  is  familiar  with  the  general  characters  of  the  upper  Carbon- 
iferous fossils,  he  can  readily  recognize  this  part  of  the  section  as  the 
limestones,  especially  those  occurring  in  and  overlying  the  phosphate 
beds  are  very  fossiliferous  and  the  fossils  are  well  preserved.  If  this 
method  is  not  practicable,  he  can  start  from  a  known  base  and  work 
out  for  himself  the  sequence  of  the  various  beds.  The  maps  of  the 
Fortieth  Parallel  Survey  and  of  the  Hayden  Survey  jover  parts  of  the 
known  area  and  would  be  useful  in  selecting  a  starting  point  from 
which  to  make  a  detailed  section.  Owing  to  the  intense  folding  and 
compression  which  the  beds  have  undergone  in  some  localities  and 
their  probable  repetition  by  faulting,  the  latter  method  may  be  found 
difficult  to  follow. 
The  whole  of  this  section  is  known  to  occur  in  Weber  Canyon  and  to 
the  north  in  Utah  and  Idaho.  To  the  south  of  the  Weber,  in  the 
Wasatch  Range,  the  Cambrian  limestones,  the  Ordovician  quartzite, 
and  the  Silurian  and  Devonian  limestones  become  thinner  and  in  some 
places  appear  to  be  entirely  wanting. 
CARBONIFEROUS    SYSTEM. 
GENERAL   DESCRIPTION. 
As  the  phosphate  series  occurs  within  the  Carboniferous  rocks,  a 
more  detailed  description  of  these  strata  will  be  given.  They  outcrop 
over  considerable  areas  in  eastern,  central,  western,  and  northern 
Utah,  southeastern  Idaho,  and  adjoining  portions  of  Wyoming,  and 
in  northern  Nevada.  Their  lithologic  characters  are  very  persistent, 
and  the  three  subdivisions  may  be  recognized  in  the  above-defined 
area. 
The  limestones  which  form  the  lower  division  are  generally  massive 
and  occur  in  bold  and  precipitous  outcrops.  In  many  places  they  are 
coarse  grained  and  weather  rough  and  in  dark  colors.  They  are  also 
rather  siliceous  and  contain  some  cherty  layers  and  masses.  This 
division  is  2,000  feet  or  more  in  thickness. 
