HARMONY,   COLOB,   AND   KANAB   COAL  FIELDS,    UTAH.  383 
Igneous  rocks  cover  a  large  part  of  the  surface  of  the  High  Pla- 
teaus north  of  the  coal  fields,  but  in  the  area  under  consideration 
they  are  comparatively  rare.  The  common  type  is  basalt,  which 
occurs  in  lava  flows  on  an  eroded  surface  of  the  sedimentary  rocks 
from  those  of  Eocene  age  downward.  Over  most  of  the  area  these 
igneous  rocks  apparently  have  had  no  effect  on  the  coal,  but  in  the 
Harmony  field  an  intrusive  mass  of  andesite  has  accomplished  con- 
siderable metamorphism. 
STRUCTURE. 
Throughout  the  greater  part  of  the  area  included  in  the  present 
report  the  rocks  dip  between  1°  and  2°  NE.;  but  along  the  western 
margin  of  the  Plateau  Province  the  structure  is  complex  and  the 
strata  are  steeply  tilted,  and  north  of  New  Harmony  the  coal  meas- 
ures adjacent  to  a  mass  of  intrusive  igneous  rock  dip  eastward  at 
high  angles.  The  continuity  of  the  strata  is  interrupted  by  a  num- 
ber of  normal  faults  of  large  displacement.  One  of  these,  the  Hurri- 
cane fault,  extends  along  the  western  border  of  the  plateau  and  has 
been  traced  southward  as  far  as  the  Grand  Canyon  in  Arizona.  In 
consequence  of  this  fault  the  coal  in  the  Colob  field  occurs  about 
2,000  feet  higher  than  that  in  the  Harmony  field.  Several  displace- 
ments, in  general  parallel  to  the  Hurricane  fault,  occur  east  of  it, 
and  in  the  vicinity  of  Cedar  City  especially  the  rocks  are  much 
disturbed.  Another  important  fault  is  the  Sevier,  which  extends 
along  the  upper  valley  of  Virgin  River  east  of  Orderville  and  Glendale. 
This  displacement  has  been  traced  for  many  miles,  both  north  and 
south,  beyond  the  limits  of  the  area  represented  by  the  map  (PL 
XXV).  Within  the  region  here  discussed  the  throw  of  the  Sevier 
fault  amounts  to  about  2,000  feet,  the  downthrow,  as  is  common 
throughout  the  plateau  region,  being  on  the  west.  This  fault  causes 
a  lateral  offset  of  the  coal  outcrop  of  9  miles,  extending  from  the 
vicinity  of  Mount  Carmel  to  a  point  north  of  Glendale. 
THE   COAL. 
OUTLINE   OF  OCCURRENCE. 
Coal  occurs  throughout  the  area  examined  in  the  lower  part  of  the 
Cretaceous  system  between  50  and  500  feet  above  the  top  of  the 
Jurassic  rocks.  In  general,  in  any  one  section  only  one  bed  of  work- 
able coal  has  been  found,  but  in  places  six  are  present.  The  beds  of 
coal  thicken  and  thin  out  like  lenses,  and  no  single  bed  has  been 
found  to  be  continuous  for  more  than  a  few  miles.  In  the  absence 
of  prospecting,  however,  many  facts  relating  to  the  occurrence  of 
the  coal  are  unknown.  It  is  estimated,  on  the  assumption  that  the 
workable  limit  of  the  coal  is  4  miles  back  from  the  outcrop,  that 
there  are  295  square  miles  of  coal  land  in  the  area  examined  in  1907. 
