362         CONTRIBUTIONS   TO    ECONOMIC   GEOLOGY,    1907,    PART    II. 
principal  meridian.     The  following  is  a  section  of  the  horizontal  coal- 
bearing  rocks  at  the  prospect : 
Section  of  coal-bearing  rocks  in  sec.  36,  T.  36  N.,  R.  1  W. 
Sandstone  and  shale,  largely  covered. 
Coal  bed,  burnt.  Ft.    in. 
Shale,  brown,  carbonaceous 6 
Covered 15 
Shale,  carbonaceous 14 
Coal 5      6 
Shale,  brown,  carbonaceous 9 
Coal 1 
Shale,  carbonaceous 1 
Coal 1      3 
Sandstone,  carbonaceous 2 
Sandstone,  massive,  white 50 
104       9 
Two  coal  beds  3  feet  or  more  in  thickness  are  reported  by  J.  E. 
Chapson,  of  Pagosa  Springs,  as  occurring  above  the  5^-foot  bed  shown 
in  the  above  section.  Possibly  one  of  these  beds  is  represented  by 
the  burned  zone  at  the  top  and  the  other  in  the  covered  area  of  15 
feet  near  the  top  of  the  section.  Coal  has  been  mined  for  local  use 
at  the  prospect. 
In  the  eastern  part  of  the  SW.  J  sec.  31,  T.  36  N.,  R.  1  E.,  there 
has  been  some  local  mining.  The  bed  at  this  point  measures  10| 
feet,  with  shale  above  and  below.  The  coal  has  a  black,  shiny  luster, 
and  mines  out  in  rather  thin  layers. 
It  is  the  writer's  opinion  that  the  coal  beds  in  the  region  under 
discussion  are  Laramie  and  have  been  preserved  by  block  faulting 
adjacent  to  the  San  Juan  Mountains.  The  exposures  are  within  1 
mile  of  the  igneous  peaks  and  1,000  feet  above  San  Juan  River.  The 
coal-bearing  rocks  are  largely  covered  by  talus  and  spruce.  There 
is  evidence  of  a  fault  in  the  vicinity,  but  no  attempt  was  made  to 
trace  the  sedimentary  boundaries  or  to  map  the  structure.  The 
coal  sections  with  the  massive  white  sandstone  at  the  base  are  closely 
similar  to  sections  on  the  north  side  of  the  main  Laramie  outcrop, 
and  on  this  basis  alone  the  identification  is  made. 
For  purposes  of  comparison  the  analyses  of  three  other  samples 
from  the  vicinity  of  Durango  are  given  on  page  363.  Sample  No.  2092 
is  from  bed  No.  3,  at  Porter,  and  No.  3552  from  Perrine  Peak.  Both 
of  these  samples  are  from  coal  in  the  Mesaverde  formation.  Sample 
No.  3551  was  obtained  3  miles  southeast  of  Durango  and  is  repre- 
sentative of  the  Laramie  coal  in  this  district. 
