CLAYS  AND  SHALES  IN  CENTRAL  PENNSYLVANIA.     443 
no  information  could  be  gained  of  its  thickness  or  character.  In  the  case  of  the  shales  the 
notes  are  confined  to  the  deposits  lying  near  transportation,  which  alone  can  be  considered 
at  the  present  time  as  of  commercial  value. 
DISTRIBUTION   OF  FLINT-CLAY  DEPOSITS. 
Center  County.— The  rise  of  the  rocks  from  Moshannon  Creek  toward  the  southeast  to 
the  Allegheny  Front  exposes  the  horizon  of  the  Mercer  clay  all  along  the  northwestern 
flank  of  the  mountains  facing  the  creek.  Little  is  known  of  the  clay  in  this  region,  except 
at  Sandy  Ridge,  where  it  has  long  been  worked.  Here  there  are  about  2  feet  6  inches  of 
flint  clay,  overlain  by  from  3  to  6  feet  of  soft  blue  clay  and  underlain  by  from  1  to  3  feet 
of  soft  clay.  The  exposure  here  is  just  at  the  outcrop.  The  bed  dips  below  the  surface 
to  the  northwest  and  may  in  the  future  be  mined  in  that  direction  by  shafts,  should  pros- 
pecting prove  it  to  be  present  and  of  workable  quality  and  thickness. 
Clearfield  County. — From  its  outcrop  on  the  Allegheny  Mountains  the  Mercer  clay  is 
carried  below  drainage  under  the  Houtzdale  syncline,  containing  the  Houtzdale  coal  basin, 
but  it  rises  again  above  drainage  on  the  flanks  of  the  anticline  which  runs  from  McCartney 
to  near  Wallaceton  and  beyond.  This  arch  is  low  at  either  end,  but  rises  so  that  the 
Mercer  clay  is  in  the  hilltops  at  an  elevation  of  over  2,000  feet  above  sea  level  to  the  north- 
east of  Burly.  It  is  carried  down  to  the  northeast  by  the  sinking  of  the  anticline  until  it 
is  but  little  above  the  railroad  between  Wallaceton  and  Bigler  at  elevations  of  1,750  to 
1,770  feet.  Along  the  crest  of  the  anticline  it  is  exposed  at  a  large  number  of  points  and 
has  been  mined  in  every  direction  from  Burly.  In  this  district  it  ranges  from  6  to  8  feet 
in  thickness  and  occasionally  shows  12  or  15  feet.  It  is  also  exposed  on  the  roads  north- 
west of  Sanbourn  at  a  number  of  points.  It  has  been  mined  extensively  in  the  crest  of 
the  hill  2  miles  west  of  Blue  Ball  and  outcrops  at  several  points  a  similar  distance  west  of 
Wallaceton.  Along  the  Tyrone  and  Clearfield  branch  of  the  Pennsylvania  Railroad,  and 
the  Beech  Creek  division  of  the  New  York  Central  and  Hudson  River  Railroad,  it  is  exten- 
sively mined  between  Wallaceton  and  Woodland,  rising  above  drainage  at  Wallaceton. 
In  this  district  it  shows  a  maximum  thickness  of  10  or  11  feet,  though  the  portion  mined 
and  the  average  thickness  will  be  much  less.  In  most  of  the  mines  it  ranges  from  2  feet  6 
inches  to  4  feet.  The  worked  stratum  is  apt  to  be  irregular  both  in  thickness  and  in  quality. 
It  is  often  overlain  and  underlain  by  impure  or  soft  fire  clay.  On  Clearfield  Creek  its  hori- 
zon is  above  drainage  from  a  little  north  of  Madera  to  the  mouth  of  the  creek.  It  was  not 
seen  south  of  Faunce  in  the  main  valley,  but  it  outcrops  on  North  Branch  of  Upper  Mor- 
gan Run.  At  Faunce  the  clay  has  a  thickness  of  about  6  feet,  but  usually  only  a  part  of 
that  is  workable.  It  has  been  worked  again  at  Chase,  where  the  flint  portion  of  the  clay 
is  only  2  or  3  feet  thick,  the  soft,  sandy  clay  being  both  above  and  below.  At  these  points 
the  clay  occurs  about  200  feet  above  the  level  of  the  creek,  but  descends  toward  the  mouth 
of  Little  Clearfield  Creek.  The  clay  is  below  water  level  under  all  of  the  Little  Clearfield 
Creek  drainage.  It  rises  from  water  level  at  Curwensville,  being  exposed  just  above  the 
Buffalo,  Rochester  and  Pittsburg  Railroad  track  directly  across  from  town,  though  of  poor 
quality.  It  runs  up  Little  Anderson  Creek,  Biglers  Run,  and  Anderson  Creek  and  has 
been  opened  and  worked  at  a  number  of  points.  It  also  outcrops  over  quite  an  area  on 
Hogback  Run  to  the  north  of  Curwensville.  In  this  district  it  shows  a  maximum  thick- 
ness of  18  feet,  though  most  of  the  operations  on  it  do  not  mine  more  than  6  or  8  feet,  and 
often  less.  At  Stronach  the  "nodular"  clay  is  from  a  knife-edge  to  6  feet  thick,  and  the 
"block"  clay  below  from  2|  to  7  feet  thick.  There  is  usually  some  black  shale  between 
the  clay  and  the  overlying  Mercer  coal.  On  Anderson  Creek  the  clay  is  from  2\  to  10  feet 
thick.  On  Hogback  Run  the  clay  is  reported  to  show  locally  as  much  as  8  feet  of  "nodu- 
lar" clay  overlying  11  feet  of  "block"  clay.  In  places  this  changes  to  as  high  as  11  feet 
of  "nodular"  clay  over  7+  feet  of  "  block"  clay. 
Farther  up  Susquehanna  River  it  again  appears  above  drainage  at  the  mouth  of  Porter 
Run  and  remains  above  water  level  to  the  sharp  bend  below  Bells  Landing.  The  Mercer 
horizon  rises  above  Susquehanna  River  just  west  of  Mahaffey  and  continues  for  several 
