NOTES  ON  CLAYS  AND  SHALES  IN  CENTRAL  PENNSYLVANIA." 
By  George  K.  Ashley. 
Area  discussed. — The  following  notes  are  among  those  collected  during  the  survey  of  the 
Houtzdale,  Curwensville,  and  Punxsutawney  quadrangles,  lying  in  southern  Clearfield 
County,  southeastern  Jefferson  County,  and  northeastern  Indiana  County,  Pa.  The  region 
covered  includes  the  well-known  Clearfield  County  flint-clay  area, 
GENERAL  DESCRIPTION. 
The  rocks  outcropping  in  this  district  belong  in  the  lower  part  of  the  Pennsylvanian  series 
of  the  Carboniferous.  They  include,  first,  the  Pottsville  formation,  composed  of  the  Home- 
wood  and  Connoquenessing  sandstones,  between  which  lies  the  Mercer  group  of  shales, 
clays,  and  coals:  second,  the  Allegheny  formation,  including  the  strata  between  the  Brook- 
ville  and  Upper  Freeport  coals;  and,  third,  the  lower  half  of  the  Conemaugh  formation, 
which  overlies  the  Upper  Freeport  coal. 
The  clay  materials  of  this  area  consist  of  flint  clay,  plastic  clay,  and  shale.  Flint  clay 
occurs  at  four  horizons — three  in  the  Allegheny,  which  appear  to  be  of  rather  limited  dis- 
tribution and  minor  importance,  and  a  fourth  at  the  Mercer  horizon  in  the  middle  of  the 
Pottsville  formation.  In  the  Allegheny  formation  flint  clay  occurs  below  the  Upper  Free- 
port  coal  in  a  position  possibly  corresponding  with  that  of  the  well-known  Bolivar  flint 
clay.  It  has  been  found  at  a  number  of  points  in  the  Little  Mahoning  Creek  drainage. 
Flint  clay  has  been  noted  at  the  horizon  of  the  Middle  Kittanning  coal  at  a  number  of 
widely  separated  points,  notably  about  Westover  and  near  McCartney,  in  Clearfield  County. 
The  Lower  Kittanning  coal  is  underlain  by  Flint  clay  in  the  Little  Mahoning  Creek  drain- 
age. The  Mercer  coal  is  underlain  by  flint  clay,  which  at  present  is  the  principal  bed 
being  mined  in  Clearfield  County.  It  is  present  throughout  a  broad  stretch  of  country, 
ranging  from  Grampian  eastward  down  the  Susquehanna  Valley  to  Clearfield,  up  the  Clear- 
field Creek  drainage  to  the  south  and  southeast,  and  over  into  the  Moshannon  Creek  drain- 
age around  Osceola.  It  occurs  to  the  north  and  northeast  of  the  area  studied,  but  notes 
on  those  occurrences  can  not  be  given  at  this  time. 
Plastic  clay  underlies  practically  all  the  coal  seams  of  the  Allegheny  formation,  but.  the 
clay  underlying  the  Lower  Kittanning  coal  appears  to  be  the  most  important,  and  at  the 
time  the  examination  of  this  area  was  made  it  was  the  only  one  being  worked.  It  is  mixed 
with  flint  clay  in  the  making  of  fire  brick. 
Shales  are  very  abundant  in  the  area  of  these  three  quadrangles,  but  in  most  cases  they 
are  very  sandy.  There  are  one  or  two  horizons  of  shale  which  give  promise  of  being  com- 
mercially valuable.  One  of  these  beds  is  low  in  the  Conemaugh,  occurring  just  above  the 
Mahoning  sandstone,  and  is  especially  well  developed  in  northeastern  Indiana  County  and 
southeastern  Jefferson  County.  The  other  shale  deposit  specially  noted  is  between  the 
Upper  and  Lower  Freeport  Coals. 
In  the  following  description  the  localities  at  which  flint  clay  was  noted  are  given,  and 
special  emphasis  is  put  on  deposits  not  being  worked.  In  the  majority  of  cases  the  data 
consisted  simply  of  the  discovery  of  the  flint  clay  in  the  washing  of  the  road,  and  little  or 
a  See  sketch  map,  fig.  11,  p.  272. 
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