306  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,   L906,   PART    r. 
of  the  bell  lying  west  of  Macon.  At  its  contact  with  the  crystalline 
rocks,  which  are  schist  and  gneisses,  the  formation  in  this  region  is 
composed  of  subangular  quartz  and  feldspar  gravel;  farther  south 
these  are  replaced  by  gray  and  pink  micaceous  sand  containing  irregu- 
lar beds  of  kaolin  and  fire  clay.  The  kaolin  beds  are  not  so  thick  here 
as  in  the  eastern  belt,  and  individual  beds  are  not  so  extensive.  No  I 
kaolins  of  great  value  have  been  discovered  west  of  Butler.  The 
Tuscaloosa  in  the  vicinity  of  Geneva,  near  Columbus,  differs  in  appear- 
ance from  the  formation  as  exposed  in  any  other  part  of  the  State. 
Here  it  is  composed  largely  of  indurated  material  and  consists  of 
alternating  layer-  of  indurated  clay  and  sandstone.  I 'lie  clay  layers 
here  are  thin,  dark  colored,  and  iron  stained.  The  Tuscaloosa  in 
western  Georgia  is  overlain  by  Upper  Cretaceous  strata,  whereas  in 
eastern  Georgia  it  is  overlain  by  sand  and  clays  of  Tertiary  age.  It 
is  very  difficult  to  distinguish  the  Tuscaloosa  from  the  clayey  sands 
of  the  I  upper  <  Jretaceous. 
Upper  Cretaceous.  The  Upper  Cretaceous  strata  in  Georgia  are 
exposed  in  a  belt,  1")  to  25  miles  in  width,  which  extends  westward 
from  Ocmulgee  River  to  Chattahoochee  River.  No  Upper  (Yet  aceous 
strata  are  known  to  be  exposed  east  of  Ocmulgee  River.  The  strata 
consist  of  unconsolidated  sands  and  gravel,  marls,  clays,  and  lime- 
stone. The  marls  and  limestone  are  besl  developed  along  Chatta- 
hoochee River,  where  the  greatest  thickness  of  strata  is  exposed. 
East  of  Chattahoochee  River  the  formation  is  predominantly  sand 
containing  lenticular  layers  and  irregular  and  uonpersistenl  beds  of 
clay,  although  one  of  the  marl  beds  can  be  t  raced  from  Chatl  ahoochee 
River  eastward  to  a  point  1  miles  east  of  Marshallville,  in  Houston 
County.  The  sands  are  ferriferous  and  contain  thin  layers  and  hollow 
nodules  of  sHiceous  limonite.  At  some  localities,  however,  there  are 
great  thicknesses  of  pure  white,  extremely  fine,  loose  sand.  No  clays 
thai  are  likel\  to  be  of  value  have  been  discovered  in  the  formation 
except  iii  Houston  County,  where  white  clays  occur  in  great  quantity. 
DESCRIPTIONS   OF   CLAY   DEPOSITS   BY   LOCALITIES. 
The  following  descriptions  do  not  by  any  means  include  all  the 
localities  where  good  clays  are  exposed.  The  aim  is  to  describe  the 
clay  at  the  principal  local  it  ies,  in  order  to  give  some  idea  of  its  extent, 
quality,  and  accessibility. 
ni:v    BRANCH. 
Dry  Branch  is  on  the  Macon,  Dublin  and  Savannah  Railroad,  9 
miles  southeast  of  Macon.  Here  the  most  extensive  and  purest  beds 
of  clay  occur  and  here  clay  mining  is  most  actively  carried  on.  The 
clay  mined  is  largely  a  soft  kaolin,  suitable  for  the  paper  and  pottery 
trade.     Four  companies  are  at  present  engaged  in  active  mining, 
