418  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,    1905. 
Cretaceous. — The  Cretaceous  is  the  oldest  of  the  Gulf  embayment  deposits.  It  is  a  sei 
of  interstratified  sandstones  and  clays  in  the  lower  part  and  limestones,  marls,  sandstones 
and  clays  in  the  upper  part.  It  occupies  a  narrow  area  on  the  east  adjacent  to  Tennesse 
River.  The  area  is  widest  to  the  south,  where  its  width  is  about  31  miles.  North  of  this i 
gradually  narrows,  and  at  Paducah,  Ky.,  it  is  not  more  than  8  miles  wide. 
Tertiary. — Above  the  Cretaceous  are  the  stratified  sands,  clays,  and  limestones  of  I 
Tertiary,  with  a  total  thickness  of  2,000  feet  or  more.     The  lowest  member  of  the  Tertiar; 
an  impure  limestone  and  marl  of  Midway  age,  which  outcrops  in  the  southeastern  sectio: 
i  lie  Tertiary  area  near  the  Mississippi  line.     North  of  this  the  marine  deposits  disap 
or  are  covered  so  deeply  by  later  deposits  that  they  do  not  come  to  the  surface.     Im 
diately  above  the  limestone  noted  above  is  the    'orters  Creek,  a  very  persistent   body 
dark,  slaty,  nonfossiliferous  clay  which  occupies  a  belt  2  to  0  miles  wide  and  extends  acr 
Tennessee  and  Kentucky  in  a  direction  roughly  parallel  to  Tennessee  River.     It  forms  tl 
most  easily  recognized  and  important  geologic  horizon  in  the  entire  area.      Except  in  tl 
extreme1  south  it  forms  the  division  between  the  Cretaceous  and  the  remaining  Tertiary 
makes  it  possible  to  determine  the  age  of  the  rich  clay  deposits  of  the  district. 
The  Tertiary  strata  above  the  Porters  Creek  beds  consist  of  interstratified  sands,  clays, 
and  lignites.     The  sands  predominate  in  the  lower  portion.     The  line  deposits  of  white,  «| 
stoneware,  and  hall  clays  occur  in  these  stratified  Tertiary  sands  immediately  overlying  the 
Porters  ('reek  clay. 
Quaternary. — Over  the  entire  Tertiary  and  Cretaceous  areas  is  a  thin  veneer  of  Lafayette 
and  loess  which  rests  unconformably  on  the  older  strata.     On  account  of  these  overlapping   ' 
formations  it  is  often  ditliculi  to  obtain  good  exposures  of  the  Tertiary  and  Cretaceous  and   I 
the  exact  division  line  between  them  is  in  places  impossible  to  determine.     These  surficial    : 
deposits  are  thickest  on  the  bluffs  adjacent  to  Mississippi  River,  where  they  reach  a  maxi 
mum  thickness  of  100  feet.     They  gradually  thin  to  the  easi  and  at  Tennessee  River  t 
maximum  thickness  is  less  than  25  feet  and  they  are  often  wanting. 
The  large  rivers  and  many  of  the  streams  in  the  interior  have  extensive  bottoms  win 
are  covered  with  recent  deposits. 
DISTRIBUTION   OF    CLAY   DEPOSITS. 
CRETACEOUS   (LAYS. 
Clays  belonging  to  the  Cretaceous  in  this  area  are  easily  fusible  and  are  usually  of  a  dark 
or  bluish  color.     They  occur  interbedded  with  sharp,  fine-grained,  micaceous  sands. 
Few  of  the  Cretaceous  clays  have  been  developed.  This  is  partially  due  to  the  fad  that 
the  deposits  are  generally  too  far  removed  from  transportation  facilities  to  be  of  value. 
KENTUCKY. 
Pottertown,  Calloway  County.  The  Pottertown  stoneware  plant  is  located  6\  miles  east 
of  Murray,  at  Pottertown.  Common  jugware,  churns,  and  crocks  are  the  principal  piod- 
ucts.  Only  one  turner  is  now  employed,  who  turns  about  50,000  gallons  yearly.  A  sn  all 
updraft  kiln  is  used  for  burning  ware.  The  ware  burns  to  a  beautiful  cream  color  on  glaziJ 
with  Albany  slip.  The  green  ware  can  be  put  in  hot  sunshine  after  twro  days  of  drying  in 
the  shade. 
The  clay  comes  from  a  pit  200  yards  east  of  the  former  post-office.  It  occurs  in  irregulal 
lenses  in  the  Cretaceous  and  is  overlain  by  3  to  6  feet  of  Lafayette.  The  clay  varies  in 
color  from  a  cream  white  to  a  gray,  purple,  and  black.  It  is  underlain  by  a  fme-graincd, 
micaceous,  variegated  sand  and  is  not  used  as  it  comes  from  the  pit,  but  is  mixed  with  the 
underlying  sand  in  the  proportion  of  five  parts  of  clay  to  one  part  of  sand.  The  principal 
market  for  the  ware  is  at  Murray  and  the  small  stores  and  farms  throughout  the  country. 
