CLAYS  OF  THE  PENOBSCOT  BAY  REGION,  MAINE. 
By  Edson  S.  Bastin. 
Area  corned  by  field  studies. — The  field  observations  od  which  this  paper  is  based  were 
confined  to  the  coastal  regitin  and  extended  from  Bluehill  Bay  on  the  east  to  Pemaquid 
Point  "ii  the  west,  taking  in  Dearly  all  of  the  islands  which  border  this  pari  of  the  main- 
land. That  portion  lying  to  the  east  of  Thomaston  was  studied  during  the  summers  of 
1904  and  1905,  while  making  a  detailed  geological  study  for  folio  publication  of  the  Penob- 
scot Bay  and  Rockland  quadrangles.  The  coast  from  Thomaston  to  Pemaquid  Point  was 
studied  hastily  during  a  reconnaissance  trip  in  the  autumn  of  1905,  made  principally  fol 
the  purpose  of  tracing  the  limits  of  certain  granite  areas. 
Distribution.  The  days  of  this  districl  are  distributed  over  the  lowlands  of  the  coastal 
region  as  a  nearly  horizontal  sheel  of  varying  thickness.  So  uniform  is  the  material  in 
grain  and  color  that  only  here  and  there  can  a  division  into  distinct  beds  be  recognized. 
Vertically  they  are  confined  mainly  to  the  interval  between  sea  level  and  the  125-foot 
lev],  and  while  tk  >t  all  the  land  within  this  interval  is  occupied  by  these  deposits  it  is 
prol  abl\  safe  t<i  say  that  they  cover  fully  half  of  such  territory.  Areally  they  find  their 
broadesl  distribution  and  penetrate  farthest  inland  along  the  rivers  and  tidal  estuaries, 
while   along  certain    bold   parts  of   the  coast    they  may   be  entireU    absent.      Along    IVnob- 
seot  River  they  are  well  developed  as  far  up  as  Bangor  and  along  St.  George  River  they 
penetrate  inland  a  distance  of  20  miles  to  the  villages  of  Thomaston,  Wan-en.  and  beyond. 
General  <■/>/>( <intnc<  of  flu  clays.  The  clays  here  considered,  which  are  the  only  com- 
mercially important  clays  of  the  region,  are  yellowish  gray  to  blue-gray  in  color,  the  former 
being  by  far  the  more  common.  For  the  most  pari  they  are  exceedingly  fine  grained  and 
except  in  a  few  localities  are  very  five  from  sand  or  pebbles. 
Recognition  in  thefield.  The  clay-  are  readily  recognized  where  they  have  been  exposed 
by  the  waves  or  streams  and  where  they  have  been  uncovered  in  excavations.  Excellent 
natural  exposures  occur  a!  Sherman  Cove,  near  Camden,  along  the  north  side  of  Rockland 
1  [arbor,  along  St.  ( reorge  River  near  Thomaston,  and  at  many  other  localities  on  the  shore, 
where  they  have  been  cut  into  by  the  waves  and  now  stand  up  as  benches  or  terraces 
rising  10  to  25  feet  above  the  beach.  Artificial  exposures  are  common  in  the  railroad 
cuts  and  in  the  cuts  and  ditches  of  many  of  the  wagon  roads.  One  of  the  besl  exposures 
is  at  the  brickyard  at  Thomaston,  and  other  good  exposures  occur  at  the  quarries  west  of 
Rockland,  where  the  clays  must  be  stripped  oil'  before  the  limestone  can  be  reached.  Even 
where  sections  can  not  be  found,  the  presence  or  absence  of  the  clays  may  usually  be  recog- 
nized from  the  general  appearance  of  the  land  surface.  Extensive  flats  or  gently  sloping 
plains  occupying  the  lowlands  and  free  from  surface  bowlders  are  nearly  always  found  to 
be  built  up  of  these  clays.  When  roads  traversing  these  flats  have  not  been  graded  with 
material-  brought  in  from  other  localities,  the  clayey  character  is  revealed  by  the  fine  light- 
gray  dusl  which  develops  in  dry  weather,  the  sticky  gray  mud  which  forms  after  a  heavy 
rain,  and  the  absence  of  pebbles  or  cobbles. 
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