416  CONTRIBUTIONS    TO    ECONOMIC    GEOLOGY,  1904.         [bull.  260. 
Pleistocene. — Pleistocene  deposits  of  till  and  bedded  clays,  sands, 
and  gravels  compose  the  bluffs  which  skirt  the  Strait  of  Juan  de 
Fuca  from  the  eastern  end  of  Clallam  County  westward  to  Fresh- 
water Bay.  Evidences  of  the  same  formation  were  also  found  at 
Gettysburg  and  as  far  west  as  the  mouth  of  the  Pysht  River.  The 
Pleistocene  deposits  are  thickest  in  the  eastern  part  of  the  county, 
gradually  thinning  out,  until  in  the  region  west  of  Gettysburg  they 
form  but  a  comparatively  thin  la}^er  over  the  Oligocene-Miocene 
shales.  Pleistocene  sands  and  gravels  of  varying  thickness  are  also 
found  capping  the  bluffs  which  skirt  the  ocean  along  the  western  end 
of  the  county.  These  Pleistocene  sands  and  gravels  carry  small 
quantities  of  gold,a  platinum,  and  iridosmine  at  several  places  along 
the  coast  from  Point  of  the  Arches  south  as  far  as  the  mouth  of  the 
Quillayute  River. 
GEOLOGIC    STRUCTURE. 
As  indicated  by  the  exposures  along  the  coast,  the  structural  lines 
in  the  region  from  Port  Angeles  to  Gettysburg  average  approxi- 
mately parallel  to  the  trend  of  the  Olympics,  N.  70°  W.-S.  70°  E.; 
those  in  the  Gettysburg-Clallam  Bay  territory  almost  perpendicular 
to  this,  or  a  little  east  of  north,  and  those  in  the  Clallam  Bay-Cape 
Flattery  stretch  N.  30°  W.-S.  30°  E.,  or  again  parallel  with  the 
ridges  which  extend  along  the  coast  in  this  region.  A  syncline,  with 
its  southern  limb  resting  against  the  sandstones  south  of  Lake  Cres- 
cent and  its  northern  one  truncated  by  the  waters  of  the  Strait  of 
Juan  de  Fuca,  is  the  major  structural  feature  of  the  Port  Crescent- 
Gettysburg  region.  The  Freshwater  Bay  coal  field  is  located  in  the 
northern  portion  of  the  trough  of  this  syncline.  A  rather  broad 
sjaicline,  with  its  axis  extending  in  a  northeasterly-southwesterly 
direction,  occupies  most  of  the  territory  between  the  Pysht  River 
and  Clallam  Bay.  The  Clallam  Bay  coal  field  occupies  this  synclinal 
trough.  The  region  between  Clallam  Bay  and  Cape  Flattery  is 
formed  by  a  great  northeast-dipping  monocline,  the  beds  of  which 
appear  to  have  a  total  thickness  of  over  15,000  feet. 
South  of  the  Clallam  Bay-Cape  Flattery  monocline  is  the  western 
extension  of  the  axis  of  the  Olympic  Mountains.  The  structure  inj 
the  region  about  this  line  of  disturbance  is  complex,  but  toward  the 
south  it  becomes  simpler. 
A  great  uplift  followed  by  a  considerable  period  of  erosion  appears 
to  have  taken  place  in  the  Olympic  Peninsula  region  at  or  near  the 
close  of  the  Miocene  epoch,  and  still  another  lesser  one  during  the  late 
Pliocene.     That  these  orogenic  movements  are  still  taking  place  or] 
have  occurred  since  the  deposition  of  the  Pleistocene  is  evidenced  by 
"See  "  Gold  placers  of  the  coast  of  Washington,"  this  bulletin,  pp.  154-157. 
