866  PRE-CAMBRIAN    GEOLOGY    OF    NORTH    AMERICA. 
Hornblende  and  epidote  schists,  as  well  as  quartzite,  occur  in  the 
same  formation,  so  that  the  East  on  schist  is  believed  to  contain  rocks 
of  both  igneous  and  sedimentary  origin.  These  rocks  unconformably 
underlie  metamorphic  formations  to  which  a  Carboniferous  age  is 
provisionally  assigned. 
Smith  (G.  O.)  and  Calkins,157  in  1904,  describe  the  granitoid 
gneiss  and  schist  of  the  Columbia  River  gorge  above  Wenatchee, 
which  appear  older  than  the  supposedly  Carboniferous  strata  in  the 
vicinity  of  the  international  boundary.  Along  the  boundary  pre- 
Cretaceous  sedimentaries  and  volcanics  were  encountered  on  the  west 
slope  of  the  Cascades,  but  no  evidence  is  cited  to  show  that  these 
metamorphic  rocks  are  pre-Paleozoic.  In  the  lower  Skagit  Valley  a 
series  of  slates,  chlorite  and  glaucophane  schists,  with  ferruginous 
quartzites  and  jaspers,  is  described,  but  no  definite  age  is  assigned 
to  the  series. 
Ransome,132  in  1906,  states  that  in  the  course  of  a  reconnaissance 
covering  a  strip  about  10  miles  Avide  along  the  south  side  of  the 
international  boundary  in  1901  he  found  the  northeast  corner  of  the 
State,  east  of  Pend  Oreille  River  and  as  far  south  as  lone,  to  be 
occupied  by  complexly  folded,  dark  siliceous  slates  and  fine-grained 
crystalline  schists,  including  numerous  bands*  of  schistose  limestone 
and  occasional  beds  of  quartzite.  These  rocks  are  unfossiliferous,  as 
far  as  known,  and  seem  to  be  continuous  with  the  schists  and  gneisses 
of  northwestern  Idaho,  which,  as  stated  on  page  851,  are  probably 
pre-Cambrian. 
Along  Pend  Oreille  River  from  lone  to  the  international  bound- 
ary are  thick  masses  of  limestone  which,  while  intimately  associated 
with  the  schistose  rocks,  may  possibly  be  infolded  younger  beds. 
From  Pend  Oreille  River  to  the  Columbia  the  prevailing  rocks 
are  dark  siliceous  slates,  fine-grained  fissile  schists,  and  schistose  lime- 
stone. These  highly  compressed  rocks  are  tentatively  assigned  to  the 
Carboniferous  by  Daly,a  but  fossils  are  lacking  and  the  series  passes 
with  no  apparent  break  into  the  more  conspicuously  crystalline  and 
gneissic  complex  of  northwestern  Idaho.  Considerable  masses  of 
gneissic  granite  are  exposed  west  of  lone  and  on  Deep  Creek  a  few 
miles  east  of  Northport.  The  presence  of  these  masses  suggests  that 
the  schistose  rocks  between  Pend  Oreille  and  Columbia  rivers  may 
be  much  older  than  the  Carboniferous. 
West  of  Columbia  River  the  slaty  schists  are  gradually  succeeded 
by  closely  compressed  conglomerates  and  greenstone  (andesitic)  brec- 
cias with  much  greenish  tuffaceous  slate  and  some  clay  slate.  These 
rocks,  which  are  cut  by  numerous  dikes  of  dioritic  porphyry,  may  be 
younger  than  the  Algonkian.     They  are,  however,  so  closely  inter- 
a  Summary  Rept.  Geol.  Survey  Canada  for  1902,  1903,  p.  143. 
