van  msK.l  EASTERN    UNITED    STATES.  401 
of  the  gneiss  rocks.  Tke  gneiss  is  divided  into  four  principal  belts.  The 
Azoic  formations,  with  trifling  exceptions,  are  stratified.  Usually  they 
are  inclined  a  good  deal,  bnt  the  dip  varies  from  zero  to  90°.  The 
axes  of  the  folds  are  generally  in  a  northeast  and  southwest  direction. 
Some  of  the  rocks  are  so  thin  bedded  as  to  be  schistose,  while  other  por- 
tions are  so  thick  bedded  that  for  long  distances  it  is  almost  impossible 
to  tell  which  way  the  rock  dips.  The  gneiss  is  cut  by  veins  and  dikes 
of  trap  and  granite.  The  Azoic  rocks  of  Trenton  are  much  more  like 
a  true  gneiss  than  those  of  the  Highlands.  The  Potsdam  sandstone, 
the  base  of  the  Paleozoic,  is  found  resting  unconformably  upon  the 
Azoic  gneiss  at  Franklin  furnace  and  at  Green  pond  mountain.  The 
relations  of  the  two  rocks  are  such  as  to  make  it  certain  that  the  sand- 
stone is  later  than  and  unconformably  upon  the  gneiss.  The  Franklin 
furnace  sandstone  is  capped  by  the  blue  magnesian  limestone,  which 
is  equivalent  to  the  calciferous  sandstone  of  the  New  York  reports. 
Cook,137  in  1873,  gives  the  four  Azoic  belts  of  New  Jersey  the  names 
Rainapo,  Passaic,  Musconetcong,  and  Pequest.  In  the  first  and  last  are 
found  numerous  bands  of  interlaminated  limestones,  but  in  the  others 
these  are  not  known  to  occur.  Lithologically  the  greater  portion  of  the 
Azoic  rock  is  syenite-gneiss.  There  is  no  way  of  identifying  it  with  the 
Laurentian  or  Huronian  of  Canada.  As  to  origin  all  are  agreed  that 
these  Azoic  syenitic  gneisses  are  sedimentary.  The  crystalline  lime- 
stone of  the  Ramapo  belt  is  associated  with  the  serpentine,  sometimes 
in  large  quantity. 
Cook,138  in  1883,  states  that  the  rocks  of  the  Highland  include  gran- 
ite, syenite,  several  varieties  of  gneiss,  crystalline  limestone,  and  mag- 
netite, with  rare  species  of  various  schists  and  some  serpentine.  The 
strata  dip  to  the  southeast  at  an  angle  of  from  45°  to  80°,  although  it 
is  often  difficult  to  determine  the  directions  of  strike  and  dip  positively 
because  of  the  massive  character  of  the  rock.  The  ranges  are  regarded 
as  anticlinal  folds  in  general,  although  this  is  not  probably  true  in 
every  case,  and  the  valleys  are  synclinal.  The  massive  syenites,  gran- 
ites, and  traps  are  very  limited  in  quantity,  and  they  are  perhaps  a  part 
of  the  stratified  beds  in  which  stratification  has  been  obliterated, 
although  granite  and  syenite  dikes  are  found  traversing  the  bedded 
gneisses. 
Darton,139  in  1883,  states  that  at  Sparta  granite  cuts  across  the 
limestone  beds  and  may  be  in  true  veins. 
Cook,140  in  1884,  finds  that  besides  the  southeastern  dips  northwest 
dips  occur.  There  is  difficulty  in  separating  the  stratified  from  the  un- 
stratified  rocks,  as  nearly  all  the  glaciated  ledges  look  like  massive 
rocks.  The  relations  of  the  syenite  rocks  and  gneisses  are  not  made 
out  and  it  can  not  be  asserted  which  are  the  older,  but  these  granitoid 
and  syenitic  rocks  are  surrounded  by  stratified  gneisses  and  other  crys- 
talline rocks.  To  the  Highlands  the  term  Archean  is  applied  because 
Bull,  86 26 
