634  PRE-CAMBRTAN    GEOLOGY    OF    NORTH   AMERICA. 
Tarrytown  and  West  Point  quadrangles  in  the  Highlands  of  New 
York.     The  first  view  is  presented  by  Spencer  as  follows: 
View  of  A.  ('.  Spencer  and  associates. — In  southeastern  New  York 
is  a  great  series  of  crystalline  rocks  which  are  now  generally  re- 
garded as  of  pre-Cambrian  age.  These  rocks  include  granites  and 
granite  gneisses,  syenites,  evenly  banded  schistose  gneisses,  bedlike 
bodies  of  magnetic  iron  ore,  and  interlaminated  masses  of  crystalline 
limestone.  East  of  the  Hudson  River  they  are  found  in  New  York, 
Westchester,  Putnam,  and  Dutchess  counties,  whence  they  extend 
into  Connecticut,  and  west  of  the  river  in  Orange  and  Rockland 
counties,  extending  thence  southwest  into  New  Jersey.  A  coarse 
hornblende  granite  forming  the  central  mass  of  the  Highlands  of  the 
Hudson  is  believed  by  Merrill  to  be  the  oldest  formation  of  the  com- 
plex, but  later  work  by  Eckel  tends  to  show  that  relations  of  super- 
position can  not  be  recognized.  This  suggestion  corresponds  with 
recent  work  by  Bayley;  and  Spencer  in  New  Jersey,  where  the  gneisses 
are  regarded  as  mainly  eruptive.  On  the  flanks  of  this  mass  of 
granite  are  banded  biotitic  and  hornblendic  gneisses  containing  nu- 
merous beds  of  magnetite.  These  gneisses  are  found,  both  north  and 
south  of  the  Highlands  of  the  Hudson,  to  be  overlain  unconform- 
ably  by  Paleozoic  sediments.  The  Fordham  gneiss  of  Westchester 
and  New  York  counties  is  also  overlain  unconformably  by  Paleozoic 
formations,  but  it  lias  not  been  correlated  as  yet  with  any  part  of  the 
complex  in  the  Highlands  of  the  Hudson. 
Infolded  with  the  gneisses  along  northeast-southwest  axes  are 
highly  metamorphosed  and  crystalline  Paleozoics.  The  folds  are 
closely  compressed — often  overturned.  The  general  dip  of  schistos- 
ity  is  toward  the  southeast,  though  faulting  and  transverse  folding 
cause  local  variations.  The  crystalline  sediments  of  southeastern 
New  York,  including  the  "  Manhattan  group  "  and  the  "  Taconics," 
are  now  regarded  mainly  as  the  metamorphosed  equivalents  of  the 
Cambrian  and  Ordovician  formations  which  occur  in  an  unaltered 
condition  north  of  the  Highlands.  With  them  are  associated  in- 
trusive rocks  and  the  pre-Cambrian  Fordham  gneiss. 
View  of  C.  P.  Berkey. — Berkey  finds  in  the  basement  gneiss  group, 
northward  from  New  York,  limestones  and  other  sediments  with  such 
relations  to  the  gneiss  as  to  lead  him  to  correlate  the  group  with  the 
Grenville  series  of  the  Adirondack^  and  southern  Ontario.  This 
correlation  he  believes  also  to  extend  southward  into  the  New  York 
City  quadrangle.  A  part  of  the  supposed  Paleozoic  rocks  called  the 
"  Inwood "  limestone  and  "  Manhattan  "  schist,  infolded  with  the 
basal  series,  he  finds  to  be  pre-Cambrian  and  to  be  separated  by  an 
unconformity  from  the  Poughquag  quartzite  above,  representing  the 
base  of  the  Paleozoic,  and  by  another  unconformity  from  the  base- 
ment gneiss  series  below.     He  says  that  if  these  rocks  are  truly  con- 
