608  PEE-CAMBEIAN   GEOLOGY   OF   NOETH   AMEEICA. 
roborated  the  conclusions  reached  in  his  previous  report  on  this 
county  ,a  concerning  the  main  classification  of  the  rocks  of  the  area, 
although  it  is  now  doubtful  if  a  sharp  stratigraphic  distinction  can 
be  drawn  between  series  1  and  2. 
Cushing,39  in  1898,  describes  the  geology  of  Clinton  County,  N.  Y. 
Following  Kemp,  he  gives  the  p  re-Cambrian  succession  as:  (1)  A 
basal  gneissic  series;  (2)  a  series  of  schists  and  gneisses,  with  crys- 
talline limestone;  (3)  igneous  rocks  of  the  gabbro  type,  intrusive  in 
the  first  two  series.  All  of  these  are  overlain  unconformably  by 
Paleozoic  sediments.  This  classification  is  tentative,  and  probably 
simpler  than  the  one  finally  adopted  is  likely  to  be. 
1.  The  bassic  gneissic  series  appears  in  the  western  tier  of  town- 
ships of  the  county,  with  the  exception  of  Clinton,  Peru,  and  Ausable. 
The  gneisses  comprise  several  varieties,  varying  widely  in  texture  and 
composition. 
2.  The  series  of  schists  and  gneisses,  with  crystalline  limestone, 
occurs  only  in  Black  Brook  ToAvnship.  The  limestone  is  coarsely 
crystalline,  and  much  of  it  is  nearly  pure,  but  very  often  it  contains 
a  large  amount  of  green  pyroxene. 
3.  The  gabbros  occur  in  three  areas,  which  are  outliers  of  the  main 
gabbro  massive  of  the  Adirondacks.  One  is  in  Ausable  Township, 
extending  north  and  west  of  Keeseville,  and  is  the  direct  prolongation 
northeastward  of  a  great  gabbro  ridge  which  comes  up  to  Keeseville 
from  the  southwest.  The  second  forms  Rands  Hill,  in  Beekmantown 
and  Altona  townships,  20  miles  north  of  the  first  one.  The  third 
area  forms  the  Catamount  Mountain  ridge,  in  southwestern  Black 
Brook  Township. 
After  the  intrusion  of  the  gabbro  and  prior  to  the  Potsdam  deposi- 
tion the  region  was  subjected  to  intense  metamorphism,  resulting  in 
the  formation  and  granulation  of  the  rocks,  with  or  without  subse- 
quent crystallization. 
Smyth,40  in  1898,  reports  on  the  crystalline  rocks  of  St.  Lawrence 
County,  and  particularly  the  towns  of  De  Peyster,  De  Kalb,  Hermon, 
Edwards,  Canton,  Russell,  Potsdam,  Pierrepont,  and  Parishville, 
together  with  points  reexamined  in  the  towns  of  Gouverneur,  Rossie, 
and  Fowler,  which  were  covered  in  the  examination  made  during 
1893.  The  crystalline  limestones,  for  which,  in  a  previous  report,  the 
name  Oswegatchie  series  was  suggested,  form  belts  stretching  in  a 
northeast-southwest  direction.  Four  belts  comprise  a  large  propor- 
tion of  the  crystalline  limestones  of  the  region  examined.  The  largest, 
the  Gouverneur  belt,  extends  from  Antwerp  to  probably  2  miles  south 
of   Canton   village.     Northwest  of   this  belt  another  extends   from 
a  See  Thirteenth  Ann.  Rept.  New  York  State  Geologist,  for  1893,  published  in  Forty- 
seventh  Ann.  Rept.  New  York  State  Museum  (for  1893),  1894,  pp.  625-666.  Summar- 
ized in  Jour.  Geology,  vol.  6,  1898,  pp.  528-529. 
