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  SANTA 
  MARTA 
  OTL 
  DISTRICT, 
  CAT/IFORNTA. 
  

  

  UPPER 
  DIVISION. 
  

  

  The 
  line 
  of 
  division 
  between 
  the 
  lower 
  and 
  upper 
  portions 
  of 
  the 
  

   Monterey 
  is 
  rather 
  arbitrary, 
  yet 
  if 
  each 
  portion 
  is 
  taken 
  as 
  a 
  whole 
  

   the 
  lithologic 
  distinction 
  is 
  marked, 
  and 
  the 
  separation 
  is 
  made 
  natural 
  

   by 
  the 
  areal 
  limitations 
  of 
  the 
  outcrops 
  of 
  one 
  or 
  the 
  other 
  in 
  various 
  

   places. 
  Where 
  they 
  are 
  in 
  contact 
  a 
  conformity 
  between 
  the 
  two 
  

   halves 
  of 
  the 
  formation 
  is 
  evident 
  and 
  a 
  gradation 
  occurs 
  from 
  the 
  

   porcelaneous 
  and 
  flinty 
  shales 
  of 
  the 
  lower 
  part 
  into 
  the 
  light-colored, 
  

   earthy 
  beds 
  of 
  the 
  upper. 
  Such 
  is 
  the 
  occurrence, 
  for 
  instance, 
  near 
  

   the 
  north 
  edw 
  of 
  the 
  hills 
  4 
  miles 
  west-southwest 
  of 
  the 
  town 
  of 
  

   Lompoc. 
  

  

  The 
  greater 
  part 
  of 
  the 
  upper 
  division 
  is 
  made 
  up 
  of 
  white 
  or 
  light 
  

   chocolate-colored 
  diatomaceous 
  shale, 
  usually 
  of 
  light 
  weight 
  and 
  

   porous, 
  but 
  grading 
  in 
  places 
  into 
  heavier 
  and 
  harder, 
  more 
  compact, 
  

   brittle, 
  porcelain-like 
  shale. 
  The 
  soft 
  shale 
  is 
  extremely 
  fine 
  grained, 
  

   rarely 
  being 
  at 
  all 
  gritty. 
  The 
  bedding 
  is 
  characteristically 
  very 
  thin, 
  

   but 
  where 
  great 
  masses 
  of 
  the 
  soft 
  white 
  shale, 
  which 
  goes 
  by 
  the 
  

   name 
  of 
  diatomaceous 
  earth, 
  occur, 
  lines 
  of 
  bedding 
  are 
  usually 
  

   indistinguishable, 
  except 
  here 
  and 
  there 
  on 
  thin 
  projecting 
  lamina) 
  

   produced 
  by 
  weathering, 
  or 
  on 
  the 
  upper 
  surface 
  of 
  small 
  cavities 
  

   due 
  to 
  the 
  eating 
  out 
  of 
  less 
  resistant 
  patches. 
  PI. 
  IV 
  illustrates 
  two 
  

   characteristic 
  types 
  of 
  the 
  soft 
  unaltered 
  shale. 
  In 
  the 
  upper 
  view 
  

   it 
  is 
  massive, 
  and 
  bedding 
  planes 
  are 
  almost 
  indistinguishable 
  except 
  

   for 
  lines 
  brought 
  into 
  relief 
  by 
  weathering 
  and 
  erosion. 
  In 
  the 
  lower 
  

   view 
  it 
  is 
  slightly 
  more 
  compact 
  and 
  lies 
  in 
  distinct 
  platy 
  layers. 
  

   Major 
  bedding 
  planes 
  from 
  a 
  fraction 
  of 
  an 
  inch 
  to 
  several 
  inches 
  

   apart 
  are 
  distinctly 
  apparent, 
  and 
  there 
  is 
  a 
  further 
  laminated 
  struc- 
  

   ture 
  that 
  enables 
  the 
  shale 
  to 
  be 
  split 
  into 
  plates 
  of 
  extreme 
  thinness. 
  

   An 
  artificial 
  cut 
  through 
  somew 
  r 
  hat 
  disintegrated 
  shale 
  of 
  the 
  upper 
  

   part 
  of 
  the 
  Monterey 
  is 
  shown 
  in 
  PI. 
  VIII, 
  A 
  (p. 
  78). 
  The 
  typical 
  

   unaltered 
  diatomaceous 
  shale 
  is 
  pictured 
  in 
  PI. 
  V, 
  A. 
  The 
  small 
  

   round 
  diatom 
  tests 
  of 
  w 
  T 
  hich 
  it 
  is 
  largely 
  composed 
  are 
  faintly 
  distin- 
  

   guishable 
  with 
  the 
  naked 
  eye 
  in 
  the 
  photograph. 
  In 
  general, 
  both 
  

   the 
  softer 
  and 
  harder 
  varieties 
  of 
  the 
  Monterey 
  shale, 
  owing 
  to 
  their 
  

   siliceous 
  composition, 
  do 
  not 
  give 
  way 
  readily 
  to 
  decomposition 
  or 
  

   weathering. 
  Local 
  chalcedonic 
  lenses 
  are 
  to 
  be 
  found 
  in 
  this 
  series 
  

   roughly 
  following 
  the 
  bedding 
  planes 
  in 
  unaltered 
  shale, 
  as 
  well 
  as 
  

   horizons 
  of 
  hard, 
  porcelaneous, 
  usually 
  much-fractured 
  shale; 
  but 
  

   the 
  latter 
  does 
  not 
  become 
  predominant 
  over 
  the 
  softer 
  shale 
  as 
  it 
  

   does 
  in 
  the 
  lower 
  division. 
  

  

  The 
  white 
  chalklike 
  deposits 
  of 
  this 
  formation 
  are 
  not 
  fully 
  described 
  

   by 
  the 
  use 
  of 
  the 
  word 
  shale 
  in 
  its 
  ordinary 
  sense. 
  Especially 
  in 
  the 
  

   massive 
  deposits, 
  where 
  bedding 
  is 
  not 
  very 
  apparent, 
  it 
  has 
  neither 
  

   in 
  composition 
  nor 
  lamination 
  the 
  character 
  of 
  ordinary 
  shale. 
  But 
  

   this 
  word 
  has 
  come 
  into 
  use 
  in 
  connection 
  with 
  the 
  Monterey 
  for 
  lack 
  

   of 
  any 
  other. 
  The 
  major 
  portion 
  of 
  the 
  formation, 
  however, 
  does 
  

  

  