﻿I 
  

  

  1 
  08 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  After 
  his 
  examination 
  of 
  Port 
  Hudson 
  and 
  his 
  trip 
  through 
  

   southern 
  Louisiana 
  he 
  recognized 
  over 
  the 
  whole 
  area 
  the 
  equiva- 
  

   lents 
  of 
  his 
  Coast 
  Pliocene, 
  and 
  proposed 
  for 
  the 
  whole 
  the 
  name 
  

   Port 
  Hudson 
  group.* 
  The 
  layer 
  of 
  blue 
  clayf 
  which 
  the 
  labors 
  

   of 
  Humphreys 
  and 
  Abbott 
  had 
  revealed 
  to 
  be 
  very 
  widespread 
  

   in 
  the 
  bottoms, 
  and 
  which 
  they 
  referred 
  to 
  a 
  number 
  of 
  different 
  

   geological 
  horizons, 
  from 
  the 
  Cretaceous 
  up, 
  Hilgard 
  referred 
  to 
  

   the 
  Port 
  Hudson. 
  J 
  He 
  came 
  to 
  the 
  conclusion 
  that 
  the 
  present 
  

   deposits 
  of 
  the 
  river 
  are 
  of 
  inconsiderable 
  thickness 
  ; 
  a 
  view 
  

   which 
  he 
  has 
  maintained 
  in 
  all 
  his 
  subsequent 
  writings. 
  

  

  Johnsoyi. 
  — 
  Investigations 
  by 
  Mr. 
  L. 
  C. 
  Johnson 
  in 
  1890, 
  in 
  

   southern 
  Mississippi 
  and 
  in 
  the 
  region 
  north 
  of 
  Lake 
  Pontchar- 
  

   train, 
  in 
  the 
  coastal 
  phase 
  of 
  the 
  Port 
  Hudson, 
  led 
  him 
  to 
  pro- 
  

   pose 
  for 
  it 
  the 
  name 
  Pontchartrain 
  clays. 
  § 
  At 
  the 
  same 
  time 
  he 
  

   proposed 
  the 
  name 
  Biloxi 
  sands 
  for 
  the 
  more 
  recent 
  coastal 
  

   formations. 
  The 
  difficulty 
  in 
  distinguishing 
  between 
  the 
  two 
  

   beds, 
  which 
  were 
  formed 
  under 
  very 
  similar 
  conditions, 
  led 
  to 
  

   the 
  extension 
  of 
  the 
  meaning 
  of 
  Biloxi 
  sands 
  to 
  include 
  the 
  

   Pontchartrain 
  clays. 
  || 
  

  

  McGee. 
  — 
  In 
  his 
  correlation 
  of 
  the 
  coastal 
  deposits 
  McGee 
  

   includes 
  all 
  the 
  Quaternary 
  deposits 
  in 
  Louisiana, 
  except 
  the 
  

   most 
  recent 
  alluvium, 
  under 
  the 
  Columbia 
  formation.^ 
  He 
  

   restricts 
  the 
  Orange 
  Sand, 
  as 
  used 
  by 
  Safford 
  in 
  1888, 
  ft 
  to 
  the 
  

   basal 
  portions 
  of 
  the 
  Yellew 
  Loam. 
  

  

  *Am. 
  Jour. 
  Sci., 
  2d 
  series, 
  vol. 
  48. 
  p. 
  332, 
  1869. 
  

  

  t 
  Hydraulics 
  and 
  Physics 
  of 
  the 
  Mississippi 
  River, 
  p. 
  99. 
  

  

  X 
  Am. 
  Jour. 
  Sci., 
  3d 
  series, 
  vol. 
  47, 
  p. 
  79 
  ; 
  also 
  Am. 
  Jour. 
  Sci., 
  3d 
  series, 
  

   vol. 
  2, 
  pp. 
  391-404; 
  Am. 
  Assoc. 
  Adv. 
  Sci., 
  Proc.,vol. 
  20, 
  pp. 
  222-236. 
  

  

  \ 
  Bull. 
  Geol. 
  Soc. 
  Am., 
  vol. 
  2, 
  pp 
  20-25, 
  1890. 
  

  

  II 
  Geol. 
  Surv. 
  Ala., 
  1894, 
  p. 
  41. 
  

  

  11 
  The 
  Lafayette 
  formation 
  by 
  W 
  J 
  McGee, 
  12th 
  Annual 
  Report 
  U.S. 
  

   Geol. 
  Surv., 
  Part 
  I, 
  p. 
  392. 
  

  

  ff 
  Agricultural 
  and 
  Geological 
  Map 
  of 
  Tennessee 
  (J. 
  M. 
  Safford, 
  State 
  

   Geologist), 
  1888. 
  

  

  