﻿II] 
  

  

  General 
  Geology 
  : 
  Quaternary 
  

  

  109 
  

  

  TABI,E 
  of 
  LOUISIANA 
  QUATERNARY 
  FORMATIONS 
  

  

  River 
  Development 
  

  

  Costal 
  Development 
  

  

  Alluvium 
  

  

  Coastal 
  Marshes 
  

   Biloxi 
  Sands 
  

  

  Yellow 
  Loam 
  Lcess 
  

   Fluviatile 
  Port 
  Hudson 
  

  

  

  Colum 
  

   bia 
  

  

  f 
  Chocolate 
  Colored 
  Loam 
  ^ 
  ti-i 
  

   I 
  Yellow 
  Loam 
  ■ 
  ^^^oxi 
  

  

  or 
  Old 
  Alluvium 
  [ 
  cMc-re^f^s 
  "I 
  Ponchartrain 
  Clays 
  or 
  

  

  .1 
  firoirf^l 
  (,iViCVjeej 
  I 
  Mar^tiP 
  Pr.rt 
  Mi'irlt 
  

  

  Basal 
  Gravel 
  

  

  

  Marine 
  Port 
  Hudson 
  

   [Coast 
  Pliocene 
  (Hilgard) 
  

  

  Sands 
  

   (John 
  

   son) 
  

  

  DEVELOPMENT 
  AND 
  CHARACTERISTICS 
  OF 
  I.OUIS- 
  

   lANA 
  QUATERNARY 
  FORMATION 
  

  

  MANNER 
  OF 
  FORMATION 
  

  

  Natural 
  periods 
  hi 
  the 
  Quateryiary 
  of 
  Louisiana. 
  — 
  The 
  history 
  

   of 
  the 
  Eouisiana 
  Quaternary 
  seems 
  to 
  be 
  divisible 
  into 
  three 
  

   parts 
  : 
  a 
  long 
  period 
  of 
  deposition, 
  with 
  varying 
  conditions 
  in 
  

   altitude 
  and 
  consequent 
  differences 
  in 
  the 
  character 
  of 
  sediment 
  

   deposited 
  ; 
  a 
  period 
  of 
  erosion 
  ; 
  and 
  the 
  present, 
  comparatively 
  

   recent 
  period 
  of 
  deposition. 
  

  

  First 
  period 
  of 
  subsidence. 
  — 
  In 
  the 
  beginning 
  of 
  this 
  period 
  the 
  

   land 
  must 
  have 
  stood 
  over 
  248 
  feet* 
  higher 
  in 
  the 
  northern 
  part 
  

   of 
  Eousiana 
  than 
  it 
  does 
  to-day. 
  In 
  the 
  valley 
  where 
  the 
  stream 
  

   was 
  sufficiently 
  rapid, 
  portions 
  of 
  the 
  Eafayette 
  gravels 
  were 
  

   re-deposited 
  or 
  other 
  gravel 
  brought 
  down 
  by 
  the 
  river 
  from 
  the 
  

   north. 
  The 
  deposition 
  of 
  gravel 
  would 
  naturally 
  be 
  greatest 
  in 
  the 
  

   upper 
  part 
  of 
  the 
  valley 
  while 
  nearer 
  the 
  coast 
  the 
  material 
  

   would 
  be 
  finer. 
  Along 
  the 
  coast, 
  deposits 
  of 
  clay 
  and 
  sand 
  would 
  

   be 
  formed, 
  which 
  near 
  the 
  mouth 
  of 
  the 
  river 
  they 
  would 
  contain 
  

   Rajigia 
  and 
  other 
  brackish 
  water 
  molluscs, 
  while 
  at 
  a 
  distance 
  

   from 
  the 
  main 
  outlet 
  of 
  the 
  river 
  the 
  deposits 
  would 
  contain 
  

   recent 
  marine 
  species. 
  As 
  the 
  subsidence 
  progressed 
  the 
  deposi- 
  

  

  * 
  The 
  depth 
  of 
  the 
  Quaternary 
  deposits 
  at 
  Lake 
  Providence. 
  — 
  Hilgard 
  and 
  

   Hopkins, 
  Report 
  on 
  Borings 
  between 
  Memphis 
  and 
  Vicksburg, 
  48th 
  Cong., 
  

   1st 
  Sess., 
  House 
  Ex. 
  Doc, 
  vol. 
  19, 
  1884, 
  p. 
  481. 
  

  

  