﻿174 
  Geological 
  Survey 
  of 
  Louisiana 
  [Sect. 
  

  

  Formation 
  of 
  the 
  delta 
  at 
  the 
  foot 
  of 
  Cross 
  lake. 
  — 
  The 
  peculiar 
  

   delta 
  at 
  the 
  foot 
  of 
  Cross 
  lake 
  has 
  already 
  been 
  described 
  under 
  

   Cross 
  lake, 
  and 
  the 
  peculiar 
  fact 
  noticed 
  that, 
  at 
  present, 
  in 
  

   ordinary 
  stages 
  of 
  water 
  the 
  water 
  flows 
  from 
  the 
  delta 
  instead 
  

   of 
  into 
  it. 
  

  

  Under 
  the 
  old 
  raft 
  regime 
  the 
  great 
  amount 
  of 
  water 
  sweeping 
  

   through 
  the 
  pass 
  from 
  Sodo 
  lake 
  into 
  Cross 
  lake 
  must 
  have 
  

   carried 
  with 
  it 
  a 
  great 
  deal 
  of 
  sediment 
  and 
  thus 
  silted 
  up 
  the 
  

   lower 
  end 
  of 
  Cross 
  lake 
  valley. 
  The 
  ancient 
  stream 
  channel 
  was 
  

   entirely 
  filled 
  and 
  the 
  present 
  outlet 
  was 
  thus 
  forced 
  to 
  flow 
  over 
  

   projecting 
  points 
  of 
  the 
  older, 
  harder 
  Eocene 
  material. 
  The 
  delta 
  

   at 
  the 
  head 
  of 
  Bowman's 
  chute 
  is 
  one 
  of 
  the 
  incidents 
  of 
  the 
  silt- 
  

   ing 
  up 
  of 
  the 
  foot 
  of 
  Cross 
  lake.* 
  

  

  Formation 
  of 
  irregular 
  ridges 
  in 
  the 
  bottoms. 
  — 
  Along 
  the 
  river 
  

   front 
  and 
  the 
  banks 
  of 
  bayous, 
  where 
  the 
  sandy 
  front 
  land 
  is 
  well 
  

   developed, 
  the 
  surface 
  is 
  often 
  very 
  irregular 
  as 
  if 
  a 
  great 
  volume 
  

   of 
  water 
  had 
  rushed 
  through 
  in 
  time 
  of 
  flood, 
  cutting 
  a 
  multitude 
  

   of 
  little 
  gullys 
  and 
  leaving 
  little 
  irregularly 
  shaped 
  knolls 
  one 
  to 
  

   two 
  feet 
  high. 
  

  

  They 
  are 
  markedly 
  different 
  from 
  the 
  natural 
  mounds 
  of 
  the 
  

   post-oak 
  or 
  upland 
  flat 
  region 
  ; 
  they 
  are 
  not 
  so 
  uniform 
  in 
  shape, 
  

   so 
  symmetrical, 
  being 
  irregularly 
  oblong 
  rather 
  than 
  circular, 
  

   and, 
  a 
  minor 
  difference, 
  they 
  are 
  not 
  so 
  high. 
  The 
  ridges 
  are 
  

   well 
  developed 
  in 
  Sec. 
  33, 
  20 
  N., 
  14 
  W. 
  

  

  The 
  theory 
  of 
  the 
  current 
  origin 
  of 
  the 
  upland 
  flat 
  topography 
  

   hardly 
  seems 
  probable 
  when 
  these 
  unquestionably 
  current-formed 
  

   mounds 
  are 
  seen. 
  

  

  Old 
  shore 
  line 
  at 
  Cross 
  lake 
  bridge. 
  — 
  Extending 
  along 
  the 
  base 
  

   of 
  the 
  hills 
  and 
  about 
  15 
  feet 
  above 
  the 
  present 
  water 
  level 
  is 
  a 
  

   little 
  wave 
  formed 
  bluff 
  ranging 
  from 
  a 
  few 
  feet 
  to 
  12 
  feet 
  in 
  

   height. 
  It 
  represents 
  the 
  old 
  water 
  level 
  of 
  the 
  lake. 
  As 
  the 
  

   interval 
  between 
  the 
  formation 
  of 
  this 
  lake 
  and 
  the 
  removal 
  of 
  

   the 
  raft 
  was 
  about 
  60 
  years, 
  this 
  bluff 
  represents 
  the 
  effects 
  of 
  

   50 
  years' 
  wave 
  work. 
  It 
  is 
  best 
  developed 
  just 
  east 
  of 
  the 
  south 
  

   end 
  of 
  the 
  railroad 
  bridge. 
  (Plate 
  17.) 
  

  

  *On 
  plate 
  15 
  a 
  delta 
  is 
  shown 
  only 
  at 
  the 
  head 
  of 
  Bowman's 
  chute. 
  This 
  

   was 
  the 
  only 
  portion 
  of 
  the 
  foot 
  of 
  the 
  lake 
  carefully 
  examined. 
  The 
  other 
  

   channels 
  should 
  show 
  the 
  same 
  peculiarity. 
  

  

  