﻿236 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  194 
  3 
  

  

  the 
  instrument 
  hits 
  the 
  bottom. 
  More 
  uniform 
  performance 
  has 
  been 
  

   secured 
  with 
  this 
  coring 
  tube 
  in 
  deep 
  water 
  than 
  with 
  any 
  other 
  yet 
  

   devised, 
  and 
  cores 
  up 
  to 
  10 
  feet 
  in 
  length 
  are 
  frequently 
  taken, 
  al- 
  

   though 
  occasionally 
  greater 
  lengths 
  have 
  been 
  attained 
  by 
  tubes 
  

   which 
  are 
  dropped 
  at 
  high 
  velocity. 
  The 
  extra 
  6 
  or 
  7 
  feet 
  of 
  core 
  

   obtained 
  by 
  these 
  newer 
  instruments 
  may 
  not 
  seem 
  to 
  be 
  of 
  much 
  

   significance 
  as 
  compared 
  to 
  the 
  probable 
  total 
  thickness 
  of 
  the 
  de- 
  

   posit, 
  but 
  it 
  must 
  be 
  remembered 
  that 
  the 
  rate 
  of 
  deposition 
  de- 
  

   creases 
  as 
  one 
  goes 
  beyond 
  the 
  continental 
  slopes 
  into 
  the 
  ocean 
  basins. 
  

   Accordingly, 
  10 
  feet 
  of 
  sediment 
  may 
  represent 
  a 
  considerable 
  inter- 
  

   val 
  of 
  time. 
  Indeed, 
  in 
  a 
  series 
  of 
  cores 
  taken 
  by 
  Piggott 
  across 
  the 
  

   Atlantic 
  basin, 
  and 
  worked 
  up 
  by 
  the 
  United 
  States 
  Geological 
  Sur- 
  

   vey, 
  four 
  warm 
  and 
  four 
  cold 
  alterations 
  of 
  climate 
  are 
  represented 
  

   (Geophysical 
  Exploration, 
  1937, 
  Bradley 
  et 
  al., 
  pp. 
  41-46). 
  

  

  Using 
  this 
  same 
  instrument, 
  numerous 
  cores 
  have 
  been 
  taken 
  by 
  the 
  

   Atlantis 
  in 
  and 
  around 
  the 
  east 
  coast 
  submarine 
  canyons, 
  along 
  the 
  

   continental 
  slope, 
  and 
  for 
  some 
  distance 
  out 
  into 
  the 
  Atlantic 
  basin. 
  

   In 
  these, 
  one 
  or 
  more 
  climatic 
  cycles 
  are 
  usually 
  found. 
  The 
  pres- 
  

   ent-day 
  warm-water 
  fauna 
  from 
  the 
  tops 
  of 
  the 
  cores 
  occurs 
  in 
  a 
  

   green 
  silt 
  which 
  is 
  being 
  deposited 
  under 
  modern 
  marine 
  conditions. 
  

   The 
  cold-water 
  fauna 
  from 
  the 
  bottom 
  sections 
  is 
  found 
  in 
  a 
  com- 
  

   pact, 
  varicolored 
  clay. 
  Such 
  fine-grained, 
  terrigenous 
  material 
  is 
  not 
  

   being 
  deposited 
  on 
  the 
  surface 
  of 
  the 
  present-day 
  bottom 
  in 
  this 
  area, 
  

   on 
  the 
  shelf, 
  slope, 
  or 
  even 
  in 
  the 
  westerly 
  part 
  of 
  the 
  Atlantic 
  basin, 
  

   as 
  practically 
  all 
  river-borne 
  sediment 
  is 
  now 
  effectively 
  trapped 
  in 
  

   the 
  bays 
  and 
  estuaries 
  which 
  today 
  border 
  the 
  entire 
  eastern 
  sea- 
  

   board. 
  The 
  clay 
  in 
  question 
  evidently 
  dates 
  from 
  the 
  last 
  glacial 
  

   stage 
  of 
  the 
  Wisconsin 
  when, 
  because 
  of 
  the 
  lowered 
  sea 
  level, 
  the 
  

   rivers 
  were 
  able 
  to 
  cross 
  the 
  shelf 
  and 
  dump 
  their 
  loads 
  directly 
  on 
  

   the 
  steep 
  continental 
  slope. 
  

  

  The 
  possibilities, 
  therefore, 
  of 
  being 
  able 
  to 
  trace 
  the 
  history 
  of 
  

   Pleistocene 
  sedimentation 
  in 
  the 
  Atlantic 
  basin 
  and 
  on 
  the 
  continental 
  

   slope 
  by 
  the 
  continued 
  use 
  of 
  the 
  coring 
  tube 
  are 
  very 
  good. 
  It 
  is 
  

   even 
  possible 
  that 
  from 
  this 
  source 
  some 
  light 
  may 
  be 
  thrown 
  on 
  the 
  

   far 
  from 
  settled 
  problem 
  of 
  the 
  origin 
  of 
  submarine 
  canyons. 
  This 
  

   investigation 
  is 
  already 
  under 
  way 
  at 
  the 
  Woods 
  Hole 
  Oceanographic 
  

   Institution, 
  and 
  similar 
  work 
  is 
  in 
  progress 
  at 
  the 
  Scripps 
  Institution 
  

   of 
  Oceanography 
  at 
  La 
  Jolla. 
  At 
  the 
  latter 
  institution 
  an 
  extensive 
  

   program 
  for 
  submarine 
  geology 
  is 
  being 
  carried 
  out 
  under 
  the 
  direc- 
  

   tion 
  of 
  Dr. 
  F. 
  P. 
  Shepard, 
  which 
  is, 
  in 
  part, 
  financed 
  by 
  a 
  grant 
  from 
  

   the 
  Penrose 
  Bequest 
  of 
  the 
  Geological 
  Society 
  of 
  America. 
  

  

  Cores 
  have 
  one 
  limitation 
  which 
  is 
  only 
  just 
  beginning 
  to 
  be 
  recog- 
  

   nized. 
  The 
  deeper 
  the 
  tube 
  penetrates 
  the 
  sediment 
  the 
  greater 
  be- 
  

   comes 
  the 
  friction 
  on 
  the 
  inside 
  walls 
  of 
  the 
  tube. 
  Dr. 
  M. 
  Juul 
  

  

  