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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1943 
  

  

  proach 
  has 
  been 
  made 
  to 
  an 
  understanding 
  of 
  the 
  factors 
  controlling 
  

   the 
  transportation 
  and 
  deposition 
  of 
  sediments 
  by 
  means 
  of 
  traps 
  

   placed 
  on 
  the 
  bottom, 
  although 
  this 
  work 
  is 
  still 
  in 
  its 
  early 
  stages. 
  

  

  Additional 
  regional 
  studies 
  have 
  been 
  carried 
  out 
  in 
  the 
  Baltic 
  and 
  

   neighboring 
  waters 
  by 
  the 
  Thalassological 
  Institute 
  at 
  Helsinki 
  and 
  by 
  

   the 
  marine 
  laboratory 
  of 
  the 
  University 
  of 
  Kiel; 
  these 
  studies 
  have 
  

   added 
  much 
  to 
  our 
  knowledge 
  of 
  the 
  conditions 
  of 
  sedimentation 
  found 
  

   in 
  inland 
  seas. 
  Princeton 
  University 
  has 
  sponsored 
  expeditions 
  to 
  

   the 
  Bahamas 
  for 
  the 
  investigation 
  of 
  shallow-water, 
  calcareous 
  sedi- 
  

   ments, 
  a 
  relatively 
  unexplored 
  field. 
  It 
  is 
  hoped 
  that 
  data 
  obtained 
  

   from 
  studies 
  of 
  this 
  type, 
  to 
  cite 
  but 
  a 
  few 
  examples, 
  will 
  help 
  solve 
  

   some 
  of 
  the 
  problems 
  of 
  the 
  stratigrapher 
  and 
  lead 
  to 
  a 
  better 
  interpre- 
  

   tation 
  and 
  understanding 
  of 
  the 
  environments 
  which 
  produced 
  the 
  

   different 
  sedimentary 
  rocks. 
  

  

  SUBMARINE 
  CANYONS 
  AND 
  ROCK 
  DREDGING 
  

  

  Within 
  the 
  last 
  few 
  years 
  the 
  submarine-canyon 
  problem 
  has 
  pro- 
  

   voked 
  so 
  much 
  discussion 
  that 
  the 
  subject 
  has 
  become 
  familiar 
  to 
  all 
  

   geologists. 
  Although 
  their 
  existence 
  has 
  been 
  known 
  since 
  J. 
  D. 
  Dana's 
  

   day, 
  they 
  had 
  attracted 
  but 
  little 
  attention 
  until 
  the 
  United 
  States 
  

   Coast 
  and 
  Geodetic 
  Survey 
  completed 
  the 
  first 
  surveys 
  of 
  Georges 
  

   Bank 
  by 
  radio-acoustic 
  ranging. 
  For 
  the 
  first 
  time 
  an 
  adequate 
  picture 
  

   of 
  their 
  true 
  configuration 
  was 
  available, 
  and 
  Dr. 
  F. 
  P. 
  Shepard 
  (1933 
  ; 
  

   1934) 
  was 
  quick 
  to 
  grasp 
  the 
  significance 
  of 
  the 
  new 
  evidence. 
  As 
  

   more 
  of 
  these 
  gorges 
  were 
  discovered, 
  and 
  particularly 
  as 
  the 
  continen- 
  

   tal 
  slope 
  between 
  the 
  major 
  valleys 
  was 
  shown 
  to 
  be 
  deeply 
  scoured 
  and 
  

   channeled, 
  geologists 
  realized 
  that 
  they 
  were 
  faced 
  with 
  a 
  problem, 
  

   world-wide 
  in 
  its 
  scope, 
  for 
  which 
  they 
  had 
  no 
  ready 
  explanation. 
  The 
  

   multiplicity 
  of 
  the 
  theories 
  that 
  have 
  been 
  put 
  forward 
  is 
  an 
  index 
  

   of 
  the 
  general 
  perplexity. 
  Some 
  consider 
  that 
  the 
  erosion 
  is 
  due 
  to 
  

   stream 
  cutting 
  and 
  would 
  alter 
  the 
  relationships 
  of 
  land 
  and 
  sea 
  to 
  a 
  

   hitherto 
  undreamt 
  of 
  extent 
  (Veatch 
  and 
  Smith, 
  1939) 
  ; 
  another 
  con- 
  

   ceives 
  of 
  a 
  great 
  lowering 
  of 
  sea 
  level 
  by 
  postulating 
  a 
  vastly 
  thickened 
  

   and 
  extended 
  Pleistocene 
  ice 
  cap 
  (Shepard, 
  1936) 
  ; 
  still 
  others 
  consider 
  

   that 
  the 
  erosion 
  took 
  place 
  beneath 
  the 
  sea. 
  One 
  hypothesis 
  calls 
  

   for 
  turbidity 
  currents 
  made 
  heavy 
  by 
  their 
  load 
  of 
  mud 
  acquired 
  from 
  

   the 
  Continental 
  Shelf 
  by 
  wave 
  action 
  during 
  the 
  lowered 
  sea 
  level 
  of 
  

   the 
  Pleistocene. 
  These 
  currents 
  ran 
  down 
  the 
  slope 
  and 
  scoured 
  it 
  as 
  

   they 
  sought 
  the 
  depths 
  of 
  the 
  ocean, 
  as 
  well 
  as 
  "triggering 
  off" 
  mud 
  

   slides 
  by 
  the 
  friction 
  of 
  their 
  passage 
  (Daly, 
  1936). 
  The 
  latest 
  hy- 
  

   pothesis 
  in 
  the 
  case 
  of 
  the 
  east 
  coast 
  of 
  the 
  United 
  States 
  invokes 
  

   artesian 
  springs 
  flowing 
  out 
  from 
  the 
  Coastal 
  Plain 
  formations 
  along 
  

   the 
  continental 
  slope, 
  possibly 
  at 
  a 
  time 
  when 
  this 
  wedge 
  of 
  sediments 
  

   had 
  a 
  greater 
  westward 
  extent 
  than 
  it 
  has 
  today, 
  and 
  by 
  their 
  long- 
  

  

  