﻿R. 
  E. 
  Gregory 
  — 
  Gravels 
  at 
  Cuzco. 
  15 
  

  

  Art. 
  III. 
  — 
  The 
  Gravels 
  at 
  Guzco, 
  Peru; 
  by 
  Herbert 
  E. 
  

  

  Gregory.* 
  

  

  Introduction. 
  — 
  A 
  prominent 
  feature 
  of 
  the 
  Cuzco 
  Valley 
  is 
  

   a 
  fringe 
  of 
  unconsolidated 
  deposits 
  exhibited 
  as 
  walls 
  or 
  dis- 
  

   sected 
  slopes. 
  "With 
  the 
  exception 
  of 
  a 
  superficial 
  cover 
  of 
  

   recent 
  sediments 
  these 
  border 
  forms 
  are 
  the 
  remnants 
  of 
  pied- 
  

   mont 
  alluvial 
  deposits 
  which 
  date 
  from 
  a 
  time 
  when 
  waste 
  

   prepared 
  through 
  a 
  long 
  period 
  of 
  local 
  disintegration 
  was 
  

   stripped 
  from 
  the 
  highlands 
  and 
  carried 
  to 
  the 
  central 
  valley 
  

   below. 
  The 
  bulk 
  of 
  these 
  deposits 
  is 
  assigned 
  to 
  the 
  late 
  

   Pleistocene 
  on 
  the 
  basis 
  of 
  the 
  interlocking 
  relations 
  which 
  the 
  

   gravels 
  flanking 
  the 
  lower 
  slopes 
  sustain 
  to 
  the 
  slightly 
  

   modified 
  glacial 
  drift 
  now 
  occupying 
  the 
  valley 
  heads. 
  

  

  The 
  most 
  extensive 
  of 
  these 
  Pleistocene 
  fluvial 
  deposits 
  and 
  

   those 
  best 
  exposed 
  for 
  study 
  are 
  the 
  fans 
  which 
  mark 
  the 
  

   mouths 
  of 
  nearly 
  all 
  valleys, 
  even 
  minor 
  ravines 
  and 
  wet- 
  

   weather 
  channels, 
  which 
  enter 
  the 
  Cuzco 
  basin. 
  Two 
  of 
  these 
  

   fans, 
  San 
  Geronimo 
  and 
  Cuzco, 
  the 
  former 
  actively 
  aggrading, 
  

   the 
  latter 
  in 
  a 
  stage 
  of 
  rapid 
  disintegration, 
  are 
  conspicuous 
  

   among 
  the 
  gravel 
  accumulations 
  of 
  the 
  Cuzco 
  Valley, 
  and 
  are 
  

   somewhat 
  unusual, 
  both 
  in 
  extent 
  and 
  in 
  thickness, 
  as 
  border 
  

   features 
  of 
  a 
  valley 
  of 
  such 
  limited 
  dimensions. 
  

  

  The 
  Cuzco 
  fan, 
  while 
  presenting 
  no 
  essential 
  features 
  which 
  

   differentiate 
  it 
  from 
  other 
  examples 
  of 
  its 
  class, 
  is 
  deemed 
  

   worthy 
  of 
  somewhat 
  extended 
  description 
  in 
  view 
  of 
  twofacts: 
  

   (1) 
  the 
  city 
  of 
  Cuzco 
  is 
  built 
  on 
  the 
  outer 
  dissected 
  fringe 
  and 
  

   the 
  terminal 
  bluffs 
  of 
  the 
  fan 
  — 
  a 
  city 
  which 
  probably 
  marks 
  

   the 
  site 
  of 
  one 
  of 
  the 
  earliest 
  permanent 
  human 
  settlements 
  on 
  

   the 
  South 
  American 
  continent. 
  (2) 
  Because 
  these 
  gravels 
  

   have 
  yielded 
  implements, 
  pottery, 
  the 
  bones 
  of 
  lower 
  animals, 
  

   and 
  human 
  bones, 
  which 
  on 
  the 
  basis 
  of 
  a 
  preliminary 
  exam- 
  

   ination 
  were 
  tentatively 
  assumed 
  to 
  date 
  from 
  glacial 
  times. 
  f 
  

  

  Topography. 
  — 
  In 
  superficial 
  extent 
  the 
  Cuzco 
  gravels 
  are 
  

   arranged 
  as 
  a 
  wide-open 
  V 
  or 
  triangle 
  whose 
  apex 
  extends 
  to 
  

   the 
  divide 
  separating 
  the 
  Anta 
  and 
  the 
  Cuzco 
  basins 
  and 
  whose 
  

   base 
  forms 
  a 
  curved 
  line 
  reaching 
  from 
  the 
  Chunchullumayo 
  

   Quebrada, 
  where 
  it 
  merges 
  with 
  a 
  second 
  fan, 
  to 
  the 
  lime- 
  

   stone 
  bluffs 
  one 
  mile 
  due 
  north 
  of 
  the 
  railroad 
  station. 
  

   (See 
  map, 
  fig. 
  2.) 
  - 
  In 
  topographic 
  expression 
  it 
  consists 
  of 
  two 
  

   parts 
  : 
  the 
  lower 
  portion 
  on 
  which 
  the 
  city 
  is 
  built 
  is 
  bounded 
  

   on 
  the 
  north 
  and 
  northwest 
  by 
  steep-faced 
  bluffs 
  ; 
  on 
  the 
  south 
  

   and 
  west 
  it 
  grades 
  imperceptibly 
  into 
  the 
  main 
  valley 
  floor. 
  

  

  * 
  Geologist 
  of 
  the 
  Peruvian 
  Expedition, 
  1912. 
  

  

  f 
  Bingham 
  : 
  The 
  Discovery 
  of 
  Prehistoric 
  Human 
  Eemains 
  near 
  Cuzco, 
  

   Peru 
  ; 
  and 
  Bowman 
  : 
  The 
  Geologic 
  Relations 
  of 
  the 
  Cuzco 
  Remains. 
  This 
  

   Journal, 
  vol. 
  xxxiii, 
  pp. 
  297-325, 
  1912. 
  

  

  