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Abstract

The  present  article deals with  the  pallen  analysis  of  a  section from a lake  (laguna de Los Bobos)  at an eleuation of 3800 metres  in  the  regían  of  Oak-forests near the  limit  of  the departments  of  Boyacá and  Santander  (Cordillera  Oriental,  Colombia).  The  diagram  shows two  more important   changes  of  "tree-line",  a rise  between  samples 21  and   20  and  a  fall between  samples  13 and  12. According  to  the  C14  dates, the  second  one  should  correspond to  the  Subboreal-Subatlantic   transition  in Europe.   Comparison  with  other diagrams  from Colombia shows  that  the  first  should  correspond  approximately to  the  Atlantic-Subboreal transition.  The  fall of  Alnus and  the  rise of  Quercus  between  samples 16 and 15  is another chango  of  vegetation,  also recognizable  in other  Colombian  diagrams. A  curve  for  Zea mais  (maize,  corn) and  the  C14  dates indicate  that  agricultura  was of  importance  in  the  lower  valleys  from  approximately 300 (-600) B. C.  until 1200 A. D.