Research  Report  Man  and  Biosphere  Young  Scientist  Award  

             By        

   

Juan  Carlos  Silva  Tamayo  Assistant  Professor,  Universidad  de  Caldas  Marie  Curie  Fellow,  Stanford  University  

         

Abstract    Stalagmites   and  organic   rich   sediments   from  high  altitude   continental  watersheds  

have  been  collected  and  dated  to  determine  their  potential  as  climate  variability  and  

high  altitude  biodiversity  archives.    Ages  spanning  from  16  Ky  to  the  present  have  

been  determined  using  U-­‐Th  dating  in  selected  stalagmite  records  from  the  Andean  

Mountain  Belt  (Cinturon  Andino)  in  northeastern  Colombia.  AMS  14C  dates  from  4.4  

Ky  to  the  present  have  been  in  turn  obtained  in  continuous  sediment  cores  from  a  

watershed  in  the  most  northern-­‐central  part  of  the  Cinturon  Andino.  The  obtained  

ages  allowed  selecting  these  records  for  further  research  in  climate  variability  and  

biodiversity  during  the  late  Holocene  at  the  Tropical  Cinturon  Andino.  

             

1.  Introduction    

The  20th  century  witnessed  an  exponential  increase  in  anthropogenic  CO2  emissions  

to   the   atmosphere.   Investigating   the  possible   effects   of   anthropogenic   (industrial)  

CO2   emissions   on   global   climate   has   become   a   priority   to   the   international  

community.    

 

Intensive  research  has  been  done  in  order  to  constrain  the  effects  of  global  warming  

on  the  marine  and  continental  ecosystems  and  on  the  water  resources.  However  the  

real   effects   (magnitude   and   timing)   of   anthropogenic   CO2   emissions   and   global  

climate  warming  have  remained  controversial  due  to  the  discrepancies  of  the  short  

term   -­‐   instrumental   data   (restricted   to   a   few   decades).   Moreover,   the   lack   of  

continuous   and   reliable   instrumental   data   at   equatorial   latitudes   hampers   our  

understanding   of   the   effects   of   anthropogenic   CO2   emissions   and   global   climate  

variability   on   the   equatorial   continental   and   marine   ecosystems   and   water  

resources.        

 

This   research  aims  on   investigating   the   real   effects  of   changing   atmospheric  pCO2  

and  global   climate  variability  on   the  equatorial  high  altitude   (Andean)  continental  

ecosystems  and  on  the  northern  South  American  Pre-­‐Hispanic  Cultures.    

 

High-­‐resolution  oxygen   isotopes   in   speleothems,   especially   stalagmites,   have  been  

recently   successfully   used   to   investigate   regional   and   global   climate   variability.    

Several   speleothem   sites   were   visited   along   the   Andean  Mountain   Belt   (Cinturon  

Andino)  to  collect  stalagmite  that  can  provide  continuous  high-­‐resolution  records  of  

Climate  variability  along  this  UNESCO  biosphere  reserve.      

 

Funding   from   the   MAB   have   been   used   to   support   this   research.   Specifically,  

Funding   have   been   used   to   help   performing   the   geochronology   of   these   climate  

archives.    

Here  we  report  precise  U-­‐Th  dating  of  several  stalagmites  from  one  site  (the  Penon  

cave)   at   the   northeastern   most   part   of   the   Cinturon   Andino.   Results   suggest  

stalagmite  record  of  climate  variability  extending  back  t  16  Ky.  

 

High   altitude   mountain   watersheds   and   lake   are,   on   the   other   hand,   alternative  

archives  of  climate  variability  and  also  mountain   floral  biodiversity.  One  sediment  

core  was   collected   on   a  watershed   from   at   the   central   north-­‐western  Andes.   This  

watershed   is   located   at   the   Sub  Paramo-­‐Paramo  boundary   right   below  where   the  

tree   line   is   located   (ca   4200   masl).   Funding   from   the   MAB   program   also   helped  

dating   this   core.   Late  Holocene   ages   have  been  obtained   for   this   core.   These   ages  

may   provide   important   information   about   the   changes   on   floristic   biodiversity  

during  the  late  Holocene  that  can  be  compared  with  the  high-­‐resolution  stalagmite  

record  of  climate  variability.  

 2.  Location  of  the  studied  areas    Several   speleothem   sites   have   been   visited   along   the   Cinturon   Andino   and   the  

Caribbean  Region  (i.e.  Colombia  and  Panama,  Fig.  1).    These  sites  contain  potential  

stalagmite  growths  that  can  be  potentially  used  for  climate  variability  studies.  These  

sites  also  present  variable  lithologies  which  span  from  the    early-­‐middle  Paleozoic,  

up  to  the  Miocene.  

 

Watershed  cores  have  been  collected  at  the  Triunfo  watershed  of  the  amortisation  

area  of  the  Colombian  Snow  Peaks  Natural  National  Park.  The  study  area  is  located  

at   the   Central   Cordillera   of   Colombia.   This   area   is   characterized   by   a   continuous  

volcanic  activity  (Fig.  1).  

 

3.  Results        

 

Initial   stratigraphic   analysis   of   ca   30   stalagmites   allowed   selecting   the   best-­‐

preserved  and  likely  more  continuous  records  for  high  resolution  U-­‐Th  dating.  From  

all  the  visited  sites  (7  in  total,  Fig.  1)  only  2  (The  Penon  Area)  provided  stalagmites  

with   no   obvious   stratigraphic   discontinuities   (Fig.   2).   The   visited   sites   at   the   la  

Guajira,  Toluviejo,  Los  Guacharos  National  Park  and  the  San  Luis  Park  in  Colombia  

and   the  Maje  Area   in  Panama  did  not  provide   stalagmite   records  with   continuous  

stratigraphies.  More  importantly,  in  these  sites,  the  stalagmites  usually  display  high  

detritus  contents,  which,  due  to  their  high  Th  contents,  can  hamper  the  U-­‐Th  dating.  

 

                                                   

 Figure.  1.  Location  of  the  study  areas.  1  Toluviejo  (60  masl),    2.  Alta  Guajira  (30  masl),  3.  Rio  Claro  (600  masl),  4.  Maje  (10  

masl),  5  El  Penon  and  Indio  Caves  (2000  masl),  6.  Guacharos  (2300  masl),  7.  Triunfo  watershed  (National  Snow  Peaks  Park).  White  squares  are  caves.  Gray  squares  are  lakes.  

 

 

 

 

 

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 Figure.  2.  View  of  the  El  Penon  Cave  and  some  examples  of  the  dated  stalagmites.  Note  the  high  resolution  record  offered  by  

the    annual  growth  rings  of  the  stalagmite  records.    

 

The  stalagmite  records  yield  U-­‐Th  ages  that  extend  back  to  16  Ky  (Fig.  3).      One  of  

the   stalagmites   presents   an   stratigraphic   record   that   even   extend   farther   back   to  

what  can  be  determined  by  using  the  U-­‐Th  technique.  

 

The   core   analysed   from   the   Triunfo   watershed   provided   a   continuous   age  

sedimentation  record  since  4.4  ky  (Fig.  4).  This  6  m  core  shows  no  evident  signs  of  

stratigraphic  discontinuities,  but  the  presence  of  some  intervals  with  volcanic  ashes  

accumulations  may  suggest  a  lack  of  record  of  biologic  material,  i.e.  polen,  that  can  

be   used   for   reconstructing   biodiversity   changes   along   the   high   altitude   Cadena  

Andina.   However   almost   80%   of   the   core   corresponds   to   well   preserved   fine-­‐

grained,  organic  rich  material  that  can  be  used  for  this  purposes.    

   

              Years  before  the  present      Figure.  3.  U/Th  Ages  of  the  analyzed  stalagmites  at  the  El  Penol  cave.  Notice  how  the  different  dated  stalagmites  show  a  

continuous  Holocene  record.  Se  also  figure  2  for  quality  of  the  stalagmite  records.          

0 2000 4000 6000 8000 10000 12000 14000 16000

C AR  7

C AR  3

C AR  2

T empo  (anos  A .P .)

C AR  1

     

   Figure.  4.  AMS  14C  ages  of  one  single  sediment  core  in  a  watershed  at  the  Snow  peaks  National  Park  of  Colombia.  Northern  

Andean  Mountain  Belt  (  Cinturon  Andino).  See  Fig.  1  for  location.                

4.  Conclusions.    Speleological   visits   to   seven   speleothem   sites   in   northern   South   America   and  

Panama   allowed   identifying   excellent   stalagmite   records   for   climate   variability  

studies.    Thus  far,  only  one  site  (El  Penon),  provided  satisfactory  stalagmite  records  

that   can   be   used   for   these   purposes.   Precise   high   resolution   U-­‐Th   dating   of   the  

stalagmite  records  at  this  site  yield  ages  that  span  the  whole  Holocene  and  even  to  

the   late  Pleistocene.  The  age  of  one  stalagmite  can  extend  more  back   in  time.  AMS  14C  dating  of  a  sediment  core  from  a  watershed  at  the  northern-­‐Central  Colombian  

Andes   provided   late   Holocene   ages.     The   combined   stalagmite   and   watershed  

archives  allow  predicting  continuous  records  of  climate  variability  and  biodiversity  

in  the  northern  most  part  of  the  Tropical  Cinturon  Andino.  

 

5.  Future  research,  outreach  and  prespectives.    The   ages   obtained   and   the   characteristics   of   the   studied   geologic   records   suggest  

that   these   are   good   archives   for   climate   variability   and   biodiversity   during   the  

Holocene   at   the   equatorial   Neotropics,   specially   along   the   Cadena   Andina.    Multi-­‐

proxies   analyses   are   currently   being   done   in   the   watershed   cores,   i.e.  

sedimentology,   palynology,   geochemistry,   in   the   high   altitude  water   located   along  

the   Central   and   Western   Cordillera   of   Colombia   (Fig.   1).   Further   dating   of   three  

more  cores  will  be  performed.  A  master  student  is  currently  doing  this  work  at  the  

Geosciences  Department  of   the  Caldas  University,  Manizales,  Colombia.    This  work  

will  allow  correlating  main  Holocene  changes  in  regional  climate  and  rain  regime  to  

major  modifications  of  the  equatorial  high  altitude  ecosystems.    

 C  and  O  isotope  analyses  are  currently  being  done  in  the  Late  Holocene  well-­‐dated  

stalagmites  from  the  El  Penon  site  in  north-­‐eastern  Colombia  (Fig.  1).    This  work  is  

currently  being  perform  by  a  Colombia  (geologist-­‐anthropologist)  master  student  at  

the  Geoscience  Department  of   the  Sao  Paulo  University,  Sao  Paulo,  Brazil.    Besides  

determining   climate   variability,   this   student   is   also   currently   determining   how  

important   changes   on   the   Colombian   pre-­‐Hispanic   pottery   styles,   which   seem   to  

have  paralleled  main  cultural  changes  that  occurred  around  the  9th  century  A.D.  are  

related  to  major  changes  in  regional  tropical  climate.  This  research  ultimately  aims  

on  contributing  to  have  a  better  understanding  of  the  possible  future  effects  (timing  

and   magnitude)   of   climate   variability   and   water   resources   crises   on   the   human  

population  around  the  equator.      

 

One  Brasilian  PhD  student  is  concentrated  on  the  long  term  (Pleistocene  to  recent)  

record  of  climate  variability  based  on  the  well-­‐dated  stalagmites  from  the  El  Penon  

site.  This   research  will  provide   important   information  of   the   longterm  vs  shortem  

climate  variability  in  the  Neotropical  Cadena  Andina.    

 Thus   far,   one   manuscript   is   being   written   focused   the   U-­‐Th   dating   of   the  

speleothems.  We  expect  to  have  other  two  manuscripts  written  by  the  end  2013  on  

both,  the  short  and  the  long-­‐term  climate  variability  along  the  Neotropical  Andean  

Chain.  

 

Finally,  the  University  of  Caldas  has  recently  funded  Dr  Juan  Carlos  Silva  –Tamayo  to  

continue   the   research   at   the   high   altitude   watersheds   of   Central   Colombia.   The  

funding  granted  to  Dr  Silva-­‐Tamayo  will  ensure  the  continuation  of  his  work  in  this  

area,  which  was  partially  funded  by  the  MAB  award.