Depositional System, Petrography and Facies Analysis of Pleistocene Travertine in Southern MarcheE, Central Italy

1 CHAPTER  1:  INTRODUCTION  TO   THE  SUDY  OF   TRAVERTINE     1   –   INTRODUCTION:  THESIS  AIMS   Travertines   are   terrestrial   carbonates   that   are   deposited   exclusively   by   water   issuing   from   hydrothermal  springs  according  to  the  definition  by  Pedley  (1990).   Pleistocene-­‐Holocene   hydrothermal  spring  travertines  have  attracted  attention  for  centuries  since   the  Romans  extensively  quarried  the   lapis  tiburtinus   as  a  construction  building  stone.  Travertines   have   been   the   focus   of   numerous   studies   about   Quaternary   geology,   geomorphology,   hydrogeology,  Neogene  tectonics  and  paleoclimatology.  In  the  last  decades  several  travertine   depositing  sites  were  studied  in  detail  from  a  sedimentological  and  carbonate  petrography  point   of  view:  Tivoli  travertines  near  to  Rome  (Chafetz  and  Folk,  1984;  Faccenna  et  al.,  2008),  Mammoth   Hot  Spring  in  Yellowstone  National  Park  (Wyo ming,  USA,  Pentecost,  1990;  Fouke  et  al.,  2000)  and   Pamukkale  (Altunel  and  Hancock,  1993).   There  are  many  open  questions  regarding  the  type  of  precipitation  process  controlling  some   travertine  fabrics,  abiotic  vs.  biologically  (microbial)  mediation.  The  sc ientific  community  working   on  travertines  is  still  divided  on  this  point.  It  is  not  possible  to  clearly  establish  whether  travertine   precipitation  is  a  fully  abiotic  or  microbially  induced  process.  It  is,  however,  first  of  all  important  to   produce   a   detailed   database   of   the   different   fabric   types   and   their   occurrence   in   specific   depositional  settings,  controlled  by  hydrothermal  water  temperature,  velocity  of  flow  and  degree   of  turbulence  to  clearly  determine  the  physical  factors  affecting  travertine  carbona tes.  This  is  what   has  been  attempted  in  this  study.   This  thesis  investigates  the  travertine  deposits  of  the  Tronto  valley,  more  precisely  the  travertine   deposits  in  the  Acquasanta  Terme  area  (Upper  Pleistocene),  about  20  km  from  Ascoli  Piceno,   Southern  Mar che  (Central  Italy).   Different  travertine  units  were  analysed  within  two  quarries  that  show  different  depositional   systems  and  are  placed  at  two  different  topographic  elevations:  Tancredi  quarry  (451m)  and  Cardi   quarry  (335m).  These  elevations  relate  to  different  depositional  phases  and  ages;  in  fact  the  lower   unit  is  the  youngest  due  to  its  position  along  the  fluvial  valley  incision  of  the  Tronto  River.   The  aims  of  the  project  are:   1.  To  analyse,  describe  and  interpret  the  depositional  setting  of  the  several  carbonate  fabrics   of  the  Acquasanta  travertine  proposing  a  general  classification  of  the  carbonate  fabrics.