A newly launched research program permitted the sampling of speleothem deposit in the Algarve area (Southern
Portugal) with the primary objective of constraining the ages of past humid intervals in the area from U-series
measurements.Os sedimentos estuarinos constituem valiosos registos das variações das condições climáticas e ambientais regionai

Ghaleb, Bassam

Hillaire-Marcel, C.

Hélie, Jean-François

Luis, Joaquim

Moura, Delminda

Veiga-Pires, C.

Universidade do Algarve

Geophysical Research Abstracts
Vol. 13, EGU2011-3905, 2011
EGU General Assembly 2011
© Author(s) 2011
A first Last Glacial Maximum to Younger Dryas stalagmite record from
southern Portugal
Cristina Veiga-Pires (1), Bassam Ghaleb (2), Jean-François Hélie (2), Delminda Moura (1), Joaquim Luis (1), and
Claude Hillaire-Marcel (2)
(1) Universidade do Algarve, FCT-CIMA, Faro, Portugal (cvpires@ualg.pt, +351289800069), (2)
GEOTOP-UQAM-McGILL, Montreal, Canada
A newly launched research program permitted the sampling of speleothem deposit in the Algarve area (Southern
Portugal) with the primary objective of constraining the ages of past humid intervals in the area from U-series
measurements. A first 180 mm-long stalagmite has been analyzed. It yielded very small amounts of U (∼ 20 ppb).
Adding to the presence of a detrital "contaminating" fraction labelled by 232Th contents around 10 ppb, the subse-
quent lack of precision on 230Th measurements resulted in relatively large uncertainties for the calculation of the
accretion chronology of this stalagmite. 14C-data however provide some complementary information. With some
caveat about impacts of climatic changes on the U- vs 232Th-series systematics of the contaminating fraction, ages
ranging∼ 20 to∼10 ka are estimated from the base to the top of the stalagmite. The set of ages indicate deposition
from the Last Glacial Maximum (LGM) until the end of the YD, but for a precipitation gap matching possibly
the Bølling-Allerød interval. Information about paleoclimate conditions during the two precipitation intervals was
investigated using stable isotope measurements, following satisfying Hendy tests performed at three levels in the
stalagmite. Accordingly, the deglacial sequence may be interpreted in relation with paleoclimate/paleovegetation
conditions in the overlying environment. Carbon isotope values range from -9 to -7h (vs VPDB), and suggest a
recharge with a soil CO2 composition intermediate between those of C4 and C3 plant covers. Oxygen isotope delta
values range from -2h (vs VPDB), at the bottom, to -3h near the top of the stalagmite. From this preliminary
study, we conclude that if more humid conditions during the LGM and cold deglacial stages indeed led to carbonate
deposition in caves, they were not necessarily accompanied with drastically lower temperatures than at present.
A first Last Glacial Maximum to Younger Dryas stalagmite record from southern Portugal 
Cristina Veiga‐Pires (1), Bassam Ghaleb (2), Jean‐François Hélie (2), Delminda Moura (1), Joaquim Luis (1), and Claude Hillaire‐Marcel (2) 
(1) Universidade do Algarve, FCT‐CIMA, Faro, Portugal (cvpires@ualg.pt, +351289800069), (2) GEOTOP‐UQAM‐McGILL, Montreal, Canada 
Conclusions: From this preliminary study, we conclude that if more humid conditions 
during the LGM and cold deglacial stages indeed led to carbonate deposition in caves, 
they were not  necessarily  accompanied with drastically   lower temperatures than at 
present. 
Introduction:   The   newly   launched   SIPCLIP   research   project   permitted   the 
sampling  of   a   stalagmite   from  “Gruta  da   Senhora”   cave   in   the  Algarve   area 
(Southern Portugal) with the primary objective of constraining the ages of past 
humid intervals in the area from U‐series measurements. The geological regional 
setting is characterized by limestones from the Late Jurassic (Kimmeridgian). 
U‐series   systematics:  A   first  180  mm‐long  stalagmite   (GS)  has  been analyzed.   It   yielded  very   small 
amounts of U (20 ppb). Adding to the presence of a detrital “contaminating” fraction labeled by 232Th 
contents around 10 ppb, the subsequent lack of precision on 230Th measurements resulted in relatively 
large   uncertainties   for   the   calculation   of   the   accretion   age   of   this   stalagmite.   However,   a   14C‐
measurement on a sample from 17‐18 cm below the top of the stalagmite provides a complementary 
information:  21880  ± 370  yrs   cal  BP.  Assuming  no   significant  dead   carbon   contribution,   then   the 
authigenic 230Th/234U ratio corresponding to this age can be calculated: 0.183, and used to correct for the 
detrital contamination of all the others samples.  
U‐series   chronology:   The   observed   inversion   of   ages   in   sample   GSC   9‐11   is 
probably   due   to   the   very   low  amount  of  measured   230Th   (~10  pg)   and  high 
quantity of detrital 232Th as shown on the greyscale profile. Accordingly, and with 
some   caveat   about   impacts   of   climatic   changes   on   the   U‐   vs   232Th‐series 
systematics of the contaminating fraction, ages ranging  20 to 10 ka are estimated 
from the base to the top of the stalagmite. The set of ages indicate deposition 
from   the   Last   Glacial  Maximum   (LGM)   until   the   end   of   the   YD,   but   for   a 
precipitation gap matching possibly the Bølling‐Allerød interval.  
Stable isotopes systematics : Information about paleoclimate conditions during 
the two precipitation intervals was searched using stable isotope measurements, 
following satisfying Hendy tests performed at three levels in the stalagmite.  
Stable   isotopes   measurements:  The   deglacial   sequence   may   be   interpreted   in   relation   with 
paleoclimate/paleovegetation conditions   in   the overlying  environment.  Carbon  isotope values   range 
from ‐9 to ‐7 ‰  (vs VPDB), and suggest a soil CO2 composition intermediate between those of C4 and 
C3 plant covers. Oxygen isotope delta values range from ‐2 ‰ (vs VPDB), at the bottom, to  ‐3 ‰ near 
the top of the stalagmite .  
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Acknowledgments: This work was realized under the  SIPCLIP project (PTDC/AAC‐CLI/100916/2008), 
financed by FEDER and OE, through Fundação para a Ciência e Tecnologia. 


A first last glacial maximum to younger dryas stalagmite record from southern Portugal

Sapientia

Geophysical Research AbstractsVol. 13, EGU2011-3905, 2011EGU General Assembly 2011© Author(s) 2011A first Last Glacial Maximum to Younger Dryas stalagmite record fromsouthern PortugalCristina Veiga-Pires (1), Bassam Ghaleb (2), Jean-François Hélie (2), Delminda Moura (1), Joaquim Luis (1), andClaude Hillaire-Marcel (2)(1) Universidade do Algarve, FCT-CIMA, Faro, Portugal (cvpires@ualg.pt, +351289800069), (2)GEOTOP-UQAM-McGILL, Montreal, CanadaA newly launched research program permitted the sampling of speleothem deposit in the Algarve area (SouthernPortugal) with the primary objective of constraining the ages of past humid intervals in the area from U-seriesmeasurements. A first 180 mm-long stalagmite has been analyzed. It yielded very small amounts of U (∼ 20 ppb).Adding to the presence of a detrital "contaminating" fraction labelled by 232Th contents around 10 ppb, the subse-quent lack of precision on 230Th measurements resulted in relatively large uncertainties for the calculation of theaccretion chronology of this stalagmite. 14C-data however provide some complementary information. With somecaveat about impacts of climatic changes on the U- vs 232Th-series systematics of the contaminating fraction, agesranging∼ 20 to∼10 ka are estimated from the base to the top of the stalagmite. The set of ages indicate depositionfrom the Last Glacial Maximum (LGM) until the end of the YD, but for a precipitation gap matching possiblythe Bølling-Allerød interval. Information about paleoclimate conditions during the two precipitation intervals wasinvestigated using stable isotope measurements, following satisfying Hendy tests performed at three levels in thestalagmite. Accordingly, the deglacial sequence may be interpreted in relation with paleoclimate/paleovegetationconditions in the overlying environment. Carbon isotope values range from -9 to -7h (vs VPDB), and suggest arecharge with a soil CO2 composition intermediate between those of C4 and C3 plant covers. Oxygen isotope deltavalues range from -2h (vs VPDB), at the bottom, to -3h near the top of the stalagmite. From this preliminarystudy, we conclude that if more humid conditions during the LGM and cold deglacial stages indeed led to carbonatedeposition in caves, they were not necessarily accompanied with drastically lower temperatures than at present.A first Last Glacial Maximum to Younger Dryas stalagmite record from southern Portugal Cristina Veiga‐Pires (1), Bassam Ghaleb (2), Jean‐François Hélie (2), Delminda Moura (1), Joaquim Luis (1), and Claude Hillaire‐Marcel (2) (1) Universidade do Algarve, FCT‐CIMA, Faro, Portugal (cvpires@ualg.pt, +351289800069), (2) GEOTOP‐UQAM‐McGILL, Montreal, Canada Conclusions: From this preliminary study, we conclude that if more humid conditions during the LGM and cold deglacial stages indeed led to carbonate deposition in caves, they were not  necessarily  accompanied with drastically   lower temperatures than at present. Introduction:   The   newly   launched   SIPCLIP   research   project   permitted   the sampling  of   a   stalagmite   from  “Gruta  da   Senhora”   cave   in   the  Algarve   area (Southern Portugal) with the primary objective of constraining the ages of past humid intervals in the area from U‐series measurements. The geological regional setting is characterized by limestones from the Late Jurassic (Kimmeridgian). U‐series   systematics:  A   first  180  mm‐long  stalagmite   (GS)  has  been analyzed.   It   yielded  very   small amounts of U (20 ppb). Adding to the presence of a detrital “contaminating” fraction labeled by 232Th contents around 10 ppb, the subsequent lack of precision on 230Th measurements resulted in relatively large   uncertainties   for   the   calculation   of   the   accretion   age   of   this   stalagmite.   However,   a   14C‐measurement on a sample from 17‐18 cm below the top of the stalagmite provides a complementary information:  21880  ± 370  yrs   cal  BP.  Assuming  no   significant  dead   carbon   contribution,   then   the authigenic 230Th/234U ratio corresponding to this age can be calculated: 0.183, and used to correct for the detrital contamination of all the others samples.  U‐series   chronology:   The   observed   inversion   of   ages   in   sample   GSC   9‐11   is probably   due   to   the   very   low  amount  of  measured   230Th   (~10  pg)   and  high quantity of detrital 232Th as shown on the greyscale profile. Accordingly, and with some   caveat   about   impacts   of   climatic   changes   on   the   U‐   vs   232Th‐series systematics of the contaminating fraction, ages ranging  20 to 10 ka are estimated from the base to the top of the stalagmite. The set of ages indicate deposition from   the   Last   Glacial  Maximum   (LGM)   until   the   end   of   the   YD,   but   for   a precipitation gap matching possibly the Bølling‐Allerød interval.  Stable isotopes systematics : Information about paleoclimate conditions during the two precipitation intervals was searched using stable isotope measurements, following satisfying Hendy tests performed at three levels in the stalagmite.  Stable   isotopes   measurements:  The   deglacial   sequence   may   be   interpreted   in   relation   with paleoclimate/paleovegetation conditions   in   the overlying  environment.  Carbon  isotope values   range from ‐9 to ‐7 ‰  (vs VPDB), and suggest a soil CO2 composition intermediate between those of C4 and C3 plant covers. Oxygen isotope delta values range from ‐2 ‰ (vs VPDB), at the bottom, to  ‐3 ‰ near the top of the stalagmite .  !18O!13CHiatusGreyscale-10-8-6-4-202-100-500501001502002508 10 12 14 16 18 20 22 24ISotopic composition (permil vs VPDB)Greyscale230Th Chronology (ka)Acknowledgments: This work was realized under the  SIPCLIP project (PTDC/AAC‐CLI/100916/2008), financed by FEDER and OE, through Fundação para a Ciência e Tecnologia. 

https://sapientia.ualg.pt/bitstream/10400.1/3065/1/Veiga-Pires%202011a%20EGU.pdf

A first last glacial maximum to younger dryas stalagmite record from southern Portugal

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