Mg, Sr and Sr isotope geochemistry of a Belgian Holocene speleothem: implications for paleoclimate reconstructions

87 86 Ž In this study, variations in MgrCa, SrrCa and Srr Sr ratios in a Holocene Belgian speleothem cave secondary . carbonate deposit are interpreted in terms of changes in water residence time and changes in weathering processes, possibly Ž . induced by changes in West European climate. A stalagmite from the Pere Noel cave Belgium was dated with the TIMS ` ̈ UrTh method and was deposited between ;13 and ;2 ka BP. The 1000 MgrCa ratio varies between 4.9 and 26, and displays short-term changes but no significant long-term trend. The 1000 SrrCa ratio varies between 0.09 and 0.31 and displays both short-term changes and a long-term decreasing trend from 12.9 to 3.5 ka. In parallel, the Sr isotopic composition of the speleothem decreases from 0.7090 at 12.9 ka to 0.7088 at 3.5 ka. The Sr isotope ratio is higher than Ž 86 . expected from the overlying limestone Srr Srs0.7081 which implies an external source of radiogenic Sr, most probably from a silicate phase. Short-term and long-term changes in MgrCa, SrrCa as well as long-term changes of SrrSr ratios can be explained by changes in the dissolution and precipitation processes of the host limestone. These Ž processes are controlled by changes in water residence times linked to changes in the water excess precipitation minus . evapo-transpiration . q 2000 Elsevier Science B.V. All rights reserved.