In:
Radiocarbon, Cambridge University Press (CUP), Vol. 41, No. 3 ( 1999), p. 251-270
Abstract:
Twenty-two radiocarbon activity measurements were made by accelerator mass spectrometry (AMS) on 2 Holocene stalagmites from Belgium (Han-stm1b) and from southwest France (Vil-stm1b). Sixteen thermal ionization mass spectrometric (TIMS) U/Th measurements were performed parallel to AMS analyses. The past dead carbon proportion (dcp) due to limestone dissolution and old soil organic matter (SOM) degradation is calculated with U/Th ages, measured calcite 14 C activity and atmospheric 14 C activity from the dendrochronological calibration curves. Results show that the dcp is different for the 2 stalagmites: between 10,800 and 4780 yr from present dcp=17.5% (σ=2.4; n=10) for Han-stm1b and dcp=9.4% (σ=1.6; n=6) between 3070 and 520 yr for Vil-stm1b. Despite a broad stability of the dcp during the time ranges covered by each sample, a slight dcp increase of about 5.0% is observed in the Han-stm1b sample between 8500 and 5200 yr. This change is synchronous with a calcite δ 13 C increase, which could be due to variation in limestone dissolution processes possibly linked with a vegetation change. The dcp and δ 13 C of the 2 studied samples are compared with 5 other modern stalagmites from Europe. Results show that several factors intervene, among them: the vegetation type, and the soil saturation leading to variable dissolution process systems (open/closed). The good correlation (R 2 =0.98) between the U/Th ages and the calibrated 14 C ages corrected with a constant dcp validates the 14 C method. However, the dcp error leads to large 14 C age errors (i.e. 250–500 yr for the period studied), which is an obstacle for both a high-resolution chronology and the improvement of the 14 C calibration curves, at least for the Holocene.
Type of Medium:
Online Resource
ISSN:
0033-8222
,
1945-5755
DOI:
10.1017/S003382220005712X
Language:
English
Publisher:
Cambridge University Press (CUP)
Publication Date:
1999
detail.hit.zdb_id:
2028560-7
SSG:
11
SSG:
13
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