NERC Radiocarbon Facility (Environment)

Transcription

1 RADIOCARBON AGE REPORT Allocation No. 615/0795 Submitter: Project Title: D. Charman University of Plymouth Robustness and precision of Holocene palaeoclimatic records from peatlands and testate amoebae. Pretreatment of Raw Samples: Prior to isotope analyses the raw samples were digested in 2M HCl (at 80 C for 24 hours), washed free of acid, filtered and dried to constant weight in drying oven. Sample Series: Butterburn Flow. Sampling location: Butterburn Flow, Cumbria, England, (55 05'20"N 02 30'15"W ; Natl. Grid Ref. NY ). Samples composition and Collection: Peat from ombrotrophic peat bog. Recovered using Russian corer. Collected D. Hendon September 1995 and submitted D. Charman, University of Plymouth. SRR-5991 BBF I 40-45cm 385 ± 45 δ 13 C = SRR-5992 BBF I cm 1220 ± 45 δ 13 C = SRR-5993 BBF I cm 2325 ± 40 δ 13 C = SRR-5994 BBF I cm 3625 ± 45 δ 13 C = SRR-5995 BBF I cm 5070 ± 45 δ 13 C = SRR-5996 BBF I cm 6210 ± 45 δ 13 C = SRR-5997 BBF I cm 8225 ± 45 δ 13 C = -27.7

2 This series of dates suggests an almost perfect linear relationship between peat depth and age and provides a sound basis for age estimation between dated horizons. These dates also test correlations of reconstructed water tables with the records from Coom Rigg Moss (SRR-5998 to 6011). The dates confirm the Butterburn Flow record is much longer than at Coom Rigg. Major fluctuations in water tables from 2325 ± 40 (SRR-5993) onwards occur at the same times as in Coom Rigg Moss, but prior to this the records differ significantly from each other. This, together with the convergence of water table records for CRM I and CRM IV suggests that climatic control on surface wetness of ombrotrophic mires increases in the later Holocene and especially over the last 1500 years. Sample Series: Coom Rigg Moss I. Sampling location: Coom Rigg Moss, Northumberland, England, (55 06'45"N 02 28'53"W ; Natl. Grid Ref. NY ). Samples composition and Collection: Peat from ombrotrophic peat bog. Recovered using Waardenaar and Russian corers. Collected D. Hendon November 1994 and submitted D. Charman, University of Plymouth. SRR-5998 CRM I 40-42cm 270 ± 45 δ 13 C = SRR-5999 CRM I cm 1370 ± 40 δ 13 C = SRR-6000 CRM I cm 2500 ± 40 δ 13 C = SRR-6001 CRM I cm 3550 ± 40 SRR-6002 CRM I cm 4585 ± 40 δ 13 C = The series SRR-5998 to SRR-6002 and SRR-6007 to SRR-6011 are conformable sets of dates for two closely spaced cases (10m apart) in the centre of Coom Rigg Moss. They show the peat has a variable accumulation rate over quite small distances. The whole series (SRR-5998 to SRR-6011) was aimed at testing hypothesised correlations between water table records derived from fossil testate amoebae. The dates for CRM I (SRR-5998 to SRR-6002) and CRM IV (SRR-6007 to -6011) show that major water table fluctuations are coincident in the two cors. However, CRM IV shows much greater variability in water table between 2255 ± 40 BP (SRR-6009) and 3325 ± 40 BP (SRR-6010). The dates for the cores from the periphery of the site (SRR-6003 to SRR-6006) generally suggest that the site edges were responding to different hydrological controls in the late Holocene. However, there is some evidence for increasing

3 wetness across the entire site with the coincidence of SRR-6004 (1340 ± 45BP) from CRM II and SRR (1285 ± 40 BP) from CRM III with similar changes in CRM I and CRM IV.

4 Sample Series: Coom Rig Moss II.Sampling location: Coom Rigg Moss, Northumberland, England, (55 06'40"N 02 28'45"W ; Natl. Grid Ref. NY ). Samples composition and Collection: Peat from ombrotrophic peat bog. Recovered using Russian corer. Collected D. Hendon April 1995 and submitted D. Charman, University of Plymouth. SRR-6003 CRM II 45-50cm 375 ± 45 δ 13 C = SRR-6004 CRM II cm 1340 ± 45 δ 13 C = SRR-6005 CRM II cm 2215 ± 40 δ 13 C = -27.6

5 Sample Series: Coom Rig Moss III. Sampling location: Coom Rigg Moss, Northumberland, England, (55 06'50"N 02 28'45"W ; Natl. Grid Ref. NY ). Samples composition and Collection: Peat from ombrotrophic peat bog. Recovered using Russian corer. Collected D. Hendon April 1995 and submitted D. Charman, University of Plymouth. SRR-6006 CRM III cm 1285 ± 40 δ 13 C = -28.9

6 Sample Series: Coom Rig Moss IV. Sampling location: Coom Rigg Moss, Northumberland, England, (55 06'45"N 02 28'45"W ; Natl. Grid Ref. NY ). Samples composition and Collection: Peat from ombrotrophic peat bog. Recovered using Russian corer. Collected D. Hendon April 1995 and submitted D. Charman, University of Plymouth. SRR-6007 CRM IV 30-35cm 250 ± 45 δ 13 C = SRR-6008 CRM IV cm 1645 ± 45 SRR-6009 CRM IV cm 2255 ± 40 δ 13 C = SRR-6010 CRM IV cm 3325 ± 40 SRR-6011 CRM IV cm 3965 ± 40

7 Sample Series: The Wou. Sampling location: The Wou, Northumberland, England, (55 01 N 02 30'15"W ; Natl. Grid Ref. NY ). Samples composition and Collection: Peat from minerogenic peat mire. Recovered using Russian corer. Collected D. Hendon September 1995 and submitted D. Charman, University of Plymouth. SRR-6012 TW II cm 265 ± 45 δ 13 C = SRR-6013 TW II cm 1340 ± 40 δ 13 C = These dates delimit the tope and base of the reconstructed water table record from The Wou, a minerotrophic mire close to Coom Rigg Moss and Butterburn Flow where longer records of water table change have been constructed (SRR-5991 to SRR-6018 to SRR-6113 inclusive). The water table changes at The Wou are synchronous with those recorded in the ombrotrophic mire suggesting a climatic signal is present in minerotrophic as well as in ombrotrophic mires. Publications Arising: B.F.Miller 25 August 1997