Young et al. Littleton

19
© University of Reading 2008 www.reading.ac.uk UKAS 2011 05/07/22 Holocene Hydrological and Vegetation Changes in Ombrotrophic Bogs in Central Ireland: Implications for our Understanding of Climate History and Human Activities Young, D., Stastney, P., Black, S., Branch, N., Pritchard, O., McCarroll, J. and Whitaker, J.

Transcript of Young et al. Littleton

Page 1: Young et al. Littleton

© University of Reading 2008 www.reading.ac.uk

UKAS 2011

2 May 2023

Holocene Hydrological and Vegetation Changes in Ombrotrophic Bogs in Central Ireland: Implications for our Understanding of Climate History and Human ActivitiesYoung, D., Stastney, P., Black, S., Branch, N., Pritchard, O., McCarroll, J. and Whitaker, J.

Page 2: Young et al. Littleton

UKAS 2011

2

Introduction

• Littleton Bog, Co. Tipperary

• Milled peat production bog

• Formerly an ombrotrophic, raised bog

Page 3: Young et al. Littleton

UKAS 2011

Littleton Bog• Type site for the

Holocene vegetation history of Ireland (Mitchell, 1956; 1965)

3

Page 4: Young et al. Littleton

UKAS 2011Raised peat bogs as archives• Sensitive to changes in

precipitation-evapotranspiration balance since they are ombrotrophic, or literally ‘cloud-fed’ systems free from the influence of groundwater

• So a record of bog surface wetness can be a record of climate (precipitation and temperature) change

4

Page 5: Young et al. Littleton

UKAS 2011

5

Archaeology

Plank trackway2972-2789 cal BP

Brushwood trackway1865-1596 cal BP

Page 6: Young et al. Littleton

UKAS 2011

Methods• Loss-on-ignition• Humification

• Radiocarbon dating • Plant macrofossils• Pollen• Testate amoebae• Oxygen, carbon and hydrogen isotopes

6

Page 7: Young et al. Littleton

UKAS 2011

7

ca. 5 yr/cm

ca. 42 yr/cm

Page 8: Young et al. Littleton

UKAS 2011

Results: Plant Macrofossils

8

• Oligotrophic transitional bog during LTN 1, LTN 2

• Drier raised mire during LTN 3; Increasingly wet during LTN 4; drier in LTN 5; increased wetness during LTN 6

Page 9: Young et al. Littleton

UKAS 2011

Results: Pollen

9

• Stable bog surface during pollen zone 1• Hazel/bog myrtle declines during 2a-2b,

grasses/Sphagnum increase• Sphagnum/grasses decline, increased heath, pine

during 2c

Page 10: Young et al. Littleton

UKAS 2011

Results: Testate Amoebae

10

Reconstructed water table curve produced using Charman et al. (2007) transfer function, with thanks to Dan Charman, University of Exeter.

Page 11: Young et al. Littleton

UKAS 2011

Results: Stable Isotopes

11

Page 12: Young et al. Littleton

UKAS 2011

Composite diagram

12

Page 13: Young et al. Littleton

UKAS 2011

Medieval Warm Period

13

Page 14: Young et al. Littleton

UKAS 2011

Medieval Warm Period

14

Page 15: Young et al. Littleton

UKAS 2011

Bond events

15

Page 16: Young et al. Littleton

UKAS 2011

Bond events and trackways

16

Page 17: Young et al. Littleton

UKAS 2011

Dated archaeology at Littleton

• 13 structures dated:– 9 trackways– 4 platforms

• Apparently 2 main phases:– 3 earlier structures

are all constructed from Oak planks

– Later structures constructed from roundwood.

17

Page 18: Young et al. Littleton

UKAS 2011

Dated structures at Littleton

18

Page 19: Young et al. Littleton

UKAS 2011

Conclusions• Multi-proxy analysis from Littleton Bog shows

that evidence for climatic forcing of changes in the ecology of the bog.

• There is a link between changes in the circulation in the North Atlantic, and changes in effective precipitation at Littleton.

• These changes may have driven a series of bog bursts.

• Human activity on the bog adapted to these changes.

19