Lake sub-fossil material to extend living chronologies

In 2008, a survey of of lochans in the NW Cairngorms region identified several lakes with abundant amounts of preserved pine woody material in the sediments. The picture below shows the initial 25 preliminary samples taken from two lochs (Eilein and Gamnha) in the Rothiemurchus Estate which were carbon dated in 2009. Although these preliminary samples were taken using a pruning saw and 10mm corer, some of these samples had > 150 rings.

Carbon dating of these samples indicated ages ranging from 200-8000 yrs. BP. When compared to carbon dates from peat pine macrofossils, it is clear that there is no evidence, so far, for trees in this region dying around the so called "pine decline" around 5000 yrs BP. Only more samples can answer the disparity of these results. The cluster of samples from the last millennium suggests that building at least a 1000 year continuous tree-ring chronology appears attainable. The cluster of dates around ~8000 yrs. BP is also worthy of note and suggests long term potential of a supra-long chronology for the Scottish Highlands. A paper of this early phase work can be download from this [link].

 

Since 2009, extraction of sub-fossil material from the Northern Cairngorms and Glen Affric has continued. We now have about 1000 sub-fossil samples of which about 1/3rd have been dated through dendrochronological or radiocarbon methods. The main regions of focus have been (1) Loch an Eilein and Loch Gamnha (Rothiemurchus Estate), (2) Ryvoan Pass (Greenloch)/Abernethy Pine woodlands and (3) Glen Affric. The current floating chronologies are detailed below.

The NERC SCOT2K project will is focussing on the development of a 2000 year continuous tree-ring record for the Scottish Highlands. Such chronology development is a real challenge.

		Calendar Date	Years	series	trees	C14 Dates
Loch an Eilein and Loch Gamnha
Dating method	Living	1696-2013	318	222	lots	na
TR + 14C	Float7	1682-1901	220	89	34	3
TR + 14C	Float2	1518-1745	228	36	15	1
TR	Float20	1370-1542	173	12	5	0
TR + 14C	Float23	1200-1502	303	45	20	8
TR + 14C	Float14	1089-1333	245	25	7	1
	14C based dates below - not dendro validated
14C	Float24	851-1051	246	10	5	0
14C	Float26	817-948	132	11	5	1
14C	Float1	642-898	257	20	9	2
14C	Float19	546-792	247	20	9	1
14C	Float13	148-353	206	51	27	2
14C	AD/BC
14C	Float16		114	5	2	1
14C	Float15	-1246 to -1009	237	9	5	1
14C	Float22		226	8	4	1
14C	Float5	-4075 to -3738	191	6	3	1
14C	Float17	-4132 to -3875	258	11	5	1
14C	Float12	-5174 to -4796	277	15	6	2
14C	Float11	-5175 to -4866	311	5	2	1
14C	Float9	-5423 to -5232	192	7	5	2
14C	Float3	-6008 to -5684	325	20	11	5
Abernethy and Green Loch
TR	ABW	1735-2009	275	80	80	0
TR	GRN + talus	1436-2013	578	223	lots	0
TR	Float1 (grn and ab)	1434-1970	537	181	79	0
TR	Float2 (ab only)	1176-1351	176	4	2	0
Glen Affric
	Living	1693-2013	321	189	lots	0
TR	Float1	1452-1844	393	72	33	0
TR	Float 10	1260-1558	299	21	8	0
TR + 14C	Float 5	724-1064	406	26	12	0

 

TR = tree-ring based dendrochronological date. Exact to the year.
14C dating precision varies through time, but is generally +/- 30-40 years.
TR + 14C date - denotes both tree-ring dating and consistent (within error) radiocarbon dating.