Gabor, Baker, McKnight, and Miller
324
such as the annual lamina width to be a record of water table variations in the overlying
peat and the extent of organic matter humification. The same stalagmite data have recently
been combined with tree ring records of water availability to produce a 1000-year long
record of the North Atlantic Oscillation (Trouet et al., 2009).
0.60
0.65
0.70
0.75
0.80
Intensity Ratio: 470/420 nm emission
Annual growth rate (microns)
0.85
0.90
0.95
900 1000 1100 1200 1300 1400 1500 1600 1700
Poorly humified
Well humified
1800 1900 2000
900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000
140
120
(a)
(b)
100
80
60
40
20
0
Year AD
Figure 9.11. A 1000-year record of organic matter humification preserved in a cave stalagmite. (a)
The annual band width (annual accumulation rate) of the stalagmite as determined by counting annual
bands formed from fluorescent organic matter. (b) The fluorescence ratio as determined by measuring
the intensity of emitted fluorescence at 420 and 470 nm. Low ratios (note the inverse scale) correlate
with periods of faster stalagmite growth due to a decrease in water table in the overlying peat and
increased CO 2 production and limestone dissolution. Low ratios therefore correspond to periods of
high humification. (Adapted from Proctor et al., 2000.)