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Age determination of recent cave deposits using excess 210 Pb ‐ A new technique
Author(s) -
Baskaran M.,
Iliffe Thomas M.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl00531
Subject(s) - speleothem , geology , cave , stalagmite , calcite , glacial period , radiocarbon dating , stable isotope ratio , paleontology , pleistocene , geochronology , mineralogy , holocene , archaeology , geography , physics , quantum mechanics
Cave deposits have been widely used as proxy recorders in deciphering palaeoclimate during the last glacial/interglacial maxima (∼ 120 ka) [Harmon et al., 1975; Atkinson et al., 1978; Goede and Harmon, 1983; Ayliffe and Veeh, 1989]. Palaeoclimatic studies of cave deposits for the past 1–1000 yr time scale require a precise dating technique, that until now has been lacking. Due to the multiple sources of carbon in speleothems, 14 C dates obtained for recently deposited calcite are highly variable and thus, 14 C dating techniques are not suitable to obtain speleothem ages for the past 1–1000 years. Here, we show for the first time that speleothems contain high concentrations of excess 210 Pb and that this 210 Pb excess can be successfully employed to obtain growth rates of speleothems deposited during the last 100 years. Of two specimens analyzed, a tubular “soda straw” stalactite yielded a longitudinal growth rate of 1.1 mm/yr, while a normal icicle‐shaped stalactite had a lateral growth rate of 0.028 mm/yr. The mass growth rates of these two speleothems (149 and 78 mg/yr respectively) are comparable within a factor of two. Studies of fine‐scale variations in the isotopic composition of recent speleothems will help to corroborate the validity of palaeoclimate records obtained using longer lived isotopes and extending back into Pleistocene.