HR: 1330h
AN: PP42A-0856    [PDF]
TI: The Carbon Isotopic Record from Hulu Cave, China and C$_{3}$/C$_{4}$ Vegetation History from 75 to 10.9 ka
AU: * Smith, E A
EM: smit1853@umn.edu
AF: Dept of Geology and Geophysics, U. of Minnesota, 310 Pillsbury Dr SE, Mpls, MN 55455 United States
AU: Wang, Y
EM: yjwang@njnu.edu.cn
AF: College of Geography Science, Nanjing Normal University, Nanjing, 210097 China
AU: Cheng, H
EM: cheng021@umn.edu
AF: Dept of Geology and Geophysics, U. of Minnesota, 310 Pillsbury Dr SE, Mpls, MN 55455 United States
AU: Carpenter, S
EM: scott-j-carpenter@uiowa.edu
AF: Dept of Geoscience, U. of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242 United States
AU: Dorale, J A
EM: doralej@missouri.edu
AF: Dept of Geoscience, U. of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242 United States
AU: Edwards, R L
EM: edwar001@umn.edu
AF: Dept of Geology and Geophysics, U. of Minnesota, 310 Pillsbury Dr SE, Mpls, MN 55455 United States
AB: We present a carbon isotopic record for eastern China, from a nearly continuous sequence of stalagmites (MSD, MSL, YT, H82) from Hulu Cave (32$\deg$N, 119$\deg$E). The record corresponds to the oxygen isotopic record of Wang et al. (2001), with ages from 74.9 to 10.9 ka (based on $^{230}$Th dates). $\delta$$^{13}$C values range from -11.75 to -1.52$\permil$ (VPDB). From 75 to 60 ka, the $\delta$$^{13}$C is relatively light (mean = -8.5 $\pm$ 1.4$\permil$), excluding a 2 ky $\delta$$^{13}$C excursion $\sim$71 ka. From 60 to 25 ka, the $\delta$$^{13}$C alternates between heavy to intermediate values (range = -1.7 to -7.9$\permil$). From 25 to 10.9 ka, $\delta$$^{13}$C is light compared to the preceding interval except a 2$\permil$ positive shift synchronous with the Bolling/Allerod.\\\\ The carbon record of the four stalagmites replicate suggesting that factors such as changes in the hydrologic characteristics of individual drip pathways, amount of carbonate bedrock dissolved, or kinetic fractionation, do not affect $\delta$$^{13}$C significantly. Similarly, it is unlikely that variability is caused by changes in the proportion of atmospheric to soil-produced CO$_{2}$. If that was the case, one would expect high $\delta$$^{13}$C during cold, dry intervals, which is exactly the opposite of what we observe. Therefore, we conclude that the $\delta$$^{13}$C variations are likely caused by variation in the ratio of C$_{3}$ to C$_{4}$ vegetation above the cave. From 40 ka to 10.9 ka, the stalagmite $\delta$$^{13}$C values are broadly consistent with known vegetation patterns based on pollen records (Liu et al., 1992; Sun et al., 1997; Winkler and Wang, 1993).\\\\ Hulu Cave $\delta$$^{18}$O has features similar to Greenland ice core $\delta$$^{18}$O, with warmer temperatures during Greenland interstadials (heavy $\delta$$^{18}$O) correlated with stronger summer monsoons in China (light $\delta$$^{18}$O). Between 69-14.5 ka, Hulu Cave $\delta$$^{18}$O and $\delta$$^{13}$C are significantly anti-correlated (R = -0.80). During periods of stronger summer monsoons, suggestive of warmer temperatures and higher evapotranspiration, the record shows a greater abundance of C$_{4}$ vegetation. During periods of weaker summer monsoons, likely associated with colder temperatures, the record shows a greater abundance of C$_{3}$ vegetation. The mixed forest-grassland boundary is presently more than 1000 km NW of Hulu Cave. Thus, our data indicate that this boundary was much further SE during portions of the Last Glacial Period and that during this interval, the boundary passed over Hulu Cave many times in concert with millennial-scale climate changes that are likely at least hemisphere-wide in scale.\\\\ Y.J. Wang et al., Science 294, 2345 (2001).\\ K.-B. Liu et al., Quaternary Research 38, 32 (1992).\\ X. Sun et al., Marine Geology 156, 227 (1999).\\ Winkler and Wang, {\it in} Global Climates Since the Last Glacial Maximum, H.E. Wright, Ed., (U. of Minnesota Press, 1993), pp. 221-261.
DE: 3344 Paleoclimatology
DE: 4215 Climate and interannual variability (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting