An annual-resolution record of deglacial hydroclimate from Hulu Cave, China
Abstract
Stalagmites (carbonate cave formations) from Hulu Cave in eastern China have proven to be an extraordinary source of paleoclimate information. Their multidecadal-resolution d 18O records are interpreted as proxies for the local strength of the East Asian Monsoon and have been used to test and verify critical hypotheses related to the influence of insolation on global climate, trans-hemisphere atmospheric teleconnections, and abrupt climate change. In parallel, Hulu stalagmites were the testbed for continued development of U-Th geochronology in carbonates, resulting in a remarkable climatological chronometer that - in combination with other Chinese stalagmites - acts as a continuous 640 ky backbone for the age model of many paleoclimate proxy records. As a result, well-characterized Hulu stalagmites are ideal targets for novel analytical methods with high-reward potential.
Here, we report an annually-resolved record of d 18O measured by secondary ion mass spectrometer (SIMS) across Hulu stalagmite H82. At the UW-Madison WiscSIMS lab, 10-m m-diameter d 18O analyses were placed using images of fluorescent banding in H82 collected by confocal laser fluorescent microscopy. The bands, which repeat every ~20-40 m m, are interpreted to be annual. More than 4,000 d 18O analyses - with at least one analysis per band - span a 17 cm traverse across the sample, which includes 92 U-Th ages from 16.5-11.0 ka. New methods at WiscSIMS allow for unattended, automated spot-sampling at locations that are pre-determined off-instrument in a micro-spatial reference frame constructed in the open-source QGIS software. This protocol increases the sample analysis rate to ~400/24 hr, making analysis of a multi-millennial timeseries feasible. The resulting d 18O record reveals structure that is averaged in the mm-scale, drill-sampled timeseries. The SIMS record has a range of 7‰ vs. 4‰ in the drilled record. Combined with the exceptional age model for H82, our record provides a valuable reference of past hydroclimate variability and further characterizes short-lived and abrupt hydroclimate changes across the last deglaciation. As examples, we highlight the Younger Dryas/Holocene transition and Preboreal Oscillation(s). Partially supported by U.S. NSF Grants 1702816, 1702407, 1603065, 1658823 and the 111 project of China (D19002).- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP44B..08O
- Keywords:
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- 1009 Geochemical modeling;
- GEOCHEMISTRY;
- 4914 Continental climate records;
- PALEOCEANOGRAPHY;
- 4924 Geochemical tracers;
- PALEOCEANOGRAPHY;
- 4994 Instruments and techniques;
- PALEOCEANOGRAPHY