Stable Isotopes of Subfossil Bat Guano as a Long-Term Environmental Archive: Insights from a Grand Canyon Cave Deposit

• Published in: Journal of caves and karst studies Vol. 72; no. 2; pp. 111 - 121
• Main Authors: Wurster, Christopher, McFarlane, Donald, Bird, Michael, Ascough, Philippa, Beavan Athfield, Nancy
• Format: Journal Article
• Language: English
• Published: 01.08.2010
• Subjects: USA, Arizona, Grand Canyon
• ISSN: 1090-6924
• DOI: 10.4311/jcks2009es0109

We investigated the utility of subfossil bat guano as a paleoenvironmental archive by comparing elemental ratios and delta super(13)C, delta super(15)N, and delta D values of various simple extracts from bulk material. Solvent-extracted guano yielded consistent C:N and N:H ratios, and delta super(13)C values of solvent-extracted guano exhibited strong covariation with delta D values, as well as with the delta super(13)C values of other simple extracts (bulk guano, bulk lipid). The results suggest that reliable records are easily recovered for delta super(13)C, and also indicate that delta super(15)N values may have utility as a paleoenvironmental archive. Despite coeval delta super(13)C values of bulk guano and solvent-extracted guano, super(14)C ages of the different fractions did not always yield similar ages, indicating that future refinement of a suitable extraction protocol is required. Applying these protocols to an ancient bat guano deposit allowed us to infer that climate at the Grand Canyon during the late Pleistocene was more variable and generally cooler and wetter, relative to Holocene climate. We conclude that guano deposits are an underutilized, yet powerful continental paleoenvironmental archive of climate change for semi-arid and tropical regions.