Stable carbon and hydrogen isotopes from bat guano in the Grand Canyon, USA, reveal Younger Dryas and 8.2 ka events
Abstract
We inferred climate change through the Pleistocene-Holocenetransition from <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">13C and <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">D values of bat guano deposited from14.5 to 6.5 ka (calendar ka) in Bat Cave, Grand Canyon, Arizona.The <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">13C and <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">D values generally covaried, indicating that regionallate Pleistocene climate was relatively cool and wet, and earlyHolocene climate gradually became warmer with increased summerprecipitation until ca. 9 ka, at which time the onset of modernNorth American Monsoon-like conditions occurred. Duringthe Younger Dryas event, <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">13C values decreased, whereas <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">D valuesincreased, indicating a cool and possibly drier period. We alsoobserved a distinct isotopic anomaly during the 8.2 ka event,at which time both <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">13C and <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">D values decreased. The <IMG SRC="/math/delta.gif" ALT="{delta}" BORDER="0">13C valuesabruptly increased at 8.0 ka, suggesting a rapid change in atmosphericcirculation and greater influence from convective storms originatingfrom the south. Deposits of bat guano represent a largely untappedsource of paleoenvironmental information that can provide continuousand long-term continental archives of environmental change.
- Publication:
-
Geology
- Pub Date:
- September 2008
- DOI:
- 10.1130/G24938A.1
- Bibcode:
- 2008Geo....36..683W