Holocene Climate, Fire and Vegetation Change Inferred from Lacustrine Proxies in the Tropical Andes, Laguna Yanacocha, SE Peru
Abstract
We present a 12,000-year long paleoenvironmental reconstruction from a small high-elevation lake in southeastern Peru. Climate and environmental change are inferred from chironomid species assemblages, charcoal abundance, size and morphology, and the abundance of some important pollen and spore types (Poaceae, Asteraceae, Isoetes). We employ a new chironomid training set developed for tropical South America (Matthews-Bird et al. 2016) to interpret shifts in chironomid assemblages. The sedimentary record from Yanacocha was first discussed by Beal et al. (2014), who reconstructed Hg deposition and measured metals, biogenic silica and loss-on-ignition through the Holocene. Additional downcore proxies are presented by Stroup et al. (this meeting). Yanacocha sits at 4910 m asl and less than 2 km from Quelccaya Ice Cap (QIC), but the lake's watershed has been topographically isolated from glacier meltwater since 12.3 ka. We compare our inferences from biological proxies with independent constraints on paleoclimate derived from published reconstructions of QIC fluctuations. Previous studies found that temperature was the primary driver of late Holocene fluctuations of QIC (e.g., Stroup et al. 2014), but records from the broader region indicate the Holocene also saw major changes in hydroclimate. Most modern precipitation at Yanacocha derives from the Amazon Basin to the east, and El Niño years are associated with drier conditions. Holocene sediments at Yanacocha likely thus record both changes in temperature and hydroclimate. Vegetation was sparse and no charcoal was preserved prior to 11.7 ka, whereas the early Holocene saw the highest overall pollen concentrations of the entire record and the onset of charcoal preservation. An increase in charcoal abundance, decrease in pollen concentrations, and shifts in vegetation and chironomid assemblages at Yanacocha suggest drier conditions from 9 to 3.5 ka, consistent with widespread regional evidence for early to middle Holocene aridity. One sample at 8.4 ka contains uniquely abundant charcoal, Poaceae and Asteraceae, possibly recording a brief (<500 yr) and uniquely dramatic dry event at that time. Shifts in chironomid assemblages, including a major shift centered on 1000 AD, indicate a variable climate through the late Holocene.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMPP21C2293A
- Keywords:
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- 1616 Climate variability;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 1637 Regional climate change;
- GLOBAL CHANGEDE: 1655 Water cycles;
- GLOBAL CHANGE