Stories from the Field

A rare glimpse into the Ice Age

The recent discovery of well-preserved remains of Pleistocene mammal species, including the Columbian mammoth, American mastodon and giant ground sloth, together with extensive plant matter, insects and invertebrates, at an excavation site near Snowmass Village, CO is providing researchers with a unique opportunity to assess the role that climate and environmental change played in Pleistocene megafauna population dynamics.

This summer, Porinchu and Danielle Haskett, a UGA Geography Master's student, are planning to return to Colorado to collect additional sediment cores. This additional material will serve as the basis for Danielle's thesis.

Looking south from Independence Lake Pass, White River National Forest, CO

Looking south from Independence Lake Pass, White River National Forest, CO

Linkins Lake, White River National Forest, CO

Linkins Lake, White River National Forest, CO

Chironomid tubes in surface sediment core

Chironomid tubes in surface sediment core

Holocene sediment recovery using a modified Livingstone corer (East Humboldt Mountains, NV)

Holocene sediment recovery using a modified Livingstone corer (East Humboldt Mountains, NV)

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The recent discovery of well-preserved remains of Pleistocene mammal species, including the Columbian mammoth, American mastodon and giant ground sloth, together with extensive plant matter, insects and invertebrates, at an excavation site near Snowmass Village, CO is providing researchers with a unique opportunity to assess the role that climate and environmental change played in Pleistocene megafauna population dynamics. This exceptionally well-preserved Ice Age ecosystem, known as the Snowmastodon Site (SMS), is significant for a number of reasons. The site, which is located at 8,874 ft above sea level (asl), contains a relatively complete sequence of fossil bearing strata spanning approximately 100 ka (40-140 ka Before Present). Recovery of such a lengthy and diverse set of Pleistocene biotic assemblages is a rarity at high elevations because high elevation catchments are subject to erosional processes that typically limit the preservation of fossil records.

Led by the Denver Museum of Natural Science (DMNS), a large, multi-institution research group has been brought together to undertake a detailed, multi-disciplinary study of the SMS fossil locality. The development of quantitative estimates of past temperature is an integral component of the SMS project. David Porinchu, a new faculty member in Geography, is using sub-fossil midge analysis to characterize late Quaternary thermal conditions at the SMS. Midges have successfully been used to reconstruct late Quaternary thermal conditions in a wide variety of environments including the alpine, sub-arctic and arctic regions of North America and Eurasia. Reconstructing late Quaternary thermal conditions at the SMS will provide researchers with the means to relate changes in climate directly to observed changes in local flora and community composition and address questions related to ecosystem response to climate forcing during the previous interglacial and most recent glacial.

As a part of this project, this past summer, David led a research team in recovering lake sediment cores from 27 sub-alpine and alpine lakes in central Colorado. During sediment core collection, measurements of physical variables such as surface water temperature, specific conductivity and Secchi depth were made. The lakes sampled spanned an elevation range of ~ 900 m (~2900-3800 m) and capture significant elevation-dependent water temperature gradients. The uppermost 1 cm of surface sediment, which represents contemporary midge communities, will provide modern analogues for the older, fossil assemblages at SMS. These data will be used to develop of a midge-based inference models for mean July air and water temperature that will hopefully more fully capture the downcore variability of the SMS midge assemblages. These cores will be used to develop quantitative records of climate change and will provide some measure of the sensitivity of lakes in Inter-Mountain region of western United States to climate forcing during the late Quaternary.

More about David Porinchu

Porinchu, David

Associate Professor

Research Interests

biogeography, paleolimnology, paleoclimatology, water resources, climate change

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