Environmental interpretation of fossil insect assemblages from MIS 5 at Ziegler Reservoir, Snowmass Village, Colorado

Scott Elias

Research output: Contribution to journalArticlepeer-review


Organic-rich lake sediments from a trench exposed at Ziegler Reservoir fossil site near Snowmass Village, Colorado yielded a sequence of 27 insect fossil assemblages, spanning the time interval from about 125 to 77 ka. The assemblages appear to represent MIS 5e, 5c, 5b, and 5a. A total of 99 taxa were identified, mostly beetles. The fossils represent the oldest known Pleistocene insect faunas from high elevation in the Rocky Mountains, and document a
series of climatic oscillations from full interglacial to stadial and interstadial environments, accompanied by changes in regional biological communities. The MIS 5e fauna indicates summer temperatures similar to modern values, with winter temperatures 5–7 °C cooler than today. Regional climates cooled somewhat by MIS 5c, and during MIS 5b summer temperatures were 5–6 °C colder than modern values. Summer temperatures recovered to near modern
levels during early MIS 5a, and cooled by 1–2 °C at its end, although winter temperatures were apparently abovemodern levels. The indication of milder but wetter winters, strengthened by the inclusion of species found today only in the Pacific Northwest region, suggests conditions that may have led to increased snowpack at high elevations in this part of the Southern Rockies, linked with the onset of MIS 4 glaciation.
Original languageEnglish
Pages (from-to)592-603
Number of pages11
JournalQuaternary Research
Publication statusPublished - 20 Nov 2014


  • Late Pleistocene, Insect fossils,Ziegler Reservoir, Colorado

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