RANGE OF MEAN ANNUAL TEMPERATURES OF THE PAST ∼MILLION YEARS INFERRED FROM PROPERTIES OF RELICT PALEOSOLS AND PERIGLACIAL FEATURES, GLACIER PARK AREA, MONTANA

Particular kinds of soils and periglacial features form under particular climatic regimes. Thus, magnitude of past climate fluctuations can be estimated in areas where these features record environmental conditions significantly different from those of the present. Relict interglacial paleosols (less than a million years old based on paleomagnetic analyses) near Glacier National Park, Montana resemble fersiallitic soils (Paleudalfs, Palustalfs, and Paleudolls) of the southeastern U.S., where mean annual temperature (MAT) is at least 6 to 8°C warmer and mean average precipitation (MAP) is at least 40 cm greater than present climate in the Glacier Park area, where MAT is 4.2°C and MAP is 50 cm. Relict periglacial features in this area, including ice-wedge casts, record radically colder glacial conditions. Because active ice-wedges form in continuous permafrost where MAT is -6°C or less, their occurrence here suggests MAT in this area during full glacial conditions was at least 10°C colder than today. Thus, these data suggest that over the past ~ one million years, MAT fluctuated between -6°C or colder during full glacial conditions to 10 to 12°C or warmer during interglacials. Distribution of plant and animal fossils in mid-continental Eurasia and North America record a similar (extreme) range of average annual temperatures (at least 16-18°C or 29-32°F).