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    Author(s): G.P. Juday
    Date: 1989
    Source: Gen. Tech. Rep. PNW-GTR-237. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 58 p
    Publication Series: General Technical Report (GTR)
    Station: Pacific Northwest Research Station
    PDF: Download Publication  (3.1 MB)


    The 2083-hectare Limestone Jags Research Natural Area in the White Mountains National Recreation Area of central Alaska contains old limestone terrain features––caves, natural bridges, disappearing streams, and cold springs in a subarctic setting. A limestone dissolution joint-type cave in the area is one of the largest reported in high-latitude North America. A Silurian limestone and an Ordovician volcanic and sedimentary sequence are in disconformable contact in the Research Natural Area (RNA); the limited stratigraphic break between the two units is evidence of a major drop in sea level caused by ancient glaciation. The tilted and faulted rocks within and near the RNA have been interpreted to illustrate the process by which Alaska was accreted to the geologic core of North America. A wind gap in the area marks a former stream channel through the White Mountains that was stranded after Fossil Creek captured the drainage through headward erosion. Groundwater released during the winter into Fossil Creek freezes into thick accumulations of aufeis. Limestone Jags RNA contains a rich diversity of habitats for vascular plants; the 303 species collected in the area represent nearly one-fourth of the flora of Alaska. Open, rocky limestone habitats support several plant species disjunct from the Rocky Mountains. A collection of the plant Draba fladnizensis in the RNA represents a marginal range extension from its previously known Alaska distribution. The only collection of the arctic moss Andreaeobryum macrosporum Steere & B. Murray south of the Brooks Range in Alaska is from the RNA. Alpine plant communities on basaltic rock in the RNA are especially lush and rich in lichens. An unusual form of open-canopied white spruce parkland occurs on dry limestone uplands. A closed-canopy, old-growth white spruce forest occupies productive bottomland sites of Fossil Creek. South-facing basalt slopes support a young paper birch and white spruce mixed forest that originated after a wildfire in the 1950's. The RNA includes important alpine habitat of the resident White Mountain caribou herd; it was part of the traditional calving area of the migratory Steese-Forty mile caribou herd until the early 1960's. Vertical limestone cliffs and pinnacles in the RNA provide escape terrain for an isolated population of Dan sheep and perching sites for raptors, including golden eagle and peregrine falcon. Rocky overhangs and abundant talus on steep limestone slopes of the RNA provide excellent escape terrain for the hoary marmot.A relatively uncommon songbird, the Townsend's solitaire, is found in the RNA.

    Publication Notes

    • Visit PNW's Publication Request Page to request a hard copy of this publication.
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    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.


    Juday, G.P. 1989. Alaska research natural areas: 2. Limestone jags. Gen. Tech. Rep. PNW-GTR-237. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 58 p


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    Alaska, aufeis, basalt, caribou, cave, cold spring, Dall sheep, disconformity, ecosystems, hoary marmot, limestone, Natural Areas (Research), natural bridge, old-growth forest, Research Natural Area, scientific reserves, Townsend's solitaire, windgap

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