Great Oasis

by Mark L. Anderson
Illustrations by Mary Slattery
 and Rick Friday 
© Copyright 1998 The University of Iowa. All rights reserved.

Great Oasis Map
The Great Oasis culture was initially defined and described on the basis of excavations conducted by Loyd Wilford during the late 1940's at the Low Village site in southwestern Minnesota. The name Great Oasis is derived from Joseph Nicollet's description (1837) of a large wooded area of southwest Minnesota that was protected from prairie fires by a complex of adjoining shallow lakes. One of the largest lakes in this region is named Great Oasis Lake and it is on the north shore of this lake that the Low Village site exists. The Great Oasis culture extended across a broad region of the eastern Plains periphery including southwestern Minnesota, northeastern Nebraska, southeast and central South Dakota and northwest and central Iowa. Many Great Oasis sites in central Iowa are located in the valleys of the Des Moines and the Raccoon rivers, suggesting that an extensive population of Great Oasis people once inhabited that region. Based on recent excavations, the "Maxwell phase" was defined to include the Great Oasis of Central Iowa. Extensions into central South Dakota appear to be primarily restricted to the valley of the Missouri River. Several Great Oasis sites have been recorded along the Missouri and its tributaries in northeast Nebraska with one site being discovered on the Loup River in the east-central part of the state. A sizable amount of information regarding the Great Oasis culture in northwest Iowa was produced as a result of studies conducted for a proposed reservoir in the Perry Creek drainage basin, located approximately 5 miles (8.1 km) northwest of Sioux City. 

Great Oasis semi-subterranean house structure
The Great Oasis, (AD 900-1100) culture is associated with both the terminal Late Woodland period and the Initial Middle Missouri periods. Their subsistence system included intensive hunting, collecting, and fishing. Excavations also revealed evidence of a diverse agricultural system including corn, chenopodium (goosefoot), sunflower, little barley, and sumpweed, and other indigenous species such as smartweed, wild plum, hackberry, and walnut.

Site locations are typically on the first or second terraces along rivers and streams, and in Minnesota can be found on shores, peninsulas, and islands of shallow lakes. Sites contain hearths, storage/trash pits, and large semi-subterranean house structures as evidenced by excavations at the Broken Kettle West site (13PM25) and the Maxwell site (13DA264). The Great Oasis settlement system may represent a seasonal pattern characterized by concentrated winter occupations of semi-subterranean earth lodges and dispersed summer occupations of both flood plain farming stations and mobile hunting camps. Great Oasis cemeteries appear to be located on hill or bluff tops away from the living areas, although human skeletal remains are sometimes recovered within settlement sites. 

Lithic assemblages are usually comprised of chert, chalcedony, and quartzite. Projectile points are typically triangular unnotched and side notched. Other lithic tools are similar to those of other Late Woodland and early Plains Village cultures. Some of the lithic raw material derives from distant sources such as Knife River Flint from western North Dakota and Burlington chert from southeastern Iowa suggesting developed trade networks. This conclusion is supported by discovery at Great Oasis sites of Lithasia and Leptoxis (formerly Anculosa) shells from the Ohio River valley. Bone tools also occur and include needles, awls, spatulas, quill flateners, and scapula hoes made from large mammal bones. 

Great Oasis High Rim
Great Oasis Wedge Lip

Great Oasis High Rim (left) and Wedge Lip (right).

Probably the most distinctive Great Oasis artifacts are the ceramics. They are divided into two main wares: Great Oasis High Rim and Great Oasis Wedge Lip. Both forms are typically well made, globular jars with rounded bottoms and shoulders, constricted necks, and outflaring rims. High Rims are generally parallel sided with flattened lips. Wedge Lip rims are short and thickened with flat lips that are steeply beveled toward the exterior. Decorative motifs are typically restricted to the rims and include fine trailed lines, oblique lines, elongated punctate impressions, tool impressions, or cross-hatched trailing. Additional motifs typically found on High Rim vessels include triangles, diamonds, pendant triangles, trapezoids, pendant chevrons, and occasionally upright or inverted turkey tracks, stylized maize and tree motifs, and stylized deer motifs. Great Oasis vessels are typically 4-6 mm thick, smoothed to smoothed over cord marked, grit and sand tempered, and manufactured with paddle and anvil modeling with subsequent smoothing. The end of Great Oasis in northwest Iowa coincides with the appearance of Mill Creek culture.In central Iowa, sites were apparently abandoned, and there is no subsequent occupation until the appearance of Oneota. 


Suggested Reading

Alex, Lynn
1980 Exploring Iowa's Past: a Guide to Prehistoric Archaeology. University of Iowa Press, Iowa City.

Anfinson, Scott F.
1997 Southwestern Minnesota Archaeology: 12,000 Years in the Prairie Lake Region. Minnesota Prehistoric Archaeology Series No. 14. Minnesota Historical Society, St. Paul.

Henning, Dale and Elizabeth Henning
1978 Great Oasis Ceramics. In Some Studies of Minnesota Prehistoric Ceramics, edited by A. R. Woolworth and M. A. Hall. Occasional Publications in Minnesota Anthropology, No. 2. Minnesota Archaeology Society, St. Paul.

Tiffany, Joseph A.
1983 An Overview of the Middle Missouri Tradition. In Prairie Archaeology: Papers in Honor of David A. Baerries, edited by Guy E. Gibbon. Publications in Anthropology, No. 3. Univeristy of Minnesota, Minneapolis.

Zimmerman, Larry J.
1985 Peoples of Prehistoric South Dakota. University of Nebraska Press, Lincoln.