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Site 21AN106          
Site Number(s):   21AN106  
County:   Anoka, MN  
City Township:   Columbus Twp.  
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Site 21AN106 is located in southeastern Anoka County. It lies on a former sand dune and overlooks two shallow lakes, Crossways (or Tamarack) and Rondeau (or Randeau), which are connected by Rice Creek. A volunteer working with the Institute for Minnesota Archaeology first recorded it in 1988.

 
 


Preliminary Investigation

 
 


In 1995 archaeologists from IMA Consulting relocated 21AN106 during a survey of the route for a pipeline proposed by Northern Natural Gas Company.

Excavators use a transit to record surface elevations across the site.
Excavators use a transit to record surface elevations across the site. The elevations were later used to create a contour map of the site area.

 
 



Three-dimensional site map of 21AN106 showing the location of 1996 excavation units
Three-dimensional site map of 21AN106 showing the location of 1996 excavation units.


By digging a series of shovel tests and three excavation units measuring 1 X 1 meters, they collected pieces of ceramics, stone tools and waste flakes, and fire-cracked rock (stones fractured during cooking or heating).
 
 




Preparing to Dig


On the basis of this information, Minnesota's State Historic Preservation Office decided that 21AN106 was eligible for listing on the National Register of Historic Places. Because the site could not be avoided during pipeline construction, Northern Natural Gas Company sponsored a data recovery excavation there in 1996. No license was required, since it was on private land and permission was received from the landowner. The work was conducted by IMAC.


Research Design


The project was designed to answer some key questions:

  • How old was the site?
  • What types of artifacts were present?
  • What sort of activities had occurred on-site?
  • How did the story of the people there relate to other sites in the area?
 
 






Data recovery would occur in two phases, and all investigation would be confined to the narrow strip in which the pipeline would be built.


View of 1996 excavations at 21AN106, facing east.
View of 1996 excavations at 21AN106, facing east.

 
 
 



Excavation and Data Collection


First, archaeologists surveyed the pipeline corridor with ground-penetrating radar, one of several geophysical techniques that are being used increasingly in archaeology.

 
 




The great advantage of this and similar remote-sensing techniques is that they allow archaeologists to identify important spots for excavation without disturbing larger portions of a site.


A technician pulls the ground-penetrating radar unit across the site.
A technician pulls the ground-penetrating radar unit across the site.

 
 



A laptop computer was used to record ground-penetrating radar data in the
A laptop computer was used to record ground-penetrating radar data in the field.



The ground-penetrating radar survey at 21AN106 found several places that appeared to be clusters of fire-cracked rock, which the archaeologists believed might be former fire hearths.

 
 



The second phase of the data recovery consisted of manual excavation of 30 square meters within the pipeline corridor. For three weeks in August 1996, archaeologists used shovels and trowels to dig units measuring 1 X 1 m.

The digging was in places where the radar survey had located potential features, or where the 1995 field work had indicated that artifacts were present in quantity.


Excavators use trowels to carefully unearth a cluster of fire-cracked rock.
Excavators use trowels to carefully unearth a cluster of fire-cracked rock.

 
 



Retouched blade excavated from 21AN106 in 1996. The tool is made from
Retouched blade excavated from 21AN106 in 1996. The tool is made from Hixton Quartzite, a material that was derived from bedrock deposits in west-central Wisconsin.



At least 18 different types of stone were used in making tools at 21AN106. Most of this stone could have been found near the site in bedrock or glacial deposits, but a few types came from southeastern Iowa, west-central Wisconsin, and west-central North Dakota.

 
 



Also found at the site were two pieces of obsidian (a black volcanic glass). The nearest source for this is in Yellowstone Park, Wyoming, a thousand miles west of 21AN106. Although we do not know exactly how these materials got to the Rice Creek drainage, it is likely that the people of 21AN106 traded with groups that either traveled to the source areas or in turn traded with others who had.

 
 




Archaeologists excavated over 55 pounds of fire-cracked rock. Some of this material was found in loose clusters that may have been fire hearths, but the rocks had been scattered through several thousand years of burrowing by animals. Because the soils of the site were very sandy, preservation of organic material was poor, and what little charcoal remained was badly decayed.


Small cluster of fire-cracked rock encountered during excavation of a 1-x-1-m
Small cluster of fire-cracked rock encountered during excavation of a 1-x-1-m unit.

 
 



Copper points like this one from 21AN106 have been found
Copper points like this one from 21AN106 have been found at other Middle Woodland sites in Minnesota. Drawing by Mike Beck.


There was a single copper spear point, made by rolling a flat piece of copper into a cone. Although some of the native copper used by precontact peoples was mined from deposits around Lake Superior, small, workable pieces also occur in the glacial deposits that cover the state.

 
 



Although no whole pots were found, there were more than 250 sherds, 20 from the rim area of vessels. They most resembled the St. Croix and Onamia types, which date to the late Middle Woodland period.

 
 



Interior surface of a ceramic rim sherd excavated from 21AN106 in 1996.
Interior surface of a ceramic rim sherd decorated by applying a cord-marked stick. Rims are especially useful because the form and decoration help to distinguish ceramic types.


Exterior surface of a ceramic rim sherd excavated from 21AN106 in 1996.
Exterior surface of a ceramic rim sherd excavated from 21AN106 in 1996. The surface has been decorated by applying a cord-marked stick and dentate stamp, forming patterns in vertical zones.

 
 



Crushed rock had been used for tempering. The sherds were 6-9 millimeters thick and had been decorated by applying patterns with sticks wrapped in twine, combs, or dentate stamps (a wide-toothed comb).


Analyzing the Data


Several of the ceramic sherds had a dark crust of food residue on their interiors -- remains of food that had been cooked in the vessels. Samples of this residue were analyzed to see whether opal phytoliths were present.

 
 




Most of them contained phytoliths from the chaff of wild rice, but two included phytoliths representing an unidentified wild grass. A single phytolith that could have been squash was present, and one of the samples unexpectedly contained corn phytoliths.


Corn phytolith, magnified 900 times.
Corn phytolith, magnified 900 times. No direct evidence that corn was used during Middle Woodland times had previously been found in Minnesota.

 
 



Possible squash or gourd phytolith recovered from food residue on a ceramic
Possible squash or gourd phytolith recovered from food residue on a ceramic sherd excavated from 21AN106 in 1996 (magnified 900 times).


Wild rice phytoliths recovered from food residue on a ceramic sherd
Wild rice phytoliths recovered from food residue on a ceramic sherd excavated from 21AN106 in 1996 (magnified 400 times).

 
 



Using accelerator mass spectrometry (AMS) a special type of radiocarbon dating that works on very small samples of organic matter, archaeologists dated the food residues. The wild rice had been eaten at some time between 2,150 and 1,875 years ago, but the corn was more recent. It was cooked between 1,750 and 1,450 years ago. The dates for wild rice were consistent with other Middle Woodland sites, but corn use at 21AN106 preceded the earliest known date by about 400 years. (This was obtained from a Late Woodland site near Mankato.)


What Was Learned


By analyzing the excavation results, archaeologists were able to address the research questions for the data recovery project.

  • Based on AMS dates, it appears that the site was occupied at least two times during the Middle Woodland period. There was no sign of year-round occupation, which would have included evidence for hunting, fishing, and other subsistence activities. Rather, it appears to have been a location where Middle Woodland peoples camped temporarily for a specific purpose.

  • The artifacts found, with fire-cracked rock and ceramics dominating the assemblage, suggests that 21AN106 was a processing site.

  • The presence of fire-cracked rock (associated with stone boiling) and St. Croix/Onamia ceramics, (types usually associated with intensified wild rice use in Minnesota), suggest that processing of wild rice was the main activity. Direct evidence for wild rice use there is provided by the phytoliths identified in food residues from the ceramic sherds. Based on the presence of phytoliths, it appears that the inhabitants also ate corn, squash, and other plants, but there is no evidence that these were grown at the site.

  • Finally, the location overlooking Rondeau Lake, where extensive wild rice beds still exist, suggests that this attracted Middle Woodland peoples to the area. It is likely that the site was used repeatedly on a short-term, seasonal basis. Wild rice is harvested during the late summer and early fall. Frequency of occupation was probably determined by the size of the wild rice crop in Rondeau and other lakes along Rice Creek. This may have varied with time because of local and regional environmental factors. Therefore, 21AN106 may not have been inhabited consistently over the years.

This site, like many others in the Rice Creek drainage basin was occupied during a period when lake levels were relatively high and wild rice would have been plentiful. In addition, other plant and animal resources would have been available, making the area a particularly attractive one to Middle Woodland peoples.

 
 
 


 

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Updated 09 Jul 1999