igh above the banks of the Assabet River, amid the wooded hills in the southernmost tip of Acton, arch eologists have found traces of an ancient Native American civilization that dates back as far as 7,000 years, to 5,000 BC.
Duncan Ritchie, the senior arch eologist for the Rhode Island-based Public Archaeology Laboratory, said the discovery of thousands of Native American artifacts excavated from the site, called Pine Hawk, includes fragments and bits from stone tools, arrow heads used for spears, hearths and fire pits, storage and refuse pits, workshops where stone tools were made, and post molds for housing circles.
The site, which existed at the time of the ancient Egyptian civilization when the pyramids were built, ''is considered one of the most significant discoveries of ancient Native American culture on the Eastern Seaboard,'' said Acton's Bob Ferrera, the founder of the ad hoc committee, Friends of Pine Hawk. The Acton-based group was created last summer to promote public awareness of both the arch eological and human history of Pine Hawk.
Now Ferrara and others want to spread the word about the discovery and the ancient civilization that used the tools and weapons. They are hoping to offer a local library exhibit to display some of the artifacts and to develop a school curriculu m about the Native Americans who left the items behind.
Though the dig was conducted three summers ago, details of the Pine Hawk discovery were made available only recently because the site was registered as a historic property by the Massachusetts Register of Historical Places, with an edict that requires that information about such places not be made public until fragments from the site are excavated and studied.
Pine Hawk was discovered quite by accident five years ago when Acton began planning to build a waste-water treatment plant along the Assabet River. Before digging or construction could begin, an arch eological survey had to be completed as part of the planning process, as required by law on construction projects, such as Pine Hawk, that use federal or state funding.
During the survey, the Public Archaeology Laboratory, led by Ritchie, started digging for test bits and found small flakes of stone used in tool-making. Ritchie said this discovery led to further investigation and excavation, which uncovered thousands of chipping debris pieces and projectile point fragments that were implanted as arrow tips on spears. In addition, several fire pits were uncovered 4 feet deep in the soil. The pits had traces of charcoal indicating that they were used between 3,900 and 4,600 years ago.
Since it was not possible to relocate the proposed treatment plant and preserve the Pine Hawk site in place, the arch eologists mounted a program to retrieve the fragments for analysis.
Ritchie said a study of the fragments followed with radio carbon-dating tests at a Florida laboratory indicate that the area was occupied by an ancient Native American culture 7,000 years ago in the post-glacial period.
The Assabet River served as a navigable transportation route from the Merrimack, Concord, and Sudbury rivers, and a place with rich natural resources where Native Americans could fish, hunt, and collect plant food. Pine Hawk provided easy access to fresh water, transport, as well as good drainage and soft soil. It also faced south - which provided more sunlight during the day.
''The amazing thing about the fragments is that they weren't buried; they were left on the ground, and time has added more and more material over them,'' said Doug Halley, a Friends of Pine Hawk member and Acton's Board of Health director. ''It's hard to believe that over a period of 4,000 years, almost 4 feet of it has fallen on the ground.''
Added Ferrera: ''It works out to be that about an inch of soil is built up per century, or approximately a foot per each millennium. The process is similar to reading tree rings to determine their age.''
