By noting differences in spear point and arrowhead shape among the different occupational zones at Twin Knobs Rockshelter, investigators determined when and for how long Native peoples had lived there. Native flintknappers made each point from local chert and had resharpened most of them several times.
Below is a summary of the changes in point shape observed for Twin Knobs Rockshelter - starting with the most recent examples from the uppermost levels. The accompanying photograph illustrates these changes.
Mississippian - Light-colored Point at Top Left
Arrowheads mark the final occupation of the rockshelter. This point is triangular in shape and has a straight base. Like all arrowheads, it lacks a stem.
Late Woodland - Dark-gray Point to the Right and Below Mississippian Point
This spear point is small to medium-sized and triangular in shape. It has straight corners with straight edges, an expanding stem, and a straight base.
Early Woodland - Large, Light Tan Point Below and Left of Late Woodland Point
This spear point is medium-sized and has a distinctive contracting, rounded stem. It is lanceolate to triangular in shape with sloped corners.
Late Archaic - Two Points Below Early Woodland Point
These points are triangular in shape, have straight to barbed corners with straight edges, and convex bases.
Early Archaic - Next Four Points Below Late Archaic Points
These spear points are large to medium-sized. They are triangular in shape, corner notched, have barbed shoulders, straight to flared shoulder edges, and expanding stems.
Late Paleoindian - Bottom Two Points
Archaeologists recovered these spear points from the deepest deposits. They have concave bases, are medium to large in size and are lanceolate-shaped. The specimen on the bottom left probably broke while while being made.