Great find. How can they tell the age?
I went on a website and looked for an arrowhead similar to this one from the Midwest. The closest I could find was one called a Burroughs found in Missouri.
The shape is a "lanceolate" A leaf design.
I found the most similar one to be called a burroughs. It is listed as from the early archaic period. The period is from 2,000 to 10,000 bc. I would guess early is 5,000 bc or older. I am just guessing. I plan to take it to the archeologist at the wildlife refuge headquarters.
Looking at it, it makes sense it is an ancient one as it is not a refined design. The part where it would connect to the spear is very primitive.
I have looked at others but this looks most like it. I am learning a lot about arrowheads in last 12 hours. I find it interesting. The problem with it is the map shows them being found in Mo. Ks, Ne and southern Ia. and not from here.
I looked up the climate and Vegetation here around 5,000 BC. We were emerging from tundra and retreating Glaciers, (Global warmer was raising its ugly head) The water levels were higher here then they are now. The tamarack swamp surround my house was most likely open water. The area where our house is and the high point in the area. The swamp was most likely a lake that was part of the river. There is a few small "creeks' Through the swamp still that connect to the river.
Granted this is all conjecture on my part, and could be complete BS. The internet is great for looking this kind of stuff up, but sometimes it is bunk.
Here is the website I found the arrowhead stuff on. If you look and find one more like this one, Please let me know. It bothers me there have been no others like this one found, or reported to these sites. I will spend the day when company is not here researching it more.
http://www.projectilepoints.net/Search/NorthCentral_Lanceolates.html