The depth of the sample was apparently the OP's clue that the seed was ancient. Perhaps the seed is petrified.
As you can imagine, identification of a plant to species from a seed, let alone from an ancient seed, is an esoteric science and the realm of experts.
Look around. What is growing around where you found the seed? What has grown there historically? Is there a common plant in the area that has the same seed?
In taxonomy, similar species are grouped into families. "Sunflower" is the common name of the family of plants - the Asteraceae, that is also the common name for the seed snack from that family.
I have no idea what you might have found, but the seed reminds me of the castor bean seed, which is a Euphorbicaceae family plant.
But your seed is striped and not mottled and castor bean seeds are larger.
The USDA has a seed ID website:
Family Guide for Fruits and Seeds
There is a weed seed ID key called LUCID but it wasn't working on my web browser, but just from the pages you can read, you can get an idea of how esoteric the science is -
Federal Noxious Weeds Identification Tool
I don't think your seed is a grass seed, as grass seeds are very distinctive. Grasses are monocots and it appears that your seed is a dicot or a two leaved seedling flowering plant
Usually the larger state dept's of agriculture, the USDA, or your local natural history museum, or university will have the experts (the PhDs) who can really id your seed. Depts of agriculture verify the purity of seed for sale and the identity of noxious weeds from seed.
I think the circle of people that would be interested in your seed find is pretty small - those scientists, including anthropologists, who study Adena culture or fossil or heritage plants.