We sometimes seem to divide earthworks and stone structures into two groups - ancient and modern. That is where we stumble because we ignore the fact that earthworks and stoneworks continued to be made right through the Roman occupation, the so called Dark Ages, medieval, industrial and modern ages. A "stone row" and a "round barrow" could be medieval or the remains of miners sheds and spoil tip. Dating anything older than a century or so by looking at weathering and soil deposits requires expert knowledge.

The first thing to ask yourself when discovering an unknown ancient site is simply "Why is it unknown?" Why has nobody recorded it as an ancient site already? Is it really so obscure and so remote that it has remained undiscovered? Check out the local history and see what was going on at that spot in historical times. What does the local arhaeological/historical society have to say about it? By eliminating other known later structures, you may then be able to approach the local archaeology unit with more confidence.