More than 100 prehistoric carvings have been discovered on rocks and boulders across the North of England.

The Neolithic art created 5,000 years ago bears a series of mysterious shapes, including concentric circles, interlocking rings and hollowed cups.

The finds, around Northumberland and Durham, are particularly exciting as many of the nation's prehistoric carvings have been lost to natural erosion and human activities such as quarrying and field clearance.

Although they are not in caves, many of the sites are barely accessible, accounting for their having lain undiscovered for thousands of years.

The most interesting discoveries include a large and elaborately carved panel found on a sandstone boulder on Barningham Moor, a remote 300m-high (984ft) area of Co Durham, on the edge of the Pennines.

It features abstract carvings — interlocking grooves and hollowed cups with surrounding circles. Tools of stone or bone were used to carve the symbols and the work is so well preserved that the “peck” marks are still visible. Near the boulder there appears to be evidence of clearance of fields for agriculture and burial cairns.

The discoveries were made as part of a four-year initiative funded by English Heritage, in partnership with Northumberland and Durham County Councils.

Kate Wilson, inspector of ancient monuments at English Heritage, said: “There are many theories as to what rock art carvings mean. They may have played a role in fire, feastings and offering activities, or been used as signposts, or to mark territory.

“They may have a spiritual significance. In hunter-gatherer communities those places where mountains touch the sky or the sea reaches the shore are often considered the domain of supernatural ancestors. Most rock art is found in those areas.”

Mrs Wilson said that, unlike the earlier hunter-gatherer period, the Neolithic Age saw “a fairly sophisticated culture”, with the introduction of agriculture: “They were settling and cultivating something. You find monuments such as stone circles and henges. Something's going on where society's changing. This is a story yet to be told.”

A hundred volunteers were trained by English Heritage to help to record and publish online all the prehistoric rock art discovered within the region. Carvings in inaccessible parts of the country can now be seen by the public. Richard Stroud, a volunteer who discovered the Barningham boulder, said: “There is a gulf of time and civilisation between the society that carved this stone and ours, its true meaning is something we will possibly never understand.”

About 2,500 rock carvings have been recorded in England so far. Carbon-dating is not possible with carvings, and dating is assessed by reference to quality and style and to associated finds or remains.

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