Campaigners opposing plans for quarrying near an ancient monument in North Yorkshire must wait until the New Year for a decision by councillors.
Each henge consists of circular earth banks and ditches
Tarmac has applied to quarry sand and gravel at Ladybridge Farm, north of Ripon, near Thornborough Henges.
Opponents fear it could destroy clues about the 5,000-year-old earthworks' history but Tarmac says the land could cope with quarrying and conservation.
A decision was deferred on Tuesday to await a full report in January.
On Tuesday North Yorkshire County Council issued a statement saying: "Today's meeting has decided to defer this matter to allow a further archaeological investigation to be carried out.
"We hope to have a full report for members to consider in January."
Members of the North Yorkshire County Council planning board had visited the site in August and were recommended to refuse permission by planning officers.
The henges are believed to be one of Britain's largest ritual gathering places from the Neolithic period.
The henges are in open countryside near the A1
Local campaign group Timewatch has collected a petition of more than 10,000 signatures against the plans which would see work about half a mile away from the henges.
It said the quarry would contribute to the permanent loss of nationally important archaeology.
US-based conservation group the Landmarks Foundation has also voiced its concern at the quarry proposals, describing them as a tragedy.
But several people have expressed their support for the quarry extension.
Tarmac already has a quarry at Nosterfield, close to the ancient henges which consist of three earthworks built in a line running north-south for about a mile.
Workers at the Nosterfield Quarry and local building firms have sent in 80 letters and a 350-signature petition arguing that more than 50 livelihoods depend on the application's approval.
Tarmac has said the extension is on farmland where there is only "thin and scattered" evidence of prehistoric activity, according to a recent study by archaeological consultants.
The actual henges are under no threat from quarrying because of their status as protected ancient monuments, the company added.