It contains around 50 objects, including necklaces, bracelets, and clothing pins.
“I first thought it might be a lamp,” said cartographer Thomas Karlsson, “but when I looked closer, I saw it was old jewellery.”
According to Swedish archaeologists, finding such a hoard in a forest is very unlikely.
Such gifts were typically left in rivers or wetlands by ancient tribes.
The hoard was located on the forest floor, among bricks.
It is thought that one or more animals had disturbed the earth, leaving the many items semi-exposed. They have been dated to the period between 750 and 500BC.
Karlsson said he had spotted the metallic glint while looking down at a map he was working on. At first he thought the ornaments were copies, as they were in such good condition. Then he emailed a local archaeologist while having a coffee in the forest, regional newspaper Goteborgs-Posten reported.
The forest is near the town of Alingsas, about 48km northeast of Gothenburg.
Archaeologists describe it as a “depot” find – that is, a hoard deliberately left as an offering to a god or gods, or to invest in life after death.
The jewellery “is extremely well preserved”, a lecturer in archaeology at Gothenburg University, Professor Johan Ling said.
“Most of the items can be linked to a woman, or women, of high status,” he said, quoted by Goteborgs-Posten.
The treasure includes a type of rod used to spur on horses, previously found in neighbouring Denmark, but not in Sweden.
Treasures turned over to state
Swedish law requires anyone finding such antiquities to notify the police or local authority, as they are regarded as state property. The Swedish National Heritage Board then decides what reward, if any, the finder should receive.
Karlsson said a reward “would be a nice bonus, but it’s not very important to me.
“It’s fun to be a part of exploring history. We know so little about that era, because there are no written sources.”
In Scandinavia the Bronze Age ran from about 1700BC to 500BC, when it gave way to the Iron Age. The Iron Age continued until about AD800, when the Viking Age began.
Pernilla Morner, an antiquities expert for Vastra Gotaland region, said that “not since the bronze shields from Froslunda were excavated from a field in Skaraborg in the mid-1980s has such an exciting find from the Bronze Age been made in Sweden”.
VGRfokus, a news site for Vastra Gotaland, says a team of Gothenburg archaeologists is now investigating the site in detail.