Bosques Petrificados, Petrified forest national park in Santa Cruz, Argentina

Bosques Petrificados de Jaramillo is a national park in Santa Cruz whose surface is strewn with fossilized Araucaria trunks, some up to 30 m long and 2 m across. The logs lie on reddish-brown rocky soil among low shrubs, their surfaces banded in reddish brown, tan and pale gray, with jagged cracks splitting the stone layers.

The area was once covered by extensive forests during the Middle Jurassic period before volcanic eruptions and mineral-rich water sources altered the landscape. Over millions of years, these geological processes gradually converted wooden material into the stone formations visible today.

The fossil wood of Araucaria mirabilis was quarried by hunter-gatherers more than 10,000 years ago to make stone tools; workshops, base camps and burial sites from these groups lie in the park. Visitors can also see Cerro Madre e Hija, an extinct volcano that rises above the fossil beds.

The park entrance is reached from Jaramillo and Fitz Roy, about 140 km north of the fossil site, via National Route 3 and Provincial Route 49. Trails cross open ground with direct sun and strong westerly winds. Carry water and sun protection; the plateau offers little shelter and temperatures swing from 40 °C in summer to −15 °C in winter.

Many visitors overlook the range in conditions across the logs, with some fully exposed and others still partly buried in the ground. These varying degrees of exposure reveal how different erosion patterns have affected each petrified specimen over time.