While a few of these rock carvings had been spotted previously, a new variety of them has piqued the interest of researchers, providing valuable insights into their origins.

Archeologist Jaime de Santana Oliveira highlighted the discovery on Monday and pointed out the presence of various distinct carvings.

One particular area exhibits polished grooves in the rock, believed to have been used by Indigenous inhabitants for sharpening their arrows and spears well before the arrival of Europeans.

"The engravings are prehistoric, or precolonial. We cannot date them exactly, but based on evidence of human occupation of the area, we believe they are about 1,000 to 2,000 years old," Mr Oliveira said in an interview.

The rocky spot, known as Ponto das Lajes, sits on the north side of the Amazon River, close to where the Rio Negro and Solimoes rivers meet.

Mr Oliveira said people first noticed the carvings there in 2010, but that this year's drought had been worse.

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The Rio Negro has gone down by 15 metres (49.2ft) since July, revealing large stretches of rocks and sand where there used to be no beaches.

"This time we found not just more carvings but the sculpture of a human face cut into the rock," added Mr Oliveira, who works for the National Historic and Artistic Heritage Institute (IPHAN) that oversees the preservation of historic sites.