Paleorrota - Fossils of The Region

Fossils of The Region

In the area north of the geopark, dating from the Triassic and in the past consisted of rivers and lakes with oxygen and carbonate (alkaline) which facilitated the preservation of bones, but deteriorated easily the weakest parts of the plant and animal tissues. Only tree trunks with Permineralization survived into the rivers of Santa Maria Formation and Caturrita Formation.

Already the south is the area dating from the Permian, with the Rio do Rastro Formation and Rio Bonito Formation. Were composed of mangroves and swamps with acidic and anoxic waters that facilitated the preservation of fragile tissues such as leaves, seeds, pollens and spores. But easily destroyed bone.

The vertebrate fossils are found in reddish soil-like bedrock. Depending on the process of fossilization, they will have certain characteristics:

• Without Calcium carbonate the fossils will take on a white color and are easily dissolved in water.
• With Calcium carbonate the fossils will show the color of brown rust, and have the form of concrete because of the calcium carbonate. When a fossil has the ideal amount of carbonate, the fossil is undeformed, and does not dissolve in water. But excess of carbonate will deform the fossil, giving it a swollen appearance. If there is a very large quantity of carbonate, the fossil takes on a dusty outer surface which dissolves in water.

Another important feature is caused by slow creep. During the millions of years that the fossils have been embedded in the ground the slow creeping movement of the ground has created ripples in the fossils and given them a wavy appearance.

Most of the bedrock in the region is covered by soil. Only one percent of the bedrock is exposed in creeks, streams, lakes and roads.