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A variety of invertebrate organisms live and feed within the soft sediment accumulating under water. The activity of these organisms, known as bioturbation, can leave traces in the sediments of the substrate. These traces can become fossilized, as is the case for this Cretaceous sandstone from the coast of Chile. The meniscate patterns in the sand are indicative of bioturbation. Surface view of bed, pencil for scale.
The distinctive linear patterns observed on the surface of this sandstone bed are trace fossils produced by crustaceans as they were moving in the originally loose sediment. The technical term for this type of biogenic structures is bioturbation. Photo taken on a sandstone slab at the Varvito Park, Ito, Brazil, with exposures of Permian strata from the Itararé Group.
Burrows, Dinosaur Ridge, west Denver --- These tubes are assumed to be traces of animals that formed burrows on the surface of underwater sediment.