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Some concretions have a central particle, such as a fossil, that triggered the cementation. Others have a void, perhaps where a central object dissolved away, and others have nothing special inside, maybe because the cementation was imposed from outside.
Most often, the fossils in concretions are simply skeletal debris, but there are a few exceptional sites where the concretions contain many and various highly detailed, three-dimensional fossils of soft-bodied animals. These include a few of the most famous fossil sites in the world, three examples of which are outlined below.
3 Απρ 2020 · Below we introduce the major types of concretions and similar rocks, as well as share images of concretions that were sent to us by the public and often initially mistaken for various types of fossils.
18 Μαρ 2013 · Carbonate concretions are common features of sedimentary rocks of all geological ages. They are most obvious in sandstones and mudstones as ovoid bodies of rock that protrude from natural outcrops: clearly harder or better cemented than their host rocks.
Trace fossils can be grouped into several major types of structures based on what the organism was doing: Bioturbation structures record disruption of bedding by burrows, tracks, and trails. Bioerosion structures record erosion of substrate by boring, scraping, or biting.
Explore the Atlas of Trace Fossils, featuring burrows, tracks, and trails that reveal ancient animal activities in sedimentary environments.
Trace fossils. Trace fossils (sometimes also called ichnofossils) provide evidence about the movements and/or activities of ancient organisms, but not necessarily about their appearance. There are three major types: Movement traces. Predation traces. Digestive traces.
