Which sedimentary rock contains fossils

We say that the rocks are deposited. The deposited rocks build up in layers, called sediments. This process is called sedimentation. The weight of the sediments on top squashes the sediments at the bottom. This is called compaction. The water is squeezed out from between the pieces of rock and crystals of different salts form.

There are many factors that can contribute to the likelihood of an organism being preserved as a fossil. Fossils are most common in limestones. That is because most limestones consist partly or mostly of the shells of organisms.

Sometimes, however, the shells are worn so much that they look like sediment grains rather than "real" fossils. Fossils are also common in shales, which form from muds. Excellent imprint fossils can be formed in fine-grained sediments like muds. Fossils, the preserved remains of animal and plant life, are mostly found embedded in sedimentary rocks. Of the sedimentary rocks, most fossils occur in shale, limestone and sandstone. Earth contains three types of rocks: metamorphic, igneous and sedimentary.

With rare exceptions, metamorphic and igneous rocks undergo too much heat and pressure to preserve fossils. So most fossils are found in sedimentary rocks, where gentler pressure and lower temperature allows preservation of past life-forms. Fossils become a part of sedimentary rocks when sediments such as mud, sand, shells and pebbles cover plant and animal organisms and preserve their characteristics through time.

Mud forms when larger rocks erode into tiny, usually microscopic, particles. These particles settle in the calm waters of lakes, swamps and the ocean, covering creatures that live there. Mud and clay combine with minerals and other particles over time to harden into shale.

The hard parts of the creatures covered with mud undergo preservation as fossils when consolidated with other materials inside the shale. Shale splits easily into layers to reveal any fossils inside. Fossils inside shale often include brachiopods, fossilized plants, algae, crustaceans and arthropods trapped in the hardened mud.

The very small mud and clay particles allow small details of organisms to be preserved, like the rare fossils of soft-bodied organisms found in the Burgess Shale. Dec 19, See below. Explanation: Well, as you know, there are three types of rocks. There are igneous rocks metamorphic rocks sedimentary rocks. Related questions What are sediments and how are they formed? How are sediments classified? What is an evaporite and how is it formed? How are sedimentary rocks different from igneous and metamorphic rocks?