Reading the Rock Record

Sedimentary rocks are rocks made of particles cemented together. They can be particles of other rocks like sandstones, clay and mudstones, particles made by living organisms as limestones are, or particles deposited chemically like salts and other evaporites.

By looking at physical attributes of the sedimentary rocks you can tell something about the energy of the environment, climatic conditions, source of the sediments, how they were transported. Fossils in the rock record living creatures, ecological relationships, chemical conditions. Correlating layers localy, regionaly and in the end on a global basis, a relative time scale was established. Paleomagnetic data and chemical isotopes can also be correlated to put together a picture of continental configuration, paleoclimate and ocean chemistry.

The photo above was taken in Glacier National Park in Montana, USA. The ripple marks here in this case tell you the sediments were washed by waves going in two directions. The red colour indicates the sediments were exposed to the air so that iron oxidized.