Describe the difference between clastic and organic sedimentary rocks.

Clastic sedimentary rocks: The word clastic came from “clasts” which means grains. Mainly silicic rocks like sandstone, shale etc. fall under clastic rocks. Organic sedimentary rocks: Sedimentary rockswhich are formed due to biogenic activity/processes or form fromorganic matter are called organic sedimentary rocks.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

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