Why could sedimentary rocks have bits of fossils and decaying plants and animals in them?
Answers
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Sedimentary rocks have been derived from deposition of organic material (e.g. coal) or siliciclastic material (e.g. sand) (minerals and aggregates of rocks (metamorphic, magmatic, sedimentary) , called lithoclasts). These fragments originated from weathering, erosion and transport by water, wind and ice or simple mass wasting. Bioclastic rocks have been derived from biogenic material. Depending on the transport distance the grain size may range from gravel to clay. There are sedimentary rocks which formed immediately on top of the parent material called residual deposits which may grade directly into the topsoil (see pedology). Apart from siliciclastic rocks, there are chemical sediments (organic and biogenic). This rocks may be altered during diagenesis ,e.g. cementation under temperatures and pressure below the metamorphic grade