Sedimentary processes
Sedimentary rock natures varies with difference of the grains origin, size, shape and composition. Grains and pebbles particles may be derived from the erosion of existing rocks or from volcanic eruption. Organism also contributes to sediments which varies from micro organism to reefs. These have calcium carbonate shells which rest at floors to make sedimentary rock, limestone. Sedimentary rock formation involves transportation which can be aided by any of the medium air, water, ice, gravity or chemical, biological growth of sediments at depositional site. Few factor influence the accumulation of sediments ultimate results on the formation of rock which are chemistry, temperature and biological characteristics of desired location. Transportation and depositional processes can be interpretted by looking at the sediments layers, their size, shape and distribution pattern gives knowledge of the processes of transportation. Sedimentary structures also proves the type of transportation medium example ripple marks. As present is the key to past so keeping this in mind physical, chemical and biological characters of the sedimentary rock can be examined to interpret the sedimentation process which resulted the formation of rock.
Sedimentary environment and facies
Every environment have its own characteristics either chemical, biological or physical. Studying these properties of the sedimentary rocks deposited and exposed on the surface reveals the secrets of environments at which they deposited. As an example of the fluvial environment, river base deposits will have gravely sandy material deposited while in floods on the banks of the river fine sediments will deposits providing habitat to vegetation. The channel will have lens of sand or conglomerate while the floodplain will have clay producing mud rock and sand at the base.
As every environment has own characteristic rocks so these are termed facies. Facies is a rock body with specific characteristics that reflects the condition under which it formed. For describing a facie its all characteristics as lithology, texture, sedimentary structures and fossil content are documented in order to fully interpret its environment of deposition.
