Question

What are significant characteristics of sedimentary rocks?

Answer 1

Examples of sedimentary rocks are Basanite, Limestone, Coal, Sandstone, Novaculite and many more. The different features of sedimentary rocks are: They are deposited in layers as strata, forming a structure called bedding.

Answer 2

1) Sedimentary rocks are formed of sediments derived from the older rocks, plant and animal remains and thus these rocks contain fossils of plants and animals. The age of the formation of a given sedimen­tary rock may be determined on the basis of the analysis of the fossils to be found in that rock.

(2) Sedimentary rocks are found over the largest surface area of the globe. It is believed that about 75 per cent of the surface area of the globe is covered by sedimentary rocks whereas igneous and metamorphic rocks cover the remaining 25 per cent area. Inspite of their largest coverage the sedimentary rocks constitute only 5 per cent of the composition of the crust whereas 95 per cent of the crust is composed of igneous and metamorphic rocks. Thus, it is obvious that the sedi­mentary rocks are important for extent, not for depth in the earth’s crust.(3) The deposition of sediments of various types and sizes to form sedimentary rocks takes place in certain sequence and system. The size of sediments decreases from the littoral margins to the centre of the water bodies or sedimentation basins. Different sediments are consolidated and compacted by differ­ent types of cementing elements e.g., silica, iron com­pounds, calcite, clay etc.

(4) Sedimentary rocks contain several layers or strata but these are seldom crystalline rocks.

(5) Like igneous rocks sedimentary rocks are not found in massive forms such as batholiths, laccoliths, dykes etc.