This chapter is about the origin and distribution of sedimentary deposits (sediments and sedimentary rocks) with a focus on marine sediments.
The word “sedimentary” refers to materials consisting of sediments or formed by deposition; the word sedimentary also applies to both the processes and the products of deposition (Figure 6.1).
Sediment: Solid material that has settled from a state of suspension. Sediments are transported and deposited by water (rivers, lakes, and oceans), ice (glaciers), and wind.
Sedimentary rock is rock that has formed through the deposition and consolidation and solidification of sediment. Sedimentary rocks are often deposited in layers, and frequently contain fossils. Studies of sedimentary deposits can help tell the geologic history of an area.
Classification of Sediments and Sedimentary Rocks
Sediments (and sedimentary rocks) are classified in by origin of source material and by grain size.
There are 4 sources of sediments (and sedimentary rocks):
a) Cosmogenous: material that falls to the Earth surface from outer space.
b) Hydrogenous: material precipitated directly seawater.
c) Lithogenous: material derived from erosion of other rocks, typically from continental sources.
d) Biogenous: material formed from the accumulation of remains of living organism.