Which of the following is/are correctly matched? Mechanism/Process : Rock 1. Mechanically formed sedimentary rock : Sandstone 2. Organically formed sedimentary rock : Dolomites 3. Chemically formed sedimentary rock : Shale Select the correct answer using the code given below:

[A] 1 only

[B] 1 and 2 only

[C] 2 and 3 only

[D] 1, 2 and 3

Answer: B

Notes:

Sedimentary rocks are formed by the accumulation of sediments. There are three basic types of sedimentary rocks.

Clastic sedimentary rocks such as breccia, conglomerate, sandstone, siltstone, and shale are formed from mechanical weathering debris.
Chemical sedimentary rocks, such as rock salt, iron ore, chert, flint, some dolomites, and some limestone, form when dissolved materials precipitate from solution.

Organic sedimentary rocks such as coal, some dolomites, and some limestone, form from the accumulation of plant or animal debris.

Source: G C Leong