A first step in lithification is burial of the sediment, followed by a process of compressing the clasts (such as sand or clay) together. What is this called

Weathering

Explanation:

Weathering is a process of break down of parent rock into sediments by agents like water, wind, or any other agent.

The lithification can be defined as the process of formation of the soil into the sedimentary rock. In this process the parent rocks first get weathered and loose soil particles form sediments. Then compaction of sediments, cementation and recrystallization of minerals occurs in the soil.