Answer:
The two main processes responsible for porosity reduction in sedimentary rocks are cementation and compaction.
Cementation involves the precipitation of mineral matter in the pore spaces between sediment grains. As mineral matter precipitates out of the solution, it acts as a glue, binding the grains together and reducing the size of the pore spaces.
Compaction involves the compression of sediment grains by the weight of overlying sediment. As sediment becomes buried, the importance of the overlying deposition causes the sediment grains to pack more tightly together, reducing the size of the pore spaces between the grains.
Over time, these processes can reduce the porosity of sedimentary rocks, making them less absorbent and less able to store fluids.
Step-by-step explanation: