For ten points, name this type of sedimentary rock known for both preserving fossils and trapping petroleum.
Deposited in slow moving water or tidal areas, it is brittle, easily cleaves, and often splinters into thin laminar sheets. The two most common varieties, mudstones and siltstones, consist of particles less than 16 micrometers in diameter, while heat and pressure transforms it into slate. For ten points, name this type of sedimentary rock known for both preserving fossils and trapping petroleum.
Deposited in slow moving water or tidal areas, it is brittle, easily cleaves, and often splinters into thin laminar sheets.
{shale}