Answer: organic sedimentary rock
Organic sedimentary rocks are particular type of sedimentary rocks that contains more than 3% of the organic carbon. These rocks are characterized by the uniform dark color, occurrence of bitumen, asphalt, tar, petroleum and carbonaceous materials. These rocks are the reservoirs of fossil evidences. These rocks preserves fossils when the fully or partially degraded fossil evidences are covered by a heap of weathered strata which get compacted due to heat and pressure underneath.