Which sedimentary environments are commonly associated with sandstone, limestone, and shale?

• A. Sandstone in desert dunes; Limestone in reefal, shallow marine; Shale in quiet offshore or lake.
• B. Sandstone in beach/river/aeolian; Limestone in shallow marine/reef; Shale in quiet offshore or lake.
• C. Sandstone in glacial moraines; Limestone in deep ocean trenches; Shale in fast rivers.
• D. Sandstone in coral reefs; Limestone in dunes; Shale in volcanic ash beds.

Answer: (B)

Sedimentary rocks reflect the energy of the environment where they form, and grain size is a clue to that energy. Sandstone forms from sand-sized grains that settle in higher-energy settings such as beaches, rivers, and wind-driven deserts (aeolian). Limestone accumulates in shallow, warm marine areas and reef systems where calcium carbonate from organisms builds up. Shale comes from very fine clay and silt that settle only in calm, low-energy waters like quiet offshore basins or lakes. So the best match is sandstone in beach, river, or aeolian settings; limestone in shallow marine or reef environments; and shale in quiet offshore or lake settings. Other options mix environments that don’t align with how these rocks typically form.