6: Sediments and Sedimentary Rocks (Exercises)

Q6.1 Describe the sediment on a beach

Responses will vary

Q6.2 Classifying sandstones

Description	Rock name
Angular grains, 85% quartz, 15% feldspar, <5% silt and clay	Arkosic arenite
Rounded grains, 99% quartz, <2% silt and clay	Quartz arenite
Angular grains, 70% quartz, 20% lithic and 10% feldspar, ~20% silt and clay	Lithic wacke

Q6.3 Making evaporite

Responses will vary

Q6.4 Interpretation of past environments

Description	Source rock	Weathering	Transportation	Dep. environment
Cross-bedded quartz sandstone, rounded grains	probably sandstone	strong chemical weathering	wind	desert
Feldspathic sandstone and mudstone with volcanic fragments and repetitive graded bedding	granite and volcanic rock	weak chemical weathering	short transport in a river	sub-marine fan
Conglomerate with well- rounded pebbles and cobbles, imbricated	granite and volcanic rock	difficult to tell	high-energy river	moderate energy river
Limestone breccia with orange-red matrix	limestone	mechanical only	rock fall	talus slope, oxidizing environment