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Geosciences LibreTexts

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