1) Breccia and Conglomerate: Coarse-grained clastic sedimentary rocks. Breccia composed of coarse, angular rock fragments. Conglomerate composed of rounded gravel.
2) Sandstone: Medium-grained clastic sedimentary rock. Types determined by composition. Quartz sandstone is >90% quartz grains. Arkose is mostly feldspar and quartz grains. Graywacke is sand grains surrounded by a dark, fine grained matrix, often clay rich.
3) Shale: Fine-grained clastic sedimentary rock, silt and clay sized grains. Sediment deposited in lake bottoms, river deltas, floodplains, and on deep ocean floor. Fissile=Splits into thin layers.
4) Siltstone: Slightly coarser-grained than shales, non-fissile.
5) Claystone: Predominantly clay-sized grains, non-fissle
6) Mudstone: Silt and clay-sized grains, massive/blocky
Sandstone v Conglomerate: Differences in grain size, differences in sorting
Breccia v Conglomerate: Conglomerate particles are rounded and breccia particles are angular
Sedimentary rocks give important clues to the geologic history of an area.
1) Source area: Locality that eroded and provided sediment. Sediment composition, shape, size and sorting are indicators of source rock type and relative location.
2) Environment of Depositional: Location where sediment came to rest. Sediment characteristics and sedimentary structures (like fossils) are indicators. Glaciers, alluvial fans, river channels, floodplains, lakes, deltas, beaches, lagoon, shallow marine shelves, reefs, deep marine.
3) Transgression and Regression: Records the rising and falling of sea level. Transgression: Sea level rises and marine sedimentary deposits will migrate onto the subsided land areas. Regression: Sea level falls and the sedimentary deposits will migrate away from the land areas.