In some areas coral reefs or carbonate muds dominate the shelf. Sediments on the slope consist of fine silts and clays. Sediments consist of sands, silts and clays from shelf. Calcareous and siliceous deposits are the most common. Dunes of cross bedded sands often form.
Sediments consist of sands, silts and clays interlayered by meandering streams.
Sands are found in point bars and along stream banks and bottoms, clays and silts are found on the floodplain. Each of the environments above contain distinct sediments. This enables geologists to determine the past environment of an area based on the rock types found there. Other sedimentary features help geologists determine the environment of deposition. Forms in anaerobic areas such as a restricted basin, lake or swamp.