Fluvial, alluvial, or proluvial deposits

These are denominated to a lithologic and unconsolidated group that consists of sand, gravel, clay and lime that has been deposited or are becoming deposited mainly along the different grades of the rivers that are in certain regions. These deposits can be seen in transported floors of heterogeneous, permeable and variable potency in composition. The fluvial deposits and or alluvial deposits are the most important type in the world and are subdivided in:

Vega alluviums. A lot of the terraces are simply older alluvials which were eroded and dug in their central part or on one of the sides, deepening the river bed of the rock by increase of the gradient due to the increase of the waters, which causes a lot of banks to run dry, sometimes at very little height above the river beds and other times a great distances from these.

Terrace alluvials. These are the clastic accumulations that have been left behind and its tributaries during a previous stage of depositing. These are the deposits of greater extension in certain areas. Lithologically they are made up of sand, gravel, clay, lime and conglomerates that both horizontally and semi horizontal; these deposits are made up of transported grounds that have a variable permeability and can be found in the form of high and low terraces, of hills, double alluviums, triples etc.

Lacustrine alluvials. These are those alluviums that are deposited in depressions in the form of a cup and or lakes.

Littoral or marine alluvials. These are deposits situated in the marine coasts. There are some very ancient ones and today they can be found elevated in the form of banks. These are also called placers and are brought about due to the force of the waves, where the jump and undercurrent carry with them the smaller particles, concentrating the heavier particles that come from the terraces of the coasts and from the rivers. These can be found submerged and out in the sea.

Fossilized or buried alluviums. These are the ones that have been covered by newer formations and lava that has buried gravel of placers down to considerable depths.

Auriferous conglomerates. These consist of cemented alluvials, also known as cemented gravel, due to the consolidation of the auriferous gravels in a conglomerate.