#3:  Chemical Composition

Classifying sediments based on their chemical composition is fairly simple and straightforward. There are two important varieties: Silicious and Calcareous.

SiO₂ (aka silica or quartz)

Siliceous Oozes are a fine-grained pelagic deposit composed of 30% or more siliceous (SiO₂) material of organic origin. Siliceous particles dissolve slowly and therefore are presevered more readily.

CaCO₃ (aka calcium carbonate or calcite)

Calcareous Oozes are wide-spread in relatively shallow areas of the deep sea. Calcium Carbonate (CaCO₃) particles dissolve at “Carbonate Compensation Depth” = (CCD):

• Atlantic: ~ 4,000 m
• Pacific: ~ 500 - 1,500 m

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#4: Place of deposition (Depositional environment)

Terrigenous sediments are deposited near land and derived primarily from land sources. Most terrigeonous sediments are also lithogenous sediment, and geologists use grain sizes (gravel, sand, and mud) to describe them.

Neritic sediments are deposited in shallow coastal waters, mainly on the continental shelves. They include fine lithogenous sediments (silts and clays) in addition to biogenous sediments

Pelagic sediments are deposited in the open ocean and are composed of sediments which have settled to the deep-ocean floor (biogenous, lithogenous and hydrogenous sediments)