The Kimmeridge clay of the North Sea and the Tannezuft shale of Algeria are of this kerogen type, with original organic matter consisting of algal detritus and material from zooplankton and phytoplankton.

The Kimmeridge clay of the North Sea and the Tannezuft shale of Algeria are of this kerogen type, with original organic matter consisting of algal detritus and material from zooplankton and phytoplankton.

• A. Type II
• B. Type I
• C. Type III
• D. Type IV

Answer: (A)

The type of kerogen is determined by the origin of the organic matter and the environment where it formed, which in turn dictates what kind of hydrocarbon it can generate. When the organic matter comes from marine plankton and algae—as indicated by algal detritus plus material from zooplankton and phytoplankton—the kerogen is typically Type II. This marine, planktonic source is known to be oil-prone, yielding liquids (oil) upon maturation. The Kimmeridge clay and Tannezuft shale are classic marine shales rich in such planktonic and algal material, so they fit Type II kerogen. By contrast, Type I is more lacustrine and extremely algal-rich, often with higher oil yield but from freshwater environments; Type III comes from terrestrial (land plant) matter and is gas-prone; Type IV is largely inert with little hydrocarbon potential.

The type of kerogen is determined by the origin of the organic matter and the environment where it formed, which in turn dictates what kind of hydrocarbon it can generate. When the organic matter comes from marine plankton and algae—as indicated by algal detritus plus material from zooplankton and phytoplankton—the kerogen is typically Type II. This marine, planktonic source is known to be oil-prone, yielding liquids (oil) upon maturation. The Kimmeridge clay and Tannezuft shale are classic marine shales rich in such planktonic and algal material, so they fit Type II kerogen. By contrast, Type I is more lacustrine and extremely algal-rich, often with higher oil yield but from freshwater environments; Type III comes from terrestrial (land plant) matter and is gas-prone; Type IV is largely inert with little hydrocarbon potential.