Which kerogen type is associated with algal detritus and zooplankton/phytoplankton material?

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

Answer: (B)

Kerogen types tell you what kind of original organic matter and environment produced the source rocks. When the organic matter is primarily marine plankton—algal detritus along with zooplankton and phytoplankton—the resulting kerogen is Type II. This marine, hydrogen-rich material is oil-prone and tends to generate liquid hydrocarbons when heated. Other types come from different inputs: kerogen from terrestrial plant material (Type III) is more gas-prone, and kerogen that’s largely inert (Type IV) yields little hydrocarbon. Type I is oil-prone too, but it mainly stems from lacustrine or freshwater algal pools. So the association with marine algal detritus and plankton points to Type II kerogen.