Definition - What does Immature mean?
Immature in geology refers to the hydrocarbon source rocks which have not completely entered the most favorable conditions for a generation. It is considered that the greater amount of quartz in coarse sedimentary rocks results in high mineralogical maturity. The rocks which have a sand-sized quartz grains with sharp edges and corners, and clay minerals are said to be immature. The rocks with quartz grains of same sizes or well rounded are said to be super mature. A long transportation time increases the maturity of sediments.
Petropedia explains Immature
The immature sandstones have sand size grains and clay matrix. The grains are poorly sorted and are angular in the immature sandstones. This shows that there is a wide range of sand sizes present in immature sandstones. This is a characteristic of environments where sediments are dumped and are thereafter not worked on by currents or waves. The mature sediments contain stable minerals and thus, usually have a smaller variety of minerals than the immature sediments containing both unstable and stable minerals. The maturity of rocks is also considered as an indicator of their hydrocarbon potential.