Stage of Thermal Maturity

Maturation Parameters

PI [S₁/(S₁ + S₂)]

R_o (%)

Tmax (˚C)

Immature

0.2 - 0.6

<435

<0.10

Mature

Early

0.6 - 0.65

435 - 455

0.10 - 0.15

Peak

0.65 - 0.9

455 - 450

0.25 - 0.40

Late

0.9 - 1.35

450 - 470

>0.40

Postmature

>1.35

>470

-