Burial history model for New Albany and Maquoketa shales generated using Basin Mod 1D software (Platte River Associates,
Inc.). (A) Burial history diagram for Pike County showing levels of thermal maturity and maximum exposure temperatures reached by
New Albany and Maquoketa shales; (B) Evolution of transformation ratio and R
o
of New Albany and Maquoketa shales throughout
geologic time and measured present day R
o
values. In the case of the Maquoketa Shale, the calibrated reflectance of solid bitumen was
used instead of R
o
to compensate for the lack of vitrinite. The burial history model used the hybrid model of variable heat flow combined
with deep burial during Permian (Rowan et al., 2002). Ord = Ordovician; Sil = Silurian; Dev = Devonian; Carb = Carboniferous; Perm =
Permian; T = Triassic; Pal = Paleogene; N = Neogene.