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Figure 11. Modeled thermal maturity (%Ro, vitrinite reflectance) for the top of the Wilcox Group. Ro was calculated using the Wilcox surface elevation (Figure 9) and more than 450 values of unpublished USGS Wilcox %Ro. Wilcox vitrinite reflectance values range from about 0.3 %Ro updip, near the outcrop, to more than 2.4 %Ro at depths greater than 24,000 ft in south Texas (after Warwick, 2006).