Burial history plots

Figure 8.37. Burial history plot for Helderberg Group rocks and other strata. Helderberg Group is shaded, whereas the base of Ordovician strata, base of Silurian strata and base of Mississippian strata are shown as thin lines marked O, S and M. Dashed lines are time-temperature indices of maturity (TTI see Waples, 1980). The oil generation window represents the necessary conditions of time and temperature for potential oil generation. The 50° oil preservation deadline is the upper TTI limit for occurrence of oil with API gravity of 50°. (Modified from Dorobek, 1987.)...

Fig. 3. Time-depth-temperature burial history plot at North Coles Levee. Modihed from Wood Boles (1991). Note the rapid burial of the Stevens sandstone (shaded) at North Coles Levee, which is also typical of Stevens sandstone s burial history throughout the central basin. Carbonate cements formed throughout the burial history of the Stevens.

Fig. 13. Equilibrium fractionation plot showing possible combinations of water S 0 values and temperatures which are compatible with the intergranular and vein-fill dolomites. Curves plotted using the equation from Land (1983). Estimated 0%o smow for Carboniferous sea water from Popp et at. (1986) low-latitude meteoric water from Anderson Arthur (1983). Burial temperatures calculated from subsidence history (Fig. 3), 20"C surface temperature and 30"C km geothermal gradient.

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