Continental stable platforms

Fig. 3. NE-SW cross-section of the Jeanne d Arc basin, showing the lystric Murre Fault which bounds the basin in the west. (1) Stable shelf (Bonavista Platform) (2) rollover anticline resulting from antithetic movement of the hanging-wall block along the Murre Fault (3) central Jeanne d Arc basin (4) Central Ridge. TR, interpreted Triassic continental red beds at the base of the Mesozoic sedimentary succession overlain by Lower Jurassic evaporites involved in diapirism (squared pattern). Insert map shows hydrocarbon fields of the Jeanne d Arc basin mentioned in text and location of section. From Tankard Welsink (1988). A, T, movement of fault block away from viewer and towards viewer, respectively.

Of the two main episodes of oil source-rock deposition, the Palaeozoic accounts for only 10—15% of the total reserves of conventional oils (Bois et al. 1982).The smaller size of the Palaeozoic oil reserves compared with those of the Mesozoic is probably mainly attributable to escape of the older oils from reservoirs due to later tectonic events and to various degradation processes (as described in Section 4.5.6). The surviving Palaeozoic oils are found in stable continental platforms that have escaped significant tectonic activity. The relationship of relative sea level to the occurrence of oil source rocks is reflected in the fact that most oil is derived from marine sources. In comparison, lacustrine source rocks are usually of much more restricted... 

Ronov et al. (1972, 1974) broadened the study to include the Russian and Scythian platforms (representative of stable, continental regions), the mio-geosyncline of the high Caucasus mountains, the mountains themselves, and the seaward eugeosyncline. The lanthanide concentrations in clays (shales) increased in a regular manner from the eugeosynclinal sediments to the Russian Platform a similar trend was observed for carbonates (fig. 21.3). The opposite... 

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