Parameter: Source Rock
1) Type-2 Deep Offshores
These offshores are, directly, associated with the formation of megasutures, i.e., with the formation of the different supercontinents, as Proto-Pangea (Precambrian), Pangea (Permo-Triassic) and Neo-Pangea, which agglutination of the continents is underway. As a result, their variety is much greater than in Type-1 Deep Offshores. In general, Type-2 Deep Offshores develop non Atlantic-type divergent margin (associated with B-subduction zones), which can form, mainly in backarc and forearc basin. However, they can develop, also, in association with A-Type subduction (fold belts), particularly, when the extension is big enough to create an oceanization (Mediterranean-Type Basins). Consequently, the prediction of the generating petroleum sub-system and its evaluation is very dependent on the characteristics of the episutural or perisutural basins on which the deep offshore has developed.
a) Backarc Basins
Type-2 Deep Offshores seem to be more frequent when there is oceanization behind the volcanic arc, i.e, when the backarc basin broke-up or, in other words, when there is formation of a marginal sea.
a1) Without Oceanization
If the deep offshores develop in this type of basin, which is relatively rare, the generating petroleum sub-system is associated with the underlying rift-type basins induced by the stretching of the crust behind the volcanic arc.
Ex: SW Sulawesi deep offshore (Salajar basin) ;
North Bali deep offshore , etc.
a2) With Oceanization
In this type of basin, Type-2 Deep Offshores are more frequent than in the previous basin type. The generating petroleum sub-system is, most often, attached to progradational intervals (slope shales or deep shales) and , rarely, with transgressive intervals overcoming rift-type basins (occurring just upstream in the conventional offshore).
Ex: Makassar deep offshore ;
Sulu Sea deep offshore, etc.
b) Forearc Basins
The deep offshores associated with this type of basin are, generally, very poor in hydrocarbons. When hydrocarbons are generated, they are most often related to underlying basins. This seems to be the case in the SW Java offshore (Indonesia), where potential source-rocks were deposited in the Paleogene backarc basin.
c) Fold Belts
Panonian-Type Basins - The existence of deep offshore linked to Pannonian-type basins is unlikely. In fact, although Pannonian basins are backarc basins associated with continental collisions and located in the concave side of A-subduction zones, they are overlying the continental crust. The absence of oceanization and significant thermal subsidence seem to be not favorable to the development of a generating petroleum sub-system.
Mediterranean-Type Basins
Unlike the Pannonian basins, deep offshores are very common in association with this type of basin. We can mention their occurrence in the following geographic basins : (i) Gulf of St. Lawrence ; (ii) St. George (Alaska) ; (iii) Ana Maria (Cuba) ; (iv) Cauca (Colombia) ; (v) Alboran (Algeria) ; (vi) Adana (Turkey) ; (vii) West Mediterranean (Ligurian) ; (viii) Sardinia ; (ix) Gulf of Mexico ; (x) Strait of Makassar (non Atlantic-Type divergent margin), etc.
Ex: Gulf of Mexico
d) Foredeep Basins
Deep offshores associated with foredeep basins, although rare, can develop in areas with high subsidence such as the North Slope (Colville), Pecten-Chiapas (Chiapas depression and the Chaparral basin), Vera Cruz ( Mexico), South Adriatic, South Caspian Sea, etc. Source-rocks can be located in the foredeep or in the underlying sedimentary platforms (ramps with grabens or tilted blocks).
Ex: North Slope
