*5.1. Thermal Evolution*

Figure 7 depicts the modeled evolution of temperature through time in the central sub-basin (Figure 7A) and eastern sub-basin (Figure 7B). During the initial Late Permian stage prior to salt mobilization, in the central part of the basin the thermal gradient is reduced within the salt (up to 3 km thick) as depicted by widely spaced isotherms (Figure 7A,B, VIII). Temperatures are elevated above the salt, implying enhanced heat flow. Towards the shoulders of the basin, the regional thermal gradient is reestablished.

In the Early to Middle Triassic stages, when salt was mobilized and reached the surface (Figure 7, IV to VII), the temperature distribution was altered as salt diapirs provided vertical conduits for conducting heat out of the basin, inducing a negative thermal anomaly in the interior of the diapirs. This thermal anomaly is highest at the center of the diapirs and gradually decreases outwards. Isotherms within the diapirs are widely spaced and, as a consequence, isotherms are deeper below salt than in the adjacent minibasins. Around the salt diapirs, the temperature is also a ffected by the reduced geothermal gradient inside the diapir. The wide, isolated diapir in the eastern sub-basin shows this e ffect more clearly (Figure 7B, IV). In this diapir, the temperature contrast between the salt interior and surrounding minibasins at ~3 km is as much as 30 ◦C. In the central sub-basin (section A), the negative thermal anomaly of a single diapir cannot be seen as the diapirs are narrower and closer together (Figure 7A, IV). In this section, the thermal e ffect of each diapir mutually interferes, resulting in a combined e ffect that lowers the isotherms below the regional trend. In the center of the basin, temperatures are as much as 60 ◦C lower than those in the platform areas far from the salt e ffect.

After deposition of the Upper Jurassic and Cretaceous-Cenozoic sediments, the salt diapirs are no longer connected to the surface (Figure 7, stages II and III). A positive thermal anomaly developed above the closely spaced diapirs in section A and above the single diapir in section B owing to the focusing of heat by the underlying salt. In section A, the temperature rises ~10 ◦C above the largest diapir compared to the surrounding sediments (Figure 7A, II) while in section B the temperature rises ~15 ◦C above the massive diapir (Figure 7B, II). The negative thermal anomaly within the salt diapirs is still present, but at a lower intensity than in previous stages.

Several pseudo-wells along the sections demonstrate the thermal e ffect of the salt at present day. In the central sub-basin (section A), we extracted temperatures in pseudo-wells through a small diapir at 9 km from the northern edge of the cross-section, and through a wider diapir at 17 km. Temperatures were also extracted in pseudo-wells at 27 km and at 56 km in a minibasin and a platform area, respectively (Figure 7A, I). Figure 8A depicts the distribution of temperature in these wells. The thermal gradient in the small diapir (9 km well) is greater than in the large diapir (17 km well). The temperature di fference between these wells is ~15 ◦C at a depth of 5 km. In both diapirs, the thermal gradient beneath the salt increases and depicts a similar trend to the one observed at the well in the platform area (56 km well). The temperature beneath the small diapir (9 km well) is still ~25 ◦C higher than below the large diapir (17 km well) (Figure 8A). These di fferences are most likely related to the size of the diapirs, with the wider diapir conducting heat more e fficiently. Significant thermal di fferences exist between the two wells outside salt structures (27 and 56 km wells). The maximum temperature di fference between these two wells is ~35 ◦C at a depth of 5 km (Figure 8A). Although both wells are outside the salt diapirs, the well in the minibasin (27 km) is between closely spaced diapirs whose mutually interfering e ffect induces a broad negative thermal anomaly in the central part of the basin. Therefore, temperatures in the minibasin resemble those in the salt diapirs rather than those in the platform areas.

In the eastern sub-basin (section B), we extracted temperatures in pseudo-wells at 29 km from the northern edge of the cross-section in a minibasin, at 45 km through the massive diapir, and at 100 km in the platform area (Figure 7B, I). Figure 8B displays the distribution of temperature in these wells. The temperature gradient in the salt diapir (45 km well) is considerably lower than in the minibasin and platform area (29 and 100 km wells). The greatest temperature di fference is ~110 ◦C at a depth of 7 km between the wells in the diapir (45 km) and the platform area (100 km). The well in the minibasin (29 km) shows intermediate temperatures, although still it is ~70 ◦C warmer than the diapir at a depth of 7 km (Figure 8B). These significant thermal di fferences are most likely related to the large size (width) of the salt diapir.

**Figure 7.** Evolution of temperature through time in (**A**) section A in the central sub-basin, and (**B**) section B in the eastern sub-basin. Black lines are unit contacts and red lines are isotherms. For guidance, stippled unit is the Lower to Middle Triassic Kobbe Formation (S4). Figure 1B shows the location of the sections.

**Figure 8.** Modeled, present temperature distribution in pseudo-wells along (**A**) section A in the central sub-basin, and (**B**) section B in the eastern sub-basin. Thick lines in the minibasins and platforms wells show the temperature distribution in potential reservoirs. Figure 6 (I) shows the location of the pseudo-wells.
