Leaky salt: the history of cross-evaporite fluid escape as recorded in pipe trails, Levant Basin, Eastern Mediterranean

Reconstructing the history of repeated fluid escape events is challenging as their expression in the geological record frequently overlaps in time and space. In the northern Levant Basin, the Messinian salt tectonics preserved in the stratigraphic record successive fluid escape episodes from common leakage points. Here, the fluid escape formed discrete, cross-evaporite fluid escape pipes arranged in several kilometers-long trails. The pipes originate at the crest of prominent sub-salt anticlines, where thinning and hydrofracturing of overlying salt permitted focused fluid flow. Sequential pipes were progressively deformed due to basinward gravity-gliding of salt and its overburden. The analysis of pipes distribution suggests that margin-wide fluid escape started contemporaneously in the Late Pliocene/Early Pleistocene, coincident with a significant uplift of the Levant margin. The uplift transferred fluids and overpressure from the center of the basin to its margin. The focus of overpressure triggered seal failure and cross-evaporite fluid flow. We infer that other triggers, mainly associated with the Messinian Salinity Crisis and compressive tectonics, played a secondary role in the northern Levant Basin. After the initial margin-wide fluid escape, further escape events are unique to each leakage point. Despite a common initial cause, long-term fluid escape proceeded independently according to structure-specific characteristics, such as the local dynamics of fluid migration and anticline geometry. Cross-evaporite fluid escape in the southern Levant Basin has been attributed to the Messinian Salinity Crisis and compaction disequilibrium. We argue that these mechanisms do not apply to the northern Levant Basin. Here, fluid escape was mainly driven by the tectonic evolution of the margin. Within this context, our study shows that the causes of cross-evaporite fluid escape can vary over time, act in synergy, and have different impacts in different areas of large salt basins.