Leaky salt: Pipe trails record the history of cross‐evaporite fluid escape in the northern Levant Basin, Eastern Mediterranean. (20th February 2021)

• Record Type: Journal Article
• Authors: Oppo, Davide; Evans, Sian; Iacopini, David; Kabir, S. M. Mainul; Maselli, Vittorio; Jackson, Christopher A.‐L.
• Is Part Of: Basin research. Volume 33:Number 3(2021)
• Page Start: 1798
• Page End: 1819
• Publication Date: 2021-02-20
• Subjects: cross‐evaporite escape -- Eastern Mediterranean -- fluid escape -- fluid pipe -- focused fluid flow -- overpressure -- salt leakage; Sedimentation and deposition -- Periodicals; Sedimentary basins -- Periodicals; 551
• DOI: 10.1111/bre.12536
• Languages: English
• ISSNs: 0950-091X

Abstract

Abstract: Despite salt being regarded as an extremely efficient, low‐permeability hydraulic seal, an increasing number of cross‐evaporite fluid escape features have been documented in salt‐bearing sedimentary basins. Because of this, it is clear that our understanding of how thick salt deposits impact fluid flow in sedimentary basins is incomplete. We here examine the causes and evolution of cross‐evaporite fluid escape in the northern Levant Basin, Eastern Mediterranean. High‐quality 3D seismic data offshore Lebanon image hundreds of supra‐salt fluid escape pipes distributed widely along the margin. The pipes consistently originate at the crest of prominent sub‐salt anticlines, where overlying salt is relatively thin. The fact the pipes crosscut the salt suggests that hydrofracturing occurred, permitting focused fluid flow. Sequential pipes from unique emission points are organized along trails that are several kilometres long, and which are progressively deformed due to basinward gravity gliding of salt and its overburden. Correlation of pipes in 12 trails suggests margin‐wide fluid escape started in the Late Pliocene/Early Pleistocene, coincident with a major phase of uplift of the Levant margin. We interpret that the consequent transfer of overpressure from the central basin area, in addition to gas exsolution from hydrocarbons already trapped in sub‐salt anticlines, triggered seal failure and cross‐evaporite fluid flow. We infer that other causes of fluid escape in the Eastern Mediterranean, such as subsurface pressure changes driven by sea‐level variations and salt deposition associated with the Messinian Salinity Crisis, played only a minor role in triggering cross‐evaporite fluid flow in the northern Levant Basin. Further phases of fluid escape are unique to each anticline and cannot be easily correlated across the margin. Therefore, despite a common initial cause, long‐term fluid escape proceeded according to structure‐specific characteristics, such as local dynamics of fluid migration and anticline geometry. Our work shows that the mechanisms triggering cross‐evaporite fluid flow in salt basins vary in time and space. Abstract : In the northern Levant Basin, hundreds of fluid escape pipes are organized in linear trails, documenting widespread cross‐evaporite fluid migration since the Late Pliocene/Early Pleistocene. Major uplift of the basin margin is inferred to have caused lateral overpressure transfer and the resulting seal failure above prominent sub‐salt anticlines. This study shows that cross‐evaporite fluid escape in the Eastern Mediterranean can have multiple causes, which vary over time, act in synergy, and have different impacts in the various areas of this salt giant basins.