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

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Authors

Davide Oppo , Sian Evans , David Iacopini , SM Mainul Kabir, Vittorio Maselli , Christopher Aiden-Lee Jackson 

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 this hydrofractured permitting focused fluid flow. Sequential pipes from unique emission points are organized along trails that are several kilometers 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.

DOI

https://doi.org/10.31223/osf.io/v9fj8

Subjects

Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure

Keywords

Cross-evaporite escape, Eastern Mediterranean, Fluid escape, Fluid pipe, Focused fluid flow, Ovepressure, Salt leakage

Dates

Published: 2020-08-05 16:39

Last Updated: 2020-08-06 11:12

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License

GNU Lesser General Public License (LGPL) 2.1

Additional Metadata

Data Availability (Reason not available):
The data that support the findings of this study are available from LPA. Restrictions apply to the availability of these data, which were used under license for this study.

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