Interplay between early rifting, later folding, and sedimentary filling of a long-lived Tethys remnant: The Levant Basin

Deep and long-lived rifted basins host valuable information about tectonic evolution and environmental changes occurring in their surroundings throughout hundreds of millions of years. These basins, however, are hard to infer, because their deep parts are commonly obscured in seismic images and their structure is affected by several deformation phases that occurred during their long history.

The Levant Basin is a good example for a deep Tethyan basin that formed alongside Gondwana breakup. Unlike many Tethyan basins that were eroded and/or severely deformed during the Alpine orogeny, the Levant Basin has preserved a thick (>15 km), long-lived (>250 Myr), and continuous sedimentary record providing a world-class archive to study the role of post-rift subsidence and sediment supply on depocenter evolution. It exemplifies classic tectono-sedimentary problems, such as basin inversion and the mutual relationships between accommodation space, sediment supply, and sediment accumulation. Also, it provides valuable information about the ancient Tethyan margin, which were mostly destructed by the Alpine Orogeny.

We review the tectonic and sedimentary evolution of the Levant Basin. We synthesize regional seismic interpretations from previous studies utilizing thousands of kilometers of seismic lines and tens of wells in a unified dataset. Based on thickness analysis, we identify the syn-rift to post rift transition. The regional seismic horizon marking this transition is tied to dated horizons in wells providing a concrete age constraint of pre- 163 Ma (end of Callovian) for the end of rifting, which was previously debated. In addition, we show that rifting comprises at least two phases, which are equivalent to two extensional phases documented onshore: Permian to Middle-Triassic and late-Early to Middle-Jurassic. We further show that the early extensional structures (normal faults) approximately coincide with much younger contractional structures of the Syrian Arc Fold belt.

Analysis of 11-thickness maps showcase the 250 Myr evolution of sedimentary filling, opening a discussion about what controlled depocenter migration in relation to tectonic subsidence and sediment supply. We distinguish between periods during which near margin accumulation dominated versus periods during which more sediments accumulated in the deep basin. We explain these changes in light of sediment sources in surrounding continents and paths of transport. Marginal accumulation periods (syn-rift, early post-rift, and Pliocene-Quaternary) represents sediment supply from the nearby Levant (Arabia), whereas, deep basin accumulation periods represent sediment supply that was either provided from the water column (pelagic micro- and nano-fossils, Santonian to Mid-Eocene), or transported mostly from Africa with minimal accumulation along the Levant margin (during the Late-Eocene to Miocene).

This review is based on holistic approach for basin analysis. A lateral perspective integrates seismo-stratigraphic information from the deep basin with lithological and paleo-geographical information from nearby continental areas. A vertical perspective ties deep basin structures formed during rifting with shallow structures formed much later during contraction. Structural maps are used to highlight horsts, folds, and canyons, whereas thickness maps are used to highlight patterns of sediment accumulation. Finally, the distinction between distal basin and marginal accumulation is interpreted in light of the regional geology hinting for sediment sources.