Internal wave deposits in Jurassic Kermanshah pelagic carbonates and radiolarites (Kermanshah area, West Iran)

• First report of internal wave deposits within pelagic limestones and radiolarites
• They formed from upslope and downslope flows caused by breaking internal waves.
• The downslope distribution of internal wave deposits is proposed.
• Internal waves developed in a thermocline associated to climate warming
• Internal waves were excited by volcanic, storm and tectonic events.

We report eventites generated by turbulence events triggered by breaking internal waves in Jurassic pelagic muds deposited in a graben area located between the Arabian and Bisotoun carbonate platforms, at the Kermanshah basin (West Iran). The 43 m-thick studied Pliensbachian–Aalenian succession at Kermanshah includes sponge spicule-radiolarian limestones and cherts with cm- to dm-thick intercalations of pyroclastic beds and coarse-grained deposits formed by neritic-derived grains and reworked pelagic material. Breaking of internal waves in localized areas reworked the available sediment on sea floor, including the erosion of cohesive pelagic muds and the resuspension of neritic-derived grains, which were resedimented from the Bisotoun platform most probably by storms or turbidity currents. The generated internal wave deposits include: flat- and round pebble limestone conglomerates, formed by deposition of pelagic clasts and neritic-derived grains near the breaker zone; laminated packstone-grainstones deposited by high-energy, upslope (swash) and downslope (backswash) flows; cm-thick packstone-grainstones with asymmetrical starved ripples and hummocy crossstratification, generated downdip by waning of backwash flows and internal wave oscillatory flows. These internal wave deposits predominate in the Pliensbachian–early Toarcian, and were related to internal waves developed along a thermocline linked to climate warming and excited by submarine volcanic eruptions, storms or tectonic shaking.