Hydrocarbon‐derived thrombolites from the Outer Carpathians (Lower Cretaceous, Poland)

Shallow marine thrombolites from a newly discovered Lower Cretaceous cold seep in the Outer Carpathians (Poland) were analysed in order to untangle the complex sedimentological and biogeochemical processes involved in their formation and their diagenetic modifications. The studied thrombolites are made of two components: (i) microcrystalline mesoclots; and (ii) spar‐filled framework cavities. These components are dominated by calcite and show a complex spatial relationship, resulting in a heterogeneous, clotted fabric. The mesoclots exhibit digitate structures, often concentrically‐laminated, and are chiefly composed of microcrystalline material with δ13C values from −34.8 to −19.4‰ PeeDee Belemnite. Biomarkers analyses show the presence of 2, 6, 10, 15, 19‐pentamethylicosane within the mesoclots. The mesoclots host