The “chimney forest” of the deep Montenegrin margin, south-eastern Adriatic Sea

Abstract A spectacular field of columnar carbonates has been discovered on the Montenegrin margin in the southern Adriatic Sea at a depth of about 450 m. The site exposes many columnar carbonates protruding from the substrate or abated on the bottom. Such carbonates attain maximum visible lengths of ca. 60 cm with diameters up to 20 cm; display an annular growth, and are either hollow or plugged by indurated sediment. Petrographic and geochemical analyses document the pervasive presence of dolomite, and δ 13 C values as low as −30‰ VPDB. These ‘chimneys’ are therefore interpreted as former conduits related to hydrocarbon expulsion in this sector of the Adriatic basin. However, available data suggest that hydrocarbon flows at this site have ceased. Our results show that chimneys formed inside the local depositional units, glacial Pleistocene shelf shelly-rich muddy sediment and were successively exhumed from the host sediment. Today, the chimneys offer substrate to benthic life, including cold water corals and sponges. The U-series dating of these carbonate concretions is complicated by the presence of a significant fraction of detrital sediment, which represents a major source of initial 230 Th. AMS- 14 C and 87 Sr/ 86 Sr dating of shells embedded in one of the chimney provided ages beyond the range of radiocarbon dating and