At a first glance, you may call it just a breathtaking wonder of the nature. A million thoughts going trough your mind while trying to get a reasonable explanation for origin and existence of these imposing rock trunks mysteriously and peacefully lying on NE Bulgarian fields 20 kilometres near to Varna and the Black Sea shore. Many local tales are saying even nowadays that we are actually admiring a petrified forest. The simplest and more convenient explanation for a famous touristic attraction for sure.
Photo source: GeologX
In reality, plenty of geological studies have been carried out and they unanimously advocate the marine cold seeps theory.
"Up to 10 m high and meter-diameter tubular concretions (so-called columns) are exposed within Lower Eocene sands and sandstones (Dikili Tash Formation). These are calcite-cemented sandstone concretions that reveal: a) the Paleogene structural framework likely played an important role in directing fluid movement to the paleo-seafloor and b) the morphology of different types of tubular concretions was controlled by the subvertical path of ascending gas-bearing fluids through the unconsolidated host sediments as well as by the characteristics of the host lithology and lateral differences in seepage conditions. Based on a detailed petrographical, geochemical and lipid biomarker study, it was furthermore shown that interparticular low-magnesian calcite cementation of the unconsolidated host sediments around the rising methane-bearing fluid plume, occurred at shallow depth below the seafloor and was triggered by the microbial mediated anaerobic oxidation of methane"(De Boever et al., 2008).
Photos source: GeologX