Properties and depositional environment of the Neogene Elhovo Lignite, Bulgaria

Past climate and vegetation in Southeast Bulgaria — a study based on the late Miocene pollen record from the Tundzha Basin

“…The peat accumulation occurred in an environment subject to a low subsidence rate, in which the woods were sustained severe mechanical destruction prior to the burial. Peat accumulation was terminated by a major flooding event, expressed by a short-lived lake (Zdravkov et al 2007). The Elhovo Formation is unconformably overlain by a few meters of the Pleistocene-Holocene sediments.…”

“…The Tundzha Basin was an extensive graben structure formed in the final stage of the continental collision at the southern edge of the Alpine Orogen. Typically, this type of basins has a similar development, starting with lake-river sedimentation and deposition of conglomerates and sands, gradually passing into clay sedimentation and subsequently swamping and forming thick coal beds covered by lake sediments (Zdravkov et al 2007). This sequence reflects the drowning of the palaeomire due to high subsidence rates.…”

“…The high number of lignite layers in the Tundzha Basin is the evidence of a relatively low subsidence speed, which allowed the frequent change between lacustrine (diatomaceous and black clays) and swampy environments (lignite).. The high peat content of lignite indicates that swamps were often flooded, and the marsh complex was of the so-called rheolytic marshes (Zdravkov et al 2007).…”

“…The geochemical analysis of the coals showed that lignites originated from coniferous wood, which is significantly more resistant to oxidation processes than that of herbaceous plants and it is better stored (Zdravkov et al 2007). Probably the main coal precursors were the representatives of Taxodioideae (Taxodium, Glyptostrobus), as in most Miocene lignite basins in Bulgaria.…”

“…During the periods of peat accumulation, the (ground)water table was probably not above the peat surface. The basis for such asumption is the complete absence of algal remains and of sapropelic coal (Zdravkov et al 2007). According to Zdravkov et al (2007), the vegetation rich in decay-resistant conifers, accompanied by mesophytic broadleaf species, prevailed during these intervals.…”