Структурно-минералогическая характеристика палеогеновых песков Северо-Восточной Болгарии

Pages: 
pp. 59-68
Abstract: 

N. P. Ruskova. Textural and mineralogical features of Paleogene sands in Northeast Bulgaria. The studies concern the sandy sediments of the Paleogene in Northeast Bulgaria which outcrop in a relatively persistent stratigraphic level of Lower Eocene age along the scarps of Momino, Frangen and Provadia Plateau. Two main lithological varieties occur - yellowish fine-grained sands to silts and white fine- to medium-grained sands. The first (along with a packet of white or grey-white sands) form the base of the section and arc related to Beloslav Formation, and the white coarser-grained sands (Dikilitas Formation) occur with a gradual transition in a higher stratigraphic level. Both types show characteristic texturaI parameters: the yellowish sands of Beloslav Formation are slightly clayey and not well sorted, gradually become purer upwards and in the packet of white sands with wide lateral and vertical distribution the textural parameters (σ1 0.5 to 0.9) indicate practically everywhere excellent sorting and normal distribution. The sands of Dikilitas Formation are more variable, locally cross- bedded (in Provadia Plateau), with rapidly changing textural parameters, relatively bad sorting (σ1 over 1), in places bimodal. In mineralogical respect the sands are monotonous, practically monomineral quartz or slightly oligomictic sands. The heavy fraction (below I %) consisting of stable accessory minerals, kyanite, magnetite (and its martitized varieties), epidote minerals and rarely amphibole, indicates mixed supply in which metamorphic, volcanomagmatic and mainly recyclic components take part. Typomorphic are kyanite, related probably to the metamorphic complex of North Dobdrudža, unstable epidote varieties, amphibole and magnetite - to the East Srednogorie zone, and garnet along with the main quartz amount - to the slightly cemented oltgomictic sandstones of Santonian age in Northeast Bulgaria.