Rola halokinezy w powstawaniu trzeciorzędowych złóż węgla brunatnego na Niżu Polskim

Abstract

Halokinetic impact on origin of the Tertiary lignite deposits on the Polish Lowlands.A b s t r a c t . Large concentrations of lignite, creating economic lignite deposits, occur frequently in a close vicinity or directly above salt domes. Those lignite accumulations, common in the northern and central parts of Szczecin-Łódź-Miechów Synclinorium (Polish Lowlands), were partially produced by halotectonic processes active during Tertiary. Generally, differentiated activity of halotectonics did not secure proper conditions controlling extensive accumulation of phytogenic matter and even destroyed the uplifted lignite seams. However, conditions convenient for phytogenic matter accumulation were rather common locally. The following processes: 1) salt subrosion of a dome upper part, 2) halokinetic salt outflow along opened fault surfaces, 3) formation of secondary peripherial sinks nearby the domes and 4) development of extensional depressions on the top of disrupted antyclines formed within a salt-dome overburden during the uplift, all were responsible for generating of salt-related sinks. In a regional scale, development of the primary peripherial sinks between salt structures (mostly salt crests, walls and pillows) could be also related to the halokinetics. Detailed analysis of geological setting in vicinities of some major salt domes on the Polish Lowlands evidenced that more than 80% of lignite resources are directly or indirectly related to these structures. Those lignite resources are most profitable due to an advantagenous overburden ratio. Application of complex research methods (including high-resolution seismic profilling) enables a model construction of those areas and precise defining the relations between stages of salt structure development and a rate of phytogenic accumulation, offering/bringing significant data for lignite prospection.