Palaeotectonic cross-sections through the Mid-Polish Trough

Abstract

The Late Perm ian and Me so zoic evo lu tion of the Mid-Polish Trough is ana lysed using a set of palaeotectonic cross-sections which are con strained by re gional in te grated depth-converted re flec tion seis mic pro files. Re sults sup port the con cept that the cen tral and NW part of the Mid-Polish Trough can be sub di vided into a Pom er a nian and a Kuiavian seg ment. The Pom er a nian seg ment is characterised by lower sub si dence and a shal lower depth to the base of the Zechstein (3500–4000 m) as com pared with the Kuiavian seg ment. The Pom er-a nian ba sin was characterised by a nearly sym met ri cal struc ture and a sin gle depocentre. In Kujawy, the ba sin dis plays a more com plex struc ture with sev eral lo cal depocentres. In the Pom er a nian seg ment, salt struc tures are poorly de vel oped (salt pil lows). These formed rel a tively late: dur ing the lat est Cre ta ceous and Early Paleocene. In the Kuiavian seg ment, salt struc tures in clude also salt diapirs which be gan to form at the end of the Muschelkalk, and were ac tive later through out Me so zoic times, as ev i denced by lat eral fa cies and thick-ness changes. Dur ing end Cre ta ceous and Paleocene ba sin in ver sion, the base of the Zechstein was up lifted by 3000–4000 m in the Kuiavian seg ment and by 2000–3000 m in the Pom er a nian seg ment. The tran si tion zone be tween the Pom er a nian and Kuiavian seg-ments, lo cated in the area be tween Piła and Toruń, dis plays mixed fea tures in its struc ture and geo log i cal evo lu tion. Sub si dence of the Mid-Polish Trough was con trolled by mul ti ple extensional pulses dur ing which pre-existing crustal-scale faults were re ac ti vated. Sim i-larly, in ver sion of the Mid-Polish Trough in volved re ac ti va tion of crustal faults. Seg men ta tion of the Mid-Polish Trough can be re lated