Stratygrafia, facje i tektonika mastrychtu zachodniej części Wyżyny Lubelskiej

Abstract

Mastrycht Lubelszczyzny wchodzi w skład dwóch typów formacji lito stratygraficznych: 1– wapieni, margli, opok i gez oraz 2 – kredy piszącej. W jego profilu autorka wyróżniła trzy ogniwa, a w każdym z nich z kolei po kilka kompleksów litologicznych przebiegających diachronicznie w stosunku do granic chronostratygraficznych. Analiza wyników z przeglądowego kartowania, wierceń oraz pomiarów spękań i danych z literatury pozwoliła wyróżnić wielkopromienne fałdy o generalnym kierunku NW – SE oraz uskoki zrzutowe o kierunku NW – SE i przesuwcze NE – SW. Fałdy zaczęły się tworzyć w czasie sedymentacji mastrychtu, przemawiają za tym zmniejszone miąższości osadów w obrębie antykliny Opole Lubelskie – Zakrzew. Uskoki są niewątpliwie pokredowe.

STRATIGRAPHY, FACIES AND TECTONICS OF THE MAESTRICHTIAN IN WESTERN PART OF THE LUBLIN UPLAND

Maestrichtian rocks of western part of the Lublin Upland, developed as opokas, chalk and, on a smaller scale, limestones, marls and gaizes, represent the IIIrd type formation of limestones, marls, opokas and gaizes, and the IVth type formation of chalk (A. Błaszkiewicz, S. Cieślinski, 1979).

Two opoka members may be recognized in the IIIrd type formation: Member A, with some share of marls and chalk (Piotrowin Opokas), and Member C, with share of limestones, marls and chalk (Kazimierz Opokas). In the IVth type formation, there is recognized Member B – chalk and marls (Głusko Chalk). The members were further subdivided into complexes comprising separate lithological successions.

The Member A comprises complexes o/cp – m₃ and om/cp – m₃, the Member B – km/m_1–3 and k/m _l–3 , and the Member C – om/m₃ and ow/m₃. Individual elements of the above symbols denote the major and second order or characteristic lithological types and the chronostratigraphic position of a unit (Figs. 1 and 2).

The above subdivision of the section into members reflects cyclic changes in sedimentary reservoir, related to the Alpine tectogenesis and the resulting origin of folds with NW–SE oriented axes and two major fault systems, NW – SE and NE – SW oriented (Figs. 3, 7). The folds began to originate in times of sedimentation, which is evidenced by a reduced thickness of the relevant rocks in the Opole Lubelskie – Zakrzew anticline, whereas the faults are post-Cretaceous.

The subdivision into complexes reflects differences in facies between the areas of the Opole Lubelskie – Zakrzew anticline and the marginal syncline, expressed by variability in thickness, lithological development and horizontal extent of individual complexes (Figs. 4 – 6). The above data give further support to the hypothesis of the influence of movements of the deep basement on sedimentation and tectonics during the Maestrichtian.