Neokom obszaru warszawsko-radomskiego

Abstract

Neokom obszaru warszawsko-radomskiego reprezentowany jest przez górny walanżyn i hoteryw. W artykule przedstawiono stratygrafię tych osadów, charakterystykę litostratygraficzną oraz rozwój paleogeograficzny i facjalny. Osady górnego walaniżynu i hoterywu stanowią częściowo formację włocławską (klastyczną), częściowo formację białobrzeską (wapienno-klastyczną). Rodzaj i tempo sedymentacji warunkowały w znacznym stopniu uskoki i linie naruszeń tektonicznych czynne w tym okresie.

THE NEOCOMIAN IN THE WARSAW-RADOM AREA

Three blocks separated by tectonic lines may be differentiated in the Warsaw-Radom area on the basis of analysis of Lower Cretaceous; especially Neocomian sediments: Grodzisk block (Płock Basin), Magnuszew, and Radom blocks (Fig. 1). Throughout the area, the Lower Cretaceous begins with transgressive Upper Valanginian, resting on various members of the Upper Jurassic. Older members of the Valanginian and Berriasian are known from the margins of the Góry Świętokrzyskie Mts. In the Grodzisk and Magnuszew blocks. the Upper Valanginian is overlain by the Hauterivian whereas in some parts of the Radom block - directly by the Middle-Upper Albian.

In the studied area, Upper Valanginian and Hauterivian sediments represent two Iithostratigraphic formations interfinging with one another: Włoscławek (clastic) and Białobrzegi (carbonate-clastic) formations. The following lithofacies fields may be differentiated here (Fig. 1): claystone-sand-stone lithofacies I - inferred in marginal zone of sedimentary basin; sandstone-day lithofacies II - occurring in northern part and at south-western margin of the studied area; carbonate-clay lithofacies III -adjoining the latter and also occupying southern part of the Magnuszew block; carbonate-sandy lithofacies IV - present in areas characterized by increased thickness of the relevant strata (30 - 65 m - Żyrardów trough, a part of the Magnuszew block and a belt SW of Bąkowa): and clastic-carbonate lithofacies V, mainly characteristic of the Radom block. Lithofacies I and II belong 10 the Włocławek Formation, and III-V - to the Białobrzegi Formation. Sedimentary and tectonic processes active in the Valanginian and Hauterivian were markedly influenced by vertical movements of individual blocks, i.e. on activity of zones of tectonic disturbances.