The epicontinental Lower Jurassic of Poland

• Autorzy: Pieńkowski G.
• Konferencja: International Congress on the Jurassic System (7 ; 06-18.09.2006 ; Kraków, Poland]
• Języki publikacji: EN

Abstrakty

EN

During the Early Jurassic times terrigenous, continental, marginal-marine and marine sediments up to 1400 m in thickness were deposited in a large epeiric basin extending across Poland. These strata are defined herein as the Kamienna Group, which is subdivided into 13 lithoformations (Fm.). Lithofacies description, recognition of depositional systems and subsystems and determination of their fluctuation in space and time allowed a high-resolution sequence stratigraphic analysis. Sedimentation in the shallow (usually not more than 10-20 m deep), epeiric Early Jurassic basin of Poland was particularly sensitive to reflect changes in sea level. Except for the ammonite-bearing Pliensbachian deposits in Western Poland, biostratigraphical resolution in marginal-marine and continental deposits is usually of a lesser precision. However, an internally consistent sequence stratigraphic scheme of Poland can be compared with fossiliferous marine sediments of the Ligurian cycle of United Kingdom and France. The minor sequences identified within the Ligurian cycle play a very important role in correlation as they can be recognized in the Polish Basin. Concerning the range of sea level changes, the Exxon model was also adopted and ten of the Exxon Early Jurassic depositional sequences (I-X) were identified in the Polish Lower Jurassic. Transgressive systems tracts prevail in sedimentary record and are represented either by retrogradational or aggradational facies architecture, and high-stand systems tracts are represented by progradational facies architecture. A typical marginal - marine parasequence is usually more complex than a simple "quick flooding-gradual prograding" model - transgressive deposits are usually preserved and "parasequence maximum flooding surfaces" can be distinguished. Correlative significance of transgressive surfaces is enhanced when they are coupled with their nonmarine correlative surfaces. Development of transgression with its coeval effects in continental deposits is discussed and non-marine correlative surfaces of the transgressive surfaces are documented - a "step-wise", retrogradational development of transgression with its nonmarine correlative surfaces within alluvial and deltaic systems is particularly well recognized in the Early Jurassic Polish Basin. The regional cross sections and cross sections of the whole Polish Basin showing dominant depositional systems and sequence stratigraphic correlation, as well as "time-tuned" palaeogeographical maps of the Polish Basin in Early Jurassic are presented. Despite existence of some regional dislocation zones occurring along the edges of the Mid-Polish Trough, which shaped the sedimentation and sediment thickness contrast (for example the Nowe Miasto-Iłża Fault), a gradual decrease of sediment thickness outwards the axis of the Mid-Polish Trough prevails. Additionally, occurrence of conspicuous zones of increased subsidence, which are actually perpendicular to the Mid-Polish Trough (for example the "Mazurian Way") indicates that there is no reason to regard the Mid-Polish Trough in any respect as a "rift basin", at least in the Early Jurassic times. Depositional history of the Early Jurassic in Poland provides a good case study concerning sequence correlation between marine and non-marine sedimentary successions.

Słowa kluczowe

EN

Lower Jurassic; Poland; continental and marginal marine depositional systems; sea-level changes; continental correlatives; transgressions; sequence analysis; sequence stratigraphic correlation

• Wydawca: Państwowy Instytut Geologiczny - Państwowy Instytut Badawczy
• Czasopismo: Volumina Jurassica
• Rocznik: 2006
• Tom: Vol. 4, no. 1
• Strony: 268--268

Twórcy

autor

Pieńkowski G.

• Department of Regional and Petroleum Geology, Polish Geological Institute, ul. Rakowiecka 4, PL-00975 Warszawa, Poland,