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Correlation and comparison of Jurassic deposits in republics of Belarus and Lithuania, and Russian Federation in transboundary region

Makhnach V. V.

Geology, Geophysics and Environment

2012

Vol. 38, no. 4

500--502

Correlation and comparison of the Jurassic deposits of Republic of Belarus, Republic of Lithuania and Kaliningrad region of the Russian Federation transboundary region is an important time milepost in studying of a paleogeographical situation of the western part of the East European Platform. The geologist Ullman began to study Jurassic deposits of the Republic of Lithuania in 1830s (Grigyalis 1958). He investigated river Venta in the town of Papilany. For the first time, geologist A.E. Gedroyts conducted research of the Jurassic deposits in the territory of Belarus. He found erratic boulders in the Białowieża forest at the beginning 1880s (Mityanina 1982). Correlations of the Jurassic deposits were repeatedly undertaken in this region. In 1922, N.F. Bliodukho discussed the similarity between "Western" and "Russian" Jurassic on basis of the mollusk analogies. The second attempt was made within the project of UNESCO No. 86 of the International program of geological correlation The East European Platform (southwest region) only in 1985. Correlations were carried out within the project "Peritetis". The newest research of the Jurassic deposits of Belarus revealed the series of paleogeographical and sedimentological features (Makhnach 2011). This research revealed, a glacial exaration of the Jurassic deposits from Grodno (Republic of Belarus), Druskininkay and Premay (Republic of Lithuania) as a distinctive feature of the Lithuanian-Polish Monocline. The considered transboundary region includes (from the North to the South) following tectonic structures: Baltic Syneclise, western slope of the Latvian Saddle, Mazursko-Belorusskaja Anteclise and Podlyassko-Brestsky Hollow. Desrciptions and paleontological material from stratigraphic wells, which encountered Jurassic deposits were used as a research material. Data from following wells were used: stratigraphic wells Gvardeyskaja-57 and Bely Yar-1 for the Kaliningrad region, Yoty's stratigraphic well for the Republic of Lithuania, stratigraphic wells Vysokoe-77 and Brest-52 for the territory of Belarus. The correlation of regional data and comparison of paleogeographical events showed that the most complete section of the Jurassic deposits for this area is located in the territory of the Kaliningrad region - a stratigraphic well Gvardeyskaja 57. For the territory of Belarus, the most complete section of Oxfordian is presented in the stratigraphic well Vysokoe-77, and Callovian deposits are best represented in the stratigraphic well Brest-52. Paleogeographical reconstruction shows that the sea was absent in the territory of Belarus, but the plentiful river network drained the Polesye Saddle through the Svislochsky snap in Early Callovian. Lowland with wetlands existed in Early Callovian during the beginning of transgression in the transboundary region of Lithuania, Belarus and the Kaliningrad region. The maximum transgression from the Polish Sea occurred during the Kosmo-ceras jason time (Middle Callovian). At this time, connection through the Pripyat Passage and through the southern passage systems with the Central Russian Sea was established. The second maximum transgression in this region happened during the Quenstedtoceras maria time (Early Oxfordian), and the communication with the Central Russian Sea was reestablished in the period of Cardioceras cordatum (Early Oxfordian). Completeness of Middle and Upper Oxfordian cuts from the territory of Belarus isn't clear and requires further paleontological research. Lithological differences and time of sediment accumulation reveal different sedimentation conditions. This fact indicates various movement directions of tectonic structures. It should be noted that unidirectional movements (immersion) effected all tectonic structures during the maximum sea transgressions. Differences in regions, where Jurassic sediments were deposited, were also studied. In the second half of Late Callovian, the Podlyassko-Brestsky Hollow underwent immersion and a flexure towards the Stryysky Deflection while Mazursko-Belorussky Anteclise was under conditions of tectonic rest. During Cardioceras cordatum time (Early Oxfordian), the submerging of Pripyat passage northern part was amplified. Most likely, the Polish Sea started to recede from the major part of the territory of Belarus during Middle Oxfordian, marking a new land stage of the territory. The buckling of the Latvian Saddle towards the Baltic Syneclise was observed within the territory of Lithuania. Paleontological data are also interesting. Existence of coral reeves in the territory of Lithuania (Grigyalis 1958) testifies the prevalence of northwest currents from Peritetis areas, and also does not reject the hypothesis about the Northern (Baltiyskii) Passage connecting the Polish and Central Russian seas. Biota features indicate the existence of benthonic currents in Late Callovian and difficult fauna exchange between Lithuanian and Belarusian regions.