O jurze środkowej między Krośniewicami i Płockiem

Abstract

ON THE MIDDLE JURASSIC DEPOSITS BETWEEN KROŚNIEWICE AND PŁOCKSummaryIn the Kujawy region the Middle Jurassic deposits crop out under the Tertiary cover only within a narrow belt, in the vicinity of the Kłodawa salt plug. In the remaining areas, the Middle Jurassic deposits, disclosing their sedimentary continuity, rest under the lowermost Upper Jurassic (Figs. 1 and 2). Hare, a complete section has been encountered, from Aalenian to Callovvian inclusive (Fig. 3). Ammonite evidences do not concern all the stages in the area considered. The bottom boundary of the Middle Jurassic deposits marked by the Lower Aalenian marine sandstones, which rest on the continental Liassic formations. The Upper Aalenian its characterized here by an ammonite of the genus Ludwigia sp. and by a foraminifer Reinholdella dreheri B a r t. Stratigrahical situation of Bajocian is marked out by its vertical position in the lithological section between the evidenced Upper Aalenian and Lower Kujawian. In the entire area here considered this latter is well documented by ammonite fauna. The deposits of Lower Middle Bathonian Age have also their-rich ammonite fauna, unfortunately, however, within the Łęczyca-Ozorków region only. The Upper Bathonian is lacking any detailed faunistic evidences. Only at the beginning of the Callovian, the ammonite fauna appeared within the regions of Łęczyca and Ciechocinek.The greatest thickness of the Middle Jurassic deposits has been ascertained (Fig. 4) to occur in the areas pierced by bore holes Gostynin IG 3 (831,8 m) and Krośniewice IG 1 (700,0 m). The seismical data from the vicinity of bore hole Głogowiec IG 1 show that most probably these deposits are 900 m in thickness. Towards Łęczyca and Ozorków the thickness decreases to 650 and even 400 m. Within the Warszawa trough the thickness is considerably smaller, and amounts to 353.9 m in bore hole Gostynin IG 1/1a, and 306,0 m – in bore hole Gostynin IG 4.Facial changes observed to occur in the Kujawy region are related to the transgressive impulses of the Middle Jurassic sea. The Polish Lowland area is characterized by a transgressive character of the deposits of Garantiana garantiana zone, by the transgression throughout the Upper Kujawian, Lower Bathonian and Middle Bathonian times, by its maximum in the Upper Bathonian as well as by a transgression at the Upper Callovian time. In the marginal zones of the Lowland basin these deposits rest transgressively either on the lower members of the Middle Jurassic, or on the older deposits. At that time, the deposits were hare more arenaceous, particularly in the vicinity of Łęczyca and Ciechocinek. In the Krośniewice-Głogowiec area, and in the vicinity of bore hole Gostynin IG 3, clay facies predominates, and both these areas reveal the quietest sedimentation within the entire Kujawy region.