Sedimentation regime and accommodation space in the Middle Jurassic-Lower Cretaceous on the eastern Russian Plate

This study presents new data on transgressive-regressive and accommodation-sedimentation regimes in the eastern Russian Plate during the Middle Jurassic-Lower Cretaceous. The proposed generalized scheme illustrating the combined effects of three major factors (eustasy, tectonic “noise”, and depositional gradient) controlling the deposition of sequences with different stratal architecture allowed us to quantify the parameters of sedimentation (5S) and accommodation (5A) for second- and third-order cycles. A distinctive feature of the evolution of the Middle Jurassic-Lower Cretaceous sedimentary basin is the excess of accommodation space over sediment supply, which was not conducive to creation of clinoforms. The difference between stacking patterns in individual time intervals and the estimated values of 5A/5S may be indicative of the presence of unidentified stratigraphic breaks in the Bathonian and Late Tithonian-Berriasian, which were accompanied by erosion and reworking of sand strata. The stepwise regressive-transgressive deepening during the Oxfordian-Early Tithonian and transgressive-regressive shallowing during the Late Tithonian-Berriasian were probably caused by short-term manifestations of local tectonic “noise”, and depositional hiatuses accompanied by the erosion of missing elements in the structure of third-order cycles. The Lower Cretaceous succession exhibits no mismatch between transgressive-regressive and retrogradational-progradational cycling, which provides another supporting evidence for a quiet tectonoeustatic and sedimentation regime during the Early Cretaceous compared to that of Middle-Late Jurassic time.