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Dynamic evolution of the Campanian and Maastrichtian (Upper Cretaceous) of the Miechow Synclinorium is presented. Through chronostratigraphic analysis, the geometry of the Campanian and Maastrichtian of the area is interpreted, while microfacies analysis allowed determination of some of the paleoenvironmental parameters (rate of sedimentation, bottom condition and terrigenous input). The chronostratigraphy is based on inoceramid biostratigraphy. Nine inoceramid zones are recognized: Sphenoceramus patootensiformis, Sphaeroceramus sarumensis-Cataceramus dariensis and ‘Inoceramus’ azerbaydjanensis-‘Inoceramus’ vorhelmensis, ‘Inoceramus’ tenuilineatus, Sphaeroceramus pertenuiformis, ‘Inoceramus’ inkermanensis and ‘Inoceramus’ costaecus- ‘Inoceramus’ redbirdensis (Campanian); Endocostea typica and Trochoceramus radiosus (Maastrichtian). Five unconformities (isochronous in the study area) represented by horizons of slower sedimentation rate, were recognized. They correlate with eustatic sea-level changes, well recorded in European successions (Jarvis et al. 2002, 2006; Niebuhr et al. 2011). Unconformity horizons allow six alloformations to be distinguished. The thickness of particular chronostratigraphic units within the Campanian and Lower Maastrichtian increases progressively toward the axis of the Danish-Polish Trough, which indicates that the inversion of the trough could not have started before the Late Maastrichtian.

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The stratigraphical distribution of Porosphaera globularis, a common calcareous sponge in the Upper Cretaceous (mostly Campanian and Maastrichtian) of Poland was studied. The presented material, both new and from museum collections, comes from the Campanian of the Miechów Synclinorium, in southern Poland, and from the Lower Campanian of Mielnik in the south-eastern part of the Mazury-Podlasie Homocline, in eastern Poland. The significance of the species in extra-regional correlation, its palaeobiogeography and stratigraphical potential is critically reviewed.

The silicon (Si) cycle in the modern ocean might still be representative of some of the processes that occurred in the Si‐depleted post‐Eocene oceans resulting after the expansion of diatoms. However, silicon‐rich pre‐Eocene seas, where sponges and radiolarians were major Si users before the emergence of diatoms, were radically different from modern ocean scenarios. The spatial and temporal evolution of Si cycling in Earth history is recorded in geological deposits and could be reconstructed by petrographic and mineralogical analyses. The thick successions of carbonate siliceous rocks deposited in marine environments during the Paleozoic and Mesozoic indicate the significant role of Si outflow from the Si cycle via burial in sediments. The aim of this study is to fill an important gap in knowledge concerning the functioning of the main silicon sink in the oceans: burial in sediments. Si outflow from the marine biogeochemical Si cycle occurs via early diagenetic silica crystallization within seabed mud. The mechanisms leading to Si binding in silica minerals are a complex process controlled by abiotic global events, biological activity of silicifiers and geochemical conditions mediated by microbes. This study concentrates on reconstructions of the mechanisms of Si outflow from the Si cycle by silica polymorph crystallization below the seabed surface and was realized through mineralogical and microtextural analyses of the main components of Upper Cretaceous carbonate–siliceous rocks.

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ABSTRACT:Jurkowska, A. and Uchman, A. 2013. The trace fossil Lepidenteron lewesiensis (Mantell, 1822) from the Upper Cretaceous of southern Poland. Acta Geologica Polonica, 63 (4), 611-623. Warszawa. (Mantell, 1822) is an unbranched trace fossil lined with small fish scales and bones, without a constructed wall. It is characteristic of the Upper Cretaceous epicontinental, mostly marly sediments in Europe. In the Miechów Segment of the Szczecin-Miechów Synclinorium in southern Poland, it occurs in the Upper Campanian-Lower Maastrichtian deeper shelf sediments, which were deposited below wave base and are characterized by total bioturbation and a trace fossil assemblage comprising Planolites, Palaeophycus, Thalassinoides, Trichichnus, Phycosiphon, Zoophycos and Helicodromites that is typical of the transition from the distal Cruziana to the Zoophycos ichnofacies. L. lewesiensis was produced by a burrowing predator or scavenger of fishes. The tracemaker candidates could be eunicid polychaetes or anguillid fishes. Lepidenteron lewesiensis