Sedimentation in a synclinal shallow‐marine embayment: Coniacian of the North Sudetic Synclinorium, SW Poland

Abstract

This study is a reconstruction of the Coniacian palaeogeographic and palaeoenvironmental development in the North Sudetic Basin, a synclinal trough within the Late Cretaceous Central European seaway linking the Boreal and Tethyan marine provinces. The basin formed as an early side effect of the Alpine orogeny combined with the mid-Cretaceous eustasy, and crucial stages of its evolution occurred during the Coniacian. The basin in the early Coniacian was a long and narrow shallow-marine embayment with a hypothetical (non-preserved) bayhead strait funnelling tidal currents. Coalescing tidal sand ridges formed a littoral platform that prograded from the bayhead zone along the basin axis, impinged on laterally by the basin-margin shoreface and local river deltas. A mid-Coniacian forced marine regression and closure of the bayhead strait, attributed to the Alpine tectonism combined with eustasy, brought about a dramatic change in the basin, whereby the basin-wide littoral sand platform emerged and turned briefly into a denudated coastal plain. The late Coniacian eustatic marine transgression formed an in-place growing coastal sand barrier at the outer edge of the former littoral platform, sheltering a paralic limno-lagoonal plain with peat-forming mires. The coastal barrier was eventually drowned by the sea and maximum marine flooding occurred, followed by a normal regression recorded as a rapidly upwards-shallowing succession of offshore-transition to fluvio-deltaic deposits. This case study of the sedimentation pattern in an evolving, tectonically controlled marine embayment contributes to the existing facies models for estuarine embayments formed by a passive marine drowning of large fluvial or glacial valleys. K E Y W O R D SIchnofacies, lithofacies, North Sudetic Basin, paralic plain, shoal-water deltas, shoreface, tidal sand ridges

Not simply volcanoes – The Geoheritage of the Cretaceous System in the Land of the Extinct Volcanoes Geopark, West Sudetes (SW Poland)

“…Chronologically, they cover the Cenomanian -Santonian interval of the Late Cretaceous, which is some 15 million years long. Cretaceous rocks are exclusively marine in origin and interpreted as sediments of a shallow epicontinental sea, representing a variety of facies, from nearshore coarse sandstones and locally sandy conglomerates to deeper-water calcareous sandstones, mudstones and claystones (Milewicz, 1997;Leszczyński, 2018;Leszczyński & Nemec, 2020). Coarse-and fine-grained sediments alternate in the litostratigraphic profile, so that coarse-grained sandstone series occur repeatedly within the Cenomanian, Turonian and Coniacian succession.…”

“…9). It is 14 m high on the downslope side and has a rectangular outline, with generally vertical walls, which expose a variety of sedimentary structures: large-scale cross-stratifications in the lower part, ripple cross-laminations and plane-parallel stratifications in the upper part, interpreted to indicate tidal bars (sand ridges) (Leszczyński & Nemec, 2020). These discontinuities, in turn, influence the process of surface weathering that produced various small-scale cavernous features and narrow ledges (Fig.…”

“…Photo P. Migoń exceed 5 m high. It is also an important geological locality, since unrestricted access allows one to examine a large section of the vertical sedimentary succession, otherwise exposed in working quarries (Leszczyński & Nemec, 2020) and therefore, essentially off limits for an individual geotourist.…”

Exploring Causal Relationships for Geoheritage Interpretation — Variable Effects of Cenozoic Volcanism in Central European Sedimentary Tablelands

“…The most widespread sedimentary rocks in all three geoparks are sandstones and mudstones (siltstones) of Late Cretaceous age, deposited within an interval from Cenomanian to Coniacian/Santonian, over some 15 million years (Skoček and Valečka 1983;Milewicz 1997). Coarser and finer variants, with variable content of quartz, alternate in the vertical profile, reflecting changing palaeogeographic conditions of the epicontinental sea (Milewicz 1997;Uličný et al 2009;Leszczyński and Nemec 2019;Nádaskay et al 2019). Various localities (geosites -existing or potential) offer insights into the sedimentary architecture of Cretaceous deposits and help to unravel the complex history of sedimentation and erosion (Adamovič et al 2006(Adamovič et al , 2010Migoń and Pijet-Migoń 2021).…”

Anatomy of a mixed bioclastic–siliciclastic regressive tidal sand ridge: Facies‐based case study from the lower Pleistocene Siderno Strait, southern Italy

“…Case studies documenting tidal sand ridges in the rock record of ancient tidal straits are scarce (e.g. Messina et al, 2014;Chiarella et al, 2020;Leszczy nski & Nemec, 2020) and examples of ridges developed during marine normal to forced regressive stages are rarer (e.g. Wu et al, 2017).…”