Recent studies on the Silurian of the western part of Ukraine

Abstract

ABSTRACT:Łuczyński, P., Skompski, S. and Kozłowski, W. 2016. Recent studies on the Silurian of the western part of Ukraine. Acta Geologica Polonica, 66 (3), 281-297. Warszawa.The paper summarises the effects of recent studies carried out by a team from the Department of Historical and Regional Geology of the Faculty of Geology, University of Warsaw on the upper Silurian of Podolia (western part of Ukraine).The sedimentary history of the Silurian succession of Podolia is characterised by its cyclic pattern, with shallowing-upward cyclothems. In the traditional interpretation, the occurrence of stromatoporoid beds within each cyclothem marks the deepest (or most open-marine) sedimentary environment within the cycle. According to the results of recent studies, their occurrence is connected rather with a relatively shallow-water environment and with high energy phenomena. A substantial reinterpretation of the main sedimentary processes governing the deposition and facies distribution on the shelf is presented. Particularly, there are recognised and described high-energy sedimentary events repeatedly punctuating the generally calm sedimentation that prevailed in the lagoonal settings, some of which are interpreted as tsunami induced.Further perspectives for studies on the Silurian successions of Podolia are also discussed. The main problem is the precise correlation of particular sections that are scattered over vast distances and developed in similar facies associations.

Tsunamites versus tempestites: Various types of redeposited stromatoporoid beds in the Devonian of the Holy Cross Mountains (Poland), a case study from the Ołowianka Quarry

“…Most commonly, these are represented as various coarse-grained deposits including calcarenites, carbonate breccias, bioclastic beds, and flat pebble conglomerates, usually interpreted as storm- [ 38 – 40 ] or gravitational associated deposits [ 41 , 42 ]. However, many similar deposits could also have resulted from tsunamis and associated phenomena, as has been demonstrated in the Silurian of Podolia [ 30 , 32 , 35 , 36 , 80 ]. The possibility of palaeotsunamis in the Holy Cross Mountain Devonian has been previously suggested by Kaźmierczak and Goldring [ 37 ].…”

“…The average recurrence intervals of even particularly fierce storms are at least an order of magnitude shorter than for tsunamis [ 84 , 94 , 110 ]. Therefore, in the absence of directly contradictory features ( Table 2 ), a storm interpretation is usually the preferred, and default, explanation [ 30 , 32 , 35 ], as in the parabiostrome.…”

“…Consequently, tsunamites are rarely identified in the sedimentary record, and the influence of tsunami induced phenomena on deposition is commonly underestimated [ 117 ]. In this context, studies of variously developed stromatoporoid beds, and particularly the analysis of the stromatoporoid morphometric features, provide a unique opportunity to identify palaeotsunamites in the geologic record [ 30 , 32 , 36 ]. Stromatoporoid facies are common among shallow water carbonate deposits from the Middle Ordovician to the Upper Devonian (Frasnian) [ 49 , 54 ] and in this timespan they may serve as potential indicators of palaeotsunamites.…”

“…Stromatoporoid reefs and biostromal accumulations that are, in many aspects, similar to those of the Holy Cross Devonian, are a typical component of the Upper Silurian succession of the Podolia region in western Ukraine [ 30 – 32 ]. They represent a zone of shoals and barriers along a carbonate shelf that fringed the Baltica continent (the East European Craton) with exposures ranging from Ukraine through the Baltic states to Gotland [ 27 , 33 , 34 ].…”