Geological Quarterly, 2012, 56 (3): 475–492 DOI: http://dx.doi.org/10.7306/gq.1034 Mykolaiv Sands in Opole Minor and beyond: sedimentary features and biotic content of Middle Miocene (Badenian) sand shoals of Western Ukraine Anna WYSOCKA, Andrzej RADWAÑSKI and Marcin GÓRKA Wysocka A., Radwañski A. and Górka M. (2012) – Mykolaiv Sands in Opole Minor and beyond: sedimentary features and biotic content of Middle Miocene (Badenian) sand shoals of Western Ukraine. Geol. Quart., 56 (3): 475–492, doi: 10.7306/gq.1034 The Mykolaiv Sands are a huge lithosome of Middle Miocene (Badenian) age, accommodated within the Fore-Carpathian Basin in the Western Ukraine. Typically developed in the area of Opole Minor, it spreads across adjacent regions of Opole to cover an area of about 1300 km 2 . The varied sedimentary structures and ubiquitous burrows, indicate their development as a stack of sand shoals or related bodies, up to a few tens of metres thick, some of which temporarily reached sea level. Amidst the shoals, storm scours intermittently formed chan- nel-like infills, some with residual lags at the base. The reversed density stratification and/or an increasing gravity gradient involved mass movements, some of which may have been triggered by seismic shocks focused at the shore or the adjacent hinterland of Podolia and Volhynia. Special attention is paid to the diverse fossils, all taphonomically filtered (aragonite shells and chitinous carapaces being lost), but which locally are mass-aggregated. They typify particular sand sets/bodies, to form allochthonous assemblages, some members of which (the cirripedes Scalpellum and Creusia, the shark Hemipristis, the ray Myliobatis) are newly recognized in the Ukrainian part of the Fore-Carpathian Basin. The others enrich considerably the faunal content of the Middle Miocene (Badenian) Paratethyan basins, either in terms of taxonomic diversity, or the eco-taphonomy of selected taxa (the starfish Astropecten, diverse echinoids). The whole faunal content of the Mykolaiv Sands may owe its profuse development to the global Middle Miocene Climatic Optimum of early Badenian age. Anna Wysocka, Andrzej Radwañski and Marcin Górka, Institute of Geology, University of Warsaw, ¯wirki i Wigury 93, 02-089 Warszawa, Poland, e-mails: anna.wysocka@uw.edu.pl, magurka@uw.edu.pl (received: April 3, 2012; accepted: May 29, 2012; first published online: August 29, 2012). Key words: Western Ukraine, Middle Miocene (Badenian), eco-taphonomy, burrows, depositional structures, sedimentology. INTRODUCTION The enormous accumulation of the Middle Miocene (Badenian) Mykolaiv Sands in Western Ukraine has long been known (NiedŸwiedzki, 1879; Hilber, 1882; £omnicki, 1897, 1898; Jahn, 1937; Malicki and Jahn, 1937; Teisseyre, 1938; Pazdro, 1953; Kudrin, 1966; Wysocka and Jasionowski, 2006), but never systematically described. This lack of interest has supposedly been caused by the paucity, or absence, of body fossils which occur abundantly in other coeval sands spreading widely throughout Western Ukraine. The sand-mass in ques- tion, typically developed around the small city of Mykolaiv (south of Lviv), situated near the valley of the Dnister River in the south, extends northwards as far as the vicinity of Lviv (Fig. 1). In their southern part, near Mykolaiv, the sands are poorly exposed along the slopes of gentle hills, and are covered by arable soil or forested, elsewhere. Their study has involved access to many commercial sand-pits or quarries established in recent decades. When the present authors started with their in- vestigation (Radwañski and Wysocka, 2001), it appeared that the Mykolaiv Sands contained a well-nigh inexhaustible spec- trum of sedimentary structures, both of physical and of biogenic origin. Moreover, their content of body fossils turned out to be not as scarce as thought formerly (see Radwañski et al., 2012). The Mykolaiv Sands, as an informal lithostratigraphical unit, was distinguished by Petryczenko et al. (1994, fig. 2) and, as such, is used in the present paper. REGIONAL SETTING The Mykolaiv Sands extend from the southwestern margin of the East European Platform to border the tectonically active Carpathian Foredeep (Fig. 1). They rests upon a Laramide basement of Upper Cretaceous (Maastrichtian) marls, the to-