A thin sandy-oolitic formation [Jadowniki Formation (JF)] is described from the Upper Silurian of the ¸ysogóry Unit, Holy Cross Mountains (Central Poland). Its numerous trilobites (e.g. Homalonotus knighti, Acastella spinosa) and position in the lithological column testify for the late Ludfordian age of this formation. The sedimentary environment of the Jadowniki Formation is interpreted as extremely shallow-barrier environments with episodes of emersion and subaerial early diagenesis and erosion. However, these shallows were not connected with the nearshore belt of Baltica land and were separated from them by a belt of deep basin sedimentation – the graptholitic shales. Silurian shallow marine sediments of the ¸ysogóry Unit were deposited on top of a clastic wedge, which in the Ludlovian infilled the offshore – deep basin of the SW margin of the East European Craton. The wedge was probably connected with the process of dockage of new terranes onto the south-west periphery of the East European Craton The second factor that led to the development of shallow marine environments was probably the uppermost Ludfordian regressive event.
