Drzewica Formation

The Drzewica Formation (also called Drzewica Series/Seria Drzewicka or Serii Drzewiekiej and in older literature Brónow Series) is a geologic formation in Szydłowiec, Poland. It is Pliensbachian in age. Vertebrate fossils have been uncovered from this formation, including dinosaur tracks. The Drzewica Formation is part of the Depositional sequence IV-VII of the late lower Jurassic Polish Basin, with the IV showing the presence of local Alluvial deposits, with possible meandriform deposition origin, dominated in Jagodne and Szydłowiec, while delta system occurred through the zone of the modern Budki. The sequence V shows a reduction of the erosion in the Zychorzyn borehole of the Drzewica Formation, showing changes on the extension of the marine facies, where upper deposits change from Alluvial to Deltaic-Seashore depositional settings. VI-VII facies were recovered on the Brody-Lubienia borehole, with a lower part exposed on the village of Śmiłów that shows a small fall of the Sea level. The stathigraphic setting of the dinosaur tracks reported from the formation suggest a Seashore or Deltaic barrier. Body fossils reported include bivalves, palynology, fossil trunks, roots. Trunks of coniferous wood, especially Cheirolepidiaceae and Araucariaceae trees show the occurrence of vast coniferous forests around the tracksite. The association of forests and dinosaur megafauna on the Pliensbachian suggests also a colder and specially dry ecosystem. Drzewica deposits where in part to be a gigantic shore barrel, setting at the time where the Polish basin sea was at its lowest point. Other related units are Fjerritslev or Gassum Formation (Danish Basin), Hasle & Sorthat Formation (Bornholm), upper Neringa Formation (Lithuania) and abandoned informal units in other regions of Poland: upper Sawêcin beds, Wieluñ series or Bronów series.