The Drzewica Formation is a geologic formation in Szydłowiec, Poland. It is late Pliensbachian 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 where recovered on the Brody-Lubienia borehole, with a lower part exposed on the village of Smilów 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 damp ecosystem. As many studies of the formation share, Drzewica shows 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, lower Bagå Formation, upper Neringa Formation. Abandoned informal units in Poland: upper Sawêcin beds, Wieluñ series or Bronów series.
Stratygraphic Profile
Depositional systems
There are several Types os Seashore Stratification Seen On the Drzewica Formation. Starting with the shore prograding cycle, where the nearshore deposits show detailed Hummocky cross-stratification, at the time are covered by thin beach-welded facies showing irregular “massive” bedding and numerous Plant roots penetrating down from the undulated bounding surface. Superimposed are fine grained, very well sorted Sandstones with giant tabular Cross-bedding set interpreted as beach EolianDune with complete Plant remains buried in the wind-transported Sand. The Direction of the Wind sedimentation is clearly visible on this deposits, where the stratification of the sand is well oriented. Those deposits are abundant on the Antecki quarry. The most related to the shores, probably barrier-Lagoon and Delta depositional systems are clearly visible on the Smilów Quarry, where the exposure shows different lithofacies and strata, including fine-grained, white and light-grey Sandstones with Hummocky cross-stratification, with a series of tabular and trough Cross-bedding sets, probably related to nearmarine depositional subsystem. A more fine-medium-grained, grey to brownish sandstones also with flat-tabular-horizontal bedding with abundant drifted Plant Fossils and plant remains in situ is considered to be part of a clear foreshoreb–arrier–Eolian depositional subsystem, proabably related to a series of Dune fields, related to the Sea Barriers. Kaolinized grey Mudstones with abundant Dispersed plant roots are related to more lagoonal depositional subsystems. The slightly smaller and fine built, brownish and yellow Sandstones that show detailes Cross-bedding are related to a more alluvial deposition, proabablly from the influence of a local Channel. On the Main Smilów Quarry the dominant shoreface depositional subsystem show detailed marks of clear Palaeocurrent directions, dispersed trough Cross-bedding inclinations that point to the West. There has been measurements of the Wave-formed ripple that approximately reflects a shoreline orientation. Thanks tothe wave ripple crests orientation and the orientation of fossil tree logs it was indicated an inclination of the inclined tabular Foreset bed continuing across the whole outcrop. These Foreset bed show a more pronounced inclination thanks to seaward-dipping Clinoforms, what reflects the original inclination of a barrier slope, with the sum of palaeocurrent pointing to south-west.
Fungi
Paleofauna
Along the Early Jurassic, there was a mostly marginal-marine, deltaic and continental sedimentation that prevailed in the area of Poland. The Marine of Polyhaline character conditions occurred mainly in the Pliensbachian, due to a flooding of the Polish Basin. due to that, Pliensbachian sedimentation in Pomerania developed in a shelf basin that attained depths of about 100 m, below the stormwave base. As the latest Pliensbachian began, the climate changes to a more cold environment, as prove the presence of ice sheets on northern latitude facies of the same age. That led to changes in salinity. The Drzewica Formation was influenced by an ancient swampy-lagoonal sub-system, with Deltaic currents depositing fluvial sediments. The Main Boreholes show eustatic changes on the marine conditions, with a retreat of the sea level, leading to the appearance of vegetation and abundant pollen on the uppermost parts of the formation. The regressive phase of sea level is represented by the Komorowo Beds and Upper Slawecin Beds along with the Drzewica Formation. As the level of the sea recovered on the Toarcian, mostly of the setting turn out to be a bathial marine bottom. There is a high report of footprints, with different sizes, that range from small to large animals of various groups. The Smilow Quarry Tracksite is the main Borehole and setting for the Footprints. Those are the only ones recovered from the Late Liassic of Europe. The footprints are related to mostly lagoonar facies, unlike the Vegetation, that appears on Deltaic facies. Brackish deposits are relates to Brachiopods and other molluscs and lime animals. The presence of Late Pliensbachian common ammonoids and several vertebrate clades connects the marine fauna with similar environments of the same age across Europe. The Drzewica Fauna is also, one of the few from the Pliensbachian-Toarcian Anoxic event recorded worldwide, specially referred to the vertebrate fauna reported.
Invertebrates
Annelida
Bivalve Ichnofossils
Blackish bivalves were reported from the formation. They may be evidence of an ancient water system.
Bivalvia
Ammonites
Limuloidea
Vertebrates
Chondrichthyes
Actinopteri
Unidentified fin spines are known from this formation.
Sarcopterygii
Rhynchocephalia
Testudinata
Cynodontia
Crocodrylomorpha
Theropoda
Sauropodomorpha
Ornithischia
Plants
The sediments of this formation in Smiłów Quarry are mainly fine-grained Sandstones with small over-minerals. Diagonal layers and wave strata appear in them, where there is also traces of root plants with numerous plant remains. Juzuz Karaszewski observed in the Drzewica Sandstone vertically preserved plants, and on this basis he derived a possible Dune-related origin of these sediments. More recent studies suggest an environment of shallow seafront and beach, which of course does not exclude the presence of Aeolian zones there. Lithofacies on the Smilów Quarry shows slightly inclined Beach foresets and abundant Plant roots in a series of barrier/foreshore–ackshore–eolian dune facies, that include even plants buried in whole Dune, while drifted plant fossils and tree logs occur on the main depositional surface. This inclined surface exposes most likely a long period of non deposition and washed plants, recovering at the same time the original tilt of the local beach.
