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The phosphatized sponges from the Santonian (Upper Cretaceous) of the Wielkanoc Quarry (southern Poland) as a tool in stratigraphical and environmental studies

Olszewska-Nejbert D., Świerczewska-Gładysz E.

Acta Geologica Polonica

2009

Vol. 59, no. 4

483-504

Phosphatized sponges from the Santonian of the Wielkanoc Quarry are represented by 11 species of Hexactinosida and 16 species of Lychniscosida. Their species composition is most similar to the Micraster coranguinum Zone fauna (Middle Coniacian - Middle Santonian) of England. Three preservational groups of sponges are distinguished: 'white', 'beige' and 'dark'. They are infilled by phosphatized foraminiferal/foraminiferal-calcisphere wackestone and are contained in the marly calcareous inoceramid packstone. The sponges indicate a calm and relatively deep (> 100 m) life environment. After burial, phosphatization and exhumation, the fossil sponges were redeposited in Upper Santonian strata. The 'white' and 'beige' groups were transported laterally over a very short distance or represent lag deposits. The rolled and crushed sponges of the 'dark' group were exhumed and phosphatized more than once. They could be redeposited (reworked) nearly in the same place and/or transported from some longer distances (but not from outside the Cracow Swell). The phosphatized sponges document the former presence in the area of part of theMiddle Coniacian through Middle Santonian succession, which was removed secondarily by subsequent erosion.

Development of the Turonian/Coniacian hardground boundary in the Cracow Swell area (Wielkanoc quarry, Southern Poland)

Olszewska-Nejbert D.

Geological Quarterly

2004

Vol. 48, No 2

159--170

During the Turonian and Coniacian, up to the early Santonian, the present-day Polish Jura Chain composed a positive submarine palaeotectonic feature referred to as the Cracow Swell, separating the deeper Opole Trough to the SW from the Danish-Polish Trough to the NE. At present the Turonian and Santonian deposits at themargin of the Polish Jura Chain and the Miechów Trough are fragmentarily preserved. They are characterised by numerous stratigraphic hiatuses and the occurrence ofmany unconformity surfaces.One of themost spectacular unconformities is a hardground at the Turonian/Coniacian boundary described herein from the vicinity of Wielkanoc. Its development took place in several stages. Threemain stages can be distinguished with a compositemiddle stage. In the first stage during the early late Turonian, a gradual drowning of the carbonate Cracow Swell took place followed by eutrophication of the environment. The second stage from the latest Turonian to the earliest Coniacian was linked with a crisis of a carbonate sedimentation leading to its cessation. A firmground with Thalassinoides traces was formed, followed by a hardground with bivalve borings and ?Trypanites. Carbonate- clastic sedimentation recommenced at least twice (with quartz arenites), followed by rejuventation of burrows and/or borings, lithification of the sediment, glauconitization and phosphatization, as well as the development of microbial mats undergoing early phosphatization. This led to the formation of phosphatic stromatolites. In consequence a composite hardground was formed. The third stage took place in the late early Coniacian. Carbonate-clastic sedimentation resumed. Deposits, developed as carbonate arenites with quartz and glauconite admixtures (non-phosphatized), filled the last generation of the rejuvenated burrows and finally covered the hardground.