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Facies and sedimentation of Coniacian deposits of the Kraków Swell in the Wielkanoc area (southern Poland)

Olszewska-Nejbert D., Świerczewska-Gładysz E.

Geological Quarterly

2013

Vol. 57, No. 1

1–-16

Coniacian deposits, ca. 1.5 m thick, cropping out in the Wielkanoc Quarry, north of Kraków in southern Poland, consist of firm, nodular and, less commonly, marly limestones with horizons of in situ, slightly phosphatized hexactinellid sponges and thick-shelled inoceramid bivalves. The succession is composed of foraminiferal-inoceramid packstones with common sand-sized quartz and glauconite grains at the base, passing upwards into foraminiferal or foraminiferal-inoceramid wackestones with or without rare glauconite. A microfacies analysis shows that planktonic foraminifers are the dominant forms, while benthic forms are rare. The facies indicates that sedimentation in the Wielkanoc area on the Kraków Swell, which separated the deeper Mid-Polish Trough Zone to the north-east and the Opole Trough Zone to the south-west, was generally calm (documented by abundant wackestones) and slow (indicated by the dominant sedimentary “coccolith system” and presence of glauconite) during the Coniacian. Rare episodes of non-deposition are recorded by episodes of phosphatization and minor intra-Coniacian discontinuity surfaces. The presence of hexactinellid sponges in the section studied are consistent with a calm environment, below the storm-wave base, with low rates of sedimentation. Subhercynian (latest Turonian–Coniacian Ilsede Phase) local tectonic movements had an important influence on the evolution of the region. They presumably led to subsidence of the Wielkanoc Block during the Early Coniacian. These movements were probably associated with activity on the Kraków–Myszków Fault Zone.

Injection dykes as evidence of Campanian synsedimentary tectonics on the Kraków Swell, southern Poland

Kołodziej B., Szulc J., Machaniec E., Kędzierski M., Duda M.

Annales Societatis Geologorum Poloniae

2010

Vol. 80, No 3

285-301

The topmost part of the Oxfordian limestones, building the Zakrzówek Horst in Kraków, is featured by a network of minute fissures, filled with Upper Cretaceous limestones. Fissures are dominantly subhorizontal, anastomosing and polygonal in plane. They are filled with white limestones representing mostly foraminiferal- calcisphere wackestones, with subordinate amount of quartz pebbles and fragments of stromatolite coming from the latest Turonian-?Early Coniacian conglomerate overlying Oxfordian basement. The fissures are seismically- induced injection dykes. In contrast to gravitationally-filled neptunian dykes the recognised injection dykes were filled by overpressured soft sediments. Foraminifera within some dykes are abundant, and dominated by planktonic forms, which indicate the Early/Late Campanian age (Globotruncana ventricosa and Globotruncanita calcarata zones) of the filling, and hence date also the synsedimentary tectonics. Abundant and diversified keeled globo- truncanids in the Campanian of the Kraków region are recognised for the first time. Other important findings at the studied section include karstic cavities featuring the surface of the Oxfordian bedrock filled with conglomerates of the latest Turonian-?Early Coniacian age based on foraminifera and nannoplankton, and lack of Santonian deposits, which elsewhere are common in the Upper Cretaceous sequences in the Kraków region. The discovered Campanian dykes provide new evidence for the Late Cretaceous tectonic activity on the Kraków Swell related to the Subhercynian tectonism, which resulted among others in stratigraphic hiatuses and unconformities characte- ristic of the Turonian-Santonian interval of this area.