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1 Annales Societatis Geologorum Poloniae

1 2019

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Middle to Late Jurassic carbonate-biosiliceous sedimentation and palaeoenvironment in the Tethyan Fatricum Domain, Krížna Nappe, Tatra Mts, Western Carpathians

Jach Renata, Reháková Daniela

Annales Societatis Geologorum Poloniae

2019

Vol. 89, No. 1

1--46

The Jurassic of the Alpine-Mediterranean Tethys was characterized by the formation of several interconnected basins, which underwent gradual deepening and oceanization. Sedimentation in each basin was influenced by a specific set of interrelated factors, such as tectonic activity, seawater circulation, climate, chemistry and trophic state of seawater as well as evolutionary changes of the marine biota. This paper deals with the Fatricum Domain (Central Carpathians, Poland and Slovakia), which in the Jurassic was a pull-apart basin on a thinned continental crust. The sedimentation history of this domain during the Bajocian-Tithonian and its governing factors have been revealed. Facies analysis of the Bajocian-Oxfordian deposits evidences considerable relief of the basin-floor topography. Deposits in the Western Tatra Mts represent sedimentation on a submarine intrabasinal high, whereas the coeval deposits of the eastern part of the Tatra Mts accumulated in a deeper basin. The basin succession began with Bajocian bioturbated “spotted” limestones and siliciclastic mudstones (Fleckenmergel facies). These were succeeded by uppermost Bajocian - middle Bathonian grey nodular limestones, affected by synsedimentary gravitational bulk creep. The coeval deposits of the intrabasinal high are represented by well-washed Bositra-crinoidal limestones with condensed horizons. Uniform radiolarite sedimentation commenced in the late Bathonian and persisted until the early late Kimmeridgian. The basal ribbon radiolarites (upper Bathonian - lower Oxfordian), which consist of alternating chert beds and shale partings, are a record of seawater eutrophication, a related crisis in carbonate production and the rise of the CCD, which collectively resulted in biosiliceous sedimentation. The overlying calcareous radiolarites (middle Oxfordian - lowermost upper Kimmeridgian) marked a gradual return to carbonate sedimentation. The return of conditions that were favourable for carbonate sedimentation took place in the late Kimmeridgian, when the red nodular limestones were deposited. They are partly replaced by basinal platy limestones (uppermost Kimmeridgian - Tithonian) in the Western Tatra Mts. This lateral variation in facies reflects a change in the sedimentary conditions governed by a bathymetric reversal of the seafloor configuration, attributed to a further stage in the pull-apart transcurrent tectonics of the Fatricum Domain.