Integrated biostratigraphy and carbon isotope stratigraphy of the Upper Jurassic shallow water carbonates of the High-Tatric Unit (Maly Giewont area, Western Tatra Mountains, Poland)

摘要

New biostratigraphical and carbon isotope data are presented for the Upper Jurassic limestones of the Raptawicka Turnia Limestone Formation (High-Tatric Unit, Western Tatra Mountains, Poland) from the Maly Giewont area. The Kimmeridgian, Lower Tithonian and lower part of the Upper Tithonian have been identified on the basis of calcareous dinocysts and calpionellids. Eight microfossil biozones are distinguished: acme Fibrata, acme Parvula, Moluccana, Borzai, Tithonica-acme Pulla(?), Malmica, Chitinoidella and Crassicollaria (pars). The Kimmeridgian/ Tithonian boundary is inferred at the top of the Borzai Zone, 76 m above the base of the Raptawicka Turnia Limestone Formation. The microfossil stratigraphy suggests a late Early Kimmeridgian age (acme Parvula Zone) for the ammonites described by Passendorfer (1928). The taxon Taramelliceras ex gr. compsum found 14 m above those ammonites is Late Kimmeridgian in age. Seven microfacies types (MF) are identified in the Upper Jurassic limestones of the Maty Giewont area. The Bositra-Saccocomidae MF occurs across the Lower-Upper Kimmeridgian boundary. The presence of planktonic and benthic foraminifers was documented in the Upper Jurassic deposits of the Raptawicka Turnia Limestone Formation. The genera Lenticulina Lamarck and Spiriffina Ehrenberg are common in the Kimmeridgian and Tithonian limestones. The palaeobathymetric evolution of the Kimmeridgian-Tithonian deposition recorded in the Maly Giewont sections reveals: a transgressive episode at the Early/Late Kimmeridgian boundary interval, a transgression peak in the Early Tithonian (Malmica Zone) and gradual shallowing of the High-Tatric swell in the Late Tithonian. Integrated isotope stratigraphy and biostratigraphy enabled correlation with the pelagic section of the Sub-Tatric Succession in the Dluga Valley section. The middle part of the Raptawicka Turnia Limestone Formation (Upper Kimmeridgian) may be correlated with the upper part of the Czajakowa Radiolarite Formation (red radiolarites) and Czorsztyn Limestone Formation in the Dfuga Valley (Western Tatra Mts.) section. The upper part of the Raptawicka Turnia Limestone Formation (Lower Tithonian) corresponds mostly to the Jasenina Formation. The overall similarity of the delta C-13 decreasing values recorded in the Kimmeridgian-earliest Tithonian interval of the Maly Giewont (this study) and Dluga Valley sections indicates that the generally shallow-water deposits of the Raptawicka Turnia Limestone Formation accumulated below the zone that was influenced by changes in the composition of marine water caused, for instance, by intense rainfall.