Comprehensive provenance study of the Triassic–Jurassic boundary interval in the Zliechov Basin (Western Carpathians, Slovakia)
摘要
To examine the sedimentary environment, source, and tectonic setting, the mineralogy and geochemistry of major, trace, and rare earth elements (REE) of carbonates of the Rhaetian Fatra Formation (Fatric Zone, Western Carpathians, Slovakia) were studied. The investigated pure and mainly impure limestones from the Kardolína section in the Tatra Mountains show signs of detrital input (∑REE = 73.46 ppm, Al2O3 = 1.33 wt.%, Zr = 36.8 ppm, Th = 2.8 ppm, and the occurrence of quartz, feldspars as well as clay minerals) and a diagenetic effect (low Sr, Na, and Ba contents in a few samples). The clastic admixture has been revealed by some immobile ratios (Th/Co and La/Sc) and is explicitly formed from silicic rocks. Hence, geochemistry has impeded the reconstruction of primary depositional environments. Nevertheless, sedimentation under a generally well-oxidized, shallow-water marine palaeoenvironment could be revived. Moreover, our work shows that the carbonate sedimentary environments changed with increased continental weathering (some of the samples studied have values of the chemical index of alteration higher than 90) to form specific iron-rich oolitic rocks, whereas this weathering is not related to the distance from the palaeoshoreline. These rocks may have been formed in an environment with the influx of oxygen-poor water (the likely source of which was the oxygen minimum zone) into the shallow-water setting. The findings of this work would benefit those working on the end-Triassic marine strata in various European basins.
Research highlightsThe studied limestones from the Kardolína section in the Tatra Mts (Western Carpathians, Slovakia) show signs of detrital input and a certain diagenetic influence. The siliciclastic sources are explicitly silicic rocks. Sedimentation under a shallow-water, generally well-oxygenated marine environment was reconstructed.