Storm-dominated deposition of the Lower Jurassic crinoidal limestones in the Kr�?na unit, Western Tatra Mountains, Poland

Abstract

The Lower-Middle Jurassic of the Krína unit in the Western Tatra Mts. (southern Poland) shows considerable facies variation. Crinoidal grainstones of variable thickness (up to 12 m) are one of characteristic facies. They occur above spiculites which were deposited below storm wave base on the slopes of elevated horsts. First single beds of crinoidal limestones occur within spiculites. They were deposited as event beds, generated probably by storms. The overlying thick complex of wellsorted grainstones composed almost entirely of crinoidal ossicles display widespread erosional bed amalgamation, hummocks and locally wave-formed ripples. The above characteristics are the effects of multiple reworking and winnowing of fine crinoidal material by oscillatory currents related to storms. This proves that the sedimentation of the crinoidal grainstones took place between the storm and the fair-weather wave bases. The vertical transition from spiculites with intercalations of crinoidal limestone beds towards the crinoidal grainstones is interpreted as the result of a shallowing upward trend. Since this trend is opposite to the global Early Toarcian transgression, this could be related to an uplift due to local block tectonic activity. The evidence for that is diversification of facies in the Krína Basin, as well as submarine slumps recorded in spiculites. The location of Krína Basin on relatively low northern latitude and on western edges of great Tethys Ocean during Early Jurassic enabled the formation of the crinoidal tempestites.

Trace fossils from the Lower Muschelkalk of Raciborowice Górne (North Sudetic Synclinorium, SW Poland) and their palaeoenvironmental interpretation

“…In siliciclastic deposits, Thalassinoides is indicative of lower shoreface-offshore settings (Pemberton et al 2001;Uchman and Krenmayr 2004;Buatois and Mángano 2011;Chrząstek 2013;La Croix et al 2013). It is also reported from the inner-middle carbonate ramp (Knaust 1998;, and mostly from shallow carbonate deposits (Monaco and Giannetti 2002;Jach 2005;Waite et al 2008Waite et al , 2013Vlahovic et al 2011;Wiedl et al 2012Wiedl et al , 2013. Thalassinoides was described from the upper part of the shallowing upward cycle (Knaust 1998;Pérez-Valera and Pérez-López 2008;Pérez-López and Pérez-Valera 2012).…”

Trace-fossil assemblages with a new ichnogenus in “spotted”

“…These spicules either represent relicts of poorly-developed sponge communities or they were transported from sponge communities in the northern parts of the Zliechov Basin where spiculite-rich packstones are more widespread and recurrent than at the Skladaná Skala section. Such packstones, locally with in situ sponges (Jach 2002), signify the presence of sponge-dominated meadows on the foot and slopes of topographic elevations (Jach 2002(Jach , 2005) that were rimming the depocenters with spotted deposits. Therefore, the deposition of Pliensbachian bioturbated deposits at Skladaná Skala partly coincides with the deposition of spiculites in shallower, more proximal, northern parts of the Zliechov Basin, now preserved in the northern parts of the Malá Fatra and High Tatra Mountains.…”

“…The Central Western Carpathians were located on the northern passive margin of the Tethys during the Early Jurassic, approximately at 25-30° N in the tropical climatic belt (Thierry 2000;Jach 2005) (Fig. 1).…”

“…However, the actual stratigraphic range of this formation is frequently smaller owing to complex horizontal and stratigraphic relations with other formations. It can be horizontally replaced by crinoidal limestones, spiculitic limestones, or nodular limestones of the Adnet Formation (Mišík & Rakús 1964;Jach 2002Jach , 2005. In the upper part, it can be replaced by spiculitic limestones (Świńska Turnia Member of the Huciska Formation, Western Tatra Mountains), nodular limestones (Adnet Formation, Ve ká Fatra Mountains), crinoidal limestones (Lefeld et al 1985), or by radiolarian limestones of the Sokolica or Ždiar Formations (Lefeld et al 1985;Polák & Ondrejičková 1993;Polák et al 1998).…”

“…Second, spotted deposits in the northern parts of the Ve ká Fatra Mountains are horizontally and stratigraphically replaced by nodular limestones of the Adnet Formation in the southward direction (Mišík & Rakús 1964). Third, frequent spiculitic and crinoidal beds imply proximity of slope, and thus more northward limit of the depocenter of the Zliechov Basin, in the eastern part of the High Tatra Mountains (Lefeld et al 1985;Jach 2005). Therefore, the thickness reduction by two orders of magnitude and the spatial replacement of deep-water "spotted" facies by sponge meadows, by shallower sediments exposed to stronger current action (crinoidal facies), and by highly condensed and bioturbated sediments (nodular facies) imply topographic differentiation of the Zliechov Basin into plateaus and semi-enclosed, sediment-catching and high-subsidence depocenters.…”