New dating of palaeokarst features at Torricelle hills (Verona, Italy)

Abstract

At the southern edge of the Lessini Mountains (Venetian Prealps,Italy), a well-developed palaeokarst network is found in the hills surroundingVerona, called Torricelle. Palaeokarst cavities are fossilizedby palaeosols of mostly limonitic composition ('yellow ochres'),which were mined for centuries for pigments. In the current interpretation,the age of the palaeokarst features is set between theOligocene and the early Miocene, when a regression took place in thecentral Lessini Mountains which partially emerged. In the Torricellearea, ochres are believed to be the insoluble residuals of subaerialweathering of upper-Priabonian marly limestones.The exploration of paleokarst cavities and of the surroundingarea has led to the discovery of terrigenous-calcarenitic layers embed -ded in the palaeosol fillings, containing foraminifera assemblageswhose age ranges from the upper Eocene to the upper OligocenelowerMiocene. In particular, one of the caves is developed in theMarne di Priabona Formation (lower Priabonian), and its ochre fillingcontains fossiliferous layers with Priabonian Foraminifera assemblages.The presence of fossils whose age is comparable to that ofthe host rock is a testimony of upper-Eocene eogenetic karst. Furthermore,the presence of ochre fragments embedded in nearbyYpresian and Bartonian limestones provides evidence of emergedland and pedogenesis in early and middle Eocene, partly disprovingthe current interpretation of ochres' formation.These findings provide evidence that ochre formation, karstdevelopment and its fossilisation started earlier than Miocene, aspreviously thought. Phenomena began in early Eocene and ended inMiocene, over a time span of at least 30 million years.