Veronica Chiarini

Evaporite karst in Italy: a review

*jo.dewaele@unibo.it Citation:

Petrographical and geochemical changes in Bosnian stalagmites and their palaeo-environmental significance

Detailed petrographic observations have been coupled with trace element and δ13C - δ18O analyses in order to investigate their dynamics in two Holocene Bosnian speleothems. The potential of this multiproxy approach in providing a means to extract palaeo-environmental information from stalagmites whose stable isotope signals are noisy and without obvious trends has been tested. The studied stalagmites are mostly characterized by columnar microcrystalline fabric. At the sub-millimetre scale of lamination, different microcrystalline columnar sub-types (open and closed) have been detected and classified on the basis of the observed porosity and the crystallite size. The presence of variations in crystallite arrangement at the lamina scale suggests the occurrence of small-scale environmental changes recorded in the studied samples. A positive correlation was found found between Mg concentration, δ13C and fabric variations, while a negative correlation relates those parameters with Sr concentration. Both δ13C and fabric changes appear to be directly related to changes in hydrology. The detailed observation of calcite fabrics combined with stable isotope and trace element profiles allowed for the interpretation of the conditions under which the speleothems were deposited.

Late quaternary speleogenesis and landscape evolution in the northern Apennine evaporite areas: Development of underground and surface drainage in gypsum terrains

Gypsum beds host the majority of the caves in the north-eastern flank of the Apennines, in the Emilia Romagna region (Italy). More than six hundred of these caves have been surveyed, including the longest known epigenic gypsum cave systems in the world (Spipola-Acquafredda, ~11 km). Although this area has been intensively studied from a geological point of view, the age of the caves has never been investigated in detail. The rapid dissolution of gypsum and uplift history of the area have led to the long-held view that speleogenesis commenced only during the last 130 000 years. Epigenic caves only form when the surface drainage system efficiently conveys water into the underground. In the study area, this was achieved after the dismantling of most of the impervious sediments covering the gypsum and the development of protovalleys and sinkholes. The time necessary for these processes can by constrained by understanding when caves were first formed. The minimum age of karst voids can be indirectly estimated by dating the infilling sediments. U–Th dating of carbonate speleothems growing in gypsum caves has been applied to 20 samples from 14 different caves from the Spipola-Acquafredda, Monte Tondo-Re Tiberio, Stella-Rio Basino, Monte Mauro, and Castelnuovo systems. The results show that: (i) caves have been forming since at least ~600 kyr ago; (ii) the peak of speleogenesis was reached during relatively cold climate stages, when rivers formed terraces at the surface and aggradation caused paragenesis in the stable cave levels; (iii) ~200 000 years were necessary for the dismantling of most of the sediments covering the karstifiable gypsum and the development of a surface mature drainage network. Besides providing a significant contribution to the understanding of evaporite karst evolution in the Apennines, this study refines our knowledge on the timescale of geomorphological processes in a region affected by rapid uplifting. Copyright

Geomorphology of the Castel de' Britti area (Northern Apennines, Italy): an example of teaching geomorphological mapping in a traditional and practical way

Teaching how to map the geomorphology of an area cannot be performed in a satisfying manner only in the lecture room, but requires practical exercises both in the laboratory and in the field. A preliminary study of existing geological maps, geomorphological legends and symbols used in Italy and of the landslide inventory preceded a detailed four-day-long field mapping campaign carried out by students in the framework of their MSc course on ‘Geomorphological Mapping’ at Bologna University. The Geomorphological Map at 1:5000 produced by some of these students is presented in this paper. The study area is located in the northern Apennines, a few kilometres East of Bologna, along the Idice Valley (N-Italy). Lithologies are mainly composed of clayey and marly sequences ranging in age from Cretaceous to Plio-Pleistocene, sands and sandstones of Pleistocene age, and Messinian gypsum, these last being the most resistant rocks. Besides the greater scale used in this map, allowing for a more detailed representation of the mapped features, this map also shows the recent evolution of landslides in this actively mass wasting area.