Geomorphological analysis of dolines in a low-topography karst, and considerations about their hydraulic functioning

Starting from previous experiences in karst settings of southern Italy, and following the same procedure for the identification of dolines and endorheic basins (Zumpano et al., 2019; Pisano et al., 2020), we focus here our attention on several dolines characterizing the landscape of the Salento peninsula, in the southernmost part of Apulia. This region shows a typical low-topography karst, with elevations reaching maximum values of about 120 m a.s.l.. Thus, very often the main karst landforms, such as dolines and endorheic basins, are not clear to identify and present subdue connections with the adjoining land. Only at those sites where the doline was produced by collapse of the carbonate bedrock, or of the overburden above it, and where an active swallow hole is present, recognition appear more direct and straightforward.

Nevertheless, it is exactly this difficulty in identification of the karst landforms which makes particularly intriguing the research in the central sector of Salento. Further, in this area one of the two Apulian caves where speleologists are able to directly reach the water table, at depth of -60 m below the ground surface, is located: Vora Bosco opens within a narrow, W-E oriented, fissure in the topographic surface, and develops through the overall stratigraphic succession of Salento, from Quaternary deposits, to Plio-Pleistocene and Miocene calcarenites, down to the Cretaceous limestones, with these latter hosting the water table.

In a 240km²-wide area around Vora Bosco, a systematic survey was carried out aimed at identifying all dolines. The work started from analysis of historical sources, integrated by periodic field surveys, and by detailed analysis of multi-temporal sets of aerial photographs. Several tens of dolines and endorheic basins of variable size were mapped, and distinguished on the basis of the mechanism at the origin of their formation, according to the most widespread international classification (Gutierrez et al., 2014).

In addition to the genetic and morphometric characterization of the identified dolines and endorheic basins, these were also discriminated as concerns the role they play for hydraulic functioning: based upon the local situation, with particular regard to presence and thickness of residual deposits, and to the discontinuity networks in the rock mass, these sites may act as absorption point to recharge the karst aquifer, or as impervious areas which retard the downward infiltration of water.

 

References

Gutierrez F., Parise M., De Waele J. & Jourde H., 2014, A review on natural and human-induced geohazards and impacts in karst. Earth Science Reviews, vol. 138, p. 61-88.

Parise M., 2019, Sinkholes. In: White W.B., Culver D.C. & Pipan T. (Eds.), Encyclopedia of Caves. Academic Press, Elsevier, 3^rd edition, ISBN 978-0-12-814124-3, p. 934-942.

Pisano L., Zumpano V., Liso I.S. & Parise M., 2020, Geomorphological and structural characterization of the “Canale di Pirro” polje, Apulia (Southern Italy). Journal of Maps, vol. 16 (2), p. 479-487.

Zumpano V., Pisano L. & Parise M., 2019, An integrated framework to identify and analyze karst sinkholes. Geomorphology, vol. 332, p. 213-225.