Surface and subsurface drainage evolution of the Corfino and Soraggio karst areas (Tuscany, Italy)

Abstract

IzvlečekUDK 551.435.8(450.52) Giampaolo Mariannelli & Leonardo Piccini: Razvoj površin-ske in podzemne odtočne mreže na kraških območjih Corfino in Sorragio Pania di Corfino in Ripa di Soraggio sta dva manjša kraška območja v Toskani. Površine območij znašajo 11 km 2 , vendar je na nji� znani� preko 100 jam. Obstoj stari� epifreatični� galerij priča o nezveznem zniževanju nivoja erozijske baze dolin rek Serc�io di Soraggion in Fiume, ki sekata karbonatno območje na SZ oziroma JV meji masiva. Glavne jame so razporejene v višinskem obsegu 500 m. Povezava leg jam in položaja aluvialni� sedimentov, nam je omogočila sklepanje o razvoju območja v poznem kvartarju. če predpostavimo odlaganje fluvialnega gradiva v mrzli� obdobji� in vrezovanje rečni� dolin v topli� obdobji�, la�ko sklepamo, da so nezvezno razporejeni epifreatični rovi nastali ob pre�odi� iz enega v drugo obdobje. Poleg tega je na razvoj jamski� sistemov vplivala tudi preureditev rečne mreže ob tektonskem dvigu. Strukturnomorfološki pogoji so narekovali razvoj podzemnega odtoka skozi masiv, preko katerega so površinski vodotoki z ene strani masiva napajali vodotoke na drugi strani, ki so se posledično �itreje urezovali. Ves proces je napredoval gorvodno in ustvaril niz stari� ponorov, izvirov in pripadajoči� fosilni� jamski� galerij. Ključne besede: kras, speleogeneza, reliktne jame, Pania di Corfino, severni Apenini. The Pania di Corfino and Ripa di Soraggio are two minor karst areas in Tuscany, �aving a surface of only 11 km 2 , but contain more t�an 100 known caves. Some caves are old epi-p�reatic passages testifying to a discontinuous lowering of base level in t�e two major valleys t�at cross t�e carbonate outcrops: t�e Serc�io di Soraggio and t�e Fiume rivers, respectively located along t�e Nw and SE borders of t�e massif. The spatial-altimetric distribution of major caves, w�ic� are found on a vertical range of a few �undreds of meters, and t�eir relations�ips wit� t�e position of surface alluvial deposits �ave allowed to infer a first evolutionary framework of karst during t�e late quaternary. If we refer to a simple model, w�ere fluvial deposition occurs mainly during cold stages and incision during warm stages, t�e discrete distribution of cave passages suggests t�at t�e different epi-p�reatic p�ases are t�e responses to t�e alternation of cold and warm periods. In any case, t�e re-organization of t�e river network induced by t�e tectonic uplift �ad a relevant effect on cave systems. First, t�e underground diversion of surface drainage en�anced t�e downcutting of Nw and SE perip�eral streams, w�ic� received a larger quantity of water t�roug� karst springs due to t�e favored morp�o-structural setting. Successively, t�e backward piracy of t�e allogenic catc�ments of t�e karst systems by surface tributaries led to t�e dewatering of caves and to t�e present situation.

Sulphuric acid speleogenesis and landscape evolution: Montecchio cave, Albegna river valley (Southern Tuscany, Italy)

“…As a result, ancient phreatic and epiphreatic passages are often concentrated in some precise elevation ranges formed during a prolonged stability of the water table position inside a karst system (Palmer, 1987). In this sense a cave system can be regarded as a sort of precise proxy of incision rates (Marianelli and Piccini, 2011). The main problem is that the origin of caves cannot be dated with certainty, because the phreatic stage commonly does not produce datable sediments.…”