On the Upper Pleistocene, almost at the beginning of Holocene, a giant deep seated gravitational collaps, involving an area of about 1000 km2 and a volume of about 40 Mm3, triggered by the Sila “crickogeno” tec-tonic function, has involved the north-western side of the Sila Massif, dammed the Crati river near the present “Stretta di Tarsia”, producing a lake, here named Crati Lake, whose extension reached the town of Cosenza. This huge phenomena has been favored, very probably, by the large spreading towards NW of the northern part of Calabria in consequence of Pollino right transcurrent fault, which has displaced towards the Tyrrhenian sea the “la Mula, Montea, etc. chain”. This movement could have exerted an attraction, just towards NW (a sort of “chain suck”), affecting up to Sila side.This huge, large gravitational phenomena, on the basis of the morphological shape and features, has been in-terpreted as post tectonic phenomena to be included in the wide range of gravitative phenomena. Owing to its very large dimensions, which exceed by far the usually sizes for such deformations, we propose to name it as deep seated gravitational “territorial” deformations (DSGTD). The phenomena was favored by structural conditions of that region, in which the unit of phyllades (Bagni Unit), tectonically underlain to gneiss, biotite schists and granites of Polia Copanello Unit, have had the fun-ction of weak, “plastic” body respect to the more rigid superposed rocks. The giant deformation has involved, in the foot zone, also the whole hilly territory, where the hydrographic net appears strongly deformed and the terrains of Plio-Pleistocene age raised by means of the “lever effect” of the deep and hidden gravitative thrusts in the foot zone itself. It caused kilometric deviations of the water courses, “snatchs”, narrowing of the val-ley sections, changes of the attitude of strata, tilting, planimetric rotations, river captures, etc. During the displacement the DSGTD body has undergone also an initial clockwise rotation, which has brought about a change of the orientation of the numerous river valleys which cross it. The northern foot zone of the deforma-tion has moved forward to north in confront of the re-maining part of the base of the Sila slope towards Ros-sano town. The remarkable geomorphological effects on the territory give evidence of the recent age of the giant gravitative phenomena, not yet masked or can-celled by erosive Holocene processes. Finally, this work must have an undoubted significance for seismological aspects of that territory.
Nel Pleistocene superiore-inizio dell’Olocene, per il sol-levamento tettonico della Sila (“crickogeno”), sul suo versante nord occidentale si è attivato un grande movi-mento gravitativo, che ha coinvolto un’area di oltre 1000 km2 ed un volume di circa 40 Mm3. Detto movimento ha sbarrato il fiume Crati all’altezza dell’attuale “Stret-ta di Tarsia”, originando un grande lago che si estese fino a Cosenza. Le masse in gioco comprendono unità di rocce intrusive e metamorfiche di alto e basso grado, ascrivibili alle Unità Alpine, depositi marini post oro-geni del Pleistocene-Calabriano-Pliocene ed i depositi alluvionali clastici, terrazzati e non dell’Olocene. Alla sua attivazione ha probabilmente contribuito l’allarga-mento della piana di Sibari conseguente al movimento della faglia trascorrente destra del Pollino, che avreb-be esercitato un’azione di richiamo appunto verso NW (una sorta di “risucchio”), risentitosi fin nel versante silano.Si tratta di un fenomeno che per le sue dimensioni può essere definito una Deformazione Gravitativa Territo-riale Profonda (DGTP) e che a grande scala ha forme morfologiche analoghe a quelle delle mega-frane ro-tazionali multiple: con abbassamenti e basculamenti, “rigonfiamenti”, rotture multiple, innalzamenti al piede. Il fenomeno di macro-scala ha generato i presupposti per la franosità p.d. passata e futura di tutto quell’ampio settore territoriale silano, avendo agito a livello delle “strutture” delle rocce ivi affioranti, nonché del loro grado di alterazione chimico-fisica. Rilevante è stato lo spostamento delle aste fluviali del Fiume Crati e di altri corsi d’acqua verso nord, come pure l’effetto di sollevamento nelle zone di piede da parte delle rotture gravitative sepolte nelle unità Plio-Pleistoceniche, evi-denziando un’epoca alquanto recente del gigantesco fenomeno gravitativo, che i fenomeni di erosione oloce-nici non hanno ancora mascherato o cancellato. Infine il tema del presente lavoro ha un indubbio significato per gli aspetti sismici del territorio in oggetto.
La grande deformazione territoriale profonda della Sila Nord-occidentale, con sbarramento del fiume Crati, spostamenti ed “effetti leva” nei terreni della Piana di Sibari, condizionata anche dalla tettonica trascorrente del Pollino
Vincenzo Simeone
2016-01-01
Abstract
On the Upper Pleistocene, almost at the beginning of Holocene, a giant deep seated gravitational collaps, involving an area of about 1000 km2 and a volume of about 40 Mm3, triggered by the Sila “crickogeno” tec-tonic function, has involved the north-western side of the Sila Massif, dammed the Crati river near the present “Stretta di Tarsia”, producing a lake, here named Crati Lake, whose extension reached the town of Cosenza. This huge phenomena has been favored, very probably, by the large spreading towards NW of the northern part of Calabria in consequence of Pollino right transcurrent fault, which has displaced towards the Tyrrhenian sea the “la Mula, Montea, etc. chain”. This movement could have exerted an attraction, just towards NW (a sort of “chain suck”), affecting up to Sila side.This huge, large gravitational phenomena, on the basis of the morphological shape and features, has been in-terpreted as post tectonic phenomena to be included in the wide range of gravitative phenomena. Owing to its very large dimensions, which exceed by far the usually sizes for such deformations, we propose to name it as deep seated gravitational “territorial” deformations (DSGTD). The phenomena was favored by structural conditions of that region, in which the unit of phyllades (Bagni Unit), tectonically underlain to gneiss, biotite schists and granites of Polia Copanello Unit, have had the fun-ction of weak, “plastic” body respect to the more rigid superposed rocks. The giant deformation has involved, in the foot zone, also the whole hilly territory, where the hydrographic net appears strongly deformed and the terrains of Plio-Pleistocene age raised by means of the “lever effect” of the deep and hidden gravitative thrusts in the foot zone itself. It caused kilometric deviations of the water courses, “snatchs”, narrowing of the val-ley sections, changes of the attitude of strata, tilting, planimetric rotations, river captures, etc. During the displacement the DSGTD body has undergone also an initial clockwise rotation, which has brought about a change of the orientation of the numerous river valleys which cross it. The northern foot zone of the deforma-tion has moved forward to north in confront of the re-maining part of the base of the Sila slope towards Ros-sano town. The remarkable geomorphological effects on the territory give evidence of the recent age of the giant gravitative phenomena, not yet masked or can-celled by erosive Holocene processes. Finally, this work must have an undoubted significance for seismological aspects of that territory.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
