Lo studio effettuato per la redazione della presente Carta Geologica in scala 1:50 000 ha previsto sia un rilevamento geologico in scala 1:10 000 che un'attenta analisi geomorfologica condotta sul campo, su foto aeree e su carte topografiche in scala 1:5 000 degli anni '80 (Carta Tecnica dell'Italia Meridionale; Cassa per il Mezzogiorno). Ciò è stato integrato dal riesame di circa trecento stratigrafie di sondaggio pre-esistenti (ad uso geotecnico e idrogeologico) e dallo studio di 11 carotaggi continui effettuati ad hoc; studio che ha previsto osservazioni sedimentologiche ed analisi micropaleontologiche e palinologiche volte a definire paleoambienti di sedimentazione e condizioni paleoclimatiche. Lo studio ha consentito di meglio definire l'estensione di unità già note, di riconoscere nuove unità stratigrafiche e di operare suddivisioni all'interno degli ampi accorpamenti formazionali presenti sui citati Fogli 1:100 000 della Carta Geologica d'Italia. Avendo meglio chiarito i rapporti geometrici e cronologici tra i vari terreni presenti ed aderendo alle normative del progetto CARG, le unità completamente formate e non ubiquitarie sono state organizzate secondo i criteri delle UBSU. Esse appartengono tutte all'ampio Bacino della Piana Sele-Golfo di Salerno; denominazione con la quale s'intende sia la omonima depressione peri-tirrenica (vedi capitolo II), sia i bacini fluviali che verso di essa convergono dai retrostanti rilievi appenninici. Nella depressione tettonica, le fasi di subsidenza hanno permesso l'accumulo di successioni quaternarie, spesse da centinaia a migliaia di metri, che sulla Piana alternano intervalli alluvionali, transizionali e litorali, mentre nel Golfo sono dominate da depositi marini.
The present sheet of the 1:50,000 Carta Geologica d'Italia falls entirely in the so called Piana del Sele (i.e. Sele River Plain). This alluvial-coastal plain lyes on Quaternary sediments that were accumulated inside a coastal half-graben, which continues in the off-shore with the deep Salerno Gulf. As shown in Fig. 1, this tectonic depression cuts the -orogenically speaking- inner side of the Southern Apennine chain, being interpreted as an effect of the opening and eastward migration of the Tyrrhenian Sea back-arc basin. The present day bathimetry of the Salerno Gulf is shown in Fig. 2, while Fig. 3 shows the thickness of the basin fill by isopachs in milliseconds t.w.t.. The main tectonic features of the basin are described in Fig. 5 and 6, according to Sacchi et alii (1994) for the off-shore and according to the present authors for the faults running either near coast or on land. The logs of Mina 1 and Sele 1 wells (Fig. 5 and 6) account for the deep stratigraphy of the basin fill, but there are still doubts about the age of its lowest terms and, consequently, the beginning of collapse. However, most authors agree that the present day morphostructural setting is due to Quaternary extensional tectonics, controlled by a NW-SE oriented ?3. On land, the first phases of the collapse (and generation of strong relief) is evidenced by the deposition of the so called Conglomerati di Eboli (i.e., the Eboli Supersynthem; CE). This thick and widespread clastic unit of the Lower Pleistocene is deeply buried in this Sheet (Fig 7) but it is largely exposed in the Sheets 467 and 468. It is mostly composed of fan-glomerates whose clasts came from the dissection of the Mt. Picentini massif, where a thick succession of tectonized 134 Mesozoic limestones and dolostones crops out. Around the beginning of Middle Pleistocene, the geomorphology of the Plain was re-shaped by normal and transtensional (transfer) faults (Fig. 8). Part of the area carrying the Lower Pleistocene fanglomerates was uplifted, while another large part of the Plain continued to subside and started accomodating the Battipaglia-Persano supersynthem (BP). This unit, which is up to some hundreds meters thick, covers large part of the present Sheet and associates with a wide depositional terrace that rests at 16-18 m a.s.l. closer to the modern coast and rises up to 100 m a.s.l. and more near the mountain front (where alluvial fans increase locally its elevation; Fig. 9). Even though never sampled and studied in detail, the lower part of the BP supersynthem is lithostratigraphically described in the logs of numerous drillings for water research. There it appears composed of decametrica alternations of coarse grained intervals of probable fluvial origin, intervals dominated by grey to blue clays (sometimes with peat and fossils) of probable lagoonal origin and intervals of matrix free sands of probable beach and coastal dune environments. Thickness and facies of the supersynthem's lower part prove that its deposition was accompanied by subsidence and, maybe, NW-ward tilting (see Fig. 8). The younger part of the supersynthem BP was investigated in detail with a number of new drillings (see Appendice 1), palaeo-ecological analyses and correlations with the logs of many pre-existing perforations. As shown in Fig. 14, it is composed of coarse and fine grained alluvial deposits close to the hills of Battipaglia (area of the ancient fan of the Tusciano River; see Fig. 9), while the coeval, more distal part of it is composed of a number of coastal parasequences that give evidence of several regressions and trasgressions. Based on pollen data and relations with the Gromola Synthem (see below), those fluctuations are tentatively framed between the OIS 9 and 5.5. As proved by the elevation of beach and lagoonal facies of abovementioned parasequences, during the second half of Middle Pleistocene, the Plain was subject to some uplift (up to about 30 m; see also Fig. 12). Both stratigraphical data and geomorphological evidence prove that it was also affected by moderate faulting (see the Sheet). The mentioned faults had stopped moving when the trasgression witnessed by the Gromola synthem (GML) occurred (Last Interglacial; Tyrrhenian Marine Stage). As Fig. 15 and 16 show, this glacial-eustatic transgression advanced first with transitional (lagoonal to palustrine) deposits and then with sandy beaches. The back-barrier domains were eventually filled up with marshy and fluvio-palustrine sediments when the sea rise stopped and, aeolian sands were finally accumulated on the coastal ridge. Some isoleucine datings and some stratigraphical evidence suggest that the Gromola ridge incorporates two peacks of the OIS 5 (5.3 and 5.1). Remnants of the back-barrier terrace of these Tyrrhenian high stands is preserved in the modern landscape (Fig. 9) at 11-14 m a.s.l., while the coeval shoreface sediments occur up to 13 m a.s.l. and the dunes up to 23 m a.s.l. 135 Near Paestum, the Gromola transgressions were limited by the pre-existing, prominent lobes of the travertini di Seliano (TSN), which are calcareous tufa belonging to the upper part of the BP supersynthem. The Sele Plain was subject to fluvial dissection during the Last Glacial regression. During this period (probably in the late part of it) the deposition of the alluvial synthem MQS took place along the lower Tusciano River. The load carried by the Sele River probably fed the deposition of less inclined valleyfloor beds, nowadays to be found under the similar Holocene deposits. After the marine regression of OIS 4 and largely before the Holocene high stand, the southernmost part of the Sheet area received the deposition of new calcareous tufa (travertini di Paestum; TPP). To the late part of the Post Glacial trasgression and to the following period of high stand is finally due the deposition of the Campolongo Syntem (SLG), whose internal composition and relations with the present day morphology of the lower Sele Plain are shown in Fig. 21. The Early Holocene part of it shows a clear transgressive trend, while the Late Holocene part has a progradational trend. As shown in Fig. 22, also this last transgression was pre-announced by lagoonal deposits, whose basal part has been radiometrically dated (14C) around 9,000 yrs B.P. The peak of ingression occurred around 5,300 yrs B.P. and it formed the innermost part of the composite Cordone di Laura coastal ridge (up to 1.5 km from the present coastline). The beach deposits forming the most internal part of the composite Cordone di Sterpina coastal ridge (generally at some 250 m from the modern coast) have ages ranging from the 6th century B. C. to about 2.000 years ago.
Note Illustrative alla Carta Geologica d'Italia alla scala 1:50000, foglio 486 Foce del Sele
Budillon F;D'Argenio B;Ferraro L;Insinga D;
2009
Abstract
The present sheet of the 1:50,000 Carta Geologica d'Italia falls entirely in the so called Piana del Sele (i.e. Sele River Plain). This alluvial-coastal plain lyes on Quaternary sediments that were accumulated inside a coastal half-graben, which continues in the off-shore with the deep Salerno Gulf. As shown in Fig. 1, this tectonic depression cuts the -orogenically speaking- inner side of the Southern Apennine chain, being interpreted as an effect of the opening and eastward migration of the Tyrrhenian Sea back-arc basin. The present day bathimetry of the Salerno Gulf is shown in Fig. 2, while Fig. 3 shows the thickness of the basin fill by isopachs in milliseconds t.w.t.. The main tectonic features of the basin are described in Fig. 5 and 6, according to Sacchi et alii (1994) for the off-shore and according to the present authors for the faults running either near coast or on land. The logs of Mina 1 and Sele 1 wells (Fig. 5 and 6) account for the deep stratigraphy of the basin fill, but there are still doubts about the age of its lowest terms and, consequently, the beginning of collapse. However, most authors agree that the present day morphostructural setting is due to Quaternary extensional tectonics, controlled by a NW-SE oriented ?3. On land, the first phases of the collapse (and generation of strong relief) is evidenced by the deposition of the so called Conglomerati di Eboli (i.e., the Eboli Supersynthem; CE). This thick and widespread clastic unit of the Lower Pleistocene is deeply buried in this Sheet (Fig 7) but it is largely exposed in the Sheets 467 and 468. It is mostly composed of fan-glomerates whose clasts came from the dissection of the Mt. Picentini massif, where a thick succession of tectonized 134 Mesozoic limestones and dolostones crops out. Around the beginning of Middle Pleistocene, the geomorphology of the Plain was re-shaped by normal and transtensional (transfer) faults (Fig. 8). Part of the area carrying the Lower Pleistocene fanglomerates was uplifted, while another large part of the Plain continued to subside and started accomodating the Battipaglia-Persano supersynthem (BP). This unit, which is up to some hundreds meters thick, covers large part of the present Sheet and associates with a wide depositional terrace that rests at 16-18 m a.s.l. closer to the modern coast and rises up to 100 m a.s.l. and more near the mountain front (where alluvial fans increase locally its elevation; Fig. 9). Even though never sampled and studied in detail, the lower part of the BP supersynthem is lithostratigraphically described in the logs of numerous drillings for water research. There it appears composed of decametrica alternations of coarse grained intervals of probable fluvial origin, intervals dominated by grey to blue clays (sometimes with peat and fossils) of probable lagoonal origin and intervals of matrix free sands of probable beach and coastal dune environments. Thickness and facies of the supersynthem's lower part prove that its deposition was accompanied by subsidence and, maybe, NW-ward tilting (see Fig. 8). The younger part of the supersynthem BP was investigated in detail with a number of new drillings (see Appendice 1), palaeo-ecological analyses and correlations with the logs of many pre-existing perforations. As shown in Fig. 14, it is composed of coarse and fine grained alluvial deposits close to the hills of Battipaglia (area of the ancient fan of the Tusciano River; see Fig. 9), while the coeval, more distal part of it is composed of a number of coastal parasequences that give evidence of several regressions and trasgressions. Based on pollen data and relations with the Gromola Synthem (see below), those fluctuations are tentatively framed between the OIS 9 and 5.5. As proved by the elevation of beach and lagoonal facies of abovementioned parasequences, during the second half of Middle Pleistocene, the Plain was subject to some uplift (up to about 30 m; see also Fig. 12). Both stratigraphical data and geomorphological evidence prove that it was also affected by moderate faulting (see the Sheet). The mentioned faults had stopped moving when the trasgression witnessed by the Gromola synthem (GML) occurred (Last Interglacial; Tyrrhenian Marine Stage). As Fig. 15 and 16 show, this glacial-eustatic transgression advanced first with transitional (lagoonal to palustrine) deposits and then with sandy beaches. The back-barrier domains were eventually filled up with marshy and fluvio-palustrine sediments when the sea rise stopped and, aeolian sands were finally accumulated on the coastal ridge. Some isoleucine datings and some stratigraphical evidence suggest that the Gromola ridge incorporates two peacks of the OIS 5 (5.3 and 5.1). Remnants of the back-barrier terrace of these Tyrrhenian high stands is preserved in the modern landscape (Fig. 9) at 11-14 m a.s.l., while the coeval shoreface sediments occur up to 13 m a.s.l. and the dunes up to 23 m a.s.l. 135 Near Paestum, the Gromola transgressions were limited by the pre-existing, prominent lobes of the travertini di Seliano (TSN), which are calcareous tufa belonging to the upper part of the BP supersynthem. The Sele Plain was subject to fluvial dissection during the Last Glacial regression. During this period (probably in the late part of it) the deposition of the alluvial synthem MQS took place along the lower Tusciano River. The load carried by the Sele River probably fed the deposition of less inclined valleyfloor beds, nowadays to be found under the similar Holocene deposits. After the marine regression of OIS 4 and largely before the Holocene high stand, the southernmost part of the Sheet area received the deposition of new calcareous tufa (travertini di Paestum; TPP). To the late part of the Post Glacial trasgression and to the following period of high stand is finally due the deposition of the Campolongo Syntem (SLG), whose internal composition and relations with the present day morphology of the lower Sele Plain are shown in Fig. 21. The Early Holocene part of it shows a clear transgressive trend, while the Late Holocene part has a progradational trend. As shown in Fig. 22, also this last transgression was pre-announced by lagoonal deposits, whose basal part has been radiometrically dated (14C) around 9,000 yrs B.P. The peak of ingression occurred around 5,300 yrs B.P. and it formed the innermost part of the composite Cordone di Laura coastal ridge (up to 1.5 km from the present coastline). The beach deposits forming the most internal part of the composite Cordone di Sterpina coastal ridge (generally at some 250 m from the modern coast) have ages ranging from the 6th century B. C. to about 2.000 years ago.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
