The Castelnuovo Garfagnana basin, which is investigated since 1800s for mining of lignite and quarrying of clay, is filled by Villafranchian continental deposits for long time interpreted as fluvio-lacustrine sequences (De Stefani 1889, D'Amato Avanzi & Puccinelli, 1988; Masini, 1936; Calistri, 1974; Puccinelli, 1987). A recent survey by Landi et al. (2002) provides a more detailed paleoenvironmental reconstruction, mapping four different lithostratigraphic Units. The lithostratigraphic Unit l is referred to a cohesive sediment anabranching river system developed in moist climatic conditions. This lithostratigrafic Unit, which represents the more ancient fluvial system recorded, mainly consists of spread fine clayey, silty and sandy deposits, characterized by accumulation in si tu of lignite (Overbank architectural elements ), and, subordinately, of conglomeratic deposits (Channel belt architectural elements). The lithostratigraphic Unit 2, 3 and 5 are chiefly composed of conglomeratic deposits (Channel belt architectural elements), respectively related to: (i) gravel bed-load alluvial system (lithostratigraphic Unit 2), (ii) debris flow dominated fan (lithostratigraphic Unit 3), and (iii) braided fluvial fan (lithostratigraphic Unit 5). The age of these deposits represents a matter of debate. Several previous studies suggested a generalized Villafranchian age (De Stefani, 1887, Zaccagna, 1932; Masini, 1933). Because of the occurrence of a diversified mammal assemblage (Anancus arvernensis, Lynx cf. issiodorensis, Sus cf. minor, Tapirus sp.) (De Stefani, 1887, 1889) in deposits related to the basal portion of lithostratigrafic Unit l of Landi et al. (2002), Azzaroli (1977) and Antiga (1988) proposed a Lower Villafranchian age (correlable with the Triversa Faunal Unit). In the middle portion of lithostratigraphic Unit l instead, the presence of charophyte gyrogonites, which belong to the species Nitellopsis cf. megarensis, and fresh-water molluscs (Theodoxus cf. groyanus, Prososthenia paulae and Prososthenia sp.) is indicative of a Middle Villafranchian age, corresponding to the Late Pliocene (Souliè-Marsche, 1979; Gliozzi et al., 1997; Esu & Girotti, 2001). The age of the successive lithostratigraphic Units is unclear. However, some ostracod val ves assigned to the species Cyprideis torosa have been collected in the basal portion of the lithostratigraphic Unit 2. According to Gliozzi et al. (1997), this species is commonly found in Pleistocene sediments with a stratigraphic range, which extends from Late Villafranchian to Aurelian. The different biostratigraphical setting of the lithostratigraphic Units l and 2 is consistent with the hypothesized presence of a disconformity between these two Units, as inferred by Landi et al. (2002).
PRELIMINARY BIOSTRATIGRAPHIC DATA FROM CASTELNUOVO GARFAGNANA BASIN (LUCCA, TUSCANY, ITALY).
SARTI, GIOVANNI
2003-01-01
Abstract
The Castelnuovo Garfagnana basin, which is investigated since 1800s for mining of lignite and quarrying of clay, is filled by Villafranchian continental deposits for long time interpreted as fluvio-lacustrine sequences (De Stefani 1889, D'Amato Avanzi & Puccinelli, 1988; Masini, 1936; Calistri, 1974; Puccinelli, 1987). A recent survey by Landi et al. (2002) provides a more detailed paleoenvironmental reconstruction, mapping four different lithostratigraphic Units. The lithostratigraphic Unit l is referred to a cohesive sediment anabranching river system developed in moist climatic conditions. This lithostratigrafic Unit, which represents the more ancient fluvial system recorded, mainly consists of spread fine clayey, silty and sandy deposits, characterized by accumulation in si tu of lignite (Overbank architectural elements ), and, subordinately, of conglomeratic deposits (Channel belt architectural elements). The lithostratigraphic Unit 2, 3 and 5 are chiefly composed of conglomeratic deposits (Channel belt architectural elements), respectively related to: (i) gravel bed-load alluvial system (lithostratigraphic Unit 2), (ii) debris flow dominated fan (lithostratigraphic Unit 3), and (iii) braided fluvial fan (lithostratigraphic Unit 5). The age of these deposits represents a matter of debate. Several previous studies suggested a generalized Villafranchian age (De Stefani, 1887, Zaccagna, 1932; Masini, 1933). Because of the occurrence of a diversified mammal assemblage (Anancus arvernensis, Lynx cf. issiodorensis, Sus cf. minor, Tapirus sp.) (De Stefani, 1887, 1889) in deposits related to the basal portion of lithostratigrafic Unit l of Landi et al. (2002), Azzaroli (1977) and Antiga (1988) proposed a Lower Villafranchian age (correlable with the Triversa Faunal Unit). In the middle portion of lithostratigraphic Unit l instead, the presence of charophyte gyrogonites, which belong to the species Nitellopsis cf. megarensis, and fresh-water molluscs (Theodoxus cf. groyanus, Prososthenia paulae and Prososthenia sp.) is indicative of a Middle Villafranchian age, corresponding to the Late Pliocene (Souliè-Marsche, 1979; Gliozzi et al., 1997; Esu & Girotti, 2001). The age of the successive lithostratigraphic Units is unclear. However, some ostracod val ves assigned to the species Cyprideis torosa have been collected in the basal portion of the lithostratigraphic Unit 2. According to Gliozzi et al. (1997), this species is commonly found in Pleistocene sediments with a stratigraphic range, which extends from Late Villafranchian to Aurelian. The different biostratigraphical setting of the lithostratigraphic Units l and 2 is consistent with the hypothesized presence of a disconformity between these two Units, as inferred by Landi et al. (2002).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
