Late Messinian Lago-Mare deposits show high-frequency cyclicity in the whole Mediterranean Basin. Both millimeter- and centimeter-scale cyclicities have been observed in several ODP sites as well as in stratigraphic sections from the Mediterranean borderland. We have analyzed a well-exposed late Messinian Lago-Mare section from the Adriatic side of the central Apennines (Italy). At the Fonte dei Pulcini section (SE Majella Mts.), millimeter- and centimeter-scale white-and-dark couplets have been observed in the field. A 50 cm regular-spaced sampling has been performed in the uppermost 53 m of the late Messinian Lago- Mare clays. On the 107 collected samples, geochemical (CaCO3 content), mineralogical (XRD analyses), and micropalaeontological investigations have been performed. In addition, SEM and microprobe investigations as well as mineralogical and micropalaeontological analyses have been carried out on single lamina from a 34-cm-thick interval of millimeter-scale laminites. Besides the 103 cycles/m and 102 cycles/m frequencies observed in the field, spectral analyses performed on the CaCO3 data set indicated other high-frequency cyclicities: 0.47 cycles/m, 0.35 cycles/m, and 0.17 cycles/m. Taking into account the estimated sedimentation rate, these frequencies correspond, respectively, to periodicities of: 1 year, 10 years, 2.1 kyr, 2.8 kyr, and 5.6 kyr. These sub-Milankovitch cyclicities have been related to annual and sunspot solar activity. The millimeter-scale couplets are interpreted as varves sedimented in an ephemeral water environment marginal to a perennial brackish water lagoonal basin. These varved sediments reflect a marked seasonality characterized by the alternation of arid and more humid climatic phases. The presence of high values of smectite (60–80%) in the clay minerals of the analyzed samples could be a consequence of these climatic oscillations from drier to moister conditions. The climatic scenario suggested in this paper for the late Messinian Lago-Mare episode is in agreement with the monsoon system that, according to some authors, starting from 5.8 Ma developed in the Mediterranean area.
Cosentino, D., Cipollari, P., LO MASTRO, S., Giampaolo, C. (2005). High-frequency cyclicity in the latest Messinian Adriatic foreland basin: Iinsight into palaeoclimate and palaeoenvironments of the Mediterranean Lago-Mare episode. SEDIMENTARY GEOLOGY, 178, 31-53.
High-frequency cyclicity in the latest Messinian Adriatic foreland basin: Iinsight into palaeoclimate and palaeoenvironments of the Mediterranean Lago-Mare episode
COSENTINO, Domenico;CIPOLLARI, PAOLA;
2005-01-01
Abstract
Late Messinian Lago-Mare deposits show high-frequency cyclicity in the whole Mediterranean Basin. Both millimeter- and centimeter-scale cyclicities have been observed in several ODP sites as well as in stratigraphic sections from the Mediterranean borderland. We have analyzed a well-exposed late Messinian Lago-Mare section from the Adriatic side of the central Apennines (Italy). At the Fonte dei Pulcini section (SE Majella Mts.), millimeter- and centimeter-scale white-and-dark couplets have been observed in the field. A 50 cm regular-spaced sampling has been performed in the uppermost 53 m of the late Messinian Lago- Mare clays. On the 107 collected samples, geochemical (CaCO3 content), mineralogical (XRD analyses), and micropalaeontological investigations have been performed. In addition, SEM and microprobe investigations as well as mineralogical and micropalaeontological analyses have been carried out on single lamina from a 34-cm-thick interval of millimeter-scale laminites. Besides the 103 cycles/m and 102 cycles/m frequencies observed in the field, spectral analyses performed on the CaCO3 data set indicated other high-frequency cyclicities: 0.47 cycles/m, 0.35 cycles/m, and 0.17 cycles/m. Taking into account the estimated sedimentation rate, these frequencies correspond, respectively, to periodicities of: 1 year, 10 years, 2.1 kyr, 2.8 kyr, and 5.6 kyr. These sub-Milankovitch cyclicities have been related to annual and sunspot solar activity. The millimeter-scale couplets are interpreted as varves sedimented in an ephemeral water environment marginal to a perennial brackish water lagoonal basin. These varved sediments reflect a marked seasonality characterized by the alternation of arid and more humid climatic phases. The presence of high values of smectite (60–80%) in the clay minerals of the analyzed samples could be a consequence of these climatic oscillations from drier to moister conditions. The climatic scenario suggested in this paper for the late Messinian Lago-Mare episode is in agreement with the monsoon system that, according to some authors, starting from 5.8 Ma developed in the Mediterranean area.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
