A detailed carbon-isotope study has been carried out on a Santonian (Upper Cretaceous) carbonate platform succession which crops out at Monte SantErasmo (southern Italy). Previous cm-scale studies on this succession have shown that high-frequency eustatic changes, due to Earths orbital fluctuations, controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles, bundles (groups of 3-5 elementary cycles) and superbundles (groups of 3-4 bundles). While the elementary cycles, which correspond to single beds, suggest a control due to the Earths precession, the bundles and superbundles record the short- (~100 kyr) and long- (~400 kyr) eccentricity periodicity respectively. The ä13C signal of the Monte SantErasmo succession is cyclic in nature and may be considered to be a reliable proxy of the sedimentary evolution (and related sea-level history) of the analyzed sequence. The carbon-isotope cyclicity is recorded at bundle and superbundle level, but it is not evident at the scale of the elementary cycles, at least with the sampling interval used in this study. Spectral analysis of the ä13C record shows two main peaks corresponding to the short- and long- eccentricity periodicity, while the precession signal is not evident in the power spectrum. In addition, lithofacies analysis shows that in each bundle (and superbundle) higher C-isotope values occur in sediments characterized by marine cements, while lower values are normally found in more restricted deposits overprinted by early meteoric diagenesis. Early diagenesis, driven by periodic sea-level fluctuations, developed either in shallow-subtidal (marine diagenesis) or in subaerial-exposed (meteoric overprint) sedimentary environments and directly influenced the carbon-isotope signature. As a consequence, the ä13C record at Monte SantErasmo reflects high-frequency climatic oscillations controlling both environmental and early diagenetic changes. The long-term isotopic record is similar to that of contemporaneous pelagic sections in England and elsewere in Italy. It is concluded that the ä13C signature of shallow-water carbonates, like those of Monte SantErasmo, offers great potential for correlation with coeval sections, including those of the pelagic realm.
Cyclostratigraphy and high frequency carbon isotope fluctuations in Upper Cretaceous shallow-water carbonate, southern Italy.
2002
Abstract
A detailed carbon-isotope study has been carried out on a Santonian (Upper Cretaceous) carbonate platform succession which crops out at Monte SantErasmo (southern Italy). Previous cm-scale studies on this succession have shown that high-frequency eustatic changes, due to Earths orbital fluctuations, controlled the hierarchical organization of the depositional and early diagenetic features in elementary cycles, bundles (groups of 3-5 elementary cycles) and superbundles (groups of 3-4 bundles). While the elementary cycles, which correspond to single beds, suggest a control due to the Earths precession, the bundles and superbundles record the short- (~100 kyr) and long- (~400 kyr) eccentricity periodicity respectively. The ä13C signal of the Monte SantErasmo succession is cyclic in nature and may be considered to be a reliable proxy of the sedimentary evolution (and related sea-level history) of the analyzed sequence. The carbon-isotope cyclicity is recorded at bundle and superbundle level, but it is not evident at the scale of the elementary cycles, at least with the sampling interval used in this study. Spectral analysis of the ä13C record shows two main peaks corresponding to the short- and long- eccentricity periodicity, while the precession signal is not evident in the power spectrum. In addition, lithofacies analysis shows that in each bundle (and superbundle) higher C-isotope values occur in sediments characterized by marine cements, while lower values are normally found in more restricted deposits overprinted by early meteoric diagenesis. Early diagenesis, driven by periodic sea-level fluctuations, developed either in shallow-subtidal (marine diagenesis) or in subaerial-exposed (meteoric overprint) sedimentary environments and directly influenced the carbon-isotope signature. As a consequence, the ä13C record at Monte SantErasmo reflects high-frequency climatic oscillations controlling both environmental and early diagenetic changes. The long-term isotopic record is similar to that of contemporaneous pelagic sections in England and elsewere in Italy. It is concluded that the ä13C signature of shallow-water carbonates, like those of Monte SantErasmo, offers great potential for correlation with coeval sections, including those of the pelagic realm.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
