We propose a high-resolution regional to global scale correlation of two Hauterivian/Barremian shallow water carbonate platform sections belonging to different palaeogeographic domains of the Southern margin of the Tethys. These successions are now located more than 500 km apart and are represented by 137 m of core drilled at Monte Raggeto (southern Apennines, Italy) and by 80 m of well stratified rocks cropping out in the Podgorica Mountains (Dinarides, Montenegro). They display three superimposed orders of stratigraphic cyclicity defined by elementary cycles grouped into bundles and superbundles and attributed to orbitally induced composite sea-level fluctuations. Elementary cycles are interpreted as the precession and the obliquity periodicities (2040 ky), while bundles and superbundles correspond to the short (100 ky) and long (400 ky) eccentricity cycles, respectively. As both the ratios between the elementary cycles and the bundles and between the bundles and the superbundles do not always reflect the classical 5:1 and 4:1 relationship, the sedimentary record of both the studied sections is likely to include omission of bundles or their portion. The general evolution of depositional and diagenetic facies, the vertical change in thickness of the cyclic units, and the interpretation of superbundles as small-scale depositional sequences, suggest that elementary cycles and their groups are superimposed on lower-frequency environmental oscillations. These display an upward Transgressive/Regressive Trend (T/RT) of the facies and testify to larger-scale variations of accommodation potential on the shelf. T/RTs, sequence stratigraphic interpretation of the superbundles as well as the common occurrence of the biostratigraphic dated Hauterivian/Barremian boundary in the studied sections, support the long-distance regional correlation between the successions to be carried out on the 100 ky scale. Moreover, by assuming the maximum flooding intervals of time-equivalent superbundles as virtually isochronous intervals, we have detected stratigraphic gaps of 1200 and 600 ky in the Monte Raggeto and in the Podgorica Mountains sections, respectively. Both sections are formed of 10 complete superbundles each of them testifying to the 400-ky-long eccentricity. Hence, the Monte Raggeto and Podgorica Mountains successions represent a duration of at least 4.0 My in terms of elapsed time, regardless of gaps within the stratigraphic record. Finally, a correlation between the orbitally induced compared sections and both the 3rd order Tethyan stratigraphic cycles and the global cycle chart is suggested. Our study confirms that cyclically organized, shallow marine carbonate platform deposits controlled by orbitally induced sea-level fluctuations represent a powerful tool for high-precision regional and global correlations. This can be of fundamental importance for quantification of sedimentary, diagenetic, and evolutionary processes as well as for the understanding of autocyclic versus allocyclic control on sequence development.
Regional to global correlation of lower Cretaceous (Hauterivian-Barremian) shallow-water carbonates of the southern Apennines (Italy) and Dinarides (Montenegro), southern Tethyan Margin.
RASPINI A
2004
Abstract
We propose a high-resolution regional to global scale correlation of two Hauterivian/Barremian shallow water carbonate platform sections belonging to different palaeogeographic domains of the Southern margin of the Tethys. These successions are now located more than 500 km apart and are represented by 137 m of core drilled at Monte Raggeto (southern Apennines, Italy) and by 80 m of well stratified rocks cropping out in the Podgorica Mountains (Dinarides, Montenegro). They display three superimposed orders of stratigraphic cyclicity defined by elementary cycles grouped into bundles and superbundles and attributed to orbitally induced composite sea-level fluctuations. Elementary cycles are interpreted as the precession and the obliquity periodicities (2040 ky), while bundles and superbundles correspond to the short (100 ky) and long (400 ky) eccentricity cycles, respectively. As both the ratios between the elementary cycles and the bundles and between the bundles and the superbundles do not always reflect the classical 5:1 and 4:1 relationship, the sedimentary record of both the studied sections is likely to include omission of bundles or their portion. The general evolution of depositional and diagenetic facies, the vertical change in thickness of the cyclic units, and the interpretation of superbundles as small-scale depositional sequences, suggest that elementary cycles and their groups are superimposed on lower-frequency environmental oscillations. These display an upward Transgressive/Regressive Trend (T/RT) of the facies and testify to larger-scale variations of accommodation potential on the shelf. T/RTs, sequence stratigraphic interpretation of the superbundles as well as the common occurrence of the biostratigraphic dated Hauterivian/Barremian boundary in the studied sections, support the long-distance regional correlation between the successions to be carried out on the 100 ky scale. Moreover, by assuming the maximum flooding intervals of time-equivalent superbundles as virtually isochronous intervals, we have detected stratigraphic gaps of 1200 and 600 ky in the Monte Raggeto and in the Podgorica Mountains sections, respectively. Both sections are formed of 10 complete superbundles each of them testifying to the 400-ky-long eccentricity. Hence, the Monte Raggeto and Podgorica Mountains successions represent a duration of at least 4.0 My in terms of elapsed time, regardless of gaps within the stratigraphic record. Finally, a correlation between the orbitally induced compared sections and both the 3rd order Tethyan stratigraphic cycles and the global cycle chart is suggested. Our study confirms that cyclically organized, shallow marine carbonate platform deposits controlled by orbitally induced sea-level fluctuations represent a powerful tool for high-precision regional and global correlations. This can be of fundamental importance for quantification of sedimentary, diagenetic, and evolutionary processes as well as for the understanding of autocyclic versus allocyclic control on sequence development.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
