The Sardinia and southern Apennines-Apulia carbonate platforms were respectively parts of the northern and southern continental margins of the Mesozoic Tethys. The Upper Cretaceous limestones studied in several areas of these regions accumulated on temperate-type, ramp-like open shelves. Sediments are mostly bioerosion-derived bioclasts essentially made up of rudists with a variable contribution of benthic foraminifers, bryozoans and red algae. Non-skeletal grains are absent and the skeletal components are indicative of the foramol sensu lato association, assuming clear rhodalgal characteristics in the Sardinia sequences. The lithofacies of the studied successions are dominated by skeletal fine to coarse grainstones and rudstones. They show evidence of storm and current winnowing. Rudists are rarely preserved in growth position. They dwelled in loose sediments giving rise to limited and scattered rudist-rich bodies whose relief on the surrounding sea bed was slight and limited to the last generation of individuals which grew with constratal pattern. No rigid frameworks characterized these rudist accumulations that did not develop into true reefs. No rimming marginal bodies were present and from the resulting open shelves the bioerosion-derived finer fractions were swept off to the deeper areas, where the coarser skeletal debris basically accumulated by means of granular flows. In the Recent, similar foramol deposits are largely spread over wide sectors of the continental shelves of temperate seas. Nevertheless, similar situations may also develop in tropical/subtropical regions if characterized by conditions of ecological stress. In the Senonian the peri-Tethyan platforms evolved from "warm-water" types to relatively "cooler" types. In the latter, complex interplaying factors may have been effective in controlling different environmental and depositional conditions, resulting in modified lithofacies features in the opposing margins of the Mediterranean Tethys.
Upper Cretaceous temperate-type open shelves from northern (Sardinia) and southern (Apennines-Apulia) Mesozoic Tethyan margins
RUBERTI, Daniela;
1997
Abstract
The Sardinia and southern Apennines-Apulia carbonate platforms were respectively parts of the northern and southern continental margins of the Mesozoic Tethys. The Upper Cretaceous limestones studied in several areas of these regions accumulated on temperate-type, ramp-like open shelves. Sediments are mostly bioerosion-derived bioclasts essentially made up of rudists with a variable contribution of benthic foraminifers, bryozoans and red algae. Non-skeletal grains are absent and the skeletal components are indicative of the foramol sensu lato association, assuming clear rhodalgal characteristics in the Sardinia sequences. The lithofacies of the studied successions are dominated by skeletal fine to coarse grainstones and rudstones. They show evidence of storm and current winnowing. Rudists are rarely preserved in growth position. They dwelled in loose sediments giving rise to limited and scattered rudist-rich bodies whose relief on the surrounding sea bed was slight and limited to the last generation of individuals which grew with constratal pattern. No rigid frameworks characterized these rudist accumulations that did not develop into true reefs. No rimming marginal bodies were present and from the resulting open shelves the bioerosion-derived finer fractions were swept off to the deeper areas, where the coarser skeletal debris basically accumulated by means of granular flows. In the Recent, similar foramol deposits are largely spread over wide sectors of the continental shelves of temperate seas. Nevertheless, similar situations may also develop in tropical/subtropical regions if characterized by conditions of ecological stress. In the Senonian the peri-Tethyan platforms evolved from "warm-water" types to relatively "cooler" types. In the latter, complex interplaying factors may have been effective in controlling different environmental and depositional conditions, resulting in modified lithofacies features in the opposing margins of the Mediterranean Tethys.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
