Oligocene carbonate ramps and platforms are widespread and though they are important carbonate reservoirs, detailedstudies onthe facies organization,platformtype and internal architecture are scarce.Withinthis context, the Chattian carbonate units cropping out in Salento (southern Italy) allow detailed study of the distribution of skeletal components and facies architecture. The lower Chattian Castro Limestone, previously considered as a fringing reef, is reinterpreted as a distally steepened ramp with a distal talus induced by a paleo-escarpment in the substrate. Epiphytic biota and sedimentdweller organismsthriving in seagrassmeadows dominated produc- tion in the shallow-water euphotic zone. Seawards, large rotalid foraminifers dominated a detritic mesophotic zone. Near the edge of the escarpment, also in the mesophotic zone, luxurious growth of corals built discrete moundswithnoevidences ofwave-resistant growthfabrics. Basinward,25° to 30° dipping clinobeds abut against the escarpment where coral rudstone/floatstone textures resulted from downfall of corals and sediments. The upper Chattian Porto Badisco Calcarenite represents a homoclinal ramp dominated by packstone textures. In the euphotic inner ramp, autochthonous biota suggests the occurrence of extensive seagrass meadows. Basinward, large rotalid packstone and small coralmounds developed inmesophotic conditions, and rhodolithic floatstone to rudstone and large lepidocyclinid packstone characterize the sediments of the deeper oligophotic zone. Comminuted skeletal debris, depleted of light-dependent organisms, typifies deposition in the dysphotic/aphotic zone. In both examples, the middle ramp (meso-oligophotic zones) was themost prolificin terms of carbonate production, whereas shallow-water seagrass-related production (euphotic) was much less important. Corals builtmounds, also in themesophotic zone but never reached sea level. Hydrodynamic condi- tions in themeso-oligophotic zone are better explained by breaking of internalwaves, and their induced up- and down-slope currents, instead of the surface stormwaves
Carbonate ramp evolution during the Late Oligocene (Chattian), Salento Peninsula, southern Italy
MORSILLI, Michele;
2014
Abstract
Oligocene carbonate ramps and platforms are widespread and though they are important carbonate reservoirs, detailedstudies onthe facies organization,platformtype and internal architecture are scarce.Withinthis context, the Chattian carbonate units cropping out in Salento (southern Italy) allow detailed study of the distribution of skeletal components and facies architecture. The lower Chattian Castro Limestone, previously considered as a fringing reef, is reinterpreted as a distally steepened ramp with a distal talus induced by a paleo-escarpment in the substrate. Epiphytic biota and sedimentdweller organismsthriving in seagrassmeadows dominated produc- tion in the shallow-water euphotic zone. Seawards, large rotalid foraminifers dominated a detritic mesophotic zone. Near the edge of the escarpment, also in the mesophotic zone, luxurious growth of corals built discrete moundswithnoevidences ofwave-resistant growthfabrics. Basinward,25° to 30° dipping clinobeds abut against the escarpment where coral rudstone/floatstone textures resulted from downfall of corals and sediments. The upper Chattian Porto Badisco Calcarenite represents a homoclinal ramp dominated by packstone textures. In the euphotic inner ramp, autochthonous biota suggests the occurrence of extensive seagrass meadows. Basinward, large rotalid packstone and small coralmounds developed inmesophotic conditions, and rhodolithic floatstone to rudstone and large lepidocyclinid packstone characterize the sediments of the deeper oligophotic zone. Comminuted skeletal debris, depleted of light-dependent organisms, typifies deposition in the dysphotic/aphotic zone. In both examples, the middle ramp (meso-oligophotic zones) was themost prolificin terms of carbonate production, whereas shallow-water seagrass-related production (euphotic) was much less important. Corals builtmounds, also in themesophotic zone but never reached sea level. Hydrodynamic condi- tions in themeso-oligophotic zone are better explained by breaking of internalwaves, and their induced up- and down-slope currents, instead of the surface stormwavesI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
