Digital 3d Modelingby Laser Scanning Technique of Lepidocyclina Limestone (Bolognano Formation, Majella)

To study a sedimentary structures the prerequisite is the availability of 3D outcrop. Sedimentary structures reproductions may be based on drawings, supplied by photographs. However drawings and photographs present and cause different problems, for examples the accuracy of drawings as well as photographs are dependent on the direction and intensity of light. Laser scanners produce a "point cloud" giving an accurate and precise three dimensional representation of a considered target. Terrestrial laser scanner has been used in order to obtain a model of the trampled area taking in account that terrestrial laser scanner allows a highly detailed geometric characterization also on target situated at distances up to tens of meters. The acquisition has been performed with Riegl VZ 400 laser scanner from a distance of approximately 90 m, setting a mean point to point spacing of 0,005 m . The 3D digital modelling was performed on the sedimentary structures of the Chattian Lepidocyclina limestone of Majella (Formazione di Bolognano) along a 200 m long transect. The Lepidocyclina Limestones of the Majella area were deposited in the oligophotic and aphotic zones of a carbonate ramp (BRANDANO et alii 2012). The taphonomic analysis implies a parautochthonous origin for an important part of the sediments in a middle ramp environment, and an increase with depth of autochthonous sediments in the outer ramp. In the Lepidocyclina Limestone, sediment sorting is not directly related to a decrease in water energy linked to increasing water depth. Instead, sediment-sorting is attributed to the effect of unidirectional currents. Grainstones dominate the middle ramp environment. Palaeocurrent patterns suggest the occurrence of a strong, generally north-west directed flowthat affected the middle ramp environment. It is believed that this basinwardflowing current led to the development of a wide (10×15 km), downslope-migrating dune field. It is proposed that the combined effects of coastal set-up and strong return currents caused by storms and winds were able to produce basinward migrating bedforms In this work it will be presented the result of the 3D modelling of the sedimentary structures of the sigmoidal crossbedded grainstone that represent the record of submarine dune migration in the middle ramp environment.