Options
Franceschi, Marco
Loading...
Preferred name
Franceschi, Marco
2 results
Now showing 1 - 2 of 2
- PublicationRestrictedDiscrimination between marls and limestones using intensity data from terrestrial laser scannerTerrestrial Laser Scanner (TLS) is an active instrument widely used for physical surface acquisition and data modeling. TLS provides both the geometry and the intensity information of scanned objects depending on their physical and chemical properties. The intensity data can be used to discriminate different materials, since intensity is proportional, among other parameters, to the reflectance of the target at the specific wavelength of the laser beam. This article focuses on the TLS-based recognition of rocks in simple sedimentary successions mainly constituted by limestones and marls. In particular, a series of experiments with an Optech ILRIS 3D TLS was carried out to verify the feasibility of this application, as well as to solve problems in data acquisition protocol and data processing. Results indicate that a TLS intensity-based discrimination can provide reliable information about the clay content of rocks in clean outcrop conditions if the geometrical aspects of the acquisition (i.e. distance) are taken into account. Reflectance values of limestones, marls and clays show, both in controlled conditions and in the field, clear differences due to the interaction of the laser beam (having a 1535 nm wavelength) with H2O- bearing minerals and materials. Information about lithology can be therefore obtained also from real outcrops, at least if simple alternation of limestones and marls are considered. Comparison between reflectance values derived from TLS acquisition of an outcrop and the clay abundance curves obtained by gas chromatography on rock samples taken from the same stratigraphic section shows that reflectance is linked by an inverse linear relationship (correlation coefficient r = −0.85) to the abundance of clay minerals in the rocks. Reflectance series obtained from TLS data are proposed as a tool to evaluate the variation of clay content along a stratigraphic section. The possibility of linking reflectance values to lithological parameters (i.e. clay content) could provide a tool for lithological mapping of outcrops, with possible applications in various fields, ranging from petroleum geology to environmental engineering, stratigraphy and sedimentology.
76 1 - PublicationRestrictedTerrestrial Laser Scanner imaging for the cyclostratigraphy and astronomical tuning of the Ypresian–Lutetian pelagic section of Smirra (Umbria–Marche Basin, Italy)(2015)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Terrestrial laser scanner imaging is applied, together with calcimetry and lithofacies logging, for the cyclostratigraphic characterization of the Ypresian–Lutetian pelagites exposed in the Smirra section (Umbria–Marche Basin, Italy). The necessary chronostratigraphic framework is provided by detailed bio- and magnetostratigraphic analyses, which allow locating the Ypresian–Lutetian boundary in this section. Terrestrial laser scanner intensity is compared to carbonate content values obtained through calcimetric analyses carried out on samples taken from the same section, and is found to represent a good proxy for lithology in these pelagic homogenites. Time-series analysis highlights Milankovitch frequencies, particularly evident in the high-resolution terrestrial laser scanner intensity series. The recognition of distinctive low-frequency (> 1 Myr) features in the amplitude oscillations of short eccentricity as well as its ~ 400 kyr modulation (long eccentricity), promote a tuning of the Smirra series using the most recent astronomic solution (La2010 nominal), which provides insights on the ages of the Y–L boundary and of the main biostratigraphic and magnetostratigraphic events in the Umbria–Marche Basin. Results confirm the value of high-resolution (mm-scale) terrestrial laser scanning for scrutinizing pelagite successions in search of low-frequency cycles that may help in the refinement of the astrochronological time scale.251 4