3D outcrop model made by UAV/drone of an Oligocene carbonate platform, Morro de Toix (Calpe, Alicante, SE Spain)

Abstract

Morro de Toix tertiary Tethyan carbonate platform exposed along the Alicante coast of southeast Spain has permitted to study the morphology and arrangement of facies successions. The steep sides of the 300-m-high massif, up to 70-m vertical cliff, difficult its observation and sampling, although its poor vegetation offers an excellent candidate to produce a high-resolution 3D outcrop model by drone photogrammetry. 3496 valid pictures were taken in six UAV (Unmanned Aerial Vehicle) drone flights and about 20 4K-videos, using two aircrafts (DJI Mavic 3 enterprise and DJI air 2s) even the quantity of the pictures taken, the heavily karstified overstep part of the sea-cliff was not well constrained. The model has a pixel resolution of 19.2 cm/pixel, covering an area of 1.12 km2. The orthomosaic produced has a quality of 5.55 cm/pixel and a size of 39090 x 23872 pixels. The massif stratification is mainly vertical and to the eastern tip (the Toix cape) the dip is 80º to the north-northeast. Five major high-frequency sequences can be differentiated, the first one Eocene, and the rest Early Rupelian in age. Each of the Oligocene sequence show a shallowing trend from open marine shelf to restricted inner shelf being the first environments thicker in newest sequences. The four Oligocene sequences, together, show an overall upward-deepening trend and subsequent drowning, overlain by glauconitic mudstones with turbidites. A parallel to the stratification fault separates the Eocene to the Oligocene sequences indicating a hanging-wall movement to the West. The whole massif is cut by two sets of high-angle normal faults near perpendicular to the stratification, one set WNW-ESE producing the longest sea-cliff and the other N-S strike cutting the previous one in a near 90º, producing also a shorter sea-cliff. The drowning of the Oligocene platform resulted probably by the extensional event produced the first mentioned fault. The Toix massif today is uplifted by the sets of sea-cliff faults. The 3D model is an outcrop digital twin of the Toix massif allowing a wide and complete observation of the hardly accessible massif without vegetation cover.Funded by projects GVA-THINKINAZUL/2021/039, and PID2020-114381GB-I0