GPR study of bedding planes, fractures and cavities in limestone

We performed a multi-fold GPR study at a Cretaceous-Tertiary (K-T) outcrop in limestone layers of the Peri-Adriatic carbonatic platform (Italy). Primary objective of the study was imaging of the K-T contact and mapping of localized depth variations in a general framework of homoclinal limestone layers. A secondary objective was the study of faults, fractures and cavities of interest for engineering purposes. A combination of 2-D and 3-D multi-fold techniques was used to image and map structural and stratigraphic features. A 200 sqm grid was surveyed with 1 metre cross-line spacing and 5 cm in-line trace interval. The K-T contact is electromagnetically transparent, and it is actually deduced from paleontologic evidence. Due to the homoclinal trend, K-T topography is reconstructed from the bedding planes bounding the contact. Fractures antithetic to bedding planes are imaged by 2-D stack and migrated profiles. Part of the fractures can be considered small transtensional faults. The results obtained provide the first geophysical evidence of small-scale transtensive deformation in the area. Curvilinear radar reflector, intersecting the homoclinal bedding planes, are imaged in faulted zones and are possibly related to limestone buildups. A fractured rock volume develops into a cavity with average estimated section of 4 sqm.