Reappraisal of paleomagnetic data from Gargano (South Italy)

Abstract

VandenBerg, J., 1983. Reappraisal of paleomagnetic data from Gargano (South Italy). In: E. McClelland Brown and J. VandenBerg (Editors), Palaeomagnetism of Orogenic Belts. Tectonophysics, 98: 29-41. The platform limestones of Apulia (Italy) outcropping in the Gargano peninsula have been restudied. Paleomagnetic research has been carried out on Upper Cretaceous, Lower Cretaceous and Jurassic rocks. Despite the low intensities of the NRM (10-100 PA/m), all samples (268) could be cleaned by stepwise A.F. and/or thermal demagnetization treatments. NRM directions could be determined accurately and reproducibly for 85% of the samples, using a ScT cryogenic magnetometer and double precision measuring procedures. NRM of the Jurassic limestone is carried by secondary haematite and the results are therefore rejected from further consideration. The Upper and Lower Cretaceous limestones have an NRM carried by magnetite. Minor bedding tilt corrections improve the grouping of the site-mean results. The Upper Cretaceous “Scaglia” limestone (Turonian-Senonian) reveals a characteristic mean direction of decl. = 327.7”, incl. = 38.2O, a ss = 4.3’ (21 sites), while the Lower Cretaceous “Maiolica” limestone (Neocomian-Aptian/Albian) reveals a characteristic mean direction of decl. = 303.1 O, incl. = 35.1”. as,s = 8.7O (8 sites). The Cretaceous results show a post-Aptian/Albian counterclockwise rotation of about 25”, which is expressed by the smeared distribution of the Late Cretaceous site-mean results, and a post-Senonian (i.e. Tertiary) counterclockwise rotation of the same amount with respect to the pole. These results are in excellent agreement with contemporaneous paleomagnetic results from other peri-Adriatic regions. A Tertiary counterclockwise rotation of all the stable Adriatic block is strongly supported by the new results.