Paleoflow Directions Measurements Using Anisotropy of Magnetic Susceptibility: A Case Study — East Carpathians, Romania

Around 15 Ma ago, when the Alcapa and Tisia lithospheric blocks collided with the southeastern border of the European plate, volcanism occurred in the eastern Carpathian-Pannonian region, forming the Călimani-Gurghiu-Harghita volcanic chain (East Carpathians). This work is the first magnetic fabric study of the pyroclastic deposits from the Călimani Mountains to identify the flow directions using the anisotropy of magnetic susceptibility (AMS) method. We have measured 80 oriented samples from different lithologies: poorly lithified pyroclastic deposits, lithic blocks of andesites and inter-bedded lava flows. The results show an orientated magnetic fabric during the pyroclastic deposits emplacement. Rock magnetic experiments revealed the co-existence of Ti-poor and medium titanomagnetite as the dominant ferromagnetic minerals. The AMS shape ellipsoids that range from oblate to tri-axial ones are interpreted to reflect the heterogeneous nature of the flow, mostly resulting from the influence of topography. All the inferred paleoflow directions in the pyroclastic deposits are in agreement with the supposed position of the main volcanic structure of the studied area —Rusca-Tihu strato-volcano.