Palaeomagnetism of the South Harghita volcanic rocks of the East Carpathians: implications for tectonic rotations and palaeosecular variation in the past 5 Ma

Abstract

SUMMARY LavasofPliocene–QuaternaryageweresampledintheSouthHarghitaMountains,whichform the southern end of the Cu alimani–Gurghiu–Harghita volcanic chain of the East Carpathians. The analyses of 68 volcanic sites in the South Harghita Mountains provided 62 sites with well-constrained directional data (n > 5 and k > 50) in an age interval ranging from 0.5 to 4.3Ma. The age and polarity for the 62 sites (38 normal and 24 reversed) are consistent with the Geomagnetic Reversal Time Scale and support the model of the southward migration of the volcanism. The distribution of the VGPs is Fisherian and the mean pole position, both from all contributing sites and from the 53 sites older than 2 Ma, includes the spin axis. This result is consistent with the absence of important vertical axis rotations after the emplacement of the volcanicrocksinagreementwithtectonicmodelsforthePliocene–Quaternaryevolutionofthe bending area of the East Carpathians. Virtual geomagnetic pole dispersions are consistently high compared with global values obtained between 40 and 55 ◦ N, but closer to the values obtained only from the Time Averaged geomagnetic Field Initiative studies for the same latitudinal band. Our data are compatible with the prediction of the statistical palaeosecular variationmodelTK03.Theinclinationanomalyislessthan1 ◦ inaccordwiththeTotalAverage Field global data. These palaeomagnetic data from the South Harghita volcanic rocks are the first data from the southeastern Europe which can be considered in the databases for time averaged field and palaeosecular variation from lavas analyses in the last 5 Ma.