Palaeomagnetism of the Upper Miocene- Lower Pliocene lavas from the East Carpathians: contribution to the paleosecular variation of geomagnetic field.

Mădălina Vişan,Cristian Necula,Cristian G Panaiotu,Anca Dumitru

doi:10.1038/srep23411

Mădălina Vişan, Cristian Necula + Show 2 more

Open Access

https://doi.org/10.1038/srep23411

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Journal: Scientific reports	Publication Date: Mar 21, 2016
Citations: 5	License type: CC BY 4.0

Affiliation: University of Bucharest, Romanian Academy

Abstract

Investigations of the paleosecular variation of the geomagnetic field on geological timescales depend on globally distributed data sets from lava flows. We report new paleomagnetic results from lava flows of the East Carpathian Mountains (23.6°E, 46.4°N) erupted between 4 and 6 Ma. The average virtual geomagnetic pole position (76 sites) includes the North Geographic Pole and the dispersion of virtual geomagnetic poles is in general agreement with the data of the Time Averaged geomagnetic Field Initiative. Based on this study and previous results from the East Carpathians obtained from 0.04–4 Ma old lava flows, we show that high value of dispersion are characteristic only for 1.5–2.8 Ma old lava flows. High values of dispersion during the Matuyama chron are also reported around 50°N, in the global paleosecular variation data set. More data are needed at a global level to determine if these high dispersions reflect the behaviour of the geomagnetic field or an artefact of inadequate number of sites. This study of the East Carpathians volcanic rocks brings new data from southeastern Europe and which can contribute to the databases for time averaged field and paleosecular variation from lavas in the last 6 Ma.

Highlights

The Earth’s magnetic field is generated by geodynamo processes in the Earth’s liquid outer core and its direction and strength vary with time[1]
After the main collisional events at 11 Ma9, volcanism took place in the East Carpathians forming the Călimani – Gurghiu – Harghita (CGH) volcanic chain (Fig. 1). This volcanic chain consists of calc-alkaline products that occurred along the easternmost margin of the rigid Transylvanian block, in the front of European Platform and it marks the end of the post-collisional subduction-related magmatism along the front of the European convergent plate margin[10]
We have measured paleomagnetic directions recorded by lava flows erupted between 4–6 Ma in the East Carpathians in order to augment and improve the observations relevant to understanding the time averaged character of the Earth’s magnetic field

Summary

Introduction

The Earth’s magnetic field is generated by geodynamo processes in the Earth’s liquid outer core and its direction and strength vary with time[1]. After the main collisional events at 11 Ma9, volcanism took place in the East Carpathians forming the Călimani – Gurghiu – Harghita (CGH) volcanic chain (Fig. 1). This area was studied in earlies 70s, but this pioneering paleomagnetic study[15] for the East Carpathians does not fulfil any more the modern paleomagnetic quality standards for PSV studies For this reason we sampled 84 new sites in the main volcanic structures from the North Harghita Mountains (Vârghiş, Ivo-Cocoizaş and Ostoroş) and a small volcanic structure from the southern tip of the Gurghiu Mountains (Supplementary Fig. S1).

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Conclusion