Some data on the characteristics of the geomagnetic field at the Gauss–Matuyama magnetic chron boundary from the Pirnuar section, West Turkmenistan

Abstract

Extremely scarce data have been published on the structure of the geomagnetic field during the Gauss and early Matuyama chrons until recently. Only a few papers contain information about the characteristics of the field during the Gauss–Matuyama reversal, derived by studying the terrestrial sediments. This motivated us to revisit the paleomagnetism of the sedimentary rocks of Akchagyl age in the section of the Pirnuar Valley in West Kopet Dag, for the first time studied by us in the late 1960s–early 1970s. These rocks are the analog of the top Piacenzian–bottom Gelasian and span the mentioned time interval. The reanalysis was conducted with the use of the state-of-the-art paleomagnetic techniques and modern magnetostratigraphic timescale. We have studied a number of the characteristics which enabled us to distinguish the rocks whose remanence is most likely to have a depositional origin. Based on the paleomagnetic characteristics of these rocks, we reconstructed the structure of the paleomagnetic field for the studied interval (~270 ka) of the initial stage of the Gauss–Matuyama reversal and revealed the excursions at the final and initial stages of the Gauss and Matuyama chrons. This analysis has significantly updated the time constraints of the rock sedimentation in the studied section and supported the locations of the virtual geomagnetic pole during the reversal, obtained previously.