New palaeodirections and palaeointensity data from extensive profiles through the Ediacaran section of the Volyn Basalt Province (NW Ukraine)

Abstract

Summary Changes of the geomagnetic field over geologic time scales can be used to study the evolution and processes of its sources in Earth's deep interior. As a stark contrast to the geomagnetic field behaviour of the recent past, the field in the late Neoproterozoic is defined by ambiguous polar wander paths, ultra-low field strengths and a period of extreme reversal hyperactivity. Palaeointensity data from this time are still scarce and conclusions made from these data suffer from large uncertainties brought by a low sampling density. In this study, we present new palaeomagnetic and palaeointensity data from quarry outcrops and five deep drill cores, covering the longest and most complete profiles through the Ediacaran units in the Volyn Basalt Province (NW-Ukraine) to date. Palaeodirectional analysis of thermal and alternating field demagnetisation experiments reveal at least six reversals in the profile as well as four palaeopoles that agree with previously published poles. Whole-rock palaeointensity estimates are derived from a multi-method approach that utilises thermal and microwave Thellier experiments in Coe- and IZZI-protocol as well as Wilson and double-heating-Shaw experiments. These produce instantaneous site-mean palaeointensity estimates in the range of 2.1±0.4 µT - 11.1±3.5 µT and virtual dipole moments in the range of 0.31±0.06 ×1022Am2 - 1.67±0.53 ×1022Am2. Small-scale variations of palaeointensities throughout the profile not only show extremely weak field strengths around polarity changes but could also suggest that the field strength never fully recovered between reversals. These new results increase the density of intensity data coverage for Baltica in the Late Ediacaran and, in combination with previously published Ediacaran dipole moments, support an extremely weak field that seems to increase in strength towards the Ediacaran-Cambrian transition.

Palaeomagnetism of the Vendian traps of Volyn, southwestern margin of the East European Platform, P. 2: magnetostratigraphy

“…This is a continuation of previous studies of upper part of the Volyn series described by Bakhmutov et al [2021]. In the recent works [Shcherbakova et al, 2020;Thallner et al, 2022], the results of palaeointensity determinations of the Volyn series basalts showed the ultra-low dipole moment of Earth's magnetic field which coincident with other palaeomagnetic data for Ediacaran indicating an extremely weak geomagnetic field. Clear stratification and correlation of the basalt and tuff layers by magnetic parameters allow us to determine the magnetic field reversals throughout the stratigraphic succession of the Volyn series of about 400 m thick.…”

“…In recent publications on palaeointensity of Volyn basalts [Shcherbakova et al, 2020;Thallner et al, 2022] the thermomagnetic and electron microscopic studies of basalts from Ratne and Luchichiv suites confirmed the previous results and showed the Curie temperature of 550-590 °C indicating the presence of titanomagnetite with a low content of Ti. The temperature-dependent susceptibility curves of some samples of basalts and backed contact tuffs from the Ratne, Babyne and Zabolottya suites demonstrated another Curie temperature of ~650 °C probably due to a high degree of oxidation of the magnetite phase resulting in increases of Curie temperature.…”

“…The boreholes uncover the Volyn traps succession about 400 m thickness represented by an alternation of basalt flows with lava breccias and tuffs. In this paper, we are presented detailed information about palaeomagnetic study and magnetostratigraphy of the sequence in addition to palaeointensity determination presented in [Thallner et al, 2022]. This sequence stratigraphycally lies below the sections described in [Bakhmutov et al, 2021].…”

MCADAM: A Continuous Paleomagnetic Dipole Moment Model for at Least 3.7 Billion Years

“…In total, 295 new sites from 34 studies have been added to the PINT v8.1.1 database, increasing the total number of site mean records ( N Sites ) to 4,648. These data include contributions constraining the field during the Cambrian/Ediacaran (e.g., Thallner, Biggin, & Halls, 2021; Thallner, Biggin, McCausland, & Fu, 2021; Thallner et al., 2022; Zhou et al., 2022) and Neoproterozoic (e.g., Lloyd, Biggin, et al., 2021), which remain under‐sampled relative to other geologic intervals.…”

Substantiation of research results on energy efficiency of basalt crushing

“…Intensive quarrying of basalt deposits is conducted in Ukraine. It is mainly concentrated in the western area of the country and most widely -in Rivne region [1]. The basalt mined in this process is used in construction.…”