Refining geomagnetic field intensity changes in Europe between 200 CE and 1800 CE. New data from the Mediterranean region

Abstract

Absolute past geomagnetic intensity values can mainly be recovered by fired archaeological materials and volcanic rocks. Here, we present 10 new archeointensities from the Mediterranean region that help to better constrain geomagnetic field intensity changes in Europe over the last two millennia. The new archeointensity results were obtained from the Thellier classical method including thermoremanent magnetization (pTRM) checks and both the TRM anisotropy and cooling rate corrections and were derived from at least three specimens. The new data presented, together with a selection of previous archeointensities satisfying a set of quality criteria, confirm the presence of several intensity maxima in Europe over the last 2000 years. In particular, the new archeointensities allow to better define the starting point of the double-oscillation feature that occurred in Europe during the second half of the first millennium CE, and reinforce the existence of a relative maximum at the end of the 14th century -beginning of the 15th century in Western Europe. From selected European archeointensities two new paleosecular variation curves are constructed for Western and Eastern Europe using temporal cubic b-splines in a bootstrap approach. The obtained curves suggest that the occurrence of the intensity maxima is characterized by a period of about 300 ± 50 years. In addition, our results suggest that the maxima do not occur simultaneously in Western and Eastern Europe, pointing out an intensity eastward drift with a mean lag-time of about 100 years.

Rapid Intensity Decrease During the Second Half of the First Millennium BCE in Central Asia and Global Implications

“…The hysteresis ratios obtained are presented in a Day plot (Day et al., 1977), modified as proposed by Dunlop (2002) to see where our samples lay in the theoretical PSD‐SD (pseudo‐single domain PSD/single domain SD) regions for magnetite, including magnetite mixing (Figure 2d). As commonly observed in other archeointensity studies (e.g., Gómez‐Paccard et al., 2019; Gómez‐Paccard, McIntosh, et al., 2012; Rivero‐Montero, Gómez‐Paccard, Pavón‐Carrasco, et al., 2021), most of the samples fall in the PSD region. No SP content was detected by using J‐coercivity measurements, which can be used to estimate SP existence with the decay of the SIRM when reversing the field (Jasonov et al., 1998).…”

Archaeomagnetism in the Levant and Mesopotamia Reveals the Largest Changes in the Geomagnetic Field

“…However, global models are smoothed by design, as they require a tradeoff between model complexity and fit to heterogeneous data. Regional intensity curves provide important insights into field behavior (Cai et al., 2017 ; Garcia et al., 2021 ; Genevey et al., 2016 , 2021 ; Rivero‐Montero et al., 2021 ; Schnepp et al., 2020 ), but they depend on the quality of the underlying source data. One of the most significant limiting factors for both global and regional field modeling is the precision and accuracy of the published ages.…”

Holocene Paleosecular Variations Recorded by Relict Magnetic Minerals in the Anoxic Black Sea Sediments

“…At about 3 ka BP, the Levantine Iron Age Anomaly (LIAA) with high intensity and rapid secular variations was firstly reported from the Levant region (Ben‐Yosef et al., 2009; Shaar et al., 2016) and later found around the Mediterranean region (Molina‐Cardín et al., 2018; Osete et al., 2020; Rivero‐montero, Gómez‐Paccard, Kondopoulou, et al., 2021). An additional high field intensity at ∼1.2 ka BP with a double‐oscillation feature was commonly observed in European archeomagnetic results (e.g., Genevey et al., 2016; Gómez‐Paccard et al., 2012; Kovacheva et al., 2014), though the maxima do not occur simultaneously in Western and Eastern Europe (Rivero‐Montero, Gómez‐Paccard, Pavón‐Carrasco, et al., 2021). During the past millennia, low paleointensity anomalies were found in southern Africa (∼650 years BP; Tarduno et al., 2015), and southern Asia (∼750 years BP; Cai et al., 2021).…”

“…After shifting about 0.6 ka indicated by red arrows, this pattern can be correlated with the high intensity feature at about 1.2 ka BP which are commonly found at Europe (Genevey et al., 2016). In high‐resolution archeomagnetic datasets mainly from central Europe and the Balkan Peninsula, the high intensity feature exhibit two peaks and is regarded as a double‐oscillation at about 1.2 ka (Kovacheva et al., 2014; Rivero‐Montero, Gómez‐Paccard, Pavón‐Carrasco, et al., 2021). But from Iberian Peninsula and east Europe (Rivero‐montero, Gómez‐Paccard, Kondopoulou, et al., 2021), the double‐oscillation is not well recognized and the intensity curves indicate a single peak which is alike the studied Black Sea record.…”