Jaqueto Plinio, Trindade Ricardo I F, Terra-Nova Filipe, Feinberg Joshua M, Novello Valdir F, Stríkis Nicolás M, Schroedl Peter, Azevedo Vitor, Strauss Beck E, Cruz Francisco W, Cheng Hai, Edwards R Lawrence
Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, 05508-090, São Paulo, Brazil.
Institute for Rock Magnetism, University of Minnesota, Minneapolis, MN, 55455, USA.
Nat Commun. 2022 Mar 15;13(1):1349. doi: 10.1038/s41467-022-28972-8.
Speleothems can provide high-quality continuous records of the direction and relative paleointensity of the geomagnetic field, combining high precision dating (with U-Th method) and rapid lock-in of their detrital magnetic particles during calcite precipitation. Paleomagnetic results for a mid-to-late Holocene stalagmite from Dona Benedita Cave in central Brazil encompass ~1900 years (3410 BP to 5310 BP, constrained by 12 U-Th ages) of paleomagnetic record from 58 samples (resolution of ~33 years). This dataset reveals angular variations of less than 0.06° yr and a relatively steady paleointensity record (after calibration with geomagnetic field model) contrasting with the fast variations observed in younger speleothems from the same region under influence of the South Atlantic Anomaly. These results point to a quiescent period of the geomagnetic field during the mid-to-late Holocene in the area now comprised by the South Atlantic Anomaly, suggesting an intermittent or an absent behavior at the multi-millennial timescale.
洞穴沉积物可以提供高质量的地磁场方向和相对古强度的连续记录，它结合了高精度测年（采用铀-钍法）以及方解石沉淀过程中碎屑磁性颗粒的快速锁定。来自巴西中部多纳贝内迪塔洞穴的一个全新世中晚期石笋的古地磁结果涵盖了约1900年（公元前3410年至公元前5310年，由12个铀-钍年龄限定）的古地磁记录，该记录来自58个样本（分辨率约为33年）。该数据集显示，角度变化小于0.06°/年，并且在用地磁场模型校准后，古强度记录相对稳定，这与在南大西洋异常影响下同一地区较年轻洞穴沉积物中观察到的快速变化形成对比。这些结果表明，在现在由南大西洋异常所涵盖的区域，全新世中晚期地磁场处于静止期，这表明在地磁场千年尺度上存在间歇性或缺失行为。
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