Constraining the long-term variability and average of the Earth’s magnetic field strength is fundamental to understanding the characteristics and behavior of the geomagnetic field. Questions remain about the strength of the average field, and the rela-tionship between strength and reversal frequency. The dispersion of data from key timeintervals reflects the complexity in obtaining absolute paleointensity values. Here, we focus on the Cretaceous Normal Superchron (CNS; 121-84 Ma), during which there were no reversals. We present new results from 42 submarine basaltic glass (SBG) sites collected on the Nicoya Peninsula and Murcielago Islands, Costa Rica and new and revised 40Ar/39Ar ages along with biostratigraphic age constraints from previous studies that indicate ages from 141 to 112 Ma. One site with a 40Ar/39Ar age of 135+\-1.5Ma (2σ) gave a reliable intensity result of 34+\-μT (equivalent to a paleomagnetic dipole moment, PDM, value of 88+\-20 ZAm2), while three sites between 121 and 112 vary from 21+\- to 34+\-4 μT (53+\-3 to 87+\-10 ZAm2) spanning the onset of the CNS. These results from the CNS are all higher than the long-term average of ~42 ZAm2 and similar to data from Suhongtu (46-53 ZAm2) and the Troodos Ophiolite (81 ZAm2, reinterpreted, using the same criteria of this study). Together with the reinterpreted data, the new Costa Rica results suggest thatthe strength of the geomagnetic field was about the same before and after the onset ofthe CNS. Therefore, the data do not support a strict correlation between polarity interval length and the strength of the magnetic field.

A fundamental assumption in paleomagnetism is that a geocentric axial dipole (GAD) geomagnetic field structure extends to the ancient field. Global paleodirectional compilations that span 0 - 10 Myr support a GAD dominated field structure with minor non-GAD contributions, however, the paleointensity data over the same period do not. In a GAD field, higher latitudes should preserve higher intensity, but the current database suggests that intensities are independent of latitude. To determine whether the seemingly “low’ intensities from Antarctica reflect the ancient field, rather than low quality data or inadequate temporal sampling, we have conducted a new study of the paleomagnetic field in Antarctica. This study focuses on the paleomagnetic field structure over the Late Neogene. We combine and re-analyze new and published paleodirectional and paleointensity results from the Erebus volcanic province to recover directions from 107 sites that were both thermally and AF demagnetized and then subjected to a set of strict selection criteria and 28 paleointensity estimates from specimens that underwent the IZZI modified Thellier-Thellier experiment and were also subjected to a strict set of selection criteria. The paleopole (205.6$^{\circ}$, 87.1$^{\circ}$) and $\alpha_{95}$ (5.5$^\circ)$ recovered from our paleodirectional study supports the GAD hypothesis and the scatter of the virtual geomagnetic poles is within the uncertainty of that predicted by TK03 paleosecular variation model. Our time averaged field strength estimate, 33.01 $\mu$T $\pm$ 2.59 $\mu$T, is significantly lower than that expected for a GAD field estimated from the present field, but consistent with the long term average field.