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The Valanginian period is marked by significant events, including the earliest perturbations of the global carbon cycle and the initial emplacement of large igneous provinces on land. Recent years have seen the ratification of the global boundary stratotype sections and points (GSSPs) for the Valanginian and Hauterivian stages, reflecting increased stratigraphic and palaeoenvironmental research on the Valanginian. However, paleoceanographic information remains limited for the Early Cretaceous Panthalassa, which was the largest ocean during early Cretaceous. In Northeast Japan, Lower Cretaceous marine sequences, formed in the northwest region of Panthalassa along the northeastern margin of Eurasia, are exposed intermittently. These sequences have been challenging to date accurately due to the limited availability of age-diagnostic fossils. We establish new global stratigraphic correlations using U–Pb zircon ages from tuffs and carbon isotope stratigraphy for the Lower Cretaceous formations of the Karakuwa and Oshima Groups in Northeast Japan. We identify the Berriasian/Valanginian boundary and the Weissert Event within these strata. In addition, we recognize a potential stratigraphic level for the Valanginian/Hauterivian boundary. Notably, the Weissert Event interval within these sequences does not exhibit the significant lithological changes, such as the intercalation of black shales or a decrease in bioturbation observed elsewhere . By contrast, observed lithological changes are indicative of regional tectonics, including large-scale sinistral strike-slip movement and subsequent ridge subduction along the active continental margin of Eurasia. 

The Leucite Hills Volcanic Field, southwest Wyoming comprises two dozen volcanic features including necks, flows, dikes, and plugs. It has been the focus of many petrologic studies as its volcanic and shallow intrusive rocks are one of the only surficial manifestations of ultrapotassic lamproite. We build on paleomagnetic findings of Sheriff and Shive (1980) by providing further paleomagnetic data from the Boars Tusk dike and Black Rock flows. We also characterize the magnetic mineral assemblage of these lamproites. Principal component analysis of alternating field (AF) and thermal demagnetization data indicate that the dike and breccias of Boars Tusk record a reversed magnetic polarity and the Black Rock lava records a normal polarity, both consistent with previous findings. This recording is typically carried by minerals with coercivities >15 mT and susceptibility measurements indicate magnetite, maghemite, and titanomagnetite as likely magnetic carriers. AF and thermal demagnetization experiments evince secondary magnetizations held by lower coercivity grains, likely caused by lightning strikes. 40Ar/39Ar incremental heating experiments from Boars Tusk and Black Rock give plateau ages of ∼ 2500 ka and ∼ 900 ka, respectively. Recent advances in the chronology of geomagnetic field reversals and excursions during the Quaternary permit integration of the Boars Tusk dike into the lower Matuyama chron, whereas the Black Rock lavas most probably record the Kamikatsura excursion. Notably, Black Rock records high inclinations that suggest the short-lived excursion achieved a full geomagnetic reversal, something not observed at other localities recording the Kamikatsura excursion. The Leucite Hills offer further opportunities to refine the Quaternary geomagnetic instability time scale (GITS), and to improve understanding of the eruptive and geomorphic evolution of this unusual volcanism.