Syn-orogenic detachment faults exhuming extensional shear zones are ever-present features in orogenic settings on Earth. Kinematic and fluid-flow models for brittle detachment faults paired with crystal-plastic shear zones continue to evolve alongside new data and techniques. Evidence for meteoric water infiltrating the frictional-viscous transition zone in detachment-related shear zones has survived revisions of these models, but the extent and influence of meteoric-hydrothermal circulation is not fully understood. Kinematic analysis and delta H-2 values of syn-kinematic micas from nine transects through the <6-0 Ma footwall shear zone of the Cordillera Blanca Detachment in the Peruvian Andes explore patterns of fluid flow during shear zone initiation and evolution at a previously unattained resolution. delta H-2 values reveal a pervasive pattern of meteoric water infiltration into the frictional-viscous transition zone across the detachment. Gradients in delta H-2 values reveal that fluid infiltration follows patterns of anataxial magmatism and the distribution of syn-kinematic fractures within and across the shear zone. Cumulatively, a three-dimensional assessment of the footwall shear zone of the Cordillera Blanca Detachment indicates that fluid infiltration into the frictional-viscous transition zone is spatially heterogeneous and correlated with the style of shear zone initiation and strain localization. Observed variability of fluid-rock interaction across the Cordillera Blanca Detachment highlights the importance of assessing for spatial heterogeneity when quantifying or qualifying fluid activity in meteoric-hydrothermally modified detachment faults.
Shear zone systems exposed in the crystalline rocks of Colorado record Proterozoic deformation episodes documenting strain partitioning, reactivation and the progressive tectonic evolution of SW Laurentia. These structures, and their equivalents throughout the southwestern USA, provide insight into the structural evolution of the North American craton, and inform tectonic models for an active, but challenging to decipher period in Earth's history. NE-SW-trending mylonitic bands record regional fold formation and establishment of sub-vertical D-1/D-2 shear zones occurred during the successive c. 1720-1600 Ma Yavapai and Mazatzal orogenies, and D-3/D-4 reactivation of these structures during the c. 1450-1300 Ma Picuris Orogeny. The shallowly dipping Slide Lake Shear Zone (SLSZ), in Colorado's Sawatch Range, is adjacent to the steeply dipping Homestake Shear Zone (HSZ), allowing for comparison between high- and low-angle faulting in mid-crustal positions associated with the long-lived Laurentian orogenic margin throughout the Proterozoic. Both structures record similar deformational conditions and bulk NW-SE-verging kinematics. Newly obtained in situ electron microprobe monazite U-Th-Pb geochronology and trace element geochemistry constrain the timing and nature of SLSZ activity, allowing direct comparison with established HSZ activity. Core domains in a steeply dipping segment of the SLSZ record mineral growth during the Yavapai Orogeny (D-1) at c. 1700 +/- 14 Ma, and support continued SLSZ activation during the Mazatzal Orogeny (D-2). Low-angle segments preserve deformation associated with the Mesoproterozoic Picuris Orogeny (D-3/D-4) at c. 1450-1300 Ma. The age progression of the SLSZ parallels the structural evolution of the HSZ, indicating that sub-horizontal, transtensional, D-3/D-4 slip on the SLSZ was coeval with sub-vertical, transpressional, D-3/D-4 slip on the HSZ. Cumulatively, the existing structural and newly established temporal history of the HSZ-SLSZ system is interpreted to indicate that oblique extensional and compressional strain were competing in the middle crust within the Laurentian interior during the Picuris Orogeny, lending credence to models of plateau-style crustal thickening and collapse during this event.
Efforts to counter Christian nationalism focus on the power of ideas-that Christian nationalism is historically inaccurate, religiously heretical, or even fascist. Those efforts build upon a vast research agenda on Christian nationalism in the social sciences to argue, at least implicitly, that a Christian nationalist worldview rejects religious, racial, and political pluralism in favor of a (white) Christian-centric goal for the United States. But they may be wrong on at least one account. In a January 2024 survey of 1,500 American Christians, we piloted "anti-Christian nationalism" measures, expecting to find a robust negative relationship with established measures of Christian nationalism. Instead, we find that many Christian nationalists already hold pluralist ideas in their heads. We then explore whether anti-Christian nationalism can work to counter, moderate, or align attitudes with Christian nationalism on political tolerance. We find that Christian nationalism often overrules anti-Christian nationalism, especially when the threat is high.
I examine the two careers of British colonial administrator and Pacific historian Henry Evans Maude (1906-2006) to illuminate continuities between the logic of late-imperialism and foundational modes of Pacific historiography. Maude worked as a colonial servant in the Gilbert and Ellice Islands Colony from 1929, where he instigated two coerced resettlement schemes. In 1957, he joined the Department of Pacific History at the Australian National University, where he championed new modes of history writing tailored to the era of decolonisation-especially "island-centred" ethnohistory and "participant history." I argue that Maude's visions of empire and of the past were deeply linked, and that imbrications between the two informed the practices of an emerging professional Pacific history during the 1960s. Modes of history-writing that would come to be understood as critical of older imperial histories, or even as anti-colonial, had their origins in colonial structures. At the same time, both of Maude's careers evinced a colonial notion of futurity; he understood himself as a benevolent expert able to guide Indigenous peoples into eventual independence.
