Permeability of continental crust influenced by internal and external forcing

The permeability of continental crust is so highly variable that it is often considered to defy systematic characterization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability–depth relations) on a very large scale? Here we argue that large‐scale crustal permeability adjusts to accommodate rates of internal and external forcing. In the deeper crust, internal forcing – fluxes induced by metamorphism, magmatism, and mantle degassing – is dominant, whereas in the shallow crust, external forcing – the vigor of the hydrologic cycle – is a primary control. Crustal petrologists have long recognized the likelihood of a causal relation between fluid flux and permeability in the deep, ductile crust, where fluid pressures are typically near‐lithostatic. It is less obvious that such a relation should pertain in the relatively cool, brittle upper crust, where near‐hydrostatic fluid pressures are the norm. We use first‐order calculations and numerical modeling to explore the hypothesis that upper‐crustal permeability is influenced by the magnitude of external fluid sources, much as lower‐crustal permeability is influenced by the magnitude of internal fluid sources. We compare model‐generated permeability structures with various observations of crustal permeability.     

Glimpses Into the Dialectics of Antebellum Landscape Nucleation in Agrarian Michigan

This paper explores the transforming antebellum (ca. 1834–60) landscape, political economy, and progressive ideologies that existed at the Shepard farmstead site (20CA104) in Battle Creek, Michigan. Through this study of agrarian capitalist transformations, a picture emerges of complex dialectic interdependencies between gender, class, progressive philosophies, and the nucleated and alienating farmscape. To explore these issues, a model of agrarian transitions is developed and compared and contrasted with primary documentary, landscape, and archaeological data. This approach allows for an analysis and interpretation of transitional dynamics that have been ignored by scholars of the historical American countryside.     

Filling a Gap in the Ife–Benin Interaction Field (Thirteenth–Sixteenth Centuries AD): Excavations in Iloyi Settlement, Ijesaland

Previous archaeological studies have indicated that the Yoruba polity of Ile–Ife and the Edo polity of Benin, both in southwest Nigeria, belonged to the same sphere of sociocultural interactions before the nineteenth century AD. The spatial and temporal dimensions of this interaction sphere have not, however, been understood, because the archaeological sequences of the areas between the two polities are largely unknown. One of these intervening areas is Ijesaland. The excavations conducted in Iloyi settlement, northern Ijesaland, provide a new set of data that not only fills a gap in the Ife–Benin interaction sphere but also offers new perspectives on the process of material culture homogenization in the Yoruba–Edo region during the first half of the second millennium. Calibrated radiocarbon dates show that Iloyi was occupied during the thirteenth–sixteenth centuries AD. Using the stylistic and iconographic characteristics of ceramics and the patterns of burial and sacrificial rituals as evidence, it is demonstrated that Iloyi was a sociopolitical and cultural frontier of Ile–Ife, and that Ijesaland was part of the Ife–Benin cultural corridor. The paper strengthens the earlier suggestions that the development of a kingship institution at Ile–Ife helped to widen the interaction networks in the region, an historical process that culminated in the trend toward regional cultural homogenization between the thirteenth and sixteenth centuries.Des études archéologiques antérieures ont indiqué que l'état Yoruba de Ile-Ife et l'état Edo du Benin, les deux dans le sud ouest du Nigeria, appartenaient à la même sphére socio-culturelle avant le dix-neuvième siècle après J.-C. Pourtant, les dimensions spacio-temporelles de cette interaction n'ont pas encore été entièrement comprises, car les séquences archéologiques des régions entre les deux états restent à découvrir. L'une de ces régions est Ijesaland. Les fouilles entreprises à Iloyi, situé au nord de Ijesaland, ont divulgué l'information nouvelle sur la sphére d'interaction entre Ife et Benin ainsi que révélé des nouvelles interprétations du développement de l'homogéneisation de la culture matérielle dans la région de Yoruba-Edo durant la premiére partie du deuxiéme millénaire. Sur la base de tests de carbone, on sait que Iloyi fut occupé de treizième au seizième siècle AD. Les caractéristiques stylistiques et iconographiques de la céramique ainsi que les procédés d'enterrement et les rites de sacrifices laissent à penser que Iloyi était situé à la frontiére socio-politique et culturelle de Ile-Ife et que Ijesaland faisait partie de la zone culturelle de Ife-Benin. Ceci renforce l'hypothése que le développement d'une institution royaliste à Ile-Ife à étendu les réseaux d'interaction de cette région—un processus historique qui culmina avec la tendance à l'homogéneisation régionale culturelle du treizième au seizième siécles.