Palynological evidence for early Holocene aridity in the southern Sierra Nevada, California

Sediments of Balsam Meadow have produced a 11,000-yr pollen record from the southern Sierra Nevada of California. The Balsam Meadow diagram is divided into three zones. (1) The Artemisia zone (11,000–7000 yr B.P.) is characterized by percentages of sagebrush (Artemisia) and other nonarboreal pollen higher than can be found in the modern local vegetation. Vegetation during this interval was probably similar to the modern vegetation on the east slope of the Sierra Nevada and the climate was drier than that of today. (2) Pinus pollen exceeded 80% from 7000 to 3000 yr B.P. in the Pinus zone. The climate was moister than during the Artemisia zone. (3) Fir (Abies, Cupressaceae, and oak (Quercus) percentages increased after 3000 yr B.P. in the Abies zone as the modern vegetation at the site developed and the present cool-moist climatic regime was established. Decreased fire frequency after 1200 yr B.P. is reflected in decreased abundance of macroscopic charcoal and increased concentration of Abies magnifica and Pinus murrayana needles.     

Syn-metamorphic element transfer across lithological boundaries in the Port-aux-Basques gneiss complex, Newfoundland

Mineralogical reaction-zones developed between mafic gneiss (amphibolite) and metapelite reveal the role of cm-scale metasomatism during amphibolite-facies metamorphism of the Port-aux-Basques gneiss complex (PBGC). Ionic diffusion between mafic and pelitic layers led to the development of 1–3 cm wide, schistose, biotite + garnet-rich (Type 1) reaction-zones at the margins of mafic layers, and/or the crystallization of poikiloblastic hornblende within a garnet- and biotite-depleted (Type 2) reaction-zone up to 20 cm wide within nearby paragneiss. Garnet-biotite thermometry of the Type 1 reaction-zones indicates T_max of c. 560–645°C at a pressure of c. 6 kbar constrained by “GASP” and “GRAIL” subassemblages in the host rock.

Compared to the “unaltered” amphibolite, Type 1 reaction-zones are enriched in K, Rb and Ba, and depleted in Ca and Sr; compared to the “unaltered” metapelite, Type 2 reaction-zones show opposite trends: they are depleted in K, Rb and Ba, and enriched in Ca and Sr. This indicates that the formation of the reaction-zones involved the exchange of K, Ca and related trace elements in opposite directions across the amphibolite/paragneiss interface, and that the system was approximately closed to these components where both reaction-zones are present.     

First report of the small bird track Koreanaornis from the Cretaceous of North America: implications for avian ichnotaxonomy and paleoecology

Although body fossils of shorebirds and shorebird-like species are extremely rare from the Cretaceous, rapid increase in the discovery of bird footprint sites provides valuable alternate evidence to help fill gaps in the story of the early evolution of shorebird-like species. Newly discovered bird tracks from the Albian-Cenomanian Dakota Formation in northeastern Utah represent the first report of the ichnogenus Koreanaornis from North America and only the second report of bird tracks from this formation. These tracks are not attributable to Aquatilavipes as previously claimed. Three well-preserved trackways are described and provisionally referred to Koreanaornis cf. hamanensis (Kim). However, a review of the ichnotaxonomy of shorebird ichnites reveals that this ichnotaxon also closely resembles the Miocene ichnospecies Avipeda sirin (Vyalov). This latter comparison points to the need for a thorough evaluation of the similarity between Mesozoic and Cenozoic avian ichnotaxa, which may be over-split in some cases and under-differentiated in others.The new material helps distinguish ichnogenus Koreanaornis from the larger bird track Aquatilavipes, which is more abundant and widespread in North America. In some cases Aquatilavipes has been incorrectly used as a catch-all ichnogenus both in North America and Asia. The Dakota Formation stratigraphy at the tracksite indicates that the track makers lived in a marginal marine paleoenvironment. However, despite the widespread distribution of such facies, often replete with dinosaur tracks, the bird track record of the Dakota Formation, and the Cretaceous of the western USA remains relatively sparse in comparison with other areas such as east Asia.     

Pyrometamorphism of 19th‐century kiln artifacts from Caledonia Springs,Ontario, Canada

Marked, 19th‐century kiln bricks and rocks from Caledonia Springs (CS) have black glass coatings that can easily be mistaken for glass produced at the elusive CS glassworks (c. 1844–1846). The glass‐on‐brick material, however, is more aluminous (nearly 20% Al₂O₃) than virtually any analyzed historical glass, and the glass‐on‐rock is compositionally similar to the rock itself, which shows clear signs of having undergone extensive melting. Mineral thermometry (Cpx‐Ol, Pl‐melt) indicates that parts of the kiln‐achieved temperatures of approximately 1200–1300°C. The CS samples show that caution must be exercised when identifying seemingly obvious waste glass near defunct glassworks sites. © 2005 Wiley Periodicals, Inc.     

Basin‐scale predictive models of alluvial architecture: Constraints from the Palaeocene–Eocene,Bighorn Basin,Wyoming, USA

Basin‐scale models are required to interpret ancient continental sedimentary successions, and reduce uncertainty in assessing geological resources in basins. Recently, modern studies show distributive fluvial systems to comprise a substantial proportion of modern sedimentary basins, but their role in ancient basin fills has yet to be quantitatively documented at the basin scale. This study analysed key fluvial characteristics to construct a detailed basin‐wide model of the Palaeogene Fort Union and Willwood formations (Bighorn Basin, Wyoming), using observations from modern studies, and ancient system scale studies of distributive fluvial systems, to guide interpretations. Mapping showed these formations to be highly heterogeneous with channel‐body proportion (from 12 to 81%) and geometry types (large amalgamated bodies to isolated channels), grain size (silt to conglomerate), average channel‐body thickness (4 to 20 m) and average storey thickness (3 to 10 m) varying significantly across the basin. Distributive fluvial systems in the form of alluvial and fluvial fans in transverse configurations were recognized as well as a wide axial system, with heterogeneity in the formations being closely aligned to these interpretations. Furthermore, numerous individual depositional systems were identified within the formations (Beartooth Absaroka, Washakie, Owl Creek and axial). Predicted downstream distributive fluvial system trends (i.e. downstream decrease in channel proportion, size and grain size) were identified in the Beartooth, Absaroka and Owl Creek systems. However, predicted trends were not identified in the Washakie system where intrabasinal thrusting disturbed the sequence. Importantly, a wide axial fluvial system was identified, where reverse downstream distributive fluvial system trends were present, interpreted to be the result of the input of transverse systems of variable size. This study provides a new level of detail in the application of basin‐scale models, demonstrating their usefulness in trying to understand and predict alluvial architecture distribution and heterogeneity, with important implications for economic resources and palaeogeographic reconstructions.     

Landforms and landscape evolution in the Skardu,Shigar and Braldu Valleys,Central Karakoram

The Central Karakoram, which includes K2 in Pakistan, is one of the most rapidly rising areas on Earth and exhibits complex topography and extreme relief. Impressive valley fills and glacial landforms are present throughout the valleys. The dynamics of landscape evolution of the region are currently not well understood. Consequently, the landforms were mapped and assessed in the Skardu, Shigar, and Braldu valleys, to elucidate the spatio-temporal scale dependencies of surface processes active in the region. These valleys were examined using geomorphic field methods, remote sensing, geomorphometry, and terrestrial cosmogenic nuclides (TCNs) surface exposure dating. The glaciers in this region have oscillated considerably throughout the Late Quaternary, and four glacial stages have been recognized including at least six glacial advances. Surface processes readjusted after glacier retreat, and ubiquitous mass movements and catastrophic landsliding transported material from steep slopes to valley bottoms, while glaciofluvial meltwater and glacier outburst floods redistributed sediment down valley. Glacier geochronology and late Holocene ages of the outburst flood deposits indicate that landscape evolution has been dominated by glaciation and paraglaciation during the late Quaternary.     

Interpreting the Civil Rights Movement: Place,Memory, and Conflict

Produced over the past decade, monuments and museums dedicated to the Civil Rights movement of the 1950s and 1960s have desegregated America's memorial landscape. Tracing a broad arc across the US South, the material elements of this landscape — historic markers, monuments, parks, registered buildings, and museums — present a distinct challenge to representations of an elite, white American past. This challenge, however, is offered in a distinctly gendered manner, inasmuch as the role of women in organizing and leading the movement is obscured. Further, the historical narratives concretized at these sites are mediated by conventions associated with civil rights historiography and the tourism development industry. The result is a complex, sometimes ironic landscape. Via the narratives they embed and the crowds they attract, these landscapes are co‐constitutive with contemporary politics of representing the past in the United States. This paper offers an overview of current memorial practices and representations of the Civil Rights movement found at the country's major memorial landscapes.