Structure, Construction, and Emplacement of the Late Cretaceous Sonora Pass Intrusive Suite: Central Sierra Nevada Batholith, California

The \u3e1000 km2, ~95-88 Ma Sonora Pass intrusive suite is the oldest and most northern of the four voluminous, normally-zoned Late Cretaceous suites of the Sierra Nevada batholith. It consists of the older, marginal, equigranular Kinney Lakes hornblende-biotite granodiorite and the inner, porphyritic to megacrystic Topaz Lake biotite granodiorite. The suite intruded the ~109 Ma Bummers Flat biotite granodiorite, Jurassic diorites, and Pre-Cambrian to Cambrian metasedimentary rocks of the Snow Lake pendant. The Topaz Lake granodiorite records evidence of the development of a sizable magma chamber. The Bummers Flat and Kinney Lakes granodiorites were likely constructed by many increments, were capable of flow and disaggregation of host and co-magmatic mafic rocks, are marked by widespread schlieren, and may have not formed a single magma chamber. Accommodation of magmas was facilitated by multiple material transfer processes; stoping was the best documented process, followed by minor ductile flow and magmatic wedging of the Kinney Lakes granodiorite. There is no direct evidence for transfer processes during emplacement of the Topaz Lake granodiorite. Magmatic foliation within the study area records regional tectonic strain and complex internal magmatic processes. Solid-state structures including steep ductile shear zones, foliations, and lineations occur within the Bummers Flat granodiorite. One of these structures, the Toe Jam Lake shear zone, may extend for 10s of km, likely formed during ENE-WSW shortening, and probably predated the Sonora Pass intrusive suite

Parameterizing Quasiperiodicity: Generalized Poisson Summation and Its Application to Modified-Fibonacci Antenna Arrays

The fairly recent discovery of "quasicrystals", whose X-ray diffraction patterns reveal certain peculiar features which do not conform with spatial periodicity, has motivated studies of the wave-dynamical implications of "aperiodic order". Within the context of the radiation properties of antenna arrays, an instructive novel (canonical) example of wave interactions with quasiperiodic order is illustrated here for one-dimensional (1-D) array configurations based on the "modified-Fibonacci" sequence, with utilization of a two-scale generalization of the standard Poisson summation formula for periodic arrays. This allows for a "quasi-Floquet" analytic parameterization of the radiated field, which provides instructive insights into some of the basic wave mechanisms associated with quasiperiodic order, highlighting similarities and differences with the periodic case. Examples are shown for quasiperiodic infinite and spatially-truncated arrays, with brief discussion of computational issues and potential applications.Comment: 29 pages, 10 figures. To be published in IEEE Trans. Antennas Propagat., vol. 53, No. 6, June 200

Headwaters are critical reservoirs of microbial diversity for fluvial networks

Streams and rivers form conspicuous networks on the Earth and are among nature's most effective integrators. Their dendritic structure reaches into the terrestrial landscape and accumulates water and sediment en route from abundant headwater streams to a single river mouth. The prevailing view over the last decades has been that biological diversity also accumulates downstream. Here, we show that this pattern does not hold for fluvial biofilms, which are the dominant mode of microbial life in streams and rivers and which fulfil critical ecosystem functions therein. Using 454 pyrosequencing on benthic biofilms from 114 streams, we found that microbial diversity decreased from headwaters downstream and especially at confluences. We suggest that the local environment and biotic interactions may modify the influence of metacommunity connectivity on local biofilm biodiversity throughout the network. In addition, there was a high degree of variability in species composition among headwater streams that could not be explained by geographical distance between catchments. This suggests that the dendritic nature of fluvial networks constrains the distributional patterns of microbial diversity similar to that of animals. Our observations highlight the contributions that headwaters make in the maintenance of microbial biodiversity in fluvial networks