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1.
Silurian outcrops, not previously recorded from central Texas, have been identified from the Llano uplift, where they occur in collapse structures within the Lower Ordovician Honeycut Formation of the Ellenburger Group. The formation is a pinkish-gray granular limestone, contains fossils of probable Wenlock age, and is named the Starcke Limestone.  相似文献   

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Holocene sediments in Lake Washington contain a series of turbidites that were episodically deposited throughout the lake. The magnetic signatures of these terrigenous layers are temporally and areally correlatable. Large earthquakes appear to have triggered slumping on the steep basin walls and landslides in the drainage area, resulting in turbidite deposition. One prominent turbidite appears to have been deposited about 1100 years ago as the result of a large earthquake. Downcore susceptibility patterns suggest that near-simultaneous slumping occurred in at least three separate locations, two of which now contain submerged forests. Several other large earthquakes may have occurred in the last 3000 years.  相似文献   

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Rock avalanches blocked streams in the Olympic Mountains southwest of Puget Sound during the past few thousand years. Limiting radiocarbon ages indicated that three or four of six avalanches occurred from 1000 to 1300 years ago or shortly thereafter. Most of the dates were from the outer preserved rings of trees drowned behind avalanche dams. These three or four avalanches may be coeval not only with one another but also with abrupt tectonic deformation in western Washington. No rock avalanches in the Olympic Mountains are known to have resulted from storms or earthquakes during the past century. The avalanches strengthen the case that a large prehistoric earthquake occurred in the Puget Sound region.  相似文献   

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Fourteen radiocarbon dates of shells and wood from late Pleistocene sediments in northwest Washington provide evidence for correlation of the Everson interstadial with the Two Creeks interval of the midcontinent and suggest possible correlations between the Sumas and Valders stadials and between the Vashon stadial and part of the Tazewell-Cary advances.  相似文献   

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Speckle observations of Jupiter's satellite Io at a wavelength of 5 micrometers during July 1984 resolved the disk and showed emission from a hot spot in the Loki region. The hot spot contributed a flux approximately equal to 60 percent of that from the disk. Images reconstructed by means of the Knox-Thompson algorithm showed the spot moving across the disk as the satellite rotated. It was located at 301 degrees +/- 6 degrees west longitude, 10 degrees +/- 6 degrees north latitude, and had a radiance of (2.96 +/- 0.54) x 10(22) ergs sec(-1) cm(-1) sr(-1)/A where A is the area of the spot. For an assumed temperature of 400 K, the area of the source would be 11,400 square kilometers. An active "lava lake" similar to that seen by Voyager may be the source of the infrared emission.  相似文献   

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Volcanic ash from the eruption of Mount St. Helens on 18 May 1980 fell into Williams Lake in eastern Washington and was temporarily suspended at the sediment-water interface. After several months of compaction, the ash layer broke up and sank into lower density uncompacted lake sediment. Stratigraphic time displacements of several hundred years and a failure to recognize discontinuous ash layers in sediment cores are possible consequences of this process.  相似文献   

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Intertidal mud has buried extensive, well-vegetated lowlands in westernmost Washington at least six times in the past 7000 years. Each burial was probably occasioned by rapid tectonic subsidence in the range of 0.5 to 2.0 meters. Anomalous sheets of sand atop at least three of the buried lowlands suggest that tsunamis resulted from the same events that caused the subsidence. These events may have been great earthquakes from the subduction zone between the Juan de Fuca and North America plates.  相似文献   

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Eastern Market in Detroit is one of the oldest, continuously working public markets in the United States. Starting in 2006, the management changed and the market underwent a round of renovations. Since then, the Eastern Market Corporation (EMC) has worked to increase the number of stands selling value-added food at the market. Following the EMC’s lead, the new vendors sell their fare in boutique style, putting specific care in the setup of the stands and in the visual and oral narratives they use. Their presentation of food quality emphasizes craftsmanship and cultural values more than affordability or provenance. The interplay between these vendors and the EMC management point to two worlds identified by convention theory: domestic and market. The work of boutique food producers at Eastern Market manifests a composite arrangement between the domestic and market worlds where the authenticity of the products and regard for the customers are composite principles that solidify the compromise.  相似文献   

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Fossils of the late Pleistocene elk Megaloceros giganteus from Ballybetagh bog, near Dublin, Ireland, indicate that males segregated from females during winters. The segregation implies seasonal rutting and polygynous mating and is consistent with the idea that large antlers functioned for social display. Within male groups, winterkill was the chief cause of death and was highest among juveniles and small adults with small antlers. There is no evidence to support the popular conception that heavy antlers caused animals to drown or become mired.  相似文献   

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Geodetic measurements of deformation in northwestern Washington indicate that strain is accumulating at a rate close to that predicted by a model of the Cascadia subduction zone in which the plate interface underlying the continental slope and outer continental shelf is currently locked but the remainder of the interface slips continuously. Presumably this locked segment will eventually rupture in a great thrust earthquake with a down-dip extent greater than 100 kilometers.  相似文献   

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Polycyclic aromatic hydrocarbons in three sections of a dated sediment core from Buzzards Bay, Massachusetts, have been analyzed by gas chromatographic spectrometry. This historical information suggests that sedimentary polycyclic aromatic hydrocarbons, at least at this location, result primarily from the anthropogenic combustion of fossil fuels.  相似文献   

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Of the 26 well-preserved orders of benthic marine invertebrates that have originated since the beginning of the Mesozoic, 20 first appear in onshore environments. This distribution differs significantly from that shown by well-preserved genera and families, and by the 16 poorly preserved orders. These discordances suggest that the pattern of preferential onshore origination is not an artifact of preservation or collection and that the origin of higher taxa cannot be regarded as a simple extrapolation of rates and patterns at lower levels. The onshore environment fosters production or enhances survivorship of species that initiate lineages tending to accumulate suites of derived characters and that thus are ultimately afforded high taxonomic rank.  相似文献   

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