Possible lava tube system in a hummocky lava flow at Daund,western Deccan Volcanic Province,India     

Raymond A. Duraiswami  Ninad R. Bondre  Gauri Dole 《Journal of Earth System Science》2004,113(4):819-829

A hummocky flow characterised by the presence of toes, lobes, tumuli and possible lava tube system is exposed near Daund, western Deccan Volcanic Province, India. The lava tube system is exposed as several exhumed outcrops and is composed of complex branching and discontinuous segments. The roof of the lava tube has collapsed but original lava tube walls and fragments of the tube roof are seen at numerous places along the tube. At some places the tube walls exhibit a single layer of lava lining, whereas, at other places it shows an additional layer characterised by smooth surface and polygonal cracks. The presence of a branching and meandering lava tube system in the Daund flow, which represents the terminal parts of Thakurwadi Formation, shows that the hummocky flow developed at a low local volumetric flow rate. This tube system developed in the thinner parts of the flow sequence; and tumuli developed in areas where the tube clogged temporarily in the sluggish flow.  相似文献   

A palynological biozonation for the Maastrichtian Stage (Upper Cretaceous) of South Carolina, USA     

Raymond A. Christopher  David C. Prowell 《Cretaceous Research》2002,23(6):639

Three palynological biozones are proposed for the Maastrichtian Stage of South Carolina. In ascending stratigraphic order, the biozones are the Carolinapollis triangularis (Ct) Interval Biozone, the Holkopollenites chemardensis (Hc) Interval Biozone, and the Sparganiaceaepollenites uniformis (Su) Interval Biozone. Integration of the biostratigraphy with lithologic and geophysical log data suggests that within the study area, the upper and lower boundaries of each zone are bounded by regional unconformities, and that a three-fold subdivision of the Maastrichtian Stage is warranted. The biozonation is based on the analysis of 114 samples from 24 subsurface and three outcrop sections from the Coastal Plain of South Carolina; samples from an additional seven subsurface and 18 outcrop sections from North Carolina and Georgia were examined to evaluate the geographic extent of the biozones. One new genus and five new species of pollen are described, and emendations are presented for two genera and one species of pollen.  相似文献   

The effects of seasonal variability and weather on microbial fecal pollution and enteric pathogens in a subtropical estuary     

Erin K. Lipp  Raymond Kurz  Robert Vincent  Cesar Rodriguez-Palacios  Samuel R. Farrah  Joan B. Rose 《Estuaries and Coasts》2001,24(2):266-276

The Charlotte Harbor estuary in southwest Florida was sampled monthly for one year at twelve stations, in the lower reaches of the Myakka and Peace Rivers. The objectives of the study were to address the distribution and seasonal changes in microbial indicators and human pathogen levels in Charlotte Harbor shellfish and recreational waters, and to determine those factors that may be important in the transport and survival of pathogens. Monthly water samples and quarterly sediment samples were analyzed for fecal coliform bacteria, enterococci,Clostridium perfringens, and coliphage. Quarterly samples also were analyzed for the enteric human pathogens,Cryptosporidium spp.,Giardia spp., and enteroviruses. Fecal indicator organisms were generally concentrated in areas of low salinity and high densities of septic systems; however, pollution became widespread during wet weather in, the late fall and winter of 1997–1998, coincident with a strong El Nino event. Between, December 1997 and February 1998, enteroviruses were detected at 75% of the sampling stations; none were detected in other months. Enteric protozoa were detected infrequently and were not related to seasonal influences. Fecal indicators and enteroviruses were each significantly associated with rainfall, streamflow, and temperature. Regression models suggest that temperature and rainfall can predict the occurrence of enteroviruses in 93.7% of the cases. Based on findings in this watershed, factors such as variability in precipitation, streamflow, and temperature show promise in modeling and forecasting periods of poor coastal water quality.  相似文献   

Effects of Waste-Water Irrigation on Aqueous Geochemistry Near Paris, Texas     

Dante J. Tedaldi  Raymond C. Loehr 《Ground water》1992,30(5):709-719

  相似文献   

The explosive volcanic eruption signal in northern hemisphere continental temperature records   总被引：3，自引：0，他引：3  

Raymond S. Bradley 《Climatic change》1988,12(3):221-243

Several catalogs of explosive volcanic eruptions are reviewed and their limitations assessed. A new, homogeneous set of high quality gridded temperature data for continental regions of the northern hemisphere is then examined in relation to the timing of major explosive eruptions. Several of the largest eruptions are associated with significant drops in summer and fall temperatures, whereas pronounced negative anomalies in winter and spring temperatures are generally unrelated to volcanic activity. The effect of explosive eruptions on temperature decreases latitudinally away from the location of the eruption. High latitude eruptions have the greatest impact on high and mid latitudes; low latitude eruptions mainly influence low and mid latitudes. Temperature depressions following major eruptions are very abrupt but short-lived (1 to 3 months) decreasing in magnitude over the course of the subsequent 1 to 3 years. Generally any signal is indistinguishable from noise after 12 months but a small recurrent drop in temperature is evident about 12 to 24 months after the initial anomaly. Considering all known eruptions which injected material into the stratosphere over the last 100 years (except the 5 largest eruptions) a significant temperature depression is observed over the continents only in the month immediately following the eruption. There is no evidence that large eruptions over the last 100 years have had a significant effect on low frequency temperature changes.  相似文献   

Formulation of the thermal internal boundary layer in a mesoscale model. II. Simulations with a level-2.5 turbulence closure     

Raymond W. Arritt  William L. Physick 《Boundary-Layer Meteorology》1989,49(4):411-416

Physick et al. (1989) have discussed some difficulties associated with simulation of the sea-breeze thermal internal boundary layer (TIBL), using a numerical model containing a profile exchange coefficient formulation developed by O'Brien (1970). They suggested that a closure scheme based on a prediction of turbulent kinetic energy (TKE) would be able to resolve the TIBL better than a profile scheme. This Research Note reports simulations of the case discussed in I, using a numerical model with a TKE-based turbulence closure.  相似文献   

The match game: New stratigraphic correlation algorithms   总被引：1，自引：0，他引：1  

Michael S. Waterman  Robert Raymond Jr. 《Mathematical Geology》1987,19(2):109-127

New algorithms for automatic correlation of geologic strata are introduced. The algorithms are extensions of the Smith and Waterman (1980) dynamic programming technique and include several features that greatly increase the utility for sedimentary sequences. Gaps in correlation (unconformities) caused by local nondeposition or eroded strata can include in a single event several strata. Furthermore, these gaps can be weighted as a single event, rather than as the sum of gap events for each strata. In addition, one or several adjacent strata in a second column can be correlated (matched) with one or several strata in a second column. Deletions within one of these multiple matches are also possible. The new algorithms include the method of minimum distance and the method of maximum similarity. Within this context, a similarity algorithm is given to locate and correlate the best matching segments or intervals from each stratigraphic column. All correlations within a preset distance of the optimum likewise can be produced for any of these algorithms. An example of specific assignments of these weight functions is given for correlation of well logs from the San Juan Basin.  相似文献   

Tectonic erosion at the front of the Japan Trench convergent margin   总被引：1，自引：0，他引：1  

Roland Von Huene  Raymond Culotta 《Tectonophysics》1989,160(1-4):75-90

The imaging of a multichannel seismic record was improved by reprocessing using pre-stack techniques. The reprocessed record shows structures that indicate tectonic erosion and gravity collapse at the front of the Japan Trench margin. Much of the lower slope appears to be underlain by a detached, coherent block of continental crust. The lower slope has failed by mass wasting and the resulting apron of slump debris at the base of the slope has become involved in thrust faulting at the front of the subduction zone. Slumping continues as long as debris is removed from the front of the margin by subduction, and the apron cannot build up sufficiently to stabilize the failing lower slope. Truncated beds at the base of the upper plate indicate subcrustal erosion as well, this probably being the main cause of massive subsidence of the margin. Subsidence was the cause of oversteepening, destabilization and subsequent gravity collapse of the leading edge of the upper plate.  相似文献   

Amorce de la Sédimentation Synorogénique dans les PyrénéesVarisques. Données Chronologiques; Implications Paléogéographiques     

Professeur Dr. Raymond Mirouse  Gilbert Barrouquère  Gilbert Bessière  Jean-Jacques Delvolvé  Marie-France Perret 《International Journal of Earth Sciences》1983,72(1):253-281

Conodont associations and recent macrofaunal discoveries, allow us to date the beginning of detrital deposits going with the Variscan uplift in the Pyrenean marine basins during the Lower Carboniferous. Thus, the establishing of synorogenic conditions seems to have progressed from the East to the West; there appears the picture of a kind of north-Pyrenean axis already individualized in the wide Cantabrico-Pyrenean foreland.  相似文献   

Statistical analysis of travel-time anomalies     

David D. Jackson  Raymond A. Ergas 《Physics of the Earth and Planetary Interiors》1979,18(4):303-308

We develop a method of testing local travel-time data for the presence of velocity anomalies. Using the theory of statistical hypothesis testing, we compare residual errors from two different models, one normal and one containing an anomaly. The probability of a false rejection is estimated, and is used to accept or reject the normal hypothesis. Application of the method to aftershocks of the 1975 Oroville, California earthquake illustrates the problems that are caused by incomplete knowledge of the local time-independent structure.  相似文献