Modern sedimentary processes in the Santa Monica,California continental margin: sediment accumulation,mixing and budget     

Alexander CR  Venherm C 《Marine environmental research》2003,56(1-2):177-204

Sediment input to SMB appears to be associated with at least two point sources on the shelf, with Malibu Creek and the Hyperion sewage outfall being the most significant. Sediment contributions are sufficient to support apparent mass accumulation rates near these sources up to approximately 1.8 g/cm(2) year, which with distance decrease to approximately 0.5 g/cm(2) year near the shelf break (approximately 80-100 m water depth). Sequestering of material on the shelf and decreasing sediment supply to the slope is evident as rates decrease between 100 and 200 m water depths to less than 0.2 g/cm(2) year. Below 100-200 m water depth, rates are relatively slow throughout a broad region of the slope (0.07-0.14 g/cm(2) year). These slower rates are in general agreement with rates determined on the flanks of the California Borderland basins. Sediment texture fines from approximately 3.5 phi to approximately 7 phi with distance offshore. Texture does not exhibit significant changes from surficial values with depth in the seabed at any given site or between sites on the slope. This similarity in rates and downcore texture over such a broad extent suggests that hemiplegic sedimentation is the dominant mechanism of sediment delivery in water depths >200 m. Seabed distributions of radionuclides suggest that apparent accumulation rates in SMB may be twice the actual accumulation rates. A sediment budget documents that over the past century at least, SMB has served as a sink for 50-100% of the natural and anthropogenic inputs to the coastal ocean.  相似文献   

Localised strain in fissured clays: the combined effect of fissure orientation and confining pressure     

Tudisco  Erika  Vitone  Claudia  Mondello  Cristina  Viggiani  Gioacchino  Athanasopoulos  Stefanos  Hall  Stephen A.  Cotecchia  Federica 《Acta Geotechnica》2022,17(5):1585-1603

Acta Geotechnica - This paper reports the main results of an experimental study on the mechanics of intensely fissured natural clays, extending our previous studies on scaly clay from Santa Croce...  相似文献   

Deep low-salinity groundwater in sedimentary basins: petrophysical methods from a case study in Somalia     

Quiroga  Elizabeth  Bertoni  Claudia  Ruden  Fridtjov 《Hydrogeology Journal》2023,31(3):685-705

Oil and gas exploration data for the Northern Somalia and Horn of Africa region have been utilised for deep freshwater resources exploration. This unique geophysical and petrophysical dataset is integrated into a regional hydrogeological study and it allows for targeting of unmapped and unknown deep aquifers that would otherwise be beyond the conventional reach of the groundwater sector. The database includes open-hole well logging surveys (resistivity, gamma ray, and spontaneous potential), mud logging and drill stem test (DST) data. The results from the data analysis are combined with the geological interpretation to assess the freshwater potential of each mapped hydrostratigraphic unit in the region. The results highlight the presence of several previously unknown deep low-to-medium salinity (<9  g/L total dissolved solids (TDS)) aquifers within the Jurassic to Eocene units, including the Adigrat, Hamanlei, Gabredarre, Gumburo, Jessoma, and Auradu formations. With tested intervals of water containing less than 3.8 g/L total dissolved solids, the Auradu, Jessoma, and Gumburo formations are the most promising deep freshwater aquifers. Additional results on the analysis of groundwater parameters, such as hydraulic head, provide the basis for further groundwater modelling. The results show that the method has good potential, in particular for use in drought-stricken areas of arid regions. Ultimately, the results from this region have global significance, as the method can provide a new means of boosting fresh groundwater resources in water-poor regions, and supporting sustainable development and utilization of the resources in the medium and long term.

  相似文献   

Slope instability processes in intensely fissured clays: case histories in the Southern Apennines     

Federica Cotecchia  Claudia Vitone  Francesca Santaloia  Giuseppe Pedone  Osvaldo Bottiglieri 《Landslides》2015,12(5):877-893

  相似文献   

Microvertebrates from the basal Rhaetian Bone Bed (latest Triassic) at Aust Cliff,S.W. England     

Samuel R.R. Cross  Nikola Ivanovski  Christopher J. Duffin  Claudia Hildebrandt  Adam Parker  Michael J. Benton 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(5):635-653

  相似文献   

The response of drainage basins to the late Quaternary tectonics in the Sicilian side of the Messina Strait (NE Sicily)     

Pierpaolo Guarnieri  Claudia Pirrotta 《Geomorphology》2008,95(3-4):260-273

Despite more than 40 yr of research attributing temporal changes in streambank erosion rates to subaerial processes, little quantitative information is available on the relationships between streambank erodibility (k_d) and critical shear stress (τ_c) and the environmental conditions and processes that enhance streambank erosion potential. The study goal was to evaluate temporal changes in k_d and τ_c from soil desiccation and freeze–thaw cycling. Soil erodibility and τ_c were measured monthly in situ using a multiangle, submerged jet test device. Soil moisture, temperature, and bulk density as well as precipitation, air temperature, and stream stage were measured continuously to determine changes in soil moisture content and state. Pairwise Mann–Whitney tests indicted k_d was 2.9 and 2.1 times higher (p < 0.0065) during the winter (December–March) than in the spring/fall (April–May, October–November) and the summer (June–September), respectively. Regression analysis showed 80% of the variability in k_d was explained by freeze–thaw cycling alone. Study results also indicated soil bulk density was highly influenced by winter weather conditions (r² = 0.86): bulk density was inversely related to both soil water content and freeze–thaw cycling. Results showed that significant changes in the resistance of streambank soils to fluvial erosion can be attributed to subaerial processes. Water resource professionals should consider the implications of increased soil erodibility during the winter in the development of channel erosion models and stream restoration designs.  相似文献   

Morphologic resilience and depositional processes due to the rapid evolution of the submerged Sciara del Fuoco (Stromboli Island) after the December 2002 submarine slide and tsunami   总被引：1，自引：0，他引：1  

Francesco L. Chiocci  Claudia Romagnoli  Alessandro Bosman   《Geomorphology》2008,100(3-4):356-365

In order to monitor the Stromboli submarine slope after the 30 December 2002 landslide and tsunami, repeated marine surveys were carried out offshore of Sciara del Fuoco. The morphological changes and depositional processes that brought to the gradual filling of the slide scar have been studied in detail. Thirteen surveys in a period of little more than 4 years provided a unique opportunity to reconstruct the morpho-sedimentary evolution of the submarine slope and its recovery after the mass-wasting event. The scar has been progressively filled with lava and volcanoclastic debris; in the first month and a half, the filling rate was very high due to the entrance of lava flows into the sea and to the morphological readjustment of the slope; in the following months/years the rate dramatically decreased when the eruptive vents moved upwards and the eruption finally stopped. After 4 years (February 2007) more than 40% of the scar was already filled. In early 2007, a new eruption occurred and a lava delta was constructed in the 2002 scar, influencing the natural readjustment of the slope; therefore, our reconstruction only encompasses the period between the 2002 and 2007 eruptions.The swath bathymetry reconstruction of geometry and volume of scar filling during the period 2002–2007 evidenced a punctuated and fast shift of depocenters and debris emplacement through avalanching processes. This process quickly obliterated the features produced by the 2002 tsunamigenic landslide so that a major question about the preservation potential of mass-wasting features on active volcanic flanks emerges.  相似文献   

Hydrocarbons in sediments of a chronically contaminated bay: the challenge of source assignment   总被引：2，自引：0，他引：2  

Wagener Ade L  Meniconi Mde F  Hamacher C  Farias CO  da Silva GC  Gabardo IT  Scofield Ade L 《Marine pollution bulletin》2012,64(2):284-294

Aliphatic hydrocarbons and 39 PAH (parental and alkylated homologs) determined in ca. 100 sediment samples from the Guanabara Bay, Rio de Janeiro, were evaluated for source discrimination using new approaches. Concentrations of total PAH were in the range of 96-135,000 μg kg(-1) similar to other coastal urbanized embayment. Traditional diagnostic ratios were not as efficient PAH source indicators, e.g. biomass combustion was assigned as the major source of the pyrolytic PAH although the hydrographic basin is highly industrialized and urbanized. It is proved petrogenic imprint cannot be detected if only the 16 USEPA PAH are determined. The high production in the eutrophic system is not apparent in the aliphatic fraction dominated by land derived n-alkanes due to the effectiveness of microbial degradation. The present work demonstrates the complexity of hydrocarbon forensics when applied to chronically contaminated environments.  相似文献   

Magnetic studies and scanning electron microscopy — X-ray energy dispersive spectroscopy analyses of road sediments,soils and vehicle-derived emissions   总被引：1，自引：0，他引：1  

Marcos A. E. Chaparro  Débora C. Marié  Claudia S.G. Gogorza  Ana Navas  Ana M. Sinito 《Studia Geophysica et Geodaetica》2010,54(4):633-650

Human health and environmental problems related to particulate matter emission from vehicles has become a topic of research interest in recent years. These airborne particles can not only be directly inhaled, but are also present as suspended and deposited particles on paved areas and roadside soils. Here we report on magnetic studies, scanning electron microscopy (SEM), X-ray energy dispersive spectroscopy (EDS) and chemical analyses of vehicle-derived particles collected from both primary sources and as deposited particles on roads and soils. Preliminary results, recently published by the authors, have revealed that the magnetic signal of such particles is controlled by a magnetite-like phase with magnetic grain size ranging between 0.1 μm and 5 μm. An enrichment of some trace elements: Ba, Cr, Cu, Zn and Pb was also found. In this study we focus on SEM and EDS complementary studies of magnetic extracts. SEM observations showed small individual particles or spherulites, small aggregates in the form of chains or clusters, large aggregates of spherules, flake-like bodies, fibre-like particles, sheet-like particles, irregular debris and large particle agglomerates, i.e. a wide variety of shapes. Grain size distribution is also in agreement with magnetic grain size estimations. Additionally the following elements: C, O, Na, Mg, Al, Si, S, K, Ca, V, Ba, Ti, Cr, Mn, Fe, Cu, Zn and Pb were detected by EDS analysis.  相似文献   

Geoelectrical investigations in the Cheb Basin/W-Bohemia: An approach to evaluate the near-surface conductivity structure     

Christina Flechsig  Tobias Fabig  Carsten Rücker  Claudia Schütze 《Studia Geophysica et Geodaetica》2010,54(3):443-463

The Cheb Basin, located in the western Eger (Ohře) Rift, is part of the European Cenozoic Rift system. Although presently non-volcanic, it is the most active area within the European Rift with signs of recent geodynamic activity like emanations of mantle derived CO₂, and the repeated occurrence of swarm earthquakes, which are common features in active volcanic regions. It is assumed that the fluids, uprising in permeable channels, play a key role for the genesis of these earthquake swarms.  相似文献