Cirrus Cloud Macrophysical and Optical Properties over North China from CALIOP Measurements   总被引：1，自引：0，他引：1  

MIN Min  WANG Pucai  James R. CAMPBELL  ZONG Xuemei  XIA Junrong 《大气科学进展》2011,28(3):653-664

Two years of mid-latitude cirrus cloud macrophysical and optical properties over North China are described from Earth-orbiting Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP) satellite measurements. Global cloud climatological studies based on active remote sensing data sets benefit from more accurate resolution of vertical structure and more reliable detection of optically thin layers.The mean values for cirrus cases over North China are 0.19±0.18 for infrared emittance,0.41±0.68 for visible optical depth, 0.26±0.12 for integrated depolarization ratio,and 0.72±0.22 for integrated color ratio.When studied using reasonable assumptions for the relationship between extinction and ice crystal backscatter coefficients,our results show that most of the cirrus clouds profiled using the 0.532μm channel data stream correspond with an optical depth of less than 1.0.The dependence of cirrus cloud properties on cirrus cloud mid-cloud temperature and geometry thickness are generally similar to the results derived from the ground-based lidar, which are mainly impacted by the adiabatic process on the ice cloud content.However,the differences in macrophysical parameter variability indicate the limits of spaceborne-lidar and dissimilarities in regional climate variability and the nature and source of cloud nuclei in different geographical regions.  相似文献   

Petrology of the G and H Chromitite Zones in the Mountain View Area of the Stillwater Complex, Montana   总被引：2，自引：2，他引：2  

CAMPBELL  IAN H.; MURCK  BARBARA W. 《Journal of Petrology》1993,34(2):291-316

The Ultramafic Series of the Stillwater Complex in the MountainView area of the intrusion consists of 17 cyclic units thathave been numbered stratigraphically. A typical unit has olivinecumulates at the base, olivine–bronzite cumulates at intermediatelevels, and bronzite cumulates at the top. Most cyclic unitsalso have chromite-rich layers near their base, the thickestbeing the G and H chromitite zones in units 10 and 11. The Gand H zones are each separated from the top of the underlyingcyclic unit by 1–3 m of coarse-grained olivine cumulateand pegmatite; and they are both succeeded by thinner chromititezones, respectively called the hanging wall G (HWG) and thehanging wall H (HWH) zones, situated {small tilde}20 m and 5m above them. The G and H chromitite zones feature rhythmicsequences of thin layers that tend to progress upward from massivechromitite through chromite–olivine cumulate to olivine–chromitecumulate (the last with the minerals in approximately cotecticproportions of about 98:2). In cyclic units 10 and 11, variationsof Mg/Fe in the olivine and bronzite, and of Ni in the olivine,are small and show no clear stratigraphic fractionation trends.The abundance of Cr in the chromite in unit 10 does have a fractionationtrend, however, being generally highest at the bottom of theunit and lowest at the top, with a regression at the HWG zone.In general, Cr in chromite is highest at the base of a rhythmicunit and decreases upward, but it shows no overall decline throughsuccessive rhythmic units; Fe³ exhibits opposite variation,being lowest in the massive chromite, and highest in the disseminatedgrains. The G and H chromitite zones, in the Mountain View area, eachcontain enough chromite to form a single layer of massive chromitite{small tilde} 1 m thick. If their formation involved removalof only 30% of the Cr in the parental magmatic liquid (estimatedconcentration, 600 ppm), then this liquid could have amountedvolumetrically to an areally equivalent layer at least 2000m thick. Model calculations demonstrate that such a large volumeof liquid is consistent with the small variations of Mg/Fe inthe pyroxenes and olivines in the Stillwater cyclic units. We postulate that the G and H chromitite zones and cyclic unitsthat host them formed in response to the entry of new pulsesof primitive magmatic liquid into the Stillwater chamber. Fromexperimental observations, we infer that these pulses producedfountains in which the primitive liquid mixed with residualfractionated liquids, yielding hybrids that were compositionallywithin the chromite liquidus field (or volume) and that weresupercooled (supersaturated ) with respect to the oxide mineral.These effects may have been enhanced by low fO₂ (oxygen fugacity)in the primitive liquid and(or) by high fO₂ of the fractionatedliquid. The hybrid liquids probably collected at the bottomof the chamber in a zoned layer that then divided into double-diffusiveconvecting layers. In these circumstances, the lowest chromite-richlayer in a rhythmic sequence could have formed from the lowestdouble-diffusive liquid layer, and the next could then haveformed when this liquid mixed with the liquid layer above it—andso on up the sequence. We argue that the thick G and H chromititezones are situated toward the top of the Ultramafic Series becausethat level marks when the compositional contrasts between theinjected primitive liquid and the residual fractionated liquidsin the chamber were greatest.  相似文献   

Grain-size parameters of insoluble residues in mixed terrigenous-skeletal carbonate sediments and sedimentary rocks: some New Zealand examples     

CAMPBELL S. NELSON 《Sedimentology》1977,24(1):31-52

Grain-size parameters derived from the mechanical analysis of acid-insoluble residues from mixed terrigenous-shell beach sediments from Auckland, New Zealand, are more effective for interpreting the depositional processes, and for characterizing the beach environment on textural scatter plots, than are parameters based on the analysis of the total beach samples. This results mainly from the wide variations in size of hydraulically equivalent skeletal carbonate grains in the sediment, especially in the coarser size grades, but may also be accentuated by the local origin and susceptibility to alteration of the shell material. Compared with the total sediment grain-size distribution, the insoluble residues from the beach deposits are characteristically finer-grained, better sorted, and more consistently coarse-skewed and leptokurtic. The grain-size distribution characteristics of insoluble residues from several stratigraphic units in a sequence of Oligocene mixed terrigenous-skeletal shelf sediments in the South Auckland region distinguish depositional mechanisms and environmental energy levels for each unit that are consistent with interpretations made on the basis of carbonate petrography and palaeontology. With regard to the bulk content of terrigenous mud in the insoluble residues, the grain-size distribution of the fraction coarser than 4φ is alone diagnostic of the energy-time trends in these sediments. The grain-size parameters of the acid-insoluble residues in modern and ancient mixed terrigenous-skeletal carbonate sediments may provide more reliable criteria for distinguishing and characterizing the depositional environment of these deposits than do the parameters obtained from the size distribution of the total grain population.  相似文献   

Trace Metal Speciation of USGS Reference Sample MAG-I     

A. TESSIER  P.G.C. CAMPBELL  M. BISSON 《Geostandards and Geoanalytical Research》1980,4(2):145-148

The USGS reference sample marine mud MAG-1 has been subjected to a sequential extraction procedure designed to partition the constituent trace metals into five fractions: I-exchangeable; II- bound to carbonates; III-bound to Fe-Mn oxides; IV- bound to organic matter; V- residual. The analytical approach involved successive chemical extractions and the subsequent determination of trace metal concentrations (Co, Cu, Ni, Pb, Zn; Fe, Mn) in the leachates by atomic absorption spectrophotometry. The chemical speciation results obtained on four replicate sub-samples demonstrate that the coefficients of variation for metal concentrations in the individual fractions are generally better than + 10%. Comparison with published values for total trace metal concentrations in the MAG-1 sample suggests that the overall accuracy of the chemical extraction procedure is satisfactory.  相似文献   

Kyanite in upper Proterozoic quartzite near Veslebukta, Wedel Jarlsberg Land, western Spitsbergen     

A. CHENG  C. CRADDOCK  G. ZHU 《Polar research》1989,7(2):147-148

Kyanite has been identified in three specimens of dolomitic quartzite collected near Veslebukta, western Spitsbergen. The host rocks are fine-grained dolomitic quartzite with a recognizable foliation. The kyanite occurs as metacrysts, probably pre- or syntectonic; none appears detrital. The non-parallel kyanite crystals define laminae, and some of these layers are isoclinally folded, with axial planes parallel to foliation. This unusual occurrence of kyanite suggests that the metamorphism associated with the Proterozoic deformation may have reached medium grade, at least locally.  相似文献   

Signatures of storms, oceanic floods and forearc tectonism in marine shelf strata of the Quinault Formation (Pliocene), Washington, USA     

KATHLEEN A. CAMPBELL  ELIZABETH A. NESBITT†  JOANNE BOURGEOIS‡ 《Sedimentology》2006,53(5):945-969

Marine shelf strata of the Quinault Formation reflect the influences of storm–flood processes and convergent margin tectonism on sedimentation and palaeocommunity distributions in an active forearc basin of Early Pliocene age, western Washington, USA. The sedimentologic, ichnologic and invertebrate megafaunal character of coastal sea cliff exposures in the Pratt Cliff–Duck Creek area, Quinault Indian Nation, reveal five different sedimentary facies – scoured, Rosselia, bioturbated, mixed and Acharax. These facies document the shifting interplay and intensities among storms, waves and river‐flood plumes during transgression in inner to mid‐shelf settings. Storm sedimentation on the inner shelf is recorded north of Pratt Cliff by amalgamated, proximal tempestites of the scoured facies, which grade up‐section to thick deposits of hummocky cross‐stratified sandstone, indicative of strong wave influences. These hummocky beds alternate, in metre‐scale packages, with banded mudstone and siltstone that have distinctive sedimentologic and ichnofaunal characteristics (Rosselia facies). In particular the mudstone and siltstone occur as 1–15 cm‐thick, rhythmic, parallel beds that are laterally continuous, internally homogeneous to faintly laminated, and thus similar in nature to fine‐grained, oceanic flood deposits reported from shelf settings offshore the modern Eel River, northern California. The Quinault flood deposits are dominated by the ubiquitous trace fossil Rosselia socialis, comprising vertical, mud‐packed, flaring burrows with a sand‐filled central shaft which has been inferred as the feeding‐dwelling structure of a vermiform invertebrate adapted to high sedimentation rates in inner‐shelf settings. Fairweather conditions in between the higher energy periods of storms, waves and floods are recorded north of Pratt Cliff by the mixed facies, which is interpreted as representing the sand and mud zone of the inner‐ to mid‐shelf transition. Quieter, deeper, mid‐shelf, fairweather settings are typified by the bioturbated facies south of Pratt Cliff, where lower sedimentation rates and lower physical energies produced extensively bioturbated deposits of sandy siltstone punctuated, in places, by isolated sandy beds of distal tempestites. Quinault strata also chronicle stratigraphic signatures of subduction of the Juan de Fuca plate beneath western Washington during the Pliocene. For example, the imprint of geochemically unusual authigenic carbonates and a chemosynthetic palaeocommunity (Acharax facies) have been interpreted as a methane seep on the Quinault seafloor. Furthermore, a mobile rockground epifauna of pholadid bivalves became established on abundant, dark mudstone cobbles and pebbles sourced from the Hoh Assemblage, a Miocene accretionary prism that was actively deforming as well as interacting with Quinault forearc sediments during the Pliocene. Hoh mudstone clasts were supplied to the Quinault shelf via seafloor‐piercing diapirs and eroding mélange shear zones, exposures of which today occur in fault contact with Quinault strata along the coast from Taholah to the Raft River.  相似文献