Open crustacean burrows associated with hardgrounds in the Jurassic of the Cotswolds,England     

F.T. Fürsich  T.J. Palmer 《Proceedings of the Geologists' Association. Geologists' Association》1975,86(2):171-181

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Petrogenesis of cataclastic rocks within the San Andreas fault zone of Southern California U.S.A.     

J. Lawford Anderson  Robert H. Osborne  Donald F. Palmer 《Tectonophysics》1980,67(3-4)

This paper petrologically characterizes cataclastic rocks derived from four sites within the San Andreas fault zone of southern California. In this area, the fault traverses an extensive plutonic and metamorphic terrane and the principal cataclastic rock formed at these upper crustal levels is unindurated gouge derived from a range of crystalline rocks including diorite, tonalite, granite, aplite, and pegmatite.The mineralogical nature of this gouge is decidedly different from the “clay gouge” reported by Wu (1975) for central California and is essentially a rock flour with a quartz, feldspar, biotite, chlorite, amphibole, epidote and oxide mineralogy representing the milled-down equivalent of the original rock. Clay development is minor (less than 4 wt. %) to nonexistent and is exclusively kaolinite. Alterations involve hematitic oxidation, chlorite alteration on biotite and amphibole, and local introduction of calcite. Electron microprobe analysis showed that in general the major minerals were not reequilibrated with the pressure—temperature regime imposed during cataclasis.Petrochemically, the form of cataclasis that we have investigated is largely an isochemical process. Some hydration occurs but the maximum amount is less than 2.2% added H₂O. Study of a 375 m deep core from a tonalite pluton adjacent to the fault showed that for Si, Al, Ti, Fe, Mg, Mn, K, Na, Li, Rb, and Ba, no leaching and/or enrichment occurred. Several samples experienced a depletion in Sr during cataclasis while lesser number had an enrichment of Ca (result of calcite veining).Texturally, the fault gouge is not dominated by clay-size material but consists largely of silt and fine sand-sized particles. An intriguing aspect of our work on the drill core is a general decrease in particulate size with depth (and confining pressure) with the predominate shifting sequentially from fine sand to silt-size material.The original fabric of these rocks is commonly not disrupted during the cataclasis. It is evident that the gouge development in these primarily igneous crystalline terranes is largely an in situ process with minimal mixing of rock types. Fabric analyses reveal that brecciation (shattering), not shearing, is the major deformational mechanism at these upper crustal levels.  相似文献   

Postglacial midge community change and Holocene palaeotemperaturereconstructions near treeline, southern British Columbia (Canada)     

Samantha Palmer  Ian Walker  Markus Heinrichs  Geoffrey Scudder 《Journal of Paleolimnology》2002,28(4):469-490

Stratigraphic analysis of fossil chironomid head capsules wasperformed at North Crater Lake and Lake of the Woods, located at treeline (2250m) in the Ashnola region of southernmost British Columbia. Priorto 10,000 yr BP, cold conditions were indicated by the lack oftemperate taxa and the presence of cold-stenotherms. The abundance anddiversity of warm-adapted taxa (e.g., Dicrotendipes,Microtendipes, Polypedilum and Cladopelma)increased rapidly after 9500 yr BP, whereas taxa indicative ofcold conditions disappeared. Beginning prior to deposition of the Mazama ash(6730 ± 40 yr BP), several warm-adapted taxa decreasedin abundance. Mid- to late-Holocene assemblages (ca. 4500yr BP to present) indicated continued cooling as revealed by afurther reduction in diversity and abundance of warm-adapted taxa atboth lakes, and the reappearance of cold-stenotherms in Lake of theWoods. Diversity changes in the cores paralleled the inferred climatic changes.Diversity was low during the late-glacial, increased in theearly-Holocene, and declined after 5400 yr BP.To quantitatively infer past climatic changes, a newweighted yphen;averaging partial-least-squares (WA-PLS)model was developed and applied to the fossil midge data. The quantitativereconstructions revealed late-glacial mean July air temperatures rangingfrom about 8 to 10°C. Summer air temperatures were highest inthe early Holocene (13 to 17°C), gradually decreasing by about3°C through the mid- to late-Holocene.  相似文献   

Chemical compositions of tourmaline in the Yindongzi-Tongmugou Pb-Zn deposits,Qinling, China: Implications for hydrothermal ore-forming processes     

S. -Y. Jiang  M. R. Palmer  Y. -H. Li  C. -J. Xue 《Mineralium Deposita》1995,30(3-4):225-234

A microprobe study has been carried out on the chemical composition of tourmaline from the Yindongzi and Tongmugou stratabound Pb-Zn ore deposits, eastern Qinling, China. Tourmaline was analysed from a variety of rock types representative of its various occurrences associated with the ore bodies. All the tourmalines studied here belong to the schorl-dravite series. Most are of hydrothermal origin with Mg > Fe and Na > Ca. Some detrital cores of tourmaline have been recognized from their geometry and chemistry, with Fe > Mg. The chemical trends from core to rim in zoned grains suggest a multi-stage model for the growth of tourmaline and genesis of the ore bodies. The first stage was represented by a more Mg-rich hydrothermal fluid in the submarine hydrothermal system, producing Mg-rich tourmalines by selective replacement of clay-rich sediments close to the sediment-water interface. The second stage was dominated by Fe-rich hydrothermal fluid and resulted in overgrowth of Fe-rich tourmaline rims. This stage also led to the nucleation and growth of new tourmaline crystals and was responsible for the formation of the main massive sulphide orebodies. Finally, a further period of hydrothermal activity or a metamorphic event led to the formation of an additional rim of Mg-rich tourmaline.  相似文献   

Paleosols and their relevance to Precambrian atmospheric composition     

Palmer JA  Phillips GN  McCarthy TS 《The Journal of geology》1989,97(1):77-92

Various paleosols have been reported from within the Witwatersrand and Ventersdorp Supergroups, South Africa. They were studied in an attempt to constrain the amount of oxygen available in the atmosphere during deposition of the gold- and uranium-bearing Witwatersrand conglomerates. The majority of these horizons do not have any physical characteristics of paleosols, and none of them have a chemistry consistent with weathering, suggesting they have been subjected to modification by later alteration processes. A similar chemistry, indicating overprinting of any original soil chemistry, has been reported from paleosols elsewhere (Elliot Lake region, Canada; Hekpoort basalt, South Africa), but it does not appear that significant cognizance has been taken of this fact when using these paleosols to determine the composition of the Precambrian atmosphere. It is concluded here that characteristics previously attributed to Precambrian weathering in an oxygen-deficient atmosphere are better explained by post-burial, hydrothermal alteration along lithological contacts.  相似文献   

Removal of Phosphate in Aqueous Solution by Permethylated Poly(ethyleneimine) Entfernung von Phosphat mit permethyliertem Poly(ethylenimin) in wäßriger Lösung     

V. Palmer  R. Zhou  K. E. Geckeler  E. Bayer 《洁净——土壤、空气、水》1994,22(5):231-235

The use of cationic, water-soluble, permethylated poly(ethyleneimine) (PMP) for the removal of phosphate ions was investigated using the Liquid-phase Polymer-based Retention (LPR) technique. The results showed that the retention values were dependent on the filtration factor (Z) and pH. In the presence of 10 mg/L phosphate and 1% PMP, 52% of the phosphate was retained at pH = 1.0 and 93% at pH = 8.5 for Z = 2. However only 11% of phosphate was retained at pH = 1.0 and 80% at pH = 8.5 for Z = 5. The maximum binding capacity of phosphate by 1% of PMP was 22 mg phosphate per gram of PMP at pH = 1.0 and 185 mg phosphate per gram of PMP at pH = 7.0. The influence of nitrate, chloride, and sulfate ions on the interaction of phosphate ions with PMP was also investigated. It was found that the interaction is strongly influenced by sulfate ions. In addition, viscosimetric measurements were performed and discussed.  相似文献   

A Biota Associated with Matuyama-Age Sediments in West-Central Illinois     

Barry B. Miller  Russell W. Graham  Alan V. Morgan  Norton G. Miller  William D. McCoy  Donald F. Palmer  Alison J. Smith  J. J. Pilny 《Quaternary Research》1994,41(3)

A fossil assemblage containing molluscs, mammals, insects, ostracodes, and plants has been recovered from a silt-filled depression near Lima, in west-central Illinois. The reversed remanent magnetic signature of the sediments and the temporal ranges of two mammals, Microtus paroperarius and Lasiopodomys deceitensis, constrain the age of the assemblage to between 730,000 and 830,000 yr B.P. The extent of isoleucine epimerization in the molluscan shell is consistent with this age interpretation. The fauna includes at least 43 taxa of beetles from 11 families, 35 nominal species of molluscs, and two genera of ostracodes. The mammals include two shrews, three rodents, and a rabbit. The plant macrofossils (no pollen recovered) include 25 species of seed plants and four kinds of terrestrial or wetland mosses. Most of the plant species identified still occur in the upper Midwest, although a few of the taxa are found mainly to the north of the site. The fauna is characterized by an almost total absence of true aquatic taxa. The association of both boreal and thermophilous faunal and floral elements suggest that summer temperatures were not greatly different from present ones, but cooler, moist areas must have been available to support the boreal elements. Local conditions were probably similar to those now found in northeastern Iowa, where rains blocks, fissures, and joints in carbonate bedrock serve as traps for debris accumulations, provide shade, and are kept cool and moist during the hot summer months by cold-air drainage and groundwater seepage. Summer mean temperature in these microhabitats was probably between 18 and 20°C, similar to temperatures that now occur near the northern hardwood spruce-fir transition in the eastern United States.  相似文献   

THE CORRELATIONS BETWEEN SST AND SUMMER PRECIPITATION OVER EASTERN CHINA AND THE EFFECT OF THE SST ANOMALY IN THE SOUTH CHINA SEA ON THE SUMMER MONSOON AND PRECIPITATION          下载免费PDF全文

Sun Zhaobo  Zhang jiji  T. N. Palmer 《Acta Meteorologica Sinica》1988,2(4):426-435

By use of the method of empirical orthogonal function resolution a study is made of the distributionpatterns of summer rainfall percentage anomalies over eastern China with the result that such anomalies areable to reflect the relative amount of local precipitation.Then the correlations are obtained through calcula-tion between the patterns and the January and June global SST,indicating key regions in association withChina's summer rainfall.On this basis,an 11-layer atmospheric circulation model by the U.K.Meteorol-ogical Office is used to simulate the effect of a weak SST anomaly of the South China Sea upon the summermonsoon circulation in China's mainland.Results show that‘attraction’is available for the Indian monsoonwith a warm anomaly of the SST and‘repelling’with a cold,representing one of the reasons for the anti-phase between the monsoons over the South China Sea and India.Such functions of SST anomalies have asignificant influence on summer rainfall over eastern China.  相似文献   

Twinning in tetragonal leucite     

David C. Palmer  Andrew Putnis  Ekhard K. H. Salje 《Physics and Chemistry of Minerals》1988,16(3):298-303

The change from cubic to tetragonal symmetry in natural leucite, KAlSi₂O₆, involves two types of twinning, which appear sequentially with decreasing temperature: (1) lamellar, associated with the point group symmetry reduction m3m to 4/mmm; (2) merohedric, associated with the change 4/mmm to 4/m. Twin orientations have been deduced from X-ray precession photos and TEM diffraction patterns and images. These are confirmed by theory, using the concept of spontaneous strain and the symmetry relations between adjacent domains. Lamellar twins have boundaries parallel to {101} of the cubic phase, and are cross-cut by the merohedric twins, which have irregular boundaries with x and y in adjacent domains interchanged. On an electron microscopic scale, the distortion arising from twin intersections is revealed by a curvature of one twin wall adjacent to another, and by needle-shaped domains. The macroscopic orientation of the lamellar twins is related to the lattice parameters and hence the magnitude of the spontaneous strain. This in turn leads to the characterisation of the order parameter for the m3m to 4/mmm transformation.  相似文献   

Recent sedimentation,northeastern Port Valdez,Alaska     

Harold D. Palmer 《Geo-Marine Letters》1981,1(3-4):207-212

Sediments accumulating on the northeastern shore of Port Valdez, a fjord leading to Prince William Sound in southern Alaska, are derived from both deltaic and alluvial fan processes. The resulting thick wedge of Recent silts, sands, shells and gravels lies atop irregular ridges of local graywacke bedrock and scattered till deposits. Seismic reflection profiling augmented by soil borings indicates that rapid infilling and upbuilding has occurred at this site. Evidence of slumping suggests general instability of steep submarine slopes in an area characterized by strong earthquakes and large tidal ranges.  相似文献