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1.
Clay minerals of about 600 samples from drill cores in the Tertiary shales of the Rhinegraben, were analysed by X-ray diffraction methods. It was found that the abundance of smectite decreases with increasing amounts of mixed layer clays and illites, suggesting a diagenetic alteration of smectite with increasing temperatures of the sediments as was also observed in other sedimentary basins. As for the relation between smectite alteration and temperatures as measured in sample depths, in the marine Graue Schichtenfolge (Middle Oligocene) when temperatures reach 70°C and over, smectite no longer is to be found. In the limnic Bunte Niederröderner Schichten (Upper Oligocene) the maximum temperature of smectite occurrence is about 80°C. These temperatures also fit the results of former field studies of the thermal stability of smectite. In the brackish to limnic Obere and Untere Hydrobienschichten (Lower Miocene) however, smectite seems to have disappeared already at a temperature of over 30°C. Although the smectite distribution in the latter formations may depend partly on its inhomogenous deposition there is also evidence for the diagenetic alteration of smectite in these formations. The rapid disappearance of smectite in these formations was possibly caused by a greater availability of potassium ions since high permeability of these strata provide extraordinarily good mobility of the pore solutions. In the older Lymnäenmergel formation (Upper Eocene) a more advanced stage of smectite alteration is found as compared to the other formations at corresponding temperatures. This is considered to be the consequence of the longer duration of diagenesis and the rock salt inclusions of this saline formation which might have enriched the pore solutions with potassium ions.  相似文献   
2.
DIETRICH HEYE 《Sedimentology》1971,16(1-2):111-117
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3.
The most recent deglaciation resulted in a global sea‐level rise of some 120 m over ca 12 000 years. A moving boundary numerical model is developed to predict the response of rivers to this rise. The model was motivated by experiments at small scale, which have identified two modes describing the transgression of a river mouth: (i) autoretreat without abandonment of the river delta (no sediment starvation at the topset–foreset break); and (ii) sediment‐starved autoretreat with abandonment of the delta. In the latter case, transgression is far more rapid, and its effects are felt much further upstream of the river mouth. A moving boundary numerical model that captures these features in experimental deltas is adapted to describe the response of the Fly–Strickland River system, Papua New Guinea. In the absence of better information, the model is applied to the case of sea‐level rise without local climate change in New Guinea. The model suggests that: (i) sea‐level rise has forced the river mouth to transgress over 700 km since the last glacial maximum; (ii) sediment‐starved autoretreat has forced enough bed aggradation to block a tributary with a low sediment load and create the present‐day Lake Murray; (iii) the resulting aggradation was sufficient to move the gravel–sand transition on the Strickland River upstream; (iv) the present‐day Fly Estuary may be, in part, a relict river valley drowned by sea‐level rise and partially filled by tidal effects; and (v) the Fly River is presently reforming its bankfull geometry and prograding into the Fly Estuary. A parametric study with the model indicates that sediment concentration during floods plays a key role in determining whether or not, and to what extent, transgression is expressed in terms of sediment‐starved autoretreat. A sufficiently high sediment concentration can prevent sediment‐starved autoretreat during the entire sea‐level cycle. This observation may explain why some present‐day river mouths are expressed in terms of deltas protruding into the sea, and others are wholly contained within embayments or estuaries in which water has invaded landward.  相似文献   
4.
Combined investigations of isotopes, pollen, and molliisc shells were carried out on a Latc Glacial limnic high-resolution sediment sequence from the Geiseltal open-cast mine in Central Gcrmany. The dala confirm thc division of the Late Glacial biozones into two colder (Older and Younger Dryas) and two warmer periods (Bølling, Allcrød), which have already bccn cstablishcd lor the Central and Northern German area. Radiocarbon data, mainly based on wood material, cover a time span between c , 10 800 BP and 12 760 BP, indicating a mean sedimentation rate of c . 2 mm/yr. The stable isotope data (δ18O, δ13C) reflect the transition periods between the climatic phases as changes in relative air humidity (transition from dry, cold to warmer. more humid conditions). The dominance of evaporation effects, however, is superimposed on any ternpcratiirc aignal throughout the profile. Repeated conversions of the hydrologic regime (silting-up phases. lake-level variations) characterize the specific history of the lake development.  相似文献   
5.
The regional dust model system LM-MUSCAT-DES was developed in the framework of the SAMUM project. Using the unique comprehensive data set of near-source dust properties during the 2006 SAMUM field campaign, the performance of the model system is evaluated for two time periods in May and June 2006. Dust optical thicknesses, number size distributions and the position of the maximum dust extinction in the vertical profiles agree well with the observations. However, the spatio-temporal evolution of the dust plumes is not always reproduced due to inaccuracies in the dust source placement by the model. While simulated winds and dust distributions are well matched for dust events caused by dry synoptic-scale dynamics, they are often misrepresented when dust emissions are caused by moist convection or influenced by small-scale topography that is not resolved by the model. In contrast to long-range dust transport, in the vicinity of source regions the model performance strongly depends on the correct prediction of the exact location of sources. Insufficiently resolved vertical grid spacing causes the absence of inversions in the model vertical profiles and likely explains the absence of the observed sharply defined dust layers.  相似文献   
6.
A new occurrence of Recent stromatolites different from those known up to now has been discovered on tidal flats of the Bay of Saint-Jean (near Cape Timiris). Their most remarkable features are predominance of quartz sand instead of carbonate, characteristic surface-contouring by grazing fish, absence of cementation, intensive reworking by crabs, and connection with saline sabkha deposits. Entrapment of sand grains and great resistance of the algal sheaths are most important for stromatolitic growth, although today destruction appears to prevail over accretion. Quartz sand of aeolian dunes and carbonatic pellets of aragonitic ooze feeders are the main constituents of the stromatolitic sediments. According to the tidal range the following zonation of the algal mat exists: (A) knoll and cuspate zone, (B) flat zone, (C) gas-domed zone, and (D) crinkle zone.  相似文献   
7.
In May–June 2006, airborne and ground-based solar (0.3–2.2 μm) and thermal infrared (4–42 μm) radiation measurements have been performed in Morocco within the Saharan Mineral Dust Experiment (SAMUM). Upwelling and downwelling solar irradiances have been measured using the Spectral Modular Airborne Radiation Measurement System (SMART)-Albedometer. With these data, the areal spectral surface albedo for typical surface types in southeastern Morocco was derived from airborne measurements for the first time. The results are compared to the surface albedo retrieved from collocated satellite measurements, and partly considerable deviations are observed. Using measured surface and atmospheric properties, the spectral and broad-band dust radiative forcing at top-of-atmosphere (TOA) and at the surface has been estimated. The impact of the surface albedo on the solar radiative forcing of Saharan dust is quantified. In the SAMUM case of 19 May 2006, TOA solar radiative forcing varies by 12 W m−2 per 0.1 surface-albedo change. For the thermal infrared component, values of up to +22 W m−2 were derived. The net (solar plus thermal infrared) TOA radiative forcing varies between −19 and +24 W m−2 for a broad-band solar surface albedo of 0.0 and 0.32, respectively. Over the bright surface of southeastern Morocco, the Saharan dust always has a net warming effect.  相似文献   
8.
Vertical profiles of dust key optical properties are presented from measurements during the Saharan Mineral Dust Experiment (SAMUM) by Raman and depolarization lidar at two ground-based sites and by airborne high spectral resolution lidar. One of the sites, Tinfou, is located close to the border of the Sahara in Southern Morocco and was the main in situ site during SAMUM. The other site was Ouarzazate airport, the main lidar site. From the lidar measurements the spatial distribution of the dust between Tinfou and Ouarzazate was derived for 1 d. The retrieved profiles of backscatter and extinction coefficients and particle depolarization ratios show comparable dust optical properties, a similar vertical structure of the dust layer, and a height of about 4 km asl at both sites. The airborne cross-section of the extinction coefficient at the two sites confirms the low variability in dust properties. Although the general picture of the dust layer was similar, the lidar measurements reveal a higher dust load closer to the dust source. Nevertheless, the observed intensive optical properties were the same. These results indicate that the lidar measurements at two sites close to the dust source are both representative for the SAMUM dust conditions.  相似文献   
9.
Vertical profiles of the linear particle depolarization ratio of pure dust clouds were measured during the Saharan Mineral Dust Experiment (SAMUM) at Ouarzazate, Morocco (30.9°N, –6.9°E), close to source regions in May–June 2006, with four lidar systems at four wavelengths (355, 532, 710 and 1064 nm). The intercomparison of the lidar systems is accompanied by a discussion of the different calibration methods, including a new, advanced method, and a detailed error analysis. Over the whole SAMUM periode pure dust layers show a mean linear particle depolarization ratio at 532 nm of 0.31, in the range between 0.27 and 0.35, with a mean Ångström exponent (AE, 440–870 nm) of 0.18 (range 0.04–0.34) and still high mean linear particle depolarization ratio between 0.21 and 0.25 during periods with aerosol optical thickness less than 0.1, with a mean AE of 0.76 (range 0.65–1.00), which represents a negative correlation of the linear particle depolarization ratio with the AE. A slight decrease of the linear particle depolarization ratio with wavelength was found between 532 and 1064 nm from 0.31 ± 0.03 to 0.27 ± 0.04.  相似文献   
10.
Type I (Cr-diopside group) peridotite xenoliths occur abundantlyat four volcanic vents (Szentb?k?lla, Szigliget, Bondor?-hegy,G?rce) in the Transdanubian Volcanic Region of Hungary (TVR).They comprise four-phase spinel Iherzolites and spinel harzburgites.The only additional phase a brown amphibole in some of the nodulesfrom Szigliget. Protogranular and equigranular textures prevailexcept at G?rce where porphyroclastic textures predominate.Attention has been focused however, on a rarer textural typedisplaying spherical, subhedral, or rarely even euhedral spinelinclusions in silicate phases (special group xenoliths). Major and trace element data permit the reconstruction of severalmantle events and provide indications of the nature and dimensionsof heterogeneities in the lithospheric mantle beneath the TVR.The most important events in their supposed order of time aresummarized as follows: (A) An old depletion event evidencedby LREE abundances in diopside (Type IA xenoliths) (B) laterenrichment in LREE and other LIL elements (Type IB xenoliths);(C) hydrous metasomatism bringing about the formation of amphibole;(D) magmatic introduction of Type II (Al-augite group) materialand related chemical exchange reactions with cool mantle rocks;and (E) veining of the uppcr mantle by plagioclase-free amphibolite(probably slightly prior to the volcanic eruptions). In addition,in our interpretation special group xenoliths indicate an ancientmagmatic event. As evidence we can mention: (1) textural featureswhich may be connected with generation of cumulates and whichare associated with (2) anomalous bulk rock and phase chemistry(as compared with most published data) such as: (a) a generallow abundance of Al; (b) high Cr in the spinel phase; (c) unusuallyhigh contents of Fe3+ in spinel; (d) anomalous distributionof Al between enstatite and diopside; and (e) other disequilibriumfeatures such as the lack of the expected correlation of majorelements with mg-value or important departures from the correlationlines. These peculiarities suggest that the special group xenolithsprobably reflect crystal accumulation rather than an equilibriumpartial melting process.  相似文献   
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