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Gaetano Robustelli Federica Luc Fabio Corbi Teresa Pelle Francesco Dramis Giandomenico Fubelli Fabio Scarciglia Francesco Muto Domenico Cugliari 《Geomorphology》2009,106(3-4):165-179
In this paper we present the results of an integrated geomorphological, pedological and stratigraphical study carried out along the Ionian coast of northern Calabria (southern Italy). This area is characterised by the occurrence of five orders of alluvial terraces that are striking features of the landscape, where large and steep catchments debouch from the mountain front to the hilly coastal belt.Field investigations indicate that the deposits of all five terraces are suggestive of shallow gravel-bed braided streams.On the basis of the age of the Pleistocene substratum and morphostratigraphic correlation with marine terraces cropping out in the nearby areas, each order has been associated to specific marine oxygen isotope stages.Consequently, we focused on the interplay of allocyclic factors influencing stream aggradation/degradation. Soil features and other climatic proxies suggest that climate didn't play an important role with respect to tectonic and base-level changes in controlling fluvial dynamics.In particular, we recognised that during the middle Pleistocene the study area experienced a period of subaerial landscape modelling, as suggested by the thick and complex alluvial sequence of the highest terrace (T1). The onset of regional uplift marks a change in the geomorphic scenario, with tectonic and eustatically driven changes in base-level working together in causing switches in fluvial aggradational/erosional phases (T2–T5 terraces). Because of the uplift, river dissection occurred during phases of sea level fall, whereas aggradation phases occurred during periods of climate amelioration (sea level rise) just before highstands were attained.As a consequence, the stepped terraces in the study area reflect the interplay between tectonics (uplift) and sea level changes, in which terraces define episodes of relative sea level fall during the late Quaternary. 相似文献
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Tsvetkov Yu. P. Kuznetsov V. D. Golovkov V. P. Brekhov O. M. Pelle V. A. Krapivnyi A. V. Nikolaev N. S. 《Doklady Earth Sciences》2011,436(1):117-121
The solution to the problem of extraction of the anomaly Earth’s magnetic field (EMF) from stratospheric balloon magnetic
surveys with the help of global analytical models of the normal EMF is proposed. In the problem solution, errors for the analytical
models of the normal EMF and its secular variation at a set moment of time are assessed; the found error is introduced as
a correction to the extracted anomaly EMF. The error of the model is determined in the places where significant magnetic anomalies
are absent. In this case, the error of the model corresponds to deviations of the normal EMF components, synthesized by coefficients
of analytical models, and to deviations of the EMF secular variations from the measured values at quite a low value of the
variable EMF or one being taken into account. These places are determined when carrying out additional measurements in vertical
gradients of the EMF with the use of scalar magnetometers at the gauge length of 6 km. It has been shown that the found places
can be considered as nonanomaly, if the difference of values of the anomaly EMF at the gauge length of 6 km does not exceed
1.5 nT within the profile’s portion of about 100 km in length. An experiment in nature has revealed that errors for the IGRF-2005
and IGRF-2010 models, corrected for secular variation of the EMF, can reach 200 and 140 nT, respectively, within the limits
of the territory where the Kama-Emba magnetic anomaly is located; these errors are determined by the considered causes. Comparison
of aerostatic profiles of magnetic anomalies with data on the anomaly EMF, derived from the maps, has shown that the realizations
derived from the maps contain overestimated negative values of the anomaly EMF, because they reflect processes in the near-surface
layer of the Earth’s crust. This fact causes the situation when attempts to recalculate the anomaly EMF into the upper half-space
by the near-surface data still have not been successful. Only realizations derived at the altitudes comparable to the thickness
of the Earth’s crust can give an adequate model of the anomaly EMF in the circumterrestrial space and enable us to recalculate
magnetic anomalies reliably into any altitude levels. 相似文献
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