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Slope Deposits (slope + deposit)

Distribution by Scientific Domains

Earth and Environmental Science	100%

Selected Abstracts

Physical modelling of fault scarp degradation under freeze,thaw cycles

EARTH SURFACE PROCESSES AND LANDFORMS, Issue 14 2006
M. Font
Abstract Physical modelling has been developed in order to simulate the effects of periglacial erosion processes on the degradation of slopes and scarps. Data from 41 experimental freeze,thaw cycles are presented. They attest to the efficiency of periglacial processes that control both erosion and changes in scarp morphology: (i) cryoexpulsion leads to an increase of scarp surface roughness and modifies significantly the internal structure of the active layer; (ii) combined effects of frost creep and gelifluction lead to slow and gradual downslope displacements of the active layer (0·3 cm/cycle); (iii) debris flows are associated with the most significant changes in scarp morphology and are responsible for the highest rate of scarp erosion; (iv) quantification of the erosion rate gives values close to 1 cm3 cm,2 for 41 freeze,thaw cycles. These experimental results are consistent with field data acquired along the La Hague fault scarp (Normandy, France) where an erosion rate of 4·6 ± 1 m3 m,2 per glacial stage has been computed from the volume of natural slope deposits stored during the Weichselian glacial stage. These results show that moist periglacial erosion processes could lead to an underestimation of Plio-Quaternary deformation in the mid-latitudes. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Pendleian (early Serpukhovian) marine carbonates from SW Spain: sedimentology, biostratigraphy and depositional model

GEOLOGICAL JOURNAL, Issue 1 2004
P. Cózar
Abstract The San Antonio,La Juliana tectono-sedimentary unit contains the only Namurian marine carbonates in the southwestern part of the Iberian Peninsula. The analysis of this unit is fundamental in understanding the sedimentary evolution and tectonic movements which operated during the Namurian in this area. Using foraminifera the succession has been assigned to two biozones (Zones 17 and 18), both occurring in the Pendleian (early Namurian). Seven stratigraphic sections have been analysed: San Antonio, Burjadillo, Lavadero de la Mina, Cornuda, Lozana, Caridad and Via Crucis. The stratigraphic succession of the San Antonio,La Juliana Unit consists of olistolites in the basal part, with common debris-flow deposits (mainly of carbonates, with minor siliciclastic rocks), and turbidites, all of them embedded in shales. These rocks, interpeted as slope deposits, pass up into shallow-water platform facies, with sediments characteristic of the inner platform and tidal flats. Above these rocks, terrigenous deltaic deposits occur. Thus, the stratigraphic sections show an overall shallowing-upward trend. The isolation of some outcrops, and the duplication and absence of some parts of the stratigraphic succession are explained by tectonic movements. Overall, tectonic factors seem to be the main control rather than glacio-eustatic or autocyclic processes, and sedimentation took place in a strike-slip regime. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Application of ground-penetrating radar to determine the thickness of Pleistocene periglacial slope deposits

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2004
Daniela Sauer
Abstract Wide areas of the mountainous regions of Germany have rock covered by Pleistocene periglacial slope deposits (PPSD), formed by gelifluction during the cold periods of the ice ages in non-glaciated areas. The PPSD provide the parent material for soil development, and their physical characteristics affect several stabile soil properties. Because the PPSD play a significant ecological role, we studied the spatial distribution and properties of the PPSD in order to assess the distribution of the stabile soil properties. The high stone content of the PPSD greatly hinders augering and digging. Hence, we tested the use of ground-penetrating radar (GPR) as a potentially time-saving, non-destructive method to determine the thickness of the PPSD. In several study areas of the Rhenish Massif, GPR investigations of single soil profiles and soil transects along an exposed gas-pipeline ditch were carried out. The GPR images were compared to the actual thickness of the layers of the PPSD exposed in the profiles and the ditch. In the GPR images usually at least one distinct boundary could be identified, which occurs at the transition between the loose material and the hard rock, mostly ranging between 50 and 150,cm depth. In some cases, in which stone content changed abruptly between different layers of the PPSD, also the boundaries between these layers could be identified in the GPR image. On the other hand, in areas where remnants of the Mesozoic-Tertiary weathering mantle are preserved, the boundary between the saprolite and the overlying basal layer of the PPSD is ambiguous or not at all visible. Einsatz von Georadar zur Bestimmung der Mächtigkeit periglaziärer Lagen In den deutschen Mittelgebirgen sind die Gesteine weitflächig von periglaziären Lagen überzogen. Diese entstanden durch Gelifluktion während der Kaltzeiten in den unvergletscherten Bereichen. Sie stellen das Ausgangssubstrat der Bodenbildung dar und bestimmen eine Reihe stabiler Bodeneigenschaften. Die ökologische Bedeutung der periglaziären Lagen gab den Anlass, ihre Verbreitung und Eigenschaften zu erfassen, um daraus flächenhafte Aussagen über diese Eigenschaften abzuleiten. Da Bohrungen und Grabungen in den periglaziären Lagen häufig durch hohe Skelettgehalte erschwert werden, wurde untersucht, ob Georadar zur zeitsparenden, zerstörungsfreien Erfassung der Lagenmächtigkeiten eingesetzt werden kann. In verschiedenen Teilen des Rheinischen Schiefergebirges wurden Georadar-Messungen an Bodenprofilen sowie an Transekten entlang eines Gasleitungsgrabens durchgeführt, die jeweils mit den Mächtigkeiten der periglaziären Lagen verglichen wurden, die an der Graben- bzw. Profilwand aufgeschlossen waren. In den Radargrammen ist in der Regel mindestens eine deutliche Grenze zu erkennen. Diese tritt am Übergang vom Lockermaterial zum Festgestein auf, der in der Regel zwischen 50 und 150,cm Tiefe liegt. In einigen Fällen, in denen sich der Skelettgehalt an den Lagengrenzen abrupt stark verändert, sind auch Grenzen zwischen verschiedenen Lagen im Radargramm zu erkennen. Dagegen ist in Gebieten, in denen Reste der mesozoisch-tertiären Verwitterungsdecke im Untergrund anstehen, die Grenze zwischen der Basislage und dem Gestein im Radargramm nur diffus oder nicht ausgeprägt. [source]