The main objective of the present paper is to present an integrated approach to the study of faulting stages in coarse alluvial deposits. The study site is the alluvial fan of Nahal Shehoret, presently under an extremely arid regime. The exposure of fault scarps on the fan surfaces enables the identification of several geomorphic indicators employed in analysing and separating faulting events and periods of quiescence: (a) the nature of fault scarp topography; (b) soil catenary development on fault scarps; (c) buried paleosols in alluvial deposits; (d) colluvial bodies; (e) rotated clasts along fault planes. These indicators enable us to determine, at all sites studied, the total amount of displacement, to separate faulting events and the amount of their displacement per event, and to evaluate scarp stability and the duration of periods of tectonic quiescence.
Fluviatile deposits and morphology of alluvial surfaces as indicators of Quaternary environmental changes in the southern Negev, Israel
S. Grossman & R. GersonS U M M A R Y: Quaternary environmental changes in the southern Negev are recorded in the alluvial deposits and the geometry of depositional surfaces in the Timna Valley. There are some distinct differences between the alluvial deposits of the Holocene to modern flood plains and earlier (Pleistocene) ones. The Holocene to modern alluvium is characterized by sand, fine-to medium-sized gravel and very coarse gravel in large gravel bars. The sediments indicate environments ranging between extremely arid and semi-arid dominated by floods of low to moderate magnitude but with occasional short large floods. The Pleistocene sediments include: (1) debris-flow deposits indicating talus activity under a moderately arid to semi-arid climate; (2) alternating fine-grained and gravelly layers reflecting floods of low to moderate magnitudes. The nature of the soils supports these conclusions. Thick and argillic Reg soils are typical of the Pleistocene surfaces whereas shallow loamy ones are characteristic of the Holocene terraces. The alluvial surfaces usually converge downstream. The intersection points migrate upstream, following stages in the recession of a major escarpment. Broad pedimented surfaces and bajadas are characteristic of the Pleistocene period, whereas long narrow terraces of gentle declivity were formed during the Holocene. The latter suggest depletion of the available debris and in the effectiveness of large floods.
The proportion of patients meeting clinical practice guidelines compares favorably to similar studies. In some cases, patients' clinical conditions or unit HOB angle protocol explained not meeting guidelines. However, there were cases where reasons for not meeting guidelines were unknown.
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