Umfang:
XI, 401 S.
,
zahlr. Ill. u graph. Darst.
ISBN:
0632019050
Serie:
Geological Society special publication 35
Inhalt:
Tropical deserts have existed sporodically on our planet from the Precambrian to the Present, and seem not to have been a permanent feature of its surface (Glennie 1987). Depending on their definition, tropical deserts and semi-deserts currently occupy between approximately one fifth and one third of the Earth’s land surface, of which only about 4% is covered by that popular concept of what a desert consists of—sand dunes. The remaining area comprises barren rock (both hill and plateau) with a variable cover of sediments transported by ephemeral streams (wadis, arroyos) to form the deposits at the terminal points of these streams. Varying with the ratio of water supply to the annual potential rate of evaporation, those terminal areas may be occupied by desert lakes that are generally of a temporary nature (permanent only if the water is provided from beyond the margins of the desert or is fed by groundwater), and become more saline as they become desiccated. The end product of such a situation is a salina or sabkha (area of sand, silt or clay, commonly encrusted with halite).
There is no universally accepted definition of a desert. In its simplest form it can be defined as a barren tract of land over which rainfall is too limited or spasmodic to support vegetation adequately. Very few desert areas are completely devoid of vegetation, and many areas that fall within a desert in terms of average annual rainfall may have an even though sparse cover of plants that have adapted to the relatively arid environment in which they live. In this context, some writers define deserts as areas that have an average upper limit of 250 mm of annual rainfall, even though it may all fall in one storm and rainfall may not recur for several years. Perhaps more important than the rainfall itself is the ratio between it and the potential rate of evaporation—the aridity or desiccation factor. This is about 1:10 in some parts of the Australian Desert and up to 1:500 in areas of the Sahara (Cooke & Warren 1973).
Anmerkung:
Introduction ---
K. W. Glennie: Desert sediments: ancient and modern / Geological Society, London, Special Publications, 35:1-4, doi:10.1144/GSL.SP.1987.035.01.01: Fluvial Sediments: Process and Form ---
A. P. Schick, J. Lekach, and M. A. Hassan: Vertical exchange of coarse bedload in desert streams / Geological Society, London, Special Publications, 35:7-16, doi:10.1144/GSL.SP.1987.035.01.02 ---
S. Grossman and R. Gerson: Fluviatile deposits and morphology of alluvial surfaces as indicators of Quaternary environmental changes in the southern Negev, Israel / Geological Society, London, Special Publications, 35:17-29, doi:10.1144/GSL.SP.1987.035.01.03 ---
J. K. Maizels: Plio-Pleistocene raised channel systems of the western Sharqiya (Wahiba), Oman / Geological Society, London, Special Publications, 35:31-50, doi:10.1144/GSL.SP.1987.035.01.04 ---
Tectonism, Climatic Change and Fluviatile Desert Sediments ---
L. E. Frostick and I. Reid: Tectonic control of desert sediments in rift basins ancient and modern / Geological Society, London, Special Publications, 35:53-68, doi:10.1144/GSL.SP.1987.035.01.05 ---
H. Olsen: Ancient ephemeral stream deposits: a local terminal fan model from the Bunter Sandstone Formation (L. Triassic) in the Tønder-3, -4 and -5 wells, Denmark / Geological Society, London, Special Publications, 35:69-86, doi:10.1144/GSL.SP.1987.035.01.06 ---
A. M. Harvey: Alluvial fan dissection: relationships between morphology and sedimentation / Geological Society, London, Special Publications, 35:87-103, doi:10.1144/GSL.SP.1987.035.01.07 ---
M. A. J. Williams, P. I. Abell, and B. W. Sparks: Quaternary landforms, sediments, depositional environments and gastropod isotope ratios at Adrar Bous, Tenere Desert of Niger, south-central Sahara / Geological Society, London, Special Publications, 35:105-125, doi:10.1144/GSL.SP.1987.035.01.08 ---
Aeolian Sediments: Dust Dynamics and Deposits ---
W. B. Whalley, B. J. Smith, J. J. McAlister, and A. J. Edwards: Aeolian abrasion of quartz particles and the production of silt-size fragments: preliminary results / Geological Society, London, Special Publications, 35:129-138, doi:10.1144/GSL.SP.1987.035.01.09 ---
K. Pye and H. Tsoar: The mechanics and geological implications of dust transport and deposition in deserts with particular reference to loess formation and dune sand diagenesis in the northern Negev, Israel / Geological Society, London, Special Publications, 35:139-156, doi:10.1144/GSL.SP.1987.035.01.10 ---
R. Gerson and R. Amit: Rates and modes of dust accretion and deposition in an arid region—the Negev, Israel / Geological Society, London, Special Publications, 35:157-169, doi:10.1144/GSL.SP.1987.035.01.11 ---
H. Vine: Wind-blown materials and W African soils: an explanation of the ‘ferrallitic soil over loose sandy sediments’ profile / Geological Society, London, Special Publications, 35:171-183, doi:10.1144/GSL.SP.1987.035.01.12 ---
Dune Dynamics and Deposits ---
A. Gunatilaka and S. Mwango: Continental sabkha pans and associated nebkhas in southern Kuwait, Arabian Gulf / Geological Society, London, Special Publications, 35:187-203, doi:10.1144/GSL.SP.1987.035.01.13 ---
A. Warren and S. Kay: Dune networks / Geological Society, London, Special Publications, 35:205-212, doi:10.1144/GSL.SP.1987.035.01.14 ---
L. B. Clemmensen: Complex star dunes and associated aeolian bedforms, Hopeman Sandstone (Permo-Triassic), Moray Firth Basin, Scotland / Geological Society, London, Special Publications, 35:213-231, doi:10.1144/GSL.SP.1987.035.01.15 ---
B. P. J. Williams, E. K. Wild, and R. J. Suttill: Late Palaeozoic cold-climate aeolianites, southern Cooper Basin, South Australia / Geological Society, London, Special Publications, 35:233-249, doi:10.1144/GSL.SP.1987.035.01.16 ---
R. A. Carruthers: Aeolian sedimentation from the Galtymore Formation (Devonian), Ireland / Geological Society, London, Special Publications, 35:251-268, doi:10.1144/GSL.SP.1987.035.01.17 ---
Grain Size, Process and Dune Environment ---
E. C. Flenley, N. R. J. Fieller, and D. D. Gilbertson: The statistical analysis of ‘mixed’ grain size distributions from aeolian sands in the Libyan Pre-Desert using log skew Laplace models / Geological Society, London, Special Publications, 35:271-280, doi:10.1144/GSL.SP.1987.035.01.18 ---
I. Livingstone: Grain-size variation on a ‘complex’ linear dune in the Namib Desert / Geological Society, London, Special Publications, 35:281-291, doi:10.1144/GSL.SP.1987.035.01.19 ---
D. S. G. Thomas: Discrimination of depositional environments using sedimentary characteristics in the Mega Kalahari, central southern Africa / Geological Society, London, Special Publications, 35:293-306, doi:10.1144/GSL.SP.1987.035.01.20 ---
Chemical Sediments ---
D. A. Hendry: Silica and calcium carbonate replacement of plant roots in tropical dune sands, SE India / Geological Society, London, Special Publications, 35:309-319, doi:10.1144/GSL.SP.1987.035.01.21 ---
C. R. Roberts and C. W. Mitchell: Spring mounds in southern Tunisia / Geological Society, London, Special Publications, 35:321-334, doi:10.1144/GSL.SP.1987.035.01.22 ---
Remote Sensing of Desert Sediments ---
C. S. Breed, J. F. McCauley, and P. A. Davis: Sand sheets of the eastern Sahara and ripple blankets on Mars / Geological Society, London, Special Publications, 35:337-359, doi:10.1144/GSL.SP.1987.035.01.23 ---
M. M. Ashour: Surficial deposits of Qatar Peninsula / Geological Society, London, Special Publications, 35:361-367, doi:10.1144/GSL.SP.1987.035.01.24 ---
A. C. Millington, A. R. Jones, N. Quarmby, and J. R. G. Townshend: Remote sensing of sediment transfer processes in playa basins / Geological Society, London, Special Publications, 35:369-381, doi:10.1144/GSL.SP.1987.035.01.25
In:
Geological Society special publication
Sprache:
Englisch
URL:
http://sp.lyellcollection.org/content/35/1
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