Título del libro: Arid And Semi-Arid Environments: Biogeodiversity, Impacts And Environmental Challenges
Título del capítulo: Geomorphodiversity of the ejina basin in inner mongolia, central asia: Implications for late quaternary landscape evolution and palaeoenvironmental change
YAN GAO;
Autores externos:
Idioma:
Inglés
Año de publicación:
2015
Palabras clave:
Central asian; Desert basin; Ejina; Geomorpholodiversity; Landscape patterns; Late quaternary climate
Resumen:
The north-south trending basin of Ejina in Inner Mongolia of northernwestern China, Central Asia is located at the lower reaches of the Heihe River watersheds and is a regional tectonic depression limited to the west part of the Alashan Plateau. Though neotectonic activity is believed to be the major factor in the evolution of the topography, detailed documentation and analysis of climatic landscape features like alluvial fans, desert plains, aeolian dunes and bedrock gorges and their environmental implications are lacking. The present study is a sitespecific documentation of landforms developed in the wide part of the Ejina Basin, with the aim to identify the climatic landforms based on the method of climatic geomorphology and to evaluate its landscape evolution and response to palaeoclimate changes. The morphodynamics of older landscapes are recognized by making comparison with the present climate and its corresponding landscapes. Occurrence of desert plains and aeolian dunes in the central basin is inferred to be the products of modern hyper-arid climate. No active geomorphoclimatic dynamics for development of desert bedrock gorges and pediments is observed at the margins in the present day conditions, thus we infer an obvious linkage of these landforms to the humid phases, which provided high energy runoff for the formation of landforms associated erosional features. Clear evidences testifying the basin-scale shifting and transformation of different morphoclimatic zones in the Ejina basin are observed, which prove that the main geomorphic unit is changed from an alluviallacustrine plain to a desert plain. Pediments and desert gorges are both relict landforms associated with more humid and colder climate during the last glacial period. However, the coexistence of diverse landscapes and the consequent geomorphodiversity in the basin should be a compound result of surficial processes other than glaciations. Fluvial/alluvial actions, aeolian, abrasion/deflation, aggradation and degradation processes together with climatic changes have conjunctionally played important role. The climate and hydrological conditions of the basin during the last glaciation and during the Early Holocene were much better than at present, possibly having an average annual precipitation ranged between 60~350 mm on the margins of the basin and being characterized in the central basin by high lake levels during ca. 39-23 ka BP but great fluctuations during Holocene. Because the Asian summer monsoon was quite weak during the glacial times, the periods of lower aridity during the late Pleistocene in the Ejina Bain could be induced by an increase of the westerlies and a weakening of the Asian winter monsoon on the arid areas of the central Asia. © 2015 by Nova Science Publishers, Inc. All rights reserved.
Entidades citadas de la UNAM:
ISBN:
9781634834100
Editorial:
Nova Science Publishers, Inc. Nombre de la publicación:
Geomorphodiversity of the ejina basin in inner mongolia, central asia: Implications for late quaternary landscape evolution and palaeoenvironmental change
Página inicial:
37
Página final:
77
