LGM Glacial Equilibrium Line Reconstruction On Diancang Massif In Yunnan Province

The study of palaeo-glacier could help us to understand the past history of environment, and to predict regular of future changes in glacier. In the palaeo-glacier researching, one of the most important parameters is palaeo-ELA. This paper based on topographic data, combine previous study achievements with GIS analysis, to reconstruct part of ancient typical sub-glacier landforms on Diancang massif which in quaternary last glacial maximum, further, reconstruct surface shape on ice flow line and palaeo-ELAs according to the model. Also, made a discussion of topographical features of ancient sub-glacier in study area, modeling parameter selection conditions and spatial characteristics of palaeo-ELA The main findings are as follows:1) Topography characteristics of sub-glaciers in study area. The asymmetric shape of glacial valley causes that glacial landforms gathered on one side of the cirques and U-valley. Ice flow line distribution is a little tortuous, these all show the Last Glacial Maximum is not a perfect environment to entirely suitabled with glacier. Glacier in Longquan peak west slop is a reverse slope in end, causing the ice flow line turning; the development of a multistage stepped landforms show multi-level glaciation.2) Reconstruction of model parameters. Selection the of U-valley tendency as the ice flow line, to show more terrain features, and continuous change of valley shape index could reflect the sub-glacier topography.3) Surface features. The glacier in Yuju peak north slope more in line with the theory of the ice surface morphology and reflect power function characteristics; the glacier in Longquan peak west slop have a low ice thinkness, with a flat ice surface, and show stepladder characteristic in sub-glacier. Ice thickness average in Yuju peak north slope is two times of the Longquan peak west slope of, ice volume is three times of it.4) Features of palaeo-ELA. Value with AABR method and CF(cirque bottom elevation) method to obtain small, AAR method is more balanced to reflect the palaeo-ELA distribution, with resuls:glacier in Yuju peak north slope is 3800m, glacier in Longquan peak west slope is 3850m. Contrast characteristics, Yuju peak horizontal distance of the accumulation zone from the ablation area ratio is 2.7:1, reflecting the glacial cirque characteristic; Longquan peak is 1:1. That the fractures made form geological processes in east slope was reason which accelerate growth of glacier landforms. Glaciation ratio in Yuju peak north slope is 1:2, and in Longquan peak west slop is 1:2.3, higher than the theoretical value. Glaciation lower bound is almost same, due to the influence of slope caused by geological processes.