Mineral magnetism and other characteristics of sediments from an alpine lake (3,410 m a.s.l.) in central China and implications for late Holocene climate and environment

摘要

The Qinling Mountain Range (33 degrees-34 degrees 30'N, 107 degrees-111 degrees E; 3,767 m a.s.l.) lies south of the Chinese Loess Plateau and functions as the boundary between 'north' and 'south' China. Taibai Mountain (33 degrees 41'-34 degrees 10'N, 107 degrees 19'-107 degrees 58'E; 3,767 m a.s.l.) is the central massif and highest part of the range and is the highest mountain in eastern and central China, east of 105 degrees E. It is also one of two mountains higher than the modern climatic timberline and the only one where high alpine lakes (>2,500 m a.s.l.) exist in eastern and central China. Sediments were recovered from Foye Chi (33 degrees 57'N, 107 degrees 44'E; 3,410 m a.s.l.), a small lake on the southern slope of the mountain, and measured for magnetic properties. Chronological control was achieved with AMS C-14 dating. Combined with analyses of particle-size, TOC, C/N, delta C-13(org) and pollen in these sediments, and magnetic properties of catchment soils, the mineral-magnetic data reveal late Holocene palaeoenvironmental changes on the high-altitude southern slope of Taibai Mountain. Climate gradually ameliorated about 2,300 cal yr BP and warm and wet conditions occurred afterwards, culminating from 1,700 to 1,510 cal yr BP. The climate began to deteriorate at 1,510 cal yr BP, but was still warmer and wetter than present until similar to 663 cal yr BP. Cool, arid conditions peaked and were cooler and drier than the present at 663-290 cal yr BP, coincident with the Little Ice Age. Climate became warmer and more humid again after 290 cal yr BP. Data from these less anthropologically-disturbed alpine-lake sediments provide a record of late Holocene palaeoenvironmental change that supplements information from historical documents and literature for eastern and central China.