Terminal Pleistocene/Holocene palaeoenvironmental changes revealed by mineral-magnetism measurements of lake sediments for Dali Nor area, southeastern Inner Mongolia Plateau, China

Mineral magnetic properties (SIRM, ARM, HIRM and S-ratios) are presented fo r two AMS C-14-dated pit-sequences of lake sediments recovered from Haoluku and Liuzhouwan (similar to 43 degreesN, 117 degreesE). The two sites fall in the semi-humid to semi-arid climate transition zone, Dali Nor area of th e southeast Inner Mongolia Plateau, China. Complemented by data for loss-on -ignition (LOI), total organic carbon (TOC), carbon/nitrogen (C/N), grain-s ize, and pollen, these mineral-magnetic measurements provide additional ins ights into environmental changes occurring at this area over the last 13 50 0 years. Conditions were extremely dry and windy as shown by the low SIRM, ARM and HIRM and high S-ratios before 13 500 yr BP. The environment began t o ameliorate gradually since then, and a further humidification occurred at similar to 10300 yr BP in Haoluku, the northern site, and at similar to 94 00 yr sp in Liuzhouwan, the southern one, as implied by the increased but o nly moderately high SIRM, ARM and HIRM and decreased S-ratios. As indicated by the remarkably increased SIRM, ARM, HIRM and S-ratios, a deterioration commenced at similar to 5600 yr sp in Haoluku and at similar to 4700 yr BP in Liuzhouwan. In Haoluku, conditions have been generally dry and windy sin ce similar to 5600 yr BP despite a minor amelioration at 4500-3000 yr BP. A short but marked amelioration occurred at 1200-700 yr up in Liuzhouwan. S- ratios seem to be a reliable indicator of environmental aridity for this ar ea. (C) 2001 Elsevier Science B.V. All rights reserved.