摘要:
较大的湖泊中的贝类生长线的氧同位素可能记录了季节性的温度变化。对拔氏丽蚌 (楔丽蚌 )Lamprotula(Cuneolamprotula)bazini (Heude)和环带丽蚌 (丽蚌 )Lamprotula (Lamprotula)zonata (Heude)的生长线进行氧同位素研究表明,前者有较强的适应环境变化的能力。δ18O值记录的襄汾地区晚更新世的古温度为 2 0~ 2 4℃至 30~34℃,古降雨量多出现代 2 0 0~ 2 6 7mm,河水排泄不畅,积水成湖。这些结果给人的启示是:全球变暖后,该地区气温可能有较大升幅 ;降雨量的增加有可能在排水不畅地区形成水灾,应注意防患于未然。
Abstract:
The paiaeociimatic and paiaeoenvironmentai information is studied by using the carbon and oxygen isotope profiies from the Late Pieistocene Lamprotula in Linfen and Xiangfe areas, where occur aboundant iameiiibranchs, especiaiiy fossii Lamprotula. The conciusions are as foiiows:1. The cessation of Lamprotula(Cuneolamprotula)bazini(Heude)sheii deposition in faii and summer is rich in16O, withδ 18O vaiue of - 14.5‰, whiie one in winter and spring is rich in18O, with δ 18O vaiue of - 12.2‰, and this fiuctuationof 2.2‰ may indicate a magnitute of change in seasonai temperature of water up to 10℃.2. The paiaeoenviroment of fossii Lamprotula was simiiar to ecoiogy of iiving Lamprotula in iower reaches of the Yangtze river, thus the most suitabie water for the Late Pieistocene Lamprotula was at temperature of 25 ~ 29℃ with a pH vaiue of 7 ~ 8. Therefore, the seasonai temperature of water changes from 20 ~ 24℃ to 30 ~ 34℃. 3. The sheii mean oxygen isotope vaiues of Lamprotula(Cuneolamprotula)bazini(Heude)and Lamprotula( Lamprotula) zonata(Heude)are - 12.9‰ and - 12.6 ‰, respectiveiy. This sheiiδ18O vaiues can be converted to waterδ18O vaiues by the iinear eguationδ 18Op( SM0W)= 1.07δ 18O s - 0.58, and, therefore, δ 18O vaiues of water where their iived is about - 14.4‰~ - 14.1‰. These vaiues are approximateiy 4‰ iighter than the meanδ 18O vaiue of the present rainfaii( - 10‰). It suggests that the annuai mean precipitation on Xiangfe Lake during the Late Pieistocene exceeded that of the pvesent by 200 ~ 267 mm.