金沙江干热河谷华弹段黄土状土的成因、年龄及其古气候指示意义

青藏高原东南缘干热河谷中广泛发育黄土或黄土状土,是解读中国西南季风、干热河谷环境演变与高原隆升关系的良好载体,但目前尚无关于其成因、形成时代和古气候意义的系统研究。通过对金沙江干热河谷华弹段中黄土状土的空间分布、粒度特征、化学风化指数以及沉积速率的分析,发现该区黄土状土拔河越高,粒径越小,沉积速率越低;结合前人物源示踪研究成果,证实黄土状土来源于金沙江谷底的河漫滩沉积和古堰塞湖沉积,局地山谷风环流为其提供搬运动力。磁性地层学分析显示黄土状土地层全为正极性,剖面中未出现B/M界线,结合光释光测年结果,确定金沙江干热河谷华弹段中的黄土状土形成于中更新世中期以来。通过与同河段的古堰塞湖沉积形成时代进行对比,发现黄土状土的形成时代稍晚于同河段古堰塞湖相沉积大量堆积的时代。金沙江河谷中黄土状土与古堰塞湖相沉积在时空上的紧密关联性表明,滑坡堰塞事件控制着金沙江干热河谷中黄土状土物源的丰富程度,是影响金沙江深切河谷中黄土状土形成与沉积过程的主要因素。黄土状土的粒度与化学风化指数结果表明358 ka BP以来,该段河谷中古环境气候发生过明显冷干-暖湿波动,并在冰期-间冰期尺度上响应全球气候变化。

Digestive enzyme activities in mudskipper Boleophthalmus pectinirostris and Chinese black sleeper Bostrichthys sinensis

The mudskipper Boleophthalmus pectinirostris and Chinese black sleeper Bostrichthys sinensis occupy the intertidal zone.However,both species have their own unique diet.The former is an herbivore and the latter is a carnivore.In order to reveal the relationship between digestive enzyme activities and diets in the two species,the activities of protease(P),non-specific bile salt-activated lipase(BAL) and α-amylase(A) were determined in the stomach and intestine of adult mudskipper B.pectinirostris and Chinese black sleeper B.sinensis.The results showed that the activities of protease,BAL and α-amylase in the intestine of B.pectinirostris were significantly(P<0.05) higher than those in the stomach.In B.sinensis,gastric protease activity was not different from the intestinal protease(P>0.05),while BAL and α-amylase activities of the intestine were significantly(P<0.05) higher than those of the stomach.The activity of gastric protease in B.sinensis was significantly(P<0.05) higher than that in B.pectinirostris,while the activities of intestinal protease were not different between the two fish species(P>0.05).BAL activities of the stomach and intestine in B.sinensis were significantly(P<0.05) higher than those in B.pectinirostris,while α-amylase activities of the stomach and intestine in B.pectinirostris were significantly(P<0.05) higher than those in B.sinensis.The ratios of P/BAL,A/P and A/BAL of the digestive tract in B.pectinirostris were 1.5,107.3 and 158.6,respectively;and those in B.sinensis were 0.2,1.6 and 0.2,respectively.It can be concluded that food digestion in the adult B.pectinirostris is mainly carried out in the intestine,whereas in the adult B.sinensis it is initiated in the stomach and finishes in the intestine.The activities of BAL and α-amylase in B.pectinirostris and B.sinensis are well correlated with their diets.However,a clear-cut correlation between protease activity and diets is not found in these two species.