辽西北票中晚侏罗世髫髻山组木化石的古气候、古环境和古生态意义

木化石在陆地生态系统古气候、古环境和古生态研究方面具有重要的意义。辽西北票地区中晚侏罗世髫髻山组保存有数量丰富、类型多样且解剖构造保存完好的木化石。基于北票木化石树木年轮、树桩直径等数据计算了木材早材与晚材的比率(E/L),并推算了松柏类树木古树高。通过已有测量的树木年轮直径,应用Niklas(1994)和Mosbrugger(1994)两种方法恢复了化石森林中松柏类树木的古树高约为25m。推断中晚侏罗世的裸子植物森林树木生长的环境为以火山岩和湖相沉积为主,降水丰富。推断髫髻山组属于温暖、湿润、季节性明显的亚热带到暖温带气候,有利于植物的生长与发育。木化石木材组织中呈现的特殊解剖构造包括假轮、创伤树脂道、年轮扭曲、虫孔等,也能够揭示辽西北票中晚侏罗世植物生长过程中的古气候与古环境状况。表明辽西北票地区中晚侏罗世古气候虽然有利于植物生长,但生长期间受到了火山喷发、虫害、大风、降温等多种不利气候变化的影响与干扰。

Paleoclimate and Paleoenvironment Implications of the Middle Late Jurassic Tiaojishan Formation, Western Liaoning Province: Evidence from Fossil Wood Data

Petrified wood with well preserved growth rings and anatomical structure in Middle Late Jurassic Tiaojishan Formation, western Liaoning Province shows great significant in the study of paleoclimate, paleoenvironment and paleoecology. The main parameters were calculated. The E/L values of the growth rings of fossil wood material were calculated in this study based on field survey on stump materials as well as slide observations. Reconstructions of the height of fossil coniferous trees were made using the Niklas (1994) and Mosbrugger (1994) approaches; the average height of the coniferous trees in the Middle Jurassic was about 25m. It can be infered that the paleoenvironment of Jurassic gymnosperms tree forest was dominated with volcanic rocks and lacustrine sediments, with abundant precipitation. The genaral palaeoclimate was temperate to subtropical type during the Middle Late Jurasssic and was suitable for forest growth and development. Analyses of the special anatomical structures reveal particular implications of the palaeoclimate and palaeoenvironment of the wood material based on special structural evidences including false rings, traumatic resin canals, twisted growth rings, wormholes and so on. Although the palaeoclimate in the Middle Late Jurassic in Beipiao, Liaoning was favourable for tree growth, some fluctuation and severe disturb of climatic situations presented including low temperature, heavy wind, volcanic eruption, frost and other abnormal climate.