蒙、甘、青地区侏罗纪孢粉组合序列及古气候

JURASSIC SPORA-POLLEN ASSEMBLAGES AND PALEOCLAMATE IN INNERMONGOLIA,GANSU,QINGHAI,CHINA

研究了蒙、甘、青地区侏罗纪孢粉组合特征,结合前人研究成果建立了该区侏罗纪7个孢粉组合,其中早侏罗世3个(P rotocon if erus-T aen iaesporites组合、O smund acid ites-Chasm atosporites-D isaccites组合和C lassopollis-Cyath id ites-Cycadop ites组合)、中侏罗世3个(Cyath id ites-Quad raecu lina-Cycadop ites组合、Cyath id ites-Ca llia lasporites-P inuspollen ites组合和C lassopollis-Cyath id ites-Inap erturop llen ites组合)和晚侏罗世1个(C lassopollis高含量组合)。综合利用孢粉植物群、孢粉亲缘植物古生态、沉积组合特征等,探讨了侏罗纪古气候格局及演化规律,指出早中侏罗世古气候总体温暖湿润,晚期发生一次干热化事件,中侏罗世晚期气候较炎热干旱,到晚侏罗世干热化程度进一步加剧,全区处于炎热干旱气候环境。

A larger part of Gansu, the west of Innermongolia and the northeast of Qinghai, divided into Alashan, Beiqilian-Hexizoulang,Zhongqilian and Qaidam stratigraphical divisions have been related. In this region there are widely well-developed Jurassic sediments, which include abundant coal and oil natural resources. Based on fully studing Jurassic spores and pollen grains in this area, with preceding achievement, seven spora-pollen assemblages have been established. The low Jurassic includes three assemblages： Protoconi ferus-Taeniaesporites , Osmundacidites-Chasmatosporites-Disaccites and Classopollis-Cyathidites- Cycadopites. The Middle Jurassic includes three assemblages： Cyathidites-Quadraeculina-Cycadopites, Cyathidites-CaUialasporites-Pinuspollenites and Classopollis-Cyathidites-InaperturopUenites. The Upper Jurassic only establishes Classopollis assemblage. Using paleoecology of mother plant of spores and pollen, combing the range of special rocks implying paleoclimate in strata, Jurassic climate has been studied, which includes Jurassic climate structure and evolution rule. It is suggested that the Jurassic climate locates the subtropical-moderate climate zone. Under this background,there is a fluctuated temperaturerising and humidity-falling events occur in late early Jurassic （Toarcian）. The late middle Jurassic climate is comparatively hot and arid. This hot and arid phenomenon is so further aggravate that the whole area is hot and arid in late Jurassic. The temperature is higher in Qaidam basin and Zhongqilian area than that of other place in the early-middle early Jurassic. The humidity in Yabulai basin is smaller than that of other place in the early middle Jurassic, but it is larger than that of other place in the late middle Jurassic in Qaidam basin. All of the research region are hot and arid in late Jurassic. The early-middle Jurassic is major period of assembling and generating coal and hydrocarbon with flourishing fauna and flora,coal bed and dark mudstone in Alashan, Zhongqilian and north of Qaidam basin. It is advantage for forming oil and gas-bearing depression, which is advantaged explorating area.