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通过研究四会地下古森林沉积剖面总有机碳及细根的碳同位素组成,揭示珠江三角洲地区在中晚全新世4.5~0.6kaBP期间的气候和地理环境变化特征.研究结果表明:在4.5~0.6kaBP期间,该地区的主要植被类型为C3植被.古森林在4kaBP左右于湿地环境中开始发育,在3kaBP左右与湿地同时消失,表明在3kaBP左右该地区的气候可能发生过急剧的变化.模拟结果显示:在3.5~3kaBP期间,该地区大气CO2浓度上升,气候有变暖的趋势;3~1.2kaBP期间的地层14C年代呈现大的跨度,这可能与新构造运动过程中地层抬升并遭到强烈剥蚀有关.在1.2~0.6kaBP期间,该地区为陆相沉积环境,植被的生物量日渐减少.古森林的消失可能与在3kaBP左右研究区域气候变干有关,热带辐合带的南移可能是导致气候变化的主要机制.
By studying the carbon isotope composition of total organic carbon and fine roots in the sediments of the four ancient underground forests, the climate and geography characteristics of the Pearl River Delta during the 4.5 ~ 0.6 kaBP of the middle and late Holocene were revealed. The results show that at 4.5 ~ 0.6 During the kaBP period, the main vegetation type in this area is C3 vegetation, which started to develop in the wetland around 4kaBP and disappeared at the same time as the wetland around 3kaBP, indicating that the climate may have drastically changed in the region around 3ka BP. The results show that during the period of 3.5-3 kaBP, the atmospheric CO2 concentration in this area increases, and the climate tends to warm. During the period of 3 ~ 1.2 kaBP, the formation has a large span in the 14C era, which may be uplifted and strongly affected by the neotectonic movement During the period of 1.2 ~ 0.6 kaBP, the area is continental depositional environment, and the biomass of vegetation is decreasing day by day. The disappearance of ancient forest may be related to the climate change in the study area around 3kaBP. The southward shift of the tropical convergence zone may be The main mechanism leading to climate change.