The Environmental Significance Of Submerged Forest Remains On Qianhu Bay In Fujian Province And That Of The Micropalaeontology In Its Sediment

In this paper, we discuss the form age as well as palaeovegetation, palaeoclimate, palaeoenvironment of the submerged forest remains on Qianhu bay in Fujian Zhangpu, through investigating on the distributed characteristic, the species quantity, the composition,the community character, the form age of the submerged forest remains,the microfossil(spore-pollen, diatom,foraminifera) of sediment and quaternary geology and with mutually verities through multi-angles and multi-face.Analyzing spore-pollen which on the sediment of the QHP section and QHZ core 1, we gain that there are 4 changing processes which were about the sediment environment and the palaeoclimate since Late Pleistocene on Qianhu bay. The 4 changing processes are: the forepart of the Late Pleistocene was cold and dry; the metaphase of the Late Pleistocene was mild, hot and wet, two obvious transgression sea events happened in the period; the last stage of the Late Pleistocene transiting to Holocene the temperature was being turbulence; the climate since the Holocene was similar comparatively with that of modem times.Analyzing diatom which on the sediment of the QHP section and QHZ core 1, we gain the changing processes since Late Pleistocene from old to new are: river environment- bay environment- river environment- bay river estuary environment- river environment- continental limnetic environment- lacustrine sand blown by wind environment- bank water low small bay environment.Analyzing foraminifera which from the sediment of the QHP section,QHZ core 1 and four surficial sample,we found that the grain strata which the foraminifera in is on the top of the core (2.46-2.96m). On the base of the ecologe of the superiority species and the characters of the despecies, we conclued that the depositing environment of the foraminifera was beachy shallow enviroment. Uniting the relative of strata, we conclude that the sediment was the production of nowadays.Through investigate to the submerged forest remains, we discovered the scope which submerged forest remains distributes relatively and concentrated is approximately 300m parallel seacoast and 60～150m in vertical. The elevation of the palaeostump are from -1.514m to-2.967m,the height is mostly between 10～30cm.The base diameter of the stem of the stump are usually 30～120cm,and the biggest is 210cm.There are 89 palaeostumps which are bigger and more clear among them. The identification on the slice of some of less carbonized palaeostump is that there are 4 seed plants and some broadleaf which belong to the arbor of dicotyledon growing on lands. The 14C dating result of the submerged forest samples indicates that this submerged forest remains which grew between 42560±350～>43000aB.P. was the product of the last stage of the Late Pleistocene. It is the longest and well preserved submerged forest remains which had been reported in the world at present.The typical characteristics of the broad-leaved arbor of dicotyledon found by investigation, such as the ancient bine remains on or around the trunks ,the buttress on the base of the palaeostumps and so on, combined with the micro-structure identification of the specimen of the woods, shows that the primary vegetation of the forest remains belong to monsoon evergreen broad-leaved forest.The reseach results above show that: Qianhu bay in Zhangpu once was a forest reaching the sky, surrounded by ancient bines and exuberate of vegetation in the last stage of the Late Pleistocene,42560±350 aB.P.～>43000aB.P. The discovery of this submerged forest remains is a direct evidence to the Sea level change and earth's crust vibratory movement of this area and even the west bank of Taiwan channel.