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The purpose of this book is to present the results of
our studies on the alteration of the Holocene biota in time and space
and the sedimentary and geochemical indicators in Jianhu and the adjacent
areas, northern Jiangsu, and to discuss the palaeoenvironmental changes,
essentially to study future environmental changes in these regions. The
authors carried out field investigations in the study area and collected
fossil specimens and sediment samples at the Qingfeng section of Jianhu,
Jianhu brick-field and Sanchakou brick-field of Jianhu, the Liujun section
of Huai' an and the Xiyuan section of Funing. Systematic sampling was
madde in the Qingfeng section, where eight kinds of fossils including
sporo-pollen, charophytes, foraminifers, ostracods, gastropods, bivalves,
microinsects and acarids were forund and identified. The 8 palynological
zones were estabilished and 3 foraminiferal assemblages, 4 ostracod assemblages
and 3 bivalve communities were recobgnized in the section. Gastropods,
micro-insects and acarids are restricted to several layers in the section
and charophytes are only distribted in its top part. The palaeoecology
of these faunas is discussed. The biotic alternation is clearly showed
in the Qingfeng section. On the basis of the biotic variance, it is suggested
that the Holocene transgression started at about 6900a BP and the highest
sea level appeared in the time from 6400a BP to 5400a BP in the study
area. After 5400a BP the sea level was gradually declined and the sea
water rapidly retreated from this area at about 4500a BP. From 2200a BP
to 1000a BP happened another transgression, which was much smaller in
intensity than the preceding one. The Holocene palaeoenvironment can be
reconstructed in Qingfeng region as follows: coastal muddy marsh - coastal
salted mud flat - inner bay - neritic bay - salted nearshore lowland-freshened
lagoon. According to the palynological data, the Hypsithermal interval
is deted at 8500-3700a BP in Jianhu and the climatic corresponded well
to the Holocene global climatic changes. |
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