江苏建湖地区全新世生物群和古环境

本文据古生物学和古生态学资料,论述了建湖地区全新世生物群的演替、海平面波动、古地理变迁和古气候变化。生物群资料证实,本区曾遭受两次海侵,全新世中期海侵规模大,为高海面期,属低能潮坪至潮下带上部浅水环境;其晚期海侵规模小,属潮上带环境。两次海侵期之间,出现一明显海退期。据孢粉资料计算,本区气候波动与全新世全球性气候变化规律一致。

HOLOCENE BIOTA AND PALAEOENVIRONMENT IN JIANHU, JIANGSU

The purpose of this paper is to study the Holocene biotic variance and to discuss the sea level fluctuation and the palaeoclimatic change in Jianhu area, northern Jiangsu. The fossil materials for the study were collected by the authors in January of 1990 from this area. Especially a, comparatively detailed survey was made in the Qingfeng section of Jianhu and eight kinds of fossils including sporo-pollen, charophytes, foraminiferas, ostracods, gastropods, bivalves, microinsects and acarids were found and identified. 8 palynological zones are estabilished and 3 foraminiferal assemblages, 4 ostracod assemblages and 3 bivalve assemblages were recognized in the section. Gastropods, micro-insects and acarids are restricted to several layers in the section and charophytes are only distributed 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 6 900 a B. P. and the highest sea level appeared in the time from 6 400 to 5 400 a B. P. in this area. After 5 400 a B. P. the sea level was ,gradually declined and at about 4 500 a B. P. the sea water rapidly retreated from this area. From 2 200 to 1 000 a B. P. happened another transgression, which was much smaller in intensity than the preceding one. The Holocene palaeoenvironment can be reconstructed in Qingfeng region as follows, marsh (10 000—9 200 aB. P.)—coastal salted mud flat (9 200—— 6 900 a B. P.)—tidal flat (6 900—6 400 a B.P.)—nearshore shallow water (6 400—4 500 a B. P.)—nearshore lowland (4 500—2 200 a B. P.)—freshened lagoon (2 200—1 000 a B. P.). According to the palynological data, in Jianhu area the Hypsithermal is dated at 8 500—3 700 a B. P. and the climatic changes corresponded well to the Holocene global climatic changes.