香港地区晚第四纪环境的几个问题

ON THE LATE QUATERNARY ENVIRONMENT IN HONG KONG AREA

香港的"潜在"植物区系及顶极植被与爪哇及印度相似。香港的红树林组成逊于海南但胜于闽南。海相层中有现今仅见于海南的陆均松和海桑．海相层中有红茄冬、角果木、榄李，而现今仅见榄李．中全新世香港有海滩岩发育．上述现象表明香港属于热带北部，历史上热带性比今更强。香港及邻近海域11个剖面揭示q以来有3个海相层，经历3次重大的海陆变迁．据验潮记录，近三四十年海平面上升率为1．64士0·25mm／a，若与澳门的验潮系列接口，1925～1996年海平面上升率为1.8mm／a。香港的"上升海滩"尚存疑，地震活动水平低，反映构造基本稳定，故1.6～1.8mm／a可视为珠江口绝对海平面上升率的平均值。

The potential flora, the vegetation type, and the famlies and species of mangrove, as well as the development of red weathering crust show that Hong Kong is situated at the northern part of monsoon tropical zone.Some typical tropical plants such as Dacrychum Nd Sonneratia of mangrove, which are now distributed only in Hainan Island, can be seen in the marine sediments QI with dating of 36 480- 16 420 a B P. and 36 230~ -30 560 a B. P., showing warmer and wetter climate during that Period in Hong Kong. In the Middle Holocene Stratum three SPecies of tropical mangrove, the Brubuiera Cerits and rhizophora observed, disPlaying Stronger tropical feature at that bime. At present, only Btrguiera of the three SPecies can be found in the mangrove. Modern beach rock is forming along the south coast of Hainan Island, but in Hong Kong beach rock is dated 2 820-1 700 a B P..From the analysis of Spore pollen, foraminfera, calcareous nannofossils and mineral, three marine strata interbedding with three continental deposits strata have been indentified in Hong Kong, indicating three times of transgression that occurred during Q31 Q23-2 and Q4 respectively. The elevations of ancient sea level were-35- 50m during Q13,- 25 ~ -30m during Q23-2,and -15^-20m during 8 000 a B P. Some shell layers dated 5 520 a B P. at an elevation of 0. 5~1.2m indicate that the sea level during 5 000 a B P. had been close tO that at present and then fluctuated with slight descent. According to the tidal data from 1950 to 1996 in Hong Kong, in which the data during 1953 ~1956 are not so reasonable and therefore they are rejected, a rate of sea level rise of 2. 0 mm/ a during 1959~ 1996 is calculated. In combination with the long series of tidal data of about 70 years (1925 ~ 1996) in Macao, a curve of sea level change in Hong Kong and Macao area can be established, and the rate of sea level rise during 1925~1996 is 1.8 mm/a.