摘要
该文通过对苏北—南黄海盆地高邮凹陷和海安凹陷16口石油探井中戴南组及上覆三垛组690块岩心样品的孢粉分析研究,建立了始新世三个孢粉植物组合,它们分别是早始新世Ulmipol-lenites-Inaperturopollenites-Pterisisporites组合(称第一孢粉组合,分布于戴南组一段至二段的Ⅰ亚段)、早始新世Taxodiaceaepollenites-Caryapollenites组合(称第二孢粉组合,分布于三垛组一段Ⅰ亚段)和中始新世晚期Nitrariadites-Retitricolpites-Euphorbiactes组合(称第三孢粉组合,分布于三垛组二段Ⅱ亚段)。讨论了这三个组合的特征和所属时代,提出了与以往戴南组、三垛组众多研究者将其归于渐新世的不同意见。文章还简要地阐述了各孢粉植物群的生态环境。对新发现的13个种作了描述,其中8新种,2未定种,对2种作了重新组合。
The geolgical age of the Dainan and Sanduo Formations widely developed in the subsurface ofnorthern Jiangsu and in the South Yellow Sea Basin has been in dispute since the 1950's. In the past,most geologists and micropaleontologists regarded it as Oligocene. However,after sampling and makinganalysis of the cored samples from the Dainan and Sanduo Formations,the writers now consider thatthe palynological assemblages under study from both formations may be compared with the Eocene pa-lynofloras from the strata yielding planktonic mierofossils or mammals. At present,three palynological assemblages have been distinguished from both formations; theirmain elements and occurrences are shown in Table 1 (see Chinese text). These assemblages may be briefly described as follows: A. The Ulmipollenites-Inaperturopollenites-Pterisisporites Assemblage This assemblage obtained from the Dainan Formation is characterized by the presence of rich triporate-type pollen andconiferous pollen grains, with the common occurrences of some extinct species,such as Parcisporites,Anizonosaccites, Bhardwa japollenites, Punctamonoaperturites, Navisulcites, Pentapollenites and Paraalnipollen-ites; Aquilapollenites and Proteacidites, which appeared frequently in Late Cretaceous and the Palaeocene,became rather rare. The assemblage is early Eocene in age and suggests a subtropical climate. B. The Taxodiaceaepollenites-Caryapollenites Assemblage This assemblage found from theLower bed of the Sanduo Formation is characterized by the occurrence of a great number of Caryapol-lenites triangulus, with some extinct components assigned to Parsisporites, Bhardwajapollenites, Puncta-monoaperturites, Paraalnipollenites and Pentapollenites. This assemblage indicates an early Eocene age anda subtropical climate. C. The Nitrariadites-Retitricolpites-Euphorbiacites Assemblage The assemblage form theupper part of member Ⅱ of the Sanduo Formation is very different from the underlying two assem-blages in the abundance of tricolpate and tricolporate pollen. Saccate coniferous pollen rarely occurs,whereas Ephedripites increases in number. This palynoflora is late Middle Eocene to/or early LateEocene in age and indicates a subtropical dry climate. Based on the present palynofloral data and sedimentary facies of Southeast China, the followingthree climatic events may be proposed during the Paleocene--Eocene in this area. 1. Oceurrence of Late Paleocene--Early Eocene optimum: During this time interval SoutheastChina was under the influence of comparative warm and humid climate, with wide distribution offlourishing vegetation and further development of dark sediments in major depressions, indicating animportant period for generation of oil and coal. The palynoflora is dominated by the triporate pollen ofUlmaceae ,Betulaceae,Juglandaceae,associated with some Fagaceae. The palynoflora seems to be simi-lar in aspect to that of Sabinan, Wilcox group of North America. 2. Invasion of dry-hot climate during middle Eocene:At the beginning of Middle Eocene ,dry-hotclimate invaded this area ,causing the development of poor vegetation and red-beds in Southeast China.But on the southern and northern borders of this area,luxuriant vegetation and dark sediment deposi-tion continued, owing to the weak influence of the dry climate. The palynoflora is marked by domi-nance of pollen of Fagaceae,which may be compared with that of the Claiborne Formation in NorthAmerica. 3. Strong invasion of dry-hot climate during late Middle Eocene to/or early Late Eocene: In thisperoid the arid area extended eastwards to as far as the shelf of East China Sea and Yellow Sea; the dryclimate covered a vast latitudinal area of China, with the development of red sediments intercalatedwith gypsum beds and arid palynofloras in the Chinese mainland and shelf. In the palynological assem-blage xerophytic pollen such as Ephedripites and Nitraridites often occur. Therefore,this event may beconsidered as a peroid under the driest climate since the Tertiary in SE China.
出处
《微体古生物学报》
CSCD
北大核心
1992年第1期1-24,111-116,共24页
Acta Micropalaeontologica Sinica
关键词
戴南组
三垛组
始新世
孢粉植物群
palynoflora
Eocene
Dainan Formation
Sanduo Formation
northern Jiangsu
