摘要
本文简述了热河动物群的地理及地质分布,各主要门类生物的发生与演化,论证了燕辽地区是热河动物群的发源地。热河动物群之所以在燕辽地区发生与发展,除生物自身的内因外,与当时的古气候吉地理、地壳运动、火山活动及古地磁极的频繁转换等因素密切相关。
The Jehol Fauna represented by Lycoptera-Eosestheria-Epherneropsis is a famous fauna of Late Jurassic-Early Cretaceous age in oriental Asia. It occurred and developed in certain structural and paleographical enviroments where crustal movements and volcanic activities were very active. So the study of its origin, evolution and cause is meaningful.
The Jehol Fauna is widely distributed in Eastern Trans-Baikal of USSR, Mongolia and northern China, and some of its members expanded to southeastern coastal areas and other parts of China. The present data show that the fauna first occurred in the northern Hebei-western Liaoning area and then expanded to other areas (Fig. 1). Why. did the Jehol Fauna originate from the Yanliao area? Generally speaking, causes, both internal (biologically related to heridity and variation) and external (paleoclimate, crustal movement, volcanism and geomagnetic reversals) had played their parts, but only the external causes are treated here.
Paleoclimate During the Late Jurassic-Early Cretaceous, as paleoclimates gradually became warmer and more humid in Eastern Trans-Baikal (USSR), Mongolia and northern China, there were many lakes and exuberant plants. Such an enviroment is advantageous to the development of the Jehol Fauna.
Crustal movement and volcanism During the Late Jurassic-Early Cretaceous, crustal movements and volcanic activities were rather active in the districts mentioned above, especially the northern Hebei-western Liaoning area. At the same time earthquakes possibly happened there. Volcanic eruption is considered a cause of mass extinction, but it might beneficially affect some aquatic life in that it supplied the animals with some needy chemical elements through solution in water, Benefited by such waters individuals of life had grown to large-sized ones, for example, the conchostracan species Pseudograpta, Keratestheria, Sentestheria and Jibeilimnadia and the insect species Ephemeropsis trisetalis are all very large.
Geomagnetic reversals It is quite possible that at the time of a geomagnetic reversal the shielding effect of the magnetic field would be largely removed and that the Earth's surface would be subjected to high incidence of cosmic and sun's radiations, thus inducing gene mutations, which led to new kinds of organisms. The Jehol Fauna originated and developed (from the Dabeigou to the Fuxin Formations or from the Oxfordian to the Barremian) might reflect an epoch of geomagnetic field alternations. In other words, geomagnetic field alternations might be closely related with the rise and fall of the Jehol Fauna.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1990年第4期350-360,共11页
Acta Geologica Sinica
