基于孢粉数据的白垩纪中国东部地貌解读^*

Interpretation of the Cretaceous geomorphology in eastern China based on palynological data

摘要

晚中生代一系列的构造运动使中国东部的地形、地貌发生了巨大的改变,形成了“东高西低”的地貌格局。关于白垩纪中国东部是否存在高原或山脉仍存在争议,故对高原或山脉的演化过程、古高程以及其延伸范围等方面仍需进一步的研究。笔者收集了白垩纪中国各地的双气囊花粉和喜干植物花粉的孢粉数据,通过它们百分含量的变化来分析中国东部的古植被演替和古气候演变,为白垩纪中国东部地形地貌的解读提供证据。孢粉分析表明,白垩纪中国大致分为3个气候区: 东北地区为温暖湿润的亚热带—暖温带气候区; 北方地区为半干旱的热带—亚热带气候过渡区; 南方和西藏、新疆地区为炎热干旱的热带—亚热带气候区。在古气候分析的基础上,根据孢粉数据对白垩纪中国东部地貌进行解读,结果显示: 早白垩世早期中国东北地区存在1个高海拔地貌区; 早白垩世东部沿海地区可能存在1个较高海拔的山脉,范围大致在闽浙地区; 晚白垩世早期,中国东部海岸山脉范围达到最大; 晚白垩世最晚期至古新世最早期,中国东部山脉逐步垮塌。推测至古新世早期,中国东部山脉基本已经消失。

Abstract

A series of tectonic movements during the Late Mesozoic greatly changed the topography and landform in eastern China,forming a geomorphic pattern of “high in the east and low in the west”. There is still a controversial issue on the existence of plateaus or mountains in eastern China during the Cretaceous,and thus the evolutionary processes,paleoaltitude and the extensional range of plateaus or mountains need further studies. In this paper,we collected the palynological data of xerophyte and disaccate pollen from vorious localities of China during the Cretaceous,and further discussed the paleovegetation succession and palaeoclimate evolution,which provides paleontological evidence for the interpretation of the geomorphology in eastern China at that time. The result shows that there were three climate zones in China during the Cretaceous: (i)the northeastern region was a warm and humid subtropical-warm climate zone;(ii)the northern region was a semi-arid tropical-subtropical transitional climate zone;(iii)the Tibet,Xinjiang and southern China were a hot and tropical-subtropical climate zone. The interpretation of the geomorphology shows that there was a high-altitude landform in northeast China during the early Early Cretaceous. Additionally,it is likely that coastal mountains existed in the Fujian and Zhejiang regions during the Early Cretaceous. In early Late Cretaceous,the range of coastal mountains in eastern China reached its maximum. From the late Late Cretaceous to Early Paleocene,the mountains in eastern China gradually collapsed,and by the Early Paleocene,the mountains were probably disappeared.

关键词

白垩纪 / 中国东部 / 孢粉数据 / 古气候 / 古地貌

Key words

Cretaceous / eastern China / palynological data / palaeoclimate / geomorphology

基金资助

*中国地质调查项目(编号: DD20221646)和国家自然科学基金项目(编号: 42072027)联合资助