羌塘盆地查郎拉地区中新生代古气候演化初探

通过野外遥感调研和收集整理大量剖面及路线地质资料，讨论了羌塘盆地查郎拉地区气候常量元素、变价元素及微量元素特征；气候沉积物及其分布特征，结合已有的气候指示性古生物化石及岩相古地理资料，首次系统地演绎了本区中新生代古气候特征及其变迁演化史。划分出8个气候旋回，指出晚三叠世为热带亚热带温热半潮湿－潮湿气候，组成第I气候旋回；中株罗世呈热带亚热带半干旱→半潮湿气候的周期性变化，组成第Ⅱ、Ⅲ气候旋回；晚株罗纪经历了热带炎热半干燥→温暖半潮湿和潮湿→炎热半干燥气候的演化，组成第Ⅳ、Ⅴ气候旋回；白垩纪气候早期呈温暖半潮湿，晚期转为半干燥－干燥热带、亚热带气候，组成第既Ⅵ、Ⅶ气候旋回；第三纪为内陆亚热带的干燥、半干燥→高原温凉气候；第四纪曾出现过6次冰期和5次间冰期，新生代总体经历了剧烈而频繁的冷暖波动，气候日益干燥和寒冷。最后简单分析了气候旋回与沉积旋回、构造运动和青藏高原隆升的叠加耦合关系，以及古气候变迁的主因。

A Preliminary Study of the Mesozoic-Cenozoic Palaeoclimate Evolution in Chalangla Areas, Qiangtang Basin, Northern Tibet

This paper has discussed for the first time the distribution features of climatic sediments and the characteristics of climatic majorelements, valence changeable electron elements and minorelements in Chalangla area of Qiangtang basin, northern Tibet, and indicated climatic fossils there. The discussion is based on the field remote sensing survey, the study of a series of climatic sediments in many cross sections and route geological records and petrological and geochemical analysis of majorelements and minorelements. Combined with available information of palaeontology and lithofacies paleogeography, the authors have systematically deduced palaeoclimate characteristics and the Mesozoic Cenozoic transitional evolution in this region, which can be classified into 8 climatic cycles. Late Triassic was warm half humid to humid in the tropics and subtropics, comprising the first climatic cycle. Middle Jurassic showed cyclical variation of semiarid to half humid in the tropics and subtropics, forming the second and third climate cycle. Late Jurassic went through the climatic transition from sweltering half dry to warm half humid and humid to sweltering half dry in the tropics, constituting the fourth and fifth climate cycle. Cretaceous was characterized by warm half moisture in early stage and half aridness to aridness in the tropics and subtropics in late period, which made up the sixth and seventh climate cycle. Tertiary was mainly frigidly dry in the inland subtropics and semiarid to warm and cool in plateau. Quaternary experienced six times of glacial age and five times of interglacial period. Cenozoic totally underwent violent and frequent fluctuation from cold to warm and tended to be increasingly drier and colder. This paper has also analyzed the superposition-coupling relationship of the Mesozoic Cenozoic palaeoclimate evolution to sedimentary cycles and tectonic movement and probed into the main reasons of palaeoclimate variation.