华北晚侏罗世—早白垩世风成砂沉积及其古地理和古生态学意义*

华北晚侏罗世—早白垩世风成砂主要分布于鲁西蒙阴盆地上侏罗统三台组、辽西金—羊盆地上侏罗统—下白垩统土城子组、冀西北尚义盆地上侏罗统—下白垩统土城子组/后城组（原阎家窑组）、鄂尔多斯盆地下白垩统志丹群和甘肃下白垩统河口群。各地风成砂岩均具高角度大型—巨型板状、楔状交错层理及平行层理，分选较好—好，磨圆次棱角状—次圆状等沉积特征。对华北晚侏罗世—早白垩世风成砂赋存层位以及风成砂岩形成时代进行了对比，将风成砂主要划分为3个时期，即基末利期—贝利阿斯期、凡兰吟期—欧特里夫期和欧特里夫期—阿普特期，且从鲁西到甘肃风成砂岩形成时代逐渐变新。通过上述5个地区风成砂的古风向研究发现，当时西北风盛行，古地磁研究显示风成砂岩发育于N25°—N45°之间区域。根据当前全球风带分布特征，认为华北晚侏罗世—早白垩世处于西风带上，为行星风系所控制。通过对比南半球同期风成砂岩古风向研究，提出全球南北半球中纬度地区均处于西风带上。结合风成砂及相应层位沉积特征、沉积环境的研究，初步推测晚侏罗世—早白垩世，华北N30°以北地区为干旱寒冷气候，而N30°以南地区则干旱炎热，华北北部整体处于海拔较高的山地环境，山间盆地发育，火山活动频发。燕辽生物群与热河生物群的演替过程与风成砂沉积相耦合，体现了古地理、古环境对生物群发展的制约作用。

Sedimentology,palaeogeography and palaeoecology of the Late Jurassic-Early Cretaceous eolian sands in North China

The Late Jurassic-Early Cretaceous eolian sand deposits in North China were mainly developed in the Upper Jurassic Santai Formation of Mengyin Basin in western Shandong Province，Upper Jurassic-Lower Cretaceous Tuchengzi Formation of Jin-Yang Basin in western Liaoning Province，Upper Jurassic-Lower Cretaceous Tuchengzi/Houcheng Formation of Shangyi Basin in northwestern Hebei Province，Lower Cretaceous Zhidan Group in Erdos Basin and Lower Cretaceous Hekou Group in Gansu Province.These eolian sandstones in different areas were all characterized by high dipping large-giant tabular or wedge-shaped cross-beddings and parallel beddings，well sorting and subangular-subround shape.The formation age of the eolian sandstones in the above 5 areas can be divided into three phases，that is，Kimmeridgian-Berrisian，Valanginian-Hauterivian and Hauterivian-Aptian, and shows an younger ages westward from western Shandong Province to Gansu Province.The further researches of palaeowind direction and palaeomagnetism on eolian sandstones found that the northwestward wind was prevailed during the Late Jurassic-Early Cretaceous，while the eolian sandstones were distributed in the area of N25°-N45° which belonged to the westerlies.Compared with the eolian sandstones distribution at the same period in the southern hemisphere，the authors pointed out that mid latitude zones in both hemispheres lied in westerlies which was controlled by planetary wind system.During the Late Jurassic-Early Cretaceous，it was dry and cold in the area above N30° of North China， and dry and hot in the rest region of North China.It lied in a high altitude mountainous environment with some intermountane basins and frequent volcanic eruptions in northern North China.Succession of Yanliao Biota and Jehol Biota was coupling with the eolian sand deposition, which indicates that the palaeogeography and palaeoenvironment might have an effect on the evolution of the biota.