准噶尔盆地南缘紫泥泉子组的时空展布及成因解释

准噶尔盆地南缘的紫泥泉子组生物化石贫乏 ,以往在该组所见的少量古近纪介形类、轮藻化石也多集中在上部 ,因此《西北地区区域地层表新疆维吾尔自治区分册》和《新疆维吾尔自治区岩石地层》根据层位关系将紫泥泉子组置于古新统—上始新统下部。根据在准噶尔盆地南缘露头和钻井剖面的紫泥泉子组中新采获的介形类、轮藻化石 ,紫泥泉子组的时代应为晚白垩世—中始新世。紫泥泉子组在空间分布上存在较大差异 ,露头区地层缺失多 ,覆盖区沉积较全 ,这主要是由于气候变化导致的湖平面和河流平衡剖面升降变化控制了准噶尔盆地南缘紫泥泉子组的地层发育

THE TEMPORAL AND SPATIAL DISTRIBUTION OF THE ZINIQUANZI FORMATION ON THE SOUTHERN MARGIN OF THE JUNGGAR BASIN AND THE EXPLANATION OF CONTRIBUTING FACTORS

The Ziniquanzi Formation is distributed on the southern margin of the Junggar Basin with rare fossil remains. In literatures, only few Palcogene ostracodes and charophytes were recorded from the upper part of this formation. Therefore, according to stratigraphyical succession, the Ziniquanzi Formation was assigned to the Paleocene to the lower part of the Upper Eocene (《The Regional Stratigraphic Scale of Xinjiang Uygur Autonomous Region, Northwest China》 and 《The Lithostratigraphy of Xinjiang Uygur Autonomous Region》). Since 1992, significant fossil ostracodes and charophytes have, however, been found by the authors from the Ziniquanzi Formation in both outcrops and well sections. Based on the known geological extension of these fossils in the world, the age of the Ziniquanzi Formation should be Late Cretaceous to Middle Eocene. Biostratigraphical study shows also that the Ziniquanzi Formation is poorly developed in the outcrop area, as compared with that of the covered area. Certain layers while developed in the covered area are missing in the cropped sections. It is held that the rising and dropping of lake level and river equilibrium profile resulting from the change of climate control the development of strata on the southern margin of the Basin.