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河北张家口地区,宣化、阳原、蔚县一带,分布有一套属山前凹陷或山间断陷盆地沉积的,含可采煤层,称为下花园组。其时代一直被认为早侏罗世或早—中侏罗世,而与京西门头沟组相对比。1986—1989年间笔者等在阳原东城煤矿该套地层中,首次发现了丰富的介形类化石。这是华北地区迄今发现的,侏罗系非海相介形类的最低层位。这一发现, 必将为该套地层的进一步划分、对比和时代的确定,提供新的,重要的化石依据。
Hebei Zhangjiakou area, Xuanhua, Yangyuan, Yuxian area, distributed in a set of piedmont depression or mountain fault basin sedimentary, with coal seam, known as the next garden group. Its era has been considered early Jurassic or early - Middle Jurassic, and compared with the Beijing Mentougou group. During 1986-1989, the author found abundant fossils of ostracods in this set of strata of Dongcheng Mine in Yangyuan. This is the lowest level of Jurassic non-marine ostracods so far discovered in North China. This discovery will surely provide a new and important fossil basis for the further division, comparison and time determination of this set of strata.