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富含热河生物群鸟类和恐龙化石的辽西白垩纪地层属于中生代陆相火山沉积,其不同区域之间的地层对比和时代归属一直存有较大争议。本文采用激光40Ar/39Ar年代学方法,对葫芦岛新台门地区一个实测剖面中蝾螈化石点下伏的两层火山岩夹层进行了年代学研究。通过地层中火山岩夹层及火山岩颈的年代学测定,获得6组激光40Ar/39Ar年代结果。其中,下部层位中的流纹岩和安山质玄武岩样品XTM-3、XTM-5年龄结果分别为94.2±1.3Ma、93.7±1.3Ma;作为这一期喷发晚期就位的火山岩颈样品XTM-7的年龄结果为92.8±0.4Ma;而上部层位的安山岩和安山玄武岩火山岩夹层样品XTM-6、XTM-8、XTM-9年龄分别为110.1±1.0Ma、110.9±0.5Ma、93.7±1.2Ma。随后我们又从XTM-9位置的化石点下部采集样品XTM-9-2,进行实验验证。得到的结果表明,新台门地区早白垩世地层记录了至少两期火山喷发事件,喷发时间分别为110Ma和93Ma。根据测年结果,新台门白垩系的蝾螈化石层应代表中国北方中生代地层中迄今所发现的有尾两栖类化石纪录的最高层位,可能与辽西地区的九佛堂组或甚至与阜新组相当。
The Cretaceous West Liaoning Province, which is rich in Jehol Biota birds and dinosaur fossils, belongs to the Mesozoic terrestrial volcanic sediments. Stratigraphic contrasts between the different regions and the ownership of the times have been the subject of much controversy. In this paper, the 40Ar / 39Ar chronology method is used to study the chronostratigraphy of two layers of volcanic intercalation under the salamander fossil point in a measured section of the Xintaimen area in Huludao. Through the geochronological measurement of volcanic intercalations and volcanic rocks in the strata, the results of the 40 Ar / 39 Ar dating of 6 groups of lasers are obtained. The XTM-3 and XTM-5 samples of rhyolite and andesitic basalts in the lower horizon are 94.2 ± 1.3Ma and 93.7 ± 1.3Ma, respectively. The volcanic neck sample XTM -7 was 92.8 ± 0.4Ma, while the XTM-6, XTM-8 and XTM-9 ages of upper andesite and andesite basalts were 110.1 ± 1.0Ma, 110.9 ± 0.5Ma and 93.7 ± 1.2Ma. Then we took the sample XTM-9-2 from the lower part of the XTM-9 fossil spot to verify the experiment. The results obtained show that at least two volcanic eruptions were recorded in the Early Cretaceous strata in the Xintaimen area with eruption times of 110 Ma and 93 Ma, respectively. According to the dating results, the Cretaceous salamander fossil layer in the Xintaimen area should represent the highest level of amphibian fossil records so far found in Mesozoic strata in northern China, possibly related to the Jiufotang Formation in Liaoxi area or even to Fuxin Formation quite.