出露于扬子北缘大洪山地区的打鼓石群是扬子地区保留比较完整的中元古代地层,其上被青白口系花山群不整合覆盖.通常认为其与神农架群时代相当,但缺乏物源及同位素地质年代学证据.首次报导了打鼓石群底部太阳寺组砂岩的碎屑锆石U-Pb年龄.测年结果显示,该砂岩中碎屑锆石最古老的年龄为3.1~3.2Ga,最年轻年龄为1124Ma,并在2.65Ga和2.75Ga出现统计峰值,且年龄组成与崆岭杂岩区和杨坡杂岩区的多期岩浆活动具有较好的可比性.而鄂西地区神农架群沉积于1.1~1.4Ga,主要统计峰值年龄为1.6Ga、2~2.1Ga、2.7~2.8Ga.因此,打鼓石群沉积时间晚于神农架群,两者非同物异名.%The Dagushi Group, spread on the northern margin of the Yangtze Craton, is a well-preserved succession of the Mesopro?terozoic strata in South China, unconformably overlain by the Huashan Group. It is generally considered to have the same age as the Shennongjia Group. However, the isotopic geochronological evidence of material source is relatively insufficient. Detrital zircon U-Pb dating results of sandstone from Taiyangsi Formation on the bottom of Dagushi Group are first reported in this paper. The dating re?sults demonstrate that the oldest and youngest ages are 3.1~3.2Ga and 1124Ma,respectively. There are two age peaks of 2.65Ga and 2.75Ga in the detrital zircon. Its detrital zircon ages are consistent with the multi-period magmatic activities in Kongling Complex and Yangpo Complex before Neoproterozoic. Nevertheless, the Shennongjia Group, widely distributed in western Hubei Province, was deposited from 1.4Ga to 1.1Ga with three age peaks of 1.6Ga, 2~2.1Ga and 2.7~2.8Ga. These data indicate that the Dagushi Group was deposited obviously later than the Shennongjia Group, and hence they do not belong to the same stratigraphic sequence.
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