关键词: 碎屑锆石U-Pb年龄；沉积指向性构造；陆源碎屑源区；杨柳岗组；浙江江山

Abstract:

In this study, the age spectra of detrital zircons and sedimentary directional structures are used to investigate the
paleogeographic features, especially the paleogeography in east Cathaysian Block. The dating results of detrital zircons from clastic
interlayers of the Yangliugang Formation in northern Jiangshan of Zhejiang Province, which lies on the southeastern margin of the
Yangtze Block, show that the ages range from 515 Ma to 3340 Ma, with a major peak at 828 Ma and secondary peaks at 727 Ma and
916 Ma in the detrital age spectrum. Moreover, the result of spectrum correlation suggests that northern Jiangshan might be affinity to
northwestern Fujian and eastern central Jiangxi in the Cathaysian Block as well as northeastern Jiangxi and southern Anhui in the
Yangtze Block, however, irrelative with southwestern Fujian and southern Jiangxi in the Cathaysian Block. On the other hand, the
features of sedimentary directional structures, which include syndepositional slump folds in the Yangliugang Formation and the
overlying Huayansi Formation and cross beddings in the underlying Dachenling Formation, indicate that the sedimentary basement
inclined toward the northwest and the sediment transport direction was from the southeast to the northwest during depositional periods
of these formations. And then, it can be deduced that the provenance of zircon-bearing clastics in the Yangliugang Formation might belocated in the nowadays central part of Zhejiang Province of eastern Cathaysian Block, in which there are outcrops of metamorphic
rocks with known age corresponding to 42% detrital zircons in this study. Toward the northwest, the detrital source might have supplied
clastics eroded from older strata or redeposited materials originated from older strata. These strata mainly include the Chencai Group
and the equivalent to Heshangzhen Group and Shuangxiwu Group, which contain intrusive and volcanic rocks.

Key words: detrital zircon U-Pb ages, sedimentary directional structures, detrital source, Yangliugang Formation (Cambrian);Northern Jiangshan of Zhejiang Province