赣南—粤北中生代晚期存在上、中、下３个不同时代的火山岩系，其中下火山岩系称为余田群，可进一步划分为水头迳组和菖蒲组。水头迳组以沉积岩为主、夹火山碎屑岩，代表火山活动初始期的产物；菖蒲组为玄武岩、流纹岩和流纹质凝灰岩，有时夹砂岩，代表火山活动喷发期的产物。同位素年龄数据显示，余田群菖蒲组的地质时代为中侏罗世—晚侏罗世早期，水头迳组是否包含早侏罗世沉积有待进一步研究证实 There are three different age volcanic rocks in southern Jiangxi and northern Guangdong during the Mesozoic Era, of which the lower volcanic rocks are called Yutian formations, which can be further divided into two groups, Acorus cantonensis and Acorus calamus. Head group is mainly sedimentary rocks, volcano clastics, representing the initial period of volcanic products; calamity group for the basalt, rhyolite and rhyolitic tuff, sometimes sandstone, representing the eruption of volcanic activity of the product. Isotopic age data indicate that the geologic age of the Acorus calamus group is from Middle Jurassic to early Jurassic, and that whether the Early Mesozoic sediments contained Early Jurassic sediments remains to be confirmed by further studies