Yushanjian Fm

Its basal part is in a conformable contact with the underlying Majian Fm

In some areas the formation overlies directly still older strata. Regionally, the schematic strat column indicates the next younger unit as Laocun Fm [? – Cretaceous Lexicon entry for the Laocun Fm has its span as only early Hauterivian => a major discontinuity between it and the underlying Yushanjian Fm of mid-Jurassic.]

It is distributed mainly in the area extending from Yushanjian Peak of the Baishe Township of Lanxi County through the Tongshan region of Zhuji City to Shaoxing City, as well as in the areas of Lijia Village, Fengshugang Hills, Meicheng Township of Jiande City, Changmingqiao Bridge of Yuhang County and Wentang Village of Changxing County. There are great differences in the lithology and facies of the formation between various regions of its occurrence. As in the Tongshan area of Zhuji City the basal part of the formation is composed of conglomerates with a thickness of 170 m, gradating upwards into calcareous sandstones and siltstones, intercalated occasionally with pebble-bearing sandstones, siltstones, mudstones, carbonaceous shales and coal beds, yielding bivalve fossils as represented by the Ferganoconcha-Sibireconcha-Pseudocardinia assemblage and the mixed Psilunio-Lamprotula (Eol.)-Cuneopsis assemblage, with a thickness of 1914 m. In the Lijia Village the formation is composed of an alternating layer of a set of purple sandy conglomerates in association with mudstones, with its middle and upper parts being intercalated with carbonaceous shales and thin coal beds, and with a thickness of about 858 m; while in the area of Wentang Village of Changxing County the formation is composed of purple and violet-grey sandy shales, intercalated with grey-white quartz-sandstones, yielding bivalve and Gastropod fossils, with a thickness of about 343 m.