 In terms of ammonite biostratigraphy, this bed belongs to the "Subcolumbites" zone.High-resolution date estimates have been produced for the Olenekian-aged strata exposed in the Majiashan Quarry based on isotopic records of carbon-13 cycling and spectral gamma ray logs (which measure the amount of radiation in rocks of astronomical origin); Bed 633 in particular was estimated at 248.41 Ma in age.During the Middle Triassic, the Chaohu strata were deposited in an oceanic basin relatively far from the coast, which was bordered on the south by shallower waters and carbonate platforms, and on the north by a continental slope and deeper basins.