formal biostratigraphic unit正式: formal; official; regular生物: living things; living beings ...地层: stratum; layer; serati; geos ...单位: unit非正式生物地层单位: informal biostratigraphic unit下载手机词典可随时随地查词查翻译关注微信公众号：chachacidian，回复:正式生物地层单位，即可在微信中查询翻译
