阿尔冈纪

Algonkian \Al*gon"ki*an\, a.
1. Var. of {Algonquian}.
[Webster 1913 Suppl.]

2. (Geol.) Pertaining to or designating a period or era
recognized by the United States Geological Survey and some
other authorities, between the Arch[ae]an and the
Paleozoic, from both of which it is generally separated in
the record by unconformities. Algonkian rocks are both
sedimentary and igneous. Although fossils are rare, life
certainly existed in this period. -- n. The Algonkian
period or era, or system or group of systems.
[Webster 1913 Suppl.]