It was deposited in terrestrial deltaic to paralic conditions during the Cenomanian to Turonian ages of the Late Cretaceous.

During this time period the Chatham Islands were attached to Antarctica within the Antarctic Circle, at approximately 70° to 80° south.

The lithology consists of a basal conglomerate, which grades into sandstone and carbonaceous siltstone in the upper part of the formation.

[5] Compression fossils of insects have been found including members of Carabidae and Buprestidae,[6] and acritarch Introvertocystis.

[7] Amber is also known from the deposit[8] associated with the conifer Protodammara reimatamoriori, a member of Cupressaceae.