Proposal to add anthrostratigraphic and technostratigraphic units to the stratigraphic code for classification of anthropogenic Holocene deposits

Abstract

Anthropogenic surficial deposits are formed from Holocene and older deposits that have been so modified by human activity that their original form is unrecognizable. Because their characteristics are fundamentally different from those of natural origin, the creation of special stratigraphic categories seems justified. Two new material categories are proposed for the stratigraphic classification of anthropogenic deposits. An anthrostratigraphic unit (ASU) is defined as a stratiform or irregularly shaped body of anthropogenic origin in the sedimentary record distinguished and delineated on the basis of lithologic characteristics and/or bounding disconformities. An anthropogenic origin is indicated if the deposit (1) lies beneath an anthropogenic landform, (2) contains artifacts, (3) shows evidence of artificial mixing or other human disturbance, and/or (4) was imported from offsite and is allochthonous. The basic ASU is the anthrostratum, defined as a mostly stratiform body of artificially mixed earth (rock, sediment, soil, etc.) and artifactual (brick, concrete, etc.) materials. An anthrostratum need only be mappable at a local scale, but anthrostrata of different origins or type may be grouped together as an anthroformation if regionally mappable. A technostratigraphic unit (TSU) is defined as a stratiform body of anthropogenic origin in the sedimentary record defined on the basis of artifacts (objects of anthropogenic origin). TSUs are based on the evolution of technology involved in the creation of artificially altered or manufactured objects. The basic TSU is the technozone defined on the basis of Commercial Ranges (time from beginning to end of commercial availability of certain artifacts). ASUs and TSUs are applicable to anthropogenic deposits assigned to either the Holocene or the Anthropocene.