Stratigraphic expressions of the Holocene-Anthropocene transition revealed in sediments from remote lakes
Earth Science Reviews
Short Title:
Earth Science Reviews
Format:
Journal Article
Publication Date:
2013/01/01/
Pages:
17 - 34
Sources ID:
80881
Collection:
Anthropocene and the Environmental Future
Visibility:
Public (group default)
Abstract:
(Show)
Stratigraphic boundaries are ideally defined by distinct lithological,geochemical, and palaeobiological signatures, to which a chronological
framework can be applied. We present a range of observations that
illustrate how the Holocene-Anthropocene transition meets these criteria
in its expression in sediments from remote arctic and alpine lakes,
removed from direct, catchment-scale, anthropogenic influences. In
glaciated lake basins, the retreat of glaciers commonly leads to
lithological successions from proglacial clastic sedimentation to
non-glacial organic deposition. Sediments from the majority of lakes
record marked depletions in the nitrogen stable isotopic composition of
sediment organic matter, reflecting anthropogenic influences on the
global nitrogen cycle. In all cases, siliceous microfossil assemblages
(diatoms and chrysophytes) change markedly and directionally, with
regional nuances. These stratigraphic fingerprints begin to appear in
the sediment record after AD 1850, but accelerate in pulses between AD
1950 and 1970 and again after AD 1980. Our review indicates that recent
environmental changes associated with humankind's dominance of key
global biogeochemical cycles are sufficiently pervasive to be imprinted
on the sediment record of remote lakes. Moreover, these changes are of
sufficient magnitude to conclude that the Holocene has effectively
ended, and that the concept of Anthropocene more aptly describes current
planetary dynamics. The synthesis of these observations pertains
directly to ongoing discussions concerning the eventual formalization of
a new stratigraphic boundary.