The geological cycle of plastics and their use as a stratigraphic indicator of the Anthropocene

Abstract

The rise of plastics since the mid-20 th century, both as a material element of modern life and as a growing environmental pollutant, has been widely described. Its distribution in both the terrestrial and marine realms suggests that it could be a key geological indicator of the Anthropocene, with potential to be a component of future geological strata. Most immediately evident in terrestrial deposits, it is clearly becoming a widespread component of marine sedimentary deposits in both shallow-and deep-water settings. It is abundant and widespread as macroscopic fragments and virtually ubiquitous as microplastic particles; these are dispersed by both physical and biological processes, not least via the food chain and the 'faecal express' route from surface to sea floor. Already a widespread and distinctive lithological component of strata, the amount of plastics seems likely to grow several-fold over the next few decades, and to continue to be input into the sedimentary cycle over coming millennia as temporary stores -landfill sites -are eroded. Plastics already enable fine time resolution within Anthropocene deposits via the development of its different types and via the artefacts ('technofossils') it is moulded into, and many of these may have long-term preservation potential if buried in strata.

Seagrass sedimentary deposits as security vaults and time capsules of the human past

“…Synthetic chemicals, for which the industrial nature is carefully documented, are also deposited in coastal sediments and may be used to reconstruct recent human history. It was recently suggested that the use of plastics may leave a horizon that could serve as a stratigraphic indicator of the anthropocene (Zalasiewicz et al 2016) and, in fact, accumulations of microplastic were recently documented in sediments adjacent to P. oceanica meadows in the NW Mediterranean (Alomar et al 2016).…”

Sources and sinks of microplastics in Canadian Lake Ontario nearshore, tributary and beach sediments

“…Plausible mechanisms for the deposition of low-density polymers in submerged sedimentary environments include net density increase of microplastic particles by biofouling (e.g. Ye and Andrady, 1991;Andrady, 2011;Zettler et al, 2013;McCormick et al, 2014), adsorption of natural substances to the surface (Frias et al, 2016), inclusion of inorganic fillers during manufacturing and faecal express (Cole et al, 2013;Setälä et al, 2014;Zalasiewicz et al, 2015). Inorganic fillers were not identified in any of the Raman spectra of the particles identified as PE and PP in this study, however, many microplastics in our study, particularly those with irregularly shaped, textured or degraded surfaces, appeared to have claylike particles adhered to their surfaces.…”

A Review of the Welfare Impact on Pinnipeds of Plastic Marine Debris

“…Tracing of barcodes on plastic debris has shown that marine plastic debris can originate in one country and be found 10 years later 10,000 km away (Barnes et al, 2009). Zalasiewicz et al (2016) note that degraded plastic is so widely spread now in ocean sediments that plastics will become one of the key geological indicator of the Anthropocene (current time, time of mankind), a distinctive stratal layer.…”